Culture dependent analysis of bacterial diversity in Canada’s Raspberry Rising Cave revealed antimicrobial properties

Bacteria and archaea thrive in terrestrial subsurface environments because of their unique physiology. Over time, these unique microorganisms may have adapted to possess specialized metabolic pathways that sustain their continued existence in caves, one of harshest environments on earth. The present study elucidates cultivation based microbial diversity of the cave sediments and wall scrapings collected from seven different locations in Raspberry Rising Cave located in the Columbia Mountain Range, British Columbia, Canada. A total of 103 cultivable bacteria from the cave were isolated on various agar media including R2A, Hickey-Tresner, and DifcoTM Actinomycetes Isolation agar media. Taxonomical phylogenetic analysis of the 16S rRNA gene of the bacterial isolates identified three major phyla: Proteobacteria (Class: Gammaproteobacteria) (51.45%), Actinobacteria (43.68%) and Bacteroidetes (3.88%). Among them, the major genus was Pseudomonas (48.54%) followed by Rhodococcus (39.80%) and Flavobacterium (3.88%). The genus Janthinobacterium and Arthrobacter contributed about 2.91% each, of the total population. Noteworthy, 0.99% were recognized as endophytic Proteobacteria. Furthermore, these bacterial isolates were evaluated for their potential antimicrobial activities against the multidrug resistant bacterial strains. Two bacterial isolates (RRC23, RRC75) showed antimicrobial activities against multi-drug resistant (MDR) Escherichia coli #15-318 while RRC48 exhibited against methicillin resistant (MRSA) Staphylococcus aureus. The isolates RRC36 and RRC38 were identified to show antimicrobial activities against non-pathogenic isolates of Staphylococcus aureus. To the best of our knowledge, this is the first scientific study conducted and provides the insight in occurrence and distribution of the cultivated bacterial diversity from the Raspberry Rising Cave. Moreover, the antimicrobial properties exhibited by some of the bacterial isolates suggested that this cave system could be a resource for potential antibiotics, drugs or novel biologics of clinical relevance