Colonization of Paracoccus sp QCT6 and Enhancement of Metribuzin Degradation in Maize Rhizosphere Soil

Strain QCT6, capable of degrading metribuzin, was isolated from metribuzin-contaminated soil. The isolate was identified as Paracoccus sp. according to its physiological characteristics, biochemical tests, and 16S rRNA gene phylogenetic analysis. In liquid culture, 86.4% of 50 mg/L metribuzin was removed by strain QCT6 after incubation for 7 days. The product of metribuzin degradation by QCT6 was identified as deamino-metribuzin, which has reduced phytotoxicity on the growth of maize. After being marked with the gfp gene, the colonization and distribution of gfp-tagged QCT6 were directly observed with a confocal laser scanning microscope. The QCT6 strain showed good colonization ability on maize roots and was maintained for at least 20 days in rhizosphere soil. After root irrigation with gfp-tagged QCT6, 75.7% of 15 mg/L metribuzin was removed from the maize rhizosphere soil. This metribuzin-degrading strain QCT6 has strong potential applications for in situ bioremediation of soil contaminated with metribuzin.