Degradation of Sulfadiazine by Microbacterium lacus Strain SDZm4, Isolated from Lysimeters Previously Manured with Slurry from Sulfadiazine-Medicated Pigs

摘要

Sulfadiazine (SDZ)-degrading bacterial cultures were enriched from the topsoil layer of lysimeters that were formerly treated with manure from pigs medicated with ~(14)C-labeled SDZ. The loss of about 35% of the applied radioactivity after an incubation period of 3 years was attributed to CO_(2) release due to mineralization processes in the lysimeters. Microcosm experiments with moist soil and soil slurries originating from these lysimeters confirmed the presumed mineralization potential, and an SDZ-degrading bacterium was isolated. It was identified as Microbacterium lacus , denoted strain SDZm4. During degradation studies with M. lacus strain SDZm4 using pyrimidine-ring labeled SDZ, SDZ disappeared completely but no ~(14)CO_(2) was released during 10 days of incubation. The entire applied radioactivity (AR) remained in solution and could be assigned to 2-aminopyrimidine. In contrast, for parallel incubations but with phenyl ring-labeled SDZ, 56% of the AR was released as ~(14)CO_(2), 16% was linked to biomass, and 21% remained as dissolved, not yet identified ~(14)C. Thus, it was shown that M. lacus extensively mineralized and partly assimilated the phenyl moiety of the SDZ molecule while forming equimolar amounts of 2-aminopyrimidine. This partial degradation might be an important step in the complete mineralization of SDZ by soil microorganisms.