Department of Oceanography, Florida State University, Tallahassee, FL 32306, USA.
Department of Biology, Georgia State University, Atlanta, GA 30303, USA.
Int J Syst Evol Microbiol. 2010 Mar;60(Pt 3):546-553. doi: 10.1099/ijs.0.010843-0. Epub 2009 Aug 4.
An Fe(III)- and uranium(VI)-reducing bacterium, designated strain FRC-32(T), was isolated from a contaminated subsurface of the USA Department of Energy Oak Ridge Field Research Center (ORFRC) in Oak Ridge, Tennessee, where the sediments are exposed to mixed waste contamination of radionuclides and hydrocarbons. Analyses of both 16S rRNA gene and the Geobacteraceae-specific citrate synthase (gltA) mRNA gene sequences retrieved from ORFRC sediments indicated that this strain was abundant and active in ORFRC subsurface sediments undergoing uranium(VI) bioremediation. The organism belonged to the subsurface clade of the genus Geobacter and shared 92-98 % 16S rRNA gene and 75-81 % rpoB gene sequence similarities with other recognized species of the genus. In comparison to its closest relative, Geobacter uraniireducens Rf4(T), according to 16S rRNA gene sequence similarity, strain FRC-32(T) showed a DNA-DNA relatedness value of 21 %. Cells of strain FRC-32(T) were Gram-negative, non-spore-forming, curved rods, 1.0-1.5 microm long and 0.3-0.5 microm in diameter; the cells formed pink colonies in a semisolid cultivation medium, a characteristic feature of the genus Geobacter. The isolate was an obligate anaerobe, had temperature and pH optima for growth at 30 degrees C and pH 6.7-7.3, respectively, and could tolerate up to 0.7 % NaCl although growth was better in the absence of NaCl. Similar to other members of the Geobacter group, strain FRC-32(T) conserved energy for growth from the respiration of Fe(III)-oxyhydroxide coupled with the oxidation of acetate. Strain FRC-32(T) was metabolically versatile and, unlike its closest relative, G. uraniireducens, was capable of utilizing formate, butyrate and butanol as electron donors and soluble ferric iron (as ferric citrate) and elemental sulfur as electron acceptors. Growth on aromatic compounds including benzoate and toluene was predicted from preliminary genomic analyses and was confirmed through successive transfer with fumarate as the electron acceptor. Thus, based on genotypic, phylogenetic and phenotypic differences, strain FRC-32(T) is considered to represent a novel species of the genus Geobacter, for which the name Geobacter daltonii sp. nov. is proposed. The type strain is FRC-32(T) (=DSM 22248(T)=JCM 15807(T)).
一株同时还原铁（III）和铀（VI）的细菌，被命名为 FRC-32(T) 菌株，从美国能源部橡树岭现场研究中心（ORFRC）受混合废物污染的地下水中分离得到，这些沉积物暴露在放射性核素和碳氢化合物的混合废物污染中。对来自 ORFRC 沉积物的 16S rRNA 基因和 Geobacteraceae 特异性柠檬酸合酶（gltA）mRNA 基因序列的分析表明，该菌株在进行铀（VI）生物修复的 ORFRC 地下沉积物中丰富且活跃。该生物属于地下分支的 Geobacter 属，与其他公认的 Geobacter 属物种相比，16S rRNA 基因和 rpoB 基因序列相似性分别为 92-98%和 75-81%。根据 16S rRNA 基因序列相似性，与最接近的亲缘关系物种 Geobacter uraniireducens Rf4(T)相比，FRC-32(T) 菌株的 DNA-DNA 相关值为 21%。FRC-32(T) 菌株的细胞为革兰氏阴性、非孢子形成、弯曲杆菌，长 1.0-1.5 微米，直径 0.3-0.5 微米；细胞在半固体培养物中形成粉红色菌落，这是 Geobacter 属的特征。该分离株是专性厌氧菌，生长的最适温度和 pH 值分别为 30°C 和 pH6.7-7.3，尽管在没有 NaCl 的情况下生长更好，但可以耐受高达 0.7%的 NaCl。与 Geobacter 组的其他成员类似，FRC-32(T) 菌株通过将 Fe(III)-氢氧化物呼吸与乙酸氧化偶联来保存生长所需的能量。FRC-32(T) 菌株代谢能力多样，与最接近的亲缘关系物种 G. uraniireducens 不同，它能够利用甲酸盐、丁酸盐和丁醇作为电子供体，以及可溶性三价铁（如柠檬酸铁）和元素硫作为电子受体。根据初步的基因组分析，预测了该菌株对芳香族化合物（包括苯甲酸和甲苯）的生长，通过以富马酸盐作为电子受体的连续转移得到了证实。因此，基于基因型、系统发育和表型差异，FRC-32(T) 菌株被认为代表了 Geobacter 属的一个新种，建议将其命名为 Geobacter daltonii sp. nov.。该模式菌株为 FRC-32(T)（=DSM 22248(T)=JCM 15807(T)）。
