The genome of Lactobacillus phage 3-521 the exemplar isolate of Watanabevirus wv3521, the only species in the genus, is 140 816 bp with 155 predicted protein coding sequences and 14 tRNAs. Terminal repeats have not been located (Feyereisen et al., 2019). The only known member of the genus infects Lactobacillus brevis.
Species demarcation criteria
There is only one species in the genus. New members of this species will be assigned based on their being more than 95% identical in genome nucleotide sequence, including the terminal repeat region. Phages with genomes that differ by more than 5% will be assigned to different species.