Detection of same sized 4.3 Kb extrachromosomal DNA elements in weakly beta-haemolytic human intestinal spirochaetes and Serpulina pilosicoli of swine origin

Agarose gel electrophoresis of total DNA from Italian strains of weakly bet a-haemolytic human intestinal spirochaetes (w beta HIS) and porcine Serpuli na pilosicoli reference strain P43/6/78 showed an extrachromosomal band hav ing the same size and migrating at 4.3 Kb. The same results were observed a fter agarose gel electrophoresis of DNA obtained from the supernatant fluid s of the spirochaetal cultures analysed. Swine Serpulina hyodysenteriae ref erence strain P18A was comparatively analysed and a 6.5 Kb extrachromosomal DNA element was found, as expected. Furthermore, S. hyodysenteriae referen ce strain P18A differed from all the other spirochaetes tested and had a hi gher number of flagella (8-12) at each cell end and was strongly beta-haemo lytic. To the best of our knowledge, this is the first report on the detect ion of a band of extrachromosomal DNA having the same size in w beta HIS an d S. pilosicoli from swine origin.