Pipetting, contamination....

[Tom Anderson]

On Fri, 22 Feb 2007, peter wrote:

> On Feb 22, 7:41 pm, d... from no.email.thankstospam.net (DK) wrote:
> > In article <1172181256.088647.198... from a75g2000cwd.googlegroups.com>, "peter" <peter.ianak... from gmail.com> wrote:
> >
> > >> Jeez, I've done this experiment yesterday:
> > >> 1. Took a 1 ml Pipetman, set it to 1 ml and pipetted overnight E.coli
> > >> culture up and down 20 times.
> > >> 2. Immediately after that, changed a tip, took a bottle of sterile
> > >> Terrific Broth, pipetted 20 times, set at 37C for 20 hours.
> > >>
> > >> The result: no signs of bacterial growth today ==> no aerosol
> > >> contamination.
> > >
> > >Seems like a good experiment, I just wonder what volume of the TB
> > >media you used?
> >
> > The standard square bottle filled with 100 ml.
>
> DK  ... People make night cultures for a reason before they seed 100
> ml botles.

I don't. I innoculate 100 ml or bigger cultures straight from picked
colonies. Works fine.

> wonder why?

Me too. It's 'good microbiological practice', but i can't see any reason
why it's necessary, and in my experience, there's no problem with not
doing it.

> Can you repeat same experiment with like 2 ml TB or SOC?

Alternatively, 100 ul of LB or something and then plate it. I don't know
how easy it is to see small amounts of growth in a liquid culture, but we
know that on a plate, you can detect a single bacterium.

tom

-- 
Tom Anderson, MRC Laboratory for Molecular Cell Biology, UCL, London WC1E 6BT
(t) +44 (20) 76797264   (f) +44 (20) 76797805   (e) thomas.anderson from ucl.ac.uk