PDF(Pubmed)
Abstract：
Bacterial ClpB is an ATP-dependent disaggregate that belongs to the Hsp100/Clp family and facilitates bacterial survival under hostile environmental conditions. Streptococcus agalactiae, which is regarded as the major bacterial pathogen of farmed Nile tilapia (Oreochromis niloticus), is known to cause high mortality and large economic losses. Here, we report a ClpB homologue of S. agalactiae and explore its functionality. S. agalactiae with a clpB deletion mutant (∆clpB) exhibited defective tolerance against heat and acidic stress, without affecting growth or morphology under optimal conditions. Moreover, the ΔclpB mutant exhibited reduced intracellular survival in RAW264.7 cells, diminished adherence to the brain cells of tilapia, increased sensitivity to leukocytes from the head kidney of tilapia and whole blood killing, and reduced mortality and bacterial loads in a tilapia infection assay. Furthermore, the reduced virulence of the ∆clpB mutant was investigated by transcriptome analysis, which revealed that deletion of clpB altered the expression levels of multiple genes that contribute to the stress response as well as certain metabolic pathways. Collectively, our findings demonstrated that ClpB, a molecular chaperone, plays critical roles in heat and acid stress resistance and virulence in S. agalactiae. This finding provides an enhanced understanding of the functionality of this ClpB homologue in gram-positive bacteria and the survival strategy of S. agalactiae against immune clearance during infection.
摘要：
细菌ClpB是ATP依赖性解聚物,其属于Hsp100/Clp家族并且促进细菌在恶劣环境条件下的存活。无乳链球菌，被认为是养殖尼罗罗非鱼（Oreochromisniloticus）的主要细菌病原体，已知会导致高死亡率和巨大的经济损失。这里,我们报道了无乳链球菌的ClpB同源物，并探讨了其功能。具有clpB缺失突变体（ΔclpB）的无乳链球菌对热和酸性胁迫表现出缺陷的耐受性，在最佳条件下不影响生长或形态。此外，ΔclpB突变体在RAW264.7细胞中表现出细胞内存活率降低，对罗非鱼脑细胞的粘附力减弱，对罗非鱼头肾白细胞的敏感性增加，并降低了罗非鱼感染试验中的死亡率和细菌负荷。此外，通过转录组分析研究了ΔclpB突变体的毒力降低，这表明clpB的缺失改变了多个基因的表达水平，这些基因有助于应激反应以及某些代谢途径。总的来说，我们的研究结果表明，ClpB，分子伴侣,在无乳链球菌的抗热和抗酸胁迫和毒力中起关键作用。这一发现提供了对这种ClpB同源物在革兰氏阳性细菌中的功能以及无乳链球菌在感染期间针对免疫清除的存活策略的增强理解。
