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Li M, Carpenter CE, Broadbent JR. Organic Acid Exposure Enhances Virulence in Some Listeria monocytogenes Strains Using the Galleria mellonella Infection Model. Front Microbiol 2021; 12:675241. [PMID: 34295317 PMCID: PMC8290484 DOI: 10.3389/fmicb.2021.675241] [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: 03/02/2021] [Accepted: 06/14/2021] [Indexed: 01/01/2023] Open
Abstract
Prior research has suggested that the use of organic acids in the food industry may unintentionally enhance pathogenicity of Listeria monocytogenes strain N1-227 and R2-499. This study explored the connection between habituation to L-lactic acid or acetic acid and virulence in L. monocytogenes strains N1-227 and R2-499 using selected gene expression analysis and the in vivo Galleria mellonella wax worm model for infection. Expression of transcription factors (sigB and prfA) and genes related to acid resistance (gadD2, gadD3, and arcA) and bile resistance (bsh and bilE) or to virulence (inlA, inlB, hly, plcA, plcB, uhpT, and actA) was investigated by quantitative real-time PCR (qRT-PCR), while in vivo virulence was assessed by following the lethal time to 50% population mortality (LT50) of G. mellonella larvae after injection of untreated and habituated L. monocytogenes. Twenty minutes of habituation to the organic acids at pH 6.0 significantly increased expression of key acid and bile stress response genes in both strains, while expression of virulence genes was strain-dependent. The expression of transcription factor sigB was strain-dependent and there was no significant change in the expression of transcription factor prfA in both strains. Habituation to acid increased virulence of both strains as evidenced by decreased LT50 of G. mellonella larvae injected with Listeria habituated to either acid. In summary, habituation of both L. monocytogenes strains to organic acids up-regulated expression of several stress and virulence genes and concurrently increased virulence as measured using the G. mellonella model.
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Affiliation(s)
- Minghao Li
- Department of Nutrition, Dietetics and Food Sciences, Utah State University, Logan, UT, United States
| | - Charles E Carpenter
- Department of Nutrition, Dietetics and Food Sciences, Utah State University, Logan, UT, United States
| | - Jeff R Broadbent
- Department of Nutrition, Dietetics and Food Sciences, Utah State University, Logan, UT, United States
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Hapeshi A, Healey JRJ, Mulley G, Waterfield NR. Temperature Restriction in Entomopathogenic Bacteria. Front Microbiol 2020; 11:548800. [PMID: 33101227 PMCID: PMC7554251 DOI: 10.3389/fmicb.2020.548800] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Accepted: 09/08/2020] [Indexed: 11/21/2022] Open
Abstract
Temperature plays an important role in bacteria-host interactions and can be a determining factor for host switching. In this study we sought to investigate the reasons behind growth temperature restriction in the entomopathogenic enterobacterium Photorhabdus. Photorhabdus has a complex dual symbiotic and pathogenic life cycle. The genus consists of 19 species but only one subgroup, previously all classed together as Photorhabdus asymbiotica, have been shown to cause human disease. These clinical isolates necessarily need to be able to grow at 37°C, whilst the remaining species are largely restricted to growth temperatures below 34°C and are therefore unable to infect mammalian hosts. Here, we have isolated spontaneous mutant lines of Photorhabdus laumondii DJC that were able to grow up to 36-37°C. Following whole genome sequencing of 29 of these mutants we identified a single gene, encoding a protein with a RecG-like helicase domain that for the majority of isolates contained single nucleotide polymorphisms. Importantly, provision of the wild-type allele of this gene in trans restored the temperature restriction, confirming the mutations are recessive, and the dominant effect of the protein product of this gene. The gene appears to be part of a short three cistron operon, which we have termed the Temperature Restricting Locus (TRL). Transcription reporter strains revealed that this operon is induced upon the switch from 30 to 36°C, leading to replication arrest of the bacteria. TRL is absent from all of the human pathogenic species so far examined, although its presence is not uniform in different strains of the Photorhabdus luminescens subgroup. In a wider context, the presence of this gene is not limited to Photorhabdus, being found in phylogenetically diverse proteobacteria. We therefore suggest that this system may play a more fundamental role in temperature restriction in diverse species, relating to as yet cryptic aspects of their ecological niches and life cycle requirements.
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Affiliation(s)
- Alexia Hapeshi
- Microbiology and Infection Unit, Warwick Medical School, The University of Warwick, Coventry, United Kingdom
| | - Joseph R. J. Healey
- Microbiology and Infection Unit, Warwick Medical School, The University of Warwick, Coventry, United Kingdom
| | - Geraldine Mulley
- School of Biological Sciences, University of Reading, Reading, United Kingdom
| | - Nicholas R. Waterfield
- Microbiology and Infection Unit, Warwick Medical School, The University of Warwick, Coventry, United Kingdom
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Cortés-Martínez CI, Chavarría-Hernández N. Production of entomopathogenic nematodes in submerged monoxenic culture: A review. Biotechnol Bioeng 2020; 117:3968-3985. [PMID: 32710642 DOI: 10.1002/bit.27515] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 07/15/2020] [Accepted: 07/16/2020] [Indexed: 01/29/2023]
Abstract
Monoxenic liquid culture is the most suitable technology for scaling up to industrial production of entomopathogenic nematodes (EPNs); however, the variability of the yield production remains a current problem in the process. The aim of this study was to analyze the parameters and criteria for EPN production in liquid culture based on scientific and technological knowledge from the last two decades. While experimental research has permitted the yield production of Heterorhabditis bacteriophora (362 × 103 infective juveniles [IJs]/ml) and Steinernema carpocapsae (252 × 103 IJs/ml), simultaneously, theoretical approaches have contributed to the understanding of the culture process, based on biological parameters of the bacterium-nematode complex and hydrodynamic and rheological parameters of the complex gas-liquid-solid system. Under this interdisciplinary research approach, bioprocess and biosystem engineering can contribute to design the various control strategies of the process variables, increase the productivity, and reduce the variability that until now distinguishes the in vitro production of EPNs by the liquid culture.
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Affiliation(s)
- Carlos Inocencio Cortés-Martínez
- Cuerpo Académico de Biotecnología Agroalimentaria, Instituto de Ciencias Agropecuarias, Universidad Autónoma del Estado de Hidalgo, Tulancingo de Bravo, Hidalgo, México
| | - Norberto Chavarría-Hernández
- Cuerpo Académico de Biotecnología Agroalimentaria, Instituto de Ciencias Agropecuarias, Universidad Autónoma del Estado de Hidalgo, Tulancingo de Bravo, Hidalgo, México
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Hapeshi A, Benarroch JM, Clarke DJ, Waterfield NR. Iso-propyl stilbene: a life cycle signal? MICROBIOLOGY-SGM 2019; 165:516-526. [PMID: 30882293 DOI: 10.1099/mic.0.000790] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Members of the Gram-negative bacterial genus Photorhabdus are all highly insect pathogenic and exist in an obligate symbiosis with the entomopathogenic nematode worm Heterorhabditis. All members of the genus produce the small-molecule 3,5-dihydroxy-4-isopropyl-trans-stilbene (IPS) as part of their secondary metabolism. IPS is a multi-potent compound that has antimicrobial, antifungal, immunomodulatory and anti-cancer activities and also plays an important role in symbiosis with the nematode. In this study we have examined the response of Photorhabdus itself to exogenous ectopic addition of IPS at physiologically relevant concentrations. We observed that the bacteria had a measureable phenotypic response, which included a decrease in bioluminescence and pigment production. This was reflected in changes in its transcriptomic response, in which we reveal a reduction in transcript levels of genes relating to many fundamental cellular processes, such as translation and oxidative phosphorylation. Our observations suggest that IPS plays an important role in the biology of Photorhabdus bacteria, fulfilling roles in quorum sensing, antibiotic-competition advantage and maintenance of the symbiotic developmental cycle.
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Affiliation(s)
- Alexia Hapeshi
- Microbiology and Infection Unit, Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, UK
| | - Jonatan Mimon Benarroch
- Microbiology and Infection Unit, Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, UK
| | - David James Clarke
- School of Microbiology and APC Microbiome Ireland, University College Cork, Cork, Ireland
| | - Nicholas Robin Waterfield
- Microbiology and Infection Unit, Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, UK
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Mulley G, Beeton ML, Wilkinson P, Vlisidou I, Ockendon-Powell N, Hapeshi A, Tobias NJ, Nollmann FI, Bode HB, van den Elsen J, ffrench-Constant RH, Waterfield NR. From Insect to Man: Photorhabdus Sheds Light on the Emergence of Human Pathogenicity. PLoS One 2015; 10:e0144937. [PMID: 26681201 PMCID: PMC4683029 DOI: 10.1371/journal.pone.0144937] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 11/25/2015] [Indexed: 12/27/2022] Open
Abstract
Photorhabdus are highly effective insect pathogenic bacteria that exist in a mutualistic relationship with Heterorhabditid nematodes. Unlike other members of the genus, Photorhabdus asymbiotica can also infect humans. Most Photorhabdus cannot replicate above 34°C, limiting their host-range to poikilothermic invertebrates. In contrast, P. asymbiotica must necessarily be able to replicate at 37°C or above. Many well-studied mammalian pathogens use the elevated temperature of their host as a signal to regulate the necessary changes in gene expression required for infection. Here we use RNA-seq, proteomics and phenotype microarrays to examine temperature dependent differences in transcription, translation and phenotype of P. asymbiotica at 28°C versus 37°C, relevant to the insect or human hosts respectively. Our findings reveal relatively few temperature dependant differences in gene expression. There is however a striking difference in metabolism at 37°C, with a significant reduction in the range of carbon and nitrogen sources that otherwise support respiration at 28°C. We propose that the key adaptation that enables P. asymbiotica to infect humans is to aggressively acquire amino acids, peptides and other nutrients from the human host, employing a so called “nutritional virulence” strategy. This would simultaneously cripple the host immune response while providing nutrients sufficient for reproduction. This might explain the severity of ulcerated lesions observed in clinical cases of Photorhabdosis. Furthermore, while P. asymbiotica can invade mammalian cells they must also resist immediate killing by humoral immunity components in serum. We observed an increase in the production of the insect Phenol-oxidase inhibitor Rhabduscin normally deployed to inhibit the melanisation immune cascade. Crucially we demonstrated this molecule also facilitates protection against killing by the alternative human complement pathway.
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Affiliation(s)
- Geraldine Mulley
- School of Biological Sciences, University of Reading, Whiteknights, Reading, RG6 6AJ, United Kingdom
| | - Michael L Beeton
- Cardiff School of Health Sciences, Cardiff Metropolitan University, Llandaff Campus, Western Avenue, Cardiff, CF5 2YB, United Kingdom
| | - Paul Wilkinson
- Life Sciences Building, Bristol University, 24 Tyndall Avenue, Bristol, BS8 1TQ, United Kingdom
| | - Isabella Vlisidou
- Life Sciences Building, Bristol University, 24 Tyndall Avenue, Bristol, BS8 1TQ, United Kingdom
| | - Nina Ockendon-Powell
- Primary Care Unit, Microbiology Department, Public Health England, Gloucester Royal Hospital, Great Western Road, Gloucester, GL1 3NN, United Kingdom
| | - Alexia Hapeshi
- Division of Biomedical Sciences, Warwick Medical School, Medical School Building, The University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom
| | - Nick J Tobias
- Buchmann Center for Life Sciences (BMLS), Fachbereich Biowissenschaften, Goethe Universität Frankfurt, 60438, Frankfurt, Germany
| | - Friederike I Nollmann
- Buchmann Center for Life Sciences (BMLS), Fachbereich Biowissenschaften, Goethe Universität Frankfurt, 60438, Frankfurt, Germany
| | - Helge B Bode
- Buchmann Center for Life Sciences (BMLS), Fachbereich Biowissenschaften, Goethe Universität Frankfurt, 60438, Frankfurt, Germany
| | - Jean van den Elsen
- Department of Biology & Biochemistry, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom
| | | | - Nicholas R Waterfield
- Division of Biomedical Sciences, Warwick Medical School, Medical School Building, The University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom
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Abstract
It is well recognized that bacteria communicate via small diffusible molecules, a process termed quorum sensing. The best understood quorum sensing systems are those that use acylated homoserine lactones (AHLs) for communication. The prototype of those systems consists of a LuxI-like AHL synthase and a cognate LuxR receptor that detects the signal. However, many proteobacteria possess LuxR receptors, yet lack any LuxI-type synthase, and thus these receptors are referred to as LuxR orphans or solos. In addition to the well-known AHLs, little is known about the signaling molecules that are sensed by LuxR solos. Here, we describe a novel cell-cell communication system in the insect and human pathogen Photorhabdus asymbiotica. We identified the LuxR homolog PauR to sense dialkylresorcinols (DARs) and cyclohexanediones (CHDs) instead of AHLs as signals. The DarABC synthesis pathway produces the molecules, and the entire system emerged as important for virulence. Moreover, we have analyzed more than 90 different Photorhabdus strains by HPLC/MS and showed that these DARs and CHDs are specific to the human pathogen P. asymbiotica. On the basis of genomic evidence, 116 other bacterial species are putative DAR producers, among them many human pathogens. Therefore, we discuss the possibility of DARs as novel and widespread bacterial signaling molecules and show that bacterial cell-cell communication goes far beyond AHL signaling in nature.
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Kelker MS, Berry C, Evans SL, Pai R, McCaskill DG, Wang NX, Russell JC, Baker MD, Yang C, Pflugrath JW, Wade M, Wess TJ, Narva KE. Structural and biophysical characterization of Bacillus thuringiensis insecticidal proteins Cry34Ab1 and Cry35Ab1. PLoS One 2014; 9:e112555. [PMID: 25390338 PMCID: PMC4229197 DOI: 10.1371/journal.pone.0112555] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Accepted: 10/07/2014] [Indexed: 11/18/2022] Open
Abstract
Bacillus thuringiensis strains are well known for the production of insecticidal proteins upon sporulation and these proteins are deposited in parasporal crystalline inclusions. The majority of these insect-specific toxins exhibit three domains in the mature toxin sequence. However, other Cry toxins are structurally and evolutionarily unrelated to this three-domain family and little is known of their three dimensional structures, limiting our understanding of their mechanisms of action and our ability to engineer the proteins to enhance their function. Among the non-three domain Cry toxins, the Cry34Ab1 and Cry35Ab1 proteins from B. thuringiensis strain PS149B1 are required to act together to produce toxicity to the western corn rootworm (WCR) Diabrotica virgifera virgifera Le Conte via a pore forming mechanism of action. Cry34Ab1 is a protein of ∼14 kDa with features of the aegerolysin family (Pfam06355) of proteins that have known membrane disrupting activity, while Cry35Ab1 is a ∼44 kDa member of the toxin_10 family (Pfam05431) that includes other insecticidal proteins such as the binary toxin BinA/BinB. The Cry34Ab1/Cry35Ab1 proteins represent an important seed trait technology having been developed as insect resistance traits in commercialized corn hybrids for control of WCR. The structures of Cry34Ab1 and Cry35Ab1 have been elucidated to 2.15 Å and 1.80 Å resolution, respectively. The solution structures of the toxins were further studied by small angle X-ray scattering and native electrospray ion mobility mass spectrometry. We present here the first published structure from the aegerolysin protein domain family and the structural comparisons of Cry34Ab1 and Cry35Ab1 with other pore forming toxins.
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Affiliation(s)
- Matthew S. Kelker
- Dow AgroSciences, LLC, Indianapolis, Indiana, United States of America
| | - Colin Berry
- Cardiff School of Biosciences, Cardiff University, Cardiff, Wales, United Kingdom
| | - Steven L. Evans
- Dow AgroSciences, LLC, Indianapolis, Indiana, United States of America
| | - Reetal Pai
- Dow AgroSciences, LLC, Indianapolis, Indiana, United States of America
| | | | - Nick X. Wang
- Dow AgroSciences, LLC, Indianapolis, Indiana, United States of America
| | - Joshua C. Russell
- Dow AgroSciences, LLC, Indianapolis, Indiana, United States of America
| | - Matthew D. Baker
- Cardiff School of Biosciences, Cardiff University, Cardiff, Wales, United Kingdom
| | - Cheng Yang
- Rigaku Americas Corporation, The Woodlands, Texas, United States of America
| | - J. W. Pflugrath
- Rigaku Americas Corporation, The Woodlands, Texas, United States of America
| | - Matthew Wade
- School of Optometry & Vision Sciences, Cardiff University, Cardiff, Wales, United Kingdom
| | - Tim J. Wess
- School of Optometry & Vision Sciences, Cardiff University, Cardiff, Wales, United Kingdom
| | - Kenneth E. Narva
- Dow AgroSciences, LLC, Indianapolis, Indiana, United States of America
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Ramarao N, Nielsen-Leroux C, Lereclus D. The insect Galleria mellonella as a powerful infection model to investigate bacterial pathogenesis. J Vis Exp 2012:e4392. [PMID: 23271509 DOI: 10.3791/4392] [Citation(s) in RCA: 164] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The study of bacterial virulence often requires a suitable animal model. Mammalian models of infection are costly and may raise ethical issues. The use of insects as infection models provides a valuable alternative. Compared to other non-vertebrate model hosts such as nematodes, insects have a relatively advanced system of antimicrobial defenses and are thus more likely to produce information relevant to the mammalian infection process. Like mammals, insects possess a complex innate immune system(1). Cells in the hemolymph are capable of phagocytosing or encapsulating microbial invaders, and humoral responses include the inducible production of lysozyme and small antibacterial peptides(2,3). In addition, analogies are found between the epithelial cells of insect larval midguts and intestinal cells of mammalian digestive systems. Finally, several basic components essential for the bacterial infection process such as cell adhesion, resistance to antimicrobial peptides, tissue degradation and adaptation to oxidative stress are likely to be important in both insects and mammals(1). Thus, insects are polyvalent tools for the identification and characterization of microbial virulence factors involved in mammalian infections. Larvae of the greater wax moth Galleria mellonella have been shown to provide a useful insight into the pathogenesis of a wide range of microbial infections including mammalian fungal (Fusarium oxysporum, Aspergillus fumigatus, Candida albicans) and bacterial pathogens, such as Staphylococcus aureus, Proteus vulgaris, Serratia marcescens Pseudomonas aeruginosa, Listeria monocytogenes or Enterococcus faecalis(4-7). Regardless of the bacterial species, results obtained with Galleria larvae infected by direct injection through the cuticle consistently correlate with those of similar mammalian studies: bacterial strains that are attenuated in mammalian models demonstrate lower virulence in Galleria, and strains causing severe human infections are also highly virulent in the Galleria model(8-11). Oral infection of Galleria is much less used and additional compounds, like specific toxins, are needed to reach mortality. G. mellonella larvae present several technical advantages: they are relatively large (last instar larvae before pupation are about 2 cm long and weight 250 mg), thus enabling the injection of defined doses of bacteria; they can be reared at various temperatures (20 °C to 30 °C) and infection studies can be conducted between 15 °C to above 37 °C(12,13), allowing experiments that mimic a mammalian environment. In addition, insect rearing is easy and relatively cheap. Infection of the larvae allows monitoring bacterial virulence by several means, including calculation of LD50(14), measurement of bacterial survival(15,16) and examination of the infection process(17). Here, we describe the rearing of the insects, covering all life stages of G. mellonella. We provide a detailed protocol of infection by two routes of inoculation: oral and intra haemocoelic. The bacterial model used in this protocol is Bacillus cereus, a Gram positive pathogen implicated in gastrointestinal as well as in other severe local or systemic opportunistic infections(18,19).
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Influence of the Photorhabdus luminescens phosphomannose isomerase gene, manA, on mannose utilization, exopolysaccharide structure, and biofilm formation. Appl Environ Microbiol 2010; 77:776-85. [PMID: 21148694 DOI: 10.1128/aem.02326-10] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Extracellular polysaccharide (EPS) is produced by diverse bacterial pathogens and fulfills assorted roles, including providing a structural matrix for biofilm formation and more specific functions in virulence, such as protection against immune defenses. We report here the first investigation of some of the genes important for biofilm formation in Photorhabdus luminescens and demonstrate the key role of the phosphomannose isomerase gene, manA, in the structure of functional EPS. Phenotypic analyses of a manA-deficient mutant showed the importance of EPS in motility, insect virulence, and biofilm formation on abiotic surfaces as well as the requirement of this gene for the use of mannose as the sole carbon source. Conversely, this defect had no apparent impact on symbiosis with the heterorhabditid nematode vector. A more detailed analysis of biofilm formation revealed that the manA mutant was able to attach to surfaces with the same efficiency as that of the wild-type strain but could not develop the more extended biofilm matrix structures. A compositional analysis of P. luminescens EPS reveals how the manA mutation has a major effect on the formation of a complete, branched EPS.
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