HELP!! Need information re a soil based exp

Thomas Junier tjunier at ulys.unil.ch
Tue Oct 25 04:25:49 EST 1994


In article <38a5ah$2d3 at newsbf01.news.aol.com>, ibdip at aol.com (IB Dip) wrote:

> I am a high school student who has to design experiment ased of the
> ability of a bacteria to survive in various concentrations of minerals,
> yet I don't know what bacteria to use.  I have seen several listed in this
> newsgroup, but are any of them dependent upon mineral concentration in the
> surrounding soil?

If you don't need to know exactly which bacterium you're using, the
easiest way would be to isolate bacteria from a soil sample, and carry out
your experiments with these isolates. You could have them identified if
necessary, anyway. On the other hand, if you need to know the exact
strain(s), you should choose a species that is usually found in soil.
There are lots of possible choices. One of the most studied and best known
is B. subtilis.

The effect of mineral concentration is certainly important, although, as
far as I know, it is not always well known, because it's much easier to
study bacteria in a test tube than in their natural environment. But here
are a few factors that depend on the type, concentration, solubility and
physiological role of minerals:
   - pH
   - osmotic pressure
   - availability of potassium, magnesium, phosphorus e.t.c.

Of course, there are many more things you could investigate, but that
depends a lot on the time and equipment you have. Nitrogen fixation is an
important phenomenon, but you'll need special culture conditions (no
oxygen) to observe it. Can your beastie use CO(2) as a source of carbon ?
Then watch the effect of carbonates...

Hope this helps!



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