Exploratory characterization of bacterial communities and predicted functional profiles in six water samples from four Colombian Andean lakes using 16S rRNA gene amplicon sequencing

Northern Andean highland lakes support agriculture, water provision, and local livelihoods, but their bacterial communities remain insufficiently characterized. We conducted an exploratory survey of bacterial community composition and predicted functional potential in six water samples from four freshwater lakes in the Eastern Cordillera of Colombia: Fúquene, Tota, Calderona, and Colorado. Five samples collected in 2019 comprised the primary dataset, while a previously published Tota sample collected in December 2018 was reprocessed as a historical reference. Bacterial communities were characterized using 16S rRNA gene amplicon sequencing, and functional profiles were inferred using PICRUSt2. After sequence processing and taxonomic filtering, 3153 amplicon sequence variants were retained. Actinobacteria, Proteobacteria, Bacteroidetes, Cyanobacteria, and Verrucomicrobia were the predominant bacterial phyla. Coverage-standardized richness and diversity varied descriptively among samples, with Colorado showing the lowest estimated ASV richness. Taxonomic composition and Bray–Curtis dissimilarities also varied among samples, reflecting differences in dominant bacterial groups. Mycobacterium -assigned ASVs were detected in Fúquene and Tota, Leptospira -assigned ASVs occurred in these same lakes at relative abundances of 0.01 %–0.36 %, and Legionella -assigned ASVs occurred in all six samples at 0.11 %–4.60 %. These genus-level assignments do not establish pathogenic species, viability, transmission, or risks to aquatic animals or humans. PICRUSt2 predicted variation in functional profiles, including pathways associated with naphthalene degradation, bacterial chemotaxis, biofilm formation, bacterial secretion systems, and pyrimidine and folate metabolism. Bray–Curtis ordination of predicted pathway profiles showed sample-level separation, and weighted NSTI values ranged from 0.160 to 0.181. These predictions represent inferred genomic potential rather than direct evidence of gene presence, expression, or metabolic activity. Because sampling was limited and unbalanced and lacked concurrent environmental measurements, the observed patterns cannot be attributed to specific environmental drivers. This study provides an initial descriptive baseline for bacterial communities in four Colombian Andean lakes and identifies patterns for evaluation through replicated sampling, physicochemical measurements, metagenomics, and targeted validation.