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ISME J:对维生素B12至关重要的新发现

来源:生物谷 2014-09-18 09:04

2014年9月18日 讯 /生物谷BIOON/ --新的研究发现在海洋中一组微生物可能对全球大部分维生素B12的相关产品有影响,并对全球碳循环和气候变化也会产生一定的影响。

虽然在这个星球上维生素B12是大多数生物所需要的重要的分子,但是它仅由一小群相关微生物产出,因为它是如此庞大而复杂。对于人类来说,维生素B12中在维持大脑和神经系统,以及细胞内DNA合成到全身都起着非常重要的作用。

Andew Doxey 教授发现古菌可能是主要维生素B12的生产源。这组来自古菌领域的菌群从未发现与维生素B12合成有关。“我们认为,以维生素B12为基础的化合物的特性可能已经被确定,因此这一发现改变了我们如何思考关于这种重要维生素在全球产出的想法。”Doxey教授说。

研究者使用计算方法通过大量的DNA序列寻找可以制造维生素B12的基因,在海洋和淡水中识别类似的制造者。“因为古菌种在大量的有机生物体内存在,尤其是在海洋环境中,所以在生态系统和新陈代谢中它们对维生素B12的生产影响很大。”Neufeld教授说。维生素B12的实用性可能在于控制浮游生物的生物生产力在海洋中产出的量。浮游植物通过大气层光合作用清除二氧化碳,很像植物的光合作用。因此减少这种大气中温室气体浓度是对全球变暖的最大贡献。

该研究也发现古细菌合成B12基因与在冬季极地海域的海洋深度有关。由此可见古细菌B12可能是深冷海洋环境中其他物种幸存的关键。(生物谷Bioon.com)

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Aquatic metagenomes implicate Thaumarchaeota in global cobalamin production

Andrew C Doxey1, Daniel A Kurtz1, Michael DJ Lynch1, Laura A Sauder1 and Josh D Neufeld1

Cobalamin (vitamin B12) is a complex metabolite and essential cofactor required by many branches of life, including most eukaryotic phytoplankton. Algae and other cobalamin auxotrophs rely on environmental cobalamin supplied from a relatively small set of cobalamin-producing prokaryotic taxa. Although several Bacteria have been implicated in cobalamin biosynthesis and associated with algal symbiosis, the involvement of Archaea in cobalamin production is poorly understood, especially with respect to the Thaumarchaeota. Based on the detection of cobalamin synthesis genes in available thaumarchaeotal genomes, we hypothesized that Thaumarchaeota, which are ubiquitous and abundant in aquatic environments, have an important role in cobalamin biosynthesis within global aquatic ecosystems. To test this hypothesis, we examined cobalamin synthesis genes across sequenced thaumarchaeotal genomes and 430 metagenomes from a diverse range of marine, freshwater and hypersaline environments. Our analysis demonstrates that all available thaumarchaeotal genomes possess cobalamin synthesis genes, predominantly from the anaerobic pathway, suggesting widespread genetic capacity for cobalamin synthesis. Furthermore, although bacterial cobalamin genes dominated most surface marine metagenomes, thaumarchaeotal cobalamin genes dominated metagenomes from polar marine environments, increased with depth in marine water columns, and displayed seasonality, with increased winter abundance observed in time-series datasets (e.g., L4 surface water in the English Channel). Our results also suggest niche partitioning between thaumarchaeotal and cyanobacterial ribosomal and cobalamin synthesis genes across all metagenomic datasets analyzed. These results provide strong evidence for specific biogeographical distributions of thaumarchaeotal cobalamin genes, expanding our understanding of the global biogeochemical roles played by Thaumarchaeota in aquatic environments.

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