Streptomyces griseus 45H, a producer of the extracellular autoregulator protein factor C, is a member of the species Streptomyces albidoflavus.

Streptomyces griseus strain 45H, isolated in 1960 during a mutagenesis programme on the industrial streptomycin producer S. griseus 52-1, encodes an extracellular, pleiotropic autoregulatory signalling protein, factor C, which stimulates sporulation of S. griseus 52-1 in submerged culture. The facC gene, which codes for factor C, is present in very few streptomycetes and is not present in S. griseus 52-1. Based on 16S rRNA gene sequencing and other molecular data, S. griseus 45H, the factor C producer, is here shown to be related to the original laboratory strain of Streptomyces flavofungini, which was being studied in the same laboratory in 1960, and to Streptomyces albidoflavus. Southern blotting revealed that three out of four independently isolated strains of S. albidoflavus possess facC. Both the original strain of S. flavofungini and S. griseus 45H are therefore identified as members of the species Streptomyces albidoflavus, and we propose that S. griseus 45H should be renamed Streptomyces albidoflavus 45H.