Microbial Diversity of High-Altitude Geothermal Springs in Tajikistan

Abstract

Thermophiles are a group of heat loving microbes thriving in various hot ecological niches including geothermal springs. Many high-altitude geothermal springs are located on the territory of Tajikistan, microbial diversity of which have not yet been explored.Over the last decades, thermophilic microbes have fascinated researches in many fields due to their ability to withstand and function under extreme conditions. Thermophilic microbes are a great source of thermostable enzymes, which show unique features that can be used in biotechnological processes at elevated temperatures and under other harsh conditions. Unexplored geothermal springs in Tajikistan are promising sources for isolation of thermophilic microbes with useful enzymatic activities.In this regard, a total of 21 thermophilic aerobic bacteria and one thermophilic anaerobic bacterium were isolated from three high-altitude mineralized Tajik geothermal springs with temperatures ranging from 50.5 to 89 °C. The isolates were phylogenetically identified and studied for their potential to produce extracellular hydrolytic enzymes (such as protease, amylase, lipase, and cellulase). The identification of isolates based on 16S rRNA gene sequences revealed relationships to members of more than 10 different species belonging to 5 genera, namely Aeribacillus, Anoxybacillus, Geobacillus, Parageobacillus, and Thermotoga. Geobacillus spp. were found to be the most abundant (cultivable) aerobic species in the studied geothermal springs. Some of the isolated bacilli shared less than 96% sequence similarity with their closest match in GenBank, indicating that Tajik geothermal springs harbor potentially novel bacilli species. More than 20 isolates actively produced one or more extracellular hydrolases like proteases, amylases, or lipases, which makes them a potential source for thermostable hydrolases for use in biotechnological processes.