Phenotypic characterization and genomic analysis of Limosilactobacillus fermentum phage

Limosilactobacillus (L.) fermentum is widely utilized for its beneficial properties, but lysogenic phages can integrate into its genome and can be induced to enter the lysis cycle under certain conditions, thus accomplishing lysis of host cells, resulting in severe economic losses. In this study, a lysogenic phage, LFP03, was induced from L. fermentum IMAU 32510 by UV induction for 70 s. The electron microscopy showed that this phage belonged to Caudoviricetes class. Its genome size was 39,556 bp with a GC content of 46.08%, which includes 20 functional proteins. Compared with other L. fermentum phages, the genome of phage LFP03 exhibited deletions, inversions and translocations. Biological analysis showed that its optimal multiplicity of infection was 0.1, with a burst size of 133.5 ± 4.9 PFU/infective cell. Phage LFP03 was sensitive to temperature and pH, with a survival rate of 48.98% at 50°C. It could be completely inactivated under pH 2. The adsorption ability of this phage was minimally affected by temperature and pH, with adsorption rates reaching 80% under all treated conditions. Divalent cations could accelerate phage adsorption, while chloramphenicol expressed little significant effect on phage adsorption. This study might expand the related knowledge of L. fermentum phages, and provide some theoretical basis for improving the stability of related products and establishing phage control measures.