Genetic evidence for a novel competence inhibitor in the industrially important Bacillus licheniformis

Christine Muth,Friedhelm Meinhardt,Christina Schmidt,Sonja Volland,Meike Buchholz

doi:10.1186/s13568-017-0447-5

Christine Muth, Friedhelm Meinhardt + Show 3 more

Open Access

https://doi.org/10.1186/s13568-017-0447-5

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Journal: AMB Express	Publication Date: Jul 11, 2017
Citations: 3	License type: open-access

Affiliation: University of Münster, University of Göttingen

Abstract

Natural genetic competence renders bacteria able to take up and, in case there is sufficient homology to the recipient’s chromosome, integrate exogenously supplied DNA. Well studied in Bacillus subtilis, genetic competence is—in several aspects—known to be differently regulated in Bacillus licheniformis. We now report on the identification of a novel, chromosomally encoded homolog of a competence inhibitor in B. licheniformis (ComI) that has hitherto only been described as a plasmid borne trait in the ancestral B. subtilis NCIB3610. Bioinformatical analysis that included 80 Bacillus strains covering 20 different species revealed a ComI encoding gene in all of the examined B. licheniformis representatives, and was identified in few among the other species investigated. The predicted ComI of B. licheniformis is a highly conserved peptide consisting of 28 amino acids. Since deletion of comI in B. licheniformis DSM13 resulted in twofold increased transformation efficiency by genetic competence and overexpression resulted in threefold decreased transformability, the function as a competence inhibitor became evident.

Highlights

Various bacterial species can develop natural genetic competence, a physiological state that enables cells to take up DNA (Dubnau 1999; Johnsborg et al 2007)
When bioinformatical analyses were performed, including altogether 80 Bacillus strains from 20 different genera, a putative competence inhibitor in B. licheniformis (ComI) encoding gene (comI) gene was identified for all 14 B. licheniformis strains included in the survey, whereas it was rather rarely seen in the other Bacillus strains tested (i.e. 4 representatives; see Fig. 1)
The predicted ComI of B. licheniformis is a highly conserved protein consisting of 28 aa (VTVSEALQLMVSFGILVVAILSSNDKKK)

Summary

Introduction

Various bacterial species can develop natural genetic competence, a physiological state that enables cells to take up DNA (Dubnau 1999; Johnsborg et al 2007). The regulatory system governing genetic competence has been studied rather thoroughly in the gram-positive model organism Bacillus subtilis (Dubnau 1999; Hamoen et al 2003; Spizizen 1958). The development of natural genetic competence in B. subtilis depends on environmental stimuli such as nutritional limitation and/or cell density (Hamoen et al 2003). Removing the insertion element (and thereby restoring an active copy of comP) resulted in reduced genetic competence (Hoffmann et al 2010), which clearly differs from B. subtilis. Further regulatory differences concern ComS action (Jakobs et al 2015), as the two ComS homologs identified in B. licheniformis did not impact—contrary to B. subtilis—the development of genetic competence

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