Composition of nutrient media and temperature of cultivation imposes effect on the content of secondary metabolites of Nocardiopsis sp. isolated from a Siberian Cave.

Growth of human population leads to many global and medical problems. The problems include the crisis of health, antibiotic resistance, drug discovery, etc. Increasing antimicrobial resistance of microorganisms results in the need to screen natural products (incl. antibiotics and antimicrobial peptides) and their producers in different ecological niches. The purpose of this study was to estimate antibiotic activity and biotechnological potential of rare actinobacteria Nocardiopsis sp. The strain was isolated from Okhotnichya cave located in Siberia. Here, we cultivated the strain at 3 temperature modes (13 °C, 28 °C, 37 °C) in 11 liquid nutrient (rich and poor) media. Using modern assays of liquid chromatography and high-resolution mass spectrometry, we estimated the content and number of produced natural products, distribution of their masses, and potential rate of novel secondary metabolites. We demonstrated that minimal nutrient media with l-asparagine and SM25 media with malt extract were less productive at current experimental parameters. As it was shown, this strain was characterized by antibiotic properties against Bacillus subtilis when cultivated at 28 °C. Also, weak antibiotic activity of crude extracts was found in strain cultivation at 13 °C. Also, we detected a high number of novel amphiphilic and hydrophobic NPs produced by this strain. We demonstrated both the influence of the nutrient media composition and cultivation temperature on biosynthetic capabilities of rare strain Nocardiopsis sp. Finally, high level of natural products that were predicted as novel confirms high biotechnological value of rare genera of Actinobacteria that could be explained by the evolution of microorganisms in the isolated environment of cave ecosystem.

Estimation of antimicrobial activities and fatty acid composition of actinobacteria isolated from water surface of underground lakes from Badzheyskaya and Okhotnichya caves in Siberia.

Extreme and unusual ecosystems such as isolated ancient caves are considered as potential tools for the discovery of novel natural products with biological activities. Actinobacteria that inhabit these unusual ecosystems are examined as a promising source for the development of new drugs. In this study we focused on the preliminary estimation of fatty acid composition and antibacterial properties of culturable actinobacteria isolated from water surface of underground lakes located in Badzheyskaya and Okhotnichya caves in Siberia. Here we present isolation of 17 strains of actinobacteria that belong to the Streptomyces, Nocardia and Nocardiopsis genera. Using assays for antibacterial and antifungal activities, we found that a number of strains belonging to the genus Streptomyces isolated from Badzheyskaya cave demonstrated inhibition activity against bacteria and fungi. It was shown that representatives of the genera Nocardia and Nocardiopsis isolated from Okhotnichya cave did not demonstrate any tested antibiotic properties. However, despite the lack of antimicrobial and fungicidal activity of Nocardia extracts, those strains are specific in terms of their fatty acid spectrum. When assessing fatty acid profile, we found that polyunsaturated fatty acids were quantitatively dominant in extracts of Nocardia sp. and Streptomyces sp. grown in different media. Saturated fatty acids were the second most abundant type in the fatty acid profile. It was due to palmitic acid. Also, a few monounsaturated fatty acids were detected. The obtained materials can become a basis for development of approaches to use bacteria isolated from caves as a biological sources of bioactive compounds to create medical and veterinary drugs.

Actinobacteria Isolated from an Underground Lake and Moonmilk Speleothem from the Biggest Conglomeratic Karstic Cave in Siberia as Sources of Novel Biologically Active Compounds.

Actinobacteria isolated from unstudied ecosystems are one of the most interesting and promising sources of novel biologically active compounds. Cave ecosystems are unusual and rarely studied. Here, we report the isolation and characterization of ten new actinobacteria strains isolated from an ancient underground lake and moonmilk speleothem from the biggest conglomeratic karstic cave in Siberia with a focus on the biological activity of the obtained strains and the metabolite dereplication of one active strain. Streptomyces genera isolates from moonmilk speleothem demonstrated antibacterial and antifungal activities. Some of the strains were able to inhibit the growth of pathogenic Candida albicans.