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Inhibition of Bacillus subtilis natural competence by a native, conjugative plasmid‐encoded comK repressor protein
Author(s) -
Singh Praveen K.,
Ramachandran Gayetri,
DuránAlcalde Lucía,
Alonso Carlos,
Wu Ling Juan,
Meijer Wilfried J. J.
Publication year - 2012
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/j.1462-2920.2012.02819.x
Subject(s) - biology , plasmid , bacillus subtilis , gene , repressor , genetics , promoter , gene expression , bacteria
Summary Under certain growth conditions, Bacillus subtilis can develop natural competence, the state in which it is able to bind, adsorb and incorporate exogenous DNA. Development of competence is a bistable process and is subject to complex regulation. Rok is a repressor of the key transcriptional activator of competence genes, comK , and limits the size of the subpopulation that develops competence. Here we report the finding that the large conjugative B. subtilis plasmid pLS20 harbours a rok homologue rok LS20 . Although the deduced product of rok LS20 is considerably shorter than the chromosomally encoded Rok protein, we show that ectopic expression of the plasmid‐encoded Rok LS20 leads to inhibition of competence by repressing comK , and that the effects of the plasmid and chromosomally encoded Rok proteins are additive. We also show that pLS20 inhibits competence in a rok LS20 ‐dependent manner and that purified Rok LS20 preferentially binds to the comK promoter. By analysing the available databases we identified several additional rok ‐like genes. These putative rok genes can be divided into two groups and we propose that rok LS20 is the prototype of a newly identified subgroup of nine rok genes. Finally, we discuss the possible role of the plasmid‐located rok and its relatedness with other rok genes.