Thermoactinomycetes isolated from geothermal springs in Armenia capable of producing extracellular hydrolases

Abstract

Microbes colonizing high elevation hot springs have been extensively studied in last decades. In this sense, Armenian highland geothermal springs are in the center of attention for exploring new thermophilic microbes with biotechnological prospects. In present paper, the identification and characterization of two thermoactinomycetes isolated from Armenian geothermal springs, namely Akhurik and Tatev, were reported. The isolates, designated as AkhA-12 and Tatev 35a were studied for phenotypic and phylogenetic profiling. The aerial and substrate mycelia formed by strain AkhA-12 were yellow-white and greyish-yellow respectively. The strain Tatev 35a developed white aerial and substrate mycelia. The endospores produced by thermoactinomycetes were round in shape (0.7–0.9 µm in diameter) and located on short unbranched sporophores. The strains grew aerobically at 35–60 °C (Topt 50–55 °C). The pH range for growth was observed between 5.0 and 8.0 with optimum pH 7.0–7.4. Both strains were able to grow at 0–8% NaCl (optimum 2–3%). Based on phenotypic characteristics and phylogenetic analyses (16S rRNA gene sequence analysis) both strains were identified as representatives of the genus Thermoactinomyces. The strain AkhA-12 demonstrated close relationship to Thermoactinomyces sp. JIR-004 (99.7% similarity) and T. daqus DSM 45914T (99.4% similarity), while the strain Tatev 35a was closely related to T. vulgaris DSM 43016T (99.01%). The ability to synthesize extracellular hydrolases (amylase, lipase and protease) was evaluated by growth of strains on solid media supplemented with appropriate substrate at different temperatures. The active production of thermostable hydrolytic enzymes by strains indicates their potential in biotechnology.