Isolation and characterization of a novel strain of genus Dietzia capable of multiple-extreme resistance

Abstract

An ultraviolet (UV) radiation resistant gram-positive bacterium, Dietzia sp. MG4 strain, was isolated from the Sirch Hot Spring (Kerman, Iran), then it was identified on the basis of morphological and biochemical characteristics, and 16S rRNA gene sequencing. The effects of temperature, pH, desiccation, different percentage of NaCl, hydrogen peroxide (H2O2), mitomycin C (MMC) and high levels of radiation on viability or growth rate of MG4 strain were investigated. Also heavy metal tolerance of MG4 strain was assayed. 16S rDNA sequence of the isolate exhibited 99.69% similarity with Dietzia sp. and this result was confirmed by phylogenetic analysis. Viability of this strain was obtained D91 according to D index after exposure to 25 J/cm2 UV radiation dose, and D30 after desiccation stress (for 28 days) using flow cytometery. The D10 value for a microorganism is defined as the stress dose necessary to provide 10% survivors. Therefore, this strain showed high resistance to UV-C radiation and moderate resistance to desiccation. Optimal growth of MG4 strain was observed at pH 9, temperature of 30°C and 5% (w/v) NaCl. Isolated Dietzia was resisted up to 3 mM of nickel and 0.2 mM of mercury ions. Also this strain could tolerate 1–4% (v/v) H2O2 and 8 µg/mL of MMC as oxidant agents. To the best of our knowledge, this is the first study on multiple extreme resistant Dietzia sp. MG4 strain. © 2015, Pleiades Publishing, Ltd.