In Vitro Evaluation of Bioactive Metabolites from UV resistant Bacterial Strain Isolated from Cholistan Desert, Pakistan.

Abstract

Living organisms that are inhabiting extreme environments are termed as extremophiles which are classified into different groups. Among others, radiophiles include those organisms that thrive in environments of high radiations. Exposure to excessive amount of radiation can have dire consequences for an organism and can damage vital cellular structures including DNA, proteins, and lipids. Microorganisms that are living under intense amount of UV radiation have adopted several measures to resist negative impacts of UV radiation and produce several primary and secondary extremolytes which uplift the chances of survival for a microorganism. These extremolytes are involved in the provision of either a protective shield against the incoming UV radiation or participate in maintaining the integrity of cell regulatory machinery. In the current study, a bacterium designated as strain CH-8 was isolated from Cholistan desert of Pakistan. Strain CH-8 was found resistant to UV radiation and H2O2 with 60% survivability at 2712 J/m2 and 78% at 10 mM respectively. The bacterium was identified by morphological, biochemical, and molecular methods. 16S rRNA gene sequencing results indicated that strain CH-8 is 99.85% similar to Streptomyces sp. strain TRM46222, therefore the bacterium was named as Streptomyces sp. strain CH-8. Strain CH-8 showed black color pigmentation and its intracellular metabolites were extracted using methanol as a solvent. The total phenolic and total flavonoid assays of intracellular metabolites revealed the total phenolic content as 149 mg GAE/g DW and total flavonoid content as 2.082 mg QE/g DW. The metabolites from Streptomyces sp. strain CH-8 were then partially purified through silica gel column chromatography and evaluated for bioactive potential through various assays. The fractions I-8 and I-12 exhibited significant antioxidant (77% and 73.62%) as well as DNA damage prevention activities. Moreover, the fractions inhibited hemolysis of RBCs in anti-hemolysis assay and had a considerable cytotoxic activity. Furthermore, purified fractions also had a remarkable antibacterial activities and prevented the growth of Staphylococcus aureus and Escherichia coli. These findings suggested that extract of Streptomyces sp. strain CH-8 has antioxidant, radioprotective and antitumor potential which requires further evaluation.