Isolation and Characterization of Thermus thermophilus Strain ET-1: An Extremely Thermophilic Bacterium with Extracellular Thermostable Proteolytic Activity Isolated from El Tatio Geothermal Field, Antofagasta, Chile

Abstract

The present study describes the isolation of an extremely thermophilic bacterium from El Tatio, a geyser field in the high planes of Northern Chile. The thermophile bacterium named Thermus thermophilus strain ET-1 showed 99% identity with T. thermophilus SGO.5JP 17-16 (GenBank accession No. CP002777) by 16S rDNA gene analysis. Morphologically, the cells were non-sporeforming Gram-negative rods that formed colonies with yellow pigmentation. This strain is able to proliferate between 55 and 80 °C with a pH range of 6–10, presenting an optimum growth rate at 80 °C and pH 8. The bacterium produces an extracellular protease activity. Characterization of this activity in a concentrated enzyme preparation revealed that extracellular protease had an optimal enzymatic activity at 80 °C at pH 10, a high thermostability with a half-life at 80 °C of 10 h, indicating that this enzyme can be classified as an alkaline protease. The proteolytic enzyme exhibits great stability towards chelators, divalent ions, organic solvents, and detergents. The enzyme was inhibited by phenylmethylsulfonyl fluoride (PMSF), implying that it was a serine protease. The high thermal and pH stability and the resistance to chelators/detergents suggest that the protease activity from this T. thermophilus. strain could be of interest in biotechnological applications.