How to make high titre lambda stock?

[Allison B. MacKay]

I am trying to make a high-titre stock of phage lambda (EMBL3)
in order to generate large working quantities of my genomic
clone.  I have tried plate and liquid lysis protocols from
several sources (mainly Sambrook and Short Protocols) but
only seem to get maximum titres of 10e7 to 10e8 pfu/ml.  The
protocols strongly recommend using stocks of 10e9 to 10e10
pfu/ml to infect larger cultures.  Is there some trick that
I don't know about that will boost the yield?

Allison Mackay
Department of Biology
Queen's University
Kingston, Ontario