Department of Microbiology and Molecular Genetics and The Vermont Lung Center, University of Vermont College of Medicine, Burlington, Vermont, United States of America.
PLoS One. 2013;8(2):e56850. doi: 10.1371/journal.pone.0056850. Epub 2013 Feb 14.
Pseudomonas aeruginosa can acquire and metabolize a variety of molecules including choline, an abundant host-derived molecule. In P. aeruginosa, choline is oxidized to glycine betaine which can be used as an osmoprotectant, a sole source of carbon and nitrogen, and as an inducer of the virulence factor, hemolytic phospholipase C (PlcH) via the transcriptional regulator GbdR. The primary objective was to determine the contribution of choline conversion to glycine betaine to P. aeruginosa survival during mouse lung infection. A secondary objective was to gain insight into the relative contributions of the different roles of glycine betaine to P. aeruginosa survival during infection. Using a model of acute murine pneumonia, we determined that deletion of the choline oxidase system (encoded by betBA) decreased P. aeruginosa survival in the mouse lung. Deletion of the glycine betaine demethylase genes (gbcA-B), required for glycine betaine catabolism, did not impact P. aeruginosa survival in the lung. Thus, the defect of the betBA mutant was not due to a requirement for glycine betaine catabolism or dependence on a downstream metabolite. Deletion of betBA decreased the abundance of plcH transcript during infection, which suggested a role for PlcH in the betBA survival defect. To test the contribution of plcH to the betBA mutant phenotype a betBAplcHR double deletion mutant was generated. The betBA and betBAplcHR double mutant had a small but significant survival defect compared to the plcHR single mutant, suggesting that regulation of plcH expression is not the only role for glycine betaine during infection. The conclusion was that choline acquisition and its oxidation to glycine betaine contribute to P. aeruginosa survival in the mouse lung. While defective plcH induction can explain a portion of the betBA mutant phenotype, the exact mechanisms driving the betBA mutant survival defect remain unknown.
铜绿假单胞菌可以获取和代谢多种分子，包括胆碱，一种丰富的宿主来源分子。在铜绿假单胞菌中，胆碱被氧化为甘氨酸甜菜碱，甘氨酸甜菜碱可用作渗透保护剂、唯一的碳源和氮源，以及通过转录调节剂 GbdR 诱导溶血磷脂酶 C (PlcH) 等毒力因子。主要目的是确定胆碱转化为甘氨酸甜菜碱对铜绿假单胞菌在小鼠肺部感染期间存活的贡献。次要目标是深入了解甘氨酸甜菜碱在感染期间对铜绿假单胞菌存活的不同作用的相对贡献。通过急性小鼠肺炎模型，我们确定胆碱氧化酶系统（由 betBA 编码）的缺失降低了铜绿假单胞菌在小鼠肺部的存活。甘氨酸甜菜碱脱甲基酶基因（gbcA-B）的缺失，甘氨酸甜菜碱分解代谢所必需的，对铜绿假单胞菌在肺部的存活没有影响。因此，betBA 突变体的缺陷不是由于甘氨酸甜菜碱分解代谢的要求或对下游代谢物的依赖。betBA 的缺失减少了感染期间 plcH 转录物的丰度，这表明 PlcH 在 betBA 存活缺陷中起作用。为了测试 plcH 对 betBA 突变表型的贡献，生成了 betBAplcHR 双缺失突变体。与 plcHR 单突变体相比，betBA 和 betBAplcHR 双突变体的存活缺陷较小但有统计学意义，这表明 PlcH 表达的调节不是感染期间甘氨酸甜菜碱的唯一作用。结论是，铜绿假单胞菌获取胆碱并将其氧化为甘氨酸甜菜碱有助于其在小鼠肺部的存活。虽然缺陷的 plcH 诱导可以解释部分 betBA 突变体表型，但驱动 betBA 突变体存活缺陷的确切机制仍不清楚。
