Community structure of Anaeromyxobacter in Fe(III) reducing enriched cultures of paddy soils

Purpose: Anaeromyxobacter is a typical representative genus of dissimilatory metal-reducing microbes. However, the community structure and metabolic function of Anaeromyxobacter have rarely been reported because of the limited number of Anaeromyxobacter isolations. Therefore, this study aimed to investigate the community structure and succession of Anaeromyxobacter in a Fe(III)-reducing enriched culture of paddy soils. Materials and methods: A 40-day anaerobic incubation of paddy soils enriched with ferrihydrite and goethite was conducted to investigate the response of the community structure and succession of Anaeromyxobacter to iron oxide addition. Results and discussion: The dominant Anaeromyxobacter in paddy soils were potentially capable of Fe(III) reduction. Ferrihydrite enrichment increased the absolute abundance of Anaeromyxobacter by 0.01 × 10 to 3.2 × 10 copies g soil, while goethite enrichment increased the absolute abundance of Anaeromyxobacter by 0.004 × 10 to 1.8 × 10 copies g soil. Iron oxide enrichment significantly influenced the richness of Anaeromyxobacter during the later stages of incubation but had a negligible influence on the evenness. Nonetheless, Fe(II) accumulation was stimulated by ferrihydrite enrichment after paddy soil was incubated for 5 days, whereas goethite had a negligible effect on Fe(II) accumulation. Redundancy analysis revealed that Anaeromyxobacter community succession was closely correlated with the processes of Fe(III) reduction. Conclusions: Exogenous ferrihydrite addition showed a greater influence than goethite on the Anaeromyxobacter community during anaerobic incubation of paddy soils. The difference in inherent amorphous iron oxide content in paddy soils was also decisive in the distinct community structure and succession of Anaeromyxobacter in paddy soils.