Novel Bacillus-Infecting Phage Bquatquinnuvirus eskimopiis (Strains B450T and B450C), Founder of a New Genus, and the Properties of Its Endolysin

This study characterizes two novel <i>Bacillus</i> phages, B450T and B450C, isolated from <i>Bacillus thuringiensis</i> VKM B-450 via mitomycin C induction, along with their endolysin, PlyC19. Both phages, siphoviruses with 41,205 bp genomes, lysed 38% of the tested <i>Bacillus cereus</i> sensu lato strains, with B450C showing enhanced lytic activity due to mutations in the repressor protein. PlyC19 lysed 56% of the strains tested, including <i>Priestia flexa</i>, demonstrating broader efficacy. Its Amidase_2 domain and dual SH3 cell wall-binding domains enable targeted peptidoglycan hydrolysis, with optimal activity at pH 9.0 and thermal stability up to 40 °C. We propose the taxonomic designation <i>Bquatquinnuvirus eskimopiis</i> for these phages, with B450T and B450C representing distinct strains, based on genomic divergence in the repressor protein's HTH_Xre domain, consistent with their turbid and clear plaque morphologies, respectively. PlyC19's broad specificity underscores its potential as an enzybiotic against multidrug-resistant <i>Bacillus cereus</i> group strains in food safety and medicine.