Dissemination of genes associated with antibiotic resistance and bacterial virulence during ecosystem succession in two Tibetan glacier forefields.

The release of pathogens and DNA from the cryosphere (glacier, permafrost, and, sea ice) has become a new threat to society and environment. Due to enhanced glacier retreat, the size of glacier forefields has greatly expanded. Herein, we used a combination of metagenomic and metatranscriptomic methods and adopted a sequence-based approach to investigate the distribution and changing patterns of virulence factor genes (VFGs) and antibiotic resistance genes (ARGs) in two glacier forefields. The forefields are separated by approximately 400 km located in the center and north of the Tibetan Plateau, which are used to demonstrate the gene dissemination capacity across short (10 m) and long (730 m) spatial transects. The results revealed a diverse range of actively transcribed VFGs and ARGs. The relative abundance of ARG reduced with ecosystem succession, while that of VFG was similar, suggesting that the ARG is under a stronger environmental selection pressure. VFGs and ARGs were dominated by those associated with adherence and vancomycin resistance, respectively. Notably, toxin production related genes were identified but a low abundance, indicating a low risk to health in glacier forefields. The dissemination risks were low for both VFGs and ARGs, which was strongly constrained by dispersal limitation. Additionally, the limited dissemination was mainly through vertical transmission, instead of horizontal transfer. In conclusion, the sequence-based approach revealed a low risk to health in recently deglaciated areas, with the risk of VFGs and ARGs being disseminated into downstream ecosystems remaining low.