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

Abstract

Streptomyces coelicolor A3(2) strain M145 has eight chitinase genes scattered 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 regulation 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 genes, but significantly earlier than did colloidal chitin. When cells were cultured in the presence of colloidal chitin, an exponential increase of chitobiose concentration in the culture supernatant was observed prior to the induced transcription of the chi genes. This result, together with the immediate effect of chitobiose on the induction, suggests that chitobiose produced from colloidal chitin is involved in the induction of transcription of the chi genes. The transcription of the five chi genes was repressed by glucose. This repression was apparently mediated by the glucose kinase gene glkA.

The dasABC Gene Cluster, Adjacent to dasR , Encodes a Novel ABC Transporter for the Uptake of N , N ′-Diacetylchitobiose in Streptomyces coelicolor A3(2)

“…To investigate the responses of the cells to sugars, S. coelicolor A3(2) M145 and its mutant were cultivated by following a method described previously (30), with some modifications. Spores of S. coelicolor A3(2) strains formed on SFM agar medium were inoculated into 30 ml LB medium in a 100-ml flask with a spring (13) and grown for 19 h at 30°C on a rotary shaker at 150 rpm.…”

“…It is therefore believed that the DR-like sequences are common cis-acting elements involved in the regulation of chitinase genes in streptomycetes. The transcription of chi genes in S. coelicolor A3 (2) and S. lividans is induced by (GlcNAc) 2 as well as by chitin (17,30). Because of the more immediate induction activity of (GlcNAc) 2 , it has been suggested that (GlcNAc) 2 production, which occurs by hydrolysis of chitin, is necessary for the induction of chi gene expression (30).…”

“…Streptomyces coelicolor A3(2) strain M145 possesses 13 chitinase (chi) genes in its genome, although 6 of them are putative ones (2,6,12,29). The expression of five chi genes (chiA, chiB, chiC, chiD, and chiF) is induced by chitin in the bacterium (30), and each of the chitinases (ChiA, ChiC, ChiD, and ChiF) has its own enzymatic properties (12). It is assumed that these chitinases act synergistically with each other in chitin degradation, as has been reported in the chitinase system of a marine bacterium, Alteromonas sp.…”

Comparison of Enzymatic and Antifungal Properties between Family 18 and 19 Chitinases fromS. coelicolorA3(2)

“…Saito et al examined transcription of eight chitinase genes in the presence and absence of colloidal chitin and found that the transcription of five genes (chi18bA, chi18bB, chi18aC, chi18aD, and chi19F) increased in the presence of colloidal chitin 33) while that of the other three genes did not. The induced levels of the transcripts of chi18bB were significantly lower than those of the other four genes.…”

Molecular Analysis of a Bacterial Chitinolytic Community in an Upland Pasture

“…The most information on bacterial diversity and distribution is available for group A chitinases; this may be because groups B and C are less prevalent in nature. Cloning and sequencing have revealed that many bacteria such as Streptomyces coelicolor A3 (2) possess multiple chitinases, including some in each of these subgroups (30,31). The complexity of chitin as a substrate might explain why many bacteria possess multiple chitinases that facilitate degradation in a synergistic manner.…”