Hydrogen-limited growth of hyperthermophilic methanogens at deep-sea hydrothermal vents
Hydrogen-limited growth of hyperthermophilic methanogens at deep-sea hydrothermal vents
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DOI：
10.1073/pnas.1206632109
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发表时间：
2012-08-21
影响因子：
11.1
通讯作者：
Holden, James F.
中科院分区：
文献类型：
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作者：
Eecke, Helene C. Ver;Butterfield, David A.;Holden, James F.
热液喷口的微生物生产力是深海中发现的最高的微生物之一，但对喷口微生物的生长和新陈代谢缺乏限制。我们使用培养、分子和地球化学工具的组合来验证纯培养H-2在来自东北太平洋轴向火山和奋进段的低温热液中高温甲烷生成的阈值测量。两株产自Axial和Janaschii的甲烷球菌在不同H-2浓度的生物反应器中生长时，表现出相似的Monod生长动力学。它们的H-2半饱和值为66亩M，生长停止在17-23亩MH2以下，比先前预测的低10倍。相比之下，液体中测量的H-2和CH4浓度表明，Axial公司普遍有足够的H-2生长，但Endeavour公司没有足够的H-2生长。根据培养和MCRA/MRTA分析，从Axial(标记113)的一个喷口流出的液体具有异常高的CH4浓度，并含有不同热类别的甲烷菌。在奋进号上，根据培养和分子筛查，在流体样本中基本上检测不到甲烷菌，尽管极端嗜热异养菌的丰度相对较高。在存在的情况下，甲烷球菌基因是恢复的主要MCRA/MRTA序列，占整个古菌群落的0.2-6%。现场和共培养的数据表明，H-2的限制可以通过H-2与极端嗜热的异养生物的结合而部分改善。这些数据支持我们估计的喷口高温产甲烷的H-2阈值，并突出了实验室和现场测量相结合的必要性，以限制深海微生物分布和生物地球化学影响。
Microbial productivity at hydrothermal vents is among the highest found anywhere in the deep ocean, but constraints on microbial growth and metabolism at vents are lacking. We used a combination of cultivation, molecular, and geochemical tools to verify pure culture H-2 threshold measurements for hyperthermophilic methanogenesis in low-temperature hydrothermal fluids from Axial Volcano and Endeavour Segment in the northeastern Pacific Ocean. Two Methanocaldococcus strains from Axial and Methanocaldococcus jannaschii showed similar Monod growth kinetics when grown in a bioreactor at varying H-2 concentrations. Their H-2 half-saturation value was 66 mu M, and growth ceased below 17-23 mu MH2, 10-fold lower than previously predicted. By comparison, measured H-2 and CH4 concentrations in fluids suggest that there was generally sufficient H-2 for Methanocaldococcus growth at Axial but not at Endeavour. Fluids from one vent at Axial (Marker 113) had anomalously high CH4 concentrations and contained various thermal classes of methanogens based on cultivation and mcrA/mrtA analyses. At Endeavour, methanogens were largely undetectable in fluid samples based on cultivation and molecular screens, although abundances of hyperthermophilic heterotrophs were relatively high. Where present, Methanocaldococcus genes were the predominant mcrA/mrtA sequences recovered and comprised similar to 0.2-6% of the total archaeal community. Field and coculture data suggest that H-2 limitation may be partly ameliorated by H-2 syntrophy with hyperthermophilic heterotrophs. These data support our estimated H-2 threshold for hyperthermophilic methanogenesis at vents and highlight the need for coupled laboratory and field measurements to constrain microbial distribution and biogeochemical impacts in the deep sea.