Impaired competence in flagellar mutants ofBacillus subtilisis connected to the regulatory network governed by DegU

Abstract

The competent state is a developmentally distinct phase, in which bacteria are able to take up and integrate exogenous DNA into their genome. Bacillus subtilis is one of the naturally competent bacterial species and the domesticated laboratory strain 168 is easily transformable. In this study, we report a reduced transformation frequency of B. subtilis mutants lacking functional and structural flagellar components. This includes hag, the gene encoding the flagellin protein forming the filament of the flagellum. We confirm that the observed decrease of the transformation frequency is due to reduced expression of competence genes, particularly of the main competence regulator comK. The impaired competence is due to an increase in the phosphorylated form of the response regulator DegU, which is involved in regulation of both flagellar motility and competence.Altogether, our study identified a close link between motility and natural competence in B. subtilis suggesting that hindrance in motility has great impact on differentiation of this bacterium not restricted only to the transition towards sessile growth stage.

Experimental Evolution of Bacillus subtilis Reveals the Evolutionary Dynamics of Horizontal Gene Transfer and Suggests Adaptive and Neutral Effects

“…Most of the flagellar mutations were non-synonymous, strongly indicating that mutating the flagella is likely to be beneficial. In addition to its role in enabling motility, maintaining an active flagellum is essential for the activation of the competence system by affecting the phosphorylation status of DegU, a master regulator of competence in Bacillus subtilis (Diethmaier et al 2017;Hölscher et al 2018). Thus, two types of driving forces may account for the fixation of flagellar mutations in our experiment: reducing the large cellular cost of generating and maintaining active flagella under conditions in which motility is not needed, and reducing the cost originating from switching into a competence state (Haijema et al 2001).…”