Complete mineralisation of dimethylformamide by Ochrobactrum sp. DGVK1 isolated from the soil samples collected from the coalmine leftovers

Abstract

A bacterial strain DGVK1 capable of using N,N-dimethylformamide (DMF) as sole source of carbon and nitrogen was isolated from the soil samples collected from the coalmine leftovers. The molecular phylogram generated using the complete sequence of 16S rDNA of the strain DGVK1 showed close links to the bacteria grouped under Brucellaceae family that belongs to alphaproteobacteria class. Specifically, the 16S rDNA sequence of strain DGVK1 has shown 97% similarity to Ochrobactrum anthropi LMG 3331 (D12794). This bacterium has also shown impressive growth on dimethylamine, methylamine, formaldehyde and formate that are considered to be the prominent catabolic intermediates of DMF. DMF degradation has led to the accumulation of ammonia and dimethylamine contributing to the increase of pH of the medium. The DMF-grown resting cells of Ochrobactrum sp. DGVK1 have also contributed for the release of ammonia when resting cell suspension was added to phosphate buffer containing DMF. Similar experiments done with the glucose-grown cultures have not produced ammonia and thus indicating the inducible nature of DMF-degrading enzymes in Ochrobactrum sp. DGVK1. Further, dimethylformamidase, dimethylamine dehydrogenase and methylamine dehydrogenase, the key enzymes involved in the degradation of DMF, were assayed, and the activities of these enzymes were found only in DMF-grown cultures further confirming the inducible nature of the DMF degradation. Based on these results, DMF degradation pathway found in Ochrobactrum sp. DGVK1 has been proposed.