Evaluation of the bioactive potential of polar cyanobacterial strains

Abstract

Antibiotic and antifungal resistance has become a major public health problem worldwide, with significant clinical and economic consequences. It is therefore imperative to take rapid and sustained action over the coming years to tackle this situation. Cyanobacteria, oxygenic photosynthetic prokaryotes, offer promising potential in many fields such as pharmaceuticals, biotechnology, cosmetics, food, and many others. Previous research has identified numerous strains capable of producing antimicrobial compounds. These could represent a new avenue of research in the fight against the emergence of drug resistance. As part of this thesis, an evaluation of 41 polar cyanobacterial strains from the BCCM/ULC Collection was undertaken to study their activity against pathogenic bacteria and fungi. In addition, a molecular analysis was carried out to determine their genetic potential to produce cyanotoxins and protease-inhibiting peptides, enabling us to better characterize their safety or potential usefulness in other clinical fields. The results of this study highlighted the strains Phormidesmis priestleyi ULC007 and Microcoleus attenuatus ULC371, whose methanolic extracts demonstrated significant antifungal activity against Candida albicans and Aspergillus fumigatus. The study also revealed the presence of the mcyE gene, involved in microcystin biosynthesis, in Nostoc spp. strains ULC008, ULC399 and ULC447. It also revealed the presence of a specific intergenic region between the mcnC and mcnE genes, involved in cyanopeptolin biosynthesis, in the strain Wilmottia murrayi ULC376. These results open up new prospects for further research aimed at isolating and identifying the compound(s) responsible for the observed antifungal activity. They also deepen our understanding of the biosynthetic potential of microcystin and cyanopeptolin in these strains. These advances could eventually lead to the development of promising new therapeutic applications.