RpoS, an alternative sigma factor of RNA polymerase, regulates the expression of a great deal of genes involved in stationary-phase survival and stress response. To identify the function of RpoS homologue in Serratia marcescens FS14, in-frame deletion mutant of rpoS was constructed. It was found that RpoS activates the biosynthesis of prodigiosin in FS14 which is just opposite to what was observed in Serratia sp. ATCC 39006. We also demonstrated that RpoS positively regulates the prodigiosin production by activating the transcription of pig cluster in FS14, and the transcription of pig cluster is RpoS-dependent. Further study showed that the differences in the promoters of pig clusters in FS14 and 39006 lead to the different selection of the sigma factors and result in the different regulation mechanisms. The -10 element and the spacer region between -10 and -35 elements of the pig cluster in FS14 are vital for the RpoS recognition in FS14.

RpoS 是 RNA 聚合酶的另一种 sigma 因子，它调节大量参与静止期生存和应激反应的基因的表达。为了鉴定粘质沙雷氏菌FS14中RpoS同源物的功能，构建了rpoS的框内缺失突变体。发现 RpoS 激活了 FS14 中灵菌红素的生物合成，这与在沙雷氏菌中观察到的正好相反。ATCC 39006。我们还证明了 RpoS 通过激活FS14中猪簇的转录正调节灵菌红素的产生，并且猪簇的转录是 RpoS 依赖性的。进一步研究表明，猪的启动子存在差异FS14 和 39006 中的簇导致 sigma 因子的选择不同，从而导致调节机制不同。FS14 中猪簇的 -10 元素和 -10 和 -35 元素之间的间隔区对于 FS14 中的 RpoS 识别至关重要。