Division of Environmental Science and Ecological Engineering, Korea University, Seoul, 136-713, Republic of Korea.
J Microbiol. 2010 Apr;48(2):153-9. doi: 10.1007/s12275-010-0075-0. Epub 2010 May 1.
The zwf, which encodes glucose-6-phosphate dehydrogenase, is repressed by NtrC under nitrogen-limited condition. Previously, we demonstrated that induction of zwf-1 is required for protecting Pseudomonas putida cells under oxidative stress, which could be possible probably because of derepression of HexR on the zwf-1 gene under oxidative stress. These findings led us investigate that NtrC still represses the zwf-1 under nitrogen-limited oxidative stress condition, which makes cells more sensitive under such condition. Interestingly, deletion of the ntrC gene significantly reduces growth rate, but renders cells more resistant to oxidative stress, under nitrogen limited condition in P. putida. More vitality of the ntrC mutant under oxidative stress condition was also confirmed by the fluorogenic redox dye using flow cytometry. The results of transcriptome analysis demonstrated that the derepression of several oxidative stress genes along with the zwf-1 gene might confer high resistance to oxidative stress in the ntrC mutant. Here, we presented the data for the first time, showing that different sets of genes are involved in nitrogen-rich and nitrogen-limited oxidative stress conditions and NtrC-sensed nitrogen availability is one of the most important prerequisite for full cellular defense against oxidative stress in P. putida.
zwf 基因编码葡萄糖-6-磷酸脱氢酶，在氮限制条件下受 NtrC 抑制。此前，我们证明了在氧化应激下，诱导 zwf-1 的表达对于保护 Pseudomonas putida 细胞是必需的，这可能是因为氧化应激下 HexR 对 zwf-1 基因的去抑制。这些发现促使我们研究在氮限制氧化应激条件下，NtrC 是否仍然抑制 zwf-1，这使得细胞在这种条件下更加敏感。有趣的是，在氮限制条件下，ntrC 基因的缺失显著降低了生长速度，但使细胞对氧化应激更具抗性。使用流式细胞术通过荧光氧化还原染料也证实了 ntrC 突变体在氧化应激条件下具有更高的活力。转录组分析的结果表明，除了 zwf-1 基因外，几种氧化应激基因的去抑制可能赋予 ntrC 突变体对氧化应激的高抗性。在这里，我们首次提供了数据，表明在富氮和氮限制氧化应激条件下涉及不同的基因集，而 NtrC 感知的氮可用性是 Pseudomonas putida 细胞全面抵御氧化应激的最重要前提之一。
