• The first analysis of antimicrobial activity of bacteria isolated from Krubera-Voronja Cave.
  • The first report on chemical characterization of antimicrobial mixtures of Firmicutes isolated from caves.


In the present study we aimed to perform the first analysis of antimicrobial activity of bacteria isolated from Krubera-Voronja Cave, with the main focus on their activity against Grampositive bacteria, including Gram-positive pathogens. Using five different media, in total 874 heterotrophic cultures were isolated from water and sediment samples collected in Krubera-Voronja Cave at a depth from 220 m to 1640 m. 14.0% of all isolates demonstrated antibacterial activity against Gram-positive and Gram-negative test microorganisms. Our results show that this percentage was not uniform; it increased with the sampling depth and was the highest in the lower part of the cave. 24 isolates were active exclusively against Gram-positive test strains Micrococcus luteus and Bacillus thuringiensis. Two isolates, namely strains 1350R2-TSA30-6 and 1410WF1-TSA30-2, were chosen for the further work because of the high and comparable activity against both Gram-positive test microorganisms. It was determined that both strains belong to the family Bacillaceae in phylum Firmicutes. The detailed bioactivity analysis of these two Gram-positive strains revealed the different mixtures of volatile compounds with antibacterial activity. The main antibacterial compounds of the strain 1350R2-TSA30-6 are pyrrolopyrazines pyrrolo[1,2-a]pyrazine-1,4-dione, hexahydro- 3-(2-methylpropyl)- and pyrrolo[1,2-a]pyrazine-1,4-dione, hexahydro-3-(phenylmethyl)-. The main antibacterial compound of the strain 1410WF1-TSA30-2 is 1,2-benzenedicarboxylic acid, bis(2-methylpropyl) ester. Mixtures of the volatile antimicrobial compounds of both strains were antagonistic against Gram-positive strains isolated from Krubera-Voronja Cave, and their activity against Gram-positive pathogenic bacteria substantially differed.



Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License

Table 2.pdf (100 kB)
Table 2

Table 3.pdf (107 kB)
Table 3