Department of Botany, Stockholm University, SE-10691 Stockholm, Sweden Department of Molecular Genetics and Microbiology, Faculty of Biological Sciences, Pontifícia Universidad Católica de Chile, Alameda 340, Casilla 114-D, C.P. 651 3677, Santiago, Chile Departament de Biologia Marina i Oceanografia, Institut de Ciències del Mar, CSIC, Passeig Marítim de la Barceloneta, 37-49, E-08003 Barcelona, Spain Department of Systems Ecology, Stockholm University, SE-10691 Stockholm, Sweden.
Environ Microbiol Rep. 2012 Jun;4(3):360-6. doi: 10.1111/j.1758-2229.2012.00343.x. Epub 2012 Apr 12.
Although cyanobacterial diazotrophs are common in Arctic terrestrial and freshwater habitats, they have been assumed to be absent from Arctic marine habitats. We report here a high diversity of cyanobacterial nifH genes in Fram Strait and the Greenland Sea. The nifH gene encodes the iron protein of the nitrogenase enzyme complex, which is essential for biological N2 fixation. Using primers specific for nifH genes we uncovered communities of autotrophic and heterotrophic bacteria in sea ice brine and seawater between latitudes 65 and 81°N. Cyanobacteria (Oscillatoriales and Chroococcales) with known marine planktonic and benthic distributions were distinguished, alongside a mix of metabolically versatile eubacteria (nifH Clusters I and III). Using primers selective for cyanobacterial nifH genes we identified filamentous non-heterocystous Trichodesmium-like and LPP (Leptolyngbya, Phormidium and Plectonema)-like Oscillatoriales, as well as Cyanothece-like Chroococcales in a brine sample from 81°N. The occurrence of Trichodesmium-like cyanobacteria was further confirmed by sequences of the hetR gene of Trichodesmium. Microscopic examinations confirmed the presence of viable filamentous and unicellular cyanobacteria. Our results reveal the potential for microbial N2 fixation in the Arctic seas. However, it is still left to determine if these genes are also metabolically active before any biogeochemical importance of diazotrophy in the polar oceans can be assessed.
尽管蓝细菌固氮生物在北极陆地和淡水生境中很常见，但人们一直认为它们不存在于北极海洋生境中。我们在此报告在弗拉姆海峡和格陵兰海发现了丰富多样的蓝细菌 nifH 基因。nifH 基因编码固氮酶复合物的铁蛋白，对生物固氮至关重要。使用针对 nifH 基因的特异性引物，我们在北纬 65 度至 81 度之间的海冰盐水和海水中发现了自养和异养细菌群落。我们区分了具有已知海洋浮游生物和底栖分布的蓝细菌（Oscillatoriales 和 Chroococcales），以及代谢多功能真细菌（nifH 聚类 I 和 III）。使用针对蓝细菌 nifH 基因的引物，我们在 81°N 的盐水样本中鉴定出了丝状非异形胞的类似 Trichodesmium 和 LPP（Leptolyngbya、Phormidium 和 Plectonema）的 Oscillatoriales，以及类似 Cyanothece 的 Chroococcales。在 Trichodesmium 中 hetR 基因的序列进一步证实了类似 Trichodesmium 的蓝细菌的存在。显微镜检查证实了有活力的丝状和单细胞蓝细菌的存在。我们的研究结果表明，在北极海域存在微生物固氮的潜力。然而，在评估极地海洋中固氮作用的生物地球化学重要性之前，还需要确定这些基因是否也具有代谢活性。
