GlnR positive transcriptional regulation of the phosphate-specific transport system pstSCAB in Amycolatopsis mediterranei U32.

Amycolatopsis mediterranei U32 is an important industrial strain for the production of rifamycin SV. Rifampicin, a derivative of rifamycin SV, is commonly used to treat mycobacterial infections. Although phosphate has long been known to affect rifamycin biosynthesis, phosphate transport, metabolism, and regulation are poorly understood in A. mediterranei. In this study, the functional phosphate transport system pstSCAB was isolated by RNA sequencing and inactivated by insertion mutation in A. mediterranei U32. The mycelium morphology changed from a filamentous shape in the wild-type and pstS1+ strains to irregular swollen shape at the end of filamentous in the ΔpstS1 strain. RT-PCR assay revealed that pstSCAB genes are co-transcribed as a polycistronic messenger. The pstSCAB transcription was significantly activated by nitrate supplementation and positively regulated by GlnR which is a global regulator of nitrogen metabolism in actinomycetes. At the same time, the yield of rifamycin SV decreased after mutation (ΔpstS1) compared with wild-type U32, which indicated a strong connection among phosphate metabolism, nitrogen metabolism, and rifamycin production in actinomycetes.