LPS, P. multocida and restriction digests

Michael F. Hynes hynes at acs.ucalgary.ca
Wed Mar 8 16:49:37 EST 1995

In article <3jjh78$gc at styx.uwa.edu.au>, Kirsty Townsend wrote:

> Dear Fellow Micro-Netters,
> I'm hoping someone out there can help me, because I'm having huge problems
> with restriction digests of particular strains of Pasteurella multocida.
> They are known to have a high LPS content in the cell wall, but I thought
> I was allowing for that during the million ether extractions. But the DNA
> I get at the end of it all, will cut with Eco RI but not with Pst I. I
> have tried using increased enzyme concentrations, different buffer etc

> Thanks in advance,
> Kirsty Townsend

We had a similar situation with one of our strains of Rhizobium leguminosarum
where we we couldn't cut the DNA with Pst.  It turned out that that strain
(and that strain alone) carried a plasmid which had on it a gene coding
for a methylase that protected PstI sites from digestion.  We have cloned
enzyme and the associated restriction enzyme by a methylase protection 
procedure.  If your DNA cuts with EcoRI and a large number of other enzymes
but not with Pst, I would suggest that you probably also have a methylase.
The best solution is probably just to use other enzymes in the meantime.

Michael Hynes

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