Post-monsoon seasonal variation of prokaryotic diversity in solfataric soil from the North Sikkim hot spring

Abstract

The solfataric soil sediments of the hot springs of Sikkim located at Yume Samdung and Lachen valley were studied for deciphering the bacterial diversity. The main aim here is to present a comparative study and generate a baseline data on the post-monsoon seasonal variation for the months of October and December, analyzed through 16S rRNA V3-V4 amplicon sequencing. The results have shown that there is not much variation at phylum level in the month of October in all the three hot springs such as New Yume Samdung (NYS), Old Yume Samdung (OYS), and Tarum (TAR) hot spring. The abundant phyla mainly present were Firmicutes, followed by Proteobacteria, Actinobacteria, and Bacteroidetes. Similarly, in the month of December, Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes were prevalent; however, the percent relative abundance of these phyla in the month of December is relatively less. Besides this decrease in percent abundance, it was interestingly seen that relatively more phyla were found contributing towards the bacterial diversity in the month of December. Similar to phylum level, at genus level, there was not much variation seen among various prevalent genera of the three studied hot springs in both months. The major genera prevalent in both months among all the three hot springs were followed by Bacillus, Desulfotomaculum, Lactobacillus, and Paenibacillus. A similar trend was also seen at gene level that relative abundance of various genera was higher in the month of October but more genera were found to be contributing towards bacterial diversity in the month of December. Few distinct genera were found to be more abundant in the month of December such as Rhodopirellula and Blastopirellula. The results may conclude that there is not much variation in the abundance and type of bacterial communities during the post-monsoon season in the month of October and December. However, this may be assumed that there is the accumulation or increase in the bacterial communities during the winter (relatively higher temperature among hot springs) and may favor few mesophilic and more thermophilic communities as well.

Keywords: Geothermal system; Sikkim Himalayas; Soil microbial diversity; Thermophiles.