Isolamento e caracterização de bactérias associadas à briófitas na Antártica

Abstract

Antarctica, due to its environmental conditions, constitutes a unique setting for the study of organisms adapted to extreme environments. Although numerous bacteria have been obtained from soil samples across the continent, limited information is available regarding the microbiota associated with its native vegetation. In this context, the present study aimed to isolate slow-growing bacteria associated with the bryophyte Sanionia uncinata, with special emphasis on members of the phylum Acidobacteriota. Samples were collected on King George Island during the austral summer of 2025, and the gametophytes were kept frozen until arrival at the laboratory. The gametophytes were subsequently thawed and subjected to vortex-assisted washing procedures in saline solution to promote the release of associated microorganisms. The resulting suspensions were inoculated onto selective VL-55 medium containing xylan as a carbon source, developed for the cultivation of bacteria adapted to oligotrophic growth conditions. The samples were incubated for up to four months under controlled temperature conditions and in the absence of light.From the mixed cultures, isolation was performed using the streak plate method, and pure cultures had their DNA extracted for molecular identification based on 16S rRNA gene sequencing, obtained through polymerase chain reaction using the universal primers 27F and 1492R. Sequence analysis of six isolates revealed similarity to species belonging to the phyla Proteobacteria, Firmicutes, and Actinobacteriota, with no representatives of the phylum Acidobacteriota being detected. Phylogenetic analysis confirmed that the isolates were closely related to Lysinimonas soli (isolate 1b), Sphingomonas sp. P5-21 (isolates 3a and 3ar), and Paenibacillus baekrokdamisoli (isolates 5a, 5b, and 5c). Both the environmental origin and the phenotypic characteristics described for the closest related species were consistent with those observed for the isolates obtained in this study. However, these data were not sufficient to discriminate the isolates from their closest relatives, thereby limiting species-level identification.