denitrifying bacteria

Ed Stokes ebstokes at
Tue Jul 7 08:30:15 EST 1992

I am a physicist working in a new area (new for me): optical
spectroscopy of aqueous biological media. We obtained a sample of
pseudomonas denitrificans from American Type Culture Collection, mixed
the growth media according to the recipe, and generated about 70
frozen aliquots of 50/50 culture/glycerol.

A couple of weeks ago, we took two aliquots and placed them in
individual sterile flasks on an orbital shaker, each in ~250 ml of
fresh growth media. We then added ~1000 ppm NaNO2 to one of the
flasks. The cultures have both grown up to a nice thickness, visually,
but the nitrite concentration has not changed.

The initial pH of both flasks was about 6. The control has changed to
about 7, but the nitrite-containing culture has remained at 6. Optical
density measurements indicate that the biomass has been in steady
state in both flasks for the two week period.

We have not changed the growth media in either flask.

My inclination is to bring the pH up to about 7.5 and see if we can
stimulate some denitrifying activity.

Any suggestions would be appreciated.

Ed Stokes
ebstokes at

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