Isolation and optimized production of putative antimicrobial compounds from Egyptian soil isolate Streptomyces sp. MS. 10

Mohamed Sebak,Abeer S Moawad,Walid Bakeer,Amal E Saafan,Sameh Abdelghani,Ahmed O El-Gendy

doi:10.1186/s43088-021-00099-7

Mohamed Sebak, Abeer S Moawad + Show 4 more

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https://doi.org/10.1186/s43088-021-00099-7

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Abstract

BackgroundThe rapid spread of antibiotic resistance has increased research interest in the discovery of natural products, mainly from actinomycetes, which have been the primary source of antimicrobial compounds. This study aimed to isolate, characterize, and optimize the production of some of the bioactive compounds from bioactive soil actinomycetes.ResultsOne promising soil actinomycete, which was molecularly identified as Streptomyces sp. and designated as Streptomyces sp. MS. 10, showed broad-spectrum antimicrobial activity, including activity against methicillin-resistant Staphylococcus aureus. Thus, it was selected for isolation of its major bioactive compounds. Polymerase chain reaction amplification of the genes responsible for antibiotic biosynthesis showed the presence of genes encoding type I and type II polyketide synthase. Liquid chromatography-mass spectrometry analysis found that the major antimicrobial compounds produced by Streptomyces sp. MS. 10 were weakly ionized bioactive secondary metabolites. A large-scale fermentation experiment of Streptomyces sp. MS. 10 using pre-optimized culture conditions followed by bioassay-guided chromatographic separation of its secondary metabolites resulted in the isolation of putative bioactive compounds that were identified as fatty acids using proton nuclear magnetic resonance spectroscopy.ConclusionsEgyptian soil is still a good source for exploring bioactive actinomycetes. Additionally, this study highlighted the importance of combining both physicochemical and genotypic characterization with spectroscopic analysis of the major natural products when isolating bioactive metabolites.

Highlights

The rapid spread of antibiotic resistance has increased research interest in the discovery of natural products, mainly from actinomycetes, which have been the primary source of antimicrobial compounds
Tryptone soya agar plates were surface inoculated with the indicator strains, followed by the use of a sterile borer to make 10-mm cups in the agar plates that were filled with 150 μL of the supernatant from a liquid broth culture of Streptomyces sp
MS. 10 as an actinomycete was made based on its mycelia coloration, pigment production, and morphological characteristics, followed by antimicrobial activity screening showing broad-spectrum activity against all tested indicator strains in this study, including methicillin-resistant Staphylococcus aureus (MRSA)

Summary

Introduction

The rapid spread of antibiotic resistance has increased research interest in the discovery of natural products, mainly from actinomycetes, which have been the primary source of antimicrobial compounds. Species of the Streptomyces genus are responsible for producing 75% of the reported metabolites isolated from actinobacteria [7, 8] Some of these compounds play a critical role in ecological systems by suppressing microbial competitors in their environment to protect their food supply. The production of such bioactive metabolites demonstrates highly organized and coordinated metabolic pathways in Streptomyces sp., which allows them to dominate among other ecosystem inhabitants [9, 10]. Many secondary metabolites produced by Streptomyces sp. have been successfully used as antibiotics in the treatment of drug-resistant infections in both humans and animals [12]

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