Department of Earth, Environmental and Life Sciences (DiSTAV), University of Genoa, Genoa, Italy.
National Biodiversity Future Center (NBFC), Palermo, Italy.
Environ Microbiol Rep. 2024 Oct;16(5):e13315. doi: 10.1111/1758-2229.13315.
Blue holes are vertical water-filled openings in carbonate rock that exhibit complex morphology, ecology, and water chemistry. In this study, macroscopic microbial mat structures found in complete anoxic conditions in the Faanu Mudugau Blue Hole (Maldives) were studied by metagenomic methods. Such communities have likely been evolutionary isolated from the surrounding marine environment for more than 10,000 years since the Blue Hole formation during the last Ice Age. A total of 48 high-quality metagenome-assembled genomes (MAGs) were recovered, predominantly composed of the phyla Chloroflexota, Proteobacteria and Desulfobacterota. None of these MAGs have been classified to species level (<95% ANI), suggesting the discovery of several new microbial taxa. In particular, MAGs belonging to novel bacterial genera within the order Dehalococcoidales accounted for 20% of the macroscopic mat community. Genome-resolved metabolic analysis of this dominant microbial fraction revealed a mixotrophic lifestyle based on energy conservation via fermentation, hydrogen metabolism and anaerobic CO fixation through the Wood-Ljungdahl pathway. Interestingly, these bacteria showed a high proportion of ancestral genes in their genomes providing intriguing perspectives on mechanisms driving microbial evolution in this peculiar environment. Overall, our results provide new knowledge for understanding microbial life under extreme conditions in blue hole environments.
蓝洞是碳酸盐岩中垂直的充水开口，具有复杂的形态、生态和水化学特征。在这项研究中，通过宏基因组学方法研究了马尔代夫法努穆杜高斯蓝洞（Faanu Mudugau Blue Hole）完全缺氧条件下发现的宏观微生物垫结构。自上一个冰河时代蓝洞形成以来，这些群落可能已经与周围的海洋环境隔离了超过 10000 年，从而发生了进化。总共回收了 48 个高质量的宏基因组组装基因组（MAG），主要由绿弯菌门、变形菌门和脱硫菌门组成。这些 MAG 均未被分类到种水平（<95%的 ANI），这表明发现了几种新的微生物类群。特别是，属于 Dehalococcoidales 目新型细菌属的 MAG 占宏观微生物垫群落的 20%。对这种主要微生物类群的基因组解析代谢分析表明，它们基于发酵、氢代谢和通过 Wood-Ljungdahl 途径进行厌氧 CO 固定来进行混合营养生活方式。有趣的是，这些细菌在其基因组中显示出大量的祖先基因，这为研究在这种特殊环境中驱动微生物进化的机制提供了有趣的视角。总的来说，我们的研究结果为理解蓝洞环境中极端条件下的微生物生命提供了新的知识。
