Norwegian Structural Biology Centre, UiT - The Arctic University of Norway, N-9037, Tromsø, Norway.
Centre for Bioinformatics, Department of Chemistry, Faculty of Science and Technology, UiT - The Arctic University of Norway, N-9037, Tromsø, Norway.
BMC Genomics. 2019 Mar 15;20(1):220. doi: 10.1186/s12864-019-5594-4.
The coordination of group behaviors in bacteria is achieved by a cell-cell signaling process called quorum sensing (QS). QS is an intercellular communication system, which synchronously controls expression of a vast range of genes in response to changes in cell density and is mediated by autoinducers that act as extracellular signals. Aliivibrio salmonicida, the causative agent of cold-water vibrosis in marine aquacultures, uses QS to regulate several activities such as motility, biofilm formation, adhesion and rugose colony morphology. However, little is known about either genes or detailed mechanisms involved in the regulation of these phenotypes.
Differential expression profiling allowed us to define the genes involved in controlling phenotypes related to QS in A. salmonicida LFI1238. RNA sequencing data revealed that the number of expressed genes in A. salmonicida, ΔlitR and ΔrpoQ mutants were significantly altered due to changes in cell density. These included genes that were distributed among the 21 functional groups, mainly presented in cell envelope, cell processes, extrachromosomal/foreign DNA and transport-binding proteins functional groups. The comparative transcriptome of A. salmonicida wild-type at high cell density relative to low cell density revealed 1013 genes to be either up- or downregulated. Thirty-six downregulated genes were gene clusters encoding biosynthesis of the flagellar and chemotaxis genes. Additionally we identified significant expression for genes involved in acyl homoserine lactone (AHL) synthesis, adhesion and early colonization. The transcriptome profile of ΔrpoQ compared to the wild-type revealed 384 differensially expressed genes (DEGs) that allowed us to assign genes involved in regulating motility, adhesion and colony rugosity. Indicating the importance of RpoQ in controlling several QS related activities. Furthermore, the comparison of the transcriptome profiles of ΔlitR and ΔrpoQ mutants, exposed numerous overlapping DEGs that were essential for motility, exopolysaccharide production via syp operon and genes associated with tad operon.
Our findings indicate previously unexplained functional roles for LitR and RpoQ in regulation of different phenotypes related to QS. Our transcriptome data provide a better understanding of the regulation cascade of motility, wrinkling colony morphology and biofilm formation and will offer a major source for further research and analysis on this important field.
细菌群体行为的协调是通过一种称为群体感应（QS）的细胞间信号转导过程来实现的。QS 是一种细胞间通讯系统，它通过自动诱导物作为细胞外信号，根据细胞密度的变化同步控制广泛的基因表达。冷水性粘质沙雷氏菌是海洋水产养殖冷水性粘质病的病原体，它利用 QS 来调节运动性、生物膜形成、粘附和粗糙菌落形态等多种活性。然而，对于调节这些表型的基因或详细机制知之甚少。
差异表达谱分析使我们能够确定与 A. salmonicida LFI1238 中 QS 相关的表型控制相关的基因。RNA 测序数据显示，由于细胞密度的变化，A. salmonicida、ΔlitR 和 ΔrpoQ 突变体中表达基因的数量发生了显著改变。这些基因分布在 21 个功能组中，主要存在于细胞包膜、细胞过程、染色体外/外源 DNA 和运输结合蛋白功能组中。与低细胞密度相比，高细胞密度下 A. salmonicida 野生型的比较转录组显示 1013 个基因上调或下调。36 个下调基因是编码鞭毛和趋化性基因生物合成的基因簇。此外，我们还鉴定了与酰基高丝氨酸内酯（AHL）合成、粘附和早期定植相关的基因的显著表达。与野生型相比，ΔrpoQ 的转录组谱显示有 384 个差异表达基因（DEGs），这使我们能够分配参与调节运动性、粘附和菌落粗糙度的基因。表明 RpoQ 在调节与 QS 相关的几种活性方面的重要性。此外，ΔlitR 和 ΔrpoQ 突变体转录组谱的比较暴露了许多重叠的 DEGs，这些基因对于运动性、通过 syp 操纵子产生胞外多糖和与 tad 操纵子相关的基因至关重要。
我们的研究结果表明，LitR 和 RpoQ 在调节与 QS 相关的不同表型方面具有先前未被解释的功能作用。我们的转录组数据提供了对运动性、皱缩菌落形态和生物膜形成的调节级联的更好理解，并将为这一重要领域的进一步研究和分析提供主要来源。
