Investigação da atividade antimicrobiana de streptomyces Spp. Isolados de solos do maranhão

Abstract

Investigations focused on Actinobacteria resulted in the discovery of many crucial antimicrobial drugs that still save countless human lives around the world. However, the emergence of resistance to antibiotics and antifungals often makes available drugs ineffective, making it essential to prospect for new compounds in new species or in poorly studied species of Actinobacteria. Thus, this study evaluated five actinobacteria from the soil of some cities of the State of Maranhão in order to investigate their potential antimicrobial activity. After fermentation and extraction of metabolites with different solvents, assays were carried out to evaluate the antimicrobial activity, chemical characterization and genotypic identification of each soil isolate. The actinobacteria isolates were observed to exhibit antimicrobial activity against one or all strains analyzed, including Mycobacterium smegmatis (ATCC 700084), Candida albicans (ATCC 90028), Candida krusei (ATCC 6258), Candida parapilopsis (ATCC 22019) and against Candida albicans (SWSC 5314). For submerged fermentation tests, cultivation in 96 h in Bennett's medium supplemented with 1% glucose proved to be the best carbon source for obtaining antimicrobial compounds. Extraction of the metabolites with different solvents demonstrated a good spectrum of inhibitory activity against Candida species, mainly the ethanolic extract of the biomass (Et) of the isolate Streptomyces sp. No. 516 with MIC value of 0.156 mg/ml. Of the five isolates, only No 220 was identified at the species level (Streptomyces owasiensis). The others were identified as Streptomyces sp., suggesting that they may be species not yet known. In the chemical prospection of the crude extracts of the biomass of isolate 516, the presence of Desferrioxamine A1, Desferrioxamine B and Ferrioxamine B, which are considered siderophores or iron chelating compounds, was demonstrated. Other compounds were present but not identified. In summary, our data demonstrate that the microorganisms analyzed in the soil are producers of antimicrobial and thermostable compounds, with a promising isolate (No. 516) in terms of producing antifungal compound, apparently not known.