Abstract (eng)
Ever increasing resistance of pathogens to antimicrobial agents, prompts humankind to urgently search for novel natural compounds that may be developed into antibiotics. Soil-dwelling bacteria, especially actinomycetes, are known as producers of more than 66 % of all antibiotics of natural origin, which are currently applied clinically (Barka et al., 2016). Actinomycetes are still worthwhile sources of yet unknown compounds. These bacteria have been mostly isolated from soil samples, but rhizospheres of traditional medicinal plants still remain under-investigated.
In this study we focus on the ancient medicinal plant Leontopodium nivale subsp. alpinum from the native alpine range and its rhizosphere bacteria. Soil samples from the rhizosphere were used to selectively isolate bacteria. Six media selective for rare actinomycetes were combined with soil pre-treatments to eradicate abundant other bacteria, and three antibiotic treatments were applied as additional selective forces. Bacterial colonies were selected based on actinomycetes morphology characteristics and observed bioactivity on agar plates. Isolated bacteria were cultivated and the genomic DNA was extracted. 16S-rDNA was amplified, sequenced and used to construct phylogenetic trees to compare isolates to known type strains.
The majority of the sequenced isolates belongs to the phylum Actinobacteria. Rare actinomycetes included the genera Actinokineospora, Asanoa, Kitasatospora, Microbacterium, Micrococcus, Mycobacterium and Nocardia. Dominating isolates belonged to the genera Streptomyces and Micromonospora. In total, bacteria of 15 different genera were isolated in this project. Furthermore, bioactivity in contact with other bacteria was observed and assigned to several Paenibacillus species and a few Bacillus species.
This work provides a foundation for a future project, aimed at testing these bacteria for the potential production of novel antimicrobial compounds.