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Manoharan S, Taylor-Joyce G, Brooker TA, Hernández Rodríguez CS, Hapeshi A, Baldwin V, Baillie L, Oyston PCF, Waterfield NR. From cereus to anthrax and back again: Assessment of the temperature-dependent phenotypic switching in the "cross-over" strain Bacillus cereus G9241. Front Microbiol 2023; 14:1113562. [PMID: 36937299 PMCID: PMC10017872 DOI: 10.3389/fmicb.2023.1113562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Accepted: 02/07/2023] [Indexed: 03/06/2023] Open
Abstract
Bacillus cereus G9241 was isolated from a Louisiana welder suffering from an anthrax-like infection. The organism carries two transcriptional regulators that have previously been proposed to be incompatible with each other in Bacillus anthracis: the pleiotropic transcriptional regulator PlcR found in most members of the Bacillus cereus group but truncated in all B. anthracis isolates, and the anthrax toxin regulator AtxA found in all B. anthracis strains and a few B. cereus sensu stricto strains. Here we report cytotoxic and hemolytic activity of cell free B. cereus G9241 culture supernatants cultured at 25°C to various eukaryotic cells. However, this is not observed at the mammalian infection relevant temperature 37°C, behaving much like the supernatants generated by B. anthracis. Using a combination of genetic and proteomic approaches to understand this unique phenotype, we identified several PlcR-regulated toxins to be secreted highly at 25°C compared to 37°C. Furthermore, results suggest that differential expression of the protease involved in processing the PlcR quorum sensing activator molecule PapR appears to be the limiting step for the production of PlcR-regulated toxins at 37°C, giving rise to the temperature-dependent hemolytic and cytotoxic activity of the culture supernatants. This study provides an insight on how B. cereus G9241 is able to "switch" between B. cereus and B. anthracis-like phenotypes in a temperature-dependent manner, potentially accommodating the activities of both PlcR and AtxA.
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Affiliation(s)
- Shathviga Manoharan
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom
| | - Grace Taylor-Joyce
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom
| | - Thomas A. Brooker
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom
| | | | - Alexia Hapeshi
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom
| | | | - Les Baillie
- School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Cardiff, United Kingdom
| | | | - Nicholas R. Waterfield
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom
- *Correspondence: Nicholas R. Waterfield,
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Microaerobic conditions enhance laccase production from Rheinheimera sp. in an economical medium. Arch Microbiol 2022; 204:562. [PMID: 35980477 DOI: 10.1007/s00203-022-03170-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 05/19/2022] [Accepted: 08/04/2022] [Indexed: 12/06/2022]
Abstract
Statistical optimization of aeration conditions viz. aerobic, microaerobic and anaerobic, was performed using response surface methodology (RSM) utilizing soybean meal as medium to enhance the production of laccase from Rheinheimera sp. Maximum laccase yield (18.48 × 105 U/L) was obtained under microaerobic (static) conditions sustained for 12 h in tandem with 26 h aerobically (150 rpm) grown culture, which was 17.03-fold higher than laccase production in the starting M162 medium under aerobic conditions (150 rpm). The reduction in incubation time from 72 to 38 h and utilization of cost-effective soybean meal as medium, which is easily available from local market, have provided a promising, eco-friendly method of laccase enzyme production. Enhanced expression of laccase gene under microaerobic conditions corresponded to the increased expression of fnr (fumarate nitrate reductase) gene, the oxygen sensing global regulator. The putative FNR-binding site upstream of laccase transcription initiation site was predicted to play an imperative role in Rheinheimera sp. adaptation from aerobic to microaerobic conditions and for enhanced laccase production.
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3
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Regulation of Enterotoxins Associated with Bacillus cereus Sensu Lato Toxicoinfection. Appl Environ Microbiol 2022; 88:e0040522. [PMID: 35730937 PMCID: PMC9275247 DOI: 10.1128/aem.00405-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Bacillus cereus sensu lato (s.l.) includes foodborne pathogens, as well as beneficial microorganisms, such as bioinsecticides. Some of the beneficial and commercially used B. cereus s.l. strains have been shown to carry enterotoxin genes, the products of which can cause toxicoinfection in humans. Furthermore, recent epidemiological reports indicated that some bioinsecticidal strains have been linked with foodborne illness outbreaks. This demonstrates the need for improved surveillance of B. cereus s.l., which includes characterization of isolates' virulence capacity. However, the prediction of virulence capacity of B. cereus s.l. strains is challenging. Genetic screening for enterotoxin gene presence has proven to be insufficient for accurate discrimination between virulent and avirulent strains, given that nearly all B. cereus s.l. strains carry at least one enterotoxin gene. Furthermore, complex regulatory networks governing the expression of enterotoxins, and potential synergistic interactions between enterotoxins and other virulence factors make the prediction of toxicoinfection based on isolates' genome sequences challenging. In this review, we summarize and synthesize the current understanding of the regulation of enterotoxins associated with the B. cereus s.l. toxicoinfection and identify gaps in the knowledge that need to be addressed to facilitate identification of genetic markers predictive of cytotoxicity and toxicoinfection.
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Goel D, Kumar S, Joshi GK, Rai P, Bhatnagar R. Crp/fnr family protein binds to promoters of atxA and sodmn genes that regulate the expression of exotoxins in Bacillus anthracis. Protein Expr Purif 2022; 193:106059. [PMID: 35114377 DOI: 10.1016/j.pep.2022.106059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 01/28/2022] [Accepted: 01/29/2022] [Indexed: 11/30/2022]
Abstract
Bacillus anthracis produces a tripartite exotoxin, which is regulated by AtxA. Sodmn is constitutively expressed during invasion. Crp/Fnr family transcriptional regulators are known to bind promoters of toxin regulators as well as constitutively expressed genes during pathogenesis. B. anthracis fnr gene was cloned, over-expressed in E. coli and recombinant protein was purified. Oligomeric nature of recombinant rFnr protein was studied by diamide treatment and DTT reduction. DNA binding of rFnr protein was studied by EMSA. We observed that rFnr exists in both monomeric and oligomeric forms. It was found that rFnr was able to oligomerize after diamide treatment which was reversible through DTT reduction. Promoter regions of atxA and sodmn show binding to monomeric form of rFnr, however, dimeric form was unable to bind. Fnr might be playing a role in regulation of toxin gene expression via regulation of atxA gene. It can also be involved in regulation of pathogenesis by regulating the sodmn expression. Oligomerization can act as an ON/OFF switch for the Fnr mediated regulation.
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Affiliation(s)
- Divya Goel
- Department of Biotechnology, H.N.B. Garhwal University, Srinagar (Garhwal), Uttarakhand, 246174, India; School of Biotechnology, Jawaharlal Nehru University, New Delhi, 110085, India.
| | - Sudhir Kumar
- Department of Biotechnology, H.N.B. Garhwal University, Srinagar (Garhwal), Uttarakhand, 246174, India
| | - Gopal Krishna Joshi
- Department of Biotechnology, H.N.B. Garhwal University, Srinagar (Garhwal), Uttarakhand, 246174, India
| | - Prashant Rai
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, 110085, India
| | - Rakesh Bhatnagar
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, 110085, India
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5
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Hu H, Liu M, Sun S. Pore-Forming Toxins During Bacterial Infection: Molecular Mechanisms and Potential Therapeutic Targets. DRUG DESIGN DEVELOPMENT AND THERAPY 2021; 15:3773-3781. [PMID: 34522083 PMCID: PMC8434828 DOI: 10.2147/dddt.s322393] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 08/19/2021] [Indexed: 12/17/2022]
Abstract
Bacterial infections are predominantly treated with antibiotics, and resistance to antibiotics is becoming an increasing threat to our health. Pore-forming toxins (PFTs) are virulence factors secreted by many pathogenic bacterial strains, both in acute and chronic infections. They are special membrane-targeting proteins that exert toxic effects by forming pores in the cell membrane. Recent studies have elucidated the structure of PFTs and the detailed molecular mechanisms of their pathogenicity. Here, we discuss recent findings that highlight the regulatory mechanisms and important roles of two types of PFTs, α-PFTs and β-PFTs, in mediating the virulence of bacteria, and the therapeutic potential of targeting PFTs for antibacterial treatment. Therapeutic strategies based on PFTs are highly specific and may alleviate the issue of increasing resistance to antibiotics.
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Affiliation(s)
- Haijie Hu
- Institute of Biomedical Sciences, Shandong Provincial Key Laboratory of Animal Resistance Biology, Collaborative Innovation Center of Cell Biology in Universities of Shandong, College of Life Sciences, Shandong Normal University, Jinan, 250014, People's Republic of China
| | - Min Liu
- Institute of Biomedical Sciences, Shandong Provincial Key Laboratory of Animal Resistance Biology, Collaborative Innovation Center of Cell Biology in Universities of Shandong, College of Life Sciences, Shandong Normal University, Jinan, 250014, People's Republic of China
| | - Shuang Sun
- Institute of Biomedical Sciences, Shandong Provincial Key Laboratory of Animal Resistance Biology, Collaborative Innovation Center of Cell Biology in Universities of Shandong, College of Life Sciences, Shandong Normal University, Jinan, 250014, People's Republic of China
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Hamitouche F, Armengaud J, Dedieu L, Duport C. Cysteine Proteome Reveals Response to Endogenous Oxidative Stress in Bacillus cereus. Int J Mol Sci 2021; 22:7550. [PMID: 34299167 PMCID: PMC8305198 DOI: 10.3390/ijms22147550] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 07/08/2021] [Accepted: 07/12/2021] [Indexed: 12/30/2022] Open
Abstract
At the end of exponential growth, aerobic bacteria have to cope with the accumulation of endogenous reactive oxygen species (ROS). One of the main targets of these ROS is cysteine residues in proteins. This study uses liquid chromatography coupled to high-resolution tandem mass spectrometry to detect significant changes in protein abundance and thiol status for cysteine-containing proteins from Bacillus cereus during aerobic exponential growth. The proteomic profiles of cultures at early-, middle-, and late-exponential growth phases reveals that (i) enrichment in proteins dedicated to fighting ROS as growth progressed, (ii) a decrease in both overall proteome cysteine content and thiol proteome redox status, and (iii) changes to the reduced thiol status of some key proteins, such as the transition state transcriptional regulator AbrB. Taken together, our data indicate that growth under oxic conditions requires increased allocation of protein resources to attenuate the negative effects of ROS. Our data also provide a strong basis to understand the response mechanisms used by B. cereus to deal with endogenous oxidative stress.
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Affiliation(s)
- Fella Hamitouche
- Biology Department, Campus Jean-Henri Fabre, Avignon University, INRAE, UMR SQPOV, CEDEX 09, 84911 Avignon, France; (F.H.); (L.D.)
| | - Jean Armengaud
- Département Médicaments et Technologies pour la Santé (DMTS), Université Paris-Saclay, CEA, INRAE, SPI, 30200 Bagnols-sur-Cèze, France;
| | - Luc Dedieu
- Biology Department, Campus Jean-Henri Fabre, Avignon University, INRAE, UMR SQPOV, CEDEX 09, 84911 Avignon, France; (F.H.); (L.D.)
| | - Catherine Duport
- Biology Department, Campus Jean-Henri Fabre, Avignon University, INRAE, UMR SQPOV, CEDEX 09, 84911 Avignon, France; (F.H.); (L.D.)
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Jovanovic J, Ornelis VFM, Madder A, Rajkovic A. Bacillus cereus food intoxication and toxicoinfection. Compr Rev Food Sci Food Saf 2021; 20:3719-3761. [PMID: 34160120 DOI: 10.1111/1541-4337.12785] [Citation(s) in RCA: 55] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 05/13/2021] [Accepted: 05/15/2021] [Indexed: 12/12/2022]
Abstract
Bacillus cereus is one of the leading etiological agents of toxin-induced foodborne diseases. Its omnipresence in different environments, spore formation, and its ability to adapt to varying conditions and produce harmful toxins make this pathogen a health hazard that should not be underestimated. Food poisoning by B. cereus can manifest itself as an emetic or diarrheal syndrome. The former is caused by the release of the potent peptide toxin cereulide, whereas the latter is the result of proteinaceous enterotoxins (e.g., hemolysin BL, nonhemolytic enterotoxin, and cytotoxin K). The final harmful effect is not only toxin and strain dependent, but is also affected by the stress responses, accessory virulence factors, and phenotypic properties under extrinsic, intrinsic, and explicit food conditions and host-related environment. Infamous portrait of B. cereus as a foodborne pathogen, as well as a causative agent of nongastrointestinal infections and even nosocomial complications, has inspired vast volumes of multidisciplinary research in food and clinical domains. As a result, extensive original data became available asking for a new, both broad and deep, multifaceted look into the current state-of-the art regarding the role of B. cereus in food safety. In this review, we first provide an overview of the latest knowledge on B. cereus toxins and accessory virulence factors. Second, we describe the novel taxonomy and some of the most pertinent phenotypic characteristics of B. cereus related to food safety. We link these aspects to toxin production, overall pathogenesis, and interactions with its human host. Then we reflect on the prevalence of different toxinotypes in foods opening the scene for epidemiological aspects of B. cereus foodborne diseases and methods available to prevent food poisoning including overview of the different available methods to detect B. cereus and its toxins.
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Affiliation(s)
- Jelena Jovanovic
- Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Vincent F M Ornelis
- Department of Organic and Macromolecular Chemistry, Faculty of Sciences, Ghent University, Ghent, Belgium
| | - Annemieke Madder
- Department of Organic and Macromolecular Chemistry, Faculty of Sciences, Ghent University, Ghent, Belgium
| | - Andreja Rajkovic
- Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
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8
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The Food Poisoning Toxins of Bacillus cereus. Toxins (Basel) 2021; 13:toxins13020098. [PMID: 33525722 PMCID: PMC7911051 DOI: 10.3390/toxins13020098] [Citation(s) in RCA: 99] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 01/14/2021] [Accepted: 01/25/2021] [Indexed: 12/13/2022] Open
Abstract
Bacillus cereus is a ubiquitous soil bacterium responsible for two types of food-associated gastrointestinal diseases. While the emetic type, a food intoxication, manifests in nausea and vomiting, food infections with enteropathogenic strains cause diarrhea and abdominal pain. Causative toxins are the cyclic dodecadepsipeptide cereulide, and the proteinaceous enterotoxins hemolysin BL (Hbl), nonhemolytic enterotoxin (Nhe) and cytotoxin K (CytK), respectively. This review covers the current knowledge on distribution and genetic organization of the toxin genes, as well as mechanisms of enterotoxin gene regulation and toxin secretion. In this context, the exceptionally high variability of toxin production between single strains is highlighted. In addition, the mode of action of the pore-forming enterotoxins and their effect on target cells is described in detail. The main focus of this review are the two tripartite enterotoxin complexes Hbl and Nhe, but the latest findings on cereulide and CytK are also presented, as well as methods for toxin detection, and the contribution of further putative virulence factors to the diarrheal disease.
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Jessberger N, Dietrich R, Granum PE, Märtlbauer E. The Bacillus cereus Food Infection as Multifactorial Process. Toxins (Basel) 2020; 12:E701. [PMID: 33167492 PMCID: PMC7694497 DOI: 10.3390/toxins12110701] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 10/30/2020] [Accepted: 11/02/2020] [Indexed: 02/06/2023] Open
Abstract
The ubiquitous soil bacterium Bacillus cereus presents major challenges to food safety. It is responsible for two types of food poisoning, the emetic form due to food intoxication and the diarrheal form emerging from food infections with enteropathogenic strains, also known as toxico-infections, which are the subject of this review. The diarrheal type of food poisoning emerges after production of enterotoxins by viable bacteria in the human intestine. Basically, the manifestation of the disease is, however, the result of a multifactorial process, including B. cereus prevalence and survival in different foods, survival of the stomach passage, spore germination, motility, adhesion, and finally enterotoxin production in the intestine. Moreover, all of these processes are influenced by the consumed foodstuffs as well as the intestinal microbiota which have, therefore, to be considered for a reliable prediction of the hazardous potential of contaminated foods. Current knowledge regarding these single aspects is summarized in this review aiming for risk-oriented diagnostics for enteropathogenic B. cereus.
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Affiliation(s)
- Nadja Jessberger
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Schönleutnerstr. 8, 85764 Oberschleißheim, Germany; (R.D.); (E.M.)
| | - Richard Dietrich
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Schönleutnerstr. 8, 85764 Oberschleißheim, Germany; (R.D.); (E.M.)
| | - Per Einar Granum
- Department of Food Safety and Infection Biology, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, P.O. Box 5003 NMBU, 1432 Ås, Norway;
| | - Erwin Märtlbauer
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Schönleutnerstr. 8, 85764 Oberschleißheim, Germany; (R.D.); (E.M.)
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10
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Li H, O'Hair J, Thapa S, Bhatti S, Zhou S, Yang Y, Fish T, Thannhauser TW. Proteome profile changes during poly-hydroxybutyrate intracellular mobilization in gram positive Bacillus cereus tsu1. BMC Microbiol 2020; 20:122. [PMID: 32429845 PMCID: PMC7236355 DOI: 10.1186/s12866-020-01815-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Accepted: 05/07/2020] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND Bacillus cereus is a bacterial species which grows efficiently on a wide range of carbon sources and accumulates biopolymer poly-hydroxybutyrate (PHB) up to 80% cell dry weight. PHB is an aliphatic polymer produced and stored intracellularly as a reservoir of carbon and energy, its mobilization is a key biological process for sporulation in Bacillus spp. Previously, B. cereus tsu1 was isolated and cultured on rapeseed cake substrate (RCS), with maximum of PHB accumulation reached within 12 h, and depleted after 48 h. Fore-spore and spore structure were observed after 24 h culture. RESULTS Quantitative proteomic analysis of B. cereus tsu1 identified 2952 quantifiable proteins, and 244 significantly changed proteins (SCPs) in the 24 h:12 h pair of samples, and 325 SCPs in the 48 h:12 h pair of samples. Based on gene ontology classification analysis, biological processes enriched only in the 24 h:12 h SCPs include purine nucleotide metabolism, protein folding, metal ion homeostasis, response to stress, carboxylic acid catabolism, and cellular amino acid catabolism. The 48 h:12 h SCPs were enriched into processes including carbohydrate metabolism, protein metabolism, oxidative phosphorylation, and formation of translation ternary structure. A key enzyme for PHB metabolism, poly(R)-hydroxyalkanoic acid synthase (PhaC, KGT44865) accumulated significantly higher in 12 h-culture. Sporulation related proteins SigF and SpoEII were significantly higher in 24 h-samples. Enzymes for nitrate respiration and fermentation accumulated to the highest abundance level in 48 h-culture. CONCLUSIONS Changes in proteome of B. cereus tsu1 during PHB intracellular mobilization were characterized in this study. The key enzyme PhaC for PHB synthesis increased significantly after 12 h-culture which supports the highest PHB accumulation at this time point. The protein abundance level of SpoIIE and SigF also increased, correlating with sporulation in 24 h-culture. Enzymes for nitrate respiration and fermentation were significantly induced in 48 h-culture which indicates the depletion of oxygen at this stage and carbon flow towards fermentative growth. Results from this study provide insights into proteome profile changes during PHB accumulation and reuse, which can be applied to achieve a higher PHB yield and to improve bacterial growth performance and stress resistance.
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Affiliation(s)
- Hui Li
- Department of Agricultural and Environmental Sciences, College of Agriculture, Tennessee State University, 3500 John A. Merritt Blvd, Nashville, TN, 37209, USA
| | - Joshua O'Hair
- Department of Agricultural and Environmental Sciences, College of Agriculture, Tennessee State University, 3500 John A. Merritt Blvd, Nashville, TN, 37209, USA
| | - Santosh Thapa
- Department of Agricultural and Environmental Sciences, College of Agriculture, Tennessee State University, 3500 John A. Merritt Blvd, Nashville, TN, 37209, USA
| | - Sarabjit Bhatti
- Department of Agricultural and Environmental Sciences, College of Agriculture, Tennessee State University, 3500 John A. Merritt Blvd, Nashville, TN, 37209, USA
| | - Suping Zhou
- Department of Agricultural and Environmental Sciences, College of Agriculture, Tennessee State University, 3500 John A. Merritt Blvd, Nashville, TN, 37209, USA.
| | - Yong Yang
- R.W. Holley Center for Agriculture and Health, USDA-ARS, Cornell University, Ithaca, NY, 14853, USA
| | - Tara Fish
- R.W. Holley Center for Agriculture and Health, USDA-ARS, Cornell University, Ithaca, NY, 14853, USA
| | - Theodore W Thannhauser
- R.W. Holley Center for Agriculture and Health, USDA-ARS, Cornell University, Ithaca, NY, 14853, USA
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Wushke S, Froese A, Fristensky B, Zhang XL, Spicer V, Krokhin OV, Levin DB, Sparling R. Genomic comparison of facultatively anaerobic and obligatory aerobic Caldibacillus debilis strains GB1 and Tf helps explain physiological differences. Can J Microbiol 2019; 65:421-428. [PMID: 30694700 DOI: 10.1139/cjm-2018-0464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Caldibacillus debilis strains GB1 and Tf display distinct phenotypes. Caldibacillus debilis GB1 is capable of anaerobic growth and can synthesize ethanol while C. debilis Tf cannot. Comparison of the GB1 and Tf genome sequences revealed that the genomes were highly similar in gene content and showed a high level of synteny. At the genome scale, there were several large sections of DNA that appeared to be from lateral gene transfer into the GB1 genome. Tf did have unique genetic content but at a much smaller scale: 300 genes in Tf verses 857 genes in GB1 that matched at ≤90% sequence similarity. Gene complement and copy number of genes for the glycolysis, tricarboxylic acid cycle, and electron transport chain pathways were identical in both strains. While Tf is an obligate aerobe, it possesses the gene complement for an anaerobic lifestyle (ldh, ak, pta, adhE, pfl). As a species, other strains of C. debilis should be expected to have the potential for anaerobic growth. Assaying the whole cell lysate for alcohol dehydrogenase activity revealed an approximately 2-fold increase in the enzymatic activity in GB1 when compared with Tf.
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Affiliation(s)
- Scott Wushke
- a Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Alan Froese
- a Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Brian Fristensky
- b Department Plant Science, University of Manitoba, Winnipeg, MB R3T 6B3, Canada
| | - Xiang Li Zhang
- b Department Plant Science, University of Manitoba, Winnipeg, MB R3T 6B3, Canada
| | - Victor Spicer
- c Department Physics & Astronomy, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Oleg V Krokhin
- d Department of Internal Medicine & Manitoba Centre for Proteomics and Systems Biology, University of Manitoba, Winnipeg, MB R3A 1R9, Canada
| | - David B Levin
- e Department of Biosystems Engineering, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Richard Sparling
- a Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
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12
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Barth C, Weiss MC, Roettger M, Martin WF, Unden G. Origin and phylogenetic relationships of [4Fe-4S]-containing O 2 sensors of bacteria. Environ Microbiol 2018; 20:4567-4586. [PMID: 30225854 DOI: 10.1111/1462-2920.14411] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Accepted: 09/10/2018] [Indexed: 11/28/2022]
Abstract
The advent of environmental O2 about 2.5 billion years ago forced microbes to metabolically adapt and to develop mechanisms for O2 sensing. Sensing of O2 by [4Fe-4S]2+ to [2Fe-2S]2+ cluster conversion represents an ancient mechanism that is used by FNREc (Escherichia coli), FNRBs (Bacillus subtilis), NreBSa (Staphylococcus aureus) and WhiB3Mt (Mycobacterium tuberculosis). The phylogenetic relationship of these sensors was investigated. FNREc homologues are restricted to the proteobacteria and a few representatives from other phyla. Homologues of FNRBs and NreBSa are located within the bacilli, of WhiB3 within the actinobacteria. Archaea contain no homologues. The data reveal no similarity between the FNREc , FNRBs , NreBSa and WhiB3 sensor families on the sequence and structural levels. These O2 sensor families arose independently in phyla that were already present at the time O2 appeared, their members were subsequently distributed by lateral gene transfer. The chemistry of [4Fe-4S] and [2Fe-2S] cluster formation and interconversion appears to be shared by the sensor protein families. The type of signal output is, however, family specific. The homologues of FNREc and NreBSa vary with regard to the number of Cys residues that coordinate the cluster. It is suggested that the variants derive from lateral gene transfer and gained other functions.
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Affiliation(s)
- C Barth
- Microbiology and Wine Research, Institute for Molecular Physiology, Johannes Gutenberg University Mainz, Mainz, Germany
| | - M C Weiss
- Institute for Molecular Evolution, Heinrich Heine University of Düsseldorf, Düsseldorf, Germany
| | - M Roettger
- Institute for Molecular Evolution, Heinrich Heine University of Düsseldorf, Düsseldorf, Germany
| | - W F Martin
- Institute for Molecular Evolution, Heinrich Heine University of Düsseldorf, Düsseldorf, Germany
| | - G Unden
- Microbiology and Wine Research, Institute for Molecular Physiology, Johannes Gutenberg University Mainz, Mainz, Germany
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13
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Jeßberger N, Rademacher C, Krey VM, Dietrich R, Mohr AK, Böhm ME, Scherer S, Ehling-Schulz M, Märtlbauer E. Simulating Intestinal Growth Conditions Enhances Toxin Production of Enteropathogenic Bacillus cereus. Front Microbiol 2017; 8:627. [PMID: 28446903 PMCID: PMC5388749 DOI: 10.3389/fmicb.2017.00627] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 03/28/2017] [Indexed: 01/17/2023] Open
Abstract
Bacillus cereus is a ubiquitous bacterial pathogen increasingly reported to be the causative agent of foodborne infections and intoxications. Since the enterotoxins linked to the diarrheal form of food poising are foremost produced in the human intestine, the toxic potential of enteropathogenic B. cereus strains is difficult to predict from studies carried out under routine cultivation procedures. In this study, toxigenic properties of a panel of strains (n = 19) of diverse origin were compared using cell culture medium pre-incubated with CaCo-2 cells to mimic intestinal growth conditions. Shortly after contact of the bacteria with the simulated host environment, enterotoxin gene expression was activated and total protein secretion of all strains was accelerated. Although the signal stimulating enterotoxin production still needs to be elucidated, it could be shown that it originated from the CaCo-2 cells. Overall, our study demonstrates that the currently used methods in B. cereus diagnostics, based on standard culture medium, are not allowing a conclusive prediction of the potential health risk related to a certain strain. Thus, these methods should be complemented by cultivation procedures that are simulating intestinal host conditions.
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Affiliation(s)
- Nadja Jeßberger
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität MünchenOberschleißheim, Germany
| | - Corinna Rademacher
- Functional Microbiology, Department of Pathobiology, Institute of Microbiology, University of Veterinary Medicine ViennaVienna, Austria
| | - Viktoria M Krey
- Lehrstuhl für Mikrobielle Ökologie, Zentralinstitut für Ernährungs- und Lebensmittelforschung, Wissenschaftszentrum Weihenstephan, Technische Universität MünchenFreising, Germany
| | - Richard Dietrich
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität MünchenOberschleißheim, Germany
| | - Ann-Katrin Mohr
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität MünchenOberschleißheim, Germany
| | - Maria-Elisabeth Böhm
- Lehrstuhl für Mikrobielle Ökologie, Zentralinstitut für Ernährungs- und Lebensmittelforschung, Wissenschaftszentrum Weihenstephan, Technische Universität MünchenFreising, Germany
| | - Siegfried Scherer
- Lehrstuhl für Mikrobielle Ökologie, Zentralinstitut für Ernährungs- und Lebensmittelforschung, Wissenschaftszentrum Weihenstephan, Technische Universität MünchenFreising, Germany
| | - Monika Ehling-Schulz
- Functional Microbiology, Department of Pathobiology, Institute of Microbiology, University of Veterinary Medicine ViennaVienna, Austria
| | - Erwin Märtlbauer
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität MünchenOberschleißheim, Germany
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14
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Kado T, Kashimoto T, Yamazaki K, Ueno S. Importance of fumarate and nitrate reduction regulatory protein for intestinal proliferation ofVibrio vulnificus. FEMS Microbiol Lett 2016; 364:fnw274. [DOI: 10.1093/femsle/fnw274] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 07/28/2016] [Accepted: 12/02/2016] [Indexed: 11/12/2022] Open
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15
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Duport C, Jobin M, Schmitt P. Adaptation in Bacillus cereus: From Stress to Disease. Front Microbiol 2016; 7:1550. [PMID: 27757102 PMCID: PMC5047918 DOI: 10.3389/fmicb.2016.01550] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 09/15/2016] [Indexed: 12/23/2022] Open
Abstract
Bacillus cereus is a food-borne pathogen that causes diarrheal disease in humans. After ingestion, B. cereus experiences in the human gastro-intestinal tract abiotic physical variables encountered in food, such as acidic pH in the stomach and changing oxygen conditions in the human intestine. B. cereus responds to environmental changing conditions (stress) by reversibly adjusting its physiology to maximize resource utilization while maintaining structural and genetic integrity by repairing and minimizing damage to cellular infrastructure. As reviewed in this article, B. cereus adapts to acidic pH and changing oxygen conditions through diverse regulatory mechanisms and then exploits its metabolic flexibility to grow and produce enterotoxins. We then focus on the intricate link between metabolism, redox homeostasis, and enterotoxins, which are recognized as important contributors of food-borne disease.
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Affiliation(s)
- Catherine Duport
- Sécurité et Qualité des Produits d'Origine Végétale, UMR0408, Avignon Université, Institut National de la Recherche Agronomique Avignon, France
| | - Michel Jobin
- Sécurité et Qualité des Produits d'Origine Végétale, UMR0408, Avignon Université, Institut National de la Recherche Agronomique Avignon, France
| | - Philippe Schmitt
- Sécurité et Qualité des Produits d'Origine Végétale, UMR0408, Avignon Université, Institut National de la Recherche Agronomique Avignon, France
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16
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Wallace N, Zani A, Abrams E, Sun Y. The Impact of Oxygen on Bacterial Enteric Pathogens. ADVANCES IN APPLIED MICROBIOLOGY 2016; 95:179-204. [PMID: 27261784 DOI: 10.1016/bs.aambs.2016.04.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Bacterial enteric pathogens are responsible for a tremendous amount of foodborne illnesses every year through the consumption of contaminated food products. During their transit from contaminated food sources to the host gastrointestinal tract, these pathogens are exposed and must adapt to fluctuating oxygen levels to successfully colonize the host and cause diseases. However, the majority of enteric infection research has been conducted under aerobic conditions. To raise awareness of the importance in understanding the impact of oxygen, or lack of oxygen, on enteric pathogenesis, we describe in this review the metabolic and physiological responses of nine bacterial enteric pathogens exposed to environments with different oxygen levels. We further discuss the effects of oxygen levels on virulence regulation to establish potential connections between metabolic adaptations and bacterial pathogenesis. While not providing an exhaustive list of all bacterial pathogens, we highlight key differences and similarities among nine facultative anaerobic and microaerobic pathogens in this review to argue for a more in-depth understanding of the diverse impact oxygen levels have on enteric pathogenesis.
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Affiliation(s)
- N Wallace
- University of Dayton, Dayton, OH, United States
| | - A Zani
- University of Dayton, Dayton, OH, United States
| | - E Abrams
- University of Dayton, Dayton, OH, United States
| | - Y Sun
- University of Dayton, Dayton, OH, United States
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17
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Kilcullen K, Teunis A, Popova TG, Popov SG. Cytotoxic Potential of Bacillus cereus Strains ATCC 11778 and 14579 Against Human Lung Epithelial Cells Under Microaerobic Growth Conditions. Front Microbiol 2016; 7:69. [PMID: 26870026 PMCID: PMC4735842 DOI: 10.3389/fmicb.2016.00069] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 01/14/2016] [Indexed: 12/28/2022] Open
Abstract
Bacillus cereus, a food poisoning bacterium closely related to Bacillus anthracis, secretes a multitude of virulence factors including enterotoxins, hemolysins, and phospholipases. However, the majority of the in vitro experiments evaluating the cytotoxic potential of B. cereus were carried out in the conditions of aeration, and the impact of the oxygen limitation in conditions encountered by the microbe in natural environment such as gastrointestinal tract remains poorly understood. This research reports comparative analysis of ATCC strains 11778 (BC1) and 14579 (BC2) in aerobic and microaerobic (static) cultures with regard to their toxicity for human lung epithelial cells. We showed that BC1 increased its toxicity upon oxygen limitation while BC2 was highly cytotoxic in both growth conditions. The combined effect of the pore-forming, cholesterol-dependent hemolysin, cereolysin O (CLO), and metabolic product(s) such as succinate produced in microaerobic conditions provided substantial contribution to the toxicity of BC1 but not BC2 which relied mainly on other toxins. This mechanism is shared between CB1 and B. anthracis. It involves the permeabilization of the cell membrane which facilitates transport of toxic bacterial metabolites into the cell. The toxicity of BC1 was potentiated in the presence of bovine serum albumin which appeared to serve as reservoir for bacteria-derived nitric oxide participating in the downstream production of reactive oxidizing species with the properties of peroxynitrite. In agreement with this the BC1 cultures demonstrated the increased oxidation of the indicator dye Amplex Red catalyzed by peroxidase as well as the increased toxicity in the presence of externally added ascorbic acid.
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Affiliation(s)
| | - Allison Teunis
- School of Systems Biology, George Mason University Manassas, VA, USA
| | - Taissia G Popova
- School of Systems Biology, George Mason University Manassas, VA, USA
| | - Serguei G Popov
- School of Systems Biology, George Mason University Manassas, VA, USA
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18
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Omer H, Alpha-Bazin B, Brunet JL, Armengaud J, Duport C. Proteomics identifies Bacillus cereus EntD as a pivotal protein for the production of numerous virulence factors. Front Microbiol 2015; 6:1004. [PMID: 26500610 PMCID: PMC4595770 DOI: 10.3389/fmicb.2015.01004] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Accepted: 09/07/2015] [Indexed: 11/13/2022] Open
Abstract
Bacillus cereus is a Gram-positive pathogen that causes a wide variety of diseases in humans. It secretes into the extracellular milieu proteins that may contribute directly or indirectly to its virulence. EntD is a novel exoprotein identified by proteogenomics of B. cereus ATCC 14579. We constructed a ΔentD mutant and analyzed the impact of entD disruption on the cellular proteome and exoproteome isolated from early, late, and stationary-phase cultures. We identified 308 and 79 proteins regulated by EntD in the cellular proteome and the exoproteome, respectively. The contribution of these proteins to important virulence-associated functions, including central metabolism, cell structure, antioxidative ability, cell motility, and toxin production, are presented. The proteomic data were correlated with the growth defect, cell morphology change, reduced motility, and reduced cytotoxicity of the ΔentD mutant strain. We conclude that EntD is an important player in B. cereus virulence. The function of EntD and the putative EntD-dependent regulatory network are discussed. To our knowledge, this study is the first characterization of an Ent family protein in a species of the B. cereus group.
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Affiliation(s)
- Hélène Omer
- Université d'Avignon et des Pays de Vaucluse, UMR408 Sécurité et Qualité des Produits d'Origine Végétale Avignon, France ; INRA, UMR408 Sécurité et Qualité des Produits d'Origine Végétale Avignon, France ; CEA-Marcoule, DSV/IBITEC-S/SPI/Li2D, Laboratory "Innovative technologies for Detection and Diagnostic" Bagnols-sur-Cèze, France
| | - Béatrice Alpha-Bazin
- CEA-Marcoule, DSV/IBITEC-S/SPI/Li2D, Laboratory "Innovative technologies for Detection and Diagnostic" Bagnols-sur-Cèze, France
| | | | - Jean Armengaud
- CEA-Marcoule, DSV/IBITEC-S/SPI/Li2D, Laboratory "Innovative technologies for Detection and Diagnostic" Bagnols-sur-Cèze, France
| | - Catherine Duport
- Université d'Avignon et des Pays de Vaucluse, UMR408 Sécurité et Qualité des Produits d'Origine Végétale Avignon, France ; INRA, UMR408 Sécurité et Qualité des Produits d'Origine Végétale Avignon, France
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19
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Popova TG, Teunis A, Vaseghi H, Zhou W, Espina V, Liotta LA, Popov SG. Nitric oxide as a regulator of B. anthracis pathogenicity. Front Microbiol 2015; 6:921. [PMID: 26388860 PMCID: PMC4557104 DOI: 10.3389/fmicb.2015.00921] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 08/21/2015] [Indexed: 12/18/2022] Open
Abstract
Nitric oxide (NO) is a key physiological regulator in eukaryotic and prokaryotic organisms. It can cause a variety of biological effects by reacting with its targets or/and indirectly inducing oxidative stress. NO can also be produced by bacteria including the pathogenic Bacillus anthracis; however, its role in the infectious process only begins to emerge. NO incapacitates macrophages by S-nitrosylating the intracellular proteins and protects B. anthracis from oxidative stress. It is also implicated in the formation of toxic peroxynitrite. In this study we further assessed the effects of B. anthracis NO produced by the NO synthase (bNOS) on bacterial metabolism and host cells in experiments with the bNOS knockout Sterne strain. The mutation abrogated accumulation of nitrite and nitrate as tracer products of NO in the culture medium and markedly attenuated growth in both aerobic and microaerobic conditions. The regulatory role of NO was also suggested by the abnormally high rate of nitrate denitrification by the mutant in the presence of oxygen. Anaerobic regulation mediated by NO was reflected in reduced fermentation of glucose by the mutant correlating with the reduced toxicity of bacteria toward host cells in culture. The toxic effect of NO required permeabilization of the target cells as well as the activity of fermentation-derived metabolite in the conditions of reduced pH. The host cells demonstrated increased phosphorylation of major survivor protein kinase AKT correlating with reduced toxicity of the mutant in comparison with Sterne. Our global proteomic analysis of lymph from the lymph nodes of infected mice harboring bacteria revealed numerous changes in the pattern and levels of proteins associated with the activity of bNOS influencing key cell physiological processes relevant to energy metabolism, growth, signal transduction, stress response, septic shock, and homeostasis. This is the first in vivo observation of the bacterial NO effect on the lymphatic system.
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Affiliation(s)
- Taissia G Popova
- National Center for Biodefense and Infectious Disease, College of Science, George Mason University, Manassas, VA USA ; Center for Applied Proteomics and Molecular Medicine, College of Science, George Mason University, Manassas, VA USA
| | - Allison Teunis
- Center for Applied Proteomics and Molecular Medicine, College of Science, George Mason University, Manassas, VA USA
| | - Haley Vaseghi
- University of North Carolina at Chapel Hill, Chapel Hill, NC USA
| | - Weidong Zhou
- Center for Applied Proteomics and Molecular Medicine, College of Science, George Mason University, Manassas, VA USA
| | - Virginia Espina
- Center for Applied Proteomics and Molecular Medicine, College of Science, George Mason University, Manassas, VA USA
| | - Lance A Liotta
- Center for Applied Proteomics and Molecular Medicine, College of Science, George Mason University, Manassas, VA USA
| | - Serguei G Popov
- National Center for Biodefense and Infectious Disease, College of Science, George Mason University, Manassas, VA USA
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20
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Jeßberger N, Krey VM, Rademacher C, Böhm ME, Mohr AK, Ehling-Schulz M, Scherer S, Märtlbauer E. From genome to toxicity: a combinatory approach highlights the complexity of enterotoxin production in Bacillus cereus. Front Microbiol 2015; 6:560. [PMID: 26113843 PMCID: PMC4462024 DOI: 10.3389/fmicb.2015.00560] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 05/21/2015] [Indexed: 01/30/2023] Open
Abstract
In recent years Bacillus cereus has gained increasing importance as a food poisoning pathogen. It is the eponymous member of the B. cereus sensu lato group that consists of eight closely related species showing impressive diversity of their pathogenicity. The high variability of cytotoxicity and the complex regulatory network of enterotoxin expression have complicated efforts to predict the toxic potential of new B. cereus isolates. In this study, comprehensive analyses of enterotoxin gene sequences, transcription, toxin secretion and cytotoxicity were performed. For the first time, these parameters were compared in a whole set of B. cereus strains representing isolates of different origin (food or food poisoning outbreaks) and of different toxic potential (enteropathogenic and apathogenic) to elucidate potential starting points of strain-specific differential toxicity. While toxin gene sequences were highly conserved and did not allow for differentiation between high and low toxicity strains, comparison of nheB and hblD enterotoxin gene transcription and Nhe and Hbl protein titers revealed not only strain-specific differences but also incongruence between toxin gene transcripts and toxin protein levels. With one exception all strains showed comparable capability of protein secretion and so far, no secretion patterns specific for high and low toxicity strains were identified. These results indicate that enterotoxin expression is more complex than expected, possibly involving the orchestrated interplay of different transcriptional regulator proteins, as well as posttranscriptional and posttranslational regulatory mechanisms plus additional influences of environmental conditions.
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Affiliation(s)
- Nadja Jeßberger
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München Oberschleißheim, Germany
| | - Viktoria M Krey
- Lehrstuhl für Mikrobielle Ökologie, Zentralinstitut für Ernährungs- und Lebensmittelforschung, Wissenschaftszentrum Weihenstephan, Technische Universität München Freising, Germany
| | - Corinna Rademacher
- Functional Microbiology, Department of Pathobiology, Institute of Microbiology, University of Veterinary Medicine Vienna Vienna, Austria
| | - Maria-Elisabeth Böhm
- Lehrstuhl für Mikrobielle Ökologie, Zentralinstitut für Ernährungs- und Lebensmittelforschung, Wissenschaftszentrum Weihenstephan, Technische Universität München Freising, Germany
| | - Ann-Katrin Mohr
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München Oberschleißheim, Germany
| | - Monika Ehling-Schulz
- Functional Microbiology, Department of Pathobiology, Institute of Microbiology, University of Veterinary Medicine Vienna Vienna, Austria
| | - Siegfried Scherer
- Lehrstuhl für Mikrobielle Ökologie, Zentralinstitut für Ernährungs- und Lebensmittelforschung, Wissenschaftszentrum Weihenstephan, Technische Universität München Freising, Germany
| | - Erwin Märtlbauer
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München Oberschleißheim, Germany
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21
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Facultative Anaerobe Caldibacillus debilis GB1: Characterization and Use in a Designed Aerotolerant, Cellulose-Degrading Coculture with Clostridium thermocellum. Appl Environ Microbiol 2015; 81:5567-73. [PMID: 26048931 DOI: 10.1128/aem.00735-15] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 06/03/2015] [Indexed: 11/20/2022] Open
Abstract
Development of a designed coculture that can achieve aerotolerant ethanogenic biofuel production from cellulose can reduce the costs of maintaining anaerobic conditions during industrial consolidated bioprocessing (CBP). To this end, a strain of Caldibacillus debilis isolated from an air-tolerant cellulolytic consortium which included a Clostridium thermocellum strain was characterized and compared with the C. debilis type strain. Characterization of isolate C. debilis GB1 and comparisons with the type strain of C. debilis revealed significant physiological differences, including (i) the absence of anaerobic metabolism in the type strain and (ii) different end product synthesis profiles under the experimental conditions used. The designed cocultures displayed unique responses to oxidative conditions, including an increase in lactate production. We show here that when the two species were cultured together, the noncellulolytic facultative anaerobe C. debilis GB1 provided respiratory protection for C. thermocellum, allowing the synergistic utilization of cellulose even under an aerobic atmosphere.
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22
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Abstract
Iron-sulfur clusters act as important cofactors for a number of transcriptional regulators in bacteria, including many mammalian pathogens. The sensitivity of iron-sulfur clusters to iron availability, oxygen tension, and reactive oxygen and nitrogen species enables bacteria to use such regulators to adapt their gene expression profiles rapidly in response to changing environmental conditions. In this review, we discuss how the [4Fe-4S] or [2Fe-2S] cluster-containing regulators FNR, Wbl, aconitase, IscR, NsrR, SoxR, and AirSR contribute to bacterial pathogenesis through control of both metabolism and classical virulence factors. In addition, we briefly review mammalian iron homeostasis as well as oxidative/nitrosative stress to provide context for understanding the function of bacterial iron-sulfur cluster sensors in different niches within the host.
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Affiliation(s)
- Halie K Miller
- Department of Microbiology and Environmental Toxicology, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA.
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23
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Madeira JP, Alpha-Bazin B, Armengaud J, Duport C. Time dynamics of the Bacillus cereus exoproteome are shaped by cellular oxidation. Front Microbiol 2015; 6:342. [PMID: 25954265 PMCID: PMC4406070 DOI: 10.3389/fmicb.2015.00342] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 04/07/2015] [Indexed: 01/18/2023] Open
Abstract
At low density, Bacillus cereus cells release a large variety of proteins into the extracellular medium when cultivated in pH-regulated, glucose-containing minimal medium, either in the presence or absence of oxygen. The majority of these exoproteins are putative virulence factors, including toxin-related proteins. Here, B. cereus exoproteome time courses were monitored by nanoLC-MS/MS under low-oxidoreduction potential (ORP) anaerobiosis, high-ORP anaerobiosis, and aerobiosis, with a specific focus on oxidative-induced post-translational modifications of methionine residues. Principal component analysis (PCA) of the exoproteome dynamics indicated that toxin-related proteins were the most representative of the exoproteome changes, both in terms of protein abundance and their methionine sulfoxide (Met(O)) content. PCA also revealed an interesting interconnection between toxin-, metabolism-, and oxidative stress-related proteins, suggesting that the abundance level of toxin-related proteins, and their Met(O) content in the B. cereus exoproteome, reflected the cellular oxidation under both aerobiosis and anaerobiosis.
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Affiliation(s)
- Jean-Paul Madeira
- UMR408, Sécurité et Qualité des Produits d'Origine Végétale, Université d'Avignon Avignon, France ; INRA, UMR408, Sécurité et Qualité des Produits d' Origine Végétale Avignon, France ; Commissariat à l'énergie Atomique et aux Énergies Alternatives (CEA), Direction des Sciences du Vivant (DSV), IBEB, Li2D Bagnols sur Cèze, France
| | - Béatrice Alpha-Bazin
- Commissariat à l'énergie Atomique et aux Énergies Alternatives (CEA), Direction des Sciences du Vivant (DSV), IBEB, Li2D Bagnols sur Cèze, France
| | - Jean Armengaud
- Commissariat à l'énergie Atomique et aux Énergies Alternatives (CEA), Direction des Sciences du Vivant (DSV), IBEB, Li2D Bagnols sur Cèze, France
| | - Catherine Duport
- UMR408, Sécurité et Qualité des Produits d'Origine Végétale, Université d'Avignon Avignon, France ; INRA, UMR408, Sécurité et Qualité des Produits d' Origine Végétale Avignon, France
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24
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Berthold-Pluta A, Pluta A, Garbowska M. The effect of selected factors on the survival of Bacillus cereus in the human gastrointestinal tract. Microb Pathog 2015; 82:7-14. [PMID: 25794697 DOI: 10.1016/j.micpath.2015.03.015] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 10/17/2014] [Accepted: 03/09/2015] [Indexed: 12/29/2022]
Abstract
Bacillus cereus is a Gram-positive bacterium widely distributed in soil and vegetation. This bacterial species can also contaminate raw or processed foods. Pathogenic B. cereus strains can cause a range of infections in humans, as well as food poisoning of an emetic (intoxication) or diarrheal type (toxico-infection). Toxico-infections are due to the action of the Hbl toxin, Nhe toxin, and cytotoxin K produced by the microorganism in the gastrointestinal tract. This occurs once the spores or vegetative B. cereus cells survive the pH barrier of the stomach and reach the small intestine where they produce toxins in sufficient amounts. This article discusses the effect of various factors on the survival of B. cereus in the gastrointestinal tract, including low pH and the presence of digestive enzymes in the stomach, bile salts in the small intestine, and indigenous microflora in the lower parts of the gastrointestinal tract. Additional aspects also reported to affect B. cereus survival and virulence in the gastrointestinal tract include the interaction of the spores and vegetative cells with enterocytes. In vitro studies revealed that both vegetative B. cereus and spores can survive in the gastrointestinal tract suggesting that the biological form of the microorganism may have less influence on the occurrence of the symptoms of infection than was once believed. It is most likely the interaction between the pathogen and enterocytes that is necessary for the diarrheal form of B. cereus food poisoning to develop. The adhesion of B. cereus to the intestinal epithelium allows the bacterium to grow and produce enterotoxins in the proximity of the epithelium. Recent studies suggest that the human intestinal microbiota inhibits the growth of vegetative B. cereus cells considerably.
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Affiliation(s)
- Anna Berthold-Pluta
- Division of Milk Biotechnology, Department of Biotechnology, Microbiology and Food Evaluation, Faculty of Food Sciences, Warsaw University of Life Sciences - SGGW, Nowoursynowska 159C St, 02-787 Warsaw, Poland.
| | - Antoni Pluta
- Division of Milk Biotechnology, Department of Biotechnology, Microbiology and Food Evaluation, Faculty of Food Sciences, Warsaw University of Life Sciences - SGGW, Nowoursynowska 159C St, 02-787 Warsaw, Poland
| | - Monika Garbowska
- Prof. Wacław Dąbrowski Institute of Agricultural and Food Biotechnology, Inter-Department Problem Group for Dairy Industries, Rakowiecka St 36, 02-532 Warsaw, Poland
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25
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Laouami S, Clair G, Armengaud J, Duport C. Proteomic evidences for rex regulation of metabolism in toxin-producing Bacillus cereus ATCC 14579. PLoS One 2014; 9:e107354. [PMID: 25216269 PMCID: PMC4162614 DOI: 10.1371/journal.pone.0107354] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Accepted: 08/14/2014] [Indexed: 01/07/2023] Open
Abstract
The facultative anaerobe, Bacillus cereus, causes diarrheal diseases in humans. Its ability to deal with oxygen availability is recognized to be critical for pathogenesis. The B. cereus genome comprises a gene encoding a protein with high similarities to the redox regulator, Rex, which is a central regulator of anaerobic metabolism in Bacillus subtilis and other Gram-positive bacteria. Here, we showed that B. cereus rex is monocistronic and down-regulated in the absence of oxygen. The protein encoded by rex is an authentic Rex transcriptional factor since its DNA binding activity depends on the NADH/NAD+ ratio. Rex deletion compromised the ability of B. cereus to cope with external oxidative stress under anaerobiosis while increasing B. cereus resistance against such stress under aerobiosis. The deletion of rex affects anaerobic fermentative and aerobic respiratory metabolism of B. cereus by decreasing and increasing, respectively, the carbon flux through the NADH-recycling lactate pathway. We compared both the cellular proteome and exoproteome of the wild-type and Δrex cells using a high throughput shotgun label-free quantitation approach and identified proteins that are under control of Rex-mediated regulation. Proteomics data have been deposited to the ProteomeXchange with identifier PXD000886. The data suggest that Rex regulates both the cross-talk between metabolic pathways that produce NADH and NADPH and toxinogenesis, especially in oxic conditions.
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Affiliation(s)
- Sabrina Laouami
- Avignon Université/INRA, SQPOV UMR408, Avignon, France
- INRA, SQPOV UMR408, Avignon, France
| | - Géremy Clair
- Avignon Université/INRA, SQPOV UMR408, Avignon, France
- INRA, SQPOV UMR408, Avignon, France
- Laboratoire de Biochimie des Systèmes Perturbés, CEA Marcoule, DSV-iBEB-SBTN-LBSP, Bagnols-sur-Cèze, France
| | - Jean Armengaud
- Laboratoire de Biochimie des Systèmes Perturbés, CEA Marcoule, DSV-iBEB-SBTN-LBSP, Bagnols-sur-Cèze, France
| | - Catherine Duport
- Avignon Université/INRA, SQPOV UMR408, Avignon, France
- INRA, SQPOV UMR408, Avignon, France
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Clair G, Lorphelin A, Armengaud J, Duport C. OhrRA functions as a redox-responsive system controlling toxinogenesis in Bacillus cereus. J Proteomics 2013; 94:527-39. [PMID: 24184231 DOI: 10.1016/j.jprot.2013.10.024] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Revised: 09/24/2013] [Accepted: 10/18/2013] [Indexed: 01/01/2023]
Abstract
UNLABELLED Bacillus cereus OhrR is a member of the subgroup of the MarR (multiple antibiotic resistance) family of transcriptional regulators that use a cysteine-based redox sensing mechanism. OhrA is a thiol-dependent, peroxidase-like protein. The dual OhrRA system triggers B. cereus adaptation in response to redox changes, such as those encountered in the environment of the gastrointestinal tract. Here, we investigated the role of OhrRA in toxinogenesis. Comparative shotgun analysis of exoproteomes from ∆ohrA, ∆ohrR and wild-type cells revealed significant changes in the abundance levels of toxin-related proteins depending on the extracellular redox potential. We complemented these data by measuring the DNA binding activity of reduced and oxidized recombinant OhrR on toxin and putative toxin promoter regions. Furthermore, transcriptomic data and OhrRA-dependent, antiproliferative activity of the B. cereus exoproteome on Caco-2 human epithelial cells were recorded. The results indicate that OhrR controlled toxin gene expression directly or indirectly in a redox- and toxin-dependent manner, and may function as a repressor or an activator. Moreover, we found that OhrR restricts toxin-dependent antiproliferative activity of the B. cereus exoproteome whatever the growth conditions, while the restrictive impact of OhrA occurs only under low ORP anoxic conditions. BIOLOGICAL SIGNIFICANCE B. cereus is a notorious foodborne pathogen which causes gastroenteritis. Fatal and severe cases have been reported. The pathogenicity of B. cereus is intimately associated with the production of epithelial cell-destructive toxins in the small intestine. The small intestine poses several challenges for a pathogen because it is sliced into various niches with different oxygen concentrations and different redox potentials. We recently showed that the organic hydroperoxide resistance OhrRA system was crucial to the successful adaptation of B. cereus to extreme redox environments such as those encountered in the lumen (high reducing anoxic environment) and on the intestinal epithelium (transient oxic environment). Here we provide evidence that this bacterial system is a major virulence determinant in B. cereus in that it coordinates toxinogenesis in a redox dependent manner. Specifically, our comparative exoproteomic analyses reveal that OhrR strongly restricts B. cereus toxinogenesis under high reducing anoxic conditions while OhrA boosts toxinogenesis. Based on exoproteomic analyses, we further examined the role of OhrR and found that it functions as a redox-dependent transcriptional regulator of toxin and putative toxin genes. These findings provide novel insights into the weapons used by B. cereus to control its toxinogenic potential and, as a result its toxicity against human epithelial cells.
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Affiliation(s)
- Gérémy Clair
- Université d'Avignon et des Pays de Vaucluse, UMR408, Sécurité et Qualité des Produits d'Origine Végétale, F-84000 Avignon, France; INRA, UMR408, Sécurité et Qualité des Produits d'Origine Végétale, F-84914 Avignon, France; Laboratoire de Biochimie des Systèmes Perturbés, CEA Marcoule, DSV-iBEB-SBTN-LBSP, F-30207 Bagnols-sur-Cèze cedex, France
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de Sarrau B, Clavel T, Zwickel N, Despres J, Dupont S, Beney L, Tourdot-Maréchal R, Nguyen-The C. Unsaturated fatty acids from food and in the growth medium improve growth of Bacillus cereus under cold and anaerobic conditions. Food Microbiol 2013; 36:113-22. [PMID: 24010589 DOI: 10.1016/j.fm.2013.04.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Revised: 03/12/2013] [Accepted: 04/15/2013] [Indexed: 11/17/2022]
Abstract
In a chemically defined medium and in Luria broth, cold strongly reduced maximal population density of Bacillus cereus ATCC 14579 in anaerobiosis and caused formation of filaments. In cooked spinach, maximal population density of B. cereus in anaerobiosis was the same at cold and optimal temperatures, with normal cell divisions. The lipid containing fraction of spinach, but not the hydrophilic fraction, restored growth of B. cereus under cold and anaerobiosis when added to the chemically defined medium. This fraction was rich in unsaturated, low melting point fatty acids. Addition of phosphatidylcholine containing unsaturated, low melting point, fatty acids similarly improved B. cereus anaerobic growth at cold temperature. Addition of hydrogenated phosphatidylcholine containing saturated, high melting point, fatty acids did not modify growth. Fatty acids from phospholipids, from spinach and from hydrogenated phosphatidylcholine, although normally very rare in B. cereus, were inserted in the bacterium membrane. Addition of phospholipids rich in unsaturated fatty acids to cold and anaerobic cultures, increased fluidity of B. cereus membrane lipids, to the same level as those from B. cereus normally cold adapted, i.e. grown aerobically at 15 °C. B. cereus is therefore able to use external fatty acids from foods or from the growth medium to adapt its membrane to cold temperature under anaerobiosis, and to recover the maximal population density achieved at optimal temperature.
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Affiliation(s)
- Benoît de Sarrau
- INRA, UMR408 Sécurité et Qualité des Produits d'Origine Végétale, F-84000 Avignon, France
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Ceuppens S, Boon N, Uyttendaele M. Diversity of Bacillus cereus group strains is reflected in their broad range of pathogenicity and diverse ecological lifestyles. FEMS Microbiol Ecol 2013; 84:433-50. [PMID: 23488744 DOI: 10.1111/1574-6941.12110] [Citation(s) in RCA: 125] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Revised: 03/06/2013] [Accepted: 03/06/2013] [Indexed: 12/25/2022] Open
Abstract
Bacillus cereus comprises a highly versatile group of bacteria, which are of particular interest because of their capacity to cause disease. Emetic food poisoning is caused by the toxin cereulide produced during the growth of emetic B. cereus in food, while diarrhoeal food poisoning is the result of enterotoxin production by viable vegetative B. cereus cells in the small intestine, probably in the mucus layer and/or attached to the host's intestinal epithelium. The numbers of B. cereus causing disease are highly variable, depending on diverse factors linked to the host (age, diet, physiology and immunology), bacteria (cellular form, toxin genes and expression) and food (nutritional composition and meal characteristics). Bacillus cereus group strains show impressive ecological diversity, ranging from their saprophytic life cycle in soil to symbiotic (commensal and mutualistic) lifestyles near plant roots and in guts of insects and mammals to various pathogenic ones in diverse insect and mammalian hosts. During all these different ecological lifestyles, their toxins play important roles ranging from providing competitive advantages within microbial communities to inhibition of specific pathogenic organisms for their host and accomplishment of infections by damaging their host's tissues.
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Affiliation(s)
- Siele Ceuppens
- Laboratory of Food Microbiology and Food Preservation, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium.
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Ignatova M, Guével B, Com E, Haddad N, Rossero A, Bogard P, Prévost H, Guillou S. Two-dimensional fluorescence difference gel electrophoresis analysis of Listeria monocytogenes submitted to a redox shock. J Proteomics 2013. [DOI: 10.1016/j.jprot.2012.11.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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de Sarrau B, Clavel T, Bornard I, Nguyen-the C. Low temperatures and fermentative metabolism limit peptidoglycan digestion of Bacillus cereus. Impact on colony forming unit counts. Food Microbiol 2012. [PMID: 23200654 DOI: 10.1016/j.fm.2012.09.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The impact of fermentative metabolism at low temperature on cell division of Bacillus cereus was studied. Fermentation at 37 °C had no influence on the division of bacteria. Aerobic cultures at 15 °C produced larger cells than at 37 °C, but cell division was normal. In fermentative cultures at 15 °C, no increase in CFU ml(-1) was observed. However, A(600) increased, due to formation of long filaments. Transmission electronic microscopy and light microscopy with fluorescent staining showed several nucleic acid entities separated by a hydrophobic membrane, indicating that each filament contained several individual cells attached by peptidoglycan. When left in air at room temperature, one filament gave several daughter cells, this means that one CFU formed by one filament may represent a greater contamination potential than one CFU formed by a single cell. Division was observed in cultures at 15 °C with anaerobic respiration in the presence of nitrates. Possible filamentous growth must thus be taken into account to avoid underestimating B. cereus growth in vacuum or modified atmosphere packaged foods stored at low temperature.
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Affiliation(s)
- Benoît de Sarrau
- INRA, UMR408 Sécurité et Qualité des Produits d'Origine Végétale, F-84000 Avignon, France.
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Esbelin J, Jouanneau Y, Duport C. Bacillus cereus Fnr binds a [4Fe-4S] cluster and forms a ternary complex with ResD and PlcR. BMC Microbiol 2012; 12:125. [PMID: 22731107 PMCID: PMC3520743 DOI: 10.1186/1471-2180-12-125] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2012] [Accepted: 06/11/2012] [Indexed: 11/15/2022] Open
Abstract
Background Bacillus cereus is a facultative anaerobe that causes diarrheal disease in humans. Diarrheal syndrome may result from the secretion of various virulence factors including hemolysin BL and nonhemolytic enterotoxin Nhe. Expression of genes encoding Hbl and Nhe is regulated by the two redox systems, ResDE and Fnr, and the virulence regulator PlcR. B. cereus Fnr is a member of the Crp/Fnr family of iron-sulfur (Fe-S) proteins. Only its apo-form has so far been studied. A major goal in deciphering the Fnr-dependent regulation of enterotoxin genes is thus to obtain and characterize holoFnr. Results Fnr has been subjected to in vitro Fe-S cluster reconstitution under anoxic conditions. UV-visible and EPR spectroscopic analyses together with the chemical estimation of the iron content indicated that Fnr binds one [4Fe-4S]2+ cluster per monomer. Atmospheric O2 causes disassembly of the Fe-S cluster, which exhibited a half-life of 15 min in air. Holo- and apoFnr have similar affinities for the nhe and hbl promoter regions, while holoFnr has a higher affinity for fnr promoter region than apoFnr. Both the apo- and holo-form of Fnr interact with ResD and PlcR to form a ternary complex. Conclusions Overall, this work shows that incorporation of the [4Fe-4S]2+ cluster is not required for DNA binding of Fnr to promoter regions of hbl and nhe enterotoxin genes or for the formation of a ternary complex with ResD and PlcR. This points to some new unusual properties of Fnr that may have physiological relevance in the redox regulation of enterotoxin gene regulation.
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Affiliation(s)
- Julia Esbelin
- Université d'Avignon et des Pays de Vaucluse, UMR408, Sécurité et Qualité des Produits d'Origine Végétale, F-84000, Avignon, France
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de Sarrau B, Clavel T, Clerté C, Carlin F, Giniès C, Nguyen-The C. Influence of anaerobiosis and low temperature on Bacillus cereus growth, metabolism, and membrane properties. Appl Environ Microbiol 2012; 78:1715-23. [PMID: 22247126 PMCID: PMC3298147 DOI: 10.1128/aem.06410-11] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Accepted: 01/02/2012] [Indexed: 02/02/2023] Open
Abstract
The impact of simultaneous anaerobiosis and low temperature on growth parameters, metabolism, and membrane properties of Bacillus cereus ATCC 14579 was studied. No growth was observed under anaerobiosis at 12°C. In bioreactors, growth rates and biomass production were drastically reduced by simultaneous anaerobiosis and low temperature (15°C). The two conditions had a synergistic effect on biomass reduction. In anaerobic cultures, fermentative metabolism was modified by low temperature, with a marked reduction in ethanol production leading to a lower ability to produce NAD(+). Anaerobiosis reduced unsaturated fatty acids at both low optimal temperatures. In addition, simultaneous anaerobiosis and low temperatures markedly reduced levels of branched-chain fatty acids compared to all other conditions (accounting for 33% of total fatty acids against more 71% for low-temperature aerobiosis, optimal-temperature aerobiosis, and optimal-temperature anaerobiosis). This corresponded to high-melting-temperature lipids and to low-fluidity membranes, as indicated by differential scanning calorimetry, 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence anisotropy, and infrared spectroscopy. This is in contrast to requirements for cold adaptation. A link between modification in the synthesis of metabolites of fermentative metabolism and the reduction of branched-chain fatty acids at low temperature under anaerobiosis, through a modification of the oxidizing capacity, is assumed. This link may partly explain the impact of low temperature and anaerobiosis on membrane properties and growth performance.
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Affiliation(s)
- Benoît de Sarrau
- INRA, UMR408 Sécurité et Qualité des Produits d’Origine Végétale, Avignon, France.
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Clair G, Armengaud J, Duport C. Restricting fermentative potential by proteome remodeling: an adaptive strategy evidenced in Bacillus cereus. Mol Cell Proteomics 2012; 11:M111.013102. [PMID: 22232490 DOI: 10.1074/mcp.m111.013102] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Pathogenesis hinges on successful colonization of the gastrointestinal (GI) tract by pathogenic facultative anaerobes. The GI tract is a carbohydrate-limited environment with varying oxygen availability and oxidoreduction potential (ORP). How pathogenic bacteria are able to adapt and grow in these varying conditions remains a key fundamental question. Here, we designed a system biology-inspired approach to pinpoint the key regulators allowing Bacillus cereus to survive and grow efficiently under low ORP anoxic conditions mimicking those encountered in the intestinal lumen. We assessed the proteome components using high throughput nanoLC-MS/MS techniques, reconstituted the main metabolic circuits, constructed ΔohrA and ΔohrR mutants, and analyzed the impacts of ohrA and ohrR disruptions by a novel round of shotgun proteomics. Our study revealed that OhrR and OhrA are crucial to the successful adaptation of B. cereus to the GI tract environment. Specifically, we showed that B. cereus restricts its fermentative growth under low ORP anaerobiosis and sustains efficient aerobic respiratory metabolism, motility, and stress response via OhrRA-dependent proteome remodeling. Finally, our results introduced a new adaptive strategy where facultative anaerobes prefer to restrict their fermentative potential for a long term benefit.
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Affiliation(s)
- Gérémy Clair
- Université d'Avignon et des Pays de Vaucluse, UMR408, Sécurité et Qualité des Produits d'Origine Végétale, F-84000 Avignon, France
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[Analyze and compare metabolic pathways of Bacillus cereus group]. YI CHUAN = HEREDITAS 2011; 33:1057-66. [PMID: 21993280 DOI: 10.3724/sp.j.1005.2011.01057] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A large number of data and information was obtained from genome sequencing and high-throughput genomic studies, use of the information to study metabolic networks become a new hotspot in biological research. This article compared different methods to reconstruct metabolic networks and analyzed the advantages and disadvantages of each methods, and then introduced some researches about carbohydrate metabolism pathways, amino acid metabolic pathways, and energy metabolism pathways of 9 strains of Bacillus cereus, 6 strains of B. anthracis,,6 strain of B. thuringiensis, and finds out their similarities and characteristics. These three strains have some necessary metabolic pathways, such as glycolysis, tri-carboxylic acid cycle, alanine metabolism, histidine metabolism, and energy metabolism, but they may have some specific pathways. B cereus has higher efficiency in utilizing monosaccharide, B. anthracis is rich in degradation and transport pathways of amino acids. A glutamate metabolic bypass way exists in B. thuringiensis. Analysis of metabolic pathways provides a new way to study and use food toxin, anthrax toxin, and insecticidal toxin of these strains in future.
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Ceuppens S, Rajkovic A, Heyndrickx M, Tsilia V, Van De Wiele T, Boon N, Uyttendaele M. Regulation of toxin production by Bacillus cereus and its food safety implications. Crit Rev Microbiol 2011; 37:188-213. [PMID: 21417966 DOI: 10.3109/1040841x.2011.558832] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Toxin expression is of utmost importance for the food-borne pathogen B. cereus, both in food poisoning and non-gastrointestinal host infections as well as in interbacterial competition. Therefore it is no surprise that the toxin gene expression is tightly regulated by various internal and environmental signals. An overview of the current knowledge regarding emetic and diarrheal toxin transcription and expression is presented in this review. The food safety aspects and management tools such as temperature control, food preservatives and modified atmosphere packaging are discussed specifically for B. cereus emetic and diarrheal toxin production.
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Affiliation(s)
- Siele Ceuppens
- Ghent University, Faculty of Bioscience Engineering, Laboratory of Food Microbiology and Food Preservation, Ghent, Belgium
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Lactate dehydrogenase A promotes communication between carbohydrate catabolism and virulence in Bacillus cereus. J Bacteriol 2011; 193:1757-66. [PMID: 21296961 DOI: 10.1128/jb.00024-11] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The diarrheal potential of a Bacillus cereus strain is essentially dictated by the amount of secreted nonhemolytic enterotoxin (Nhe). Expression of genes encoding Nhe is regulated by several factors, including the metabolic state of the cells. To identify metabolic sensors that could promote communication between central metabolism and nhe expression, we compared four strains of the B. cereus group in terms of metabolic and nhe expression capacities. We performed growth performance measurements, metabolite analysis, and mRNA measurements of strains F4430/73, F4810/72, F837/76, and PA cultured under anoxic and fully oxic conditions. The results showed that expression levels of nhe and ldhA, which encodes lactate dehydrogenase A (LdhA), were correlated in both aerobically and anaerobically grown cells. We examined the role of LdhA in the F4430/73 strain by constructing an ldhA mutant. The ldhA mutation was more deleterious to anaerobically grown cells than to aerobically grown cells, causing growth limitation and strong deregulation of key fermentative genes. More importantly, the ldhA mutation downregulated enterotoxin gene expression under both anaerobiosis and aerobiosis, with a more pronounced effect under anaerobiosis. Therefore, LdhA was found to exert a major control on both fermentative growth and enterotoxin expression, and it is concluded that there is a direct link between fermentative metabolism and virulence in B. cereus. The data presented also provide evidence that LdhA-dependent regulation of enterotoxin gene expression is oxygen independent. This study is the first report to describe a role of a fermentative enzyme in virulence in B. cereus.
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Carlin F, Brillard J, Broussolle V, Clavel T, Duport C, Jobin M, Guinebretière MH, Auger S, Sorokine A, Nguyen-Thé C. Adaptation of Bacillus cereus, an ubiquitous worldwide-distributed foodborne pathogen, to a changing environment. Food Res Int 2010. [DOI: 10.1016/j.foodres.2009.10.024] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Production, secretion and biological activity of Bacillus cereus enterotoxins. Toxins (Basel) 2010; 2:1690-703. [PMID: 22069656 PMCID: PMC3153264 DOI: 10.3390/toxins2071690] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Revised: 06/14/2010] [Accepted: 06/28/2010] [Indexed: 11/17/2022] Open
Abstract
Bacillus cereus behaves as an opportunistic pathogen frequently causing gastrointestinal diseases, and it is increasingly recognized to be responsible for severe local or systemic infections. Pathogenicity of B. cereus mainly relies on the secretion of a wide array of toxins and enzymes and also on the ability to undergo swarming differentiation in response to surface-sensing. In this report, the pathogenicity exerted by B. cereus toxins is described with particular attention to the regulatory mechanisms of production and secretion of HBL, Nhe and CytK enterotoxins.
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Michelon D, Abraham S, Ebel B, De Coninck J, Husson F, Feron G, Gervais P, Cachon R. Contribution of exofacial thiol groups in the reducing activity of Lactococcus lactis. FEBS J 2010; 277:2282-90. [PMID: 20423456 DOI: 10.1111/j.1742-4658.2010.07644.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Lactococcus lactis can decrease the redox potential at pH 7 (E(h7)) from 200 to -200 mV in oxygen free Man-Rogosa-Sharpe media. Neither the consumption of oxidizing compounds or the release of reducing compounds during lactic acid fermentation were involved in the decrease in E(h7) by the bacteria. Thiol groups located on the bacterial cell surface appear to be the main components that are able to establish a greater exchange current between the Pt electrode and the bacteria. After the final E(h7) (-200 mV) was reached, only thiol-reactive reagents could restore the initial E(h7) value. Inhibition of the proton motive force showed no effect on maintaining the final E(h7) value. These results suggest that maintaining the exofacial thiol (-SH) groups in a reduced state does not depend on an active mechanism. Thiol groups appear to be displayed by membrane proteins or cell wall-bound proteins and may participate in protecting cells against oxidative stress.
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Affiliation(s)
- D Michelon
- Laboratoire de Génie des Procédés Microbiologiques et Alimentaires, AgroSup Dijon, Université de Bourgogne, Dijon, France
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Samapundo S, Everaert H, Wandutu JN, Rajkovic A, Uyttendaele M, Devlieghere F. The influence of headspace and dissolved oxygen level on growth and haemolytic BL enterotoxin production of a psychrotolerant Bacillus weihenstephanensis isolate on potato based ready-to-eat food products. Food Microbiol 2010; 28:298-304. [PMID: 21315987 DOI: 10.1016/j.fm.2010.04.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Revised: 04/12/2010] [Accepted: 04/21/2010] [Indexed: 11/29/2022]
Abstract
The major objective of this study was to determine the influence of the initial headspace and dissolved O(2) level and vacuum packaging on growth and diarrhoeal enterotoxin production by Bacillus weihenstephanensis on potato based ready-to-eat food products. In general, the lower the initial headspace or dissolved O(2) level the slower the maximum growth rate (μ(max), log(10) CFU g(-1) d(-1)), the longer the lag phase duration (λ, d) and the smaller the maximum population density (N(max), log(10) CFU g(-1)) became. The slowest μ(max), the longest λ and the smallest N(max) were generally found for growth under vacuum packaging. This implies shorter shelf-lives will occur at higher initial headspace or dissolved O(2) levels as the growth of B. weihenstephanensis to the infective dose of 10(5) CFU g(-1) in such atmospheres takes a shorter time. Significant consumption of dissolved O(2) only occurred when growth shifted from the lag to the exponential phase and growth generally transitioned from the exponential to the stationary phase when the dissolved O(2) levels fell below ca. 75 ppb. Diarrhoeal enterotoxin production (determined via detection of the L2 component of haemolytic BL) was similar for growth under initial headspace O(2) levels of 1-20.9%, and was only reduced when growth took place under vacuum packaging. The reduction in L2 production when growth took place under vacuum was most probably related to the low final cell densities observed under this condition. Both growth and L2 production were inhibited over a 32-day incubation period at 7 °C by 40% CO(2) irrespective of the headspace or dissolved O(2) levels. The results illustrate the importance of residual O(2) and CO(2) on the shelf-stability and safety of modified atmosphere packaged potato based ready-to-eat food products with regards to B. weihenstephanensis.
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Affiliation(s)
- S Samapundo
- Laboratory of Food Microbiology and Food Preservation, Department of Food Safety and Food Quality, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Gent, Belgium.
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Clair G, Roussi S, Armengaud J, Duport C. Expanding the known repertoire of virulence factors produced by Bacillus cereus through early secretome profiling in three redox conditions. Mol Cell Proteomics 2010; 9:1486-98. [PMID: 20368289 DOI: 10.1074/mcp.m000027-mcp201] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The pathogen Bacillus cereus causes diarrheal disease in humans. In the small intestine, B. cereus has to deal with anaerobiosis, low oxidoreduction potential, and carbohydrate limitation conditions. To gain insight into the virulence potential of low density B. cereus cells in such an environment, we cultured bacteria in low and high oxidoreduction potential anoxic conditions and in fully oxic conditions and compared their full secretomes. A unique pattern of proteins assigned to virulence factors was revealed. Among the 57 virulence-related factors, 31 were found for the first time in the B. cereus secretome. The putative fourth component of hemolysin BL (HblB'), enterotoxin FM, hemolysin II, and three new putative conserved enterotoxins were uncovered. Cross-comparison of the relative abundance of secreted proteins reveals that a restricted set comprising 19 proteins showed significant changes in response to redox condition changes. We complemented these results with transcriptomics data and confirmed the cytotoxicity of the B. cereus secretome toward Caco-2 human epithelial cells. Our data suggest that (i) the redox-dependent regulatory pathway may modulate the expression of a subset of virulence factors to ensure an appropriate response in a specific redox environment, and (ii) an early growth phase-dependent pathway could regulate the expression of several virulence factors, allowing B. cereus to infect a host whatever the redox conditions. This early growth phase-dependent pathway may function, at least partially, independently of the pleiotropic virulence gene regulator PlcR and may therefore be more specific to the B. cereus group.
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Affiliation(s)
- Gérémy Clair
- UMR408, Université d'Avignon et des Pays de Vaucluse, F-84000 Avignon, France
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Kurosu M, Begari E. Vitamin K2 in electron transport system: are enzymes involved in vitamin K2 biosynthesis promising drug targets? Molecules 2010; 15:1531-53. [PMID: 20335999 PMCID: PMC6257245 DOI: 10.3390/molecules15031531] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Revised: 02/11/2010] [Accepted: 03/03/2010] [Indexed: 01/01/2023] Open
Abstract
Aerobic and anaerobic respiratory systems allow cells to transport the electrons to terminal electron acceptors. The quinone (ubiquinone or menaquinone) pool is central to the electron transport chain. In the majority of gram-positive bacteria, vitamin K2 (menaquinone) is the sole quinone in the electron transport chain, and thus, the bacterial enzymes catalyzing the synthesis of menaquinone are potential targets for the development of novel antibacterial drugs. This manuscript reviews the role of vitamin K in bacteria and humans, and especially emphasizes on recent aspects of menaquinones in bacterial electron transport chain and on discoveries of inhibitor molecules targeting bacterial electron transport systems for new antibacterial agents.
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Affiliation(s)
- Michio Kurosu
- Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, 1682 Campus Delivery, Fort Collins, CO 80523-1682, USA.
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Septer AN, Bose JL, Dunn AK, Stabb EV. FNR-mediated regulation of bioluminescence and anaerobic respiration in the light-organ symbiont Vibrio fischeri. FEMS Microbiol Lett 2010; 306:72-81. [PMID: 20298504 DOI: 10.1111/j.1574-6968.2010.01938.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Vibrio fischeri induces both anaerobic respiration and bioluminescence during symbiotic infection. In many bacteria, the oxygen-sensitive regulator FNR activates anaerobic respiration, and a preliminary study using the light-generating lux genes from V. fischeri MJ1 cloned in Escherichia coli suggested that FNR stimulates bioluminescence. To test for FNR-mediated regulation of bioluminescence and anaerobic respiration in V. fischeri, we generated fnr mutants of V. fischeri strains MJ1 and ES114. In both strains, FNR was required for normal fumarate- and nitrate-dependent respiration. However, contrary to the report in transgenic E. coli, FNR mediated the repression of lux. ArcA represses bioluminescence, and P(arcA)-lacZ reporters showed reduced expression in fnr mutants, suggesting a possible indirect effect of FNR on bioluminescence via arcA. Finally, the fnr mutant of ES114 was not impaired in colonization of its host squid, Euprymna scolopes. This study extends the characterization of FNR to the Vibrionaceae and underscores the importance of studying lux regulation in its native background.
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Affiliation(s)
- Alecia N Septer
- Department of Microbiology, University of Georgia, Athens, GA 30602, USA
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Messaoudi K, Clavel T, Schmitt P, Duport C. Fnr mediates carbohydrate-dependent regulation of catabolic and enterotoxin genes in Bacillus cereus F4430/73. Res Microbiol 2010; 161:30-9. [DOI: 10.1016/j.resmic.2009.11.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Revised: 11/09/2009] [Accepted: 11/10/2009] [Indexed: 11/26/2022]
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ResDE-dependent regulation of enterotoxin gene expression in Bacillus cereus: evidence for multiple modes of binding for ResD and interaction with Fnr. J Bacteriol 2009; 191:4419-26. [PMID: 19395489 DOI: 10.1128/jb.00321-09] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In the food-borne pathogen Bacillus cereus F4430/73, the production of major virulence factors hemolysin BL (Hbl) and nonhemolytic enterotoxin (Nhe) is regulated through complex mechanisms. The two-component regulatory system ResDE is involved in the activation of hbl and nhe transcription. Here, the response regulator ResD and the sensor kinase ResE were overexpressed and purified, and autophosphorylation of ResE and transphosphorylation of ResD by ResE were demonstrated in vitro. ResD is mainly monomeric in solution, regardless of its phosphorylation state. ResD was shown to interact directly with promoter regions (p) of the enterotoxin regulator genes resDE, fnr, and plcR and the enterotoxin structural genes nhe and hbl, but with different affinities. Binding of ResD to pplcR, pnhe, and phbl was not dependent on the ResD phosphorylation status. In contrast, ResD phosphorylation significantly increased interactions between ResD and presDE and pfnr. Taken together, these results showed that phosphorylation of ResD results in a different target expression pattern. Furthermore, ResD and the redox activator Fnr were found to physically interact and simultaneously bind their target DNAs. We propose that unphosphorylated ResD acts as an antiactivator of Fnr, while phosphorylated ResD acts as a coactivator of Fnr. Finally, our findings represent the first molecular evidence of the role of ResDE as a sentinel system capable of sensing redox changes and coordinating a response that modulates B. cereus virulence.
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van der Voort M, Abee T. Transcriptional regulation of metabolic pathways, alternative respiration and enterotoxin genes in anaerobic growth of Bacillus cereus ATCC 14579. J Appl Microbiol 2009; 107:795-804. [PMID: 19302486 DOI: 10.1111/j.1365-2672.2009.04252.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
AIMS To assess genes specifically activated during anaerobic growth that are involved in metabolism and pathogenesis of the foodborne pathogen Bacillus cereus. METHODS AND RESULTS Growth under anaerobic conditions in Brain Heart Infusion (BHI) broth revealed a reduced growth rate and lower yield as compared to growth under aerobic conditions. Subsequently, comparative transcriptome analysis showed specific genes induced under anaerobic conditions. These included novel genes identified for anaerobic growth of B. cereus, encoding metabolic pathways, such as the arginine deiminase pathway (ArcABDC), formate dehydrogenase (FdhF) and pyruvate formate lyase (Pfl), and alternative respiratory proteins, such as arsenate reductases. Notably, haemolytic enzyme encoding genes were induced during anaerobic growth, and enterotoxin genes were induced in high cell density transition and stationary phases of aerobic cultures. CONCLUSIONS These data point to induction of stress adaptation and pathogenicity factors and rearrangements of expression of metabolic pathways in response to oxygen limitations in B. cereus. SIGNIFICANCE AND IMPACT OF THE STUDY The reported changes in gene expression show that the foodborne pathogen B. cereus can adjust to anaerobic conditions, such as encountered in the human GI-tract.
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Affiliation(s)
- M van der Voort
- TI Food and Nutrition, Wageningen, The Netherlands and Laboratory of Food Microbiology, Wageningen University, Wageningen, the Netherlands
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Brillard J, Susanna K, Michaud C, Dargaignaratz C, Gohar M, Nielsen-Leroux C, Ramarao N, Kolstø AB, Nguyen-the C, Lereclus D, Broussolle V. The YvfTU two-component system is involved in plcR expression in Bacillus cereus. BMC Microbiol 2008; 8:183. [PMID: 18925929 PMCID: PMC2588459 DOI: 10.1186/1471-2180-8-183] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2008] [Accepted: 10/16/2008] [Indexed: 11/30/2022] Open
Abstract
Background Most extracellular virulence factors produced by Bacillus cereus are regulated by the pleiotropic transcriptional activator PlcR. Among strains belonging to the B. cereus group, the plcR gene is always located in the vicinity of genes encoding the YvfTU two-component system. The putative role of YvfTU in the expression of the PlcR regulon was therefore investigated. Results Expression of the plcR gene was monitored using a transcriptional fusion with a lacZ reporter gene in a yvfTU mutant and in its B. cereus ATCC 14579 parental strain. Two hours after the onset of the stationary phase, a stage at which the PlcR regulon is highly expressed, the plcR expression in the yvfTU mutant was only 50% of that of its parental strain. In addition to the reduced plcR expression in the yvfTU mutant, a few members of the PlcR regulon showed a differential expression, as revealed by transcriptomic and proteomic analyses. The virulence of the yvfTU mutant in a Galleria mellonella insect model was slightly lower than that of the parental strain. Conclusion The YvfTU two-component system is not required for the expression of most of the virulence factors belonging to the PlcR regulon. However, YvfTU is involved in expression of plcR, a major regulator of virulence in B. cereus.
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Affiliation(s)
- Julien Brillard
- UMR408, Sécurité et Qualité des Produits d'Origine Végétale, INRA, Université d'Avignon, F-84000 Avignon, France.
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de Been M, Bart MJ, Abee T, Siezen RJ, Francke C. The identification of response regulator-specific binding sites reveals new roles of two-component systems in Bacillus cereus and closely related low-GC Gram-positives. Environ Microbiol 2008; 10:2796-809. [PMID: 18662309 DOI: 10.1111/j.1462-2920.2008.01700.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
In bacteria, environmental challenges are often translated into a transcriptional response via the cognate response regulators (RRs) of specialized two-component systems (TCSs). A phylogenetic footprinting/shadowing approach was designed and used to identify many novel RR-specific operators for species of the Bacillus cereus group and related Gram-positives. Analysis of the operator sequences revealed characteristic traits for each RR subfamily. For instance, operators related to the largest subfamily (OmpR) typically consisted of direct repeats (e.g. TTAAGA-N5-TTAAGA), whereas operators related to the second largest family (NarL) consisted of inverted repeats (e.g. ATGACA-N2-TGTCAT). This difference indicates a fundamentally different organization of the bound RR dimers between the two subfamilies. Moreover, the identification of the specific operator motifs allowed relating several RRs to a minimal regulon and thereby to a characteristic transcriptional response. Mostly, these regulons comprised genes encoding transport systems, suggesting a direct coupling of stimulus perception to the transport of target compounds. New biological roles could be attributed to various TCSs, including roles in cytochrome c biogenesis (HssRS), transport of carbohydrates, peptides and/or amino acids (YkoGH, LytSR), and resistance to toxic ions (LiaSR), antimicrobial peptides (BceRS) and beta-lactam antibiotics (BacRS, YcbLM). As more and more bacterial genome sequences are becoming available, the use of comparative analyses such as the approach applied in this study will further increase our knowledge of bacterial signal transduction mechanisms and provide directions for the assessment of their role in bacterial performance and survival strategies.
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Affiliation(s)
- Mark de Been
- TI Food and Nutrition (TIFN), Wageningen, the Netherlands.
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Stenfors Arnesen LP, Fagerlund A, Granum PE. From soil to gut:Bacillus cereusand its food poisoning toxins. FEMS Microbiol Rev 2008; 32:579-606. [DOI: 10.1111/j.1574-6976.2008.00112.x] [Citation(s) in RCA: 676] [Impact Index Per Article: 42.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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ApoFnr binds as a monomer to promoters regulating the expression of enterotoxin genes of Bacillus cereus. J Bacteriol 2008; 190:4242-51. [PMID: 18424517 DOI: 10.1128/jb.00336-08] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Bacillus cereus Fnr is a member of the Crp/Fnr (cyclic AMP-binding protein/fumarate nitrate reduction regulatory protein) family of helix-turn-helix transcriptional regulators. It is essential for the expression of hbl and nhe enterotoxin genes independently of the oxygen tension in the environment. We studied aerobic Fnr binding to target sites in promoters regulating the expression of enterotoxin genes. B. cereus Fnr was overexpressed and purified as either a C-terminal His-tagged (Fnr(His)) fusion protein or an N-terminal fusion protein tagged with the Strep-tag (IBA BioTAGnology) ((Strep)Fnr). Both recombinant Fnr proteins were produced as apoforms (clusterless) and occurred as mixtures of monomers and oligomers in solution. However, apoFnr(His) was mainly monomeric, while apo(Strep)Fnr was mainly oligomeric, suggesting that the His-tagged C-terminal extremity may interfere with oligomerization. The oligomeric state of apo(Strep)Fnr was dithiothreitol sensitive, underlining the importance of a disulfide bridge for apoFnr oligomerization. Electrophoretic mobility shift assays showed that monomeric apoFnr, but not oligomeric apoFnr, bound to specific sequences located in the promoter regions of the enterotoxin regulators fnr, resDE, and plcR and the structural genes hbl and nhe. The question of whether apoFnr binding is regulated in vivo by redox-dependent oligomerization is discussed.
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