The Growth and Survival of Mycobacterium smegmatis Is Enhanced by Co-Metabolism of Atmospheric H2
The Growth and Survival of Mycobacterium smegmatis Is Enhanced by Co-Metabolism of Atmospheric H2
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DOI：
10.1371/journal.pone.0103034
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发表时间：
2014-07-24
期刊：
影响因子：
3.7
通讯作者：
Cook, Gregory M.
中科院分区：
文献类型：
--
作者：
Greening, Chris;Villas-Boas, Silas G.;Cook, Gregory M.
污垢分枝杆菌能够清除大气中存在的微量H-2，但其生理功能和重要性尚不清楚。我们已经证明，这种生物体中的大气H-2氧化依赖于两个在系统发育和动力学上不同的高亲和力氢酶：Hyd1(MSMEG_2262-2263)和Hyd2(MSMEG_2720-2719)。在这项研究中，我们通过比较野生型和Delta Hyd2细胞的存活率、能量学、转录物和代谢物来探索删除Hyd2对细胞生理的影响。与野生型相比，Delta hyd2突变体的长期存活率显著降低。此外，突变株在一系列条件下的生长效率较低，最明显的是在短链脂肪酸代谢期间；当乙酸酯作为唯一碳源时，Delta hy2菌株的生长速度和生长产量降低了两倍。当细胞在高H-2气氛中生长时，Hyd1补偿了Hyd2的损失。细胞参数分析表明，Hyd2不是产生膜电位、维持细胞内pH动态平衡或维持氧化还原平衡所必需的。然而，基因芯片分析表明Delta Hyd2细胞缺乏还原剂，并通过重新连接中央代谢来补偿；编码氧化脱羧基途径、尿素循环和ABC转运体介导的输入的蛋白质的转录本在Delta Hyd2突变体中显著丰富。代谢组图谱一致地显示Delta hyd2突变体的细胞内氨基酸增加。我们认为，大气中的氢氧化在分枝杆菌细胞中有两个主要作用：在混合营养生长期间产生还原剂，在休眠期间维持呼吸链。
The soil bacterium Mycobacterium smegmatis is able to scavenge the trace concentrations of H-2 present in the atmosphere, but the physiological function and importance of this activity is not understood. We have shown that atmospheric H-2 oxidation in this organism depends on two phylogenetically and kinetically distinct high-affinity hydrogenases, Hyd1 (MSMEG_2262-2263) and Hyd2 (MSMEG_2720-2719). In this study, we explored the effect of deleting Hyd2 on cellular physiology by comparing the viability, energetics, transcriptomes, and metabolomes of wild-type vs. Delta hyd2 cells. The long-term survival of the Delta hyd2 mutant was significantly reduced compared to the wild-type. The mutant additionally grew less efficiently in a range of conditions, most notably during metabolism of short-chain fatty acids; there was a twofold reduction in growth rate and growth yield of the Delta hyd2 strain when acetate served as the sole carbon source. Hyd1 compensated for loss of Hyd2 when cells were grown in a high H-2 atmosphere. Analysis of cellular parameters showed that Hyd2 was not necessary to generate the membrane potential, maintain intracellular pH homeostasis, or sustain redox balance. However, microarray analysis indicated that Delta hyd2 cells were starved for reductant and compensated by rewiring central metabolism; transcripts encoding proteins responsible for oxidative decarboxylation pathways, the urea cycle, and ABC transporter-mediated import were significantly more abundant in the Delta hyd2 mutant. Metabolome profiling consistently revealed an increase in intracellular amino acids in the Delta hyd2 mutant. We propose that atmospheric H2 oxidation has two major roles in mycobacterial cells: to generate reductant during mixotrophic growth and to sustain the respiratory chain during dormancy.