Department of Biochemistry and Molecular Biology and Center for Biomolecular Structure and Function, The Pennsylvania State University , S-235 Frear Building, University Park, PA 16802, USA.
Arch Microbiol. 2009 Nov;191(11):853-67. doi: 10.1007/s00203-009-0514-7. Epub 2009 Sep 27.
The genome of the green sulfur bacterium Chlorobaculum (Cba.) tepidum, a strictly anaerobic photolithoautotroph, is predicted to encode more than ten genes whose products are potentially involved in protection from reactive oxygen species and an oxidative stress response. The encoded proteins include cytochrome bd quinol oxidase, NADH oxidase, rubredoxin oxygen oxidoreductase, several thiol peroxidases, alkyl hydroperoxide reductase, superoxide dismutase, methionine sulfoxide reductase, and rubrerythrin. To test the physiological functions of some of these proteins, ten genes were insertionally inactivated. Wild-type Cba. tepidum cells were very sensitive to oxygen in the light but were remarkably resistant to oxygen in the dark. When wild-type and mutant cells were subjected to air for various times under dark or light condition, significant decreases in viability were detected in most of the mutants relative to wild type. Treatments with hydrogen peroxide (H(2)O(2)), tert-butyl hydroperoxide (t-BOOH) and methyl viologen resulted in more severe effects in most of the mutants than in the wild type. The results demonstrated that these putative antioxidant proteins combine to form an effective defense against oxygen and reactive oxygen species. Reverse-transcriptase polymerase chain reaction studies showed that the genes with functions in oxidative stress protection were constitutively transcribed under anoxic growth conditions.
绿硫菌（Cba. tepidum）的基因组，是严格厌氧的光合自养生物，预计编码超过十个基因，其产物可能涉及保护免受活性氧和氧化应激反应。编码的蛋白质包括细胞色素 bd 醌氧化酶、NADH 氧化酶、Rubredoxin 氧氧化还原酶、几种硫氧还蛋白、烷烃氢过氧化物还原酶、超氧化物歧化酶、甲硫氨酸亚砜还原酶和 rubrerythrin。为了测试这些蛋白质中的一些生理功能，十个基因被插入失活。野生型 Cba. tepidum 细胞在光照下对氧气非常敏感，但在黑暗中对氧气具有显著的抗性。当野生型和突变型细胞在黑暗或光照条件下暴露于空气中不同时间时，与野生型相比，大多数突变体的存活率显著降低。用过氧化氢 (H(2)O(2))、叔丁基过氧化物 (t-BOOH) 和甲紫精处理后，大多数突变体比野生型受到更严重的影响。结果表明，这些假定的抗氧化蛋白结合在一起形成了一种有效的防御机制，以对抗氧气和活性氧。逆转录聚合酶链反应研究表明，在缺氧生长条件下，具有氧化应激保护功能的基因是组成型转录的。
