Bioaerosol Diversity and Ice Nucleating Particles in the North-Western Himalayan Region

This work presents measurements of bioaerosol diversity and ice nucleating particle (INP) concentration in total suspended particulate matter along a transect in the North-Western Himalayan Region. Drop freezing assay was used to measure INP spectra. Flow cytometry analysis was performed to examine the abundance of autofluorescent entities in the samples. The DNA sequences were used to analyze the relative abundance, diversity, and putative functional traits of the bioaerosol community. INP concentrations varied from 1.5 x 10(-3) to 5.5 L-1 air between -6 degrees C and -24 degrees C. Flow cytometry measurements showed a concentration stratification along the transect. Diversity measures showed that the communities are dominated by only a relatively few populations (sequence variants). Temperature and wind speed correlated with bioaerosol diversity measures. Firmicutes, Proteobacteria and Actinobacteria dominated DNA sequences obtained from samples. Populations belonging to the ice nucleating genera Pantoea and Pseudomonas were present, yet their relative abundance did not correlate with INP concentrations. Pantoea populations dominate during daytime and may be attributed to agricultural activities in the valley region with daytime anabatic winds potentially transporting the Pantoea from the valley to more remote upslope locations. Functional attributes showed dominance of metabolism (50%), followed by environmental information processing (11%), genetic information processing (9%), and cellular processes (7%). Results from this work demonstrate the importance of surface sources, land use pattern, and local meteorology for understanding atmospheric microbial communities and their link with INP concentrations in the atmosphere.