Time-resolved analysis of a denitrifying bacterial community revealed a core microbiome responsible for the anaerobic degradation of quinoline

Quinoline is biodegradable under anaerobic conditions, but information about the degradation kinetics and the involved microorganisms is scarce. Here, the dynamics of a quinoline-degrading bacterial consortium were studied in anoxic batch cultures containing nitrate. The cultures removed 83.5% of the quinoline during the first 80 hours, which were dominated by denitrification, and then switched to methanogenesis when the nitrogen oxyanions were depleted. Time-resolved community analysis using pyrosequencing revealed that denitrifiying bacteria belonging to the genus Thauera were enriched during the denitrification stage from 12.2% to 38.8% and 50.1% relative abundance in DNA and cDNA libraries, respectively. This suggests that they are key organisms responsible for the initial attack on quinoline. Altogether, 13 different co-abundance groups (CAGs) containing 76 different phylotypes were involved, directly or indirectly, in quinoline degradation. The dynamics of these CAGs show that specific phylotypes were associated with different phases of the degradation. Members of Rhodococcus and Desulfobacterium, as well as Rhodocyclaceae- and Syntrophobacteraceae-related phylotypes, utilized initial metabolites of the quinoline, while the resulting smaller molecules were used by secondary fermenters belonging to Anaerolineae. The concerted action by the different members of this consortium resulted in an almost complete anaerobic mineralization of the quinoline.