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weird bacteria update

JEDilworth bactitech at nospamhortonsbay.com
Wed Mar 19 20:35:34 EST 2003


This is an article in pdf format regarding Bacillus species that can 
swarm. This may possibly be what you're dealing with, as opposed to a 
gram negative rod.

It's very difficult to see colony morphology with all your colonies up 
in the inoculum area. When you inoculate like that, take your loop, 
streak out a couple of rows, flame and turn your plate, streak out a 
couple of streaks, flame and do it again. It's the ONLY way you're going 
to be able to tell if you have a pure culture. Then, each isolated 
colony, if again subcultured, will yield a pure culture.


Check out this paper to see what I'm talking about. This is how we 
streak out ALL of our cultures from clinical specimens, so that we can 
separate out the different species and subculture them for antibiotic 
susceptibility testing and identification.


This is a streaked plate on blood agar of a gram negative rod.

Also, your gram stain looks more like a gram positive rod, if it is 
indeed a gram stain, as opposed to a gram negative. Are you sure you 
have decolorized adequately?


Here is a pic I found real quick through google.com images of a Bacillus 
species. Most of them look like this on gram stain.


Here is a gram negative rod, although the pic doesn't say which one it 
is. I've found that Bacillus species are usually larger than most gram 

Judy Dilworth, M.T. (ASCP)
Microbiology 29 years

Trond Erik Vee Aune wrote:

> Hi
> I've now done some more work on the bacteria.
> The first picture shows a LB plate with 6% agar:
> http://www.biotech.ntnu.no/~trondaun/xbug/6%20percent%20agar.JPG
> I spread the colonies on the area indicated with the red line. As you 
> can see the higher concentration of agar keep the bacteria from 
> spreading almost totally. 

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