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weird growth on agar

Dave david.lawton1 at nowaspamfreezonentlworld.com
Wed Sep 26 02:22:54 EST 2001

"Patrick" <in_vivo at usa.net> wrote in message
news:db4f87f8.0109252133.34795436 at posting.google.com...
> 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?

Do you mean you make the agar from basics or is it a complete powder?

If it's the former check that your agar powder is gelling properly as I
have known batches that haven't worked very well and we had to increase the
agar concentration.
If it hasn't happened before look to see what's changed


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