Kalburge Sai Siddarth, Carpenter Megan R, Rozovsky Sharon, Boyd E Fidelma
Department of Biological Sciences, University of Delaware, Newark, Delaware, USA.
Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware, USA.
Infect Immun. 2017 Feb 23;85(3). doi: 10.1128/IAI.00930-16. Print 2017 Mar.
Quorum sensing (QS) is a process by which bacteria alter gene expression in response to cell density changes. In species, at low cell density, the sigma 54-dependent response regulator LuxO is active and regulates the two QS master regulators AphA, which is induced, and OpaR, which is repressed. At high cell density the opposite occurs: LuxO is inactive, and therefore OpaR is induced while AphA is repressed. In , a significant enteric pathogen of humans, the roles of these regulators in pathogenesis are less known. We examined deletion mutants of , , and for fitness using an adult mouse model. We found that the and mutants were defective in colonization compared to levels in the wild type. The mutant did not show any defect Colonization was restored to wild-type levels in a double mutant and was also increased in an double mutant. These data suggest that AphA is important and that overexpression of is detrimental to fitness. Transcriptome sequencing (RNA-Seq) analysis of the wild type and mutant grown in mouse intestinal mucus showed that 60% of the genes that were downregulated in the mutant were involved in amino acid and sugar transport and metabolism. These data suggest that the mutant has a metabolic disadvantage, which was confirmed by growth pattern analysis using phenotype microarrays. Bioinformatics analysis revealed OpaR binding sites in the regulatory region of 55 carbon transporter and metabolism genes. Biochemical analysis of five representatives of these regulatory regions demonstrated direct binding of OpaR in all five tested. These data demonstrate the role of OpaR in carbon utilization and metabolic fitness, an overlooked role in the QS regulon.
群体感应（QS）是细菌根据细胞密度变化改变基因表达的过程。在某些物种中，细胞密度较低时，依赖σ54的应答调节因子LuxO处于活跃状态，调控两个群体感应主调节因子，即被诱导的AphA和被抑制的OpaR。在细胞密度较高时则相反：LuxO不活跃，因此OpaR被诱导而AphA被抑制。在人类重要的肠道病原体[具体物种未提及]中，这些调节因子在发病机制中的作用鲜为人知。我们使用成年小鼠模型检测了[具体基因未提及]、[具体基因未提及]和[具体基因未提及]的缺失突变体的适应性。我们发现，与野生型水平相比，[具体基因未提及]和[具体基因未提及]突变体在定殖方面存在缺陷。[具体基因未提及]突变体未表现出任何缺陷。在[具体基因未提及]双突变体中，定殖恢复到野生型水平，在[具体基因未提及]双突变体中定殖也有所增加。这些数据表明AphA很重要，并且[具体基因未提及]的过表达对[具体物种未提及]的适应性有害。对在小鼠肠道黏液中生长的野生型和[具体基因未提及]突变体进行转录组测序（RNA-Seq）分析表明，在[具体基因未提及]突变体中下调的基因有60%参与氨基酸和糖的运输与代谢。这些数据表明[具体基因未提及]突变体具有代谢劣势，这通过使用表型微阵列的生长模式分析得到了证实。生物信息学分析揭示了55个碳转运和代谢基因的调控区域中存在OpaR结合位点。对这些调控区域的五个代表进行生化分析表明，在所有五个测试中OpaR都能直接结合。这些数据证明了OpaR在碳利用和代谢适应性方面的作用，这在群体感应调控子中是一个被忽视的作用。
