Diversity of isolates performing Fe(III) reduction from paddy soil fed by different organic carbon sources

Abstract

This study examined microbial diversity of Fe(III)-reducing bacteria  isolates in paddy soils amended with ferrihydrite and different organic carbon (C) sources. Results show that Fe(III) reduction rate and Fe(II) accumulation in soil enrichments amended with glucose were the greatest followed by pyruvate, lactate, acetate and control. ARDRA (amplified ribosomal deoxyribonucleic acid restriction analysis) analysis showed 161 Fe(III)-reducing bacteria strains isolated from associated soil enrichment cultures fell into seven groups. Dominant populations in soil enrichments shifted according to amended organic C substrate. Paenibacillus spp. and Clostridum spp. occurred in all soil enrichment cultures. Solibacillus spp. and Lysinibacillus spp. were enriched by acetate, while Bacillus spp. was dominant in pyruvate-amended soil enrichments. Azotobacter spp. was detected in all soil enrichments except those amended with glucose, which were mainly consisted of Pseudomonas spp. Data analysis indicated the highest Fe(III)-reducing bacterial diversity occurring in acetate and lactate-amended soil enrichments, and glucose-amended enrichments  characterized with most predominant species. In summary, this study demonstrates a high diversity of microbial Fe(III)-reducing bacterial  populations and their response to different organic C sources in paddy soils. Their versatile C metabolism plays an important role in Fe-C cycling.

Key words: Microbial iron reduction, organic carbon, Fe(III)-reducing bacteria isolates, paddy soil.