Characterization of a novel bacteriophage PS1 targeting Bacillus licheniformis for biocontrol application in dairy products

Abstract

Bacillus licheniformis, a major food spoilage bacterium, presents significant challenges to food safety due to its robust survival in harsh environments, its role in causing foodborne illnesses, and its negative impact on product shelf life. Current control methods like pasteurization and the use of antibiotics often compromise food quality and contribute to antibiotic resistance, highlighting the need for more effective strategies. In this study, a novel bacteriophage (phage), PS1, specifically infecting B. licheniformis was isolated from environmental samples. PS1 demonstrated a narrow host range, lysing only B. licheniformis strains among the various bacterial strains tested. Furthermore, lysis was maintained for at least 16 h post-infection at multiplicities of infection ranging from 1 to 0.0001 in vitro. The phage PS1 showed excellent stability in a wide range of pHs (pH 5–11), temperatures (4–65 °C), and NaCl concentrations (0–1000 mM). Bioinformatic analysis revealed that the genome of PS1 consists of a 48,817 bp double-stranded linear DNA with 71 open reading frames. Phage PS1 is predicted to lack genes associated with toxins, virulence factors, antibiotic resistance genes, or lysogeny-related elements, supporting its safety for food applications. Additionally, PS1 effectively inhibited the growth of B. licheniformis in milk for 24 h at room temperature (22–25 °C) and 30 °C. To our best knowledge, this is the first report demonstrating a lytic phage infecting B. licheniformis. These findings suggest that the novel phage PS1 could serve as an effective biological control agent and an alternative to antimicrobials for controlling B. licheniformis in dairy products.