Targeting functional genes to study bacterial diversity, community structure and stability in the Polar atmosphere

Abstract

We investigate bacterial communities in Polar air, focusing on functionally relevant bacterial ice nucleators. Three aerobiological sampling regimes were analysed: two from Antarctica (Southern Ocean and South Georgia) and one from the Arctic (Svalbard), addressing three research aims. First, bacterial INA gene abundance was determined by quantitative PCR, examining the influence of location and weather. Second, the impact of sampling methodology was assessed, and third, taxonomy and functional potential were explored. Total bacterial biomass was comparable to global air estimates. INA gene abundance in the Antarctic ranged from 33 to 248 copies per m³ over the Southern Ocean and South Georgia, respectively. INA gene abundance as a percentage of total biomass (relative abundance) was higher in air sampled over land in both the Antarctic (~1.0% in South Georgia) and Arctic (~0.4% in Svalbard), but lower in air sampled over the Southern Ocean (<0.1%). Weather conditions did not majorly influence total biomass or INA gene abundance, though cyclonic conditions, temperature, and cloud cover slightly affected relative INA abundance. Choice of sampling device had no impact on 16S rRNA or INA gene copy numbers. However, significant differences were found in diversity (p = 0.004) and evenness (p = 0.007) at ~400m sampling height, suggesting that device impact may depend on altitude. Polar airborne communities were dominated by Proteobacteria, Actinobacteria, Firmicutes, and Bacteroidetes. Genera known to contain ice nucleating species, such as Pseudomonas, Xanthomonas, and Paenibacillus, were detected. Metagenomic analysis of air and precipitation revealed stress-tolerant fungal and bacterial species adapted for atmospheric residence. Functional gene families included those involved in the production of cold shock proteins and carotenoid pigments. This study enhances the understanding of polar airborne bacterial communities, particularly ice nucleators. Overall, this research contributes to Polar atmospheric microbiology, with potential applications in weather prediction.

Date of Award	27 Feb 2025
Original language	English
Awarding Institution	Northumbria University
Supervisor	David Pearce (Supervisor) & Lynn Dover (Supervisor)