sigma(32) regulation of the algA and pnrB expression in Pseudomonas sp HK-6 which degrades the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)

Abstract

Pseudomonas sp. HK-6 cells can utilize hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) as a carbon and nitrogen source. HK-6 cells grown in media containing RDX express several genes encoding stress shock proteins (SSPs) and enzymes that function in RDX degradation. The rpoH gene (sigma(32), a stress response sigma factor), alg operon (clustered genes for alginate synthesis) and pnrB gene (RDX nitroreductase) are included among these expressed genes. To examine whether the transcription of the algA and pnrB genes are controlled by sigma(32), their mRNA levels in rpoH knock-out cells grown under stress conditions were measured by quantitative real-time polymerase chain reaction (RT-qPCR) and compared with the levels in wild-type HK-6 cells. Expression of algA mRNA was approximately 4-7-fold lower in the rpoH knock-out cells than in the wild-type cells. Transcription levels of the pnrB gene were approximately 3-fold lower in the rpoH mutant. These results indicate that sigma(32) production by various environmental stressors, including RDX, is required for the induction of genes encoding SSPs and enzymes for RDX degradation.