Nitrate removal by a novel autotrophic denitrifier (Microbacterium sp.) using Fe(II) as electron donor

A novel denitrifying bacterium was isolated using bicarbonate as the sole carbon source in a defined medium. Strain W3 was isolated from deep sediments of East Lake (Wuhan, China). In this study, analysis of 16S rRNA genes showed that strain W3 was affiliated with Microbacterium sp. When using Fe2+ as the only electron donor, this strain could convert 88.6 % of NO3 (-)-N to N-2, corresponding to an Fe2+ oxidation rate of 80 %. Meanwhile, neither NO2 (-)-N nor NH4 (+)-N was accumulated after the experiment. In similar experiments with Fe(II)-EDTA, cell encrustations did not occur and supplementary substrates were consumed. The accumulated NO2 (-)-N was below 2.5 mg L-1. In addition, PCR revealed five kinds of key denitrifying genes: narG, napA, nirS, norB and nosZ. These results indicated that strain W3 could be used as an alternative autotrophic denitrifier for the treatment of groundwater and low C/N ratio wastewater.