Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, SP, Brazil.
FEMS Microbiol Lett. 2010 Feb;303(1):48-54. doi: 10.1111/j.1574-6968.2009.01860.x. Epub 2009 Nov 23.
A Caulobacter crescentus rho::Tn5 mutant strain presenting a partially functional transcription termination factor Rho is highly sensitive to hydrogen peroxide in both exponential and stationary phases. The mutant was shown to be permanently under oxidative stress, based on fluorophore oxidation, and also to be sensitive to tert-butyl hydroperoxide and paraquat. However, the results showed that the activities of superoxide dismutases CuZnSOD and FeSOD and the alkylhydroperoxide reductase ahpC mRNA levels in the rho mutant were comparable to the wild-type control in the exponential and stationary phases. In contrast, the KatG catalase activity of the rho mutant strain was drastically decreased and did not show the expected increase in the stationary phase compared with the exponential phase. Transcription of the katG gene was increased in the rho mutant and the levels of the immunoreactive KatG protein do not differ considerably compared with the wild type in the stationary phase, suggesting that KatG activity is affected in a translational or a post-translational step.
新月柄杆菌 rho::Tn5 突变株呈现部分功能转录终止因子 Rho，在指数期和静止期对过氧化氢均高度敏感。基于荧光团氧化，该突变株被证明一直处于氧化应激下，并且对叔丁基过氧化物和百草枯敏感。然而，结果表明，rho 突变株中超氧化物歧化酶 CuZnSOD 和 FeSOD 的活性以及烷基氢过氧化物还原酶 ahpC mRNA 水平在指数期和静止期与野生型对照相当。相比之下，rho 突变株的 KatG 过氧化氢酶活性显著降低，与指数期相比，静止期没有表现出预期的增加。rho 突变株中 katG 基因的转录增加，并且在静止期，免疫反应性 KatG 蛋白的水平与野生型相比没有显著差异，表明 KatG 活性受到翻译或翻译后步骤的影响。
