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摘要 : SAR11细菌是全球海洋中最丰富的微生物,人们一般认为它们需要氧气才能生长,但SAR11细菌也大量存在于含氧水平低的水域。

 SAR11细菌是全球海洋中最丰富的微生物,人们一般认为它们需要氧气才能生长,但SAR11细菌也大量存在于含氧水平低的水域。Frank Stewart及同事表明, SAR11细菌的一个亚群能在含氧极少的海域繁荣生长,已经适应了低氧区的微氧/厌氧条件,并编码了大量呼吸型硝酸还原酶来执行脱氮的第一步。这些结果重新定义了地球上最丰富的生物群的生态位,表明它们是导致低氧区氮流失的主要因素。


SAR11 bacteria linked to ocean anoxia and nitrogen loss


Bacteria of the SAR11 clade constitute up to one half of all microbial cells in the oxygen-rich surface ocean. SAR11 bacteria are also abundant in oxygen minimum zones (OMZs), wher oxygen falls below detection and anaerobic microbes have vital roles in converting bioavailable nitrogen to N2gas. Anaerobic metabolism has not yet been observed in SAR11, and it remains unknown how these bacteria contribute to OMZ biogeochemical cycling. Here, genomic analysis of single cells from the world’s largest OMZ revealed previously uncharacterized SAR11 lineages with adaptations for life without oxygen, including genes for respiratory nitrate reductases (Nar). SAR11 nar genes were experimentally verified to encode proteins catalysing the nitrite-producing first step of denitrification and constituted ~40% of OMZ nar transcripts, with transcription peaking in the anoxic zone of maximum nitrate reduction activity. These results link SAR11 to pathways of ocean nitrogen loss, redefining the ecological niche of Earth’s most abundant organismal group.

来源: Nature 浏览次数:0


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