The cyanobacterium Mastigocladus fulfills the nitrogen demand of a terrestrial hot spring microbial mat
The cyanobacterium Mastigocladus fulfills the nitrogen demand of a terrestrial hot spring microbial mat
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DOI：
10.1038/ismej.2015.63
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发表时间：
2015-10-01
期刊：
影响因子：
11
通讯作者：
Diez, Beatriz
中科院分区：
文献类型：
--
作者：
Estrella Alcaman, Maria;Fernandez, Camila;Diez, Beatriz
来自第V亚组（Stigonematales）的蓝细菌是非酸性陆地温泉微生物垫的重要组成部分。尽管它们具有固氮性质（N-2固定剂），但它们对这种极端生态系统中氮循环的影响仍然未知。在这里，我们调查了2009年和2011-2013年期间在Porcelana（北方巴塔哥尼亚，智利）的中性温泉固氮蓝藻的身份和活动。利用16 SrRNA和nifH基因分析了重氮蓝藻的分布和多样性。我们的研究结果表明，优势的异型属Mastigocladus（Stigonematales）沿着整个温度梯度的温泉（69-38摄氏度）。原位固氮酶活性（乙炔还原）、固氮速率（细胞对N-15（2）的摄取）和微生物垫中nifH的转录水平表明，固氮和nifH mRNA表达具有光依赖性。在58 ℃至46 ℃的温度范围内检测到固氮活性，最大日速率为600 nmol C2 H4 cm（-2）/天和94.1 nmol N cm（-2）/天。这些活动模式强烈建议一个heterocystous蓝藻的起源，并揭示了固氮酶活性和nifH基因的表达在昼夜周期的热微生物垫之间的相关性。垫中的N和C固定贡献类似于每年3 g Nm（-2）和每年27 g Cm-2，这表明这些重要的需求完全满足于Porcelana温泉中蓝藻的固氮和光合自养能力。
Cyanobacteria from Subsection V (Stigonematales) are important components of microbial mats in non-acidic terrestrial hot springs. Despite their diazotrophic nature (N-2 fixers), their impact on the nitrogen cycle in such extreme ecosystems remains unknown. Here, we surveyed the identity and activity of diazotrophic cyanobacteria in the neutral hot spring of Porcelana (Northern Patagonia, Chile) during 2009 and 2011-2013. We used 16S rRNA and the nifH gene to analyze the distribution and diversity of diazotrophic cyanobacteria. Our results demonstrate the dominance of the heterocystous genus Mastigocladus (Stigonematales) along the entire temperature gradient of the hot spring (69-38 degrees C). In situ nitrogenase activity (acetylene reduction), nitrogen fixation rates (cellular uptake of N-15(2)) and nifH transcription levels in the microbial mats showed that nitrogen fixation and nifH mRNA expression were light-dependent. Nitrogen fixation activities were detected at temperatures ranging from 58 degrees C to 46 degrees C, with maximum daily rates of 600 nmol C2H4 cm(-2) per day and 94.1 nmol N cm(-2) per day. These activity patterns strongly suggest a heterocystous cyanobacterial origin and reveal a correlation between nitrogenase activity and nifH gene expression during diurnal cycles in thermal microbial mats. N and C fixation in the mats contributed similar to 3 g Nm(-2) per year and 27 g Cm-2 per year, suggesting that these vital demands are fully met by the diazotrophic and photoautotrophic capacities of the cyanobacteria in the Porcelana hot spring.