Bacterial community structure associated with oxidation of sulfuric soil material– laboratory experiment. Changes in bacterial community structure during oxidation of sulfidic soil material

Oxidation of sulfidic soil materials by sulfur and iron oxidating bacteria results in acidification and release of metals to the environment. Bacterial taxa or microbial mechanisms associated with the oxidation and environmental risk of the acid sulfate soils are not well understood especially in cold climate conditions. In this study, sulfidic soil material was incubated in laboratory and the oxidation followed by pH measurements and linked to changes in bacterial community structure. To investigate the effect of freezing and freeze-thaw cycles on the oxidation and bacterial communities, samples were treated with three freeze-thaw cycles before incubation at 15°C. The results indicated rapid acidification coupled with shifts in bacterial community structure in the soil microcosms. Oxidation was initially slower in the freeze-thaw treated soils than control soils incubated at 15°C. Different bacterial taxa became dominant in the control and freeze-thaw treated microcosms indicating that differences in the winter time snow and frost conditions may strongly influence the microbial oxidation in acid sulfate soils.