Alawi Mashal, Lipski André, Sanders Tina, Pfeiffer Eva Maria, Spieck Eva
Department of Biology, Biocenter Klein Flottbek, University of Hamburg, Hamburg, Germany.
ISME J. 2007 Jul;1(3):256-64. doi: 10.1038/ismej.2007.34.
Permafrost-affected soils of the Siberian Arctic were investigated with regard to identification of nitrite oxidizing bacteria active at low temperature. Analysis of the fatty acid profiles of enrichment cultures grown at 4 degrees C, 10 degrees C and 17 degrees C revealed a pattern that was different from that of known nitrite oxidizers but was similar to fatty acid profiles of Betaproteobacteria. Electron microscopy of two enrichment cultures grown at 10 degrees C showed prevalent cells with a conspicuous ultrastructure. Sequence analysis of the 16S rRNA genes allocated the organisms to a so far uncultivated cluster of the Betaproteobacteria, with Gallionella ferruginea as next related taxonomically described organism. The results demonstrate that a novel genus of chemolithoautotrophic nitrite oxidizing bacteria is present in polygonal tundra soils and can be enriched at low temperatures up to 17 degrees C. Cloned sequences with high sequence similarities were previously reported from mesophilic habitats like activated sludge and therefore an involvement of this taxon in nitrite oxidation in nonarctic habitats is suggested. The presented culture will provide an opportunity to correlate nitrification with nonidentified environmental clones in moderate habitats and give insights into mechanisms of cold adaptation. We propose provisional classification of the novel nitrite oxidizing bacterium as 'Candidatus Nitrotoga arctica'.
针对低温下具有活性的亚硝酸盐氧化细菌的鉴定，对西伯利亚北极地区受永久冻土影响的土壤进行了研究。对在4℃、10℃和17℃下培养的富集培养物的脂肪酸谱分析显示，其模式不同于已知的亚硝酸盐氧化菌，但与β-变形菌纲的脂肪酸谱相似。对在10℃下培养的两种富集培养物进行电子显微镜观察，发现普遍存在具有明显超微结构的细胞。16S rRNA基因的序列分析将这些微生物归为β-变形菌纲中一个迄今未培养的类群，与之亲缘关系最近的已分类描述微生物是铁锈盖菌属。结果表明，在多边形冻原土壤中存在一种新型的化能自养亚硝酸盐氧化细菌属，并且可以在高达17℃的低温下富集。之前在活性污泥等中温生境中报道过具有高度序列相似性的克隆序列，因此表明该分类单元参与了非北极生境中的亚硝酸盐氧化。所提供的培养物将为将硝化作用与中等生境中未鉴定的环境克隆相关联提供机会，并深入了解冷适应机制。我们建议将这种新型亚硝酸盐氧化细菌临时分类为“嗜冷亚硝化螺菌属（暂定名）”。
