KSÜ Tarım ve Doğa Dergisi, vol.26, no.6, pp.1277-1290, 2023 (Peer-Reviewed Journal)
Considering that most antibiotics originate from actinomycete group
bacteria, especially the Streptomyces genus, it is predicted that novel
actinomycetes isolated from extreme environments such as caves may
bring novel antibiotics to the medical world. The study aimed to screen
the antimicrobial activity of actinomycetes isolated from the three
karst caves in Türkiye and to identify selected isolates with
antimicrobial activity by molecular methods. One hundred seventynine actinomycetes isolated from Akçakale, Kırklar (Altıntaş), and
Köprübaşı Caves in Gümüşhane province in the Eastern Black Sea
Region of Türkiye were included in the study. The antimicrobial
activity of isolates was investigated using the modified cross-streak
agar method against seven Gram-negative bacteria, three Grampositive bacteria, and one yeast strain. Fifty-three isolates (29.6%) had
antimicrobial activity against at least one of the tested
microorganisms. The rate of isolates exhibiting antimicrobial activity
against Staphylococcus aureus, Bacillus subtilis, Enterococcus
faecalis, Chromobacterium violaceum, Klebsiella pneumoniae,
Salmonella Typhimurium, Escherichia coli, Acinetobacter
haemolyticus, Pseudomonas aeruginosa, Enterobacter aerogenes, and
Candida albicans was 21.2%, 20.0%, 16.8%, 12.8%, 3.4%, 2.8%, 2.2%,
1.1%, 0.6%, 0.6%, and 0.6%, respectively. An actinomycete isolate,
TRMS 124, showed antimicrobial activity against ten test
microorganisms. The 16S ribosomal RNA (16S rRNA) sequencing was
performed for the identification and phylogenetic analysis of 26
isolates randomly selected among actinomycetes that exhibited
antimicrobial activity against at least three test microorganisms. As a
result, it was determined that 24 isolates showed homology with
various Streptomyces species and two isolates with Embleya
scabrispora and Couchioplanes caeruleus, respectively. These results
showed that karst caves could be good sources for isolating
actinomycetes with the potential to produce antimicrobial compounds