"Graham Shepherd" <muhero.nospam at globalnet.co.uk> wrote in message
news:b3tt06$b4i$1 at knossos.btinternet.com...
> "Trond Erik Vee Aune" <trondaun at chembio.NOSPAM.ntnu.no> wrote in message
> news:3E625E1F.2050809 at chembio.NOSPAM.ntnu.no...> >
> > Scott J. Coutts wrote:
> > > What do the colonies look like, and how big are they? Would it be
> > > possible for you to post some pictures on the web somewhere, or in
> > > alt.test
> > Here's a large picture I took yesterday of the buggers:
> > http://www.biotech.ntnu.no/~trondaun/Bug.JPG> >
> > Let me explain the picture (a 9 cm plate). If you look carefully at the
> > part of the plate furthest away from the camera you'll be able to see a
> > thin red line written on the bottom of the plate. This was the boundary
> > of the original streaking. I put a fair amount of colony material in
> > this area, but the day after only distinct colonies had appeared, and
> > too my surprise single colonies also had grown outside this area. For
> > each day after this, the colonies spread further down the plate. At
> > first they appear to have no connection with the other colonies, but
> > after a few days, thin lines seem to connect them (you can probably see
> > this between the oldest colonies. The newest colonies (those closest to
> > the lens) seem to have no connection to the others). Some of the
> > colonies also look like spirals, almost as if they have been built by
> > bacteria swimming in a spiral.
>> An opinion - you will probably get several more.
>> It looks to me like a mixed culture including a highly motile species
> (Proteus for example) which has actually swarmed over the entire surface
> the plate and produced confluent growth. The colonies you are getting are
> from other species. It is very difficult to separate swarming species
> others - if you take samples from the colonies you will get both. Try
> a sample from a clear area of the plate and inoculating into broth. If
> anything grows it's going to be the swarmer. Subculture from the broth
> on to agar and see what it looks like. If I'm right, you'll get confluent
> growth without colonies.
>> Separating the colony formers from the swarmers is going to require
> media, selective agents or other selective methods (eg temperature).
>> This is why microbiologists use stains and stuff.
What about subculturing the swarmer onto a plate with a stronger agar
concentration? We used to use one (6% agar if I remember correctly) which
would stop the swarmers.