Retroelements in bacteria.

A peculiar type of satellite DNA, called msDNA, has been discovered in myxobacteria and some natural isolates of E. coli. These molecules are characterized by the presence of single-stranded DNA branching out from an internal guanosine residue of an RNA molecule by a unique 2',5'-phosphodiester linkage. Reverse transcriptase is required for the synthesis of msDNA. The discovery of retroelements in bacterial populations raises many intriguing questions concerning the evolutionary origin of reverse transcriptase, the function and the biosynthesis of msDNA, and the nature of the mechanisms generating the extensive diversity found in msDNA and reverse transcriptase genes among different bacterial strains.