Hydrochemistry, microbial ecology and physiological-biochemical properties of isolated bacteria of Tyrma hot spring (Far East of Russia)

Abstract

In this study, we investigated for the first time the geochemistry, abundance, diversity and some physiological and biochemical properties of cultured bacterial communities inhabiting the Tyrminskie thermal springs (Far East, Russia). The thermal waters from the Tyrma Spring are characterized by a low mineralization level (less than 0.25 g/L), an alkaline pH medium (pH=9.4) and a fluoride (up to 10 mg/L) and bicarbonate sodium-based composition. In these thermal waters and associated microbial mats, low numbers of physiological groups of microorganisms were noted, with a predominance of heterotrophically active nitrifying bacteria in the water and silicate- and sulfate-reducing bacteria in the mats. The average air temperature during the winter was −7°C. The temperature of the spring water during sampling was recorded between 31.8 and 36.8°C. These temperatures favor the presence of mesophilic and thermotolerant microorganisms in the thermal waters, which is consistent with the identified bacterial genera. Bacterial strains isolated from the thermal waters were identified using the 16S rRNA gene. The isolated bacterial strains belong to the phyla Firmicutes, Proteobacteria and Actinobacteria. Bacterial strains of thermal waters were represented by the genera Bacillus, Ochrobactrum, Brevibacterium, Achromobacter. Shannon and Simpson ecological indices showed low bacterial diversity and their uniform distribution in the community. It should be noted that this assay is based solely on cultured microorganisms using standard culture media. According to canonical correspondence analysis the greatest influence on bacterial diversity was exerted by the elements: calcium, sodium, fluorine, and hydrocarbonates. The isolated bacteria were able to metabolize a wide range of carbohydrates and alcohols, although they fermented lactose poorly. Cultures of the Bacillus genus show the greatest sugar-metabolizing activity. The isolates are capable of producing extracellular enzymes, indicating their potential industrial applications.