Hot springs of Indian Himalayas: potential sources of microbial diversity and thermostable hydrolytic enzymes

Abstract

Microbial communities in hot springs at high elevations have been extensively studied worldwide. In this sense, the Indian Himalaya regions is valuable ecosystems for providing both the extreme 'cold' and 'hot' sites for exploring microbial diversity. In the present study, a total of 140 thermophilic bacteria were isolated from 12 samples collected from Manikaran and Yumthang hot springs of Indian Himalayas. The bacterial isolates were studied for phylogenetic profiling, growth properties at varying conditions and potential sources of extracellular thermostable hydrolytic enzymes such as protease, amylase, xylanase and cellulase. Based on production of extracellular hydrolases, 51 isolates from Manikaran (28) and Yumthang thermal springs (23) were selected and identified using 16S rRNA gene sequencing which included 37 distinct species of 14 different genera namely Anoxybacillus, Bacillus, Brevibacillus, Brevundimonas, Burkholderia, Geobacillus, Paenibacillus, Planococcus, Pseudomonas, Rhodanobacter, Thermoactinomyces, Thermobacillus, Thermonema and Thiobacillus. Out of 51 hydrolase producing bacteria, 24 isolates showed stability at wide range of temperature and pH treatments. In present investigation, three thermotolerant bacteria namely, Thermobacillus sp NBM6, Paenibacillus ehimensis NBM24 and Paenibacillus popilliae NBM68 were found to produced cellulase-free xylanase. These potential extracellular thermostable hydrolytic enzymes producing thermophilic bacteria have a great commercial prospect in various industrial, medical and agriculture applications.

Keywords: 16S rRNA gene; Diversity; Himalayan hot springs; Thermophiles; Thermostable extracellular hydrolases.

Fig. 1

a Diversity and distribution of 51 bacterial isolates for four different hydrolytic enzymes production at high temperature; b the Venn diagram illustrates the number of extracellular hydrolytic enzymes producing bacteria

Fig. 2

Phylogenetic analysis of thermo-active hydrolytic enzymes producing bacteria obtained from a Manikaran hot springs; b Yumthang hot springs. The 16S rRNA gene sequence based dendrogram representing isolates were constructed by neighbor-joining method. Accession numbers of each isolate was given in parenthesis, and reference sequences having ≥97% similarity were used as taxonomic representatives. The bootstrap values (1000 replications) were indicated at the nodes