Long-range transported bacteria perturbing airborne bacterial diversity and pathogenicity over Eastern Himalayas,...

Long-range transported bacteria have a significant impact on hill-top airborne bacterial diversity and pathogenicity. Present study investigates airborne bacterial community structure over a hill-top region of the Eastern Himalayas, based on two years (2022--23) of investigations on culture-independent metagenomic analysis. Winter-time hill-top microbial loading is found to be a minimum of about 21,401.5 ± 2791.0 × 10⁵ m^-3, representing background Himalayan airborne bacterial concentration, and a maximum of 6.7 ± 1.2 × 10⁵ m^-3 on dusty summer days. 80 % of the total Himalayan bacterial population is due to long-range transport via horizontal and vertical movement of atmosphere, causing about 60 % perturbation in Himalayan bacterial diversity. Space-borne observations with 3-days back-trajectories analysis reveal a thick dust layer between 2 and 3 km over Eastern Himalayas, coming from the Thar Desert. Long-range transported dust-attached bacteria cause a 40 % enhancement in unique bacterial loading, while 6 % unique genera are noticed in upwelling of foothill pollution, and 8 % unique bacterial genera are found in downwelling from free troposphere to the hill-top atmosphere. Desert dust-attached long-range transported bacteria contain one-third skin-infecting pathogens, while upwelling pollutants carry mainly respiratory-infecting bacteria (45 %), and downwelling transport is dominated by gastrointestinal tract-infecting bacteria (50 %). Interestingly, local Himalayan bacteria (20 %) are consistently loaded with pathogens, predominantly causing respiratory (36 %) and skin (31 %) infections throughout the study period. Present results highlight the profound impact of atmospheric transport processes on regional bacterial diversity and public health in hill-top region, highlighting Himalayan atmosphere as a dynamic and global conveyor of life, including pathogens across long distances.