lysogenic phage plaques

Don Walthers genejcky.removethis at yahoo.com
Wed Apr 11 14:03:08 EST 2001

P22 produces plaques with turbid centers because the rare lysogens that form
under conditions that favor lytic growth no longer have to compete with
nearby cells for nutrients. In addition, as the MOI rises in the center of
the plaque, any remaining uninfected cells are more likely to become
lysogens. P22 c2 mutants produce plaques with clear centers and turbid
peripheries because lysis requires rapid cell metabolism. As the bacteria
form a saturating lawn, growth slows. So maybe lambda has a lower frequency
of lysogeny that P22 and/or lysogens are less stable? Someone else probably
has a better answer.

Don Walthers, PhD genejcky @ yahoo com
Dept of Molecular Microbiology
Oregon Health Sciences University
Portland OR
Our gene pool needs a little chlorine.
> In a standard plaque assay for the quantification of a lambda phage
> the plaques formed after an overnight incubation appear as circles with a
> clear center and a turbid periphery where grow of lysogenic bacteria is
> clearly visible. In turn, when the plaque assay is performed with P22
> plaques appear with a turbid center (growth of lysogens) and a clear
> periphery. Does anibody know the reason of these differences in plaque
> appearance?
> Thanks in advance!

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