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 Bacillus phages, B450T and B450C, isolated from Bacillus thuringiensis 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 Bacillus cereus sensu lato strains, with B450C showing enhanced lytic activity due to mutations in the repressor protein. PlyC19 lysed 56% of the strains tested, including Priestia flexa, 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 Bquatquinnuvirus eskimopiis 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 Bacillus cereus group strains in food safety and medicine.