Guanosine 5'-diphosphate 3'-diphosphate (ppGpp), guanosine 5'-diphosphate 3'-monophosphate (ppGp) and antibiotic production in Streptomyces clavuligerus

Abstract

Streptomyces clavuligerus was grown in nutrient-limited defined media in laboratory scale fermenters using continuous and batch culture methods. Cephamycin C was produced in all fermentations. Clavulanic acid was produced in carbon- and nitrogenlimited continuous culture and in carbon- and phosphate-limited batch culture. Low levels of intracellular guanosine 5'-diphosphate 3'-diphosphate (ppGpp) were detected at D= 0.02 h' in continuous culture in all media. Low levels of intracellular guanosine 5 '-diphosphate 3 '-monophosphate (ppGp) were detected at D=0.02 if' in carbon- and nitrogen- limited media. ppop was not detected under phosphate limitation at any dilution rate. Increased production of cephamycin C was observed at D=0.02 If' under nitrogen limitation coinciding with the detection of elevated levels of ppGpp, ppGp and
ATP. Increased production of clavulanic acid was observed at D=0.02 If' under carbon limitation coinciding with the detection of elevated levels of ppGpp and ppGp. There was no correlation between dilution rate and basal levels of either ppGpp or ppGp in any growth-limiting medium. ppGpp was produced at low levels in carbon- and nitrogen-limited batch fermentations prior to the detection of cephamycin C and clavulanic acid in the medium. High levels of ppGpp were detected under phosphate limitation immediately prior to the transcription of cas, the gene encoding clavaminate synthase. High levels of ppGp were detected in all batch fermentations following a downturn in nitrogen and carbon levels and immediately prior to the detection of isopenicillin N synthetase (IPNS). ppGp was detected following nutrient shifidown by amino acid depletion and was not produced via degradation of ppGpp. The results point to a possible role for ppGpp in the regulation of clavulanic acid synthesis under phosphate limitation only, and a potential role for ppGp in the regulation of cephamycin C production in Streptomyces clavuligerus.