DNA translocation across bacterial membranes occurs during the biologi
cal processes of infection by bacteriophages, conjugative DNA transfer
of plasmids, T-DNA transfer, and genetic transformation. The mechanis
m of DNA translocation in these systems is not fully understood, but d
uring the last few years extensive data about genes and gene products
involved in the translocation processes have accumulated. One reason f
or the increasing interest in this topic is the discussion about horiz
ontal gene transfer and transkingdom sex. Analyses of genes and gene p
roducts involved in DNA transfer suggest that DNA is transferred throu
gh a protein channel spanning the bacterial envelope. No common model
exists for DNA translocation during phage infection. Perhaps various m
echanisms are necessary as a result of the different morphologies of b
acteriophages. The DNA translocation processes during conjugation, T-D
NA transfer, and transformation are more consistent and may even be co
mpared to the excretion of some proteins. On the basis of analogies an
d homologies between the proteins involved in DNA translocation and pr
otein secretion, a common basic model for these processes is presented
.