Infectious diseases have recently become a serious threat to human health, due to the emergence of multiple drug resistance. The development of new antimicrobial agents has focused on modifying the structures of existing antibiotics and finding new mechanisms of action, as well as finding new antimicrobial agents in extreme and under-researched environments, such as cave ecosystems that offer unexplored genetic and metabolic diversity. Therefore, in the master's thesis we focused on the cave environment, from which we obtained cave samples of sediments, soil, cave milk and clay fillings from wells. We succeeded in isolating cave actinomycetes using selective media and obtaining extracts of secondary metabolites by culturing strains in a production medium. The extracts were used to test antimicrobial activity against selected bacteria Micrococcus luteus, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and yeast Saccharomyces cerevisiae and Candida albicans. We found that 107 strains of isolated actinomycetes produced bioactive substances that inhibited the growth of test microorganisms. Activity against M. luteus was shown by 48% of the extracts, activity against S. aureus by 14% of the extracts, against E. coli by 7% of the extracts, and against P. aeruginosa by 2% of the extracts. Activity against S. cerevisiae showed 11% of the extracts and against C. albicans 5% of the extracts. Isolated strains of actinomycetes that have shown strong antimicrobial activity against Gram-positive and negative bacteria will be involved in further research with the aim of characterizing pure active substance.
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