Regulation of maltocin synthesis in Stenotrophomonas maltophilia by positive and negative regulators

Abstract

Maltocin P28, produced by Stenotrophomonas maltophilia P28, is an R-type phage tail-like bacteriocin (PTLB). Its gene cluster consists of 23 putative genes, including nine nonstructural genes and fourteen structural genes. In this work, three nonstructural genes, mpsA, mpsH and mpsR, were found to encode transcriptional regulators to control maltocin P28 synthesis. MpsA activated the transcription of mpsH and lysis genes. MpsH activated the transcription of structural genes. Under normal growth conditions, MpsR repressed the transcription of mpsA and the structural genes, as well as its own. When S. maltophilia P28 was treated with mitomycin C, an immediate and significant decrease in the amount of MpsR was observed, followed by derepressed expression of mpsA, mpsR and structural genes, a marked rise in the expression of all regulatory and structural genes, and finally a clear increase in the maltocin P28 production. Neither the recA gene nor the lexA gene was found to be involved in the induced synthesis of maltocin P28. Our study indicated that a unique mechanism regulates the expression of maltocin genes in S. maltophilia, representing a novel strategy for balancing the expression of PTLB genes in bacteria.