Antioxidative and Radioprotective Properties of Glycosylated Flavonoid, Xanthorhamnin from Radio-Resistant Bacterium Bacillus indicus Strain TMC-6.

A radio-resistant bacterium labeled as strain TMC-6 was isolated from Thal desert, Pakistan and identified through 16S rRNA gene sequencing as Bacillus indicus strain TMC-6 (MN721293). The isolate was found to be resistant to UV radiation dose of 6.780 × 103 J/m2 and showed 50% survivability to mitomycin C (6 µg/ml) and H2O2 (30 mM). The bacterium showed yellowish orange coloration when grown on tryptone yeast glucose (TGY) medium. The cellular metabolite was extracted in methanol and purified through solid phase extraction with C18 column cartridge. The compound was characterized through UV/Visible spectrophotometry, Fourier Transform Infra-Red (FT-IR) spectroscopy and Liquid Chromatography Mass Spectrometry (LC-MS). The LC-MS analysis of the compound revealed a molar mass of 769 [m/z]- that matched the chemical formula C34H42O20 and identified as a glycosylated flavonoid xanthorhamnin. The compound showed significant antioxidant (77.05%) and metal chelation (79.80%) activities. Xanthorhamnin showed promising oxidative damage inhibitory actions in bovine serum albumin (65.32%) and mice liver lipids (71.61%) and prevented DNA strand breaks from oxidative stress. Cytotoxicity in brine shrimp larvae was observed when compared with mitomycin C indicating its effect toward cancerous cells. These findings concluded that xanthorhamnin from radio-resistant Bacillus indicus strain TMC-6 has high antioxidant, radioprotective, and antitumor properties against UV-mediated oxidative damages.

Unraveling the Radioprotective Mechanisms of UV-Resistant Bacillus subtilis ASM-1 Extracted Compounds through Molecular Docking.

Radioresistant microorganisms possess inimitable capabilities enabling them to thrive under extreme radiation. However, the existence of radiosensitive microorganisms inhabiting such an inhospitable environment is still a mystery. The current study examines the potential of radioresistant microorganisms to protect radiosensitive microorganisms in harsh environments. Bacillus subtilis strain ASM-1 was isolated from the Thal desert in Pakistan and evaluated for antioxidative and radioprotective potential after being exposed to UV radiation. The strain exhibited 54.91% survivability under UVB radiation (5.424 × 103 J/m2 for 8 min) and 50.94% to mitomycin-C (4 µg/mL). Extracellular fractions collected from ASM-1 extracts showed significant antioxidant potential, and chemical profiling revealed a pool of bioactive compounds, including pyrrolopyrazines, amides, alcoholics, and phenolics. The E-2 fraction showed the maximum antioxidant potential via DPPH assay (75%), and H2O2 scavenging assay (68%). A combination of ASM-1 supernatant with E-2 fraction (50 µL in a ratio of 2:1) provided substantial protection to radiosensitive cell types, Bacillus altitudinis ASM-9 (MT722073) and E. coli (ATCC 10536), under UVB radiation. Docking studies reveal that the compound supported by literature against the target proteins have strong binding affinities which further inferred its medical uses in health care treatment. This is followed by molecular dynamic simulations where it was observed among trajectories that there were no significant changes in major secondary structure elements, despite the presence of naturally flexible loops. This behavior can be interpreted as a strategy to enhance intermolecular conformational stability as the simulation progresses. Thus, our study concludes that Bacillus subtilis ASM-1 protects radiosensitive strains from radiation-induced injuries via biofilm formation and secretion of antioxidative and radioprotective compounds in the environment.