Differential Function of the Tail Fiber Proteins and Receptor Binding Protein on Host Specificity of Bacteriophage SCB3

Abstract

Bacteriophage which can infect specific bacteria has emerged as a new tool to control various food-borne pathogens. A novel bacteriophage SCB3 targeting Salmonella enterica serovar Typhimurium was isolated from chicken skin. Morphological analysis revealed that phage SCB3 belongs to the Siphoviridae family. The genome of phage SCB3 consists of 108,773-bp nucleotides excluding terminal redundancy with 153 open reading frames (ORFs). Additional phylogenetic analysis revealed that phage SCB3 is classified as T5-like phage. Interestingly, phage SCB3 could infect only rough strains which do not have O-antigen of lipopolysaccharides even though BtuB (the vitamin B12 uptake outer membrane protein) is used as a host receptor. Comparative genomic analysis of phage SCB3 with other T5-like phage SPC35 revealed that the specificity to rough strains of phage SCB3 may be associated with tail fiber genes. Swapping of the tail fiber gene of phage SCB3 with that of phage SPC35 enabled phage SCB3 to infect wild type Salmonella, suggesting that the tail fiber protein is involved in the interaction of phage with O-antigen. These results indicate that phage tail fiber protein may play an ancillary role in infection of bacteria by phages using BtuB as a receptor. Therefore, it experimentally supports that tail fiber protein of phage SCB3 is one of the major determinant for host specificity, along with the receptor binding protein.