Evaluation of antimicrobial activities of microorganisms isolated from caves, characterization and purification of natural antimicrobial compounds

In this thesis study, it was aimed to evaluate the antimicrobial activities of microorganisms isolated from caves. Of 170 Gram positive bacterial isolates tested against pathogens, 41 isolates showed activity against at least 1 test organism. It was observed that 12 isolates were effective against 2 test organisms, and 9 isolates were effective against 3 test organisms. Based on the results of extracellular enzyme tests, approximately 58% of isolates with antimicrobial activity exhibited protease activity, 73% showed catalase activity, 39% displayed amylase activity, and 7% had gelatinase enzyme activity. Additionally, 24% of the isolates were found to produce EPS. Three isolates showing activity against both bacterial and fungal isolates were selected for phylogenetic identification, optimization of culture growth parameters, characterization and purification of antimicrobial components. Through sequence analysis, the isolates were identified as Arthrobacter sp. BP-2F-M, Rhodoccoccus erytropolis BP-2G-M, and Streptomyces rubiginosohelvolus BP-K9D-M. Characterization of the antimicrobial effective substance was performed using HPLC analysis and LC-Q-TOF MS analysis. HPLC analysis characterized the extracts obtained from the isolates in terms of various phenolic acids, organic acids and vitamines. According to the results of LC-Q-TOF MS analysis, it was determined that the strains produced the antibiotics streptomycin, kanamycin, oleandomycin, tetracycline quinolone derivatives, erythromycin, azithromycin, Arthrobacilin A, Rhodostreptomycin A. In addition to antibiotics, biotechnologically important compounds such as various siderophores, alkaloids, peptides were detected. Keywords: actinomycetes, antimicrobial activity, natural compunds, HPLC, LC-Q-TOF MS