Abstract:Prodigiosin(PG), a secondary metabolite produced by Serratia marcescens, has attracted attention owing to its anti-microbial, anti-malaria, anti-tumor and immunosuppressive activities. However, there is still limited understanding of the regulatory mechanism for prodigiosin biosynthesis in S. marcescens. In this study, a Tn5G transposon insertion mutant library using the strain S. marcescens JNB5-1 as the parental strain was constructed, and BVG90_04085(PsrB), a DeoR family transcription regulator, was identified and elucidated to positively regulate prodigiosin production in strain JNB5-1. Further, the molecular mechanism behind PsrB in regulating prodigiosin production in this strain was investigated. Results showed that when fermentation was done in LB medium, the prodigiosin productivity of psrB mutants SK8-61 and ΔPsrB was only 0.22 and 0.26 times as high as that of the parental strain JNB5-1. The expression level of pig gene cluster analyzed by RT-qPCR showed that the psrB deletion mutant ΔPsrB comparing with the parental strain JNB5-1, and the expression level of a key gene in the prodigiosin pathway, pigABCDEFGHIJKLMN, was down-regulated by 5.81 to 22.93 times. Further, electrophoretic mobility shift assay (EMSA) and other experiments confirmed that regulator PsrB could directly bind to the promoter region of the pig gene cluster, suggesting that the molecular mechanism by which PsrB regulated prodigiosin production in S.marcescens was probably through direct binding to the pig gene cluster, and thus positively regulated the transcriptional level of pig gene cluster, affecting the synthesis of prodigiosin in S. marcescens. Finally, the psrB overexpressed strain JNB5-1/pXW1906 found during prodigiosin fermented in the fermentation medium could synthesize 8.61 g/L prodigiosin, which was 1.56 times of that produced by the parental strain JNB5-1 (5.53 g/L).
