Methods are provided for preparing improved fermentation strains of the family
Enterobacteriaceae which comprise the steps of eliminating the cryptic plasmid
from the progenitor strain thereby creating the improved strain. Methods for reducing
the mobilization properties of resident plasmids in an Enterobacteriaceae strain
containing a cryptic plasmid are also provided. The present invention provides
the nucleic acid sequence of pS, a cryptic plasmid found in Pantoea which
can be used to identify the cryptic plasmid in strains of Enterobacteriaceae.
