[Microbiology] Re: isolation of bacteria

JEDilworth via microbio%40net.bio.net (by bactitech from nospamhortonsbay.com)
Sun Sep 21 01:32:17 EST 2008

Three weeks of incubation for bacteria seems excessive. I know nothing 
about DNA extraction or environmental bacteria, but I do know that 
bacteria go through growth phases. Eventually they will be living in 
their own filth and die off. Why did you decide on three weeks? Are you 
inoculating into anything nutritional? Are you passing your growth into 
new broths along the way? Why not streak the water onto solid media and 
see what grows? May have to do dilutions until you find a dilution where 
you can get isolated colonies. Pick the colonies individually, one at a 
time, and put them into their own broth, and then you will have pure 
cultures. Why work with mixed cultures?

I have no idea what media you would use for this - just putting the 
concept out there. I know we do water cultures from time to time and use 
something called Standard Methods agar. We buy the deeps commercially. 
We are not dealing with this type of water, however. We're culturing 
distilled water and checking for contaminants.

What temperature are you using? I would think environmental bacteria 
need cooler temperatures than, say, 35 degrees C which is what we 
incubate human medical bacterial specimens at. Again, I am a medical 
micro person - NOT an environmental one.

Robert Koch discovered solid media in the 1880's. This is how he got a 
leg up on Louis Pasteur, who never figured out how to move beyond broth 
cultures and work with pure cultures. Solid media is the foundation of 
modern bacteriology.

Judy Dilworth, M.T. (ASCP)

"RUTH SIELE" <ruthsiele from yahoo.com> wrote in message 
news:mailman.82.1221933057.29717.microbio from net.bio.net...
I am trying to isolate the bacteria from brackish water. I incubated the 
brackish water for three weeks. When I centrifuge the culture after 
three weeks, I couldn't get any pellets to extract the DNA. I streak 
them in LB plates but it will be culture dependent.

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