Coalescence of bacterial groups originating from urban runoffs and artificial infiltration systems among aquifer microbiomes

Abstract

Abstract. The invasion of aquifer microbial communities by aboveground microorganisms, a phenomenon known as community coalescence, is likely to be exacerbated in groundwaters fed by stormwater infiltration systems (SISs). Here, the incidence of this increased connectivity with upslope soils and impermeabilized surfaces was assessed through a meta-analysis of 16S rRNA gene libraries. Specifically, DNA sequences encoding 16S rRNA V5-V6 regions from free-living and attached aquifer bacteria (i.e., water and biofilm samples) were analysed upstream and downstream of a SIS and compared with those from bacterial communities from watershed runoffs and surface sediments from the SIS detention and infiltration basins. Significant bacterial transfers were inferred by the SourceTracker Bayesian approach, with 23 % to 57 % of the aquifer bacterial biofilms being composed of taxa from aboveground sediments and urban runoffs. Sediments from the detention basin were found more significant contributors of taxa involved in the buildup of these biofilms than soils from the infiltration basin. Inferred taxa among the coalesced biofilm community were predicted to be high in hydrocarbon degraders such as Sphingobium and Nocardia. The 16S rRNA-based bacterial community structure of the downstream-SIS aquifer waters showed lower coalescence with aboveground taxa (8 % to 38 %) than those of biofilms and higher numbers of taxa predicted to be involved in the N and S cycles. A DNA marker named tpm enabled the tracking of bacterial species from 24 genera including Pseudomonas, Aeromonas and Xanthomonas, among these communities. Several tpm sequence types were found to be shared between the aboveground and aquifer samples. Reads related to Pseudomonas were allocated to 50 species, of which 16 were found in the aquifer samples. Several of these aquifer species were found to be involved in denitrification but also hydrocarbon degradation (P. aeruginosa, P. putida and P. fluorescens). Some tpm sequence types allocated to P. umsongensis and P. chengduensis were found to be enriched among the tpm-harbouring bacteria, respectively, of the aquifer biofilms and waters. Reads related to Aeromonas were allocated to 11 species, but only those from A. caviae were recovered aboveground and in the aquifer samples. Some tpm sequence types of the X. axonopodis phytopathogen were recorded in higher proportions among the tpm-harbouring bacteria of the aquifer waters than in the aboveground samples. A significant coalescence of microbial communities from an urban watershed with those of an aquifer was thus observed, and recent aquifer biofilms were found to be significantly colonized by runoff-opportunistic taxa able to use urban C sources from aboveground compartments.

Aquifer recharge by stormwater infiltration basins: Hydrological and vadose zone characteristics control the impacts of basins on groundwater chemistry and microbiology

“…Based on these conclusions, we can make recommendations about the implementation of infiltration basins in urban areas for stormwater management to limit the impact of SIS on groundwater ecosystems. Indeed, SIS with thick vadose zones and long water transit times from surface to groundwater should be favored to reduce the contamination of groundwater with nutrients supplied with stormwater runoff and their resulting effect on microbial growth in groundwater that could be associated with the presence of pathogenic bacteria (Colin et al 2020). The installation of a homogeneous sediment layer of lower permeability than the surrounding soil at the bottom of the infiltration basin could be also an option to increase the retention time of infiltrated stormwater in the soil and the vadose zone, favoring water purification processes and then groundwater quality protection.…”

“…The practices, based on stormwater infiltration systems (SIS) like infiltration basins, were mainly hydrologically-designed with the main aim to ensure the rapid infiltration of water drained from a given catchment area during stormwater rainfalls (Grebel et al, 2013). However, infiltrated urban stormwater can be highly contaminated with heavy metals, hydrocarbons, pathogens, organic matter and nutrients (Pitt et al, 1999;Grebel et al, 2013;Gasperi et al, 2014;Mermillod-Blondin et al 2015;Colin et al, 2020) which can constitute a risk of pollution for receiving groundwater ecosystems. Therefore, assessing the environmental performance of stormwater infiltration systems is crucial for groundwater resource protection.…”

Spatio-temporal variations in chemical pollutants found among urban deposits match changes in thiopurine S-methyltransferase-harboring bacteria tracked by the tpm metabarcoding approach

“…DNAs were quantified using a nanodrop UV-Vis Spectrophotometer. DNA extracts were visualized as indicated in Colin et al (2020). DNAs were kept at -80°C.…”

“…6-MP and the related azathioprine are commonly used to treat leukemia, rheumatic diseases, inflammatory bowel diseases, and to favor solid organ transplantations (Coussement et al, 2016;Ford and Berg, 2010). TPMTs were found distributed among about 150 bacterial genera mainly allocated to the γ-proteobacteria such as the Pseudomonas and Aeromonas (Cournoyer et al, 1998;Colin et al, 2020). The tpm gene has highly conserved DNA boxes that were found to delineate highly informative sequences in terms of phylogenetic and taxonomic inferences (Favre-Bonte et al, 2005;Favre-Bonté et al, 2006).…”