Substrate-Level Phosphorylation Is the Primary Source of Energy Conservation during Anaerobic Respiration of Shewanella oneidensis Strain MR-1
Substrate-Level Phosphorylation Is the Primary Source of Energy Conservation during Anaerobic Respiration of Shewanella oneidensis Strain MR-1
复制标题
DOI：
10.1128/jb.00090-10
复制
发表时间：
2010-07-01
影响因子：
3.2
通讯作者：
Gralnick, Jeffrey A.
中科院分区：
文献类型：
--
作者：
Hunt, Kristopher A.;Flynn, Jeffrey M.;Gralnick, Jeffrey A.
众所周知，呼吸生物利用质子动力通过 F 型 ATP 合酶有氧产生 ATP，并且该过程在厌氧过程中可能逆转以产生质子动力。在这里，我们展示了 Shewanella oneidensis 菌株 MR-1，一种已知能呼吸外源电子受体的非发酵兼性厌氧菌，在厌氧条件下主要通过底物水平磷酸化产生 ATP。测试了缺乏 ackA (SO2915) 和 pta (SO2916) 的突变菌株的生长情况，ackA (SO2915) 和 pta (SO2916) 是乙酸盐产生所需的基因，并且大部分底物水平 ATP 是厌氧产生的。这些突变菌株无法以乳酸和富马酸盐作为电子受体进行厌氧生长，这与产生大量 ATP 的底物水平磷酸化一致。缺乏 ackA 和 pta 的突变菌株也显示出使用 N-乙酰氨基葡萄糖作为碳源和富马酸盐作为电子受体生长缓慢，这与使用该底物的 Entner-Doudoroff 途径产生的一些 ATP 一致。缺乏唯一 F 型 ATP 合酶（SO4746 至 SO4754）的缺失菌株表现出在厌氧条件下 N-乙酰氨基葡萄糖的生长增强和乳酸的轻微缺陷。 ATP 合酶突变体在乳酸厌氧条件下生长，同时表达蛋白视紫红质（一种光依赖性质子泵），当暴露于光时表现出恢复生长，这与 ATP 合酶在厌氧条件下的质子泵作用一致。尽管 S. oneidensis 需要外部电子受体来平衡氧化还原反应并且不发酵，但我们发现底物水平磷酸化是其主要的厌氧能量保存策略。希瓦氏菌 ackA 缺失的表型特征。菌株 MR-4 和其他测序菌株的基因组分析表明，这种策略是希瓦氏菌的共同特征。
It is well established that respiratory organisms use proton motive force to produce ATP via F-type ATP synthase aerobically and that this process may reverse during anaerobiosis to produce proton motive force. Here, we show that Shewanella oneidensis strain MR-1, a nonfermentative, facultative anaerobe known to respire exogenous electron acceptors, generates ATP primarily from substrate-level phosphorylation under anaerobic conditions. Mutant strains lacking ackA (SO2915) and pta (SO2916), genes required for acetate production and a significant portion of substrate-level ATP produced anaerobically, were tested for growth. These mutant strains were unable to grow anaerobically with lactate and fumarate as the electron acceptor, consistent with substrate-level phosphorylation yielding a significant amount of ATP. Mutant strains lacking ackA and pta were also shown to grow slowly using N-acetylglucosamine as the carbon source and fumarate as the electron acceptor, consistent with some ATP generation deriving from the Entner-Doudoroff pathway with this substrate. A deletion strain lacking the sole F-type ATP synthase (SO4746 to SO4754) demonstrated enhanced growth on N-acetylglucosamine and a minor defect with lactate under anaerobic conditions. ATP synthase mutants grown anaerobically on lactate while expressing proteorhodopsin, a light-dependent proton pump, exhibited restored growth when exposed to light, consistent with a proton-pumping role for ATP synthase under anaerobic conditions. Although S. oneidensis requires external electron acceptors to balance redox reactions and is not fermentative, we find that substrate-level phosphorylation is its primary anaerobic energy conservation strategy. Phenotypic characterization of an ackA deletion in Shewanella sp. strain MR-4 and genomic analysis of other sequenced strains suggest that this strategy is a common feature of Shewanella.