Inhibition of Bacillus subtilis natural competence by a native, conjugative plasmid-encoded comK repressor protein.
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.
Centro de Biología Molecular Severo Ochoa, Instituto de Biología Molecular Eladio Viñuela, Universidad Autónoma, Canto Blanco, 28049 Madrid, Spain.
Praveen K
PK
Singh
Gayetri
G
Ramachandran
Lucía
L
Durán-Alcalde
Carlos
C
Alonso
Ling Juan
LJ
Wu
Wilfried J J
WJ
Meijer
D001412:Bacillus subtilis / Q000235:genetics* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D061269:DNA Transformation Competence / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism
D001426:Bacterial Proteins; D012097:Repressor Proteins; D014157:Transcription Factors