A novel isolated Terrabacter-like bacterium can mineralize 2-aminopyrimidine, the principal metabolite of microbial sulfadiazine degradation

Abstract

Recently we showed that during the degradation of sulfadiazine (SDZ) by Microbacterium lacus strain SDZm4 the principal metabolite 2-aminopyrimidine (2-AP) accumulated to the same molar amount in the culture as SDZ disappeared (Tappe et al. Appl Environ Microbiol 79:2572–2577, 2013). Although 2-AP is considered a recalcitrant agent, long-term lysimeter experiments with ¹⁴C-pyrimidine labeled SDZ ([¹⁴C]_pyrSDZ) provided indications for substantial degradation of the pyrimidine moiety of the SDZ molecule. Therefore, we aimed to enrich 2-AP degrading bacteria and isolated a pure culture of a Terrabacter-like bacterium, denoted strain 2APm3. When provided with ¹⁴C-labeled SDZ, M. lacus strain SDZm4 degraded [¹⁴C]_pyrSDZ to [¹⁴C]2-AP. Resting cells of 2APm3 at a concentration of 5 × 10⁶ cells ml⁻¹ degraded 62 µM [¹⁴C]2-AP to below the detection limit (0.6 µM) within 5 days. Disappearance of 2-AP resulted in the production of at least two transformation products (M1 and M2) with M2 being identified as 2-amino-4-hydroxypyrimidine. After 36 days, the transformation products disappeared and 83 % of the applied [¹⁴C]2-AP radioactivity was trapped as ¹⁴CO₂. From this we conclude that a consortium of two species should be able to almost completely degrade SDZ in soils.