TRANSCRIPTIONAL REGULATION OF STREPTOMYCES-COELICOLOR PATHWAY-SPECIFIC ANTIBIOTIC REGULATORS BY THE ABSA AND ABSB LOCI

The four antibiotics produced by Streptomyces coelicolor are all affec ted by mutations in the absA and absB loci. The absA locus encodes a p utative two-component signal transduction system, and the absB locus e ncodes a homolog of Escherichia coli RNase TH, We assessed whether the se loci control synthesis of the antibiotics actinorhodin and unadecyl prodigiosin by regulating transcript abundance from the biosynthetic a nd regulatory genes specific for each antibiotic, Strains that were Ab s(-)(for antibiotic synthesis deficient) due to mutations in absA or a bsB were examined. In the Abs(-) absA mutant strain, transcripts for t he actinorhodin biosynthetic genes actVI-ORF1 and actI, and for the pa thway-specific regulatory gene actII-ORF4, were substantially lower in abundance than in the parent strain. The level of the transcript for the undecylprodigiosin pathway-specific regulatory gene redD was simil arly reduced in this mutant. additionally, a strain that exhibits prec ocious hyperproduction of antibiotics (Pha phenotype) due to disruptio n of the absA locus contained elevated levels of the actVI-ORF1, actII -ORF4, and redD transcripts. In the absB mutant strain, actVI-ORF1, ac tI, actII-ORF4, and redD transcript levels were also substantially low er than in the parent strain, These results establish that the abs gen es affect production of antibiotics through regulation of expression o f the antibiotic-specific regulatory genes in S. coelicolor.