1
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Zayabaatar E, Tang NMT, Pham MT. Electrogenic Staphylococcus epidermidis colonizes nasal cavities and alleviates IL-6 progression induced by the SARS2-CoV nucleocapsid protein. J Appl Microbiol 2023; 134:lxad179. [PMID: 37558389 DOI: 10.1093/jambio/lxad179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 07/29/2023] [Accepted: 08/08/2023] [Indexed: 08/11/2023]
Abstract
AIM Certain probiotic bacteria have been shown to possess an immunomodulatory effect and a protective effect on influenza infections. Using the Staphylococcus epidermidis K1 colonized mice model, we assessed the effect of nasal administration of glycerol or flavin mononucleotide (FMN) on the production of interleukin (IL)-6 mediated by the severe acute respiratory syndrome coronavirus 2 (SARS2-CoV) nucleocapsid protein (NPP). METHODS AND RESULTS FMN, one of the key electron donors for the generation of electricity facilitated by S. epidermidis ATCC 12228, was detected in the glycerol fermentation medium. Compared to the S. epidermidis ATCC 12228, the S. epidermidis K1 isolate showed significant expression of the electron transfer genes, including pyruvate dehydrogenase (pdh), riboflavin kinase (rk), 1,4-dihydroxy-2-naphthoate octaprenyltransferase (menA), and type II NADH quinone oxidoreductase (ndh2). Institute of cancer research (ICR) mice were intranasally administered with S. epidermidis K1 with or without pretreatment with riboflavin kinase inhibitors, then nasally treated with glycerol or FMN before inoculating the NPP. Furthermore, J774A.1 macrophages were exposed to NPP serum and then treated with NPP of SARS2-CoV. The IL-6 levels in the bronchoalveolar lavage fluid (BALF) of mice and macrophages were quantified using a mouse IL-6 enzyme-linked immunosorbent assay kit. CONCLUSIONS Here, we report that nasal administration of NPP strongly elevates IL-6 levels in both BALF and J774A.1 macrophages. It is worth noting that NPP-neutralizing antibodies can decrease IL-6 levels in macrophages. The nasal administration of glycerol or FMN to S. epidermidis K1-colonized mice results in a reduction of NPP-induced IL-6 production.
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Affiliation(s)
- Enkhbat Zayabaatar
- Department of Biomedical Sciences and Engineering, National Central University, Taoyuan 320317, Taiwan
| | - Nguyen Mai Trinh Tang
- Department of Biomedical Sciences and Engineering, National Central University, Taoyuan 320317, Taiwan
| | - Minh Tan Pham
- Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City 700000, Vietnam
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2
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Kabongo AT, Acharjee R, Sakura T, Bundutidi GM, Hartuti ED, Davies C, Gundogdu O, Kita K, Shiba T, Inaoka DK. Biochemical characterization and identification of ferulenol and embelin as potent inhibitors of malate:quinone oxidoreductase from Campylobacter jejuni. Front Mol Biosci 2023; 10:1095026. [PMID: 36776743 PMCID: PMC9908594 DOI: 10.3389/fmolb.2023.1095026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 01/18/2023] [Indexed: 01/27/2023] Open
Abstract
Campylobacter jejuni infection poses a serious global threat to public health. The increasing incidence and antibiotic resistance of this bacterial infection have necessitated the adoption of various strategies to curb this trend, primarily through developing new drugs with new mechanisms of action. The enzyme malate:quinone oxidoreductase (MQO) has been shown to be essential for the survival of several bacteria and parasites. MQO is a peripheral membrane protein that catalyses the oxidation of malate to oxaloacetate, a crucial step in the tricarboxylic acid cycle. In addition, MQO is involved in the reduction of the quinone pool in the electron transport chain and thus contributes to cellular bioenergetics. The enzyme is an attractive drug target as it is not conserved in mammals. As a preliminary step in assessing the potential application of MQO from C. jejuni (CjMQO) as a new drug target, we purified active recombinant CjMQO and conducted, for the first time, biochemical analyses of MQO from a pathogenic bacterium. Our study showed that ferulenol, a submicromolar mitochondrial MQO inhibitor, and embelin are nanomolar inhibitors of CjMQO. We showed that both inhibitors are mixed-type inhibitors versus malate and noncompetitive versus quinone, suggesting the existence of a third binding site to accommodate these inhibitors; indeed, such a trait appears to be conserved between mitochondrial and bacterial MQOs. Interestingly, ferulenol and embelin also inhibit the in vitro growth of C. jejuni, supporting the hypothesis that MQO is essential for C. jejuni survival and is therefore an important drug target.
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Affiliation(s)
- Augustin Tshibaka Kabongo
- School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, Japan,Department of Molecular Infection Dynamics, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan,Department of Internal Medicine, Faculty of Medicine, Pharmacy and Public Health, University of Mbujimayi, Kinshasa, Congo
| | - Rajib Acharjee
- Department of Parasitology, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan,Program for Nurturing Global Leaders in Tropical and Emerging Communicable Disease, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan,Department of Zoology, University of Chittagong, Chittagong, Bangladesh
| | - Takaya Sakura
- School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, Japan,Department of Molecular Infection Dynamics, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan
| | - Gloria Mavinga Bundutidi
- Department of Molecular Infection Dynamics, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan,Department of Parasitology, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan,Program for Nurturing Global Leaders in Tropical and Emerging Communicable Disease, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan,Department of Pediatrics, Kinshasa University Hospital, University of Kinshasa, Kinshasa, Congo
| | - Endah Dwi Hartuti
- Department of Parasitology, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan,Program for Nurturing Global Leaders in Tropical and Emerging Communicable Disease, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan,Research Center for Genetic Engineering, National Research and Innovation Agency, West Java, Indonesia
| | - Cadi Davies
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Ozan Gundogdu
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Kiyoshi Kita
- School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, Japan,Department of Host-Defense Biochemistry, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan,Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Tomoo Shiba
- Department of Applied Biology, Graduate School of Science and Technology, Kyoto Institute of Technology, Kyoto, Japan,*Correspondence: Tomoo Shiba, ; Daniel Ken Inaoka,
| | - Daniel Ken Inaoka
- School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, Japan,Department of Molecular Infection Dynamics, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan,Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan,*Correspondence: Tomoo Shiba, ; Daniel Ken Inaoka,
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3
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Stoakes E, Savva GM, Coates R, Tejera N, Poolman MG, Grant AJ, Wain J, Singh D. Substrate Utilisation and Energy Metabolism in Non-Growing Campylobacter jejuni M1cam. Microorganisms 2022; 10:microorganisms10071355. [PMID: 35889074 PMCID: PMC9318392 DOI: 10.3390/microorganisms10071355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 06/23/2022] [Accepted: 06/30/2022] [Indexed: 02/04/2023] Open
Abstract
Campylobacter jejuni, the major cause of bacterial foodborne illness, is also a fastidious organism that requires strict growth requirements in the laboratory. Our aim was to study substrate utilisation and energy metabolism in non-growing C. jejuni to investigate the ability of these bacteria to survive so effectively in the food chain. We integrated phenotypic microarrays and genome-scale metabolic modelling (GSM) to investigate the survival of C. jejuni on 95 substrates. We further investigated the underlying metabolic re-adjustment associated with varying energy demands on each substrate. We identified amino acids, organic acids and H2, as single substrates supporting survival without growth. We identified several different mechanisms, which were used alone or in combination, for ATP production: substrate-level phosphorylation via acetate kinase, the TCA cycle, and oxidative phosphorylation via the electron transport chain that utilised alternative electron donors and acceptors. The benefit of ATP production through each of these mechanisms was associated with the cost of enzyme investment, nutrient availability and/or O2 utilisation. C. jejuni can utilise a wide range of substrates as energy sources, including organic acids commonly used for marination or preservation of ingredients, which might contribute to the success of their survival in changing environments.
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Affiliation(s)
- Emily Stoakes
- Department of Veterinary Medicine, University of Cambridge, Cambridge CB3 0ES, UK; (E.S.); (R.C.); (A.J.G.)
| | - George M. Savva
- Quadram Institute Bioscience, Norwich Research Park, Norwich NR4 7UQ, UK; (G.M.S.); (N.T.)
| | - Ruby Coates
- Department of Veterinary Medicine, University of Cambridge, Cambridge CB3 0ES, UK; (E.S.); (R.C.); (A.J.G.)
| | - Noemi Tejera
- Quadram Institute Bioscience, Norwich Research Park, Norwich NR4 7UQ, UK; (G.M.S.); (N.T.)
| | - Mark G. Poolman
- Cell System Modelling Group, Oxford Brookes University, Oxford OX3 0BP, UK;
| | - Andrew J. Grant
- Department of Veterinary Medicine, University of Cambridge, Cambridge CB3 0ES, UK; (E.S.); (R.C.); (A.J.G.)
| | - John Wain
- Quadram Institute Bioscience, Norwich Research Park, Norwich NR4 7UQ, UK; (G.M.S.); (N.T.)
- Correspondence: (J.W.); (D.S.)
| | - Dipali Singh
- Quadram Institute Bioscience, Norwich Research Park, Norwich NR4 7UQ, UK; (G.M.S.); (N.T.)
- Correspondence: (J.W.); (D.S.)
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4
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Kao M, Yang J, Balasubramaniam A, Traisaeng S, Jackson Yang A, Yang JJ, Salamon BP, Herr DR, Huang C. Colonization of nasal cavities by
Staphylococcus epidermidis
mitigates SARS‐CoV‐2 nucleocapsid phosphoprotein‐induced interleukin (IL)‐6 in the lung. Microb Biotechnol 2022; 15:1984-1994. [PMID: 35426250 PMCID: PMC9111282 DOI: 10.1111/1751-7915.13994] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 11/19/2021] [Accepted: 12/02/2021] [Indexed: 11/27/2022] Open
Abstract
Infection by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) can trigger excessive interleukin (IL)‐6 signalling, leading to a myriad of biological effects including a cytokine storm that contributes to multiple organ failure in severe coronavirus disease 2019 (COVID‐19). Using a mouse model, we demonstrated that nasal inoculation of nucleocapsid phosphoprotein (NPP) of SARS‐CoV‐2 increased IL‐6 content in bronchoalveolar lavage fluid (BALF). Nasal administration of liquid coco‐caprylate/caprate (LCC) onto Staphylococcus epidermidis (S. epidermidis)‐colonized mice significantly attenuated NPP‐induced IL‐6. Furthermore, S. epidermidis‐mediated LCC fermentation to generate electricity and butyric acid that promoted bacterial colonization and activated free fatty acid receptor 2 (Ffar2) respectively. Inhibition of Ffar2 impeded the effect of S. epidermidis plus LCC on the reduction of NPP‐induced IL‐6. Collectively, these results suggest that nasal S. epidermidis is part of the first line of defence in ameliorating a cytokine storm induced by airway infection of SARS‐CoV‐2.
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Affiliation(s)
- Ming‐Shan Kao
- Department of Biomedical Sciences and Engineering National Central University Taoyuan 32001 Taiwan
| | - Jen‐Ho Yang
- Department of Biomedical Sciences and Engineering National Central University Taoyuan 32001 Taiwan
| | - Arun Balasubramaniam
- Department of Biomedical Sciences and Engineering National Central University Taoyuan 32001 Taiwan
| | | | - Albert Jackson Yang
- Department of Biomedical Sciences and Engineering National Central University Taoyuan 32001 Taiwan
| | - John Jackson Yang
- Department of Biomedical Sciences and Engineering National Central University Taoyuan 32001 Taiwan
| | | | - Deron R. Herr
- Department of Biology San Diego State University San Diego CA 92182 USA
| | - Chun‐Ming Huang
- Department of Biomedical Sciences and Engineering National Central University Taoyuan 32001 Taiwan
- Department of Biomedical Science and Environment Biology Kaohsiung Medical University Kaohsiung 80708 Taiwan
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5
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Khademi SMH, Gabrielaite M, Paulsson M, Knulst M, Touriki E, Marvig RL, Påhlman LI. Genomic and Phenotypic Evolution of Achromobacter xylosoxidans during Chronic Airway Infections of Patients with Cystic Fibrosis. mSystems 2021; 6:e0052321. [PMID: 34184916 PMCID: PMC8269239 DOI: 10.1128/msystems.00523-21] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 06/02/2021] [Indexed: 11/22/2022] Open
Abstract
Bacterial pathogens evolve during chronic colonization of the human host by selection for pathoadaptive mutations. One of the emerging and understudied bacterial species causing chronic airway infections in patients with cystic fibrosis (CF) is Achromobacter xylosoxidans. It can establish chronic infections in patients with CF, but the genetic and phenotypic changes associated with adaptation during these infections are not completely understood. In this study, we analyzed the whole-genome sequences of 55 clinical A. xylosoxidans isolates longitudinally collected from the sputum of 6 patients with CF. Four genes encoding regulatory proteins and two intergenic regions showed convergent evolution, likely driven by positive selection for pathoadaptive mutations, across the different clones of A. xylosoxidans. Most of the evolved isolates had lower swimming motility and were resistant to multiple classes of antibiotics, while fewer of the evolved isolates had slower growth or higher biofilm production than the first isolates. Using a genome-wide association study method, we identified several putative genetic determinants of biofilm formation, motility and β-lactam resistance in this pathogen. With respect to antibiotic resistance, we discovered that a combination of mutations in pathoadaptive genes (phoQ and bigR) and two other genes encoding regulatory proteins (spoT and cpxA) were associated with increased resistance to meropenem and ceftazidime. Altogether, our results suggest that genetic changes within regulatory loci facilitate within-host adaptation of A. xylosoxidans and the emergence of adaptive phenotypes, such as antibiotic resistance or biofilm formation. IMPORTANCE A thorough understanding of bacterial pathogen adaptation is essential for the treatment of chronic bacterial infections. One unique challenge in the analysis and interpretation of genomics data is identifying the functional impact of mutations accumulated in the bacterial genome during colonization in the human host. Here, we investigated the genomic and phenotypic evolution of A. xylosoxidans in chronic airway infections of patients with CF and identified several mutations associated with the phenotypic evolution of this pathogen using genome-wide associations. Identification of phenotypes under positive selection and the associated mutations can enlighten the adaptive processes of this emerging pathogen in human infections and pave the way for novel therapeutic interventions.
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Affiliation(s)
- S. M. Hossein Khademi
- Department of Clinical Sciences Lund, Division of Infection Medicine, Lund University, Lund, Sweden
| | | | - Magnus Paulsson
- Department of Clinical Sciences Lund, Division of Infection Medicine, Lund University, Lund, Sweden
- Division of Infectious Diseases, Skåne University Hospital Lund, Lund, Sweden
| | - Mattis Knulst
- Department of Clinical Sciences Lund, Division of Infection Medicine, Lund University, Lund, Sweden
| | - Eleni Touriki
- Clinical Microbiology, Labmedicin Skåne, Lund, Sweden
| | - Rasmus L. Marvig
- Center for Genomic Medicine, Rigshospitalet, Copenhagen, Denmark
| | - Lisa I. Påhlman
- Department of Clinical Sciences Lund, Division of Infection Medicine, Lund University, Lund, Sweden
- Division of Infectious Diseases, Skåne University Hospital Lund, Lund, Sweden
- Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
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6
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Alqurashi A, Alfs L, Swann J, Butt JN, Kelly DJ. The flavodoxin FldA activates the class Ia ribonucleotide reductase of Campylobacter jejuni. Mol Microbiol 2021; 116:343-358. [PMID: 33721378 DOI: 10.1111/mmi.14715] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 03/11/2021] [Indexed: 11/30/2022]
Abstract
Campylobacter jejuni is a microaerophilic zoonotic pathogen with an atypical respiratory Complex I that oxidizes a flavodoxin (FldA) instead of NADH. FldA is essential for viability and is reduced via pyruvate and 2-oxoglutarate oxidoreductases (POR/OOR). Here, we show that FldA can also be reduced by FqrB (Cj0559), an NADPH:FldA reductase. An fqrB deletion mutant was viable but displayed a significant growth defect. FqrB is related to flavoprotein reductases from Gram-positive bacteria that can reduce NrdI, a specialized flavodoxin that is needed for tyrosyl radical formation in NrdF, the beta subunit of class 1b-type (Mn) ribonucleotide reductase (RNR). However, C. jejuni possesses a single class Ia-type (Fe) RNR (NrdAB) that would be expected to be ferredoxin dependent. We show that CjFldA is an unusually high potential flavodoxin unrelated to NrdI, yet growth of the fqrB mutant, but not the wild-type or a complemented strain, was stimulated by low deoxyribonucleoside (dRNS) concentrations, suggesting FldA links FqrB and RNR activity. Using purified proteins, we confirmed the NrdB tyrosyl radical could be regenerated in an NADPH, FqrB, and FldA dependent manner, as evidenced by both optical and electron paramagnetic resonance (EPR) spectroscopy. Thus, FldA activates RNR in C. jejuni, partly explaining its essentiality.
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Affiliation(s)
- Abdulmajeed Alqurashi
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, UK
| | - Laura Alfs
- School of Chemistry, University of East Anglia, Norwich, UK
| | - Jordan Swann
- School of Chemistry, University of East Anglia, Norwich, UK
| | - Julea N Butt
- School of Chemistry, University of East Anglia, Norwich, UK
| | - David J Kelly
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, UK
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7
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Tejera N, Crossman L, Pearson B, Stoakes E, Nasher F, Djeghout B, Poolman M, Wain J, Singh D. Genome-Scale Metabolic Model Driven Design of a Defined Medium for Campylobacter jejuni M1cam. Front Microbiol 2020; 11:1072. [PMID: 32636809 PMCID: PMC7318876 DOI: 10.3389/fmicb.2020.01072] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 04/29/2020] [Indexed: 12/17/2022] Open
Abstract
Campylobacter jejuni, the most frequent cause of food-borne bacterial gastroenteritis, is a fastidious organism when grown in the laboratory. Oxygen is required for growth, despite the presence of the metabolic mechanism for anaerobic respiration. Amino acid auxotrophies are variably reported and energy metabolism can occur through several electron donor/acceptor combinations. Overall, the picture is one of a flexible, but vulnerable metabolism. To understand Campylobacter metabolism, we have constructed a fully curated, metabolic model for the reference organism M1 (our variant is M1cam) and validated it through laboratory experiments. Our results show that M1cam is auxotrophic for methionine, niacinamide, and pantothenate. There are complete biosynthesis pathways for all amino acids except methionine and it can produce energy, but not biomass, in the absence of oxygen. M1cam will grow in DMEM/F-12 defined media but not in the previously published Campylobacter specific defined media tested. Using the model, we identified potential auxotrophies and substrates that may improve growth. With this information, we designed simple defined media containing inorganic salts, the auxotrophic substrates, L-methionine, niacinamide, and pantothenate, pyruvate and additional amino acids L-cysteine, L-serine, and L-glutamine for growth enhancement. Our defined media supports a 1.75-fold higher growth rate than Brucella broth after 48 h at 37°C and sustains the growth of other Campylobacter jejuni strains. This media can be used to design reproducible assays that can help in better understanding the adaptation, stress resistance, and the virulence mechanisms of this pathogen. We have shown that with a well-curated metabolic model it is possible to design a media to grow this fastidious organism. This has implications for the investigation of new Campylobacter species defined through metagenomics, such as C. infans.
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Affiliation(s)
- Noemi Tejera
- Microbes in Food Chain, Quadram Institute Biosciences, Norwich Research Park, Norwich, United Kingdom
| | - Lisa Crossman
- Microbes in Food Chain, Quadram Institute Biosciences, Norwich Research Park, Norwich, United Kingdom.,SequenceAnalysis.co.uk, NRP Innovation Centre, Norwich, United Kingdom.,University of East Anglia, Norwich, United Kingdom
| | - Bruce Pearson
- Microbes in Food Chain, Quadram Institute Biosciences, Norwich Research Park, Norwich, United Kingdom
| | - Emily Stoakes
- Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Fauzy Nasher
- London School of Hygiene and Tropical Medicine, University of London, London, United Kingdom
| | - Bilal Djeghout
- Microbes in Food Chain, Quadram Institute Biosciences, Norwich Research Park, Norwich, United Kingdom
| | - Mark Poolman
- Cell Systems Modelling Group, Oxford Brookes University, Oxford, United Kingdom
| | - John Wain
- Microbes in Food Chain, Quadram Institute Biosciences, Norwich Research Park, Norwich, United Kingdom
| | - Dipali Singh
- Microbes in Food Chain, Quadram Institute Biosciences, Norwich Research Park, Norwich, United Kingdom
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8
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Wulsten IF, Galeev A, Stingl K. Underestimated Survival of Campylobacter in Raw Milk Highlighted by Viability Real-Time PCR and Growth Recovery. Front Microbiol 2020; 11:1107. [PMID: 32625171 PMCID: PMC7311638 DOI: 10.3389/fmicb.2020.01107] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2020] [Accepted: 05/04/2020] [Indexed: 02/03/2023] Open
Abstract
Raw milk is a frequent vehicle for transmission of thermophilic Campylobacter, leading to reported outbreaks. Milk is a challenging food matrix for pathogen detection, due to its high protein and lipid content. Limited detection of Campylobacter colony-forming unit (CFU) in raw milk might underestimate the pathogen's infectious potential. We optimized a viability real-time PCR (qPCR) for application with raw milk. The procedure was robust against variations of milk lots and different Campylobacter strains. Various DNA-intercalating dyes were evaluated for their ability to reduce the PCR signal of dead cells. Only propidium monoazide (PMA) and PMAxx qualified for diagnostic use. Different sedimentation properties of viable and dead Campylobacter jejuni and Campylobacter coli strains in 10-fold diluted milk enhanced viable/dead differentiation. The new method enabled to review survival of Campylobacter spp. in raw milk based on viable cells harboring an intact cell membrane. The data were compared to culturability according to ISO10272-2:2017. A difference of up to 4.5 log10 between viable Campylobacter counts and CFU values became apparent. Relevance of viability qPCR values was corroborated by full recovery of CFU under extremely reduced oxygen concentration in the presence of hydrogen. Recovery of CFU was limited, however, upon prolonged exposure in raw milk. The data confirm that Campylobacter survival in raw milk can be largely underestimated when relying on CFU data only. We conclude that raw milk led to oxidative stress-induced growth arrest in thermophilic Campylobacter, which was reversible by reduction of the oxygen partial pressure in a time-limited way.
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Affiliation(s)
- Imke F. Wulsten
- National Reference Laboratory for Campylobacter, Department of Biological Safety, German Federal Institute for Risk Assessment (BfR), Berlin, Germany
| | - Alibek Galeev
- Institute of Medical Microbiology and Hospital Epidemiology, Hannover Medical School (MHH), Hannover, Germany
| | - Kerstin Stingl
- National Reference Laboratory for Campylobacter, Department of Biological Safety, German Federal Institute for Risk Assessment (BfR), Berlin, Germany
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9
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Li B, Yang N, Shan Y, Wang X, Hao Y, Mao R, Teng D, Fan H, Wang J. Therapeutic potential of a designed CSαβ peptide ID13 in Staphylococcus aureus-induced endometritis of mice. Appl Microbiol Biotechnol 2020; 104:6693-6705. [PMID: 32506158 PMCID: PMC7275135 DOI: 10.1007/s00253-020-10685-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 05/07/2020] [Accepted: 05/17/2020] [Indexed: 02/07/2023]
Abstract
Staphylococcus aureus is a common pathogen that can cause clinical and subclinical endometritis in humans and animals. In this study, a designed CSαβ peptide ID13 from DLP4 exhibited high stable antibacterial activity in simulated gastric fluid (90.79%), serum (99.54%), and different pH buffers (> 99%) against S. aureus CVCC 546 and lower cytotoxicity (89.62% viability) than its parent peptide DLP4 (74.14% viability) toward mouse endometrial epithelial cells (MEECs). ID13 caused a depolarization of bacterial membrane and downregulation of the expression of genes involved in membrane potential maintenance and biofilm formation. The in vitro efficacy analysis of ID13 showed a synergistic effect with vancomycin, ampicillin, rifampin, and ciprofloxacin; intracellular antimicrobial activity against S. aureus CVCC 546 in MEECs; and the ability to inhibit lipoteichoic acid-induced pro-inflammatory cytokines from RAW 264.7. In the S. aureus-induced endometritis of mice, similar to vancomycin, ID13 remarkably alleviated pathological conditions, inhibited the production of cytokines (TNF-α, IL-1ß, IL-6, and IL-10), and suppressed the TLR2-NF-κB signal pathway. Collectively, these results suggest that ID13 could be a potential candidate peptide for therapeutic application in S. aureus-induced endometritis. Key Points •Higher antibacterial activity and lower hemolysis of ID13 than DLP4. •ID13 could downregulate the genes of bacterial survival and infection. •ID13 could alleviate the S. aureus-induced endometritis of mice. •ID13 could regulate the cytokines and suppress the TLR2-NF-κB signal pathway.
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Affiliation(s)
- Bing Li
- Team of Alternatives to Antibiotics, Gene Engineering Lab, Feed Research Institute, Chinese Academy of Agricultural Science, Beijing, 100081, People's Republic of China.,Key Laboratory of Feed Biotechnology, Ministry of Agriculture and Rural Affairs, Beijing, 100081, People's Republic of China
| | - Na Yang
- Team of Alternatives to Antibiotics, Gene Engineering Lab, Feed Research Institute, Chinese Academy of Agricultural Science, Beijing, 100081, People's Republic of China.,Key Laboratory of Feed Biotechnology, Ministry of Agriculture and Rural Affairs, Beijing, 100081, People's Republic of China
| | - Yuxue Shan
- Team of Alternatives to Antibiotics, Gene Engineering Lab, Feed Research Institute, Chinese Academy of Agricultural Science, Beijing, 100081, People's Republic of China.,Key Laboratory of Feed Biotechnology, Ministry of Agriculture and Rural Affairs, Beijing, 100081, People's Republic of China.,Tianjin Animal Science and Veterinary Research Institute, Tianjin, 300381, People's Republic of China
| | - Xiumin Wang
- Team of Alternatives to Antibiotics, Gene Engineering Lab, Feed Research Institute, Chinese Academy of Agricultural Science, Beijing, 100081, People's Republic of China.,Key Laboratory of Feed Biotechnology, Ministry of Agriculture and Rural Affairs, Beijing, 100081, People's Republic of China
| | - Ya Hao
- Team of Alternatives to Antibiotics, Gene Engineering Lab, Feed Research Institute, Chinese Academy of Agricultural Science, Beijing, 100081, People's Republic of China.,Key Laboratory of Feed Biotechnology, Ministry of Agriculture and Rural Affairs, Beijing, 100081, People's Republic of China
| | - Ruoyu Mao
- Team of Alternatives to Antibiotics, Gene Engineering Lab, Feed Research Institute, Chinese Academy of Agricultural Science, Beijing, 100081, People's Republic of China. .,Key Laboratory of Feed Biotechnology, Ministry of Agriculture and Rural Affairs, Beijing, 100081, People's Republic of China.
| | - Da Teng
- Team of Alternatives to Antibiotics, Gene Engineering Lab, Feed Research Institute, Chinese Academy of Agricultural Science, Beijing, 100081, People's Republic of China. .,Key Laboratory of Feed Biotechnology, Ministry of Agriculture and Rural Affairs, Beijing, 100081, People's Republic of China.
| | - Huan Fan
- Tianjin Animal Science and Veterinary Research Institute, Tianjin, 300381, People's Republic of China
| | - Jianhua Wang
- Team of Alternatives to Antibiotics, Gene Engineering Lab, Feed Research Institute, Chinese Academy of Agricultural Science, Beijing, 100081, People's Republic of China. .,Key Laboratory of Feed Biotechnology, Ministry of Agriculture and Rural Affairs, Beijing, 100081, People's Republic of China.
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10
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Yeow M, Liu F, Ma R, Williams TJ, Riordan SM, Zhang L. Analyses of energy metabolism and stress defence provide insights into Campylobacter concisus growth and pathogenicity. Gut Pathog 2020; 12:13. [PMID: 32165925 PMCID: PMC7059363 DOI: 10.1186/s13099-020-00349-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 02/15/2020] [Indexed: 02/08/2023] Open
Abstract
Campylobacter concisus is an emerging enteric pathogen that is associated with inflammatory bowel disease. Previous studies demonstrated that C. concisus is non-saccharolytic and hydrogen gas (H2) is a critical factor for C. concisus growth. In order to understand the molecular basis of the non-saccharolytic and H2-dependent nature of C. concisus growth, in this study we examined the pathways involving energy metabolism and oxidative stress defence in C. concisus. Bioinformatic analysis of C. concisus genomes in comparison with the well-studied enteric pathogen Campylobacter jejuni was performed. This study found that C. concisus lacks a number of key enzymes in glycolysis, including glucokinase and phosphofructokinase, and the oxidative pentose phosphate pathway. C. concisus has an incomplete tricarboxylic acid cycle, with no identifiable succinyl-CoA synthase or fumarate hydratase. C. concisus was inferred to use fewer amino acids and have fewer candidate substrates as electron donors and acceptors compared to C. jejuni. The addition of DMSO or fumarate to media resulted in significantly increased growth of C. concisus in the presence of H2 as an electron donor, demonstrating that both can be used as electron acceptors. Catalase, an essential enzyme for oxidative stress defence in C. jejuni, and various nitrosative stress enzymes, were not found in the C. concisus genome. Overall, C. concisus is inferred to have a non-saccharolytic metabolism in which H2 is central to energy conservation, and a narrow selection of carboxylic acids and amino acids can be utilised as organic substrates. In conclusion, this study provides a molecular basis for the non-saccharolytic and hydrogen-dependent nature of C. concisus energy metabolism pathways, which provides insights into the growth requirements and pathogenicity of this species.
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Affiliation(s)
- Melissa Yeow
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Kensington, Sydney, 2052 Australia
| | - Fang Liu
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Kensington, Sydney, 2052 Australia
| | - Rena Ma
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Kensington, Sydney, 2052 Australia
| | - Timothy J. Williams
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Kensington, Sydney, 2052 Australia
| | - Stephen M. Riordan
- Gastrointestinal and Liver Unit, Prince of Wales Hospital, University of New South Wales, Sydney, Australia
| | - Li Zhang
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Kensington, Sydney, 2052 Australia
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11
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Benoit SL, Maier RJ, Sawers RG, Greening C. Molecular Hydrogen Metabolism: a Widespread Trait of Pathogenic Bacteria and Protists. Microbiol Mol Biol Rev 2020; 84:e00092-19. [PMID: 31996394 PMCID: PMC7167206 DOI: 10.1128/mmbr.00092-19] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Pathogenic microorganisms use various mechanisms to conserve energy in host tissues and environmental reservoirs. One widespread but often overlooked means of energy conservation is through the consumption or production of molecular hydrogen (H2). Here, we comprehensively review the distribution, biochemistry, and physiology of H2 metabolism in pathogens. Over 200 pathogens and pathobionts carry genes for hydrogenases, the enzymes responsible for H2 oxidation and/or production. Furthermore, at least 46 of these species have been experimentally shown to consume or produce H2 Several major human pathogens use the large amounts of H2 produced by colonic microbiota as an energy source for aerobic or anaerobic respiration. This process has been shown to be critical for growth and virulence of the gastrointestinal bacteria Salmonella enterica serovar Typhimurium, Campylobacter jejuni, Campylobacter concisus, and Helicobacter pylori (including carcinogenic strains). H2 oxidation is generally a facultative trait controlled by central regulators in response to energy and oxidant availability. Other bacterial and protist pathogens produce H2 as a diffusible end product of fermentation processes. These include facultative anaerobes such as Escherichia coli, S Typhimurium, and Giardia intestinalis, which persist by fermentation when limited for respiratory electron acceptors, as well as obligate anaerobes, such as Clostridium perfringens, Clostridioides difficile, and Trichomonas vaginalis, that produce large amounts of H2 during growth. Overall, there is a rich literature on hydrogenases in growth, survival, and virulence in some pathogens. However, we lack a detailed understanding of H2 metabolism in most pathogens, especially obligately anaerobic bacteria, as well as a holistic understanding of gastrointestinal H2 transactions overall. Based on these findings, we also evaluate H2 metabolism as a possible target for drug development or other therapies.
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Affiliation(s)
- Stéphane L Benoit
- Department of Microbiology, University of Georgia, Athens, Georgia, USA
| | - Robert J Maier
- Department of Microbiology, University of Georgia, Athens, Georgia, USA
| | - R Gary Sawers
- Institute of Microbiology, Martin Luther University Halle-Wittenberg, Halle, Germany
| | - Chris Greening
- School of Biological Sciences, Monash University, Clayton, VIC, Australia
- Department of Microbiology, Monash Biomedicine Discovery Institute, Clayton, VIC, Australia
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12
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van der Stel AX, Wösten MMSM. Regulation of Respiratory Pathways in Campylobacterota: A Review. Front Microbiol 2019; 10:1719. [PMID: 31417516 PMCID: PMC6682613 DOI: 10.3389/fmicb.2019.01719] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Accepted: 07/11/2019] [Indexed: 12/19/2022] Open
Abstract
The Campylobacterota, previously known as Epsilonproteobacteria, are a large group of Gram-negative mainly, spiral-shaped motile bacteria. Some members like the Sulfurospirillum spp. are free-living, while others such as Helicobacter spp. can only persist in strict association with a host organism as commensal or as pathogen. Species of this phylum colonize diverse habitats ranging from deep-sea thermal vents to the human stomach wall. Despite their divergent environments, they share common energy conservation mechanisms. The Campylobacterota have a large and remarkable repertoire of electron transport chain enzymes, given their small genomes. Although members of recognized families of transcriptional regulators are found in these genomes, sofar no orthologs known to be important for energy or redox metabolism such as ArcA, FNR or NarP are encoded in the genomes of the Campylobacterota. In this review, we discuss the strategies that members of Campylobacterota utilize to conserve energy and the corresponding regulatory mechanisms that regulate the branched electron transport chains in these bacteria.
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Affiliation(s)
| | - Marc M. S. M. Wösten
- Department of Infectious Diseases and Immunology, Utrecht University, Utrecht, Netherlands
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13
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Taylor AJ, Kelly DJ. The function, biogenesis and regulation of the electron transport chains in Campylobacter jejuni: New insights into the bioenergetics of a major food-borne pathogen. Adv Microb Physiol 2019; 74:239-329. [PMID: 31126532 DOI: 10.1016/bs.ampbs.2019.02.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Campylobacter jejuni is a zoonotic Epsilonproteobacterium that grows in the gastrointestinal tract of birds and mammals, and is the most frequent cause of food-borne bacterial gastroenteritis worldwide. As an oxygen-sensitive microaerophile, C. jejuni has to survive high environmental oxygen tensions, adapt to oxygen limitation in the host intestine and resist host oxidative attack. Despite its small genome size, C. jejuni is a versatile and metabolically active pathogen, with a complex and highly branched set of respiratory chains allowing the use of a wide range of electron donors and alternative electron acceptors in addition to oxygen, including fumarate, nitrate, nitrite, tetrathionate and N- or S-oxides. Several novel enzymes participate in these electron transport chains, including a tungsten containing formate dehydrogenase, a Complex I that uses flavodoxin and not NADH, a periplasmic facing fumarate reductase and a cytochrome c tetrathionate reductase. This review presents an updated description of the composition and bioenergetics of these various respiratory chains as they are currently understood, including recent work that gives new insights into energy conservation during electron transport to various alternative electron acceptors. The regulation of synthesis and assembly of the electron transport chains is also discussed. A deeper appreciation of the unique features of the respiratory systems of C. jejuni may be helpful in informing strategies to control this important pathogen.
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Affiliation(s)
- Aidan J Taylor
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Western Bank, Sheffield S10 2TN, UK
| | - David J Kelly
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Western Bank, Sheffield S10 2TN, UK
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14
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Garg N, Taylor AJ, Kelly DJ. Bacterial periplasmic nitrate and trimethylamine-N-oxide respiration coupled to menaquinol-cytochrome c reductase (Qcr): Implications for electrogenic reduction of alternative electron acceptors. Sci Rep 2018; 8:15478. [PMID: 30341307 PMCID: PMC6195509 DOI: 10.1038/s41598-018-33857-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 10/08/2018] [Indexed: 12/14/2022] Open
Abstract
The periplasmic reduction of the electron acceptors nitrate (Em +420 mV) and trimethylamine-N-oxide (TMAO; Em +130 mV) by Nap and Tor reductases is widespread in Gram-negative bacteria and is usually considered to be driven by non-energy conserving quinol dehydrogenases. The Epsilonproteobacterium Campylobacter jejuni can grow by nitrate and TMAO respiration and it has previously been assumed that these alternative pathways of electron transport are independent of the proton-motive menaquinol-cytochrome c reductase complex (QcrABC) that functions in oxygen-linked respiration. Here, we show that a qcrABC deletion mutant is completely deficient in oxygen-limited growth on both nitrate and TMAO and is unable to reduce these oxidants with physiological electron donors. As expected, the mutant grows normally on fumarate under oxygen-limited conditions. Thus, the periplasmic Nap and Tor reductases receive their electrons via QcrABC in C. jejuni, explaining the general absence of NapC and TorC quinol dehydrogenases in Epsilonproteobacteria. Moreover, the specific use of menaquinol (Em -75 mV) coupled with a Qcr complex to drive reduction of nitrate or TMAO against the proton-motive force allows the process to be electrogenic with a H+/2e- ratio of 2. The results have general implications for the role of Qcr complexes in bacterial oxygen-independent respiration and growth.
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Affiliation(s)
- Nitanshu Garg
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, UK
| | - Aidan J Taylor
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, UK
| | - David J Kelly
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, UK.
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15
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van der Stel AX, van de Lest CHA, Huynh S, Parker CT, van Putten JPM, Wösten MMSM. Catabolite repression in Campylobacter jejuni correlates with intracellular succinate levels. Environ Microbiol 2018; 20:1374-1388. [PMID: 29318721 DOI: 10.1111/1462-2920.14042] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 01/06/2018] [Indexed: 12/28/2022]
Abstract
Bacteria have evolved different mechanisms to catabolize carbon sources from nutrient mixtures. They first consume their preferred carbon source, before others are used. Regulatory mechanisms adapt the metabolism accordingly to maximize growth and to outcompete other organisms. The human pathogen Campylobacter jejuni is an asaccharolytic Gram-negative bacterium that catabolizes amino acids and organic acids for growth. It prefers serine and aspartate as carbon sources, however it lacks all regulators known to be involved in regulating carbon source utilization in other organisms. In which manner C. jejuni adapts its metabolism towards the presence or absence of preferred carbon sources is unknown. In this study, we show with transcriptomic analysis and enzyme assays how C. jejuni adapts its metabolism in response to its preferred carbon sources. In the presence of serine as well as lactate and pyruvate C. jejuni inhibits the utilization of other carbon sources, by repressing the expression of a number of central metabolic enzymes. The regulatory proteins RacR, Cj1000 and CsrA play a role in the regulation of these metabolic enzymes. This metabolism dependent transcriptional repression correlates with an accumulation of intracellular succinate. Hence, we propose a demand-based catabolite repression mechanism in C. jejuni, depended on intracellular succinate levels.
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Affiliation(s)
| | - Chris H A van de Lest
- Department of Biochemistry and Cell Biology, Utrecht University, Utrecht, The Netherlands
| | - Steven Huynh
- Agricultural Research Service, U.S. Department of Agriculture, Produce Safety and Microbiology Research Unit, Albany, CA, USA
| | - Craig T Parker
- Agricultural Research Service, U.S. Department of Agriculture, Produce Safety and Microbiology Research Unit, Albany, CA, USA
| | - Jos P M van Putten
- Department of Infectious Diseases and Immunology, Utrecht University, Utrecht, The Netherlands
| | - Marc M S M Wösten
- Department of Infectious Diseases and Immunology, Utrecht University, Utrecht, The Netherlands
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16
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Guccione EJ, Kendall JJ, Hitchcock A, Garg N, White MA, Mulholland F, Poole RK, Kelly DJ. Transcriptome and proteome dynamics in chemostat culture reveal how Campylobacter jejuni modulates metabolism, stress responses and virulence factors upon changes in oxygen availability. Environ Microbiol 2017; 19:4326-4348. [PMID: 28892295 PMCID: PMC5656828 DOI: 10.1111/1462-2920.13930] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Revised: 09/04/2017] [Accepted: 09/07/2017] [Indexed: 12/15/2022]
Abstract
Campylobacter jejuni, the most frequent cause of food‐borne bacterial gastroenteritis worldwide, is a microaerophile that has to survive high environmental oxygen tensions, adapt to oxygen limitation in the intestine and resist host oxidative attack. Here, oxygen‐dependent changes in C. jejuni physiology were studied at constant growth rate using carbon (serine)‐limited continuous chemostat cultures. We show that a perceived aerobiosis scale can be calibrated by the acetate excretion flux, which becomes zero when metabolism is fully aerobic (100% aerobiosis). Transcriptome changes in a downshift experiment from 150% to 40% aerobiosis revealed many novel oxygen‐regulated genes and highlighted re‐modelling of the electron transport chains. A label‐free proteomic analysis showed that at 40% aerobiosis, many proteins involved in host colonisation (e.g., PorA, CadF, FlpA, CjkT) became more abundant. PorA abundance increased steeply below 100% aerobiosis. In contrast, several citric‐acid cycle enzymes, the peptide transporter CstA, PEB1 aspartate/glutamate transporter, LutABC lactate dehydrogenase and PutA proline dehydrogenase became more abundant with increasing aerobiosis. We also observed a co‐ordinated response of oxidative stress protection enzymes and Fe‐S cluster biogenesis proteins above 100% aerobiosis. Our approaches reveal key virulence factors that respond to restricted oxygen availability and specific transporters and catabolic pathways activated with increasing aerobiosis.
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Affiliation(s)
- Edward J Guccione
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK
| | - John J Kendall
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK
| | - Andrew Hitchcock
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK
| | - Nitanshu Garg
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK
| | - Michael A White
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK
| | - Francis Mulholland
- Institute of Food Research, Norwich Research Park, Colney Lane, Norwich NR4 7UA, UK
| | - Robert K Poole
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK
| | - David J Kelly
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK
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