Lichtenegger Sabine, Bina Isabelle, Roier Sandro, Bauernfeind Stilla, Keidel Kristina, Schild Stefan, Anthony Mark, Reidl Joachim
Institute of Molecular Biosciences, University of Graz, Humboldtstr. 50, 8010 Graz, Austria.
Insitute of Hygiene and Microbiology, University of Wuerzburg, Josef-Schneider Str. 2 E1, Wuerzburg 97080, Germany.
Int J Med Microbiol. 2014 May;304(3-4):490-8. doi: 10.1016/j.ijmm.2014.02.010. Epub 2014 Mar 2.
Haemophilus influenzae is a Gram-negative bacillus and a frequent commensal of the human nasopharynx. Earlier work demonstrated that in H. influenzae type b, l-lactate metabolism is associated with serum resistance and in vivo survival of the organism. To further gain insight into lactate utilization of the non-typeable (NTHi) isolate 2019 and laboratory prototype strain Rd KW20, deletion mutants of the l-lactate dehydrogenase (lctD) and permease (lctP) were generated and characterized. It is shown, that the apparent KM of l-lactate uptake is 20.1μM as determined for strain Rd KW20. Comparison of the COPD isolate NTHi 2019-R with the corresponding lctP knockout strain for survival in human serum revealed no lactate dependent serum resistance. In contrast, we observed a 4-fold attenuation of the mutant strain in a murine model of nasopharyngeal colonization. Characterization of lctP transcriptional control shows that the lactate utilization system in H. influenzae is not an inductor inducible system. Rather negative feedback regulation was observed in the presence of l-lactate and this is dependent on the ArcAB regulatory system. Additionally, for 2019 it was found that lactate may have signaling function leading to increased cell growth in late log phase under conditions where no l-lactate is metabolized. This effect seems to be ArcA independent and was not observed in strain Rd KW20. We conclude that l-lactate is an important carbon-source and may act as host specific signal substrate which fine tunes the globally acting ArcAB regulon and may additionally affect a yet unknown signaling system and thus may contribute to enhanced in vivo survival.
流感嗜血杆菌是一种革兰氏阴性杆菌，也是人类鼻咽部常见的共生菌。早期研究表明，在b型流感嗜血杆菌中，L-乳酸代谢与该菌的血清抗性及体内存活有关。为了进一步深入了解不可分型（NTHi）菌株2019和实验室原型菌株Rd KW20对乳酸的利用情况，构建并鉴定了L-乳酸脱氢酶（lctD）和通透酶（lctP）的缺失突变体。结果表明，菌株Rd KW20对L-乳酸摄取的表观米氏常数（KM）为20.1μM。比较慢性阻塞性肺疾病（COPD）分离株NTHi 2019-R和相应的lctP基因敲除菌株在人血清中的存活情况，发现不存在乳酸依赖性血清抗性。相反，在小鼠鼻咽部定植模型中，我们观察到突变株的毒力减弱了4倍。对lctP转录调控的研究表明，流感嗜血杆菌中的乳酸利用系统不是诱导型诱导系统。相反，在L-乳酸存在的情况下观察到负反馈调节，这依赖于ArcAB调节系统。此外，对于菌株2019，发现在不代谢L-乳酸的条件下，乳酸可能具有信号传导功能，导致对数后期细胞生长增加。这种效应似乎不依赖于ArcA，在菌株Rd KW20中未观察到。我们得出结论，L-乳酸是一种重要的碳源，可能作为宿主特异性信号底物，微调全局作用的ArcAB调节子，还可能影响一个未知的信号系统，从而有助于提高体内存活率。
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