RESUMEN
Inteins are self-splicing parasitic genetic elements found in all domains of life. These genetic elements are found in highly conserved positions in conserved proteins. One protein family that has been invaded by inteins is the vacuolar and archaeal catalytic ATPase subunits (vma-1). There are two intein insertion sites in this protein, "a" and "b." The b site was previously thought to be only invaded in archaeal lineages. Here we survey the distribution and evolutionary histories of the b site inteins and show that the intein is present in more lineages than previously annotated, including a bacterial lineage, Mahella australiensis 50-1 BON. We present evidence, through ancestral character state reconstruction and substitution ratios between host genes and inteins, for several transfers of this intein between divergent species, including an interdomain transfer between the archaea and bacteria. Although inteins may persist within a single population or species for long periods of time, transfer of the vma-1b intein between divergent species contributed to the distribution of this intein.