Exploring the diversity of pathways of autotrophic carbon assimilation in thermophilic prokaryotes

至少有六种不同的自养途径参与初级生产，更多的途径仍在等待它们的描述，反映了栖息地和生活在其中的自养生物的理化参数的多样性。在高温下发育的嗜热微生物由古生菌和细菌领域的各种（包括最古老的）系统发育群代表。嗜热菌的生化过程非常多样化，能够在其分解代谢和二氧化碳固定途径中使用异常广泛的氧化还原对。作为一种很少被探索但代谢变化很大的生理类群，嗜热微生物有望研究代谢的多样性，特别是自养碳同化，这是本联合项目德国合作伙伴的核心专长。俄罗斯申请人的团队在分离和表征新型嗜热性微生物方面获得了大量专业知识，并拥有大量系统发育和代谢多样化的自养嗜热性原核生物。在这个项目中，两个团队将结合他们的专业知识来探索嗜热自养微生物的多样性及其途径。我们将•筛选具有改良/新型自养途径的微生物，•使用放射性同位素和组学技术分析堪察加半岛、千岛群岛和/或贝加尔湖裂谷区的温泉嗜热菌群，•从这些环境中分离出新型嗜热自养菌，•使用基因组分析确定其二氧化碳固定途径，•研究相应的微生物及其生物化学途径。•确定途径及其修饰的基因组决定因素。对于不具备已知途径基因的生物，我们将概述自养二氧化碳固定的途径。预期的结果要么是新途径的检测，要么是最近描述的逆转氧化三羧酸（roTCA）循环。这是一个令人兴奋的选择，因为迄今为止只知道两个这种隐代谢途径的例子。我们的初步研究已经确定了基因组缺乏已知自养途径关键基因的生物体（热菌，自养脱铁杆菌）。这些生物将首先与活性Desulfurella actitivorans一起研究，以确定roTCA循环的基因组决定因素。该项目的一部分是对环境样本的分析，将揭示自然界中二氧化碳固定途径的分布及其影响。我们期望本项目的工作将扩大我们对嗜热菌自养途径的认识，有助于了解最重要的生物合成过程的生物化学，生态学和进化，并可能导致未知的自养途径/策略的发现。

At least six different autotrophic pathways are involved in primary production, and further pathways are still awaiting their description, reflecting the diversity of the physicochemical parameters of the habitats and of the autotrophic organisms living in them. Thermophilic microorganisms developing at high temperatures are represented by various (including the most ancient) phylogenetic groups in the Archaea and Bacteria domains. Thermophiles are extraordinary diverse in their biochemical processes, being capable to use an unusually wide range of RedOx pairs in their catabolism as well as of CO2 fixation pathways. Being only scarcely explored yet highly metabolically varied physiological group, thermophiles are promising to study diversity of metabolism, in particular autotrophic carbon assimilation, which is the core expertise of the German partner of this joint project. The team of the Russian applicant gained huge expertise in the isolation and characterization of novel thermophiles and has at its disposal a large collection of phylogenetically and metabolically diverse autotrophic thermophilic prokaryotes. In this project, both teams will combine their expertise to explore the diversity of thermophilic autotrophic microorganisms and their pathways. We are going to • screen the available collection for the microorganisms with modified/novel autotrophic pathways,• analyze thermophilic communities of hot springs of Kamchatka, Kuriles and/or the Baikal rift zone using radioisotopic and omics techniques,• isolate novel thermophilic autotrophs from these environments, • determine their CO2 fixation pathways using the genomic analysis,• study the corresponding microorganisms and their pathways biochemically, • identify genomic determinants of the pathways and their modifications.For the organisms that do not possess genes for the known pathways, we will outline the pathway(s) of autotrophic CO2 fixation. The anticipated results are either detection of a novel pathway, or of a recently described reversed oxidative tricarboxylic acid (roTCA) cycle. This is an exciting alternative, as only two examples of this cryptic metabolic pathway are known to date.Our preliminary studies have identified organisms whose genomes lacked key genes of the known autotrophic pathways (Thermus sp., Deferribacter autotrophicus). These organisms will firstly be studied along with Desulfurella acetivorans, which is studied for the identification of genomic determinants of the roTCA cycle. The part of the project, devoted to analysis of environmental samples, will shed light onto the distribution of CO2 fixation pathways in nature as well as their impact. We expect that the work on this project will expand our knowledge about the autotrophic pathways in thermophiles, contribute to the understanding of biochemistry, ecology and evolution of the most important biological synthetic process, and may lead to the discovery of unknown autotrophic pathways/strategies.