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weird bacteria

Graham Shepherd muhero.nospam at globalnet.co.uk
Sun Mar 2 16:27:34 EST 2003

"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 of
the plate and produced confluent growth. The colonies you are getting are
from other species.  It is very difficult to separate swarming species from
others - if you take samples from the colonies you will get both. Try taking
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 back
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 special
media, selective agents or other selective methods (eg temperature).

This is why microbiologists use stains and stuff.


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