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Selective Pressure for Biofilm Formation in Bacillus subtilis: Differential Effect of Mutations in the Master Regulator SinR on Bistability

Lookup NU author(s): Jan Kampf, Kerstin Kruse, Dr Robert Cleverley, Professor Rick Lewis

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

Biofilm formation by Bacillus subtilis requires the expression of genes encoding enzymes forextracellular polysaccharide synthesis and for an amyloid-like protein. The master regulator SinRrepresses all the corresponding genes, and repression of these key biofilm genes is lifted when SinRinteracts with its cognate antagonist proteins. The YmdB phosphodiesterase is a recently discoveredfactor that is involved in the control of SinR activity: cells lacking YmdB exhibit hyperactive SinR andare unable to relieve the repression of the biofilm genes. In this study, we have examined thedynamics of gene expression patterns in wild type and ymdB mutant cells by microfluidic analysiscoupled to time-lapse microscopy. Our results confirm the bistable expression pattern for motilityand biofilm genes in the wild type strain, and the loss of biofilm gene expression in the mutant.Moreover, we demonstrate dynamic behavior in subpopulations of the wild type strain that ischaracterized by switches in sets of the expressed genes. In order to gain further insights into therole of YmdB, we isolated a set of spontaneous suppressor mutants derived from ymdB mutants thathad regained the ability to form complex colonies and biofilms. Interestingly, all of the mutationsaffected SinR. In some mutants, large genomic regions encompassing sinR were deleted whereasothers had alleles encoding SinR variants. Functional and biochemical studies with these SinRvariants revealed how these proteins allowed biofilm gene expression in the ymdB mutant strains.

Publication metadata

Author(s): Kampf J, Gerwig J, Kruse K, Cleverley R, Dormeyer M, Grünberger A, Kohlheyer D, Commichau FM, Lewis RJ, Stülke J

Publication type: Article

Publication status: Published

Journal: mBio

Year: 2018

Volume: 9

Issue: 5

Online publication date: 04/09/2018

Acceptance date: 30/07/2018

Date deposited: 31/07/2018

ISSN (print): 2161-2129

ISSN (electronic): 2150-7511

Publisher: American Society for Microbiology

URL: https://doi.org/10.1128/mBio.01464-18

DOI: 10.1128/mBio.01464-18

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