E. Coli glycerol stock cytometry

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Leon Fnord
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E. Coli glycerol stock cytometry

Post by Leon Fnord » Wed Nov 28, 2007 11:35 pm

I have recently been trying to count E. coli using a Petroff-Hauser counting chamber. I wanted to count cells straight out of my glycerol stocks, but I am having difficulties.

The E. coli looks strange directly after the glycerol stock is thawed.

My Procedure:
Thaw the E. coli cell bank (glycerol stock) at 37 C.
Dilute the cell bank at a 1:10 dilution in saline & pipette 50 uL into the counting chamber.
View on scope at 400X magnification.

Specifically, the cells look elongated and many appear to be fused together in a linear orientation. Often times, several appear to be fused in chains of 5 or 6 individual units. This is strange because if I view E. coli from a live and growing culture, I can see discrete cells. :?

Can anyone explain to me what I am observing? Is this common? What causes it? Are there any handling precautions I can take to minimize this phenomenon?

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