X-Message-Number: 15082
Date: Wed, 06 Dec 2000 16:25:32 +1100
From: Damien Broderick <>
Subject: Petri dish antics

Forgive this quibbly question. Bill Walker sez:

>If you have a bacterium that 
>doubles in number every day in a petri dish and it takes 10 days to 
>completely cover the dish - then on the last day, the petri dish is still 
>only 50% covered! 

It's always been a nice image, but is it true? I've never grown bugs on
glass or plastic, but intuition tells me they can only readily spread from
the circumference of their territory (unless they send spores jumping out
through the third dimension). Once they've eaten their substrate, don't the
guys inside the perimeter have some trouble replicating?

Damien Broderick
[not a biologist]

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