Antimicrobial activity of actinomycetes and characterization of actinomycin-producing strain KRG-1 isolated from Karoo, South Africa

Abstract

In the present study we reported the antimicrobial activity of actinomycetes isolated from aridic soil sample collected in Karoo, South Africa. Eighty-six actinomycete strains were isolated and purified, out of them thirty-four morphologically different strains were tested for antimicrobial activity. Among 35 isolates, 10 (28.57%) showed both antibacterial and antifungal activity. The ethyl acetate extract of strain KRG-1 showed the strongest antimicrobial activity and therefore was selected for further investigation. The almost complete nucleotide sequence of the 16S rRNA gene as well as distinctive matrix-assisted laser desorption/ionization-time-of-flight/mass spectrometry (MALDI-TOF/MS) profile of whole-cell proteins acquired for strain KRG-1 led to the identification of Streptomyces antibioticus KRG-1 (GenBank accession number: KX827270). The ethyl acetate extract of KRG-1 was fractionated by HPLC method against the most suppressed bacterium Staphylococcus aureus (Newman). LC//MS analysis led to the identification of the active peak that exhibited UV-VIS maxima at 442 nm and the ESI-HRMS spectrum showing the prominent ion clusters for [M-H 2 O+H] + at m/z 635.3109 and for [M+Na] + at m/z 1269.6148. This information could be assigned to chromopeptide lactone antibiotic-actinomycin. Our results suggest that unexplored soils could be an interesting source for exploring antibacterial secondary metabolites.

SELECTIVE ISOLATION OF Dactylosporangium AND Micromonospora FROM THE SOIL OF KARST CAVE OF SIMEULUE ISLAND AND THEIR ANTIBACTERIAL POTENCY

“…In this study, we obtained only seven genera of actinomycetes against tested bacteria and particularly against gram -positive bacteria. Our results support previous studies which showed that the most of isolates of actinomycetes had activity against gram-positive bacteria (Charousova et al 2019;Baskaran et al, 2011).…”

Chemical Profiling of Antimicrobial Metabolites from Halophilic Actinomycete Nocardiopsis_sp. Al-H10-1 (KF384482) Isolated from Alang, Gulf of Khambhat, India

“…Al-H10-1 were extracted by using ethyl acetate (1:1 v/v) from filtrate broth. Charousová I et. al., 2019 also extracted the antimicrobial compounds produced by selected actinomycetes isolated using aridic soil sample collected from Karoo, South Africa.…”

Antagonistic Potential of Soil Streptomyces Isolates from Southern Thailand to Inhibit Foodborne Bacterial Pathogens

“…The results were in agreement with Abussaud et al [ 40 ] that found only 5 of 8 active isolates having activity on agar medium produced antagonistic effects in broth culture. These results may be attributed to differences in the culture media composition, inoculum size, or growth conditions that influence the ability of Streptomyces isolates to secrete different active substances on solid growth surfaces and liquid media [ 8 , 42 ]. Another possible explanation is that some active metabolites discharged by streptomycetes may be destroyed or chemically altered during the solvent extraction process [ 8 , 42 ].…”

“…These results may be attributed to differences in the culture media composition, inoculum size, or growth conditions that influence the ability of Streptomyces isolates to secrete different active substances on solid growth surfaces and liquid media [ 8 , 42 ]. Another possible explanation is that some active metabolites discharged by streptomycetes may be destroyed or chemically altered during the solvent extraction process [ 8 , 42 ]. The extraction of the culture filtrate derived from Streptomyces strains using ethyl acetate was utilized broadly to regain powerful secondary metabolites.…”