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weird growth on agar

Patrick in_vivo at usa.net
Wed Sep 26 00:33:44 EST 2001

Hi, I use "Buffered Charcoal Yeast Extract Agar" to grow Legionella
pneumophila. I make the agar plates myself. Recently One thing happens
very weird and interestingly that instead of growing evenly across the
plate, the bacteria grow to form a round midsize lawn only at the
center of my plates, for all tens of plates. Of course I'm confident
of spreading the bacterial liquid culture evenly throughout plates.

My first thought was that the addition of charcoal into the agar
somehow changes the surface tension when the agar solidify so that the
center of the plates is lower geographically. Anybody has met similar
problems before and any comments? Thank you.

Plus, how much time does a normal Legionella strain usually take to
form a lawn on the BCYE plates? Overnight or two days or even longer,
if I spread the bacteria with 150ul of OD600=3.0?

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