Two types of transcriptional repression in living cells of Bacillus subtilis characterized by number and brightness analysis Ferguson , Matthew L. (Centre National de la Recherche ScientifiqueInstitut National de la Santé et de la Recherche MédicaleUniversité de Montpellier, Montpellier MontpellierMontpellier(France).); Le Coq , Dominique (INRA , Jouy-En-Josas (France). UMR 1319 MICrobiologie de l'ALImentation au Service de la Santé Humaine); Jules , Matthieu (INRA , Jouy-En-Josas (France). UMR 1319 MICrobiologie de l'ALImentation au Service de la Santé Humaine) ...
2011
Conference Proceeding
Division in Escherichia coli is triggered by a size-sensing rather than a timing mechanism Robert , Lydia (INRA , Jouy-En-Josas (France). UMR 1319 MICrobiologie de l'ALImentation au Service de la Santé Humaine); Hoffmann , Marc (Université Paris Dauphine (Paris 9), Paris(France). UMR 7534); Krell , Nathalie (Université de Rennes 1, Rennes(France). UMR 6625) ...
http://www.biomedcentral.com/bmcbiol,
2014, Letnik:
1
Publication
Background: Many organisms coordinate cell growth and division through size control mechanisms: cells must reach a critical size to trigger a cell cycle event. Bacterial division is often assumed to ...be controlled in this way, but experimental evidence to support this assumption is still lacking. Theoretical arguments show that size control is required to maintain size homeostasis in the case of exponential growth of individual cells. Nevertheless, if the growth law deviates slightly from exponential for very small cells, homeostasis can be maintained with a simple 'timer' triggering division. Therefore, deciding whether division control in bacteria relies on a 'timer' or 'sizer' mechanism requires quantitative comparisons between models and data.br/Results: The timer and sizer hypotheses find a natural expression in models based on partial differential equations. Here we test these models with recent data on single-cell growth of Escherichia coli. We demonstrate that a size-independent timer mechanism for division control, though theoretically possible, is quantitatively incompatible with the data and extremely sensitive to slight variations in the growth law. In contrast, a sizer model is robust and fits the data well. In addition, we tested the effect of variability in individual growth rates and noise in septum positioning and found that size control is robust to this phenotypic noise.br/Conclusions: Confrontations between cell cycle models and data usually suffer from a lack of high-quality data and suitable statistical estimation techniques. Here we overcome these limitations by using high precision measurements of tens of thousands of single bacterial cells combined with recent statistical inference methods to estimate the division rate within the models. We therefore provide the first precise quantitative assessment of different cell cycle models.
Transcriptional regulation is insufficient to explain substrate-induced flux changes in Bacillus subtilis Chubukov , Victor (ETH Zürich, Zürich(Suisse). Institute of Molecular System Biology); Uhr , Markus (ETH Zürich, Zurich(Suisse). Swiss Institute of Bioinformatics, Department of Biosystems Science and Engineering); Le Chat , Ludovic (INRA , Jouy-En-Josas (France). UMR 1319 MICrobiologie de l'ALImentation au Service de la Santé Humaine) ...
http://msb.embopress.org,
2013
Publication
One of the key ways in which microbes are thought to regulate their metabolism is by modulating the availability of enzymes through transcriptional regulation. However, the limited success of efforts ...to manipulate metabolic fluxes by rewiring the transcriptional network has cast doubt on the idea that transcript abundance controls metabolic fluxes. In this study, we investigate control of metabolic flux in the model bacterium Bacillus subtilis by quantifying fluxes, transcripts, and metabolites in eight metabolic states enforced by different environmental conditions. We find that most enzymes whose flux switches between on and off states, such as those involved in substrate uptake, exhibit large corresponding transcriptional changes. However, for the majority of enzymes in central metabolism, enzyme concentrations were insufficient to explain the observed fluxes-only for a number of reactions in the tricarboxylic acid cycle were enzyme changes approximately proportional to flux changes. Surprisingly, substrate changes revealed by metabolomics were also insufficient to explain observed fluxes, leaving a large role for allosteric regulation and enzyme modification in the control of metabolic fluxes.
Biofilms of a Bacillus subtilis hospital isolate protect Staphylococcus aureus from biocide action Bridier , Arnaud (INRA , Jouy-En-Josas (France). UMR 1319 MICrobiologie de l'ALImentation au Service de la Santé Humaine); Sanchez-Vizuete , Maria Del Pilar (INRA , Jouy-En-Josas (France). UMR 1319 MICrobiologie de l'ALImentation au Service de la Santé Humaine); Le Coq , Dominique (INRA , Jouy-En-Josas (France). UMR 1319 MICrobiologie de l'ALImentation au Service de la Santé Humaine) ...
2012
Publication
The development of a biofilm constitutes a survival strategy by providing bacteria a protective environment safe from stresses such as microbicide action and can thus lead to important health-care ...problems. In this study, biofilm resistance of a Bacillus subtilis strain (called hereafter ND(medical)) recently isolated from endoscope washer-disinfectors to peracetic acid was investigated and its ability to protect the pathogen Staphylococcus aureus in mixed biofilms was evaluated. Biocide action within Bacillus subtilis biofilms was visualised in real time using a non-invasive 4D confocal imaging method. The resistance of single species and mixed biofilms to peracetic acid was quantified using standard plate counting methods and their architecture was explored using confocal imaging and electronic microscopy. The results showed that the ND(medical) strain demonstrates the ability to make very large amount of biofilm together with hyper-resistance to the concentration of PAA used in many formulations (3500 ppm). Evidences strongly suggest that the enhanced resistance of the ND(medical) strain was related to the specific three-dimensional structure of the biofilm and the large amount of the extracellular matrix produced which can hinder the penetration of peracetic acid. When grown in mixed biofilm with Staphylococcus aureus, the ND(medical) strain demonstrated the ability to protect the pathogen from PAA action, thus enabling its persistence in the environment. This work points out the ability of bacteria to adapt to an extremely hostile environment, and the necessity of considering multi-organism ecosystems instead of single species model to decipher the mechanisms of biofilm resistance to antimicrobials agents.
Malate-mediated carbon catabolite repression in bacillus subtilis involves the HPrK/CcpA pathway Meyer , Frederik M. (University of Göttingen, Gottingen(Allemagne). Department of General Microbiology, Institute of Microbiology and Genetics); Jules , Matthieu (INRA , Jouy-En-Josas (France). UMR 1319 MICrobiologie de l'ALImentation au Service de la Santé Humaine); Mehne , Felix M. P. (University of Göttingen, Gottingen(Allemagne). Department of General Microbiology, Institute of Microbiology and Genetics) ...
2011
Publication
Most organisms can choose their preferred carbon source from a mixture of nutrients. This process is called carbon catabolite repression. The Gram-positive bacterium Bacillus subtilis uses glucose as ...the preferred source of carbon and energy. Glucose-mediated catabolite repression is caused by binding of the CcpA transcription factor to the promoter regions of catabolic operons. CcpA binds DNA upon interaction with its cofactors HPr(Ser-P) and Crh(Ser-P). The formation of the cofactors is catalyzed by the metabolite-activated HPr kinase/ phosphorylase. Recently, it has been shown that malate is a second preferred carbon source for B. subtilis that also causes catabolite repression. In this work, we addressed the mechanism by which malate causes catabolite repression. Genetic analyses revealed that malate-dependent catabolite repression requires CcpA and its cofactors. Moreover, we demonstrate that HPr(Ser-P) is present in malate-grown cells and that CcpA and HPr interact in vivo in the presence of glucose or malate but not in the absence of a repressing carbon source. The formation of the cofactor HPr(Ser-P) could be attributed to the concentrations of ATP and fructose 1,6-bisphosphate in cells growing with malate. Both metabolites are available at concentrations that are sufficient to stimulate HPr kinase activity. The adaptation of cells to environmental changes requires dynamic metabolic and regulatory adjustments. The repression strength of target promoters was similar to that observed in steady-state growth conditions, although it took somewhat longer to reach the second steady-state of expression when cells were shifted to malate.
Reconstruction and analysis of the genetic and metabolic regulatory networks of the central metabolism of Bacillus subtilis Goelzer , Anne (INRA , Jouy-En-Josas (France). UR 1077 Mathématique, Informatique et Génome); Bekkal Brikci , Fadia (INRA , Jouy-En-Josas (France). UR 1077 Mathématique, Informatique et Génome); Martin-Verstraete , Isabelle (Institut PasteurUniversité Paris 7, ParisParis(France). URA CNRS 2171 Unité de Génétique des Génomes BactériensUnité de Formation et de Recherche de Biochimie) ...
2008
Publication
Background. Few genome-scale models of organisms focus on the regulatory networks and none of them integrates all known levels of regulation. In particular, the regulations involving metabolite pools ...are often neglected. However, metabolite pools link the metabolic to the genetic network through genetic regulations, including those involving effectors of transcription factors or riboswitches. Consequently, they play pivotal roles in the global organization of the genetic and metabolic regulatory networks. Results. We report the manually curated reconstruction of the genetic and metabolic regulatory networks of the central metabolism of Bacillus subtilis (transcriptional, translational and post-translational regulations and modulation of enzymatic activities). We provide a systematic graphic representation of regulations of each metabolic pathway based on the central role of metabolites in regulation. We show that the complex regulatory network of B. subtilis can be decomposed as sets of locally regulated modules, which are coordinated by global regulators. Conclusion. This work reveals the strong involvement of metabolite pools in the general regulation of the metabolic network. Breaking the metabolic network down into modules based on the control of metabolite pools reveals the functional organization of the genetic and metabolic regulatory networks of B. subtilis
