Stress induction of clpC in Bacillus subtilis and its involvement in stress tolerance

A member of the clpC subfamily of stress response-related Clp ATPases was cloned from Bacillus subtilis. The B. subtilis cIpC gene was induced in response to various stresses, including heat shock. Its product was identified as a general stress protein (Gspl2) described previously. A dramatic increase in the amount of clpC mRNA immediately after exposure to multiple stresses suggested regulation on a transcriptional level. Induction by heat shock was independent of the alternative sigma factor SigB, indicating a new mechanism of heat shock induction in B. subtilis. A clpC insertional mutant had an impaired tolerance for heat shock and salt stress. Furthermore, the mutation triggered the formation of elongated cells, a phenomenon particularly pronounced during stress. The Clp proteins constitute a family of proteins which are highly conserved and universal (for reviews, see references 14 and 39). Members of this family have been shown to exist in Escherichia coli (40), Streptococcus mutans (37), Streptococcus pneumoniae (29), Bacteroides nodosus (22), Mycobacterium leprae (27), and Rhodopseudomonas blastica (44) and in severa