Abstract
The complete genome sequence of Lactobacillus temperate phage ΦA3 was established. Its genome of double-stranded DNA is composed of 39,165 bp, has 44% G+C. The main coding strand contains 50 putative open reading frames (ORF), while as the complementary strand has 3 ORFs, and genome organization is similar to that of other Siphoviridae. Bacteriophage ΦA3, was induced from Lactobacillus casei ATCC ATCC 393 by mitomycin C treatment of the cells. The phage had an isometric head of 45 nm in diameter, and about 200 nm non-contractile tail long and 8 nm wide. Homology analysis was used to assign putatively function for the genes. Phylogenetic analysis and sequence comparisons showed that ΦA3 is closely related to sfi21-like phages. Additionally, ΦA3 encodes ClpP protease (ORF 5), its Ser83、His106 exactly at the position of the catalytically active residues. CI and Cro, the helix-turn-helix motif of CI and Cro were detected, implicated that two protein were the DNA-binding protein.