Selective Pressure for Biofilm Formation in <named-content content-type="genus-species">Bacillus subtilis</named-content>: Differential Effect of Mutations in the Master Regulator SinR on Bistability

ABSTRACT Biofilm formation by Bacillus subtilis requires the expression of genes encoding enzymes for extracellular polysaccharide synthesis and for an amyloid-like protein. The master regulator SinR represses all the corresponding genes, and repression of these key biofilm genes is lifted when SinR...

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Autores principales:	Jan Kampf, Jan Gerwig, Kerstin Kruse, Robert Cleverley, Miriam Dormeyer, Alexander Grünberger, Dietrich Kohlheyer, Fabian M. Commichau, Richard J. Lewis, Jörg Stülke
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2018
Materias:	biofilm formation bistability gene expression microfluidics suppressor mutants Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/0d8fed822050435b9c9bc4439edaff25
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spelling	oai:doaj.org-article:0d8fed822050435b9c9bc4439edaff252021-11-15T15:58:20ZSelective Pressure for Biofilm Formation in <named-content content-type="genus-species">Bacillus subtilis</named-content>: Differential Effect of Mutations in the Master Regulator SinR on Bistability10.1128/mBio.01464-182150-7511https://doaj.org/article/0d8fed822050435b9c9bc4439edaff252018-11-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.01464-18https://doaj.org/toc/2150-7511ABSTRACT Biofilm formation by Bacillus subtilis requires the expression of genes encoding enzymes for extracellular polysaccharide synthesis and for an amyloid-like protein. The master regulator SinR represses all the corresponding genes, and repression of these key biofilm genes is lifted when SinR interacts with its cognate antagonist proteins. The YmdB phosphodiesterase is a recently discovered factor that is involved in the control of SinR activity: cells lacking YmdB exhibit hyperactive SinR and are unable to relieve the repression of the biofilm genes. In this study, we have examined the dynamics of gene expression patterns in wild-type and ymdB mutant cells by microfluidic analysis coupled to time-lapse microscopy. Our results confirm the bistable expression pattern for motility and biofilm genes in the wild-type strain and the loss of biofilm gene expression in the mutant. Moreover, we demonstrated dynamic behavior in subpopulations of the wild-type strain that is characterized by switches in sets of the expressed genes. In order to gain further insights into the role of YmdB, we isolated a set of spontaneous suppressor mutants derived from ymdB mutants that had regained the ability to form complex colonies and biofilms. Interestingly, all of the mutations affected SinR. In some mutants, large genomic regions encompassing sinR were deleted, whereas others had alleles encoding SinR variants. Functional and biochemical studies with these SinR variants revealed how these proteins allowed biofilm gene expression in the ymdB mutant strains. IMPORTANCE Many bacteria are able to choose between two mutually exclusive lifestyles: biofilm formation and motility. In the model bacterium Bacillus subtilis, this choice is made by each individual cell rather than at the population level. The transcriptional repressor SinR is the master regulator in this decision-making process. The regulation of SinR activity involves complex control of its own expression and of its interaction with antagonist proteins. We show that the YmdB phosphodiesterase is required to allow the expression of SinR-repressed genes in a subpopulation of cells and that such subpopulations can switch between different SinR activity states. Suppressor analyses revealed that ymdB mutants readily acquire mutations affecting SinR, thus restoring biofilm formation. These findings suggest that B. subtilis cells experience selective pressure to form the extracellular matrix that is characteristic of biofilms and that YmdB is required for the homeostasis of SinR and/or its antagonists.Jan KampfJan GerwigKerstin KruseRobert CleverleyMiriam DormeyerAlexander GrünbergerDietrich KohlheyerFabian M. CommichauRichard J. LewisJörg StülkeAmerican Society for Microbiologyarticlebiofilm formationbistabilitygene expressionmicrofluidicssuppressor mutantsMicrobiologyQR1-502ENmBio, Vol 9, Iss 5 (2018)
institution	DOAJ
collection	DOAJ
language	EN
topic	biofilm formation bistability gene expression microfluidics suppressor mutants Microbiology QR1-502
spellingShingle	biofilm formation bistability gene expression microfluidics suppressor mutants Microbiology QR1-502 Jan Kampf Jan Gerwig Kerstin Kruse Robert Cleverley Miriam Dormeyer Alexander Grünberger Dietrich Kohlheyer Fabian M. Commichau Richard J. Lewis Jörg Stülke Selective Pressure for Biofilm Formation in <named-content content-type="genus-species">Bacillus subtilis</named-content>: Differential Effect of Mutations in the Master Regulator SinR on Bistability
description	ABSTRACT Biofilm formation by Bacillus subtilis requires the expression of genes encoding enzymes for extracellular polysaccharide synthesis and for an amyloid-like protein. The master regulator SinR represses all the corresponding genes, and repression of these key biofilm genes is lifted when SinR interacts with its cognate antagonist proteins. The YmdB phosphodiesterase is a recently discovered factor that is involved in the control of SinR activity: cells lacking YmdB exhibit hyperactive SinR and are unable to relieve the repression of the biofilm genes. In this study, we have examined the dynamics of gene expression patterns in wild-type and ymdB mutant cells by microfluidic analysis coupled to time-lapse microscopy. Our results confirm the bistable expression pattern for motility and biofilm genes in the wild-type strain and the loss of biofilm gene expression in the mutant. Moreover, we demonstrated dynamic behavior in subpopulations of the wild-type strain that is characterized by switches in sets of the expressed genes. In order to gain further insights into the role of YmdB, we isolated a set of spontaneous suppressor mutants derived from ymdB mutants that had regained the ability to form complex colonies and biofilms. Interestingly, all of the mutations affected SinR. In some mutants, large genomic regions encompassing sinR were deleted, whereas others had alleles encoding SinR variants. Functional and biochemical studies with these SinR variants revealed how these proteins allowed biofilm gene expression in the ymdB mutant strains. IMPORTANCE Many bacteria are able to choose between two mutually exclusive lifestyles: biofilm formation and motility. In the model bacterium Bacillus subtilis, this choice is made by each individual cell rather than at the population level. The transcriptional repressor SinR is the master regulator in this decision-making process. The regulation of SinR activity involves complex control of its own expression and of its interaction with antagonist proteins. We show that the YmdB phosphodiesterase is required to allow the expression of SinR-repressed genes in a subpopulation of cells and that such subpopulations can switch between different SinR activity states. Suppressor analyses revealed that ymdB mutants readily acquire mutations affecting SinR, thus restoring biofilm formation. These findings suggest that B. subtilis cells experience selective pressure to form the extracellular matrix that is characteristic of biofilms and that YmdB is required for the homeostasis of SinR and/or its antagonists.
format	article
author	Jan Kampf Jan Gerwig Kerstin Kruse Robert Cleverley Miriam Dormeyer Alexander Grünberger Dietrich Kohlheyer Fabian M. Commichau Richard J. Lewis Jörg Stülke
author_facet	Jan Kampf Jan Gerwig Kerstin Kruse Robert Cleverley Miriam Dormeyer Alexander Grünberger Dietrich Kohlheyer Fabian M. Commichau Richard J. Lewis Jörg Stülke
author_sort	Jan Kampf
title	Selective Pressure for Biofilm Formation in <named-content content-type="genus-species">Bacillus subtilis</named-content>: Differential Effect of Mutations in the Master Regulator SinR on Bistability
title_short	Selective Pressure for Biofilm Formation in <named-content content-type="genus-species">Bacillus subtilis</named-content>: Differential Effect of Mutations in the Master Regulator SinR on Bistability
title_full	Selective Pressure for Biofilm Formation in <named-content content-type="genus-species">Bacillus subtilis</named-content>: Differential Effect of Mutations in the Master Regulator SinR on Bistability
title_fullStr	Selective Pressure for Biofilm Formation in <named-content content-type="genus-species">Bacillus subtilis</named-content>: Differential Effect of Mutations in the Master Regulator SinR on Bistability
title_full_unstemmed	Selective Pressure for Biofilm Formation in <named-content content-type="genus-species">Bacillus subtilis</named-content>: Differential Effect of Mutations in the Master Regulator SinR on Bistability
title_sort	selective pressure for biofilm formation in <named-content content-type="genus-species">bacillus subtilis</named-content>: differential effect of mutations in the master regulator sinr on bistability
publisher	American Society for Microbiology
publishDate	2018
url	https://doaj.org/article/0d8fed822050435b9c9bc4439edaff25
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Selective Pressure for Biofilm Formation in <named-content content-type="genus-species">Bacillus subtilis</named-content>: Differential Effect of Mutations in the Master Regulator SinR on Bistability

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