A considerable amount of research exists concerning the interactions of microbes and important agricultural plant species. Little is known, however, about the integrated ecology of alpine plant communities and proximal bacterial communities in the air and soil. To address this deficit, we resampled plant survey sites established approximately 10 years ago on three mountains (Mineral Peak, Wolverine Peak, and Republic Peak; >3000 m) within and near the northeast border of Yellowstone National Park. Four sites on each of the three mountains were visited during the early (June), peak (July), and late growing season (August). Abundance and cover estimates of vegetation were recorded along a 10 m transect at all sites to provide a reference point for microbial associations and temporal comparison of previous sampling campaigns. Air (~1.5 m above ground) and soil samples (5 cm homogenized cores) were collected from each site for each month to assess seasonal effects on microbial communities. Air samples (soil, in progress) were extracted and processed through a bacteria-specific 16S rRNA bar-coded pyrosequencing approach (V4 region). The Mothur software pipeline and SILVA database were primarily used to identify bacterial amplicons.
Preliminary results indicate that bacterial species richness in the atmosphere is greatest during peak growing season. Bacterial representation was highest in the phyla Proteobacteria, Actinobacteria, Firmicutes, Bacteroidetes, and Chloroflexi. Generally, sites sheltered from a prevailing south-westerly wind and with more developed soil had greater total plant cover, plant diversity, and greater abundance of atmospheric bacteria than exposed sites. Non-metric multidimensional scaling (NMDS) revealed that plant abundance and diversity have not experienced significant shifts in diversity or abundance. Atmospheric bacteria did not demonstrate any consistent patterns among sites. This may be a by-product of collection methods and the similar origin of air currents among the three mountains. We expect that soil bacteria will be more abundant and diverse overall than those found in air samples, but should reflect similar patterns of temporal abundance. Low concentration of genomic DNA is a challenging byproduct of sampling at high-elevation. Only the July sampling effort on Mineral Peak produced measurable amplicons from atmospheric bacteria. In contrast, Wolverine Peak had nearly complete temporal and site representation of amplicons for atmospheric bacteria. Further, contaminants in DNA extraction kits may generate misleading results in samples with low microbial biomass. To address this, we optimized DNA extraction techniques and field methods to increase the resolution, accuracy, and overall comparative power of our data.