Schaefer J K, Kronberg R-M, Morel F M M, Skyllberg U
Environ Microbiol Rep. 2014 Oct;6(5):441-7. doi: 10.1111/1758-2229.12136.
The corrinoid protein, HgcA has been shown to be essential for Hg methylation in anaerobic bacteria. We investigated the diversity of hgcA from temperate and tropical wetland soils where Hg methylation is demonstrated. Sequences obtained from both environments clustered with those from the δ-Proteobacteria, Chloroflexi and Methanomicrobia with significant overlap in hgcA phylogeny between libraries. Clear differences in hgcA distribution were observed between two highly contrasting sites within a tropical wetland in Everglades National Park, USA. hgcA sequences obtained from the northern site clustered primarily with those of methanogens, while sequences from the estuarine site clustered primarily with sulphate-reducing bacteria and syntrophs in the δ-Proteobacteria. Libraries obtained from soils collected from a temperate swamp in Sweden were dominated by hgcA sequences within the δ-Proteobacteria with hgcA sequences clustering primarily with iron reducers in the upstream portion of the swamp and with sulphate reducers in the downstream portion of the swamp. Interestingly, enrichments prepared from the lower portion of this temperate wetland contained a high abundance of hgcA sequences clustering with methanogens. This first report on hgcA diversity in environmental samples suggests a role in Hg methylation for various phenotypic groups in different portions of wetlands.
类咕啉蛋白HgcA已被证明对厌氧细菌中的汞甲基化至关重要。我们调查了来自温带和热带湿地土壤中hgcA的多样性，这些湿地土壤中已证实存在汞甲基化现象。从这两种环境中获得的序列与来自δ-变形菌门、绿弯菌门和甲烷微菌目的序列聚类，文库之间hgcA系统发育存在显著重叠。在美国大沼泽地国家公园的一个热带湿地内的两个形成强烈对比的地点之间，观察到hgcA分布存在明显差异。从北部地点获得的hgcA序列主要与产甲烷菌的序列聚类，而从河口地点获得的序列主要与δ-变形菌门中的硫酸盐还原菌和互营菌聚类。从瑞典一个温带沼泽地采集的土壤中获得的文库中，δ-变形菌门内的hgcA序列占主导，hgcA序列主要在上游部分与铁还原菌聚类，在下游部分与硫酸盐还原菌聚类。有趣的是，从这个温带湿地较低部分制备的富集培养物中含有大量与产甲烷菌聚类的hgcA序列。这份关于环境样品中hgcA多样性的首次报告表明，湿地不同部分的各种表型群体在汞甲基化过程中发挥了作用。
