The application of cold-adapted microorganisms in biphenyl biodegradation: Responses and mechanisms to environmental...

For the bioremediation of contaminated sites, the efficiency of bioaugmentation depends on the survival capacity of introduced degradative strains in environmental settings. Many isolated strains exhibit poor activity after field application, primarily due to fluctuating environmental conditions, among which diurnal temperature variation represents a significant contributing factor. In this study, cold-adapted bacteria were implemented for biphenyl degradation under realistic environmental temperature fluctuations. The research employed a simplified isolation approach incorporating the limiting dilution method to isolate 22 biphenyl-degrading strains from four extreme environments: Antarctic soil, Pacific deep-sea sediment, and Qinghai-Tibet Plateau soil/lake sediment. Notably, a Microbacterium strain from deep-sea sediment demonstrated broad temperature adaptability, completely removing 500 mg/L biphenyl within 3 days at both 30 and 15 °C. This strain can also degrade toluene, phenol, and sodium benzoate. Its biphenyl removal efficiency in actual environmental water samples remained unaffected by diurnal temperature cycling. Further analysis revealed its capacity to maintain membrane fluidity at 15 °C and to upregulated the expression of the cold shock protein gene cspA. These results suggest that cold-adapted microorganisms have promising applications in the bioremediation of organic contaminants.