Extracellular DNA from Serpulina hyodysenteriae consists of 6.5 kbp random fragments of chromosomal DNA.

Preparations of chromosomal DNA from a number of Serpulina hyodysenteriae strains have shown, using agarose gel electrophoresis, the presence of an additional band with a mobility similar to that of a 6.5 kbp linear DNA fragment. Analysis showed that this is not a plasmid but rather a form of extracellular DNA like that observed for Gram-negative bacteria. However, unlike the extracellular DNA from Gram-negative bacteria, which showed a similar band profile to that of the DNA from whole cells, that from S. hyodysenteriae consisted primarily of fragments of a fixed 6.5 kbp.