sp. nov., a mesophilic sulfate-reducing deltaproteobacterium isolated from a deep siliceous mudstone formation

深部珪質泥岩層から単利された中温性硫酸還元菌 sp. nov.

上野 晃生*; 玉澤 聡*; 玉村 修司*; 村上 拓馬*; 木山 保*; 猪股 英紀*; 天野 由記   ; 宮川 和也   ; 玉木 秀幸*; 長沼 毅*; 金子 勝比古*

Ueno, Akio*; Tamazawa, Satoshi*; Tamamura, Shuji*; Murakami, Takuma*; Kiyama, Tamotsu*; Inomata, Hidenori*; Amano, Yuki; Miyakawa, Kazuya; Tamaki, Hideyuki*; Naganuma, Takeshi*; Kaneko, Katsuhiko*

幌延深地層研究計画における地上からのボーリング調査孔であるHDB-6の深度288.7-303.0m区間から採水された地下水中から、新種の嫌気的硫酸還元菌を単離した。これをHN2株と呼ぶ。採水深度の地質は新第三紀堆積岩の稚内層であり、上位の珪藻質泥岩である声問層から珪質泥岩である稚内層への遷移帯に当たる。単離されたHN2株は、温度5-43C及びpH6.5-7.5の環境において成長が確認された。HN2株は、硫酸塩や亜硫酸塩, Fe, マンガン酸化物等を電子受容体とし、硫黄元素や硝酸塩,亜硝酸塩は電子受容体として使用しない。HN2株は、NaClを必要としないが、最大でNaCl濃度4%(w/v)の高塩濃度環境において生息できた。表現型・分子的遺伝情報から、HN2株を新種と判断し、 sp. nov.と命名する。

A novel mesophilic sulfate-reducing bacterium, designated strain HN2, was isolated from groundwater sampled from the subsurface Miocene Wakkanai Formation located in Horonobe, Hokkaido, Japan. The cells were Gram-negative rods, with motility conferred by a single polar flagellum. The isolate expressed desulfoviridin, but no catalase or oxidase activities was detected. Strain HN2 grew in a temperature range of 5-43 C (optimum, 35 C) and in a pH range of 6.5-7.5 (optimum, pH 7.0-7.3). It used sulfate, thiosulfate, dimethyl sulfoxide, anthraquinone-2,6-disulfonate, Fe, and manganese oxide as electron acceptors, but not elemental sulfur, nitrite, or nitrate. The bacterium showed very weak growth with sulfite as the electron acceptor. The strain fermented pyruvate and cysteine in the absence of sulfate, but not malate or succinate. The bacterium did not require NaCl, but tolerated up to 4% NaCl (w/v). Strain HN2 did not require vitamins. The G+C content of the genomic DNA was 56.66 mol%. A 16S rRNA gene sequence analysis showed that the closest recognized relative of strain HN2 is JS1 (97.0% similarity). The average nucleotide identity (ANI) value between strain HN2 and D. JS1 was 79.8%. Based on the phenotypic and molecular genetic evidence, the isolate is assigned to the new species sp. nov. The type strain is HN2 (=DSM 101010 =NBRC 112213).