Induction of the Stringent Response in Streptomyces Coelicolor A3(2) and Its Possible Role in Antibiotic Production

Abstract

The stringent response has been implicated as one of the triggers for antibiotic production and sporulation in Streptomyces (Ochi 1986; 1987b). We have characterised the stringent response and studied its possible role in the initiation of actinorhodin biosynthesis in the genetically well-defined strain Streptomyces coelicolor A3(2). The stringent response was elicited in exponentially growing cultures either by addition of the amino acid analogue serine hydroxamate or by nutritional shiftdown. In both cases, transient accumulations of ppGpp were observed after 10 to 15 minutes that correlated with a severe reduction in the level of transcription of a previosly cloned rRNA gene set (rrnD; Baylis and Bibb, 1986a). The influence of the stringent response on actinorhodin biosynthesis was less obvious. While transcripts of the actinorhodin cluster were observed approximately one hour after a nutritional shiftdown, no such transcripts were observed after induction of the stringent response by serine hydroxamate. These results suggest that ppGpp accumulation alone is not sufficient for the induction of antibiotic production.