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Lee SM, Le HT, Taizhanova A, Nong LK, Park JY, Lee EJ, Palsson BO, Kim D. Experimental promoter identification of a foodborne pathogen Salmonella enterica subsp. enterica serovar Typhimurium with near single base-pair resolution. Front Microbiol 2024; 14:1271121. [PMID: 38239730 PMCID: PMC10794520 DOI: 10.3389/fmicb.2023.1271121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Accepted: 12/01/2023] [Indexed: 01/22/2024] Open
Abstract
Salmonella enterica serovar Typhimurium (S. Typhimurium) is a common foodborne pathogen which is frequently used as the reference strain for Salmonella. Investigating the sigma factor network and protomers is crucial to understand the genomic and transcriptomic properties of the bacterium. Its promoters were identified using various methods such as dRNA-seq, ChIP-chip, or ChIP-Seq. However, validation using ChIP-exo, which exhibits higher-resolution performance compared to conventional ChIP, has not been conducted to date. In this study, using the representative strain S. Typhimurium LT2 (LT2), the ChIP-exo experiment was conducted to accurately determine the binding sites of catalytic RNA polymerase subunit RpoB and major sigma factors (RpoD, RpoN, RpoS, and RpoE) during exponential phase. Integrated with the results of RNA-Seq, promoters and sigmulons for the sigma factors and their association with RpoB have been discovered. Notably, the overlapping regions among binding sites of each alternative sigma factor were found. Furthermore, comparative analysis with Escherichia coli str. K-12 substr. MG1655 (MG1655) revealed conserved binding sites of RpoD and RpoN across different species. In the case of small RNAs (sRNAs), 50 sRNAs observed their expression during the exponential growth of LT2. Collectively, the integration of ChIP-exo and RNA-Seq enables genome-scale promoter mapping with high resolution and facilitates the characterization of binding events of alternative sigma factors, enabling a comprehensive understanding of the bacterial sigma factor network and condition-specific active promoters.
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Affiliation(s)
- Sang-Mok Lee
- School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, Republic of Korea
| | - Hoa Thi Le
- School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, Republic of Korea
| | - Assiya Taizhanova
- Department of Genetic Engineering and Graduate School of Biotechnology, College of Life Sciences, Kyung Hee University, Yongin, Republic of Korea
| | - Linh Khanh Nong
- School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, Republic of Korea
| | - Joon Young Park
- School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, Republic of Korea
| | - Eun-Jin Lee
- Department of Life Sciences, College of Life Sciences and Biotechnology, Korea University, Seoul, Republic of Korea
| | - Bernhard O. Palsson
- Department of Bioengineering, University of California San Diego, La Jolla, CA, United States
| | - Donghyuk Kim
- School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, Republic of Korea
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The Molecular Basis for Escherichia coli O157:H7 Phage FAHEc1 Endolysin Function and Protein Engineering to Increase Thermal Stability. Viruses 2021; 13:v13061101. [PMID: 34207694 PMCID: PMC8228626 DOI: 10.3390/v13061101] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 06/01/2021] [Accepted: 06/07/2021] [Indexed: 02/02/2023] Open
Abstract
Bacteriophage-encoded endolysins have been identified as antibacterial candidates. However, the development of endolysins as mainstream antibacterial agents first requires a comprehensive biochemical understanding. This study defines the atomic structure and enzymatic function of Escherichia coli O157:H7 phage FAHEc1 endolysin, LysF1. Bioinformatic analysis suggests this endolysin belongs to the T4 Lysozyme (T4L)-like family of proteins and contains a highly conserved catalytic triad. We then solved the structure of LysF1 with x-ray crystallography to 1.71 Å. LysF1 was confirmed to exist as a monomer in solution by sedimentation velocity experiments. The protein architecture of LysF1 is conserved between T4L and related endolysins. Comparative analysis with related endolysins shows that the spatial orientation of the catalytic triad is conserved, suggesting the catalytic mechanism of peptidoglycan degradation is the same as that of T4L. Differences in the sequence illustrate the role coevolution may have in the evolution of this fold. We also demonstrate that by mutating a single residue within the hydrophobic core, the thermal stability of LysF1 can be increased by 9.4 °C without compromising enzymatic activity. Overall, the characterization of LysF1 provides further insight into the T4L-like class of endolysins. Our study will help advance the development of related endolysins as antibacterial agents, as rational engineering will rely on understanding mutable positions within this protein fold.
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Lui LM, Nielsen TN, Arkin AP. A method for achieving complete microbial genomes and improving bins from metagenomics data. PLoS Comput Biol 2021; 17:e1008972. [PMID: 33961626 PMCID: PMC8172020 DOI: 10.1371/journal.pcbi.1008972] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 06/02/2021] [Accepted: 04/16/2021] [Indexed: 11/19/2022] Open
Abstract
Metagenomics facilitates the study of the genetic information from uncultured microbes and complex microbial communities. Assembling complete genomes from metagenomics data is difficult because most samples have high organismal complexity and strain diversity. Some studies have attempted to extract complete bacterial, archaeal, and viral genomes and often focus on species with circular genomes so they can help confirm completeness with circularity. However, less than 100 circularized bacterial and archaeal genomes have been assembled and published from metagenomics data despite the thousands of datasets that are available. Circularized genomes are important for (1) building a reference collection as scaffolds for future assemblies, (2) providing complete gene content of a genome, (3) confirming little or no contamination of a genome, (4) studying the genomic context and synteny of genes, and (5) linking protein coding genes to ribosomal RNA genes to aid metabolic inference in 16S rRNA gene sequencing studies. We developed a semi-automated method called Jorg to help circularize small bacterial, archaeal, and viral genomes using iterative assembly, binning, and read mapping. In addition, this method exposes potential misassemblies from k-mer based assemblies. We chose species of the Candidate Phyla Radiation (CPR) to focus our initial efforts because they have small genomes and are only known to have one ribosomal RNA operon. In addition to 34 circular CPR genomes, we present one circular Margulisbacteria genome, one circular Chloroflexi genome, and two circular megaphage genomes from 19 public and published datasets. We demonstrate findings that would likely be difficult without circularizing genomes, including that ribosomal genes are likely not operonic in the majority of CPR, and that some CPR harbor diverged forms of RNase P RNA. Code and a tutorial for this method is available at https://github.com/lmlui/Jorg and is available on the DOE Systems Biology KnowledgeBase as a beta app.
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Affiliation(s)
- Lauren M. Lui
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, CA, United States of America
| | - Torben N. Nielsen
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, CA, United States of America
| | - Adam P. Arkin
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, CA, United States of America
- Department of Bioengineering, University of California, Berkeley, California, United States of America
- Innovative Genomics Institute, Berkeley, CA, United States of America
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Tran T, Checkley S, Caffrey N, Mainali C, Gow S, Agunos A, Liljebjelke K. Genetic Characterization of AmpC and Extended-Spectrum Beta-Lactamase Phenotypes in Escherichia coli and Salmonella From Alberta Broiler Chickens. Front Cell Infect Microbiol 2021; 11:622195. [PMID: 33777835 PMCID: PMC7994595 DOI: 10.3389/fcimb.2021.622195] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 02/18/2021] [Indexed: 11/13/2022] Open
Abstract
Horizontal gene transfer is an important mechanism which facilitates bacterial populations in overcoming antimicrobial treatment. In this study, a total of 120 Escherichia coli and 62 Salmonella enterica subsp. enterica isolates were isolated from broiler chicken farms in Alberta. Fourteen serovars were identified among Salmonella isolates. Thirty one percent of E. coli isolates (37/120) were multiclass drug resistant (resistant to ≥ 3 drug classes), while only about 16% of Salmonella isolates (10/62) were multiclass drug resistant. Among those, eight E. coli isolates had an AmpC-type phenotype, and one Salmonella isolate had an extended-spectrum beta-lactamase (ESBL)-type beta-lactamase phenotype. We identified both AmpC-type (blaCMY-2) and ESBL-type (blaTEM) genes in both E. coli and Salmonella isolates. Plasmids from eight of nine E. coli and Salmonella isolates were transferred to recipient strain E. coli J53 through conjugation. Transferable plasmids in the eight E. coli and Salmonella isolates were also transferred into a lab-made sodium azide-resistant Salmonella recipient through conjugation. The class 1 integrase gene, int1, was detected on plasmids from two E. coli isolates. Further investigation of class 1 integron cassette regions revealed the presence of an aadA gene encoding streptomycin 3’’-adenylyltransferase, an aadA1a/aadA2 gene encoding aminoglycoside 3’’-O-adenyltransferase, and a putative adenylyltransferase gene. This study provides some insight into potential horizontal gene transfer events of antimicrobial resistance genes between E. coli and Salmonella in broiler chicken production.
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Affiliation(s)
- Tam Tran
- Department of Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
| | - Sylvia Checkley
- Department of Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
| | - Niamh Caffrey
- Department of Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
| | - Chunu Mainali
- Animal Policy and Epidemiology Section, Animal Health Branch, Animal Health and Assurance Division, Alberta Agriculture and Forestry, Edmonton, AB, Canada
| | - Sheryl Gow
- Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada
| | - Agnes Agunos
- Center for Foodborne, Environmental and Zoonotic Infectious Diseases, Public Health Agency of Canada, Guelph, ON, Canada
| | - Karen Liljebjelke
- Department of Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
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Heo M, Chenon G, Castrillon C, Bibette J, Bruhns P, Griffiths AD, Baudry J, Eyer K. Deep phenotypic characterization of immunization-induced antibacterial IgG repertoires in mice using a single-antibody bioassay. Commun Biol 2020; 3:614. [PMID: 33106526 PMCID: PMC7589517 DOI: 10.1038/s42003-020-01296-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Accepted: 09/15/2020] [Indexed: 12/12/2022] Open
Abstract
Antibodies with antibacterial activity need to bind to the bacterial surface with affinity, specificity, and sufficient density to induce efficient elimination. To characterize the anti-bacterial antibody repertoire, we developed an in-droplet bioassay with single-antibody resolution. The assay not only allowed us to identify whether the secreted antibodies recognized a bacterial surface antigen, but also to estimate the apparent dissociation constant (KD app) of the interaction and the density of the recognized epitope on the bacteria. Herein, we found substantial differences within the KD app/epitope density profiles in mice immunized with various species of heat-killed bacteria. The experiments further revealed a high cross-reactivity of the secreted IgG repertoires, binding to even unrelated bacteria with high affinity. This application confirmed the ability to quantify the anti-bacterial antibody repertoire and the utility of the developed bioassay to study the interplay between bacteria and the humoral response.
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Affiliation(s)
- Millie Heo
- 'Laboratoire Colloïdes et Matériaux Divisés' (LCMD), ESPCI Paris, PSL Research University, CNRS UMR8231 Chimie Biologie Innovation, F-75005, Paris, France
| | - Guilhem Chenon
- 'Laboratoire Colloïdes et Matériaux Divisés' (LCMD), ESPCI Paris, PSL Research University, CNRS UMR8231 Chimie Biologie Innovation, F-75005, Paris, France
| | - Carlos Castrillon
- Unit of Antibodies in Therapy and Pathology, Institute Pasteur, UMR1222 INSERM, F-75015, Paris, France
- 'Laboratoire de Biochimie' (LBC), ESPCI Paris, PSL Research University, CNRS UMR8231 Chimie Biologie Innovation, F-75005, Paris, France
| | - Jérôme Bibette
- 'Laboratoire Colloïdes et Matériaux Divisés' (LCMD), ESPCI Paris, PSL Research University, CNRS UMR8231 Chimie Biologie Innovation, F-75005, Paris, France
| | - Pierre Bruhns
- Unit of Antibodies in Therapy and Pathology, Institute Pasteur, UMR1222 INSERM, F-75015, Paris, France
| | - Andrew D Griffiths
- 'Laboratoire de Biochimie' (LBC), ESPCI Paris, PSL Research University, CNRS UMR8231 Chimie Biologie Innovation, F-75005, Paris, France
| | - Jean Baudry
- 'Laboratoire Colloïdes et Matériaux Divisés' (LCMD), ESPCI Paris, PSL Research University, CNRS UMR8231 Chimie Biologie Innovation, F-75005, Paris, France
| | - Klaus Eyer
- 'Laboratoire Colloïdes et Matériaux Divisés' (LCMD), ESPCI Paris, PSL Research University, CNRS UMR8231 Chimie Biologie Innovation, F-75005, Paris, France.
- Laboratory for Functional Immune Repertoire Analysis, Institute of Pharmaceutical Sciences, D-CHAB, ETH Zürich, Zürich, Switzerland.
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Lázaro CA, Monteiro MLG, Conte-Junior CA. Combined Effect of Modified Atmosphere Packaging and UV-C Radiation on Pathogens Reduction, Biogenic Amines, and Shelf Life of Refrigerated Tilapia ( Oreochromis niloticus) Fillets. Molecules 2020; 25:molecules25143222. [PMID: 32679681 PMCID: PMC7397001 DOI: 10.3390/molecules25143222] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 07/08/2020] [Accepted: 07/09/2020] [Indexed: 11/16/2022] Open
Abstract
This study investigated the isolated effect of modified atmosphere packaging (MAP; 50% CO2 and 50% N2) and ultraviolet radiation (UV; 0.30 J/cm2) as well as their combined (MAP/UV) effect on reduction of Salmonella typhimurium and Escherichia coli O157:H7, biogenic amines (BA), and on shelf life of tilapia fillets stored at 4 ± 1 °C for 10 days. UV samples had the highest reduction of S. typhimurium (1.13 log colony forming units/g; CFU/g) and E. coli O157:H7 (0.70 log CFU/g). MAP and MAP/UV reduced the growth of S. typhimurium in 0.50 log CFU/g and did not affect the growth of E. coli O157:H7. UV, MAP, and MAP/UV increased lag phase and/or generation time of all evaluated bacterial groups, decreased pH values, ammonia formation, texture changes, and, in general, the BA formation throughout storage period, and, therefore, UV, MAP, and MAP/UV extended the shelf life for two, three, and at least five days, respectively. MAP/UV, MAP, and UV decreased redness, MAP/UV and MAP increased yellowness and lipid oxidation, while UV did not affect it. MAP/UV demonstrated promising results for shelf life extension; however, different gas ratios in combination with other ultraviolet radiation type C (UV-C) doses should be investigated to reach the highest microbiological safety and maintenance of the overall quality of tilapia fillets.
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Affiliation(s)
- César A. Lázaro
- Departmento de Salud Animaly Salud Pública, Facultad de Medicina Veterinaria, Universidad Nacional Mayor de San Marcos (UNMSM), San Borja, Lima 15021, Peru;
| | - Maria Lúcia G. Monteiro
- Departmento de Bioquímica, Instituto de Química, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Rio de Janeiro 21941-909, Brazil;
- Núcleo de Análise de Alimentos (NAL-LADETEC), Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro 21941-598, Brazil
- Departamento de Tecnologia de Alimentos, Universidade Federal Fluminense (UFF), Niterói, Rio de Janeiro 24220-000, Brazil
- Correspondence: ; Tel.: +55-21-3938-7825
| | - Carlos A. Conte-Junior
- Departmento de Bioquímica, Instituto de Química, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Rio de Janeiro 21941-909, Brazil;
- Núcleo de Análise de Alimentos (NAL-LADETEC), Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro 21941-598, Brazil
- Departamento de Tecnologia de Alimentos, Universidade Federal Fluminense (UFF), Niterói, Rio de Janeiro 24220-000, Brazil
- Programa de Pós-graduação em Vigilância Sanitária, Instituto Nacional de Controle de Qualidade em Saúde, Fundação Oswaldo Cruz (FIOCRUZ), Rio de Janeiro 21040-900, Brazil
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7
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Apjok G, Boross G, Nyerges Á, Fekete G, Lázár V, Papp B, Pál C, Csörgő B. Limited Evolutionary Conservation of the Phenotypic Effects of Antibiotic Resistance Mutations. Mol Biol Evol 2019; 36:1601-1611. [PMID: 31058961 PMCID: PMC6657729 DOI: 10.1093/molbev/msz109] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Multidrug-resistant clinical isolates are common in certain pathogens, but rare in others. This pattern may be due to the fact that mutations shaping resistance have species-specific effects. To investigate this issue, we transferred a range of resistance-conferring mutations and a full resistance gene into Escherichia coli and closely related bacteria. We found that resistance mutations in one bacterial species frequently provide no resistance, in fact even yielding drug hypersensitivity in close relatives. In depth analysis of a key gene involved in aminoglycoside resistance (trkH) indicated that preexisting mutations in other genes-intergenic epistasis-underlie such extreme differences in mutational effects between species. Finally, reconstruction of adaptive landscapes under multiple antibiotic stresses revealed that mutations frequently provide multidrug resistance or elevated drug susceptibility (i.e., collateral sensitivity) only with certain combinations of other resistance mutations. We conclude that resistance and collateral sensitivity are contingent upon the genetic makeup of the bacterial population, and such contingency could shape the long-term fate of resistant bacteria. These results underlie the importance of species-specific treatment strategies.
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Affiliation(s)
- Gábor Apjok
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | - Gábor Boross
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
- Department of Biology, Stanford University, Stanford, CA
| | - Ákos Nyerges
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | - Gergely Fekete
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | - Viktória Lázár
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
- Technion – Israel Institute of Technology, Faculty of Biology, Haifa, Israel
| | - Balázs Papp
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | - Csaba Pál
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | - Bálint Csörgő
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA
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8
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Nevermann J, Silva A, Otero C, Oyarzún DP, Barrera B, Gil F, Calderón IL, Fuentes JA. Identification of Genes Involved in Biogenesis of Outer Membrane Vesicles (OMVs) in Salmonella enterica Serovar Typhi. Front Microbiol 2019; 10:104. [PMID: 30778340 PMCID: PMC6369716 DOI: 10.3389/fmicb.2019.00104] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 01/17/2019] [Indexed: 12/26/2022] Open
Abstract
Outer membrane vesicles (OMVs) are nano-sized proteoliposomes discharged from the cell envelope of Gram-negative bacteria. OMVs normally contain toxins, enzymes and other factors, and are used as vehicles in a process that has been considered a generalized, evolutionarily conserved delivery system among bacteria. Furthermore, OMVs can be used in biotechnological applications that require delivery of biomolecules, such as vaccines, remarking the importance of their study. Although it is known that Salmonella enterica serovar Typhi (S. Typhi), the etiological agent of typhoid fever in humans, delivers toxins (e.g., HlyE) via OMVs, there are no reports identifying genetic determinants of the OMV biogenesis in this serovar. In the present work, and with the aim to identify genes participating in OMV biogenesis in S. Typhi, we screened 15,000 random insertion mutants for increased HlyE secretion. We found 9 S. Typhi genes (generically called zzz genes) determining an increased HlyE secretion that were also involved in OMV biogenesis. The genes corresponded to ompA, nlpI, and tolR (envelope stability), rfaE and waaC (LPS synthesis), yipP (envC), mrcB (synthesis and remodeling of peptidoglycan), degS (stress sensor serine endopeptidase) and hns (global transcriptional regulator). We found that S. Typhi Δzzz mutants were prone to secrete periplasmic, functional proteins with a relatively good envelope integrity. In addition, we showed that zzz genes participate in OMV biogenesis, modulating different properties such as OMV size distribution, OMV yield and OMV protein cargo.
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Affiliation(s)
- Jan Nevermann
- Laboratorio de Genética y Patogénesis Bacteriana, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago, Chile
| | - Andrés Silva
- Laboratorio de Genética y Patogénesis Bacteriana, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago, Chile
| | - Carolina Otero
- Escuela de Química y Farmacia, Facultad de Medicina, Universidad Andres Bello, Santiago, Chile
| | - Diego P Oyarzún
- Center of Applied Nanosciences, Universidad Andres Bello, Santiago, Chile
| | - Boris Barrera
- Unidad de Microbiología, Hospital Clínico Universidad de Chile, Santiago, Chile
| | - Fernando Gil
- Microbiota-Host Interactions and Clostridia Research Group, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago, Chile
| | - Iván L Calderón
- Laboratorio de Genética y Patogénesis Bacteriana, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago, Chile
| | - Juan A Fuentes
- Laboratorio de Genética y Patogénesis Bacteriana, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago, Chile
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9
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Knöppel A, Knopp M, Albrecht LM, Lundin E, Lustig U, Näsvall J, Andersson DI. Genetic Adaptation to Growth Under Laboratory Conditions in Escherichia coli and Salmonella enterica. Front Microbiol 2018; 9:756. [PMID: 29755424 PMCID: PMC5933015 DOI: 10.3389/fmicb.2018.00756] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 04/04/2018] [Indexed: 11/16/2022] Open
Abstract
Experimental evolution under controlled laboratory conditions is becoming increasingly important to address various evolutionary questions, including, for example, the dynamics and mechanisms of genetic adaptation to different growth and stress conditions. In such experiments, mutations typically appear that increase the fitness under the conditions tested (medium adaptation), but that are not necessarily of interest for the specific research question. Here, we have identified mutations that appeared during serial passage of E. coli and S. enterica in four different and commonly used laboratory media and measured the relative competitive fitness and maximum growth rate of 111 genetically re-constituted strains, carrying different single and multiple mutations. Little overlap was found between the mutations that were selected in the two species and the different media, implying that adaptation occurs via different genetic pathways. Furthermore, we show that commonly occurring adaptive mutations can generate undesired genetic variation in a population and reduce the accuracy of competition experiments. However, by introducing media adaptation mutations with large effects into the parental strain that was used for the evolution experiment, the variation (standard deviation) was decreased 10-fold, and it was possible to measure fitness differences between two competitors as small as |s| < 0.001.
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Affiliation(s)
- Anna Knöppel
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Michael Knopp
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Lisa M Albrecht
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Erik Lundin
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Ulrika Lustig
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Joakim Näsvall
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Dan I Andersson
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
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10
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Horng YT, Wang CJ, Chung WT, Chao HJ, Chen YY, Soo PC. Phosphoenolpyruvate phosphotransferase system components positively regulate Klebsiella biofilm formation. JOURNAL OF MICROBIOLOGY, IMMUNOLOGY, AND INFECTION = WEI MIAN YU GAN RAN ZA ZHI 2018; 51:174-183. [DOI: 10.1016/j.jmii.2017.01.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Revised: 01/07/2017] [Accepted: 01/24/2017] [Indexed: 02/02/2023]
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11
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Jeng WY, Panjaitan NSD, Horng YT, Chung WT, Chien CC, Soo PC. The Negative Effects of KPN00353 on Glycerol Kinase and Microaerobic 1,3-Propanediol Production in Klebsiella pneumoniae. Front Microbiol 2017; 8:2441. [PMID: 29375490 PMCID: PMC5770620 DOI: 10.3389/fmicb.2017.02441] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 11/24/2017] [Indexed: 01/25/2023] Open
Abstract
1,3-Propanediol (1,3-PD) is a valuable chemical intermediate in the synthesis of polyesters, polyethers, and polyurethanes, which have applications in various products such as cloth, bottles, films, tarpaulins, canoes, foam seals, high-resilience foam seating, and surface coatings. Klebsiella pneumoniae can produce 1,3-PD from glycerol. In this study, KPN00353, an EIIA homologue in the phosphoenolpyruvate (PEP):carbohydrate phosphotransferase system (PTS), was found to play a negative regulatory role in 1,3-PD production under microaerobic conditions via binding to glycerol kinase (GlpK). The primary sequence of KPN00353 is similar to those of the fructose-mannitol EIIA (EIIFru and EIIAMtl) family. The interaction between KPN00353 and GlpK resulted in inhibition of the synthesis of glycerol-3-phosphate (G3P) and correlated with reductions in glycerol uptake and the production of 1,3-PD. Based on structure modeling, we conclude that residue H65 of KPN00353 plays an important role in the interaction with GlpK. We mutated this histidine residue to aspartate, glutamate, arginine and glutamine to assess the effects of each KPN00353 variant on the interaction with GlpK, on the synthesis of G3P and on the production of 1,3-PD. Our results illuminate the role of KPN00353 in 1,3-PD production by K. pneumoniae under microaerobic conditions.
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Affiliation(s)
- Wen-Yih Jeng
- University Center for Bioscience and Biotechnology, National Cheng Kung University, Tainan, Taiwan.,Department of Biochemistry and Molecular Biology, National Cheng Kung University, Tainan, Taiwan
| | - Novaria S D Panjaitan
- Institute of Medical Sciences, College of Medicine, Tzu Chi University, Hualien, Taiwan
| | - Yu-Tze Horng
- Department of Laboratory Medicine and Biotechnology, College of Medicine, Tzu Chi University, Hualien, Taiwan
| | - Wen-Ting Chung
- Department of Laboratory Medicine and Biotechnology, College of Medicine, Tzu Chi University, Hualien, Taiwan
| | - Chih-Ching Chien
- Graduate School of Biotechnology and Bioengineering, Yuan Ze University, Taoyuan, Taiwan
| | - Po-Chi Soo
- Institute of Medical Sciences, College of Medicine, Tzu Chi University, Hualien, Taiwan.,Department of Laboratory Medicine and Biotechnology, College of Medicine, Tzu Chi University, Hualien, Taiwan
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Interplay between tolerance mechanisms to copper and acid stress in Escherichia coli. Proc Natl Acad Sci U S A 2017; 114:6818-6823. [PMID: 28611214 DOI: 10.1073/pnas.1620232114] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Copper (Cu) is a key antibacterial component of the host innate immune system and almost all bacterial species possess systems that defend against the toxic effects of excess Cu. The Cu tolerance system in Gram-negative bacteria is composed minimally of a Cu sensor (CueR) and a Cu export pump (CopA). The cueR and copA genes are encoded on the chromosome typically as a divergent but contiguous operon. In Escherichia coli, cueR and copA are separated by two additional genes, ybaS and ybaT, which confer glutamine (Gln)-dependent acid tolerance and contribute to the glutamate (Glu)-dependent acid resistance system in this organism. Here we show that Cu strongly inhibits growth of a ∆copA mutant strain in acidic cultures. We further demonstrate that Cu stress impairs the pathway for Glu biosynthesis via glutamate synthase, leading to decreased intracellular levels of Glu. Addition of exogenous Glu rescues the ∆copA mutant from Cu stress in acidic conditions. Gln is also protective but this relies on the activities of YbaS and YbaT. Notably, expression of both enzymes is up-regulated during Cu stress. These results demonstrate a link between Cu stress, acid stress, and Glu/Gln metabolism, establish a role for YbaS and YbaT in Cu tolerance, and suggest that subtle changes in core metabolic pathways may contribute to overcoming host-imposed copper toxicity.
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Osman D, Piergentili C, Chen J, Sayer LN, Usón I, Huggins TG, Robinson NJ, Pohl E. The Effectors and Sensory Sites of Formaldehyde-responsive Regulator FrmR and Metal-sensing Variant. J Biol Chem 2016; 291:19502-16. [PMID: 27474740 PMCID: PMC5016687 DOI: 10.1074/jbc.m116.745174] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Revised: 07/21/2016] [Indexed: 11/29/2022] Open
Abstract
The DUF156 family of DNA-binding transcriptional regulators includes metal sensors that respond to cobalt and/or nickel (RcnR, InrS) or copper (CsoR) plus CstR, which responds to persulfide, and formaldehyde-responsive FrmR. Unexpectedly, the allosteric mechanism of FrmR from Salmonella enterica serovar Typhimurium is triggered by metals in vitro, and variant FrmR(E64H) gains responsiveness to Zn(II) and cobalt in vivo Here we establish that the allosteric mechanism of FrmR is triggered directly by formaldehyde in vitro Sensitivity to formaldehyde requires a cysteine (Cys(35) in FrmR) conserved in all DUF156 proteins. A crystal structure of metal- and formaldehyde-sensing FrmR(E64H) reveals that an FrmR-specific amino-terminal Pro(2) is proximal to Cys(35), and these residues form the deduced formaldehyde-sensing site. Evidence is presented that implies that residues spatially close to the conserved cysteine tune the sensitivities of DUF156 proteins above or below critical thresholds for different effectors, generating the semblance of specificity within cells. Relative to FrmR, RcnR is less responsive to formaldehyde in vitro, and RcnR does not sense formaldehyde in vivo, but reciprocal mutations FrmR(P2S) and RcnR(S2P), respectively, impair and enhance formaldehyde reactivity in vitro Formaldehyde detoxification by FrmA requires S-(hydroxymethyl)glutathione, yet glutathione inhibits formaldehyde detection by FrmR in vivo and in vitro Quantifying the number of FrmR molecules per cell and modeling formaldehyde modification as a function of [formaldehyde] demonstrates that FrmR reactivity is optimized such that FrmR is modified and frmRA is derepressed at lower [formaldehyde] than required to generate S-(hydroxymethyl)glutathione. Expression of FrmA is thereby coordinated with the accumulation of its substrate.
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Affiliation(s)
- Deenah Osman
- From the Department of Chemistry, School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, United Kingdom
| | - Cecilia Piergentili
- From the Department of Chemistry, School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, United Kingdom
| | - Junjun Chen
- Procter and Gamble, Mason Business Center, Cincinnati, Ohio 45040
| | | | - Isabel Usón
- the Instituto de Biología Molecular de Barcelona (IBMB-CSIC), Barcelona Science Park, 08028 Barcelona, Spain, and the Institució Catalana de Recerca i Estudis Avançats (ICREA), Pg. Lluís Companys 23, 08010 Barcelona, Spain
| | - Thomas G Huggins
- Procter and Gamble, Mason Business Center, Cincinnati, Ohio 45040
| | - Nigel J Robinson
- From the Department of Chemistry, School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, United Kingdom,
| | - Ehmke Pohl
- From the Department of Chemistry, School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, United Kingdom
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The Roles of Inflammation, Nutrient Availability and the Commensal Microbiota in Enteric Pathogen Infection. Microbiol Spectr 2016; 3. [PMID: 26185088 DOI: 10.1128/microbiolspec.mbp-0008-2014] [Citation(s) in RCA: 115] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The healthy human intestine is colonized by as many as 1014 bacteria belonging to more than 500 different species forming a microbial ecosystem of unsurpassed diversity, termed the microbiota. The microbiota's various bacterial members engage in a physiological network of cooperation and competition within several layers of complexity. Within the last 10 years, technological progress in the field of next-generation sequencing technologies has tremendously advanced our understanding of the wide variety of physiological and pathological processes that are influenced by the commensal microbiota (1, 2). An increasing number of human disease conditions, such as inflammatory bowel diseases (IBD), type 2 diabetes, obesity, allergies and colorectal cancer are linked with altered microbiota composition (3). Moreover, a clearer picture is emerging of the composition of the human microbiota in healthy individuals, its variability over time and between different persons and how the microbiota is shaped by environmental factors (i.e., diet) and the host's genetic background (4). A general feature of a normal, healthy gut microbiota can generate conditions in the gut that disfavor colonization of enteric pathogens. This is termed colonization-resistance (CR). Upon disturbance of the microbiota, CR can be transiently disrupted, and pathogens can gain the opportunity to grow to high levels. This disruption can be caused by exposure to antibiotics (5, 6), changes in diet (7, 8), application of probiotics and drugs (9), and a variety of diseases (3). Breakdown of CR can boost colonization by intrinsic pathogens or increase susceptibility to infections (10). One consequence of pathogen expansion is the triggering of inflammatory host responses and pathogen-mediated disease. Interestingly, human enteric pathogens are part of a small group of bacterial families that belong to the Proteobacteria: the Enterobacteriaceae (E. coli, Yersinia spp., Salmonella spp., Shigella spp.), the Vibrionaceae (Vibrio cholerae) and the Campylobacteriaceae (Campylobacter spp.). In general, members of these families (be it commensals or pathogens) only constitute a minority of the intestinal microbiota. However, proteobacterial "blooms" are a characteristic trait of an abnormal microbiota such as in the course of antibiotic therapy, dietary changes or inflammation (11). It has become clear that the gut microbiota not only plays a major role in priming and regulating mucosal and systemic immunity, but that the immune system also contributes to host control over microbiota composition. These two ways of mutual communication between the microbiota and the immune system were coined as "outside-in" and "inside-out," respectively (12). The significance of those interactions for human health is particularly evident in Crohn's disease (CD) and Ulcerative Colitis (UC). The symptoms of these recurrent, chronic types of gut inflammation are caused by an excessive immune response against one's own commensal microbiota (13). It is assumed that deregulated immune responses can be caused by a genetic predisposition, leading to, for example, the impairment of intestinal barrier function or disruption of mucosal T-cell homeostasis. In CD or UC patients, an abnormally composed microbiota, referred to as "dysbiosis," is commonly observed (discussed later). This is often characterized by an increased relative abundance of facultative anaerobic bacteria (e.g., Enterobacteriaeceae, Bacilli) and, at the same time, depletion of obligate anaerobic bacteria of the classes Bacteroidia and Clostridia. So far, it is unclear whether dysbiosis is a cause or a consequence of inflammatory bowel disease (IBD). In fact, both scenarios are equally conceivable. Recent work suggests that inflammatory immune responses in the gut (both IBD and pathogen-induced) can alter the gut luminal milieu in a way that favors dysbiosis (14). In this chapter, I present a survey on our current state of understanding of the characteristics and mechanisms underlying gut inflammation-associated dysbiosis. The role of dysbiosis in enteric infections and human IBD is discussed. In addition, I will focus on competition of enteric pathogens and the gut microbiota in the inflamed gut and the role of dysbiotic microbiota alterations (e.g., "Enterobacterial blooms" (11)) for the evolution of pathogenicity.
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Abstract
All living organisms are continually exposed to agents that damage their DNA, which threatens the integrity of their genome. As a consequence, cells are equipped with a plethora of DNA repair enzymes to remove the damaged DNA. Unfortunately, situations nevertheless arise where lesions persist, and these lesions block the progression of the cell's replicase. In these situations, cells are forced to choose between recombination-mediated "damage avoidance" pathways or a specialized DNA polymerase (pol) to traverse the blocking lesion. The latter process is referred to as Translesion DNA Synthesis (TLS). As inferred by its name, TLS not only results in bases being (mis)incorporated opposite DNA lesions but also bases being (mis)incorporated downstream of the replicase-blocking lesion, so as to ensure continued genome duplication and cell survival. Escherichia coli and Salmonella typhimurium possess five DNA polymerases, and while all have been shown to facilitate TLS under certain experimental conditions, it is clear that the LexA-regulated and damage-inducible pols II, IV, and V perform the vast majority of TLS under physiological conditions. Pol V can traverse a wide range of DNA lesions and performs the bulk of mutagenic TLS, whereas pol II and pol IV appear to be more specialized TLS polymerases.
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Loss of the lac Operon Contributes to Salmonella Invasion of Epithelial Cells Through Derepression of Flagellar Synthesis. Curr Microbiol 2014; 70:315-23. [DOI: 10.1007/s00284-014-0720-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2014] [Accepted: 09/18/2014] [Indexed: 12/12/2022]
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Lahiri C, Pawar S, Sabarinathan R, Ashraf MI, Chand Y, Chakravortty D. Interactome analyses of Salmonella pathogenicity islands reveal SicA indispensable for virulence. J Theor Biol 2014; 363:188-97. [PMID: 25128737 DOI: 10.1016/j.jtbi.2014.08.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 07/13/2014] [Accepted: 08/05/2014] [Indexed: 12/20/2022]
Abstract
BACKGROUND Serovars of Salmonella enterica, namely Typhi and Typhimurium, reportedly, are the bacterial pathogens causing systemic infections like gastroenteritis and typhoid fever. To elucidate the role and importance in such infection, the proteins of the Type III secretion system of Salmonella pathogenicity islands and two component signal transduction systems, have been mainly focused. However, the most indispensable of these virulent ones and their hierarchical role has not yet been studied extensively. RESULTS We have adopted a theoretical approach to build an interactome comprising the proteins from the Salmonella pathogeneicity islands (SPI) and two component signal transduction systems. This interactome was then analyzed by using network parameters like centrality and k-core measures. An initial step to capture the fingerprint of the core network resulted in a set of proteins which are involved in the process of invasion and colonization, thereby becoming more important in the process of infection. These proteins pertained to the Inv, Org, Prg, Sip, Spa, Ssa and Sse operons along with chaperone protein SicA. Amongst them, SicA was figured out to be the most indispensable protein from different network parametric analyses. Subsequently, the gene expression levels of all these theoretically identified important proteins were confirmed by microarray data analysis. Finally, we have proposed a hierarchy of the proteins involved in the total infection process. This theoretical approach is the first of its kind to figure out potential virulence determinants encoded by SPI for therapeutic targets for enteric infection. CONCLUSIONS A set of responsible virulent proteins was identified and the expression level of their genes was validated by using independent, published microarray data. The result was a targeted set of proteins that could serve as sensitive predictors and form the foundation for a series of trials in the wet-lab setting. Understanding these regulatory and virulent proteins would provide insight into conditions which are encountered by this intracellular enteric pathogen during the course of infection. This would further contribute in identifying novel targets for antimicrobial agents.
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Affiliation(s)
- Chandrajit Lahiri
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India.
| | - Shrikant Pawar
- Department of Biology, Georgia State University, Atlanta, GA 30303, USA.
| | | | - Md Izhar Ashraf
- B.S. Abdur Rahman University, Vandalur, Chennai 600048, India.
| | - Yamini Chand
- Department of Bioinformatics, Karunya University, Coimbatore 641114, India.
| | - Dipshikha Chakravortty
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India.
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Bronowski C, Fookes MC, Gilderthorp R, Ashelford KE, Harris SR, Phiri A, Hall N, Gordon MA, Wain J, Hart CA, Wigley P, Thomson NR, Winstanley C. Genomic characterisation of invasive non-typhoidal Salmonella enterica Subspecies enterica Serovar Bovismorbificans isolates from Malawi. PLoS Negl Trop Dis 2013; 7:e2557. [PMID: 24244782 PMCID: PMC3828162 DOI: 10.1371/journal.pntd.0002557] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Accepted: 10/11/2013] [Indexed: 11/18/2022] Open
Abstract
Background Invasive Non-typhoidal Salmonella (iNTS) are an important cause of bacteraemia in children and HIV-infected adults in sub-Saharan Africa. Previous research has shown that iNTS strains exhibit a pattern of gene loss that resembles that of host adapted serovars such as Salmonella Typhi and Paratyphi A. Salmonella enterica serovar Bovismorbificans was a common serovar in Malawi between 1997 and 2004. Methodology We sequenced the genomes of 14 Malawian bacteraemia and four veterinary isolates from the UK, to identify genomic variations and signs of host adaptation in the Malawian strains. Principal Findings Whole genome phylogeny of invasive and veterinary S. Bovismorbificans isolates showed that the isolates are highly related, belonging to the most common international S. Bovismorbificans Sequence Type, ST142, in contrast to the findings for S. Typhimurium, where a distinct Sequence Type, ST313, is associated with invasive disease in sub-Saharan Africa. Although genome degradation through pseudogene formation was observed in ST142 isolates, there were no clear overlaps with the patterns of gene loss seen in iNTS ST313 isolates previously described from Malawi, and no clear distinction between S. Bovismorbificans isolates from Malawi and the UK. The only defining differences between S. Bovismorbificans bacteraemia and veterinary isolates were prophage-related regions and the carriage of a S. Bovismorbificans virulence plasmid (pVIRBov). Conclusions iNTS S. Bovismorbificans isolates, unlike iNTS S. Typhiumrium isolates, are only distinguished from those circulating elsewhere by differences in the mobile genome. It is likely that these strains have entered a susceptible population and are able to take advantage of this niche. There are tentative signs of convergent evolution to a more human adapted iNTS variant. Considering its importance in causing disease in this region, S. Bovismorbificans may be at the beginning of this process, providing a reference against which to compare changes that may become fixed in future lineages in sub-Saharan Africa. Bacteraemia and meningitis caused by non-typhoidal Salmonella (including serovars Typhimurium, Enteritidis and Bovismorbificans) are a serious health issue in sub-Saharan Africa, particularly in young children and HIV-infected adults. Previous work has indicated that a distinct S. Typhimurium sequence type, ST313, has evolved and spread in these countries, and may be more human-adapted than isolates found in the developed world. We therefore investigated the genomes of Salmonella enterica serovar Bovismorbificans bacteraemia isolates from Malawi and compared them to genomes of veterinary S. Bovismorbificans isolates from the UK using Next Generation Sequencing Technology and subsequent genomic comparisons to establish if there is a genetic basis for this increase in invasive disease observed among African NTS. Contrary to the previous findings for S. Typhimurium, where a distinct ST is found only in sub-Saharan Africa, we discovered that the S. Bovismorbificans isolates from Malawi belong to the most common ST of the serovar and the genome is highly conserved across all sequenced isolates. The major differences between UK veterinary and African human isolates were due to prophage regions inserted into the genomes of African isolates, coupled with a higher prevalence of a virulence plasmid compared to the UK isolates.
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Affiliation(s)
- Christina Bronowski
- Institute of Infection and Global Health, University of Liverpool, Liverpool, United Kingdom
| | - Maria C. Fookes
- Pathogen Genomics, The Wellcome Trust Sanger Institute, Hinxton, Cambridge, United Kingdom
| | - Ruth Gilderthorp
- Pathogen Genomics, The Wellcome Trust Sanger Institute, Hinxton, Cambridge, United Kingdom
| | - Kevin E. Ashelford
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Simon R. Harris
- Pathogen Genomics, The Wellcome Trust Sanger Institute, Hinxton, Cambridge, United Kingdom
| | - Amos Phiri
- Malawi-Liverpool-Wellcome Trust Clinical Research Program, Queen Elizabeth Hospital, Blantyre, Malawi
| | - Neil Hall
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Melita A. Gordon
- Institute of Infection and Global Health, University of Liverpool, Liverpool, United Kingdom
- Malawi-Liverpool-Wellcome Trust Clinical Research Program, Queen Elizabeth Hospital, Blantyre, Malawi
- Department of Medicine, College of Medicine, University of Malawi, Malawi
| | - John Wain
- Department of Medical Microbiology, University of East Anglia, Norwich Research Park, Norwich, United Kingdom
| | - Charles A. Hart
- Institute of Infection and Global Health, University of Liverpool, Liverpool, United Kingdom
| | - Paul Wigley
- Institute of Infection and Global Health, University of Liverpool, Liverpool, United Kingdom
| | - Nicholas R. Thomson
- Pathogen Genomics, The Wellcome Trust Sanger Institute, Hinxton, Cambridge, United Kingdom
- * E-mail:
| | - Craig Winstanley
- Institute of Infection and Global Health, University of Liverpool, Liverpool, United Kingdom
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Two rep genes in small cryptic plasmid pKST21 of Escherichia coli. Curr Microbiol 2013; 67:437-41. [PMID: 23680975 DOI: 10.1007/s00284-013-0386-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Accepted: 04/17/2013] [Indexed: 10/26/2022]
Abstract
The complete nucleotide sequence of a small cryptic plasmid pKST21 from Escherichia coli was determined. This plasmid is 1,460 bp long with an overall GC content of 51 %. Based on sequence analysis, the presence of two segments with different average GC density was observed. The segment with higher GC content revealed 98-90 % similarity to several small plasmids of E. coli and to pCR1 from Gram-positive Corynebacterium renale. Plasmid pKST21 possesses two conversely oriented open reading frames encoding proteins with a high degree of amino acid identity to Rep proteins involved in replication. ORF1 encodes replication protein similar to RepA protein of Bartonella tribocorum or Bacillus cereus plasmids or to the putative plasmid Rep protein from ecologically close Selenomonas ruminantium. ORF2 similarly encodes a replication protein, which shares 97 % homology with Rep protein from C. renale. Genetic diversity observed in plasmid pKST21 indicates a mosaic structure of the plasmid with different segments acquired from different sources. Deletion analysis showed that both fragments carrying the repA and repB genes are necessary for the replication of pKST21 in E. coli. The presence of plasmid with the same gene composition was revealed in 14 % of tested E. coli isolates from the rumen of sheep. All these strains produced identical ERIC-PCR profiles indicating isogenic origin of the strain and lack of horizontal gene transfer of pKST21 plasmid.
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Elucidating the regulon of multidrug resistance regulator RarA in Klebsiella pneumoniae. Antimicrob Agents Chemother 2013; 57:1603-9. [PMID: 23318802 DOI: 10.1128/aac.01998-12] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
RarA is an AraC-type regulator in Klebsiella pneumoniae, which, when overexpressed, confers a low-level multidrug-resistant (MDR) phenotype linked to the upregulation of both the acrAB and oqxAB efflux genes. Increased rarA expression has also been shown to be integral in the development of tigecycline resistance in the absence of ramA in K. pneumoniae. Given its phenotypic role in MDR, microarray analyses were performed to determine the RarA regulon. Transcriptome analysis was undertaken using strains Ecl8ΔrarA/pACrarA-2 (rarA-expressing construct) and Ecl8ΔrarA/pACYC184 (vector-only control) using bespoke microarray slides consisting of probes derived from the genomic sequences of K. pneumoniae MGH 78578 (NC_009648.1) and Kp342 (NC_011283.1). Our results show that rarA overexpression resulted in the differential expression of 66 genes (42 upregulated and 24 downregulated). Under the COG (clusters of orthologous groups) functional classification, the majority of affected genes belonged to the category of cell envelope biogenesis and posttranslational modification, along with genes encoding the previously uncharacterized transport proteins (e.g., KPN_03141, sdaCB, and leuE) and the porin OmpF. However, genes associated with energy production and conversion and amino acid transport/metabolism (e.g., nuoA, narJ, and proWX) were found to be downregulated. Biolog phenotype analyses demonstrated that rarA overexpression confers enhanced growth of the overexpresser in the presence of several antibiotic classes (i.e., beta-lactams and fluoroquinolones), the antifungal/antiprotozoal compound clioquinol, disinfectants (8-hydroxyquinoline), protein synthesis inhibitors (i.e., minocycline and puromycin), membrane biogenesis agents (polymyxin B and amitriptyline), DNA synthesis (furaltadone), and the cytokinesis inhibitor (sanguinarine). Both our transcriptome and phenotypic microarray data support and extend the role of RarA in the MDR phenotype of K. pneumoniae.
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Kim D, Hong JSJ, Qiu Y, Nagarajan H, Seo JH, Cho BK, Tsai SF, Palsson BØ. Comparative analysis of regulatory elements between Escherichia coli and Klebsiella pneumoniae by genome-wide transcription start site profiling. PLoS Genet 2012; 8:e1002867. [PMID: 22912590 PMCID: PMC3415461 DOI: 10.1371/journal.pgen.1002867] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2012] [Accepted: 06/14/2012] [Indexed: 01/08/2023] Open
Abstract
Genome-wide transcription start site (TSS) profiles of the enterobacteria Escherichia coli and Klebsiella pneumoniae were experimentally determined through modified 5′ RACE followed by deep sequencing of intact primary mRNA. This identified 3,746 and 3,143 TSSs for E. coli and K. pneumoniae, respectively. Experimentally determined TSSs were then used to define promoter regions and 5′ UTRs upstream of coding genes. Comparative analysis of these regulatory elements revealed the use of multiple TSSs, identical sequence motifs of promoter and Shine-Dalgarno sequence, reflecting conserved gene expression apparatuses between the two species. In both species, over 70% of primary transcripts were expressed from operons having orthologous genes during exponential growth. However, expressed orthologous genes in E. coli and K. pneumoniae showed a strikingly different organization of upstream regulatory regions with only 20% identical promoters with TSSs in both species. Over 40% of promoters had TSSs identified in only one species, despite conserved promoter sequences existing in the other species. 662 conserved promoters having TSSs in both species resulted in the same number of comparable 5′ UTR pairs, and that regulatory element was found to be the most variant region in sequence among promoter, 5′ UTR, and ORF. In K. pneumoniae, 48 sRNAs were predicted and 36 of them were expressed during exponential growth. Among them, 34 orthologous sRNAs between two species were analyzed in depth, and the analysis showed that many sRNAs of K. pneumoniae, including pleiotropic sRNAs such as rprA, arcZ, and sgrS, may work in the same way as in E. coli. These results reveal a new dimension of comparative genomics such that a comparison of two genomes needs to be comprehensive over all levels of genome organization. In order to investigate similarities and differences of closely related species, most of the comparative genomics studies focus on comparing the gene contents either shared or specific for each genome. However, it is also important to investigate the differences in non-coding regulatory elements because they influence the transcriptional and post-transcriptional processes. Thus, we performed a genome-wide profiling of transcription start sites (TSSs) in two species, E. coli K-12 MG1655 and K. pneumoniae MGH78578. Experimental identification of TSSs is important for precise definition of promoter regions and 5′ untranslated regions upstream of coding genes. Comparative analysis of these regulatory elements revealed the use of multiple TSSs, identical sequence motifs of promoter and Shine-Dalgarno sequence. However, we observed that the upstream regulatory regions of the majority of operons having orthologous genes were organized with different usage of promoters and TSSs, resulting in diverse and complex gene regulation. We also found that the 5′ UTR is the least conserved regulatory element in sequence between the two species. Moreover, 34 orthologous sRNAs between E. coli and K. pneumoniae were analyzed in depth. The analysis suggested many of K. pneumoniae sRNAs might regulate the target genes as in E. coli.
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Affiliation(s)
- Donghyuk Kim
- Department of Bioengineering, University of California San Diego, La Jolla, California, United States of America
| | - Jay Sung-Joong Hong
- Department of Bioengineering, University of California San Diego, La Jolla, California, United States of America
| | - Yu Qiu
- Department of Bioengineering, University of California San Diego, La Jolla, California, United States of America
| | - Harish Nagarajan
- Department of Bioengineering, University of California San Diego, La Jolla, California, United States of America
| | - Joo-Hyun Seo
- Department of Bioengineering, University of California San Diego, La Jolla, California, United States of America
| | - Byung-Kwan Cho
- Department of Bioengineering, University of California San Diego, La Jolla, California, United States of America
| | - Shih-Feng Tsai
- Division of Molecular and Genomic Medicine, National Health Research Institutes, Miaoli, Taiwan
| | - Bernhard Ø. Palsson
- Department of Bioengineering, University of California San Diego, La Jolla, California, United States of America
- * E-mail:
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Characterization of RarA, a novel AraC family multidrug resistance regulator in Klebsiella pneumoniae. Antimicrob Agents Chemother 2012; 56:4450-8. [PMID: 22644028 DOI: 10.1128/aac.00456-12] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Transcriptional regulators, such as SoxS, RamA, MarA, and Rob, which upregulate the AcrAB efflux pump, have been shown to be associated with multidrug resistance in clinically relevant Gram-negative bacteria. In addition to the multidrug resistance phenotype, these regulators have also been shown to play a role in the cellular metabolism and possibly the virulence potential of microbial cells. As such, the increased expression of these proteins is likely to cause pleiotropic phenotypes. Klebsiella pneumoniae is a major nosocomial pathogen which can express the SoxS, MarA, Rob, and RamA proteins, and the accompanying paper shows that the increased transcription of ramA is associated with tigecycline resistance (M. Veleba and T. Schneiders, Antimicrob. Agents Chemother. 56:4466-4467, 2012). Bioinformatic analyses of the available Klebsiella genome sequences show that an additional AraC-type regulator is encoded chromosomally. In this work, we characterize this novel AraC-type regulator, hereby called RarA (Regulator of antibiotic resistance A), which is encoded in K. pneumoniae, Enterobacter sp. 638, Serratia proteamaculans 568, and Enterobacter cloacae. We show that the overexpression of rarA results in a multidrug resistance phenotype which requires a functional AcrAB efflux pump but is independent of the other AraC regulators. Quantitative real-time PCR experiments show that rarA (MGH 78578 KPN_02968) and its neighboring efflux pump operon oqxAB (KPN_02969_02970) are consistently upregulated in clinical isolates collected from various geographical locations (Chile, Turkey, and Germany). Our results suggest that rarA overexpression upregulates the oqxAB efflux pump. Additionally, it appears that oqxR, encoding a GntR-type regulator adjacent to the oqxAB operon, is able to downregulate the expression of the oqxAB efflux pump, where OqxR complementation resulted in reductions to olaquindox MICs.
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Wada T, Hatamoto Y, Kutsukake K. Functional and expressional analyses of the anti-FlhD4C2 factor gene ydiV in Escherichia coli. MICROBIOLOGY-SGM 2012; 158:1533-1542. [PMID: 22461489 DOI: 10.1099/mic.0.056036-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Although Escherichia coli and Salmonella enterica serovar Typhimurium have a similar flagellar regulatory system, the response of flagellar synthesis to nutrient conditions is quite different between the two: that is, in low-nutrient conditions, flagellar synthesis is inhibited in Salmonella and enhanced in E. coli. In Salmonella, this inhibition is mediated by an anti-FlhD(4)C(2) factor, YdiV, which is expressed in low-nutrient conditions and binds to FlhD(4)C(2) to inhibit the expression of the class 2 flagellar genes. The fliZ gene encodes a repressor of the ydiV gene, and thus is required for efficient flagellar gene expression in low-nutrient conditions in Salmonella. In this study, we showed that the E. coli ydiV gene encodes a protein which inhibits motility and flagellar production when expressed from a multicopy plasmid. We showed further that E. coli YdiV binds to FlhD(4)C(2) and inhibits its binding to the class 2 flagellar promoter. These results indicate that E. coli YdiV can also act as an anti-FlhD(4)C(2) factor. However, although the ydiV gene was transcribed efficiently in E. coli cells, the intracellular level of the YdiV protein was extremely low due to its inefficient translation. Consistent with this, E. coli cells did not require FliZ for efficient motility development. This indicates that, unlike in Salmonella, the FliZ-YdiV regulatory system does not work in the nutritional control of flagellar gene expression in E. coli.
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Affiliation(s)
- Takeo Wada
- Graduate School of Natural Science and Technology and Department of Biology, Faculty of Science, Okayama University, Tsushima-Naka 3-1-1, Kita-ku, Okayama 700-8530, Japan
| | - Yuki Hatamoto
- Graduate School of Natural Science and Technology and Department of Biology, Faculty of Science, Okayama University, Tsushima-Naka 3-1-1, Kita-ku, Okayama 700-8530, Japan
| | - Kazuhiro Kutsukake
- Graduate School of Natural Science and Technology and Department of Biology, Faculty of Science, Okayama University, Tsushima-Naka 3-1-1, Kita-ku, Okayama 700-8530, Japan
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Abstract
The first stress that foodborne pathogens find upon ingestion is the very acidic pH of the stomach of the host. In addition, intracellular pathogens like Salmonella are submitted to low pH inside the host cells. Two general acid survival systems are found in these organisms: acid resistance mechanisms and acid tolerance responses. These mechanisms involve the synthesis of a series of acid shock proteins. Only a subset of these proteins is directly involved in acid survival. This is related to the fact that low pH is not only a stress to cope with, but it is also an important signal that indicates to the bacterium that it is in a potential host environment and that triggers the induction of many virulence genes. Asr is an acid shock protein that supports growth of Escherichia coli at moderate acidity. In this issue of Virulence, Allam et al. investigate the role of STM1485, the homologous of asr in Salmonella enterica serovar Typhimurium, in acid survival and virulence. Although STM1485 is not required for acid survival of S. enterica, it is necessary for intracellular replication in human epithelial cells and murine macrophages, and to prevent the progression of the Salmonella-containing vacuole along the degradative pathway. In addition, Allam et al. are able to show that the defects of the STM1485 mutant at the cellular level correlate with reduced virulence in the mouse model.
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25
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Fookes M, Schroeder GN, Langridge GC, Blondel CJ, Mammina C, Connor TR, Seth-Smith H, Vernikos GS, Robinson KS, Sanders M, Petty NK, Kingsley RA, Bäumler AJ, Nuccio SP, Contreras I, Santiviago CA, Maskell D, Barrow P, Humphrey T, Nastasi A, Roberts M, Frankel G, Parkhill J, Dougan G, Thomson NR. Salmonella bongori provides insights into the evolution of the Salmonellae. PLoS Pathog 2011; 7:e1002191. [PMID: 21876672 PMCID: PMC3158058 DOI: 10.1371/journal.ppat.1002191] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Accepted: 06/21/2011] [Indexed: 02/05/2023] Open
Abstract
The genus Salmonella contains two species, S. bongori and S. enterica. Compared to the well-studied S. enterica there is a marked lack of information regarding the genetic makeup and diversity of S. bongori. S. bongori has been found predominantly associated with cold-blooded animals, but it can infect humans. To define the phylogeny of this species, and compare it to S. enterica, we have sequenced 28 isolates representing most of the known diversity of S. bongori. This cross-species analysis allowed us to confidently differentiate ancestral functions from those acquired following speciation, which include both metabolic and virulence-associated capacities. We show that, although S. bongori inherited a basic set of Salmonella common virulence functions, it has subsequently elaborated on this in a different direction to S. enterica. It is an established feature of S. enterica evolution that the acquisition of the type III secretion systems (T3SS-1 and T3SS-2) has been followed by the sequential acquisition of genes encoding secreted targets, termed effectors proteins. We show that this is also true of S. bongori, which has acquired an array of novel effector proteins (sboA-L). All but two of these effectors have no significant S. enterica homologues and instead are highly similar to those found in enteropathogenic Escherichia coli (EPEC). Remarkably, SboH is found to be a chimeric effector protein, encoded by a fusion of the T3SS-1 effector gene sopA and a gene highly similar to the EPEC effector nleH from enteropathogenic E. coli. We demonstrate that representatives of these new effectors are translocated and that SboH, similarly to NleH, blocks intrinsic apoptotic pathways while being targeted to the mitochondria by the SopA part of the fusion. This work suggests that S. bongori has inherited the ancestral Salmonella virulence gene set, but has adapted by incorporating virulence determinants that resemble those employed by EPEC.
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Affiliation(s)
- Maria Fookes
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Gunnar N. Schroeder
- Centre for Molecular Microbiology and Infection, Division of Cell and Molecular Biology, Imperial College London, London, United Kingdom
| | - Gemma C. Langridge
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Carlos J. Blondel
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
| | - Caterina Mammina
- Dept. Sciences for Health Promotion “G. D'Alessandro”, University of Palermo, Palermo, Italy
| | - Thomas R. Connor
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Helena Seth-Smith
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Georgios S. Vernikos
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Keith S. Robinson
- Centre for Molecular Microbiology and Infection, Division of Cell and Molecular Biology, Imperial College London, London, United Kingdom
| | - Mandy Sanders
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Nicola K. Petty
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Robert A. Kingsley
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Andreas J. Bäumler
- Department of Medical Microbiology and Immunology, School of Medicine, University of California at Davis, Davis, California, United State of America
| | - Sean-Paul Nuccio
- Department of Medical Microbiology and Immunology, School of Medicine, University of California at Davis, Davis, California, United State of America
| | - Inés Contreras
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
| | - Carlos A. Santiviago
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
| | - Duncan Maskell
- Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Paul Barrow
- School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington, Leicestershire, United Kingdom
| | - Tom Humphrey
- National Centre for Zoonosis Research, University of Liverpool, Leahurst Campus, Neston, Wirral, United Kingdom
| | | | - Mark Roberts
- Institute of Comparative Medicine, Faculty of Veterinary Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Gad Frankel
- Centre for Molecular Microbiology and Infection, Division of Cell and Molecular Biology, Imperial College London, London, United Kingdom
| | - Julian Parkhill
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Gordon Dougan
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Nicholas R. Thomson
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
- * E-mail:
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26
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Evans MR, Fink RC, Vazquez-Torres A, Porwollik S, Jones-Carson J, McClelland M, Hassan HM. Analysis of the ArcA regulon in anaerobically grown Salmonella enterica sv. Typhimurium. BMC Microbiol 2011; 11:58. [PMID: 21418628 PMCID: PMC3075218 DOI: 10.1186/1471-2180-11-58] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2010] [Accepted: 03/21/2011] [Indexed: 12/18/2022] Open
Abstract
Background Salmonella enterica serovar Typhimurium (S. Typhimurium) is a Gram-negative pathogen that must successfully adapt to the broad fluctuations in the concentration of dissolved dioxygen encountered in the host. In Escherichia coli, ArcA (Aerobic Respiratory Control) helps the cells to sense and respond to the presence of dioxygen. The global role of ArcA in E. coli is well characterized; however, little is known about its role in anaerobically grown S. Typhimurium. Results We compared the transcriptional profiles of the virulent wild-type (WT) strain (ATCC 14028s) and its isogenic arcA mutant grown under anaerobic conditions. We found that ArcA directly or indirectly regulates 392 genes (8.5% of the genome); of these, 138 genes are poorly characterized. Regulation by ArcA in S. Typhimurium is similar, but distinct from that in E. coli. Thus, genes/operons involved in core metabolic pathways (e.g., succinyl-CoA, fatty acid degradation, cytochrome oxidase complexes, flagellar biosynthesis, motility, and chemotaxis) were regulated similarly in the two organisms. However, genes/operons present in both organisms, but regulated differently by ArcA in S. Typhimurium included those coding for ethanolamine utilization, lactate transport and metabolism, and succinate dehydrogenases. Salmonella-specific genes/operons regulated by ArcA included those required for propanediol utilization, flagellar genes (mcpAC, cheV), Gifsy-1 prophage genes, and three SPI-3 genes (mgtBC, slsA, STM3784). In agreement with our microarray data, the arcA mutant was non-motile, lacked flagella, and was as virulent in mice as the WT. Additionally, we identified a set of 120 genes whose regulation was shared with the anaerobic redox regulator, Fnr. Conclusion(s) We have identified the ArcA regulon in anaerobically grown S. Typhimurium. Our results demonstrated that in S. Typhimurium, ArcA serves as a transcriptional regulator coordinating cellular metabolism, flagella biosynthesis, and motility. Furthermore, ArcA and Fnr share in the regulation of 120 S. Typhimurium genes.
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Affiliation(s)
- Matthew R Evans
- Department of Microbiology, North Carolina State University, Raleigh, North Carolina 27695-7615, USA
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27
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Friedrich T, Rahmann S, Weigel W, Rabsch W, Fruth A, Ron E, Gunzer F, Dandekar T, Hacker J, Müller T, Dobrindt U. High-throughput microarray technology in diagnostics of enterobacteria based on genome-wide probe selection and regression analysis. BMC Genomics 2010; 11:591. [PMID: 20964857 PMCID: PMC3017858 DOI: 10.1186/1471-2164-11-591] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2010] [Accepted: 10/21/2010] [Indexed: 12/02/2022] Open
Abstract
Background The Enterobacteriaceae comprise a large number of clinically relevant species with several individual subspecies. Overlapping virulence-associated gene pools and the high overall genome plasticity often interferes with correct enterobacterial strain typing and risk assessment. Array technology offers a fast, reproducible and standardisable means for bacterial typing and thus provides many advantages for bacterial diagnostics, risk assessment and surveillance. The development of highly discriminative broad-range microbial diagnostic microarrays remains a challenge, because of marked genome plasticity of many bacterial pathogens. Results We developed a DNA microarray for strain typing and detection of major antimicrobial resistance genes of clinically relevant enterobacteria. For this purpose, we applied a global genome-wide probe selection strategy on 32 available complete enterobacterial genomes combined with a regression model for pathogen classification. The discriminative power of the probe set was further tested in silico on 15 additional complete enterobacterial genome sequences. DNA microarrays based on the selected probes were used to type 92 clinical enterobacterial isolates. Phenotypic tests confirmed the array-based typing results and corroborate that the selected probes allowed correct typing and prediction of major antibiotic resistances of clinically relevant Enterobacteriaceae, including the subspecies level, e.g. the reliable distinction of different E. coli pathotypes. Conclusions Our results demonstrate that the global probe selection approach based on longest common factor statistics as well as the design of a DNA microarray with a restricted set of discriminative probes enables robust discrimination of different enterobacterial variants and represents a proof of concept that can be adopted for diagnostics of a wide range of microbial pathogens. Our approach circumvents misclassifications arising from the application of virulence markers, which are highly affected by horizontal gene transfer. Moreover, a broad range of pathogens have been covered by an efficient probe set size enabling the design of high-throughput diagnostics.
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Affiliation(s)
- Torben Friedrich
- University of Würzburg, Institute for Molecular Infection Biology, Würzburg, Germany
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28
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Jackson AP, Thomas GH, Parkhill J, Thomson NR. Evolutionary diversification of an ancient gene family (rhs) through C-terminal displacement. BMC Genomics 2009; 10:584. [PMID: 19968874 PMCID: PMC2935791 DOI: 10.1186/1471-2164-10-584] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Accepted: 12/07/2009] [Indexed: 12/29/2022] Open
Abstract
Background Rhs genes are prominent features of bacterial genomes that have previously been implicated in genomic rearrangements in E. coli. By comparing rhs repertoires across the Enterobacteriaceae, this study provides a robust explanation of rhs diversification and evolution, and a mechanistic model of how rhs diversity is gained and lost. Results Rhs genes are ubiquitous and comprise six structurally distinct lineages within the Enterobacteriaceae. There is considerable intergenomic variation in rhs repertoire; for instance, in Salmonella enterica, rhs are restricted to mobile elements, while in Escherichia coli one rhs lineage has diversified through transposition as older lineages have been deleted. Overall, comparative genomics reveals frequent, independent gene gains and losses, as well as occasional lateral gene transfer, in different genera. Furthermore, we demonstrate that Rhs 'core' domains and variable C-termini are evolutionarily decoupled, and propose that rhs diversity is driven by homologous recombination with circular intermediates. Existing C-termini are displaced by laterally acquired alternatives, creating long arrays of dissociated 'tips' that characterize the appearance of rhs loci. Conclusion Rhs repertoires are highly dynamic among Enterobacterial genomes, due to repeated gene gains and losses. In contrast, the primary structures of Rhs genes are evolutionarily conserved, indicating that rhs sequence diversity is driven, not by rapid mutation, but by the relatively slow evolution of novel core/tip combinations. Hence, we predict that a large pool of dissociated rhs C-terminal tips exists episomally and these are potentially transmitted across taxonomic boundaries.
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Affiliation(s)
- Andrew P Jackson
- The Wellcome Trust Sanger Institute, Genome Campus, Hinxton, Cambridge, CB10 1SA, UK.
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29
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AbuOun M, Suthers PF, Jones GI, Carter BR, Saunders MP, Maranas CD, Woodward MJ, Anjum MF. Genome scale reconstruction of a Salmonella metabolic model: comparison of similarity and differences with a commensal Escherichia coli strain. J Biol Chem 2009; 284:29480-8. [PMID: 19690172 PMCID: PMC2785581 DOI: 10.1074/jbc.m109.005868] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2009] [Revised: 07/21/2009] [Indexed: 01/10/2023] Open
Abstract
Salmonella are closely related to commensal Escherichia coli but have gained virulence factors enabling them to behave as enteric pathogens. Less well studied are the similarities and differences that exist between the metabolic properties of these organisms that may contribute toward niche adaptation of Salmonella pathogens. To address this, we have constructed a genome scale Salmonella metabolic model (iMA945). The model comprises 945 open reading frames or genes, 1964 reactions, and 1036 metabolites. There was significant overlap with genes present in E. coli MG1655 model iAF1260. In silico growth predictions were simulated using the model on different carbon, nitrogen, phosphorous, and sulfur sources. These were compared with substrate utilization data gathered from high throughput phenotyping microarrays revealing good agreement. Of the compounds tested, the majority were utilizable by both Salmonella and E. coli. Nevertheless a number of differences were identified both between Salmonella and E. coli and also within the Salmonella strains included. These differences provide valuable insight into differences between a commensal and a closely related pathogen and within different pathogenic strains opening new avenues for future explorations.
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Affiliation(s)
- Manal AbuOun
- Department of Food and Environmental Safety, Veterinary Laboratories Agency (Weybridge), Addlestone, Surrey KT153NB, United Kingdom.
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30
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Virulent clones of Klebsiella pneumoniae: identification and evolutionary scenario based on genomic and phenotypic characterization. PLoS One 2009; 4:e4982. [PMID: 19319196 PMCID: PMC2656620 DOI: 10.1371/journal.pone.0004982] [Citation(s) in RCA: 322] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2008] [Accepted: 01/31/2009] [Indexed: 11/25/2022] Open
Abstract
Klebsiella pneumoniae is found in the environment and as a harmless commensal, but is also a frequent nosocomial pathogen (causing urinary, respiratory and blood infections) and the agent of specific human infections including Friedländer's pneumonia, rhinoscleroma and the emerging disease pyogenic liver abscess (PLA). The identification and precise definition of virulent clones, i.e. groups of strains with a single ancestor that are associated with particular infections, is critical to understand the evolution of pathogenicity from commensalism and for a better control of infections. We analyzed 235 K. pneumoniae isolates of diverse environmental and clinical origins by multilocus sequence typing, virulence gene content, biochemical and capsular profiling and virulence to mice. Phylogenetic analysis of housekeeping genes clearly defined clones that differ sharply by their clinical source and biological features. First, two clones comprising isolates of capsular type K1, clone CC23K1 and clone CC82K1, were strongly associated with PLA and respiratory infection, respectively. Second, only one of the two major disclosed K2 clones was highly virulent to mice. Third, strains associated with the human infections ozena and rhinoscleroma each corresponded to one monomorphic clone. Therefore, K. pneumoniae subsp. ozaenae and K. pneumoniae subsp. rhinoscleromatis should be regarded as virulent clones derived from K. pneumoniae. The lack of strict association of virulent capsular types with clones was explained by horizontal transfer of the cps operon, responsible for the synthesis of the capsular polysaccharide. Finally, the reduction of metabolic versatility observed in clones Rhinoscleromatis, Ozaenae and CC82K1 indicates an evolutionary process of specialization to a pathogenic lifestyle. In contrast, clone CC23K1 remains metabolically versatile, suggesting recent acquisition of invasive potential. In conclusion, our results reveal the existence of important virulent clones associated with specific infections and provide an evolutionary framework for research into the links between clones, virulence and other genomic features in K. pneumoniae.
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31
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Guillier M, Gottesman S. The 5' end of two redundant sRNAs is involved in the regulation of multiple targets, including their own regulator. Nucleic Acids Res 2008; 36:6781-94. [PMID: 18953042 PMCID: PMC2588501 DOI: 10.1093/nar/gkn742] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Small RNAs are widespread regulators of gene expression in numerous organisms. This study describes the mode of action of two redundant Escherichia coli sRNAs, OmrA and OmrB, that downregulate the expression of multiple targets, most of which encode outer membrane proteins. Our results show that both sRNAs directly interact with at least two of these target mRNAs, ompT and cirA, in the vicinity of the translation initiation region, consistent with control of these targets being dependent on both Hfq and RNase E. Interestingly, these interactions depend on short stretches of complementarity and involve the conserved 5' end of OmrA/B. A mutation in this region abolishes control of all OmrA/B targets tested thus far, thereby highlighting the crucial role of the OmrA/B 5' end. This allowed us, by looking for mRNA sequences complementary to the OmrA/B 5' end, to identify ompR as an additional direct target of these two sRNAs. Since the OmpR transcriptional regulator activates expression of both omrA and omrB genes, this newly identified control should result in an autoregulatory loop limiting the amount of OmrA/B sRNAs.
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Affiliation(s)
- Maude Guillier
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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32
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Mukherjee A, Jackson SA, LeClerc JE, Cebula TA. Exploring Genotypic and Phenotypic Diversity of Microbes Using Microarray Approaches. Toxicol Mech Methods 2008; 16:121-8. [DOI: 10.1080/15376520600558473] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Salmonella enterica serovar gallinarum requires ppGpp for internalization and survival in animal cells. J Bacteriol 2008; 190:6340-50. [PMID: 18621899 DOI: 10.1128/jb.00385-08] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To elucidate the pathogenic mechanism of Salmonella enterica serovar Gallinarum, we examined the expression of the genes encoded primarily in Salmonella pathogenicity island 1 (SPI-1) and SPI-2. These genes were found to be induced as cultures entered stationary phase under high- and low-oxygen growth conditions, as also observed for Salmonella serovar Typhimurium. In contrast, Salmonella serovar Gallinarum in the exponential growth phase most efficiently internalized cultured animal cells. Analysis of mutants defective in SPI-1 genes, SPI-2 genes, and others implicated in early stages of infection revealed that SPI-1 genes were not involved in the internalization of animal cells by Salmonella serovar Gallinarum. Following entry, however, Salmonella serovar Gallinarum was found to reside in LAMP1-positive vacuoles in both phagocytic and nonphagocytic cells, although internalization was independent of SPI-1. A mutation that conferred defects in ppGpp synthesis was the only one found to affect animal cell internalization by Salmonella serovar Gallinarum. It was concluded that Salmonella serovar Gallinarum internalizes animal cells by a mechanism independent of SPI-1 genes but dependent on ppGpp. Intracellular growth also required ppGpp for the transcription of genes encoded in SPI-2.
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34
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Middha S, Wang X. Evolution and potential function of fibrinogen-like domains across twelve Drosophila species. BMC Genomics 2008; 9:260. [PMID: 18513432 PMCID: PMC2429915 DOI: 10.1186/1471-2164-9-260] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2007] [Accepted: 05/30/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The fibrinogen-like (FBG) domain consists of approximately 200 amino acid residues, which has high sequence similarity to the C-terminal halves of fibrinogen beta and gamma chains. Fibrinogen-related proteins (FREPs) containing one or more FBG domains are found universally in vertebrates and invertebrates. In invertebrates, FREPs are involved in immune responses and other aspects of physiology. To understand the complexity of this gene family in Drosophila, we analyzed FREPs in twelve Drosophila species. RESULTS Using the genome data from 12 Drosophila species, we identified FBG domains in each species. The results show that the gene numbers in each species vary from 14 genes up to 43 genes. Using sequence profile analysis, we found that FBG domains have high sequence similarity and are highly conserved throughout. By comparison of structure and sequence conservation, some of the FBG domains in Drosophila melanogaster are predicted to function in recognition of carbohydrates and their derivatives on the surface of microorganisms in innate immunity. CONCLUSION Sequence and structural analyses show that FREP family across 12 Drosophila species contains conserved FBG domains. Expansion of the FREP families in Drosophila is mainly accounted by a major expansion of FBG domains.
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Affiliation(s)
- Sumit Middha
- Center for Genomics and Bioinformatics, Indiana University, Bloomington, IN 47405, USA.
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35
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Li QR, Carvunis AR, Yu H, Han JDJ, Zhong Q, Simonis N, Tam S, Hao T, Klitgord NJ, Dupuy D, Mou D, Wapinski I, Regev A, Hill DE, Cusick ME, Vidal M. Revisiting the Saccharomyces cerevisiae predicted ORFeome. Genome Res 2008; 18:1294-303. [PMID: 18502943 DOI: 10.1101/gr.076661.108] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Accurately defining the coding potential of an organism, i.e., all protein-encoding open reading frames (ORFs) or "ORFeome," is a prerequisite to fully understand its biology. ORFeome annotation involves iterative computational predictions from genome sequences combined with experimental verifications. Here we reexamine a set of Saccharomyces cerevisiae "orphan" ORFs recently removed from the original ORFeome annotation due to lack of conservation across evolutionarily related yeast species. We show that many orphan ORFs produce detectable transcripts and/or translated products in various functional genomics and proteomics experiments. By combining a naïve Bayes model that predicts the likelihood of an ORF to encode a functional product with experimental verification of strand-specific transcripts, we argue that orphan ORFs should still remain candidates for functional ORFs. In support of this model, interstrain intraspecies genome sequence variation is lower across orphan ORFs than in intergenic regions, indicating that orphan ORFs endure functional constraints and resist deleterious mutations. We conclude that ORFs should be evaluated based on multiple levels of evidence and not be removed from ORFeome annotation solely based on low sequence conservation in other species. Rather, such ORFs might be important for micro-evolutionary divergence between species.
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Affiliation(s)
- Qian-Ru Li
- Center for Cancer Systems Biology (CCSB) and Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA
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Elnitski L, Riemer C, Schwartz S, Hardison R, Miller W. PipMaker: a World Wide Web server for genomic sequence alignments. ACTA ACUST UNITED AC 2008; Chapter 10:Unit 10.2. [PMID: 18428692 DOI: 10.1002/0471250953.bi1002s00] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
PipMaker is a World-Wide Web site used to compare two long genomic sequences and identify conserved segments between them. This unit describes the use of the PipMaker server and explains the resulting output files. PipMaker provides an efficient method of aligning genomic sequences and returns a compact, but easy-to-interpret form of output, the percent identity plot (pip). For each aligning segment between two sequences the pip shows both the position relative to the first sequence and the degree of similarity. Optional annotations on the pip provide additional information to assist in the interpretation of the alignment. The default parameters of the underlying blastz alignment program are tuned for human-mouse alignments.
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Affiliation(s)
- Laura Elnitski
- The Pennsylvania State University, University Park, Pennsylvania, USA
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37
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Molecular variations in Klebsiella pneumoniae and Escherichia coli FimH affect function and pathogenesis in the urinary tract. Infect Immun 2008; 76:3346-56. [PMID: 18474655 DOI: 10.1128/iai.00340-08] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Type 1 pili mediate binding, invasion, and biofilm formation of uropathogenic Escherichia coli (UPEC) in the host urothelium during urinary tract infection (UTI) via the adhesin FimH. In this study, we characterized the molecular basis of functional differences between FimH of the UPEC isolate UTI89 and the Klebsiella pneumoniae cystitis isolate TOP52. Type 1 pili characteristically mediate mannose-sensitive hemagglutination of guinea pig erythrocytes. Although the adhesin domain of K. pneumoniae TOP52 FimH (FimH(52)) is highly homologous to that of E. coli, with an identical mannose binding pocket and surrounding hydrophobic ridge, it lacks the ability to agglutinate guinea pig erythrocytes. In addition, FimH-dependent biofilm formation in K. pneumoniae is inhibited by heptyl mannose, but not methyl mannose, suggesting the need for contacts outside of the mannose binding pocket. The binding specificity differences observed for FimH(52) resulted in significant functional differences seen in the pathogenesis of K. pneumoniae UTI compared to E. coli UTI. Infections in a murine model of UTI demonstrated that although the K. pneumoniae strain TOP52 required FimH(52) for invasion and IBC formation in the bladder, FimH(52) was not essential for early colonization. This work reveals that a limited amount of sequence variation between the FimH of E. coli and K. pneumoniae results in significant differences in function and ability to colonize the urinary tract.
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Utilization of an intracellular bacterial community pathway in Klebsiella pneumoniae urinary tract infection and the effects of FimK on type 1 pilus expression. Infect Immun 2008; 76:3337-45. [PMID: 18411285 DOI: 10.1128/iai.00090-08] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Klebsiella pneumoniae is an important cause of urinary tract infection (UTI), but little is known about its pathogenesis in vivo. The pathogenesis of the K. pneumoniae cystitis isolate TOP52 was compared to that of the uropathogenic Escherichia coli (UPEC) isolate UTI89 in a murine cystitis model. Bladder and kidney titers of TOP52 were lower than those of UTI89 at early time points but similar at later time points. TOP52, like UTI89, formed biofilm-like intracellular bacterial communities (IBCs) within the murine bladder, albeit at significantly lower levels than UTI89. Additionally, filamentation of TOP52 was observed, a process critical for UTI89 evasion of neutrophil phagocytosis and persistence in the bladder. Thus, the IBC pathway is not specific to UPEC alone. We investigated if differences in type 1 pilus expression may explain TOP52's early defect in vivo. The type 1 pilus operon is controlled by recombinase-mediated (fimE, fimB, and fimX) phase variation of an invertible promoter element. We found that K. pneumoniae carries an extra gene of unknown function at the 3' end of its type 1 operon, fimK, and the genome lacks the recombinase fimX. A deletion mutant of fimK was constructed, and TOP52 Delta fimK had higher titers and formed more IBCs in the murine cystitis model than wild type. The loss of fimK or expression of E. coli fimX from a plasmid in TOP52 resulted in a larger phase-ON population and higher expression levels of type 1 pili and gave TOP52 the ability to form type 1-dependent biofilms. Complementation with pfimK decreased type 1 pilus expression and biofilm formation of TOP52 Delta fimK and decreased UTI89 biofilm formation. Thus, K. pneumoniae appears programmed for minimal expression of type 1 pili, which may explain, in part, why K. pneumoniae is a less prevalent etiologic agent of UTI than UPEC.
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Vernikos GS, Thomson NR, Parkhill J. Genetic flux over time in the Salmonella lineage. Genome Biol 2008; 8:R100. [PMID: 17547764 PMCID: PMC2394748 DOI: 10.1186/gb-2007-8-6-r100] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2006] [Revised: 03/29/2007] [Accepted: 06/04/2007] [Indexed: 11/17/2022] Open
Abstract
From a whole-genome comparative analysis of Salmonella, Escherichia coli and Shigella strains, the relative time of insertion of putative horizontally acquired genes in three Salmonella strains were inferred, highlighting the major impact of horizontal transfer in the evolution of the salmonellae. Background DNA sequences that are shared between closely related organisms while being absent from their common ancestor and from sister lineages of that ancestor are likely to have been acquired by horizontal gene transfer. Over time, the composition of those sequences tends to become more similar to the compositional signature of their host (amelioration). Results From a whole-genome comparative analysis of eleven Salmonella, three Escherichia coli and one Shigella strain, we inferred the relative time of insertion of putative horizontally acquired (PHA) genes in three Salmonella strains on different branches of the S. enterica phylogenetic tree. Compositional analysis suggests that most of the PHA genes are still undergoing an amelioration process and shows a clear correlation between time of insertion and the level of amelioration. Conclusion The results show that older insertions include almost all functional classes. However, very recent horizontal transfer events in the Salmonella lineage involve primarily prophage elements that are shared only between very recently diverged lineages; despite this, the prophage sequence composition is close to that of the host, indicating that host adaptation, rather than amelioration, is likely to be the source of the compositional similarity. Almost half of the PHA genes were acquired at the base of the Salmonella lineage, whereas nearly three-quarters are shared between most S. enterica subspecies. The numerical distribution of PHA genes in the Salmonella tree topology correlates well with the divergence of the major Salmonella species, highlighting the major impact of horizontal transfer on the evolution of the salmonellae.
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Affiliation(s)
- Georgios S Vernikos
- The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK
| | - Nicholas R Thomson
- The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK
| | - Julian Parkhill
- The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK
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Manna D, Porwollik S, McClelland M, Tan R, Higgins NP. Microarray analysis of Mu transposition in Salmonella enterica, serovar Typhimurium: transposon exclusion by high-density DNA binding proteins. Mol Microbiol 2007; 66:315-28. [PMID: 17850262 DOI: 10.1111/j.1365-2958.2007.05915.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
All organisms contain transposons with the potential to disrupt and rearrange genes. Despite the presence of these destabilizing sequences, some genomes show remarkable stability over evolutionary time. Do bacteria defend the genome against disruption by transposons? Phage Mu replicates by transposition and virtually all genes are potential insertion targets. To test whether bacteria limit Mu transposition to specific parts of the chromosome, DNA arrays of Salmonella enterica were used to quantitatively measure target site preference and compare the data with Escherichia coli. Essential genes were as susceptible to transposon disruption as non-essential ones in both organisms, but the correlation of transposition hot spots among homologous genes was poor. Genes in highly transcribed operons were insulated from transposon mutagenesis in both organisms. A 10 kb cold spot on the pSLT plasmid was near parS, a site to which the ParB protein binds and spreads along DNA. Deleting ParB erased the plasmid cold spot, and an ectopic parS site placed in the Salmonella chromosome created a new cold spot in the presence of ParB. Our data show that competition between cellular proteins and transposition proteins on plasmids and the chromosome is a dominant factor controlling the genetic footprint of transposons in living cells.
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Affiliation(s)
- Dipankar Manna
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL-35294, USA
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Characterization of Escherichia coli MG1655 grown in a low-shear modeled microgravity environment. BMC Microbiol 2007; 7:15. [PMID: 17343762 PMCID: PMC1852313 DOI: 10.1186/1471-2180-7-15] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2006] [Accepted: 03/07/2007] [Indexed: 01/24/2023] Open
Abstract
Background Extra-cellular shear force is an important environmental parameter that is significant both medically and in the space environment. Escherichia coli cells grown in a low-shear modeled microgravity (LSMMG) environment produced in a high aspect rotating vessel (HARV) were subjected to transcriptional and physiological analysis. Results Aerobic LSMMG cultures were grown in rich (LB) and minimal (MOPS + glucose) medium with a normal gravity vector HARV control. Reproducible changes in transcription were seen, but no specific LSMMG responsive genes were identified. Instead, absence of shear and a randomized gravity vector appears to cause local extra-cellular environmental changes, which elicit reproducible cellular responses. In minimal media, the majority of the significantly up- or down-regulated genes of known function were associated with the cell envelope. In rich medium, most LSMMG down-regulated genes were involved in translation. No observable changes in post-culture stress responses and antibiotic sensitivity were seen in cells immediately after exposure to LSMMG. Comparison with earlier studies of Salmonella enterica serovar Typhimurium conducted under similar growth conditions, revealed essentially no similarity in the genes that were significantly up- or down-regulated. Conclusion Comparison of these results to previous studies suggests that different organisms may dramatically differ in their responses to medically significant low-shear and space environments. Depending on their specific response, some organisms, such as Salmonella, may become preadapted in a manner that predisposes them to increased virulence.
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Fink RC, Evans MR, Porwollik S, Vazquez-Torres A, Jones-Carson J, Troxell B, Libby SJ, McClelland M, Hassan HM. FNR is a global regulator of virulence and anaerobic metabolism in Salmonella enterica serovar Typhimurium (ATCC 14028s). J Bacteriol 2007; 189:2262-73. [PMID: 17220229 PMCID: PMC1899381 DOI: 10.1128/jb.00726-06] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Salmonella enterica serovar Typhimurium must successfully transition the broad fluctuations in oxygen concentrations encountered in the host. In Escherichia coli, FNR is one of the main regulatory proteins involved in O2 sensing. To assess the role of FNR in serovar Typhimurium, we constructed an isogenic fnr mutant in the virulent wild-type strain (ATCC 14028s) and compared their transcriptional profiles and pathogenicities in mice. Here, we report that, under anaerobic conditions, 311 genes (6.80% of the genome) are regulated directly or indirectly by FNR; of these, 87 genes (28%) are poorly characterized. Regulation by FNR in serovar Typhimurium is similar to, but distinct from, that in E. coli. Thus, genes/operons involved in aerobic metabolism, NO. detoxification, flagellar biosynthesis, motility, chemotaxis, and anaerobic carbon utilization are regulated by FNR in a fashion similar to that in E. coli. However, genes/operons existing in E. coli but regulated by FNR only in serovar Typhimurium include those coding for ethanolamine utilization, a universal stress protein, a ferritin-like protein, and a phosphotransacetylase. Interestingly, Salmonella-specific genes/operons regulated by FNR include numerous virulence genes within Salmonella pathogenicity island 1 (SPI-1), newly identified flagellar genes (mcpAC, cheV), and the virulence operon (srfABC). Furthermore, the role of FNR as a positive regulator of motility, flagellar biosynthesis, and pathogenesis was confirmed by showing that the mutant is nonmotile, lacks flagella, is attenuated in mice, and does not survive inside macrophages. The inability of the mutant to survive inside macrophages is likely due to its sensitivity to the reactive oxygen species generated by NADPH phagocyte oxidase.
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Affiliation(s)
- Ryan C Fink
- Department of Microbiology, North Carolina State University, Raleigh, NC 27695-7615, USA
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Malorny B, Bunge C, Guerra B, Prietz S, Helmuth R. Molecular characterisation of Salmonella strains by an oligonucleotide multiprobe microarray. Mol Cell Probes 2006; 21:56-65. [PMID: 17029709 DOI: 10.1016/j.mcp.2006.08.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2006] [Revised: 07/26/2006] [Accepted: 08/03/2006] [Indexed: 10/24/2022]
Abstract
A DNA microarray has been developed for the simultaneous characterisation and typing of Salmonella enterica subsp. enterica isolates. One-hundred and nine 35-40 mer oligonucleotides probes detect flagellar and somatic antigen encoding genes (serogroup or serotype specific), important virulence genes located within or outside the pathogenicity islands, phage-associated genes and antibiotic resistance determinants. The probes were printed on glass slides and whole genomic Cy5-labelled Salmonella DNA was hybridised to the substrate. A set of 19 different Salmonella strains and one Escherichia coli strain has been selected as positive and negative controls for each probe. The validity of the results is confirmed by gene-specific PCRs or phenotypic methods (serotyping, MIC determination for various antimicrobial agents). Of 2071 data points generated, an agreement of 97.4% has been obtained between microarray and PCR/phenotypic results. Twenty-six data points (1.3%) were classified as uncertain and, similarly, 1.3% showed a discordant result. The microarray described here is a new tool to study the epidemiology of Salmonella strains on the genotypic level and might become a powerful method in risk assessment studies.
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Affiliation(s)
- Burkhard Malorny
- National Salmonella Reference Laboratory, Federal Institute for Risk Assessment, Diedersdorfer Weg 1, D-12277 Berlin, Germany
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Loh KD, Gyaneshwar P, Markenscoff Papadimitriou E, Fong R, Kim KS, Parales R, Zhou Z, Inwood W, Kustu S. A previously undescribed pathway for pyrimidine catabolism. Proc Natl Acad Sci U S A 2006; 103:5114-9. [PMID: 16540542 PMCID: PMC1458803 DOI: 10.1073/pnas.0600521103] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The b1012 operon of Escherichia coli K-12, which is composed of seven unidentified ORFs, is one of the most highly expressed operons under control of nitrogen regulatory protein C. Examination of strains with lesions in this operon on Biolog Phenotype MicroArray (PM3) plates and subsequent growth tests indicated that they failed to use uridine or uracil as the sole nitrogen source and that the parental strain could use them at room temperature but not at 37 degrees C. A strain carrying an ntrB(Con) mutation, which elevates transcription of genes under nitrogen regulatory protein C control, could also grow on thymidine as the sole nitrogen source, whereas strains with lesions in the b1012 operon could not. Growth-yield experiments indicated that both nitrogens of uridine and thymidine were available. Studies with [(14)C]uridine indicated that a three-carbon waste product from the pyrimidine ring was excreted. After trimethylsilylation and gas chromatography, the waste product was identified by mass spectrometry as 3-hydroxypropionic acid. In agreement with this finding, 2-methyl-3-hydroxypropionic acid was released from thymidine. Both the number of available nitrogens and the waste products distinguished the pathway encoded by the b1012 operon from pyrimidine catabolic pathways described previously. We propose that the genes of this operon be named rutA-G for pyrimidine utilization. The product of the divergently transcribed gene, b1013, is a tetracycline repressor family regulator that controls transcription of the b1012 operon negatively.
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Affiliation(s)
- Kevin D. Loh
- *Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, CA 94720-3102
| | - Prasad Gyaneshwar
- *Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, CA 94720-3102
| | | | - Rebecca Fong
- *Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, CA 94720-3102
| | - Kwang-Seo Kim
- *Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, CA 94720-3102
| | - Rebecca Parales
- Section of Microbiology, 1 Shields Avenue, University of California, Davis, CA 95616; and
| | - Zhongrui Zhou
- College of Chemistry, 8 Lewis Hall, University of California, Berkeley, CA 94720-1460
| | - William Inwood
- *Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, CA 94720-3102
| | - Sydney Kustu
- *Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, CA 94720-3102
- **To whom correspondence should be addressed. E-mail:
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Suzuki N, Nonaka H, Tsuge Y, Inui M, Yukawa H. New multiple-deletion method for the Corynebacterium glutamicum genome, using a mutant lox sequence. Appl Environ Microbiol 2006; 71:8472-80. [PMID: 16332837 PMCID: PMC1317446 DOI: 10.1128/aem.71.12.8472-8480.2005] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Due to the difficulty of multiple deletions using the Cre/loxP system, a simple, markerless multiple-deletion method based on a Cre/mutant lox system combining a right-element (RE) mutant lox site with a left-element (LE) mutant lox site was employed for large-scale genome rearrangements in Corynebacterium glutamicum. Eight distinct genomic regions that had been identified previously by comparative analysis of C. glutamicum R and C. glutamicum 13032 genomes were targeted for deletion. By homologous recombination, LE and RE mutant lox sites were integrated at each end of a target region. Highly efficient and accurate deletions between the two chromosomal mutant lox sites in the presence of Cre recombinase were realized. A deletion mutant lacking 190 kb of chromosomal regions, encoding a total of 188 open reading frames (ORFs), was obtained. These deletions represent the largest genomic excisions in C. glutamicum reported to date. Despite the loss of numerous predicted ORFs, the mutant exhibited normal growth under standard laboratory conditions. The Cre/loxP system using a pair of mutant lox sites provides a new, efficient genome rearrangement technique for C. glutamicum. It should facilitate the understanding of genome functions of microorganisms.
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Affiliation(s)
- Nobuaki Suzuki
- Microbiology Research Group, Research Institute of Innovative Technology for the Earth (RITE), 9-2, Kizugawadai, Kizu-Cho, Soraku-Gun, Kyoto 619-0292, Japan
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Suzuki N, Nonaka H, Tsuge Y, Okayama S, Inui M, Yukawa H. Multiple large segment deletion method for Corynebacterium glutamicum. Appl Microbiol Biotechnol 2005; 69:151-61. [PMID: 15843930 DOI: 10.1007/s00253-005-1976-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2005] [Revised: 03/18/2005] [Accepted: 03/22/2005] [Indexed: 10/25/2022]
Abstract
A precise and scarless genome excision method, employing the Cre/loxP system in concert with double-strand break (DSB)-stimulated intramolecular recombination was developed. The DSBs were mediated by the restriction endonuclease, I-SceI. It permitted multiple deletions of independent 14-, 43-, and 10-kb-long genomic regions on the Corynebacterium glutamicum genome. Accuracy of deletion was confirmed by the loss of marker genes, PCR, and sequencing of new genome joints. Eleven, 58, and 4 genes were predicted on the 14-, 43-, and 10-kb deleted regions, respectively. Although the resultant mutant lost a total of 67 kb encoding 73 genes, it still exhibited normal growth under standard laboratory conditions. Such a large segment deletion method in which multiple, successive deletions are possible is useful for genome engineering.
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Affiliation(s)
- Nobuaki Suzuki
- Microbiology Research Group, Research Institute of Innovative Technology for the Earth (RITE), Kizugawadai, Kizu-Cho, Soraku-Gun, Kyoto, Japan
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Suzuki N, Okayama S, Nonaka H, Tsuge Y, Inui M, Yukawa H. Large-scale engineering of the Corynebacterium glutamicum genome. Appl Environ Microbiol 2005; 71:3369-72. [PMID: 15933044 PMCID: PMC1151864 DOI: 10.1128/aem.71.6.3369-3372.2005] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The engineering of Corynebacterium glutamicum is important for enhanced production of biochemicals. To construct an improved C. glutamicum genome, we developed a precise genome excision method based on the Cre/loxP recombination system and successfully deleted 11 distinct genomic regions identified by comparative analysis of C. glutamicum genomes. Despite the loss of several predicted open reading frames, the mutant cells exhibited normal growth under standard laboratory conditions. With a total of 250 kb (7.5% of the genome), the 11 genomic regions were loaded with cryptic prophages, transposons, and genes of unknown function which were dispensable for cell growth, indicating recent horizontal acquisitions to the genome. This provides an interesting background for functional genomic studies and can be used in the improvement of cell traits.
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Affiliation(s)
- Nobuaki Suzuki
- Microbiology Research Group, Research Institute of Innovative Technology for Earth (RITE), 9-2, Kizugawadai, Kizu-Cho, Soraku-Gun, Kyoto 619-0292, Japan
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Ochman H, Santos SR. Exploring microbial microevolution with microarrays. INFECTION GENETICS AND EVOLUTION 2005; 5:103-8. [PMID: 15639741 DOI: 10.1016/j.meegid.2004.09.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2004] [Revised: 09/01/2004] [Accepted: 09/02/2004] [Indexed: 10/26/2022]
Abstract
Gene arrays are typically employed to monitor gene expression and regulation, but they are finding additional applications in studying patterns of evolution in bacterial genomes. In particular, this approach has been applied to answer questions about the heterogeneity in full gene repertoires among bacterial strains and species without relying on more costly and time-consuming methodologies. In this review, we evaluate some of the evolutionary patterns and processes affecting bacterial genomes as detected with microarrays, and also delineate the limitations and conclusions stemming from such studies.
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Affiliation(s)
- Howard Ochman
- Department of Biochemistry and Molecular Biophysics, University of Arizona, Tucson, AZ 85721, USA.
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Ren CP, Beatson SA, Parkhill J, Pallen MJ. The Flag-2 locus, an ancestral gene cluster, is potentially associated with a novel flagellar system from Escherichia coli. J Bacteriol 2005; 187:1430-40. [PMID: 15687208 PMCID: PMC545627 DOI: 10.1128/jb.187.4.1430-1440.2005] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Escherichia coli K-12 possesses two adjacent, divergent, promoterless flagellar genes, fhiA-mbhA, that are absent from Salmonella enterica. Through bioinformatics analysis, we found that these genes are remnants of an ancestral 44-gene cluster and are capable of encoding a novel flagellar system, Flag-2. In enteroaggregative E. coli strain 042, there is a frameshift in lfgC that is likely to have inactivated the system in this strain. Tiling path PCR studies showed that the Flag-2 cluster is present in 15 of 72 of the well-characterized ECOR strains. The Flag-2 system resembles the lateral flagellar systems of Aeromonas and Vibrio, particularly in its apparent dependence on RpoN. Unlike the conventional Flag-1 flagellin, the Flag-2 flagellin shows a remarkable lack of sequence polymorphism. The Flag-2 gene cluster encodes a flagellar type III secretion system (including a dedicated flagellar sigma-antisigma combination), thus raising the number of distinct type III secretion systems in Escherichia/Shigella to five. The presence of the Flag-2 cluster at identical sites in E. coli and its close relative Citrobacter rodentium, combined with its absence from S. enterica, suggests that it was acquired by horizontal gene transfer after the former two species diverged from Salmonella. The presence of Flag-2-like gene clusters in Yersinia pestis, Yersinia pseudotuberculosis, and Chromobacterium violaceum suggests that coexistence of two flagellar systems within the same species is more common than previously suspected. The fact that the Flag-2 gene cluster was not discovered in the first 10 Escherichia/Shigella genome sequences studied emphasizes the importance of maintaining an energetic program of genome sequencing for this important taxonomic group.
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Affiliation(s)
- Chuan-Peng Ren
- Bacterial Pathogenesis and Genomics Unit, Division of Immunity and Infection, Medical School, University of Birmingham, Birmingham, England B15 2TT
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50
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Washietl S, Hofacker IL, Stadler PF. Fast and reliable prediction of noncoding RNAs. Proc Natl Acad Sci U S A 2005; 102:2454-9. [PMID: 15665081 PMCID: PMC548974 DOI: 10.1073/pnas.0409169102] [Citation(s) in RCA: 520] [Impact Index Per Article: 27.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2004] [Indexed: 01/22/2023] Open
Abstract
We report an efficient method for detecting functional RNAs. The approach, which combines comparative sequence analysis and structure prediction, already has yielded excellent results for a small number of aligned sequences and is suitable for large-scale genomic screens. It consists of two basic components: (i) a measure for RNA secondary structure conservation based on computing a consensus secondary structure, and (ii) a measure for thermodynamic stability, which, in the spirit of a z score, is normalized with respect to both sequence length and base composition but can be calculated without sampling from shuffled sequences. Functional RNA secondary structures can be identified in multiple sequence alignments with high sensitivity and high specificity. We demonstrate that this approach is not only much more accurate than previous methods but also significantly faster. The method is implemented in the program rnaz, which can be downloaded from www.tbi.univie.ac.at/~wash/RNAz. We screened all alignments of length n > or = 50 in the Comparative Regulatory Genomics database, which compiles conserved noncoding elements in upstream regions of orthologous genes from human, mouse, rat, Fugu, and zebrafish. We recovered all of the known noncoding RNAs and cis-acting elements with high significance and found compelling evidence for many other conserved RNA secondary structures not described so far to our knowledge.
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Affiliation(s)
- Stefan Washietl
- Department of Theoretical Chemistry and Structural Biology, University of Vienna, Währingerstrasse 17, A-1090 Wien, Austria
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