The rapid development of antibiotic resistance has led to a constant search for and development of new antibiotic drugs. One way to search for antibiotics is to study microorganisms associated with insects [1]. For example actinomycetes isolated as insect symbionts are producers of many antibiotics and antifungal drugs [2].
In this study, samples of the remains of the inner part of spruce bark that was fed on by the bark beetle typographus (Ips typographus) were studied. Preliminary bark samples were washed with sterile water and suspended for inoculation. The inoculum was spread on 9 × 9 cm Petri dishes with solid nutrient medium brain heart infusion (with nystatin 50 μg/mL), potato dextrose (with tobramycin 25 μg/mL), nutrient agar (with nystatin 50 μg/mL), nutrient agar (with nystatin 50 μg/mL and nalidixic acid 30 μg/mL). 46 microbial isolates were isolated. Further, initial screening of antibiotic activity was done using agar diffusion method against a wide range of test microorganisms.
Based on the screening results, 10 isolates of microorganisms with pronounced antibiotic properties were selected for further study. Cultivation in liquid media led to identification of active metabolites by LC-MS for two strains. The production of the known antibiotics trichorozin and gliotoxin was observed for strain SK1-7. Trichorozin is a linear peptide belonging to the peptaibol class. The spectrum of activity of peptaibols is quite broad. Gliotoxin is a sulfur-containing mycotoxin that belongs to the class of natural 2,5-diketopiperazines with a broad spectrum of activity. The production of terreic acid, which is a covalent inhibitor of the bacterial cell wall biosynthetic enzyme UDP-N-acetylglucosamine 1-carboxyvinyltransferase, was produced by the strain SK3-18.
This work was supported by the Russian Science Foundation, project no. 25-14-00281.
- M.I. Hutchings et al., Microbiota and Host 2023, 1, e230008.
- Y. Long et al. BMC Microbiol 2022, 22, 80.
