Structure and Activity of Fe(III)-Reducing Microorganism Occurring in Paddy Fields of Thailand

In the saline paddy soils of Thailand, four bacterial consortia (S1, S2, S6, and S8) were isolated in paddy soils and then selected for their abilities and efficiencies to reduced iron oxyhydroxyde (goethite) at different concentration of salt in culture medium. In this study, the effect of salinity on the structure and activities of bacterial consortia involved in iron reduction process were studied at two saline concentrations (0 and 3% NaCl). The results show that the bacterial consortia presented different behaviors in the presence or absence of salt. The bacterial consortia S1 and S2 were not affected by the presence of salt. Bacterial consortium S6 had a higher iron-reducing activity under saline conditions than in a non-saline environment. The iron reducing activity of the bacterial consortium S8 was inhibited by the presence of salt but not fermentation processes. In this rice fields, the presence of diverse halosensitive to slightly halophilic bacterial groups and also of bacteria presenting both fermentative and iron-respiring metabolisms are able to maintain a strong ability in iron-reduction and dissolution under changing saline environmental conditions.