Involvement of the sigma factor sigma H in the regulation of a small heat shock protein gene in Lactobacillus plantarum WCFS1

The relative expression of the heat shock protein hsp18.55 gene was monitored in Lactobacillus plantarum Delta ctsR and Delta ftsH mutant strains. Transcription of the hsp18.55 gene was drastically repressed in the Delta ctsR mutant of L. plantarum; conversely, significant transcriptional induction of the hsp18.55 gene was noted in the L. plantarum Delta ftsH strain. Overall, these results suggest a possible regulation of the hsp18.55 gene by the alternative sigma H factor in L. plantarum. We also noted a similarity with the small heat shock gene (shs) locus of Lactobacillus brevis, which might indicate a possible evolutionary relationship.