Mesorhizobium tamadayense MM3441: A novel methylotroph with a great potential in degrading N,N′-dimethylformamide

The widespread presence of the versatile solvent, N,N'-dimethylformamide (DMF), in industrial wastewaters, and the growing concern over its ecotoxicity necessitate the implementation of an effective remediation technology. Mesorhizobium tamadayense MM3441, isolated from a soil contaminated with polycyclic aromatic hydrocarbons, utilized higher concentrations of DMF as sole carbon and nitrogen source. To our knowledge, the strain MM3441 is the only member of the genus, Mesorhizobium, capable of degrading DMF. This strain, with methylotrophic mode of nutrition, also exhibited resistance to several organic solvents. Optimal growth of the strain was observed at pH 7.0 in the presence of 5000 mg L-1 DMF. The strain removed 95% of 5000 mg L-1 DMF within nine days of incubation. DMF utilization was accompanied by the accumulation of dimethylamine (DMA) and ammonia in the culture medium. Both the resting cell and dimethylformamidase (DMFase) assays provided the circumstantial evidence that DMF degradation by the strain MM3441 proceeds via the typical pathway yielding DMA. However, DMFase expression is not inducible with DMF, suggesting that the enzyme is constitutively expressed. Based on the DMF degradation ability and metabolic flexibility of the strain MM3441, the present study advocates its potential use in bioremediation of the environments contaminated with DMF.