Changes in the plasmid profile of Lactobacillus plantarum obtained from commercial meat starter cultures

The stability of plasmids in Lactobacillus plantarum used commercially as a starter culture in the production of dry sausage was studied. Individual isolates of one strain taken from the starter culture produced over a period of 10 years were examined, and certain changes in the plasmid profiles identified. From molecular sizing and restriction enzyme analysis it appeared that two of the six plasmids became fused over this period of time to give one new, larger plasmid. The other plasmids remained unchanged.