Identification and characterization of novel systems for oxygen metabolism and anti-oxidative stress protection in anaerobes

我们的目的是了解专性厌氧菌梭状芽胞杆菌和双歧杆菌对o2敏感的机理。乙酰丁酸梭菌（Clostridium acetobutylicum）是一种高效的丙酮-丁醇发酵菌，它能快速感知生长环境中的O_2污染，并表达O_2响应基因。在本研究中，我们通过纯化蛋白质和表征它们的酶活性来研究o_2响应的错误操纵子酶的功能。我们认为专性厌氧菌C. acetobutylicum具有高效的多酶复合物，可以以NROR作为主电子供体蛋白清除O_2和ROS。双歧杆菌需氧生长抑制的主要因素是生长培养基中H_2O_2的产生。从对h2o2敏感的两歧双歧杆菌中纯化出一种形成h2o2的NADH氧化酶，鉴定为b型DHOD。动力学参数表明，该酶可能参与高曝气环境下H_2O_2的生成。

Our purpose is to know the mechanism of O_2 sensitivity of the obligatory anaerobes Clostridium and Bifidomacterium. Clostridium acetobutylicum, which is well known as an efficient acetone-butanol fermenting bacteria, senses the contamination of O_2 in the growth environments quickly and expresses the O_2 responsive genes. In this study, we investigated the function of O_2-responsive nror operon enzymes by purification of the proteins and characterization of their enzymatic activity. We propose that the obligate anaerobe C. acetobutylicum possesses an efficient multi-enzyme complex that can scavenge O_2 and ROS using NROR as a master electron donor protein. The primary factor responsible for aerobic growth inhibition of Bifidobacterium species is proposed to be the production of H_2O_2 in the growth medium. A H_2O_2-forming NADH oxidase was purified from O_2-sensitive Bifidobacterium bifidum and was identified as a b-type DHOD. The kinetic parameters suggested that the enzyme could be involved in H_2O_2 production in highly aerated environments.