Autotrophic CO2 fixation pathways in archaea (Crenarchaeota)
Autotrophic CO2 fixation pathways in archaea (Crenarchaeota)
复制标题
DOI：
10.1007/s00203-002-0512-5
复制
发表时间：
2003-03-01
影响因子：
2.8
通讯作者：
Fuchs, G
中科院分区：
文献类型：
--
作者：
Hügler, M;Huber, H;Fuchs, G
对泉古菌门不同科的代表性自养和嗜热古菌物种进行了检测，以寻找已知的自养CO2固定途径的关键酶。热变形菌科（Thermoproteaceae）的Pyrobaculum islandicum含有还原性柠檬酸循环的关键酶。这一发现与相关嗜热变形杆菌中该途径的运作一致。深海热解菌（Pyrodictium abyssi）和隐热解菌（Pyrodictium occultum）含有核酮糖1，5-二磷酸羧化酶，该酶在沸水中有活性。然而，磷酸核酮糖激酶活性是不可检测的。卡尔文循环的运行仍有待证明。islandicus和pacificus（脱硫球菌科）含有丙酮酸氧化还原酶作为潜在的羧化酶，但显然缺乏已知途径的关键酶;它们的自养CO2固定模式存在争议。Metallosphaera sedula、Acidianus ambivalens和Sulfolobus sp.菌株VE 6（Sulfolobaceae）含有3-羟基丙酸循环的关键酶。这一发现与相关Acidianus brierleyi和Sulfolobus metallicus中乙酰辅酶A（CoA）和丙酰辅酶A羧化酶活性的证明一致。对盾壳菌中心碳代谢相关酶进行了较详细的研究。在自养生长过程中，3-羟基丙酸循环的酶活性强烈上调，支持它们在CO2固定中的作用。然而，不能证明乙酰辅酶A从琥珀酰辅酶A的形成，这表明乙酰辅酶A再生的修饰途径。我们的结论是Crenarchaeota表现出马赛克的三个或可能四个自养途径。到目前为止，这些途径的分布与Crenarchaeota的16 S-rRNA分类群相关。
Representative autotrophic and thermophilic archaeal species of different families of Crenarchaeota were examined for key enzymes of the known autotrophic CO2 fixation pathways. Pyrobaculum islandicum (Thermoproteaceae) contained key enzymes of the reductive citric acid cycle. This finding is consistent with the operation of this pathway in the related Thermoproteus neutrophilus. Pyrodictium abyssi and Pyrodictium occultum (Pyrodictiaceae) contained ribulose 1,5-bisphosphate carboxylase, which was active in boiling water. Yet, phosphoribulokinase activity was not detectable. Operation of the Calvin cycle remains to be demonstrated. Ignicoccus islandicus and Ignicoccus pacificus (Desulfurococcaceae) contained pyruvate oxidoreductase as potential carboxylating enzyme, but apparently lacked key enzymes of known pathways; their mode of autotrophic CO2 fixation is at issue. Metallosphaera sedula, Acidianus ambivalens and Sulfolobus sp. strain VE6 (Sulfolobaceae) contained key enzymes of a 3-hydroxypropionate cycle. This finding is in line with the demonstration of acetyl-coenzyme A (CoA) and propionyl-CoA carboxylase activities in the related Acidianus brierleyi and Sulfolobus metallicus. Enzymes of central carbon metabolism in Metallosphaera sedula were studied in more detail. Enzyme activities of the 3-hydroxypropionate cycle were strongly up-regulated during autotrophic growth, supporting their role in CO2 fixation. However, formation of acetyl-CoA from succinylCoA could not be demonstrated, suggesting a modified pathway of acetyl-CoA regeneration. We conclude that Crenarchaeota exhibit a mosaic of three or possibly four autotrophic pathways. The distribution of the pathways so far correlates with the 16S-rRNA-based taxa of the Crenarchaeota.