Long-Term Atrazine Degradation with Microtube-Encapsulated Pseudomonas sp. Strain ADP

Long-term atrazine degradation was studied with Pseudomonas sp. strain ADP (P. ADP) encapsulated in electrospun microtubes with no addition of external carbon source. Experiments were conducted in consecutive 3-day sequential batches under semisterile and nongrowth conditions over a period of 2.5 years. During the entire period, 95.2% atrazine was degraded on average, with 68.2% nitrogen recovery as ammonium. Only a slight buildup of intermediate (approximately 15-20% cyanuric acid) was observed. Confocal microscopy taken after 6 months showed bacteria colonizing outside the microtubes whose origin came from external contamination. Analysis of the microtube microbial community after 1.5 years revealed a mixed population containing P. ADP along with Chitinophagaceae, Variovorax, and Microbacterium. After 2.5 years, P. ADP was not found in the microtube bacterial population comprising Variovorax, Cupriavidus, Comamonas, Xanthobacter, Microbacterium, and Tsukamurella. Presence of pADP-1 plasmid in the microtube microbial population after 2.5 years indicates horizontal plasmid transfer from the initial P. ADP population to other bacteria. This suggests that gene transfer from a single bacterium, P. ADP, capable of using atrazine as a nitrogen source, but not as the energy source, allowed for the evolution of a mixed culture capable of degrading atrazine and using it both as a nitrogen and energy source. Results from this study show potential benefits of using microtube encapsulation of bacteria for bioremediation of recalcitrant compounds.