Spatio-temporal dynamics of TPMT-harboring bacteria among urban deposits reveal significant shifts in Pseudomonas and Aeromonas populations matching pollutant concentrations

Thiopurine methyltransferase (TPMT) harboring bacteria have been so far mainly associated to freshwater and aquifer environments, and plant and human opportunistic pathogens. TPMT functional inputs contributing at the occurrences of these bacteria among such systems remain to be defined but a few reports indicated a probable role in the detoxification of cellular compounds, metallic trace elements and human drugs through methylation (e. g. Ranjard et al., 2002). Here, the hypotheses that urban sediments and their contents in pollutants explain (1) the organization TPMT-harboring bacterial communities and (2) favour the occurrences of some pathogenic species like P. aeruginosa were investigated. These hypotheses were tested by using the experimental design reported by Marti et al. (2017). An urban industrial catchment (named Mi-Plaine) connected to a stormwater infiltration system (SIS) was used. This catchment is part of a field observatory of urban waters in Lyon named “OTHU” (http://www.graie.org/othu/). This observatory keeps record of all datasets and materials produced from this site, and favors their uses through multi-disciplinary research actions. This work could thus benefit from DNA samples and datasets produced over several years. The OTHU sampling scheme allowed to obtain multiple independent replicates per sampling points of the detention basin (DB) of the selected SIS and its decantation pit, but also of a control point located outside the DB. A large meta-barcoding DNA library of tpm sequences could thus be built for this site, and be compared with physico-chemical and chemical pollutant datasets generated during the same sampling periods. This allowed a first demonstration of significant changes recorded among these bacteria over time matching the accumulation of several pollutants like HAPs and MTEs. Furthermore, the development of a plant cover was found to match with an increase in phytopathogens like P. syringae and Xanthomonas campestris.