Department of Biomedical Engineering, University of California Davis, Davis, CA, USA; Department of Biological Sciences, Birla Institute of Technology and Science, Pilani, Pilani, 333031, Rajasthan, India.
Department of Biological Sciences, Birla Institute of Technology and Science, Pilani, Pilani, 333031, Rajasthan, India.
Microb Pathog. 2023 Oct;183:106268. doi: 10.1016/j.micpath.2023.106268. Epub 2023 Aug 1.
Despite the relevance of E. cloacae as an opportunistic pathogen, very little is known about its pathogenicity mechanism and the factors influencing its virulence. The mechanism of E. cloacae pathogenicity appears to be complex and multifactorial, with the presence of different putative virulence factors whose role is still not clear in the development of the disease. In this study, we systematically investigated the role of T6SS (type six secretion system) of E. cloacae SBP-8, an environmental isolate, in eukaryotic and bacterial cell interaction. Analysis of the genome sequence of E. cloacae SBP-8 revealed the presence of sets of genes coding for the expression of one complete T6SS cluster, which is similar to T6SS-1 cluster of E. cloacae ATCC 13047 (clinical isolates). In addition, an Hcp effector protein was detected in the secretome, and this secretion depended on ClpV, an Atpase of T6SS, confirming that strain SBP-8 produces functional T6SS. Deletion of T6SS-associated gene clpV did not induce any significant change in the life span and rate of colonization in C. elegans. No major significant change was observed in the expression profiling of antimicrobial genes (clec-60, clec-85, clec-87 and lys-1) and toll-like receptor (toll-1) gene, involved in stimulating an immune response against the pathogen. No difference in the ability to invade and proliferate in intestinal cells and phagocytosis by macrophages was observed. In addition, we demonstrated that the ability of E. cloacae SBP-8 to out-compete Escherichia coli was reliant upon its T6SS in contact-dependent manner. Our results show that T6SS of the environmental isolates is required for interbacterial competition but not for invasion and proliferation inside host cells.
尽管阴沟肠杆菌作为一种机会性病原体具有重要意义，但人们对其致病机制和影响其毒力的因素知之甚少。阴沟肠杆菌的致病机制似乎很复杂，具有多种假定的毒力因子，其在疾病发展中的作用尚不清楚。在这项研究中，我们系统地研究了环境分离株阴沟肠杆菌 SBP-8 的 T6SS（六型分泌系统）在真核细胞和细菌细胞相互作用中的作用。对阴沟肠杆菌 SBP-8 基因组序列的分析显示，存在一组编码表达完整 T6SS 簇的基因，该簇与阴沟肠杆菌 ATCC 13047（临床分离株）的 T6SS-1 簇相似。此外，在分泌组中检测到 Hcp 效应蛋白，这种分泌依赖于 T6SS 的 ClpV Atpase，证实了 SBP-8 株产生功能性 T6SS。T6SS 相关基因 clpV 的缺失并没有诱导秀丽隐杆线虫寿命和定植率的显著变化。参与刺激针对病原体的免疫反应的抗菌基因（clec-60、clec-85、clec-87 和 lys-1）和 Toll 样受体（toll-1）基因的表达谱没有观察到明显变化。在肠细胞中的侵袭和增殖以及巨噬细胞的吞噬作用方面没有观察到明显差异。此外，我们证明了阴沟肠杆菌 SBP-8 与大肠杆菌竞争的能力依赖于其 T6SS 的接触依赖性。我们的结果表明，环境分离株的 T6SS 是细菌间竞争所必需的，但不是入侵和增殖宿主细胞所必需的。
