Candon Heather L, Allan Brenda J, Fraley Cresson D, Gaynor Erin C
University of British Columbia, Department of Microbiology and Immunology, Vancouver, British Columbia, Canada.
J Bacteriol. 2007 Nov;189(22):8099-108. doi: 10.1128/JB.01037-07. Epub 2007 Sep 7.
Campylobacter jejuni is the leading cause of bacterial gastroenteritis in the developed world. Despite its prevalence, relatively little is known about C. jejuni's precise pathogenesis mechanisms, particularly in comparison to other well-studied enteric organisms such as Escherichia coli and Salmonella spp. Altered expression of phosphate genes in a C. jejuni stringent response mutant, together with known correlations between the stringent response, polyphosphate (poly-P), and virulence in other bacteria, led us to investigate the role of poly-P in C. jejuni stress survival and pathogenesis. All sequenced C. jejuni strains harbor a conserved putative polyphosphate kinase 1 predicted to be principally responsible for poly-P synthesis. We generated a targeted ppk1 deletion mutant (Deltappk1) in C. jejuni strain 81-176 and found that Deltappk1, as well as the DeltaspoT stringent response mutant, exhibited low levels of poly-P at all growth stages. In contrast, wild-type C. jejuni poly-P levels increased significantly as the bacteria transitioned from log to stationary phase. Phenotypic analyses revealed that the Deltappk1 mutant was defective for survival during osmotic shock and low-nutrient stress. However, certain phenotypes associated with ppk1 deletion in other bacteria (i.e., motility and oxidative stress) were unaffected in the C. jejuni Deltappk1 mutant, which also displayed an unexpected increase in biofilm formation. The C. jejuni Deltappk1 mutant was also defective for the virulence-associated phenotype of intraepithelial cell survival in a tissue culture infection model and exhibited a striking, dose-dependent chick colonization defect. These results indicate that poly-P utilization and accumulation contribute significantly to C. jejuni pathogenesis and affect its ability to adapt to specific stresses and stringencies. Furthermore, our study demonstrates that poly-P likely plays both similar and unique roles in C. jejuni compared to its roles in other bacteria and that poly-P metabolism is linked to stringent response mechanisms in C. jejuni.
空肠弯曲菌是发达国家细菌性肠胃炎的主要病因。尽管其普遍存在，但人们对空肠弯曲菌的确切致病机制了解相对较少，特别是与其他经过充分研究的肠道微生物（如大肠杆菌和沙门氏菌属）相比。空肠弯曲菌严格反应突变体中磷酸盐基因表达的改变，以及其他细菌中严格反应、多聚磷酸盐（poly-P）与毒力之间已知的相关性，促使我们研究多聚磷酸盐在空肠弯曲菌应激存活和致病过程中的作用。所有已测序的空肠弯曲菌菌株都含有一个保守的假定多聚磷酸盐激酶1，预计它主要负责多聚磷酸盐的合成。我们在空肠弯曲菌菌株81-176中构建了一个靶向ppk1缺失突变体（Deltappk1），发现Deltappk1以及DeltaspoT严格反应突变体在所有生长阶段的多聚磷酸盐水平都很低。相比之下，野生型空肠弯曲菌的多聚磷酸盐水平在细菌从对数期过渡到稳定期时显著增加。表型分析表明，Deltappk1突变体在渗透休克和低营养应激期间的存活存在缺陷。然而，其他细菌中与ppk1缺失相关的某些表型（即运动性和氧化应激）在空肠弯曲菌Deltappk1突变体中未受影响，该突变体的生物膜形成还意外增加。在组织培养感染模型中，空肠弯曲菌Deltappk1突变体在与毒力相关的上皮内细胞存活表型方面也存在缺陷，并且在雏鸡定殖中表现出显著的、剂量依赖性的缺陷。这些结果表明，多聚磷酸盐的利用和积累对空肠弯曲菌的致病过程有显著贡献，并影响其适应特定应激和严格条件的能力。此外，我们的研究表明，与在其他细菌中的作用相比，多聚磷酸盐在空肠弯曲菌中可能发挥着相似和独特的作用，并且多聚磷酸盐代谢与空肠弯曲菌的严格反应机制相关联。
