Characterization of bacterial diversity and ice-nucleating ability during different monsoon seasons over a southern tropical Indian region. (October 2018)

• Record Type: Journal Article
• Authors: Akila, M.; Priyamvada, Hema; Ravikrishna, R.; Gunthe, Sachin S.
• Is Part Of: Atmospheric environment. Volume 191(2018)
• Page Start: 387
• Page End: 394
• Publication Date: 2018-10
• Subjects: Bioaerosols -- Ice nucleating bacteria -- Indian monsoon -- Pseudomonas -- Pantoea; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2018.08.026
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: Bioaerosols abundantly found in the atmosphere can potentially influence the climate by acting as ice nuclei and thus profoundly influencing the hydrological cycle. As the first attempt over India, we report the diversity, abundance, and ice nucleating ability of bacteria present in the rainwater collected at Chennai, during summer and two contrasting monsoon seasons. Diverse bacterial communities were present in all the twenty rainwater samples and predominantly belonged to Actinobacteria (6%), Alpha proteobacter (9%), Bacilli (29%), Betaproterobacteria (14%), Flavobacteria (3%), and Gammaproteobacteria (39%). The most efficient ice nucleating bacteria such as Pseudomonas sp. and Pantoea sp. were present in our precipitation samples and they contributed to 8.4% and 9.4% of the total cultivable bacterial species obtained. The relative abundance of Pseudomonas was highest during the south-west monsoon (75%) whereas Pantoea was abundant in the north-east monsoon (51.8%). The dominant bacteria belonging to the known ice nucleating genera Pseudomonas, Pantoea, and Bacillus were chosen for the determination of their freezing temperatures using tube freeze assay technique. The onset freezing temperature of species belonging to Pseudomonas and Pantoea was recorded as −12 °C and for those species belonging to Bacillus it was found to be −14 °C. Further, the number of bacterial cells making up an ice nucleus was estimated at the temperatures ranging from −18 °C to −12 °C for all the ice nucleating bacteria and it was found to vary from 10 6 to 10 9 (cells/nucleus). Highlights: Identification of IN bacteria using DNA analysis was carried out in rain water. Gammaproteobacteria and Bacilli were diverse and abundant in samples collected. Pseudomonas and Pantoea showed disparity in abundance over two contrasting monsoons. Bacterial IN activity was observed at a temperature range of −12 °C to −18 °C. Bacterial ice nuclei in precipitation was as high as 14 (IN mL −1 of rain water).