Transposable Mu-like phages in Firmicutes: new instances of divergence generating retroelements

SglyMu-1 appears to carry a host variation system related to the DGR tropism switching retroelements, first characterized in Bordetella phages BPP-1, BIP-1 and BMP-1. Transposable phages are thus thriving among Firmicutes and can harness either of two host variation systems, the fiber genes inversion and reverse transcriptase-mediated site-directed, adenine-specific mutagenesis.