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Angelini LL, Dos Santos RAC, Fox G, Paruthiyil S, Gozzi K, Shemesh M, Chai Y. Pulcherrimin protects Bacillus subtilis against oxidative stress during biofilm development. NPJ Biofilms Microbiomes 2023; 9:50. [PMID: 37468524 PMCID: PMC10356805 DOI: 10.1038/s41522-023-00418-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2023] [Accepted: 07/04/2023] [Indexed: 07/21/2023] Open
Abstract
Pulcherrimin is an iron-binding reddish pigment produced by various bacterial and yeast species. In the soil bacterium Bacillus subtilis, this pigment is synthesized intracellularly as the colorless pulcherriminic acid by using two molecules of tRNA-charged leucine as the substrate; pulcherriminic acid molecules are then secreted and bind to ferric iron extracellularly to form the red-colored pigment pulcherrimin. The biological importance of pulcherrimin is not well understood. A previous study showed that secretion of pulcherrimin caused iron depletion in the surroundings and growth arrest on cells located at the edge of a B. subtilis colony biofilm. In this study, we identified that pulcherrimin is primarily produced under biofilm conditions and provides protection to cells in the biofilm against oxidative stress. We presented molecular evidence on how pulcherrimin lowers the level of reactive oxygen species (ROS) and alleviates oxidative stress and DNA damage caused by ROS accumulation in a mature biofilm. We also performed global transcriptome profiling to identify differentially expressed genes in the pulcherrimin-deficient mutant compared with the wild type, and further characterized the regulation of genes by pulcherrimin that are related to iron homeostasis, DNA damage response (DDR), and oxidative stress response. Based on our findings, we propose pulcherrimin as an important antioxidant that modulates B. subtilis biofilm development.
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Affiliation(s)
| | | | - Gabriel Fox
- Department of Biology, Northeastern University, Boston, MA, 02115, USA
| | - Srinand Paruthiyil
- Department of Biology, Northeastern University, Boston, MA, 02115, USA
- Medical Scientist Training Program (MSTP), Washington University School of Medicine, 660 S Euclid Ave, St. Louis, MO, 63110, USA
| | - Kevin Gozzi
- Department of Biology, Northeastern University, Boston, MA, 02115, USA
- The Rowland Institute at Harvard, 100 Edwin H. Land Blvd., Cambridge, MA, 02142, USA
| | - Moshe Shemesh
- Department of Food Science, Agricultural Research Organization The Volcani Institute, Derech Hamacabim, POB 15159, Rishon LeZion, 7528809, Israel
| | - Yunrong Chai
- Department of Biology, Northeastern University, Boston, MA, 02115, USA.
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2
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Yeak KYC, Tempelaars M, Wu JL, Westerveld W, Reder A, Michalik S, Dhople VM, Völker U, Pané-Farré J, Wells-Bennik MHJ, Abee T. SigB modulates expression of novel SigB regulon members via Bc1009 in non-stressed and heat-stressed cells revealing its alternative roles in Bacillus cereus. BMC Microbiol 2023; 23:37. [PMID: 36759782 PMCID: PMC9912610 DOI: 10.1186/s12866-023-02783-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Accepted: 01/24/2023] [Indexed: 02/11/2023] Open
Abstract
BACKGROUND The Bacillus cereus Sigma B (SigB) dependent general stress response is activated via the two-component RsbKY system, which involves a phosphate transfer from RsbK to RsbY. It has been hypothesized that the Hpr-like phosphocarrier protein (Bc1009) encoded by bc1009 in the SigB gene cluster may play a role in this transfer, thereby acting as a regulator of SigB activation. Alternatively, Bc1009 may be involved in the activation of a subset of SigB regulon members. RESULTS We first investigated the potential role of bc1009 to act as a SigB regulator but ruled out this possibility as the deletion of bc1009 did not affect the expression of sigB and other SigB gene cluster members. The SigB-dependent functions of Bc1009 were further examined in B. cereus ATCC14579 via comparative proteome profiling (backed up by transcriptomics) of wt, Δbc1009 and ΔsigB deletion mutants under heat stress at 42 °C. This revealed 284 proteins displaying SigB-dependent alterations in protein expression levels in heat-stressed cells, including a subgroup of 138 proteins for which alterations were also Bc1009-dependent. Next to proteins with roles in stress defense, newly identified SigB and Bc1009-dependent proteins have roles in cell motility, signal transduction, transcription, cell wall biogenesis, and amino acid transport and metabolism. Analysis of lethal stress survival at 50 °C after pre-adaptation at 42 °C showed intermediate survival efficacy of Δbc1009 cells, highest survival of wt, and lowest survival of ΔsigB cells, respectively. Additional comparative proteome analysis of non-stressed wt and mutant cells at 30 °C revealed 96 proteins with SigB and Bc1009-dependent differences in levels: 51 were also identified under heat stress, and 45 showed significant differential expression at 30 °C. This includes proteins with roles in carbohydrate/ion transport and metabolism. Overlapping functions at 30 °C and 42 °C included proteins involved in motility, and ΔsigB and Δbc1009 cells showed reduced motility compared to wt cells in swimming assays at both temperatures. CONCLUSION Our results extend the B. cereus SigB regulon to > 300 members, with a novel role of SigB-dependent Bc1009 in the activation of a subregulon of > 180 members, conceivably via interactions with other transcriptional regulatory networks.
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Affiliation(s)
- Kah Yen Claire Yeak
- grid.419921.60000 0004 0588 7915NIZO, Kernhemseweg 2, PO Box 20, 6718 ZB Ede, The Netherlands ,grid.4818.50000 0001 0791 5666Food Microbiology, Wageningen University and Research, PO Box 8129, 6700 EV Wageningen, The Netherlands
| | - Marcel Tempelaars
- grid.4818.50000 0001 0791 5666Food Microbiology, Wageningen University and Research, PO Box 8129, 6700 EV Wageningen, The Netherlands
| | - Jia Lun Wu
- grid.4818.50000 0001 0791 5666Food Microbiology, Wageningen University and Research, PO Box 8129, 6700 EV Wageningen, The Netherlands
| | - Wouter Westerveld
- grid.4818.50000 0001 0791 5666Food Microbiology, Wageningen University and Research, PO Box 8129, 6700 EV Wageningen, The Netherlands
| | - Alexander Reder
- grid.5603.0Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Stephan Michalik
- grid.5603.0Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Vishnu M. Dhople
- grid.5603.0Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Uwe Völker
- grid.5603.0Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Jan Pané-Farré
- grid.10253.350000 0004 1936 9756Center for Synthetic Microbiology (SYNMIKRO) & Department of Chemistry, Philipps-University Marburg, Karl-Von-Frisch-Strasse 14, 35043 Marburg, Germany
| | | | - Tjakko Abee
- Food Microbiology, Wageningen University and Research, PO Box 8129, 6700 EV, Wageningen, The Netherlands.
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3
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Yeak KYC, Boekhorst J, Wels M, Abee T, Wells-Bennik MHJ. Prediction and validation of novel SigB regulon members in Bacillus subtilis and regulon structure comparison to Bacillales members. BMC Microbiol 2023; 23:17. [PMID: 36653740 PMCID: PMC9847131 DOI: 10.1186/s12866-022-02700-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2022] [Accepted: 11/11/2022] [Indexed: 01/19/2023] Open
Abstract
BACKGROUND Sigma factor B (SigB) is the central regulator of the general stress response in Bacillus subtilis and regulates a group of genes in response to various stressors, known as the SigB regulon members. Genes that are directly regulated by SigB contain a promotor binding motif (PBM) with a previously identified consensus sequence. RESULTS In this study, refined SigB PBMs were derived and different spacer compositions and lengths (N12-N17) were taken into account. These were used to identify putative SigB-regulated genes in the B. subtilis genome, revealing 255 genes: 99 had been described in the literature and 156 genes were newly identified, increasing the number of SigB putative regulon members (with and without a SigB PBM) to > 500 in B. subtilis. The 255 genes were assigned to five categories (I-V) based on their similarity to the original SigB consensus sequences. The functionalities of selected representatives per category were assessed using promoter-reporter fusions in wt and ΔsigB mutants upon exposure to heat, ethanol, and salt stress. The activity of the PrsbV (I) positive control was induced upon exposure to all three stressors. PytoQ (II) showed SigB-dependent activity only upon exposure to ethanol, whereas PpucI (II) with a N17 spacer and PylaL (III) with a N16 spacer showed mild induction regardless of heat/ethanol/salt stress. PywzA (III) and PyaaI (IV) displayed ethanol-specific SigB-dependent activities despite a lower-level conserved - 10 binding motif. PgtaB (V) was SigB-induced under ethanol and salt stress while lacking a conserved - 10 binding region. The activities of PygaO and PykaA (III) did not show evident changes under the conditions tested despite having a SigB PBM that highly resembled the consensus. The identified extended SigB regulon candidates in B. subtilis are mainly involved in coping with stress but are also engaged in other cellular processes. Orthologs of SigB regulon candidates with SigB PBMs were identified in other Bacillales genomes, but not all showed a SigB PBM. Additionally, genes involved in the integration of stress signals to activate SigB were predicted in these genomes, indicating that SigB signaling and regulon genes are species-specific. CONCLUSION The entire SigB regulatory network is sophisticated and not yet fully understood even for the well-characterized organism B. subtilis 168. Knowledge and information gained in this study can be used in further SigB studies to uncover a complete picture of the role of SigB in B. subtilis and other species.
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Affiliation(s)
- Kah Yen Claire Yeak
- grid.419921.60000 0004 0588 7915NIZO, Ede, The Netherlands ,grid.4818.50000 0001 0791 5666Food Microbiology, Wageningen University and Research, Wageningen, The Netherlands
| | - Jos Boekhorst
- grid.419921.60000 0004 0588 7915NIZO, Ede, The Netherlands ,grid.4818.50000 0001 0791 5666Host Microbe Interactomics Group, Wageningen University and Research, Wageningen, The Netherlands
| | - Michiel Wels
- grid.419921.60000 0004 0588 7915NIZO, Ede, The Netherlands ,grid.426040.4Rijk Zwaan Breeding B.V, Fijnaart, The Netherlands
| | - Tjakko Abee
- grid.4818.50000 0001 0791 5666Food Microbiology, Wageningen University and Research, Wageningen, The Netherlands
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Lamba S, Mundanda Muthappa D, Fanning S, Scannell AGM. Sporulation and Biofilms as Survival Mechanisms of Bacillus Species in Low-Moisture Food Production Environments. Foodborne Pathog Dis 2022; 19:448-462. [PMID: 35819266 DOI: 10.1089/fpd.2022.0006] [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: 11/13/2022] Open
Abstract
Low-moisture foods (LMF) have clear advantages with respect to limiting the growth of foodborne pathogens. However, the incidences of Bacillus species in LMF reported in recent years raise concerns about food quality and safety, particularly when these foods are used as ingredients in more complex higher moisture products. This literature review describes the interlinked pathways of sporulation and biofilm formation by Bacillus species and their underlying molecular mechanisms that contribute to the bacteriums' persistence in LMF production environments. The long-standing challenges of food safety and quality in the LMF industry are also discussed with a focus on the bakery industry.
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Affiliation(s)
- Sakshi Lamba
- UCD Institute of Food and Health, Physiotherapy and Sports Science, University College Dublin, Dublin, Ireland.,UCD Centre for Food Safety, Physiotherapy and Sports Science, University College Dublin, Dublin, Ireland.,UCD School of Agriculture and Food Science, and Physiotherapy and Sports Science, University College Dublin, Dublin, Ireland
| | - Dechamma Mundanda Muthappa
- UCD Centre for Food Safety, Physiotherapy and Sports Science, University College Dublin, Dublin, Ireland.,UCD School of Agriculture and Food Science, and Physiotherapy and Sports Science, University College Dublin, Dublin, Ireland
| | - Séamus Fanning
- UCD Institute of Food and Health, Physiotherapy and Sports Science, University College Dublin, Dublin, Ireland.,UCD Centre for Food Safety, Physiotherapy and Sports Science, University College Dublin, Dublin, Ireland.,UCD School of Public Health, Physiotherapy and Sports Science, University College Dublin, Dublin, Ireland
| | - Amalia G M Scannell
- UCD Institute of Food and Health, Physiotherapy and Sports Science, University College Dublin, Dublin, Ireland.,UCD Centre for Food Safety, Physiotherapy and Sports Science, University College Dublin, Dublin, Ireland.,UCD School of Agriculture and Food Science, and Physiotherapy and Sports Science, University College Dublin, Dublin, Ireland
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5
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The Alternative Sigma Factor SigB Is Required for the Pathogenicity of Bacillus thuringiensis. J Bacteriol 2020; 202:JB.00265-20. [PMID: 32817096 DOI: 10.1128/jb.00265-20] [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: 05/04/2020] [Accepted: 08/11/2020] [Indexed: 11/20/2022] Open
Abstract
To adapt to changing and potentially hostile environments, bacteria can activate the transcription of genes under the control of alternative sigma factors, such as SigB, a master regulator of the general stress response in several Gram-positive species. Bacillus thuringiensis is a Gram-positive spore-forming invertebrate pathogen whose life cycle includes a variety of environments, including plants and the insect hemocoel or gut. Here, we assessed the role of SigB during the infectious cycle of B. thuringiensis in a Galleria mellonella insect model. We used a fluorescent reporter coupled to flow cytometry and showed that SigB was activated in vivo We also showed that the pathogenicity of the ΔsigB mutant was severely affected when inoculated via the oral route, suggesting that SigB is critical for B. thuringiensis adaptation to the gut environment of the insect. We could not detect an effect of the sigB deletion on the survival of the bacteria or on their sporulation efficiency in the cadavers. However, the gene encoding the pleiotropic regulator Spo0A was upregulated in the ΔsigB mutant cells during the infectious process.IMPORTANCE Pathogenic bacteria often need to transition between different ecosystems, and their ability to cope with such variations is critical for their survival. Several Gram-positive species have developed an adaptive response mediated by the general stress response alternative sigma factor SigB. In order to understand the ecophysiological role of this regulator in Bacillus thuringiensis, an entomopathogenic bacterium widely used as a biopesticide, we sought to examine the fate of a ΔsigB mutant during its life cycle in the natural setting of an insect larva. This allowed us, in particular, to show that SigB was activated during infection and that it was required for the pathogenicity of B. thuringiensis via the oral route of infection.
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6
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Rodriguez Ayala F, Bartolini M, Grau R. The Stress-Responsive Alternative Sigma Factor SigB of Bacillus subtilis and Its Relatives: An Old Friend With New Functions. Front Microbiol 2020; 11:1761. [PMID: 33042030 PMCID: PMC7522486 DOI: 10.3389/fmicb.2020.01761] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Accepted: 07/06/2020] [Indexed: 12/13/2022] Open
Abstract
Alternative sigma factors have led the core RNA polymerase (RNAP) to recognize different sets of promoters to those recognized by the housekeeping sigma A-directed RNAP. This change in RNAP promoter selectivity allows a rapid and flexible reformulation of the genetic program to face environmental and metabolic stimuli that could compromise bacterial fitness. The model bacterium Bacillus subtilis constitutes a matchless living system in the study of the role of alternative sigma factors in gene regulation and physiology. SigB from B. subtilis was the first alternative sigma factor described in bacteria. Studies of SigB during the last 40 years have shown that it controls a genetic universe of more than 150 genes playing crucial roles in stress response, adaption, and survival. Activation of SigB relies on three separate pathways that specifically respond to energy, environmental, and low temperature stresses. SigB homologs, present in other Gram-positive bacteria, also play important roles in virulence against mammals. Interestingly, during recent years, other unexpected B. subtilis responses were found to be controlled by SigB. In particular, SigB controls the efficiencies of spore and biofilm formation, two important features that play critical roles in adaptation and survival in planktonic and sessile B. subtilis communities. In B. subtilis, SigB induces the expression of the Spo0E aspartyl-phosphatase, which is responsible for the blockage of sporulation initiation. The upregulated activity of Spo0E connects the two predominant adaptive pathways (i.e., sporulation and stress response) present in B. subtilis. In addition, the RsbP serine-phosphatase, belonging to the energy stress arm of the SigB regulatory cascade, controls the expression of the key transcription factor SinR to decide whether cells residing in the biofilm remain in and maintain biofilm growth or scape to colonize new niches through biofilm dispersal. SigB also intervenes in the recognition of and response to surrounding microorganisms, a new SigB role that could have an agronomic impact. SigB is induced when B. subtilis is confronted with phytopathogenic fungi (e.g., Fusarium verticillioides) and halts fungal growth to the benefit of plant growth. In this article, we update and review literature on the different regulatory networks that control the activation of SigB and the new roles that have been described the recent years.
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Affiliation(s)
- Facundo Rodriguez Ayala
- Departamento de Micro y Nanotecnología, Instituto de Nanociencia y Nanotecnología - Comisión Nacional de Energía Atómica (CNEA), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Marco Bartolini
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.,Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Roberto Grau
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.,Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
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7
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Role of Glutamate Synthase in Biofilm Formation by Bacillus subtilis. J Bacteriol 2020; 202:JB.00120-20. [PMID: 32393519 DOI: 10.1128/jb.00120-20] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Accepted: 05/04/2020] [Indexed: 11/20/2022] Open
Abstract
Bacillus subtilis forms robust biofilms in the presence of large amounts of carbon sources, such as glycerol. However, little is known about the importance of the metabolic systems, or the relationship between metabolic systems and regulatory systems, involved in biofilm formation. Glutamate synthase, encoded by gltAB, is an enzyme that converts 2-ketoglutarate (a tricarboxylic acid [TCA] cycle intermediate) and glutamine into glutamate, which is a general amino group donor in metabolism. Here, we show that a ΔgltA mutant exhibited early arrest of biofilm formation in complex medium containing glycerol. This phenotype was not due to glutamate auxotrophy. Consistent with its biofilm formation phenotype, the ΔgltA mutant exhibited an early decrease in expression of the epsA and tapA operons, which are responsible for production of biofilm matrix polymers. This resulted from decreased activity of their regulator, Spo0A, as evidenced by reduced expression of other Spo0A-regulated genes in the ΔgltA mutant. The ΔgltA mutation prevented biofilm formation only in the presence of large amounts of glycerol. Moreover, limited expression of citrate synthase (but not other TCA enzymes) restored biofilm-forming ability to the ΔgltA mutant. These results indicate that the ΔgltA mutant accumulates an inhibitory intermediate (citrate) in the TCA cycle in the presence of large amounts of glycerol. The ΔgltA mutant formed biofilms when excess iron was added to the medium. Taken together, the data suggest that accumulation of citrate ions by the ΔgltA mutant causes iron shortage due to chelation, which prevents activation of Spo0A and causes defective biofilm formation.IMPORTANCE Bacillus subtilis, a model organism for bacterial biofilm formation, forms robust biofilms in a medium-dependent manner. Although the regulatory network that controls biofilm formation has been well studied, the importance of the underlying metabolic systems remains to be elucidated. The present study demonstrates that a metabolic disorder in a well-conserved metabolic system causes accumulation of an inhibitory metabolic intermediate that prevents activation of the system that regulates biofilm formation. These findings increase our understanding of the coordination between cellular metabolic status and the regulatory networks governing biofilm formation.
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Stochastic pulsing of gene expression enables the generation of spatial patterns in Bacillus subtilis biofilms. Nat Commun 2020; 11:950. [PMID: 32075967 PMCID: PMC7031267 DOI: 10.1038/s41467-020-14431-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 12/17/2019] [Indexed: 12/27/2022] Open
Abstract
Stochastic pulsing of gene expression can generate phenotypic diversity in a genetically identical population of cells, but it is unclear whether it has a role in the development of multicellular systems. Here, we show how stochastic pulsing of gene expression enables spatial patterns to form in a model multicellular system, Bacillus subtilis bacterial biofilms. We use quantitative microscopy and time-lapse imaging to observe pulses in the activity of the general stress response sigma factor σB in individual cells during biofilm development. Both σB and sporulation activity increase in a gradient, peaking at the top of the biofilm, even though σB represses sporulation. As predicted by a simple mathematical model, increasing σB expression shifts the peak of sporulation to the middle of the biofilm. Our results demonstrate how stochastic pulsing of gene expression can play a key role in pattern formation during biofilm development. Stochastic pulsing of gene expression can generate phenotypic diversity in a genetically identical population of cells. Here, the authors show that stochastic pulsing in the expression of a sigma factor enables the formation of spatial patterns in a multicellular system, Bacillus subtilis bacterial biofilms.
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9
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Differentiation of Vegetative Cells into Spores: a Kinetic Model Applied to Bacillus subtilis. Appl Environ Microbiol 2019; 85:AEM.00322-19. [PMID: 30902849 DOI: 10.1128/aem.00322-19] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Accepted: 03/10/2019] [Indexed: 01/28/2023] Open
Abstract
Spore-forming bacteria are natural contaminants of food raw materials, and sporulation can occur in many environments from farm to fork. In order to characterize and to predict spore formation over time, we developed a model that describes both the kinetics of growth and the differentiation of vegetative cells into spores. The model is based on a classical growth model and enables description of the kinetics of sporulation with the addition of three parameters specific to sporulation. Two parameters are related to the probability of each vegetative cell to commit to sporulation and to form a spore, and the last one is related to the time needed to form a spore once the cell is committed to sporulation. The goodness of fit of this growth-sporulation model was assessed using growth-sporulation kinetics at various temperatures in laboratory medium or in whey for Bacillus subtilis, Bacillus cereus, and Bacillus licheniformis The model accurately describes the kinetics in these different conditions, with a mean error lower than 0.78 log10 CFU/ml for the growth and 1.08 log10 CFU/ml for the sporulation. The biological meaning of the parameters was validated with a derivative strain of Bacillus subtilis 168 which produces green fluorescent protein at the initiation of sporulation. This model provides physiological information on the spore formation and on the temporal abilities of vegetative cells to differentiate into spores and reveals the heterogeneity of spore formation during and after growth.IMPORTANCE The growth-sporulation model describes the progressive transition from vegetative cells to spores with sporulation parameters describing the sporulation potential of each vegetative cell. Consequently, the model constitutes an interesting tool to assess the sporulation potential of a bacterial population over time with accurate parameters such as the time needed to obtain one resistant spore and the probability of sporulation. Further, this model can be used to assess these data under various environmental conditions in order to better identify the conditions favorable for sporulation regarding the time to obtain the first spore and/or the concentrations of spores which could be reached during a food process.
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10
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A Mutation in the Bacillus subtilis rsbU Gene That Limits RNA Synthesis during Sporulation. J Bacteriol 2017; 199:JB.00212-17. [PMID: 28461450 DOI: 10.1128/jb.00212-17] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 04/19/2017] [Indexed: 11/20/2022] Open
Abstract
Mutants of Bacillis subtilis that are temperature sensitive for RNA synthesis during sporulation were isolated after selection with a 32P suicide agent. Whole-genome sequencing revealed that two of the mutants carried an identical lesion in the rsbU gene, which encodes a phosphatase that indirectly activates SigB, the stress-responsive RNA polymerase sigma factor. The mutation appeared to cause RsbU to be hyperactive, because the mutants were more resistant than the parent strain to ethanol stress. In support of this hypothesis, pseudorevertants that regained wild-type levels of sporulation at high temperature had secondary mutations that prevented expression of the mutant rsbU gene. The properties of these RsbU mutants support the idea that activation of SigB diminishes the bacterium's ability to sporulate.IMPORTANCE Most bacterial species encode multiple RNA polymerase promoter recognition subunits (sigma factors). Each sigma factor directs RNA polymerase to different sets of genes; each gene set typically encodes proteins important for responses to specific environmental conditions, such as changes in temperature, salt concentration, and nutrient availability. A selection for mutants of Bacillus subtilis that are temperature sensitive for RNA synthesis during sporulation unexpectedly yielded strains with a point mutation in rsbU, a gene that encodes a protein that normally activates sigma factor B (SigB) under conditions of salt stress. The mutation appears to cause RsbU, and therefore SigB, to be active inappropriately, thereby inhibiting, directly or indirectly, the ability of the cells to transcribe sporulation genes.
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11
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Bremer E. Clostridium difficile: A bad bug goes into defensive mode. Environ Microbiol 2017; 19:2523-2528. [PMID: 28447375 DOI: 10.1111/1462-2920.13776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Accepted: 04/19/2017] [Indexed: 11/26/2022]
Affiliation(s)
- Erhard Bremer
- Laboratory for Microbiology, Department of Biology, Philipps-University Marburg, Karl-von Frisch Str. 8, Marburg, D-35043, Germany.,LOEWE Center for Synthetic Microbiology, Philipps-University Marburg, Hans-Meerwein Str. 6, Marburg, D-35043, Germany
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12
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Handtke S, Albrecht D, Zühlke D, Otto A, Becher D, Schweder T, Riedel K, Hecker M, Voigt B. Bacillus pumilus KatX2 confers enhanced hydrogen peroxide resistance to a Bacillus subtilis PkatA::katX2 mutant strain. Microb Cell Fact 2017; 16:72. [PMID: 28446175 PMCID: PMC5406934 DOI: 10.1186/s12934-017-0684-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 04/19/2017] [Indexed: 11/27/2022] Open
Abstract
Background Bacillus pumilus cells exhibit a significantly higher resistance to hydrogen peroxide compared to closely related Bacilli like Bacillus subtilis. Results In this study we analyzed features of the catalase KatX2 of B. pumilus as one of the most important parts of the cellular response to hydrogen peroxide. KatX2, the vegetative catalase expressed in B. pumilus, was compared to the vegetative catalase KatA of B. subtilis. Data of our study demonstrate that B. pumilus can degrade toxic concentrations of hydrogen peroxide faster than B. subtilis. By replacing B. subtiliskatA gene by katX2 we could significantly enhance its resistance to H2O2 and its potential to eliminate this toxic compound. Mutant cells showed a 1.5- to 2-fold higher survival to toxic concentrations of hydrogen peroxide compared to wild type cells. Furthermore, we found reversible but also irreversible oxidations of the KatX2 protein which, in contrast to KatA, contains several cysteine residues. Conclusions Our study indicates that the catalase KatX2 plays a major role in the increased resistance of B. pumilus to oxidative stress caused by hydrogen peroxide. Resistance to hydrogen peroxide of other Bacilli can be enhanced by exchanging the native catalase in the cells with katX2. Electronic supplementary material The online version of this article (doi:10.1186/s12934-017-0684-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Stefan Handtke
- Institute for Microbiology, University of Greifswald, 17489, Greifswald, Germany.,Institute of Marine Biotechnology, 17489, Greifswald, Germany
| | - Dirk Albrecht
- Institute for Microbiology, University of Greifswald, 17489, Greifswald, Germany
| | - Daniela Zühlke
- Institute for Microbiology, University of Greifswald, 17489, Greifswald, Germany
| | - Andreas Otto
- Institute for Microbiology, University of Greifswald, 17489, Greifswald, Germany
| | - Dörte Becher
- Institute for Microbiology, University of Greifswald, 17489, Greifswald, Germany.,Institute of Marine Biotechnology, 17489, Greifswald, Germany
| | - Thomas Schweder
- Institute of Pharmacy, University of Greifswald, 17489, Greifswald, Germany.,Institute of Marine Biotechnology, 17489, Greifswald, Germany
| | - Kathrin Riedel
- Institute for Microbiology, University of Greifswald, 17489, Greifswald, Germany.,Institute of Marine Biotechnology, 17489, Greifswald, Germany
| | - Michael Hecker
- Institute for Microbiology, University of Greifswald, 17489, Greifswald, Germany.,Institute of Marine Biotechnology, 17489, Greifswald, Germany
| | - Birgit Voigt
- Institute for Microbiology, University of Greifswald, 17489, Greifswald, Germany. .,Institute of Marine Biotechnology, 17489, Greifswald, Germany. .,Research Institute for Leather and Plastic Sheeting, Meißner-Ring 1-5, 09599, Freiberg, Germany.
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13
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Kint N, Janoir C, Monot M, Hoys S, Soutourina O, Dupuy B, Martin-Verstraete I. The alternative sigma factor σ B plays a crucial role in adaptive strategies of Clostridium difficile during gut infection. Environ Microbiol 2017; 19:1933-1958. [PMID: 28198085 DOI: 10.1111/1462-2920.13696] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Revised: 01/19/2017] [Accepted: 01/22/2017] [Indexed: 12/29/2022]
Abstract
Clostridium difficile is a major cause of diarrhoea associated with antibiotherapy. Exposed to stresses in the gut, C. difficile can survive by inducing protection, detoxification and repair systems. In several firmicutes, most of these systems are controlled by the general stress response involving σB . In this work, we studied the role of σB in the physiopathology of C. difficile. We showed that the survival of the sigB mutant during the stationary phase was reduced. Using a transcriptome analysis, we showed that σB controls the expression of ∼25% of genes including genes involved in sporulation, metabolism, cell surface biogenesis and the management of stresses. By contrast, σB does not control toxin gene expression. In agreement with the up-regulation of sporulation genes, the sporulation efficiency is higher in the sigB mutant than in the wild-type strain. sigB inactivation also led to increased sensitivity to acidification, cationic antimicrobial peptides, nitric oxide and ROS. In addition, we showed for the first time that σB also plays a crucial role in oxygen tolerance in this strict anaerobe. Finally, we demonstrated that the fitness of colonisation by the sigB mutant is greatly affected in a dixenic mouse model of colonisation when compared to the wild-type strain.
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Affiliation(s)
- Nicolas Kint
- Laboratoire Pathogénese des Bactéries Anaérobies, Institut Pasteur, Paris, France.,Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Claire Janoir
- EA 4043, Unité Bactéries Pathogènes et Santé (UBaPS), Université Paris-Sud, Université Paris-Saclay, 92290, Châtenay-Malabry, France
| | - Marc Monot
- Laboratoire Pathogénese des Bactéries Anaérobies, Institut Pasteur, Paris, France.,Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Sandra Hoys
- EA 4043, Unité Bactéries Pathogènes et Santé (UBaPS), Université Paris-Sud, Université Paris-Saclay, 92290, Châtenay-Malabry, France
| | - Olga Soutourina
- Laboratoire Pathogénese des Bactéries Anaérobies, Institut Pasteur, Paris, France.,Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Bruno Dupuy
- Laboratoire Pathogénese des Bactéries Anaérobies, Institut Pasteur, Paris, France.,Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Isabelle Martin-Verstraete
- Laboratoire Pathogénese des Bactéries Anaérobies, Institut Pasteur, Paris, France.,Université Paris Diderot, Sorbonne Paris Cité, Paris, France
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14
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Stepanek JJ, Schäkermann S, Wenzel M, Prochnow P, Bandow JE. Purine biosynthesis is the bottleneck in trimethoprim-treated Bacillus subtilis. Proteomics Clin Appl 2016; 10:1036-1048. [PMID: 27329548 DOI: 10.1002/prca.201600039] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2016] [Revised: 06/01/2016] [Accepted: 06/15/2016] [Indexed: 11/11/2022]
Abstract
PURPOSE Trimethoprim is a folate biosynthesis inhibitor. Tetrahydrofolates are essential for the transfer of C1 units in several biochemical pathways including purine, thymine, methionine, and glycine biosynthesis. This study addressed the effects of folate biosynthesis inhibition on bacterial physiology. EXPERIMENTAL DESIGN Two complementary proteomic approaches were employed to analyze the response of Bacillus subtilis to trimethoprim. Acute changes in protein synthesis rates were monitored by radioactive pulse labeling of newly synthesized proteins and subsequent 2DE analysis. Changes in protein levels were detected using gel-free quantitative MS. RESULTS Proteins involved in purine and histidine biosynthesis, the σB -dependent general stress response, and sporulation were upregulated. Most prominently, the PurR-regulon required for de novo purine biosynthesis was derepressed indicating purine depletion. The general stress response was activated energy dependently and in a subpopulation of treated cultures an early onset of sporulation was observed, most likely triggered by low guanosine triphosphate levels. Supplementation of adenosine triphosphate, adenosine, and guanosine to the medium substantially decreased antibacterial activity, showing that purine depletion becomes the bottleneck in trimethoprim-treated B. subtilis. CONCLUSIONS AND CLINICAL RELEVANCE The frequently prescribed antibiotic trimethoprim causes purine depletion in B. subtilis, which can be complemented by supplementing purines to the medium.
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Affiliation(s)
| | | | - Michaela Wenzel
- Ruhr-Universität Bochum, Applied Microbiology, Bochum, Germany
| | - Pascal Prochnow
- Ruhr-Universität Bochum, Applied Microbiology, Bochum, Germany
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15
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Resilience in the Face of Uncertainty: Sigma Factor B Fine-Tunes Gene Expression To Support Homeostasis in Gram-Positive Bacteria. Appl Environ Microbiol 2016; 82:4456-4469. [PMID: 27208112 DOI: 10.1128/aem.00714-16] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Gram-positive bacteria are ubiquitous and diverse microorganisms that can survive and sometimes even thrive in continuously changing environments. The key to such resilience is the ability of members of a population to respond and adjust to dynamic conditions in the environment. In bacteria, such responses and adjustments are mediated, at least in part, through appropriate changes in the bacterial transcriptome in response to the conditions encountered. Resilience is important for bacterial survival in diverse, complex, and rapidly changing environments and requires coordinated networks that integrate individual, mechanistic responses to environmental cues to enable overall metabolic homeostasis. In many Gram-positive bacteria, a key transcriptional regulator of the response to changing environmental conditions is the alternative sigma factor σ(B) σ(B) has been characterized in a subset of Gram-positive bacteria, including the genera Bacillus, Listeria, and Staphylococcus Recent insight from next-generation-sequencing results indicates that σ(B)-dependent regulation of gene expression contributes to resilience, i.e., the coordination of complex networks responsive to environmental changes. This review explores contributions of σ(B) to resilience in Bacillus, Listeria, and Staphylococcus and illustrates recently described regulatory functions of σ(B).
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16
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Schultz D. Coordination of cell decisions and promotion of phenotypic diversity in B. subtilis via pulsed behavior of the phosphorelay. Bioessays 2016; 38:440-5. [PMID: 26941227 DOI: 10.1002/bies.201500199] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The phosphorelay of Bacillus subtilis, a kinase cascade that activates master regulator Spo0A ~ P in response to starvation signals, is the core of a large network controlling the cell's decision to differentiate into sporulation and other phenotypes. This article reviews recent advances in understanding the origins and purposes of the complex dynamical behavior of the phosphorelay, which pulses with peaks of activity coordinated with the cell cycle. The transient imbalance in the expression of two critical genes caused by their strategic placement at opposing ends of the chromosome proved to be the key for this pulsed behavior. Feedback control loops in the phosphorelay use these pulses to implement a timer mechanism, which creates several windows of opportunity for phenotypic transitions over multiple generations. This strategy allows the cell to coordinate multiple differentiation programs in a decision process that fosters phenotypic diversity and adapts to current conditions.
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Affiliation(s)
- Daniel Schultz
- Department of Systems Biology, Harvard Medical School, Boston, MA, USA
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17
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Widderich N, Rodrigues CDA, Commichau FM, Fischer KE, Ramirez-Guadiana FH, Rudner DZ, Bremer E. Salt-sensitivity of σ(H) and Spo0A prevents sporulation of Bacillus subtilis at high osmolarity avoiding death during cellular differentiation. Mol Microbiol 2016; 100:108-24. [PMID: 26712348 DOI: 10.1111/mmi.13304] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/04/2015] [Indexed: 01/15/2023]
Abstract
The spore-forming bacterium Bacillus subtilis frequently experiences high osmolarity as a result of desiccation in the soil. The formation of a highly desiccation-resistant endospore might serve as a logical osmostress escape route when vegetative growth is no longer possible. However, sporulation efficiency drastically decreases concomitant with an increase in the external salinity. Fluorescence microscopy of sporulation-specific promoter fusions to gfp revealed that high salinity blocks entry into the sporulation pathway at a very early stage. Specifically, we show that both Spo0A- and SigH-dependent transcription are impaired. Furthermore, we demonstrate that the association of SigH with core RNA polymerase is reduced under these conditions. Suppressors that modestly increase sporulation efficiency at high salinity map to the coding region of sigH and in the regulatory region of kinA, encoding one the sensor kinases that activates Spo0A. These findings led us to discover that B. subtilis cells that overproduce KinA can bypass the salt-imposed block in sporulation. Importantly, these cells are impaired in the morphological process of engulfment and late forespore gene expression and frequently undergo lysis. Altogether our data indicate that B. subtilis blocks entry into sporulation in high-salinity environments preventing commitment to a developmental program that it cannot complete.
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Affiliation(s)
- Nils Widderich
- Department of Biology, Laboratory for Molecular Microbiology, Philipps-University Marburg, Karl-von-Frisch Str. 8, D-35043, Marburg, Germany
| | - Christopher D A Rodrigues
- Department of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA, 02115-5701, USA
| | - Fabian M Commichau
- Department of General Microbiology, Institute of Microbiology and Genetics, Georg August University Göttingen, Griesebachstr, 8, D-37077, Göttingen, Germany
| | - Kathleen E Fischer
- Department of Biology, Laboratory for Molecular Microbiology, Philipps-University Marburg, Karl-von-Frisch Str. 8, D-35043, Marburg, Germany
| | - Fernando H Ramirez-Guadiana
- Department of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA, 02115-5701, USA
| | - David Z Rudner
- Department of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA, 02115-5701, USA
| | - Erhard Bremer
- Department of Biology, Laboratory for Molecular Microbiology, Philipps-University Marburg, Karl-von-Frisch Str. 8, D-35043, Marburg, Germany
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18
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van der Steen JB, Hellingwerf KJ. Activation of the General Stress Response of Bacillus subtilis by Visible Light. Photochem Photobiol 2015; 91:1032-45. [PMID: 26189730 DOI: 10.1111/php.12499] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2015] [Accepted: 06/25/2015] [Indexed: 12/20/2022]
Abstract
A key challenge for microbiology is to understand how evolution has shaped the wiring of regulatory networks. This is amplified by the paucity of information of power-spectra of physicochemical stimuli to which microorganisms are exposed. Future studies of genome evolution, driven by altered stimulus regimes, will therefore require a versatile signal transduction system that allows accurate signal dosing. Here, we review the general stress response of Bacillus subtilis, and its upstream signal transduction network, as a candidate system. It can be activated by red and blue light, and by many additional stimuli. Signal integration therefore is an intricate function of this system. The blue-light response is elicited via the photoreceptor YtvA, which forms an integral part of stressosomes, to activate expression of the stress regulon of B. subtilis. Signal transfer through this network can be assayed with reporter enzymes, while intermediate steps can be studied with live-cell imaging of fluorescently tagged proteins. Different parts of this system have been studied in vitro, such that its computational modeling has made significant progress. One can directly relate the microscopic characteristics of YtvA with activation of the general stress regulon, making this system a very well-suited system for network evolution studies.
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Affiliation(s)
- Jeroen B van der Steen
- Molecular Microbial Physiology Group, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Klaas J Hellingwerf
- Molecular Microbial Physiology Group, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
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19
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Dahlsten E, Lindström M, Korkeala H. Mechanisms of food processing and storage-related stress tolerance in Clostridium botulinum. Res Microbiol 2014; 166:344-52. [PMID: 25303833 DOI: 10.1016/j.resmic.2014.09.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 09/26/2014] [Accepted: 09/26/2014] [Indexed: 12/28/2022]
Abstract
Vegetative cultures of Clostridium botulinum produce the extremely potent botulinum neurotoxin, and may jeopardize the safety of foods unless sufficient measures to prevent growth are applied. Minimal food processing relies on combinations of mild treatments, primarily to avoid deterioration of the sensory qualities of the food. Tolerance of C. botulinum to minimal food processing is well characterized. However, data on effects of successive treatments on robustness towards further processing is lacking. Developments in genetic manipulation tools and the availability of annotated genomes have allowed identification of genetic mechanisms involved in stress tolerance of C. botulinum. Most studies focused on low temperature, and the importance of various regulatory mechanisms in cold tolerance of C. botulinum has been demonstrated. Furthermore, novel roles in cold tolerance were shown for metabolic pathways under the control of these regulators. A role for secondary oxidative stress in tolerance to extreme temperatures has been proposed. Additionally, genetic mechanisms related to tolerance to heat, low pH, and high salinity have been characterized. Data on genetic stress-related mechanisms of psychrotrophic Group II C. botulinum strains are scarce; these mechanisms are of interest for food safety research and should thus be investigated. This minireview encompasses the importance of C. botulinum as a food safety hazard and its central physiological characteristics related to food-processing and storage-related stress. Special attention is given to recent findings considering genetic mechanisms C. botulinum utilizes in detecting and countering these adverse conditions.
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Affiliation(s)
- Elias Dahlsten
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, P. O. Box 66, FI-00014 Helsinki, Finland.
| | - Miia Lindström
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, P. O. Box 66, FI-00014 Helsinki, Finland.
| | - Hannu Korkeala
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, P. O. Box 66, FI-00014 Helsinki, Finland.
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21
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Alternative sigma factor SigK has a role in stress tolerance of group I Clostridium botulinum strain ATCC 3502. Appl Environ Microbiol 2013; 79:3867-9. [PMID: 23563953 DOI: 10.1128/aem.04036-12] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The role of the alternative sigma factor SigK in cold and osmotic stress tolerance of Clostridium botulinum ATCC 3502 was demonstrated by induction of sigK after temperature downshift and exposure to hyperosmotic conditions and by impaired growth of the sigK mutants under the respective conditions.
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22
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Abstract
Bacterial endospores are the most resistant cell type known to humans, as they are able to withstand extremes of temperature, pressure, chemical injury, and time. They are also of interest because the endospore is the infective particle in a variety of human and livestock diseases. Endosporulation is characterized by the morphogenesis of an endospore within a mother cell. Based on the genes known to be involved in endosporulation in the model organism Bacillus subtilis, a conserved core of about 100 genes was derived, representing the minimal machinery for endosporulation. The core was used to define a genomic signature of about 50 genes that are able to distinguish endospore-forming organisms, based on complete genome sequences, and we show this 50-gene signature is robust against phylogenetic proximity and other artifacts. This signature includes previously uncharacterized genes that we can now show are important for sporulation in B. subtilis and/or are under developmental control, thus further validating this genomic signature. We also predict that a series of polyextremophylic organisms, as well as several gut bacteria, are able to form endospores, and we identified 3 new loci essential for sporulation in B. subtilis: ytaF, ylmC, and ylzA. In all, the results support the view that endosporulation likely evolved once, at the base of the Firmicutes phylum, and is unrelated to other bacterial cell differentiation programs and that this involved the evolution of new genes and functions, as well as the cooption of ancestral, housekeeping functions.
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23
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Reder A, Albrecht D, Gerth U, Hecker M. Cross-talk between the general stress response and sporulation initiation inBacillus subtilis- the σBpromoter ofspo0Erepresents an AND-gate. Environ Microbiol 2012; 14:2741-56. [DOI: 10.1111/j.1462-2920.2012.02755.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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