Department of Innovation Systems Engineering, Graduate School of Engineering, Utsunomiya University, Japan.
Center for Bioscience Research and Education, Utsunomiya University, Japan.
Genome Biol Evol. 2019 Mar 1;11(3):931-936. doi: 10.1093/gbe/evz046.
Quorum sensing is a cell density-dependent regulation of gene expression. N-acyl-l-homoserine lactone (AHL) is a major quorum-sensing signaling molecule in gram-negative bacteria and synthesized by the LuxI family protein. The genus Serratia is known as a producer of the red pigment, prodigiosin, whose biosynthesis is dependent on the pig gene cluster. Some Serratia strains regulate prodigiosin production via AHL-mediated quorum sensing, whereas there is red-pigmented Serratia strains without quorum-sensing system. In addition, nonpigmented Serratia marcescens, which does not produce prodigiosin, has also been isolated from natural and clinical environments. In this study, we aim to reveal the distribution and genetic diversity of quorum-sensing genes and pig gene cluster in the complete genome sequences of S. marcescens. We previously demonstrated that S. marcescens AS-1 regulates the production of prodigiosin via AHL-mediated quorum sensing. We sequenced the genomes of AS-1 and compared with the complete genomes of AS-1 and the other 34 strains of S. marcescens. The luxI homolog was present on 25 complete genome sequences. The deduced amino acid sequences of the luxI homolog were divided into three phylogenetic classes. In contrast, the pig gene cluster was present in the genome of seven S. marcescens strains and only two strains, AS-1 and N4-5 contained both the luxI homolog and pig gene cluster in their genome. It is therefore assumed that prodigiosin production and its regulation by quorum sensing are not essential for the life cycle of S. marcescens.
群体感应是一种依赖于细胞密度的基因表达调控方式。N-酰基高丝氨酸内酯（AHL）是革兰氏阴性菌中主要的群体感应信号分子，由 LuxI 家族蛋白合成。沙雷氏菌属以产生红色色素灵菌红素而闻名，其生物合成依赖于 pig 基因簇。一些沙雷氏菌菌株通过 AHL 介导的群体感应来调节灵菌红素的产生，而有些红色沙雷氏菌菌株则没有群体感应系统。此外，从自然和临床环境中也分离到了不产生灵菌红素的非色素沙雷氏菌 marcescens。在本研究中，我们旨在揭示群体感应基因和 pig 基因簇在完整沙雷氏菌 marcescens 基因组序列中的分布和遗传多样性。我们之前已经证明，沙雷氏菌 marcescens AS-1 通过 AHL 介导的群体感应来调节灵菌红素的产生。我们对 AS-1 的基因组进行了测序，并与 AS-1 和其他 34 株沙雷氏菌 marcescens 的完整基因组进行了比较。25 个完整基因组序列中都存在 luxI 同源物。luxI 同源物的推导氨基酸序列分为三个系统发育类群。相比之下，pig 基因簇存在于 7 株沙雷氏菌 marcescens 菌株的基因组中，只有 2 株菌株 AS-1 和 N4-5 在其基因组中同时含有 luxI 同源物和 pig 基因簇。因此，可以假设灵菌红素的产生及其通过群体感应的调节对沙雷氏菌 marcescens 的生命周期并非必不可少。
