Three different Bacillus bacteriophages designated TP21 are known from the literature. We have determined the sequence and structure of the TP21-L genome, and compared it to the other phages. The genome is 37.5 kb in size, possesses fixed invariable genome ends and features the typical modular organization of a temperate siphovirus. TP21-L is neither identical to TP21 isolated by Thorne (TP21-T), as shown by a PCR-based approach nor to TP21 isolated by He et al. (TP21-H), as estimated from phage dimensions. For reasons of clarity, we suggest renaming the different TP21 isolates.
Klumpp, J., Calendar, R., & Loessner, M. J. (2010). Complete nucleotide sequence and molecular characterization of Bacillus phage TP21 and its relatedness to other phages with the same name. Viruses, 2(4), 961–971. https://doi.org/10.3390/v2040961