CRYPTIC PLASMIDS FROM LACTOBACILLUS-HELVETICUS AND THEIR EVOLUTIONARYRELATIONSHIP

Three different cryptic plasmids from Lactobacillus helveticus have be en identified and their DNA sequences determined. Analyses and compari sons of their primary structures revealed stretches of DNA with consid erable homology. Thus, large portions of the plasmid non-coding sequen ces were conserved at 80-90% identity between the different plasmids i dentified so far in L. helveticus. Nevertheless, different plasmids fo und in a same host strain utilise different genes of replication, prob ably acquired during evolution from different replicons from Gram-posi tive bacterial origins. A remnant structure of such a possible genetic integration of a foreign replication gene into one of the plasmids of L. helveticus was identified.