水稻土中铁氧化物对产甲烷古菌群落结构的影响

产甲烷菌广泛分布在淹水水稻土等各种厌氧环境中,在全球气候变化、碳循环和能源等领域都发挥着重要的作用。研究发现,厌氧条件下,水稻土中铁氧化物的生物还原会抑制产甲烷菌的甲烷合成作用。然而,目前关于铁氧化物对产甲烷菌群落结构的影响报道较少。通过泥浆厌氧培养实验,向采集的水稻土中添加甲酸盐作为甲烷合成的底物(Control,CK处理),并设置添加水铁矿作为体系中唯一电子受体的处理组(Ferrihydrite,Fh处理)。培养结束后,与CK相比,添加水铁矿显著降低了古菌在总微生物群落中的占比,但对古菌群落的物种多样性和均一度没有显著影响;且两组处理中优势种均为操作分类单元(Operational taxonomic unit,OTU)2056和OTU 911(76%—80%)。这说明碳源相同时,产甲烷菌的群落结构不受铁氧化物的影响。本研究为探索土壤中微生物铁还原与碳循环耦合的分子机制奠定基础。

Effects of iron oxides in paddy soils on methanogens communities

Methanogens are widely distributed in anaerobic environment, such as flooded paddy soils, and are of vital importance in global carbon cycling, climate change and clean energy utilization. Previous studies found that microbial reduction of iron oxides, which are the most abundant oxides in paddy soils, could inhibit methanogenesis as ferric iron acts as a competitive electron acceptor. However, the effects of iron oxides on methanogens communities are less reported. By anaerobic incubation experiments added with formate only (control, CK) and both formate and ferrihydrite (Fh treatment), combined with 16S rRNA gene sequencing technique, we explored the changes of archaea communities induced by iron oxides in flooded paddy soil. Our results showed that compared to CK, adding ferrihydrite significantly reduced the proportion of archaea in total microbial community after incubation. At the operational taxonomic unit (OTU) level, a total of 21 OTUs were found at the end of incubation, 15 of which were detected both in CK and Fh treatments. Meanwhile, the addition of formate induced a lower shannon index and a higher simpson index of archaea community, indicating that the species richness and evenness were reduced. OTU 2056 and OTU 911 were enriched significantly, becoming the dominant and occupying 76%-80% in whole archaea communities, but the relative abundance of other OTUs decreased. However, the addition of ferrihydrite had no significant effect on the alpha diversity (shannon index and simpson index) and dominant strains. By means of phylogenetic tree analysis, OTU 2056 and OTU 911 had a close affinity with Methanobacterium bryantii which has been reported as hydrogenotrophic methanogens that could utilize formate. It thus indicates that iron oxides may only reduce the release of methane by inhibiting the growth of methanogens, but have no selective effect on the strains that act as the key role. This study helps to lay a foundation for exploring the microbial coupling of iron reduction and carbon cycling in soils.