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

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.Electronic supplementary materialThe online version of this article (doi:10.1186/s13568-017-0447-5) contains supplementary material, which is available to authorized users.

The Large pBS32/pLS32 Plasmid of Ancestral Bacillus subtilis

“…Moreover, homologs of ComI are encoded in the chromosomes of Bacillus, Enterococcus, and Streptococcus, but a comprehensive bioinformatic and functional analysis is needed to determine whether or not they are encoded within horizontally transferred elements and/or have major effects on transformation efficiency (Fig. 4A) (25,108). Thus, the reason that bacteria encode ComI homologs and other competence inhibitors is presently unknown, but we suspect such inhibitors are more common than currently recognized.…”

Development and application of CRISPR-based genetic tools in Bacillus species and Bacillus phages

“…In B. licheniformis , the Cas9‐, dCas9‐ and Cas9n‐mediated genetic tools have been developed (Li et al, 2020 ; Li, Cai, et al, 2018 ; Zhan et al, 2020 ; Zhou et al, 2019 ). In species with a low transformation rate, two main factors should be considered: the vector size and the expression of the genes these vectors carry (Muth et al, 2017 ; Waschkau et al, 2008 ). When a genome‐integrated Cas9n was employed, this decreased the gene editing plasmid capacity (Li, Cai, et al, 2018 ).…”