Sato Yuya, Kanbe Haruna, Miyano Hirosuke, Sambongi Yoshihiro, Arai Hiroyuki, Ishii Masaharu, Igarashi Yasuo
Department of Biotechnology, Graduate School of Agricultural and Life Science, The University of Tokyo, 1-1-1 Yayoi, Tokyo 113-8657, Japan.
Biosci Biotechnol Biochem. 2012;76(9):1677-81. doi: 10.1271/bbb.120210. Epub 2012 Sep 7.
Hydrogenobacter thermophilus is a chemolithoautotroph that utilizes not only hydrogen (H(2)) but also thiosulfate as sole source of energy and assimilates carbon dioxide via the reductive tricarboxylic acid (RTCA) cycle. We systematically carried out transcriptome analysis of metabolic enzymes in both H(2)- and thiosulfate-grown H. thermophilus cells. The analysis indicated that the expression of hydrogenase genes is repressed under thiosulfate oxidation conditions as compared with H(2) oxidation conditions. This was confirmed by enzyme assay. In contrast, some genes for sulfur metabolism, including sox genes, showed almost the same expression levels under both conditions. In addition, the genes for the RTCA cycle showed high expression levels under both conditions. It was suggested that sulfur metabolism and the RTCA cycle function as forms of basal metabolism, and H(2) oxidation is inducible. Switching of H(2) oxidation can be advantageous for the lifestyle of this bacterium in nature.
嗜热氢杆菌是一种化能无机自养菌，它不仅利用氢气（H₂），还利用硫代硫酸盐作为唯一能量来源，并通过还原性三羧酸（RTCA）循环同化二氧化碳。我们系统地对在以氢气和硫代硫酸盐为生长底物的嗜热氢杆菌细胞中的代谢酶进行了转录组分析。分析表明，与氢气氧化条件相比，在硫代硫酸盐氧化条件下氢化酶基因的表达受到抑制。酶活性测定证实了这一点。相反，包括sox基因在内的一些硫代谢基因在两种条件下的表达水平几乎相同。此外，RTCA循环相关基因在两种条件下均表现出高表达水平。这表明硫代谢和RTCA循环作为基础代谢形式发挥作用，而氢气氧化是可诱导的。对于这种细菌在自然环境中的生存方式而言，氢气氧化的转换可能具有优势。
