McMeechan Alisdair, Lovell Margaret A, Cogan Tristan A, Marston Kerrie L, Humphrey Tom J, Barrow Paul A
Division of Veterinary Pathology, Infection and Immunity, School of Clinical Veterinary Science, University of Bristol, Langford, Bristol BS40 5DU, UK.
Res Microbiol. 2007 Jan-Feb;158(1):79-85. doi: 10.1016/j.resmic.2006.10.008. Epub 2006 Dec 19.
Polyphosphate is involved in resistance to stress in a number of bacterial species; however, its role in the virulence of Salmonella enterica serovars which differ in their host range has not been described. We examined the role of polyphosphate kinase in infection, growth and survival of S. Typhimurium (broad-host range) and S. Gallinarum (avian-adapted). We also used ppk mutants to assess the downstream effects on intracellular ATP levels. ppk mutants had significantly (P<0.05) elevated ATP in stationary phase compared to the wild-type and, depending on the serovar, were defective in growth, survival and virulence. The virulence of S. Typhimurium ppk::SpcStr was significantly (P<0.05) attenuated following oral infection of both Rhode Island Red chickens and BALB/c mice. In contrast, inactivation of the ppk gene of S. Gallinarum did not affect growth or virulence. The differential contribution of polyphosphate to the virulence of S. Typhimurium and S. Gallinarum may reflect aspects of the pathogenesis and host range of these serovars. The ppk mutant of both serovars survived significantly less well (P<0.05) in a saline starvation-survival model, relative to the respective parent. The effect of ppk mutation on survival was formally described by fitting the data to the Weibull model and by estimation of k(max). Measurement of rpoS promoter activity using a lacZ transcriptional fusion demonstrated repression of rpoS in a ppk background, confirming a role for polyphosphate in RpoS induction. Together the data indicate the crucial importance of maintaining stable intracellular ATP during infection and nutritional stress. We suggest that polyphosphate plays a central role in homeostasis during growth and stress.
多聚磷酸盐在许多细菌物种的应激抗性中发挥作用；然而，其在宿主范围不同的肠炎沙门氏菌血清型毒力中的作用尚未见报道。我们研究了多聚磷酸盐激酶在鼠伤寒沙门氏菌（宿主范围广）和鸡沙门氏菌（适应禽类）感染、生长和存活中的作用。我们还使用ppk突变体评估其对细胞内ATP水平的下游影响。与野生型相比，ppk突变体在稳定期的ATP水平显著升高（P<0.05），并且根据血清型不同，在生长、存活和毒力方面存在缺陷。鼠伤寒沙门氏菌ppk::SpcStr在口服感染罗德岛红鸡和BALB/c小鼠后，其毒力显著减弱（P<0.05）。相比之下，鸡沙门氏菌ppk基因的失活并不影响其生长或毒力。多聚磷酸盐对鼠伤寒沙门氏菌和鸡沙门氏菌毒力的不同贡献可能反映了这些血清型的发病机制和宿主范围。相对于各自的亲本，两种血清型的ppk突变体在盐水饥饿存活模型中的存活能力显著降低（P<0.05）。通过将数据拟合到威布尔模型并估计k(max)，正式描述了ppk突变对存活的影响。使用lacZ转录融合测量rpoS启动子活性表明，在ppk背景下rpoS受到抑制，证实了多聚磷酸盐在RpoS诱导中的作用。这些数据共同表明，在感染和营养应激期间维持稳定的细胞内ATP至关重要。我们认为，多聚磷酸盐在生长和应激期间的体内平衡中起着核心作用。
