Isolation and curing of the Klebsiella pneumoniae large indigenous plasmid using sodium dodecyl sulphate.

The ability of Klebsiella pneumoniae (NCTC, CL687/80) to produce and, in turn, excrete glutamate has been equated with the presence of a large indigenous plasmid with an apparent molecular mass in the region of 96 +/- 2 kbp (n = 6). Unlike mitomycin C, novobiocine and ethidium bromide (curing agents), the use of sodium dodecyl sulphate (SDS) proved very effective in curing the plasmid with a relatively high frequency (6.25 x 10(-4)). Furthermore, the absence of isocitrate dehydrogenase (ICDH) activity in the cured strain strongly suggests that the structural gene encoding ICDH in this organism, in sharp contrast to all known ICDHs, is plasmid-encoded. Moreover, the SDS-based protocol reported for the isolation of the K. pneumoniae indigenous plasmid has proven successful with other organisms including Pseudomonad and Corynebacteria, as well as in recombinant strains of Escherichia coli.