Transcriptional co-regulation of five chitinase genes scattered on the Streptomyces coelicolor A3(2) chromosome

Streptomyces coelicolor A3(2) strain M145 has eight chitinase genes scatter ed on the chromosome: six genes for family 18 (chiA, B, C, D, E and H) and two for family 19 (chiF and G). In this study, the expression and regulatio n of these genes were investigated. The transcription of five of the genes (chiA, B, C, D and F) was induced in the presence of colloidal chitin while that of the other three genes (chiE, G and H) was not. The transcripts of the five induced chi genes increased and reached their maximum at 4 h after the addition of colloidal chitin, all showing the same temporal patterns. The induced levels of the transcripts of chiB were significantly lower than those of the other four genes. Dynamic analysis of the transcripts of the chi genes indicated that chiA and chiC were induced more strongly than chiD and chiF. Addition of chitobiose also induced transcription of the chi gen es, but significantly earlier than did colloidal chitin. When cells were cu ltured in the presence of colloidal chitin, an exponential increase of chit obiose concentration in the culture supernatant was observed prior to the i nduced transcription of the chi genes. This result, together with the immed iate effect of chitobiose on the induction, suggests that chitobiose produc ed from colloidal chitin is involved in the induction of transcription of t he chi genes. The transcription of the five chi genes was repressed by gluc ose. This repression was apparently mediated by the glucose kinase gene glk A.