Molecular Characterization and Phenotype Analysis of a Novel Psychrotrophic Exiguobacterium Species from the Ilam Mountains

The genus Exiguobacterium includes psychrotrophic, mesophilic, and moderate thermophilic strains and species that have been isolated from extreme environments, including very cold or hot environments. The genus Exiguobacterium has received much attention in biotechnology, and related industries due to secretory enzymes with high enzymatic activity and consequently stable enzymes capable of tolerating extreme conditions. The aim of the present study was to introduce and describe the phenotypic and the genotypic characterization of a novel species of genus Exiguobacterium isolated from the Ilam mountains, Iran.

Genotypic features were analyzed using universal genes (gyrB, hsp70, rpoB, and citC) belonging to the Exiguobacterium genus. Also, cspC1, nusA, and dnaJ genes were used to confirm the profile of new psychrotrophic strains. The distinctive phenotypic characteristics of the new strain with the most famous strains of the genus Exiguobacterium were investigated. All statistical analyses were conducted using R Packages for data visualization and exploratory data.

A motile, Gram-stain-positive, rod-shaped, non-sporing, tolerant up to 5% NaCl, grew at 0-25 °C and pH 6 and 9, designated Exiguobacterium sp. HA2 was isolated from the soil. The major isoprenoid quinone is MK-7 and in the smaller amount are MK-6 and MK-8. The major cellular fatty acids (>10 %) were isoC13:0, isoC15:0, and C16:0. To adapt to low temperatures, Exiguobacterium sp. HA2 upregulated expresses cold shock response including cold shock protein (CSP) and transcription elongation protein NusA. Also, downregulated expression of heat shock protein DnaJ domain protein.

In the current study we investigated the difference in the genotype, phenotypic, and functional characteristics of Exiguobacterium sp. HA2. It can be regarded as representing a novel psychrotrophic species within the genus Exiguobacterium.