glkA is involved in glucose repression of chitinase production in Streptomyces lividans

Abstract

Chitinase production in Streptomyces lividans is induced by chitin and repressed in the presence of glucose. A mutant of S. lividans TK24, strain G015, which was defective in glucose repression of chitinase production, was obtained by screening colonies for zones of clearing on colloidal chitin agar plates containing 1.0% (wt/vol) glucose. The transcriptional analysis of chiA in G015 with xylE, which encodes catechol 2,3-dioxygenase, as a reporter gene showed that the transcription from the chiA promoter of S. lividans TK24 occurred regardless of the presence of glucose. G015 was resistant to 2-deoxyglucose (2-DOG) and did not utilize glucose as a sole carbon source. When a DNA fragment containing glkA, a gene for glucose kinase, of Streptomyces coelicolor A3(2) was introduced into strain G015 on a low-copy-number plasmid, the sensitivity to 2-DOG, the ability to utilize glucose, and the glucose repression of chitinase production were restored. These results indicate that glkA is involved in glucose repression of chitinase production in S. lividans TK24.

FIG. 1

Chitinase activity induced by colloidal chitin in the presence or absence of glucose in S. lividans TK24 and G015 (A); in TK24(pXE4), G015(pXE4), and G015(pGA01) (B); and in TK24(pGAH01) (C). Chitinase activity was measured with 4MU-(GlcNAc)₂ for panel A and 4MU-(GlcNAc)₃ for panels B and C. At time zero, cultures grown in LB medium at 30°C for 48 h were divided into three aliquots, and the mycelia in each aliquot were suspended in YE medium (open triangles), YE medium plus 0.05% (wt/vol) colloidal chitin (open circles), or YE medium plus 0.05% (wt/vol) colloidal chitin plus 1.0% (wt/vol) glucose (solid circles).

FIG. 2

Catechol dioxygenase activity of S. lividans TK24(pEMX151) (A) and G015(pEMX151) (B). Catechol dioxygenase activity was measured 45 h after subculturing (as described in the legend to Fig. 1) from LB medium supplemented with 2 μg of thiostrepton/ml. ΔA375 indicates the increase in optical density per minute at 375 nm. N, YE medium; C, YE medium plus 0.05% (wt/vol) colloidal chitin; CG, YE medium plus 0.05% (wt/vol) colloidal chitin plus 1.0% (wt/vol) glucose.