Sattley W Matthew, Swingley Wesley D, Burchell Brad M, Dewey Emma D, Hayward Mackenzie K, Renbarger Tara L, Shaffer Kathryn N, Stokes Lynn M, Gurbani Sonja A, Kujawa Catrina M, Nuccio D Adam, Schladweiler Jacob, Touchman Jeffrey W, Wang-Otomo Zheng-Yu, Blankenship Robert E, Madigan Michael T
Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA.
Department of Biological Sciences, Northern Illinois University, Dekalb, IL, 60115, USA.
Photosynth Res. 2022 Jan;151(1):125-142. doi: 10.1007/s11120-021-00870-y. Epub 2021 Oct 20.
The complete genome sequence of the thermophilic purple sulfur bacterium Thermochromatium tepidum strain MC (DSM 3771) is described and contrasted with that of its mesophilic relative Allochromatium vinosum strain D (DSM 180) and other Chromatiaceae. The Tch. tepidum genome is a single circular chromosome of 2,958,290 base pairs with no plasmids and is substantially smaller than the genome of Alc. vinosum. The Tch. tepidum genome encodes two forms of RuBisCO and contains nifHDK and several other genes encoding a molybdenum nitrogenase but lacks a gene encoding a protein that assembles the Fe-S cluster required to form a functional nitrogenase molybdenum-iron cofactor, leaving the phototroph phenotypically Nif. Tch. tepidum contains genes necessary for oxidizing sulfide to sulfate as photosynthetic electron donor but is genetically unequipped to either oxidize thiosulfate as an electron donor or carry out assimilative sulfate reduction, both of which are physiological hallmarks of Alc. vinosum. Also unlike Alc. vinosum, Tch. tepidum is obligately phototrophic and unable to grow chemotrophically in darkness by respiration. Several genes present in the Alc. vinosum genome that are absent from the genome of Tch. tepidum likely contribute to the major physiological differences observed between these related purple sulfur bacteria that inhabit distinct ecological niches.
本文描述了嗜热紫色硫细菌嗜温嗜热色菌菌株MC（DSM 3771）的完整基因组序列，并将其与其嗜温亲缘种嗜酒嗜热色菌菌株D（DSM 180）及其他着色菌科细菌的基因组序列进行了对比。嗜温嗜热色菌的基因组是一条由2,958,290个碱基对组成的单一环状染色体，无质粒，且比嗜酒嗜热色菌的基因组小得多。嗜温嗜热色菌的基因组编码两种形式的核酮糖-1,5-二磷酸羧化酶/加氧酶（RuBisCO），包含固氮酶结构基因nifHDK及其他几个编码钼固氮酶的基因，但缺少一个编码组装形成功能性固氮酶钼铁辅因子所需铁硫簇的蛋白质的基因，使得该光合生物在表型上为固氮缺陷型。嗜温嗜热色菌含有将硫化物氧化为硫酸盐作为光合电子供体所需的基因，但在基因层面上不具备将硫代硫酸盐作为电子供体进行氧化或进行同化性硫酸盐还原的能力，而这两者都是嗜酒嗜热色菌的生理特征。与嗜酒嗜热色菌不同的是，嗜温嗜热色菌严格依赖光养生长，无法在黑暗中通过呼吸作用进行化能营养生长。嗜酒嗜热色菌基因组中存在而嗜温嗜热色菌基因组中缺失的几个基因，可能导致了这些栖息于不同生态位的相关紫色硫细菌之间观察到的主要生理差异。
