Chance and Necessity inBacillus subtilisDevelopment

Abstract

Bacillus subtilis is an important model bacterium for the study of developmental adaptations that enhance survival in the face of fluctuating environmental challenges. These adaptations include sporulation, biofilm formation, motility, cannibalism, and competence. Remarkably, not all the cells in a given population exhibit the same response. The choice of fate by individual cells is random but is also governed by complex signal transduction pathways and cross talk mechanisms that reinforce decisions once made. The interplay of stochastic and deterministic mechanisms governing the selection of developmental fate on the single-cell level is discussed in this article. Everything existing in the universe is the fruit of chance and necessity. DEMOCRITUS (as quoted by J. Monod) Biologists often think of regulation as deterministic; causes have invariant consequences, and changes predictably beget further changes. However, with the advent of techniques for the study of individual cell phenotypes, it has become evident that random cell-to-cell variation in the amounts of mRNA and protein is prevalent and often entails significant consequences, particularly for developmental processes (1, 2). This review focuses on the developmental pathways of Bacillus subtilis, with attention to the roles of this variation and of stochastic reactions in competence, motility, sporulation, and biofilm formation. We do not comprehensively review the regulatory mechanisms that control these pathways but present only what is needed for our purposes. Figure 1 identifies the major players that are discussed below and illustrates the competence, motility, cannibalism, biofilm, and sporulation modules that represent the major known developmental pathways of B. subtilis. When a cell population bifurcates into two sub-populations that differ in their patterns of transcription, we use the term bimodal to describe the distribution of gene expression among the cells. The term bistable is reserved for a bimodal population in which the different cell types can be epigenetically inherited. Noise, or cell-to-cell variation in the abundance of gene products, results from the stochastic nature of chemical reactions and becomes important when small numbers of reactants are involved (3, 4). Noise in gene expression

Surfactin: A Quorum-Sensing Signal Molecule to Relieve CCR in Bacillus amyloliquefaciens

“…The srfA mutant does not stop only growth but starts to lyse immediately after 12 h. Thereby, in order to survival the cells of srfA would search for a new environment with enough glucose. Indeed, many genes transcription involved in chemotaxis and motility (Mirouze and Dubnau, 2013;van Gestel et al, 2015), were significantly up-regulated in srfA. The result is consistent with the previous report that after nutrients limitation, B. subtilis could synthesize a complex motility and chemotaxis system searching for nutrients in the environment (Hamoen et al, 2003).…”

Effect of Long-Term Farming Practices on Agricultural Soil Microbiome Members Represented by Metagenomically Assembled Genomes (MAGs) and Their Predicted Plant-Beneficial Genes

“…MAG_08 was classified to the family Bacillaceae (phylum Firmicutes ) with 70.4% of its genes being assigned to the tentative taxon ‘unclassified Bacillaceae ’ at the genus level. Members of the family Bacillaceae are mostly aerobic heterotrophic saprophytes well known for their ecosystem functions in their primary habitat soil [94,95]. These functions include plant–growth–promotion and biocontrol, as well as functions in the carbon and nitrogen cycle.…”

To Sporulate or not to Sporulate: Prevalence of Endospore-Forming Firmicutes along a Thermal Gradient in Alexandros Crater (Nisyros, Greece)

“…As endospore-formation is a complex and highly costly procedure (Errington, 2003), it should be favored and prevalent in extreme environments (Abecasis et al, 2013). Indeed, it is a last resort solution, only when other strategies, such as biofilm formation or chemotaxis for example, fail (Mirouze & Dubnau, 2013). It has been shown that only the co-existence of multiple limiting factors increases the relative abundance of EFF in natural springs (Filippidou et al, In preparation).…”

“…In order to survive in extreme environments such as volcanic fields, microorganisms have developed diverse survival strategies (Roszak & Colwell, 1987, Mirouze & Dubnau, 2013) such as biofilm formation (Kreft, 2004), morphological plasticity (Justice et al, 2008) or posttranscriptional modifications (Zhao et al, 2002). Another of these strategies that can ensure survival under extreme environmental conditions is endospore formation in Endospore-forming Firmicutes (EFF) (Onyenwoke et al, 2004).…”