Faecal Bacteria Are Governed by Distinct Assembly Processes Within the Bacterioplankton of an Urban Stream Network.

Faecal bacterioplankton in an urban stream network are governed by distinct ecological assembly processes, with dispersal limitation and external inoculum shaping their distribution.

• Why it matters: Understanding how human faecal bacteria persist and disperse in hydrological systems is crucial for managing water quality and public health risks in urban environments.
• What they did: The study analyzed 192 human gut microbiome samples and used source tracking to confirm human origin, then examined assembly processes across the Buenos Aires stream network, focusing on faecal versus non-faecal taxa.
• The result: Faecal taxa showed minimal dispersal limitation (1.8%) and were less affected by hydrological distance, with external inoculum filtering playing a key role, indicating that monitoring single indicators may overlook complex ecological dynamics.