Antimicrobial assay and genetic screening of selected freshwater Cyanobacteria and identification of a biomolecule dihydro-2H-pyran-2-one derivative.

AIMS: Explorations of freshwater Cyanobacteria as antimicrobial (bacteria, fungi and methicillin-resistant Staphylococcus aureus (MRSA) strains) drug resource using bioassay, NRPS (non-ribosomal polypeptide synthetase) and PKS (polyketide synthase) genes, as well as in silico approach.

METHODS AND RESULTS: We have bioassayed the extracts of Phormidium CCC727, Geitlerinema CCC728, Arthrospira CCC729, Leptolyngbya CCC732, Phormidium CCC730, Phormidium CCC731 against six pathogenic bacteria comprising Gram (+ve): S. aureus including seven clinical MRSA and Enterococcus faecalis, Gram (-ve): Escherichia coli, Salmonella Typhimurium, Klebsiella pneumoniae and Shigella boydii along with non-pathogenic Enterobacter aerogenes as well as fungal strains (Cryptococcus neoformans and Candida albicans, C. krusei, C. tropicalis and Aspergillus niger) exhibiting antimicrobial potential. The NRPS and PKS genes of the target strains were also amplified and sequenced. The putative protein structures were predicted using bioinformatics approach.

CONCLUSION: PKS gene expression indicated β keto-acyl synthase as one of the important active domains in the biomolecules related to antitumour and antifungal group. The simultaneous identification of the biomolecule (dihydro-2H-pyran-2-one derivative) was also inferred spectroscopically.

SIGNIFICANCE AND IMPACT OF THE STUDY: Freshwater Cyanobacteria are prolific producers of secondary metabolite(s) that may act as the antimicrobial drug resource in addition to their much explored marine counterpart.