Özet:

Objective: Recent studies have revealed the biodiversity of both cultivated and uncultivated microbiomes in extreme environments. It has been shown that terrestrial subsurface ecosystems contain vast metabolic potential. Heterotrophic bacteria living in karst caves with an organic substrate deficit represent a special reserve for the isolation of metabolite producers. Here, we cultivated a bacterial community collected from biofilms in Kapova Cave (Shulgan–Tash Nature Reserve, Bashkortostan), and assessed its ability to synthesize secreted hydrolytic enzymes including RNases, proteases, and amylases. Materials and Methods: Isolated bacteria were identified by V3-V4 16S rRNA region sequencing. Enzymatic activities were assessed by measuring transparency zones around colonies grown on the appropriate substrate (RNA, casein, starch). Functional profiles of the communitieswere predicted using the Global Mapper module on iVikodak. Taxonomic, structural, and compositional diversity were calculated using Shannon–Wiener and Bray–Curtis indices. Results: Eighty-nine percent of 102 bacterial isolates were Proteobacteria, whereas other isolates were divided into three other phyla, Actinobacteria, Firmicutes, and Bacteroidetes that comprised 5%, 4%, and 2% of the isolates, respectively. Genus Pseudomonas was predominant with 42 isolates. Six isolates showed no extracellular enzymatic activity at all, 73 isolates expressed protease, 57 isolates expressed amylase, and 71 isolates had RNase activity. All three extracellular enzymes were expressed by 39isolates. Conclusion: The biodiversity of cultivated microbiota from Kapova Cave was characterized. Bacteria that produce large amounts of protease, RNase and amylase were identified as Stenotrophomonas rhizophila, Lysinibacillus fusiformis, and Pseudomonas stutzeri, respectively.

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