size of colonies - (Apr/16/2007 )

I found the size of colonies are quite different when I picked them from my Kanamycin plate.
Why are the differences if they were plated at the same time (the same plate) and supposed to be of the same strain?
Thanks!

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Pick the large ones without a lot of satellite tiny colonies around them. The longer the colonies grow, the more of the antibiotic they use up, allowing non-resistant bacteria to grow around them. These non-resistant ones start growing later, so should appear a lot smaller than ones still carrying your plasmid.

Cheers,
Anil

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The satellite colonies are characteristic of ampicillin as an antibiotic, but not kanamycin. The kanamycin colonies are different sizes because some cells are growing faster than others. Often the small colonies contain the plasmid you are interested in, while the large ones contain an empty vector. Pick a variety of sizes to analyze further.

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Thank you, Anil.
And Thank you, phage!
I am going to try to pick the smaller ones while I used to pick the larger ones.

And I am wonder if the Topo10 competent cells (Invitrogen) are resistant to lethal protein?
And how ablout XL1 blue supercompetent cells from Statagene?
Thank you!

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I noticed both strains will die when exposed to vectors with a functional ccdB gene.
We use therefore the pZERO vector of invitrogen.

I thought that on kanamycin the satalytes were found, because it's less stable. So, thanks for your advice!

(forgive me my grammar please!)

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