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Molecular profiling and anti-infective potency of endophytic actinomycetes inhabiting Madhuca insignis Radlk., from Western Ghats of India.

ABSTRACT:

Background

Endophytic actinomycetes are well known for their diverse bioactive entities and considered as an important source for drug development research.

Results

We isolated and identified four potential endophytic Streptomyces species, i.e., Streptomyces misionensis MI22, Streptomyces roietensis MI24, Streptomyces glaucescens MI29, and Streptomyces sp. MI04 inhabiting Madhuca insignis by its characteristic morphological features and 16S rRNA gene sequence analysis. S. misionensis MI22 exhibits a broad spectrum of anti-microbial activity against methicillin-resistant Staphylococcus aureus (25.00 ± 1.00 mm) followed by Bacillus subtilis (23.66 ± 0.57 mm), Escherichia coli (22.00 ± 0.00 mm), and Candida albicans (18.00 ± 0.00 mm). Minimum inhibitory concentrations of the ethyl acetate fraction of S. misionensis MI22 against test pathogens were ranged from 25 to 100 μg/mL. Indeed, strain MI22 also exhibited significant anti-proliferative activity against HeLa cell line with IC₅₀ value 98 μg/mL and showed no cytotoxicity effect to the normal human embryonic kidney cell line in the MTT assay. The anti-microbial metabolites from strain MI22 were detected at R_f 0.55 as depicted by the inhibition zone on the intensive band in TLC-bioautography assay.

Conclusion

The study indicates that, anti-microbial metabolites of these endophytic Streptomyces species, especially S. misionensis MI22 as a prolific source to discover novel bioactive metabolites to combat multidrug-resistant pathogens.

SUBMITTER: Mondal S

PROVIDER: S-EPMC7903210 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The search for novel bioactive metabolites continues to be of much importance around the world for pharmaceutical, agricultural, and industrial applications. Actinobacteria constitute one of the extremely interesting groups of microorganisms widely used as important biological contributors for a wide range of novel secondary metabolites. This study focused on the assessment of antimicrobial and antioxidant activity of crude extracts of actinobacterial strains. Western Ghats of India represents unique regions of biologically diverse areas called "hot spots". A total of 32 isolates were obtained from soil samples of different forest locations of Bisle Ghat and Virjapet situated in Western Ghats of Karnataka, India. The isolates were identified as species of Streptomyces, Nocardiopsis, and Nocardioides by cultural, morphological, and molecular studies. Based on preliminary screening, seven isolates were chosen for metabolites extraction and to determine antimicrobial activity qualitatively (disc diffusion method) and quantitatively (micro dilution method) and scavenging activity against DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS(2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radicals. Crude extracts of all seven isolates exhibited fairly strong antibacterial activity towards MRSA strains (MRSA ATCC 33591, MRSA ATCC NR-46071, and MRSA ATCC 46171) with MIC varying from 15.62 to 125 μg/mL, whereas showed less inhibition potential towards Gram-negative bacteria Salmonella typhi (ATCC 25241) and Escherichia coli (ATCC 11775) with MIC of 125-500 μg/mL. The isolates namely S1A, SS5, SCA35, and SCA 11 inhibited Fusariummoniliforme (MTCC 6576) to a maximum extent with MIC ranging from 62.5 to 250 μg/mL. Crude extract of SCA 11 and SCA 13 exhibited potent scavenging activities against DPPH and ABTS radicals. The results from this study suggest that actinobacterial strains of Western Ghats are an excellent source of natural antimicrobial and antioxidant compounds. Further research investigations on purification, recovery, and structural characterization of the active compounds are to be carried out.