Bacteriophage PBC1 and Its Endolysin as an Antimicrobial Agent against Bacillus cereus

ABSTRACTBacillus cereusis an opportunistic human pathogen responsible for food poisoning and other, nongastrointestinal infections. Due to the emergence of multidrug-resistantB. cereusstrains, the demand for alternative therapeutic options is increasing. To address these problems, we isolated and characterized aSiphoviridaevirulent phage, PBC1, and its lytic enzymes. PBC1 showed a very narrow host range, infecting only 1 of 22B. cereusstrains. Phylogenetic analysis based on the major capsid protein revealed that PBC1 is more closely related to theBacillus clarkiiphage BCJA1c and phages of lactic acid bacteria than to the phages infectingB. cereus. Whole-genome comparison showed that the late-gene region, including the terminase gene, structural genes, and holin gene of PBC1, is similar to that fromB. cereustemperate phage 250, whereas their endolysins are different. Compared to the extreme host specificity of PBC1, its endolysin, LysPBC1, showed a much broader lytic spectrum, albeit limited to the genusBacillus. The catalytic domain of LysPBC1 when expressed alone also showedBacillus-specific lytic activity, which was lower against theB. cereusgroup but higher against theBacillus subtilisgroup than the full-length protein. Taken together, these results suggest that the virulent phage PBC1 is a useful component of a phage cocktail to controlB. cereus, even with its exceptionally narrow host range, as it can kill a strain ofB. cereusthat is not killed by other phages, and that LysPBC1 is an alternative biocontrol agent againstB. cereus.

Bacillus taeanensis sp. nov., a halophilic Gram-positive bacterium from a solar saltern in Korea

A halophilic bacterium, strain BH030017T, showing optimum growth at 2–5 % (w/v) NaCl was isolated from solar-saltern sediment from the Tae-An area of Korea and was characterized taxonomically. The cells of strain BH030017T were Gram-positive, motile, short rods containing cell-wall peptidoglycan based on meso-diaminopimelic acid. The major cellular fatty acids were anteiso-C15 : 0 and iso-C15 : 0. The DNA G+C content was 36 mol% and the predominant lipoquinone was MK-7. The major cellular phospholipids were phosphatidylglycerol, diphosphatidylglycerol and phosphatidylethanolamine. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain BH030017T formed a cluster with Bacillus clarkii DSM 8720T and Bacillus agaradhaerens DSM 8721T within the family Bacillaceae. 16S rRNA gene sequence similarities with respect to closely related type strains were less than 95.1 %. On the basis of its phylogenetic, phenotypic and chemotaxonomic properties, strain BH030017T represents a novel species within the genus Bacillus, for which the name Bacillus taeanensis sp. nov. is proposed. The type strain is BH030017T (=KCTC 3918T=DSM 16466T).