3D Structure Elucidation and Appraisal of Mode of Action of a Bacteriocin BaCf3 with Anticancer Potential Produced by Marine Bacillus amyloliquefaciens BTSS3

In the world of intense usage of antibiotics, the emergence of antimicrobial resistance necessitates research on alternative forms of antibiotics, antimicrobial peptides (AMPs), which are least known to induce resistance. The partial sequence of bacteriocin BaCf3, produced by marine Bacillus amyloliquefaciens BTSS3, derived from Matrix Assisted Laser Desorption Ionisation - Time of Flight Tandem Mass Spectroscopy (MALDI-ToF MS/MS) data was analyzed for amino acid composition and modelled in silico using TrRosetta. The mechanism of action of BaCf3 was studied in vitro on B. circulans NCIM2107 cell wall using microscopic techniques, such as confocal laser scanning microscopy, scanning electron microscopy, and high resolution transmission electron microscopy. Docking studies with cancer markers, glucose transporter protein, and mesenchymal-epithelial transition factor (MET) receptor tyrosine kinase were also conducted. BaCf3 was found to be rich in glycine and hydrophobic in nature, a characteristic property of cell wall acting AMPs. The structure of BaCf3 obtained from TrRosetta had antiparallel b-sheets resembling Laterosporulin. The bacteriocin BaCf3 has been found to act on the cell membrane of opportunistic pathogen Bacillus circulans, causing permeabilization and pore formation by dissipating the membrane potential. The microscopic examination also proved the mode of action of BaCf3 as cell wall acting. In silico docking studies with anticancer target proved that bacteriocin BaCf3 is also a possible anticancer drug candidate. In vitro anticancer assays such as 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and acridine orange/ethidium bromide dual staining on lung carcinorma cell line A549 further prove the anticancer activity of the bacteriocin.