Aromatic compound degradation by iron reducing bacteria isolated from irrigated tropical paddy soils

Forty-six candidate phenol/benzoate degrading-iron reducing bacteria were isolated from long-term irrigated tropical paddy soils by enrichment procedures. Pure cultures and some prepared mixed cultures were examined for ferric oxide reduction and phenol/benzoate degradation. All the isolates were iron reducers, but only 56.5% could couple iron reduction to phenol and/or benzoate degradation, as evidenced by depletion of phenol and benzoate after one week incubation. Analysis of degradative capability using Biolog MT plates revealed that most of them could degrade other aromatic compounds such as ferulic acid, vanillic acid, and hydroxybenzoate. Mixed-cultures and soil samples displayed greater capacity for aromatic degradation and iron reduction than pure bacterial isolates, suggesting that these reactions may be coupled via a consortia-based mechanism in paddy soils.