Culham Doreen E, Lu Annie, Jishage Miki, Krogfelt Karen A, Ishihama Akira, Wood Janet M
Department of Microbiology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada1.
Department of Gastrointestinal Infections, Statens Serum Institut, DK2300 Copenhagen, Denmark3.
Microbiology (Reading). 2001 Jun;147(Pt 6):1657-1670. doi: 10.1099/00221287-147-6-1657.
Trehalose synthesis (RpoS-dependent) and betaine uptake mediated by transporters ProP and ProU contribute to the osmotolerance of Escherichia coli K-12. Pyelonephritis isolates CFT073 and HU734 were similar and diminished in osmotolerance, respectively, compared to E. coli K-12. The roles of RpoS, ProP and ProU in osmoregulation and urovirulence were assessed for these isolates. Strain HU734 expressed an RpoS variant which had low activity and a C-terminal extension. This bacterium accumulated very little trehalose and had poor stationary-phase thermotolerance. For E. coli CFT073, introduction of an rpoS deletion impaired trehalose accumulation, osmotolerance and stationary-phase thermotolerance. The rpoS defects accounted for the difference in osmotolerance between these strains in minimal medium of very high osmolality (1.4 mol kg(-1)) but not in medium of lower osmolality (0.4 mol kg(-1)). The slow growth of both pyelonephritis isolates in high-osmolality medium was stimulated by glycine betaine (GB) and deletion of proP and/or proU impaired GB uptake. An HU734 derivative lacking both proP and proU retained osmoprotective GB uptake activity that could be attributed to system BetU, which is not present in strain K-12 or CFT073. BetU transported GB (K(m), 22 microM) and proline betaine. High-osmolality human urine (0.92 mol kg(-1)) included membrane-permeant osmolyte urea (0.44 M) plus other constituents which contributed an osmolality of only approximately 0.4 mol kg(-1). Strains HU734 and CFT073 showed correspondingly low GB uptake activities after cultivation in this urine. Deletion of proP and proU slowed the growth of E. coli HU734 in this high-osmolality human urine (which contains betaines) but had little impact on its colonization of the murine urinary tract after transurethral inoculation. By contrast, deletion of rpoS, proP and proU had no effect on the very rapid growth of CFT073 in high-osmolality urine or on its experimental colonization of the murine urinary tract. RpoS-dependent gene expression is not essential for growth in human urine or colonization of the murine urinary tract. Additional osmoregulatory systems, some not present in E. coli K-12 (e.g. BetU), may facilitate growth of pyelonephritis isolates in human urine and colonization of mammalian urinary tracts. The contributions of systems ProP and ProU to urinary tract colonization cannot be definitively assessed until all such systems are identified.
海藻糖合成（依赖RpoS）以及由转运蛋白ProP和ProU介导的甜菜碱摄取有助于大肠杆菌K - 12的渗透压耐受性。与大肠杆菌K - 12相比，肾盂肾炎分离株CFT073和HU734的渗透压耐受性分别有所不同且有所降低。对这些分离株评估了RpoS、ProP和ProU在渗透调节和尿路致病性中的作用。菌株HU734表达一种具有低活性和C末端延伸的RpoS变体。这种细菌积累的海藻糖很少，并且在稳定期的耐热性较差。对于大肠杆菌CFT073，引入rpoS缺失会损害海藻糖积累、渗透压耐受性和稳定期耐热性。rpoS缺陷解释了这些菌株在极高渗透压（1.4 mol kg⁻¹）的基本培养基中渗透压耐受性的差异，但在较低渗透压（0.4 mol kg⁻¹）的培养基中则不然。甘氨酸甜菜碱（GB）刺激了两种肾盂肾炎分离株在高渗培养基中的缓慢生长，并且proP和/或proU的缺失会损害GB摄取。一种同时缺失proP和proU的HU734衍生物保留了可归因于BetU系统的渗透保护GB摄取活性，该系统在菌株K - 12或CFT073中不存在。BetU转运GB（Km，22 μM）和脯氨酸甜菜碱。高渗人尿（0.92 mol kg⁻¹）包含可透过膜的渗透剂尿素（0.44 M）以及其他仅贡献约0.4 mol kg⁻¹渗透压的成分。在这种尿液中培养后，菌株HU734和CFT073相应地表现出较低的GB摄取活性。proP和proU的缺失减缓了大肠杆菌HU734在这种高渗人尿（含有甜菜碱）中的生长，但对其经尿道接种后在小鼠尿路中的定殖影响很小。相比之下，rpoS、proP和proU的缺失对CFT073在高渗尿液中的快速生长或其在小鼠尿路中的实验性定殖没有影响。依赖RpoS的基因表达对于在人尿中生长或在小鼠尿路中定殖不是必需的。其他渗透调节系统，一些在大肠杆菌K - 12中不存在（例如BetU），可能有助于肾盂肾炎分离株在人尿中生长以及在哺乳动物尿路中定殖。在所有此类系统被鉴定出来之前，无法明确评估ProP和ProU系统对尿路定殖的贡献。
