Investigation of novel bacteriocin producers of Bacillus thuringiensis and partial characterization of two new bacteriocins: Thuricin 466 and thuricin 4Q7

This study assessed the bacteriocin-producing capability of 140 strains of Bacillus thuringiensis isolated from Qatar. Numerous Bt strains exhibited strong antibacterial activity against both the foodborne pathogen B. cereus and the human pathogen Staphylococcus aureus. This study revealed for the 1st time that Bt strains producing rough spherical crystals synthesize bacteriocins with significantly higher activity levels when compared to strains producing smooth spherical crystals. The primary metabolites identified were thuricin 466, produced by indigenous Bt QBT 466, and thuricin 4Q7, produced by Bt. subsp. israelensis 4Q7. Thuricin 466 exhibited bactericidal effects against S. aureus, whereas thuricin 4Q7 displayed both bactericidal and bacteriostatic properties. Both of these bacteriocins demonstrated broad pH stability. Thuricin 4Q7 exhibited remarkable thermostability. Thuricin 466 was identified as a proteinaceous compound, while thuricin 4Q7 was characterized as a glycoprotein with disulfide bonds. These bacteriocins are promising candidates for industrial applications targeting human pathogenic bacteria and foodborne pathogens.