Abstract
A mutant of Streptomyces griseus, NY5, differs from the parent in sporulating when grown in a nutrient rich growth medium. Cloned genes of the wildtype organism in the multicopy plasmid pIJ702 transformed into the NY5 mutant cells resulted in converting the mutant phenotype of sporulating in rich medium to the parental genotype of not sporulating in rich medium. A 1.5 kb DNA fragment was sequenced and found to contain two open reading frame gene regions. Restriction deletion mapping and subcloning revealed a gene which when transformed in high copy number into S. griseus wildtype, mutant NY5 and S. lividans resulted in suppression of sporulation and fragmented cell growth. The gene, named ssgA (DDJB/EMBL/GenBank accession no. is D50051), encodes a 145 amino acid protein with a calculated size of 15.8 kDa. The predicted protein has a strong negative charge and shows no significant sequence homology to known proteins. Southern analysis detected regions in S. coelicolor and S. lividans DNA homologous to ssgA.
