Diversity and Structural Composition of Bacterial Communities in Mineral Springs of the Andean–Amazonian Transition Zone in Northern Peru

Mineral springs in the Andean–Amazonian transition represent poorly explored aquatic ecosystems whose hydrogeochemical heterogeneity may favor the establishment of specialized microbial communities. In this study, bacterial communities in sediments from 19 mineral springs in northern Peru were characterized using 16S rRNA gene sequencing, and their relationships with hydrogeochemical conditions and predicted functional potential were evaluated. The springs exhibited temperatures ranging from 15.1 to 38.2 °C and total dissolved solids (TDS) concentrations ranging from 0.022 to 162.5 mg L−1, reflecting marked variation in thermal and mineralization conditions. Bacterial communities were dominated by Desulfobacteraceae, Desulfosarcinaceae, Chlorobiaceae, Nitrosomonadaceae, Nitrospiraceae, and Rhodobacteraceae, including representative genera such as Halanaerobium, Chlorobium, Thiothrix, and Sulfurovum. Although alpha diversity did not differ significantly among hydrogeochemical categories, beta diversity analyses indicated compositional differentiation among thermal categories, while RDA revealed a significant multivariate association between bacterial community composition and the combined hydrogeochemical gradient (F = 1.0934, p = 0.035). Co-occurrence network analysis identified Desulfotignum, Roseimarinus, Halanaerobium, and Anaerophaga among the most highly connected taxa. PICRUSt2 predicted functional potential associated with carbon fixation, nitrogen and sulfur transformations, phosphorus acquisition and polyphosphate-related metabolism, and ferrous iron uptake. These findings provide the first integrated characterization of these bacterial communities and establish a baseline for future research on microbial ecology, biogeochemical cycling, and environmental biotechnology in Andean–Amazonian ecosystems of Peru.