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

• Published in: Microbiology (New York) Vol. 84; no. 3; pp. 389 - 397
• Main Authors: Gholami, M., Etemadifar, Z.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.05.2015
• Subjects: Biomedical and Life Sciences; Experimental Articles; Life Sciences; Medical Microbiology; Microbiology; polyextremophilic bacteria; flow cytometry; UV-resistance; oxidative stress
• ISSN: 0026-2617; 1608-3237
• DOI: 10.1134/S0026261715030054

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 (H 2 O 2 ), 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 D 91 according to D index after exposure to 25 J/cm 2 UV radiation dose, and D 30 after desiccation stress (for 28 days) using flow cytometery. The D 10 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) H 2 O 2 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.