Plasmid profiles and curing of plasmids in Lactobacillus plantarum strains isolated from green olive fermentations.

Plasmid profiles of 35 Lactobacillus plantarum strains isolated from different green olive fermentors were obtained. A large number of plasmids in the CCC form (from 5 to 16) were present in all the tested strains as confirmed by a second dimension electrophoresis of DNA. These plasmids, all of which remain cryptic, ranged from 2.0 to 68 kb in size. Novobiocin, sodium dodecyl sulphate and ethidium bromide were used as plasmid-curing agents but only novobiocin induced loss of extrachromosomal DNA at a high frequency in these strains.