Properties of free-living and particle-attached potentially pathogenic bacterial communities in a hypereutrophic urban river network.

Pathogenic bacteria are ubiquitously detected in various natural and artificial water systems, posing potential threats to public health and safety. To elucidate the structure of potentially pathogenic bacterial communities and their spatio-temporal patterns, a two-year study examined four contrasting land-use/land-cover types (urban, industrial, agricultural, natural forest) in a hypereutrophic urban river network of eastern China. Three predominant potentially pathogenic species appeared in both the particle-attached (PA) and free-living (FL) bacterial communities: Flavobacterium succinicans, Arcobacter cryaerophilus, and Aeromonas hydrophila. The richness, relative abundances, community complexity and stability of potentially pathogenic bacteria were generally higher in the PA fraction than those in the FL fraction. Moreover, higher concentrations of suspended particles appeared to increase the similarity in potentially pathogenic bacterial community composition between PA and FL assemblages. Redundancy analysis demonstrated that water temperature was the most influential water quality variable shaping the seasonal changes of potentially pathogenic bacterial community. The relative abundance of potentially pathogenic bacterial species in the urban river environment showed marked changes related to seasons, with its relative abundance appreciably higher in the winter dry season (January). Although the assembly mechanisms of potentially pathogenic bacterial communities were more stochastic than deterministic, those in the river surrounded by agricultural land were more deterministic compared to with other land-use/land-cover types. Potentially pathogenic bacterial communities with a high proportion of positive correlations might have weak stability. These findings increase our understanding of potentially pathogenic bacterial community characteristics in hypereutrophic urban river ecosystems and provide valuable insights for environmental and public health management.