Today we can identify several consortia of key players that coordinate and organize the genetic content compositions of host organisms: endogenous viruses and defectives, transposons, retrotransposons, long terminal repeats, nonlong terminal repeats, long interspersed nuclear elements, short interspersed nuclear elements, group I introns, group II introns, phages, and plasmids are currently investigated examples that use genomic DNA as their preferred living habitat.
Source: wiktionary