BacterioPhage M13??

Jesper S. Pedersen jsp at
Thu Jul 27 06:28:38 EST 2000

I've been working with a phage-display project for a long time now using a
ampicilin-resistant phagemid and Kanamycin-resistant helperphage.

I use a special kind of Helper Phage, but either it is mutating or I have a
contamination of another kind of helper phage. I grow my Tg1 to an OD of
about 0,5 and infect with my phage repertoire. When I count the cfu (using
dilution series) on ampicilin and canamycin plates I get around the same
amount - e.g. : 5e12 on ampicilin and 3e12 on canamycin. This could indicate
that around half of the plasmids rescued are (helper-)phagemids.

My question is: Can the bacteria (not resistant to ampicilin) produce
helperphage (only resistant to kanamycin) when grown in rich media
containing ampicilin, or is this process blocked immediately?? I've been
told that ampicilin disrupts the membranes of the bacteria - but is that
enough to stop a bacteria containg a phagemid from producing phage ? Can
anyone tell me more about this?

Hope someone can answer this..

Cheers Jesper.

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