Bacterial Diversity in an Alpine Debris-Free and Debris-Cover Accumulation Zone Glacier Ice, North Sikkim, India

Abstract

The Himalayas are water tower for billions of people; however in recent years due to climate change several glaciers of Himalaya are receding or getting extinct which can lead to water scarcity and political tensions. Thus, it requires immediate attention and necessary evaluation of all the environmental parameters which can lead to conservation of Himalayan glaciers. This study is the first attempt to investigate the bacterial diversity from debris-free Changme Khang (CKG) and debris-cover Changme Khangpu (CK) glacier, North Sikkim, India. The abundance of culturable bacteria in CKG glaciers was 1.5 × 10⁴ cells/mL and CK glacier 1.5 × 10⁵ cells/mL. A total of 50 isolates were isolated from both the glacier under aerobic growth condition. The majority of the isolates from both the glaciers were psychrotolerant according to their growth temperature. Optimum growth temperatures of the isolates were between 15 and 20 °C, pH 6-8 and NaCl 0-2%. The phylogenetic studies of 16S RNA gene sequence suggest that, these 21 isolates can be assigned within four phyla/class, i.e., Firmicutes, Beta-proteobacteria, Gamma-proteobacteria and Actinobacteria. The dominant phyla were Firmicutes 71.42% followed by Actinobacteria 14.28%, Alpha-proteobacteria 9.52% and Beta-proteobacteria 4.76%. The isolate Bacillus thuringiensis strain CKG2 showed the highest protease activity (2.24 unit/mL/min). Considering the fast rate at which Himalayan glaciers are melting and availability of limited number of research, there is urgent need to study the microbial communities confined in such environments.

Keywords: Changme Khang; Changme Khangpu; Glacier; Psychrophiles; Psychrotolerant.

Fig. 1

a, b Phylogenetic tree of Changme Khang and Changme Khangpu isolates. Neighbor-joining trees showing the phylogenetic relationships of bacteria 16S rRNA gene sequences from a Changme Khang glacier and b Changme Khangpu glacier ice core to closely related sequences from the GenBank database

Fig. 2

Bacterial diversity Heat map. A color scale heat-map showing culturable bacterial diversity assessment of five Himalayan glacier predominant 16S rRNA gene based bacterial sequences classified at Phylum level. Light green indicate higher abundance; light blue and dark blue indicate lower abundance. Roungbuk glacier, Changme Khangpu glacier (CK), Changme Khang glacier (CKG), Muztag Ata glacier and Roopkund glacier respectively (color figure online)

Fig. 3

Principal component analysis of bacterial diversity. Principal component analysis (Distance Biplot): The first two PC1 and PC 2 are major components possessing 49.4 and 27.8% respectively. The graph shows the positive correlation between Rongbuk glacier, Changme Khangpu and Changme Khang glacier bacterial diversity

Fig. 4

Principal component analysis of physical parameter and bacterial diversity. Principal component analysis (Distance Biplot): The first two components 1 and 2 are major components possessing 82.95 and 17.04% respectively. The graph shows that Alpha-proteobacteria of Changme Khang glacier showed positive correlation with DO whereas in Changme Khang glacier Gamma-proteobacteria and ORP were positively correlated with each other