Constitutive mineralization of low concentrations of the herbicide linuron by a Variovorax sp strain

The mineralization of the herbicide linuron at concentrations of μg and mg L^-1 was studied in liquid batch experiments with Variovorax sp. strain SRS16. The strain was highly efficient at mineralizing a range of linuron concentrations (0.002-10 mg L^-1) with 20-60% of the added ¹⁴C-ring-labeled linuron metabolized to ¹⁴CO₂ within hours to days depending on the initial linuron concentration and incubation period. At mg L^-1 linuron concentrations the mineralization activity by SRS16 was inducible and a shift to constitutive mineralization activity was apparent with a reduction in the linuron concentration to μg L^-1 levels. This study revealed that strain SRS16 is a promising candidate for bioaugmentation of water or soil resources contaminated with low linuron concentrations.