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weird bacteria

Scott J. Coutts scott.coutts at med.monash.edu.au
Mon Mar 3 01:03:42 EST 2003

Graham Shepherd wrote:
> "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
>>Here's a large picture I took yesterday of the buggers:
>>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.

But if it's a swarmer and a non-swarmer, why would the discrete colonies 
appear all over the plate? Can swarmers 'carry along' non-swarmers?! If 
the plate is inoculated at only one point, then the swarmers will 
spread, and single colonies of the other one will only be at the 
inoculation point, surely?

> Separating the colony formers from the swarmers is going to require special
> media, selective agents or other selective methods (eg temperature).

To seperate out our highly motile spirochaetes from other contaminants, 
we cut a slice in the agar, and inoculate the slice. Only our 
spirochaetes are motile enough to get out of there. I'm sure there's 
lots of others that could get out too, but thankfully, we never get them 
as contaminants (: But then, we also have the 'cheats' method of 
separating our spirochaetes - they get through a 0.2um filter, others 
dont (:

> This is why microbiologists use stains and stuff.

I agree that it should be stained.

Scott J. Coutts
  Bacterial Pathogenesis Research Group		
  Department of Microbiology			Ph  [+61 3 9905 4838]
  PO Box 53					Fax [+61 3 9905 4811]	
  Monash University, 3800, Austrlalia

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