Cyanobacterial life at low O2: community genomics and function reveal metabolic versatility and extremely low diversity in a Great Lakes sinkhole mat
Cyanobacterial life at low O2: community genomics and function reveal metabolic versatility and extremely low diversity in a Great Lakes sinkhole mat
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低氧气条件下的蓝藻生命：群落基因组学和功能揭示了五大湖天坑垫的代谢多样性和极低的多样性
DOI：
10.1111/j.1472-4669.2012.00322.x
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发表时间：
2012
期刊：
影响因子：
3.7
通讯作者：
Gregory J. Dick
中科院分区：
文献类型：
--
作者：
A. A. Voorhies;Bopi Biddanda;S. Kendall;Sunit Jain;Daniel N. Marcus;S. Nold;Nathan D. Sheldon;Gregory J. Dick
蓝藻是众所周知的地球氧化的媒介。然而，人们对蓝藻群落在低氧条件下繁盛的情况知之甚少，而低氧条件是蓝藻进化史的主要特征。休伦湖中岛沉水池中的微生物垫提供了在这种持续低氧条件下研究蓝藻的机会。在这里，排放地下水富含硫酸盐和低氧支持紫色蓝藻席独特的底栖生态系统。垫层下面是一层碳酸盐，富含方解石和少量白云石。原位底栖生物代谢室显示，这些草席是氧气的净汇，这表明除了氧气光合作用之外，主要的生产机制。事实上，自养生产的14C -碳酸氢盐摄取研究表明，有氧和无氧光合作用和化学合成的贡献是可变的，可能是因为硫化物的供应。这些结果表明存在兼性无氧蓝藻或混合的含氧/无氧类型的蓝藻。霰弹枪宏基因组测序显示，一个极低多样性的草甸群落仅由一种与蓝藻秋季紫藻最密切相关的基因型主导，并对其基本完整的基因组进行了重建。此外，还发现了一种第二基因型的紫堇和几种振荡花的部分基因组。尽管分类简单，但多种蓝藻基因被认为参与硫氧化，表明硫化物生理的多样性。优势的黄貂草基因组反映了在波动的氧化还原条件和光照可用性下的公共生活方式的多用途代谢和生理。总的来说，这项研究为低氧蓝藻垫生态系统提供了基因组和生理学的见解，这些生态系统在地球历史上发挥了重要的地理生物学作用。
Cyanobacteria are renowned as the mediators of Earth’s oxygenation. However, little is known about the cyanobacterial communities that flourished under the low‐O2 conditions that characterized most of their evolutionary history. Microbial mats in the submerged Middle Island Sinkhole of Lake Huron provide opportunities to investigate cyanobacteria under such persistent low‐O2 conditions. Here, venting groundwater rich in sulfate and low in O2 supports a unique benthic ecosystem of purple‐colored cyanobacterial mats. Beneath the mat is a layer of carbonate that is enriched in calcite and to a lesser extent dolomite. In situ benthic metabolism chambers revealed that the mats are net sinks for O2, suggesting primary production mechanisms other than oxygenic photosynthesis. Indeed, 14C‐bicarbonate uptake studies of autotrophic production show variable contributions from oxygenic and anoxygenic photosynthesis and chemosynthesis, presumably because of supply of sulfide. These results suggest the presence of either facultatively anoxygenic cyanobacteria or a mix of oxygenic/anoxygenic types of cyanobacteria. Shotgun metagenomic sequencing revealed a remarkably low‐diversity mat community dominated by just one genotype most closely related to the cyanobacterium Phormidium autumnale, for which an essentially complete genome was reconstructed. Also recovered were partial genomes from a second genotype of Phormidium and several Oscillatoria. Despite the taxonomic simplicity, diverse cyanobacterial genes putatively involved in sulfur oxidation were identified, suggesting a diversity of sulfide physiologies. The dominant Phormidium genome reflects versatile metabolism and physiology that is specialized for a communal lifestyle under fluctuating redox conditions and light availability. Overall, this study provides genomic and physiologic insights into low‐O2 cyanobacterial mat ecosystems that played crucial geobiological roles over long stretches of Earth history.