Microbial communities of underwater caves from Algarve coast: Biological activities prospection

Abstract

Microorganisms are known to be an important source of bioactive compounds. Lately, the microbiota of hypogenic environments, such as underwater caves, has been explored, since they constitute complex ecosystems, which bring unique conditions for the development of organism’s niches with unknown biodiversity. These microorganisms may have interesting characteristics regarding the high potential to produce new bioactive compounds with antitumoral, antioxidant, antimicrobial and pesticide properties, with potential application in Cultural Heritage safeguarding [1-2]. This study under the PROBIOMA project aims to search for new bioactive compounds produced by bacterial cultures, isolated from marine caves. Samples were collected in two underwater caves on the Algarve coast and microbial biodiversity was assessed by High-throughput sequencing and cultivable microorganisms were isolated on marine agar medium 2216 [3]. Metagenomics showed mostly bacteria from the Proteobacteria, Bacteroidetes and Firmicutes phyla. DNA of 269 selected bacterial isolates was extracted and the identification was performed by sequencing 16SrDNA. Antimicrobial spectra of metabolites produced by selected isolates (Brevibacterium sp., Pseudoalteromonas sp., Vibrio sp., Cobetia sp., Cellulophaga sp., Tenacibaculum sp., Bacillus sp., Mesonia sp., Rhodobacteraceae sp., Agarivorans sp. and Sulfitobacter sp.) was evaluated in solid and liquid media against bacterial strains of Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli and Pseudomonas aeruginosa, and in solid medium against biodeteriogenic fungi Mucor sp., Aspergillus niger, Fusarium oxysporum, Cladosporium sp., and two Penicillium sp.. On the other hand, supernatants of cultures from selected isolated bacterial strains were screened for evaluation of antitumor potential against breast cancer epithelial cell line MDA MB 231[4]. Direct supernatants (without prior concentration) did not show significant antifungal action against the selected fungal strains. However substantial antibacterial activity was observed in direct supernatants of Brevibacterium sp., Pseudoalteromonas sp., Vibrio sp. and Sulfitobacter sp.. Aditionally several supernatants of selected strains showed high antiproliferative activity against this breast tumour cell line, namely Sulfitobacter, Cobetia and Pseudoalteromonas. Overall, there were some very promising results concerning the prospection of new biocompounds with biological properties obtained from microbial communities of underwater caves from Algarve coast, constituting new potential for green-safe and sustainable solutions and representing an opportunity for the valorization of these Natural, Genetics and Cultural Heritage. Keywords: Natural, Genetics and Cultural Heritage; Underwater caves; hypogenic environments; Microbiota; Biological compounds; Green-safe and sustainable solutions Acknowledgements: The research was supported by the European Union’s project 0483_PROBIOMA_5_E, co-financed by the European Regional Development Fund within the framework of the Interreg V-A Spain-Portugal program (POCTEP) 2014–2020. The authors acknowledge to FCT – Foundation for Science and Technology, I.P., within the scope of the projects UIDB/04449/2020, MICROCENO (PTDC/CTA-AMB/0608/2020), ART3mis (2022.07303.PTDC) and C. Salvador (DL 57/2016/CP1372/CT0019) to individual support.

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