Evidence for autotrophic CO2 fixation via the reductive tricarboxylic acid cycle by members of the ε subdivision of proteobacteria
Evidence for autotrophic CO2 fixation via the reductive tricarboxylic acid cycle by members of the ε subdivision of proteobacteria
复制标题
DOI：
10.1128/jb.187.9.3020-3027.2005
复制
发表时间：
2005-05-01
影响因子：
3.2
通讯作者：
Sievert, SM
中科院分区：
文献类型：
--
作者：
Hügler, M;Wirsen, CO;Sievert, SM
根据16 S rRNA基因的研究，变形菌E亚门的细菌已被鉴定为各种环境中微生物群落的重要成员，并且相当多的细菌已被证明是自养生长的。然而，没有关于这些细菌可能使用的自养碳固定途径的信息。本研究对大肠杆菌中的两种化能自养硫氧化菌--硫微螺旋菌Thiomicrospira acetificans和硫弓形杆菌Arcobacter sulfidicus进行了研究。亚类的变形菌，进行了检查已知的自养CO2固定途径的关键酶的活性。这两种生物体的还原性三羧酸循环，ATP柠檬酸裂解酶，2-酮戊二酸：铁氧还蛋白氧化还原酶，丙酮酸：铁氧还蛋白氧化还原酶的关键酶的活动。此外，没有检测到其他CO2固定途径的关键酶的活性，如卡尔文循环、还原乙酰辅酶A途径和3-羟基丙酸循环。除了关键酶外，还可以测量参与还原性三羧酸循环的其他酶的活性。编码ATP柠檬酸裂解酶的α-和β-亚基的基因的部分可以从两种生物体中扩增。这些研究结果代表的第一个直接证据的操作还原性三羧酸循环自养CO2固定在ε-变形菌。由于ε-proteobacteria密切相关，这两种生物是重要的，在许多栖息地，如热液喷口，氧化-硫化物界面，或油田，这些结果表明，通过还原三羧酸循环的自养CO2固定可能比以前认为的更重要。
Based on 16S rRNA gene surveys, bacteria of the E subdivision of proteobacteria have been identified to be important members of microbial communities in a variety of environments, and quite a few have been demonstrated to grow autotrophically. However, no information exists on what pathway of autotrophic carbon fixation these bacteria might use. In this study, Thiomicrospira denitrificans and Candidatus Arcobacter sulfidicus, two chemolithoautotrophic sulfur oxidizers of the E. subdivision of proteobacteria, were examined for activities of the key enzymes of the known autotrophic CO2 fixation pathways. Both organisms contained activities of the key enzymes of the reductive tricarboxylic acid cycle, ATP citrate lyase, 2-oxoglutarate: ferredoxin oxidoreductase, and pyruvate:ferredoxin oxidoreductase. Furthermore, no activities of key enzymes of other CO2 fixation pathways, such as the Calvin cycle, the reductive acetyl coenzyme A pathway, and the 3-hydroxypropionate cycle, could be detected. In addition to the key enzymes, the activities of the other enzymes involved in the reductive tricarboxylic acid cycle could be measured. Sections of the genes encoding the alpha- and beta-subunits of ATP citrate lyase could be amplified from both organisms. These findings represent the first direct evidence for the operation of the reductive tricarboxylic acid cycle for autotrophic CO2 fixation in epsilon-proteobacteria. Since epsilon-proteobacteria closely related to these two organisms are important in many habitats, such as hydrothermal vents, oxic-sulfidic interfaces, or oillfields, these results suggest that autotrophic CO2 fixation via the reductive tricarboxyllic acid cycle might be more important than previously considered.