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首页> 外文期刊>Applied and Environmental Microbiology >Abundance of Reverse Tricarboxylic Acid Cycle Genes in Free-Living Microorganisms at Deep-Sea Hydrothermal Vents
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Abundance of Reverse Tricarboxylic Acid Cycle Genes in Free-Living Microorganisms at Deep-Sea Hydrothermal Vents

机译：深海热液喷口自由活动微生物中逆三羧酸循环基因的丰度

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Since the discovery of hydrothermal vents more than 25 years ago, the Calvin-Bassham-Benson (Calvin) cycle has been considered the principal carbon fixation pathway in this microbe-based ecosystem. However, on the basis of recent molecular data of cultured free-living and noncultured episymbiotic members of the epsilon subdivision of Proteobacteria and earlier carbon isotope data of primary consumers, an alternative autotrophic pathway may predominate. Here, genetic and culture-based approaches demonstrated the abundance of reverse tricarboxylic acid cycle genes compared to the abundance of Calvin cycle genes in microbial communities from two geographically distinct deep-sea hydrothermal vents. PCR with degenerate primers for three key genes in the reverse tricarboxylic acid cycle and form I and form II of ribulose 1,5-bisphosphate carboxylase/oxygenase (Calvin cycle marker gene) were utilized to demonstrate the abundance of the reverse tricarboxylic acid cycle genes in diverse vent samples. These genes were also expressed in at least one chimney sample. Diversity, similarity matrix, and phylogenetic analyses of cloned samples and amplified gene products from autotrophic enrichment cultures suggest that the majority of autotrophs that utilize the reverse tricarboxylic acid cycle are members of the epsilon subdivision of Proteobacteria. These results parallel the results of previously published molecular surveys of 16S rRNA genes, demonstrating the dominance of members of the epsilon subdivision of Proteobacteria in free-living hydrothermal vent communities. Members of the epsilon subdivision of Proteobacteria are also ubiquitous in many other microaerophilic to anaerobic sulfidic environments, such as the deep subsurface. Therefore, the reverse tricarboxylic acid cycle may be a major autotrophic pathway in these environments and significantly contribute to global autotrophic processes.
机译：自从25年前发现热液喷口以来，卡尔文-巴瑟姆-本森（卡尔文）循环一直被认为是这个基于微生物的生态系统中的主要固碳途径。但是，根据变形杆菌的ε子细分的自由活动和未培养的附生共生成员的最新分子数据以及主要消费者的早期碳同位素数据，可以选择另一种自养途径。在这里，基于遗传和文化的方法表明，与来自两个地理上不同的深海热液喷口的微生物群落中的加尔文循环基因的丰度相比，反向三羧酸循环基因的丰度更高。用简并引物对反向三羧酸循环中三个关键基因以及核糖1,5-双磷酸羧化酶/加氧酶的I型和II型（加尔文循环标记基因）进行PCR来证明反向三羧酸循环基因的丰度。各种排气孔样品。这些基因也在至少一个烟囱样品中表达。从自养富集培养中克隆的样品和扩增的基因产物的多样性，相似性矩阵和系统发育分析表明，利用反向三羧酸循环的大多数自养生物是变形杆菌的ε细分的成员。这些结果与以前发表的16S rRNA基因分子调查的结果相符，证明了在自由生活的热液喷口群落中，变形杆菌的ε细分成员的优势。变形杆菌的ε细分的成员在许多其他从微需氧到厌氧的硫化环境（例如深地下）中也普遍存在。因此，反向三羧酸循环在这些环境中可能是主要的自养途径，并且对整体自养过程有重要贡献。

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