CONICET | Buscador de Institutos y Recursos Humanos

E. coli persistence in urban watersheds is a challenge to microbial pollution management and a matter of sanitary concern. To explore the ecological processes influencing the spatial patterns of E. coli, we analyzed its abundance and intraspecific phylogenetic structure in water samples of a stream network with heterogeneous infrastructure and environmental conditions. E. coli was detected in a wide range of abundance across the watershed (3-10,700 cfu/ml) and mean relative frequency for each phylogenetic group was of 64% for A, 16% for B1, 10% for D, 5% for F/G, 3% for E and 2% for B2. A variance partition analysis explained mostly its abundance by spatially structured environmental and infrastructure variables, such as macrophyte cover, dissolved inorganic nitrogen and sewerage cover. E. coli abundance also correlated negatively with phylogroup richness and evenness. This fact, coupled with the prevalence of phylogroups A and B1 mainly in less disturbed sites, suggests the existence of a competitive exclusion effect operating among these conditions. Instead, low-frequent phylogroups were associated with higher ecological disturbances, related mostly to simplified habitats with higher drainage infrastructure and septic tanks, which added to the positive relationship between phylogroup richness and evenness might indicate a counterbalancing effect of facilitated dispersal against the former process. Nutrients levels also contributed to explaining phylogroups distribution. Present results have relevance for understanding the distinct ecological processes on the patterns of E. coli populations, as well as for the management of faecal pollution in urban settings.