NITE Biological Resource Center (NBRC), National Institute of Technology and Evaluation (NITE), 2-5-8 Kazusakamatari, Kisarazu, Chiba 292-0818, Japan.
Faculty of Science, Kyushu University, Higashi-ku, Fukuoka 812-8581, Japan.
Int J Syst Evol Microbiol. 2014 Jun;64(Pt 6):2128-2136. doi: 10.1099/ijs.0.060137-0. Epub 2014 Mar 27.
Two thermophilic, strictly anaerobic, Gram-negative bacteria, designated strains AZM34c06(T) and AZM44c09(T), were isolated from terrestrial hot springs in Japan. The optimum growth conditions for strain AZM34c06(T) were 60 °C, pH 7.4 and 0% additional NaCl, and those for strain AZM44c09(T) were 70 °C, pH 7.4 and 0% additional NaCl. Complete genome sequencing was performed for both strains, revealing genome sizes of 2.19 Mbp (AZM34c06(T)) and 2.01 Mbp (AZM44c09(T)). Phylogenetic analyses based on 16S rRNA gene sequences and the concatenated predicted amino acid sequences of 33 ribosomal proteins showed that both strains belonged to the genus Thermotoga. The closest relatives of strains AZM34c06(T) and AZM44c09(T) were the type strains of Thermotoga lettingae (96.0% similarity based on the 16S rRNA gene and 84.1% similarity based on ribosomal proteins) and Thermotoga hypogea (98.6 and 92.7% similarity), respectively. Using blast, the average nucleotide identity was 70.4-70.5% when comparing strain AZM34c06(T) and T. lettingae TMO(T) and 76.6% when comparing strain AZM44c09(T) and T. hypogea NBRC 106472(T). Both values are far below the 95% threshold value for species delineation. In view of these data, we propose the inclusion of the two isolates in the genus Thermotoga within two novel species, Thermotoga profunda sp. nov. (type strain AZM34c06(T) = NBRC 106115(T) = DSM 23275(T)) and Thermotoga caldifontis sp. nov. (type strain AZM44c09(T) = NBRC 106116(T) = DSM 23272(T)).
两株嗜热、严格厌氧、革兰氏阴性细菌，分别命名为菌株 AZM34c06(T) 和 AZM44c09(T)，从日本的陆地温泉中分离得到。菌株 AZM34c06(T) 的最适生长条件为 60°C、pH7.4 和 0%额外 NaCl，菌株 AZM44c09(T) 的最适生长条件为 70°C、pH7.4 和 0%额外 NaCl。对两株菌进行了全基因组测序，结果显示基因组大小分别为 2.19 Mbp（AZM34c06(T)）和 2.01 Mbp（AZM44c09(T)）。基于 16S rRNA 基因序列和 33 个核糖体蛋白预测的氨基酸序列的系统发育分析表明，两株菌均属于 Thermotoga 属。菌株 AZM34c06(T) 和 AZM44c09(T) 的最接近的亲缘种是 Thermotoga lettingae（基于 16S rRNA 基因的相似度为 96.0%，基于核糖体蛋白的相似度为 84.1%）和 Thermotoga hypogea（相似度分别为 98.6%和 92.7%）的模式株。使用 blast 进行比较时，菌株 AZM34c06(T) 与 T. lettingae TMO(T) 的平均核苷酸同一性为 70.4-70.5%，菌株 AZM44c09(T) 与 T. hypogea NBRC 106472(T) 的平均核苷酸同一性为 76.6%。这两个数值都远低于物种划分的 95%阈值。鉴于这些数据，我们建议将这两个分离株归入 Thermotoga 属中的两个新种，即 Thermotoga profunda sp. nov.（模式株 AZM34c06(T) = NBRC 106115(T) = DSM 23275(T)）和 Thermotoga caldifontis sp. nov.（模式株 AZM44c09(T) = NBRC 106116(T) = DSM 23272(T)）。
