Department of Pediatrics, University Hospital Carl Gustav Carus, Technische Universität Dresden, Fetscherstrasse 74, 01307, Dresden, Germany.
Curr Microbiol. 2019 Jun;76(6):698-705. doi: 10.1007/s00284-019-01683-y. Epub 2019 Apr 6.
Group A streptococcus (GAS) is an important human pathogen whose clinical isolates differ in their ability to produce hydrogen peroxide (HO). HO is primarily produced by the enzyme lactate oxidase (LctO), an in depth in silico research revealed that all genome-sequenced GAS possess the required gene lctO. The importance of lctO for GAS is underlined by its highly conserved catabolite control element (cre box) as well as its perfect promotor sequence in comparison to the known consensus sequences of the Gram-positive model organism Bacillus subtilis. In this study, we provide further insight in the function and regulation of lactate oxidase by analyzing a large group of clinical GAS isolates. We found that HO production increased over time in the late stationary phase; after 4 days of incubation, 5.4% of the isolates showed a positive result at 37 °C, while the rate increased to 16.4% at 20 °C. This correlation between HO production and low temperatures suggests additional regulatory mechanisms for lctO besides catabolite control protein A (CcpA) and indicates that lctO might play a role for GAS energy metabolism at sub-body temperatures. Furthermore, we could identify that HO production was different among clinical isolates; we could correlate HO production to emm-types, indicating that emm-types 6 and 75 had the highest rate of HO production. The emm-type- and temperature-dependent HO production of clinical GAS isolates might contribute to their different survival strategies.
A 组链球菌（GAS）是一种重要的人类病原体，其临床分离株在产生过氧化氢（HO）的能力上存在差异。HO 主要由酶乳酸氧化酶（LctO）产生，深入的计算机研究表明，所有基因组测序的 GAS 都具有所需的基因 lctO。lctO 对 GAS 的重要性体现在其高度保守的分解代谢物控制元件（cre 盒）以及与其相比，革兰氏阳性模式生物枯草芽孢杆菌的已知共识序列相比，其完美的启动子序列。在这项研究中，我们通过分析一大组临床 GAS 分离株，进一步深入了解乳酸氧化酶的功能和调节。我们发现，HO 的产生在晚期静止期随着时间的推移而增加；在孵育 4 天后，37°C 时 5.4%的分离株呈阳性，而在 20°C 时，该比率增加到 16.4%。HO 产生与低温之间的这种相关性表明，除了分解代谢物控制蛋白 A（CcpA）之外，lctO 还存在其他调节机制，并表明 lctO 可能在亚体温下对 GAS 能量代谢发挥作用。此外，我们可以确定 HO 的产生在临床分离株之间存在差异；我们可以将 HO 的产生与 emm 型相关联，表明 emm 型 6 和 75 的 HO 产生率最高。临床 GAS 分离株的 emm 型和温度依赖性 HO 产生可能有助于它们的不同生存策略。
