Antimicrobial activity of two Antarctic Streptomyces strains

Abstract

Aims:The search for new antibiotics is an ongoing effort and has expanded to pristine niche areas in the Antarctic in recent years due to the emergence of multi-drug resistant pathogens that outpaced the discovery of new antibiotics. We have recently isolated two new actinomycetes strains, INACH3013a and INACH3013b, which displayed antimicrobial properties from soil samples collected from Ardley Island, Antarctica. Hence, an investigation was carried out to identify them and to characterise the antimicrobial compounds produced. Methodology and results: Strains, INACH3013a and INACH3013b were identified based on their 16S rDNA sequence alignment to those in the GenBank. The results showed that strain INACH3013a was closest to Streptomyces spp. while strain INACH3013b was closest to Streptomyces corallincola and Streptomyces bullii. The extracellular compounds they produced were extracted using various solvents and the extracted compounds were tested against the test pathogens. The dichloromethane extracts from strains, INACH3013a and INACH3013b inhibited mainly Gram-positive pathogens that include Listeria monocytogenes, Staphylococcus aureus, Staphylococcus haemolyticus, Staphylococcus equorum, Bacillus cereus K3 and Enterococcus faecalis while extracts from strain INACH3013b also inhibited a Gram-negative pathogen, Klebsiella pneumonia 14x. Predominantly non-polar constituents seem responsible for antibacterial effects, with dichloromethane extracts proving most efficacious, followed by chloroform and ethyl acetate. Conclusion, significance and impact of study: The research highlights the potential of Streptomyces spp. INACH3013a and INACH3013b as a source of potential novel antibiotics. This research explores Antarctic Streptomyces strains' antimicrobial capabilities, enabling the potential for the discovery of novel antibiotics and revealing how these compounds may have helped them to compete and survive in nutrient-deficient Antarctic niches.