Heterologous Expression and Temperature Regulation of Prodigiosin-synthesis Gene Cluster in Serratia marcecens

  Objective   Strains of Serratia marcescens FZSF02 that had heterologous expression and could produce prodigiosin with relevant synthesis gene cluster were constructed to study the mechanism relating to temperature regulation in the biological process.

  Methods   Three Escherichia coli strains with heterologous expression carrying different promoters were constructed. Real-time fluorescent quantitative PCR (RT-qPCR) was used to determine the transcriptional differences of pigA, pigF and pigN in the pig gene cluster at 37 ℃ and 28 ℃.

  Results   At 28 ℃, all 3 promoters initiated the expression of the pig gene cluster in E. coli, and prodigiosin was produced in the 3 recombinant strains. In contrast, only the recombinant strain carrying the strong T7 promoter delivered a small amount of the pigment after IPTG induction at 37 ℃. The RT-qPCR results showed the transcription levels of the above genes in S. marcescens FZSF02 were down-regulated at 37 ℃ in comparison to 28 ℃.

  Conclusion   The reason why S. marcescens FZSF02 was able to produce prodigiosin at 28 ℃ but failed at 37 ℃ might be, at higher temperatures, that the pig gene cluster was down-regulated and/or that the activities of one or several key enzymes encoded by the pig genes for the biosynthesis of precursors MBC and MAP were somehow inhibited.