Bacterial signatures of anthropogenic pressures in a high-mountain river: a One Health study using full-length 16S profiling

Abstract

<title>Abstract</title> Anthropogenic pressures can reshape riverine microbiomes, with implications for water quality and One Health surveillance. Here, we profiled the bacterial composition, diversity, and 16S-based predicted functional potential across five sites along an anthropogenic pressure gradient in a high-mountain Andean system (Chicamocha River, Boyacá, Colombia), influenced by wastewater discharge, thermoelectric cooling, and agro-livestock and municipal activities. Full-length 16S rRNA gene sequencing (PacBio HiFi) generated 737,344 high-quality reads and 5,036 Amplicon Sequence Variant (ASVs). Community composition differed significantly among sites, characterized by high β-diversity and a notable association between ammonium levels and community structure. The phyla <italic>Pseudomonadota</italic> and <italic>Bacteroidota</italic> dominated most sites, whereas the wastewater outfall was enriched in phyla <italic>Bacillota</italic> and <italic>Campylobacterota</italic> (genus <italic>Arcobacter</italic> ). The cooling pond site showed enrichment of genus <italic>Sphingorhabdus</italic> , genus <italic>Flavobacterium</italic> was most abundant at agro-livestock influenced sites, and the genera <italic>Limnohabitans/Polynucleobacter</italic> dominated downstream oxygen-rich, low-nutrient reaches. 16S-based functional inference suggested site-specific metabolic profiles; the wastewater treatment plant outfall showed higher predicted representation of pathways associated with aromatic/heterocyclic compound degradation and predicted functional categories linked to motility, membrane transport, and antimicrobial resistance, whereas downstream sites showed predicted enrichment of xenobiotic-biodegradation pathways. Together, these data provide a high-resolution baseline for an under-sampled high-mountain urban river and support the utility of full-length 16S rRNA profiling for molecular surveillance to inform effluent management.