Fe-oxidizing bacteria of the family Gallionellaceae are major players in the Fe biogeochemical cycle in freshwater. These bacteria thrive in redox transition zones where they benefit from both high Fe concentrations and microaerobic conditions. We analysed the Gallionellaceae genomic diversity in an artesian hard-rock aquifer where redox transition zones develop (i) in the subsurface, where ancient, reduced groundwater mixes with recent oxygenated groundwater, and (ii) at the surface, where groundwater reaches the open air. A total of 15 new draft genomes of Gallionellaceae representing to 11 candidate genera were recovered from the two redox transition zones. Sulfur oxidation genes were encoded in most genomes while denitrification genes were much less represented. One genus dominated microbial communities belowground and we propose to name it ‘Candidatus Houarnoksidobacter’. The two transition zones were populated by completely different assemblages of Gallionellaceae despite the almost constant upward circulation of groundwater between the two zones. The processes leading to redox transition zones, oxygen diffusion at the surface or groundwater mixing in subsurface, appear to be a major driver of the Gallionellaceae diversity.

中文翻译：

---

基因组重建揭示了表面和亚表面氧化还原过渡带中的金鸡藻的独特组合

Gallionellaceae科的Fe氧化细菌是淡水中Fe生物地球化学循环的主要参与者。这些细菌在氧化还原过渡区壮成长，从高铁浓度和微好氧条件中受益。我们分析了自流硬岩含水​​层中的金鸡藻基因组多样性，该区域的氧化还原过渡带发展为（i）地下，古代的，还原的地下水与最近的含氧地下水混合，（ii）地表的地下水到达露天。总共有15个鸡没食子菌新基因组草图从两个氧化还原过渡区回收了11个候选属。硫氧化基因编码在大多数基因组中，而反硝化基因的表达则少得多。一个属为主的微生物群落地下，我们建议把它命名为“暂定Houarnoksidobacter”。尽管两个地区之间的地下水几乎持续不断地向上循环，但这两个过渡区却由满满的金毛科组成。导致氧化还原过渡区，地表氧气扩散或地下地下水混合的过程似乎是Gallionellaceae多样性的主要驱动力。