ZnuABC and ZosA zinc transporters are differently involved in competence development in Bacillus subtilis

Disruptants of genes encoding the ZnuABC high-affinity zinc incorporator and zosA encoding a P-type ATPase for zinc incorporation were identified to show low transformability. The low transformability of the znuB cells was rescued by excess zinc addition and epistatic analysis of the mutation revealed no effect on the expression of comK, which encodes a master regulator for late com operons. We further examined the expression of each late com operon in the znuA mutant and found that the znuA mutation specifically inhibited the expression of comF, but not the other late com operons. The addition of zinc also rescued the low transformability of the zosA cells. In zosA cells, transcription of comK was severely repressed. Using a strain carrying comK driven by a xylose-inducible promoter, we showed that the zosA mutation inhibited the post-transcriptional control of comK. The addition of zinc also rescued the defect of xylose-inducible comK expression in zosA cells, suggesting that post-transcriptional control of comK requires zinc incorporation. Taken together, we propose that the both ZnuABC- and ZosA-mediated zinc incorporation is involved in competence development, although the two zinc transporters are differently implicated in this developmental process.