Looking for a nitrate minus bacterium

[Laanbroek, Riks]

Dear microbiologists,

I am looking for a common freshwater or soil, heterotrophic bacterium unable
to use nitrate or nitrite as a source of nitrogen for growth. I need such an
organism in competition experiments with nitrifying bacteria. In these
experiments the autotrophic and heterotrophic bacteria have to compete for
ammonium and the looser should not be able to grow at the products of the
winner. In addition, the heterotrophic bacterium must be abe to grow on a
simple mineral medium with glucose as carbon and energy source. After 
looking
for quite some time in Bergey's and in the Prokaryotes, I could not find a
suitable bacterium. So I am wondering if somebody else could suggest an
appropriate bacterium. It might also be a mutant unable to assimilate 
nitrate and
nitrite.

Riks Laanbroek
email: laanbroek at nioo.nl