Isolation and characterization of a protease-producing thermophilic bacterium from an African hot spring

Abstract

The aim of this study was to screen for bacterial isolates from a hot spring in Eastern Zimbabwe (conditions in the hot spring: temperature 53 to 54°C and pH 9.3) for organisms of biotechnological interest. Screening of water samples from the hot spring resulted in the isolation of a novel bacterium with interesting protease activity. The bacterium was rod-shaped, Gram negative, motile, non-sporulating with 0.5 to 0.6 μM width and 2.0 to 4.0 μM length. It was oxidase and catalase positive and did not produce acid from glucose. The G+C content of the DNA was 71.7 mol%. A detailed examination of the isolate using conventional biochemical, physiological tests, fatty acid methyl ester analyses and 16S rDNA analysis showed that the strain code named EP1001 is a new genus within the γ-Proteobacteria that was distantly related to genera Stenotrophomonas, Xanthomonas, Xylella, and Lysobacter. The strain EP1001 produces an exoprotease enzyme when cultured in standard thermophilic M162 medium. The growth and protease production by the strain was also studied in shake flask cultivations to investigate optimum carbon and nitrogen sources. The results from physiological and biochemical characteristics, as well as fatty acids analysis, the 16S rDNA data and the chemotaxonomic data provided independent support for the novel nature of the isolate EP1001. In general, the results show that EP1001 isolate is a new bacterium in a new genus related to genera Stenotrophomonas, Xanthomonas, Xylella and Lysobacter, and has possibilities for use as a protease-producing bacterium.

Keywords: γ-Proteobacteria, moderate thermophile, hot spring