Segawa Takahiro, Ishii Satoshi, Ohte Nobuhito, Akiyoshi Ayumi, Yamada Akinori, Maruyama Fumito, Li Zhongqin, Hongoh Yuichi, Takeuchi Nozomu
National Institute of Polar Research, Tokyo, Japan; Transdisciplinary Research Integration Center, Tokyo, Japan.
Environ Microbiol. 2014 Oct;16(10):3250-62. doi: 10.1111/1462-2920.12543. Epub 2014 Jul 15.
Cryoconites are microbial aggregates commonly found on glacier surfaces where they tend to take spherical, granular forms. While it has been postulated that the microbes in cryoconite granules play an important role in glacier ecosystems, information on their community structure is still limited, and their functions remain unclear. Here, we present evidence for the occurrence of nitrogen cycling in cryoconite granules on a glacier in Central Asia. We detected marker genes for nitrogen fixation, nitrification and denitrification in cryoconite granules by digital polymerase chain reaction (PCR), while digital reverse transcription PCR analysis revealed that only marker genes for nitrification and denitrification were abundantly transcribed. Analysis of isotope ratios also indicated the occurrence of nitrification; nitrate in the meltwater on the glacier surface was of biological origin, while nitrate in the snow was of atmospheric origin. The predominant nitrifiers on this glacier belonged to the order Nitrosomonadales, as suggested by amoA sequences and 16S ribosomal RNA pyrosequencing analysis. Our results suggest that the intense carbon and nitrogen cycles by nitrifiers, denitrifiers and cyanobacteria support abundant and active microbes on the Asian glacier.
冰尘粒是常见于冰川表面的微生物聚集体，它们往往呈球形、颗粒状。虽然据推测冰尘粒中的微生物在冰川生态系统中发挥着重要作用，但关于它们群落结构的信息仍然有限，其功能也尚不清楚。在此，我们提供了中亚某冰川上冰尘粒中存在氮循环的证据。我们通过数字聚合酶链反应（PCR）在冰尘粒中检测到了固氮、硝化和反硝化的标记基因，而数字逆转录PCR分析表明，只有硝化和反硝化的标记基因被大量转录。同位素比率分析也表明发生了硝化作用；冰川表面融水中的硝酸盐是生物源的，而雪中的硝酸盐是大气源的。如氨单加氧酶基因（amoA）序列和16S核糖体RNA焦磷酸测序分析所示，该冰川上占主导地位的硝化细菌属于亚硝化单胞菌目。我们的结果表明，硝化细菌、反硝化细菌和蓝细菌强烈的碳和氮循环支持了亚洲冰川上丰富且活跃的微生物。
