Population Ecology of Glacier Bacteria from the View of Gene Flow in Cryobacterium

Glaciers have been proposed as evolutionary hotspots for microbial evolution; however, direct evidence for glacial microbial population formation and genomic loci undergoing selective sweeps remains limited. To address this knowledge gap, we investigated the genomic diversity, evolutionary pressures, and adaptive strategies of <i>Cryobacterium</i>, a representative genus of glacier environments. Based on recent gene flow analysis, 18 distinct populations of <i>Cryobacterium</i> were identified, each exhibiting clear discontinuities in gene flow and genetic boundaries. Selective pressure analyses revealed purifying selection within populations, maintaining genetic stability, and positive selection between populations, suggesting adaptive divergence from environmental differences. Notably, half of the populations spanned geographically distant glaciers, suggesting widespread dispersal mechanisms such as atmospheric circulation or glacial fauna migrations. We identified 17 genes under strong selective sweeps, involved in metabolic enzymes, transporters, and gene regulation. Based on the reverse ecology principles, these genes (e.g., glucose-6-phosphate dehydrogenase assembly and RNA polymerase-binding gene), are likely to be critical for cold adaptation. This study provided clear genomic evidence of glacial microbial population formation driven by recent gene flow, significantly enhanced our understanding of microbial adaptation in extreme cold ecosystems, and emphasized the importance of deep genomic sequencing in ecological and evolutionary research.