Nitrifying Bacteria

Bill Purves purves at TURING.CS.HMC.EDU
Mon Sep 8 14:07:06 EST 1997

At 11:21 AM 9/8/97 -0700, Avleen Vig wrote:

>Nitrifying bacteria take nitrogen in the soil and convert it to ammonia and
>ammonium ions. How does the Nitrosomonas and Nitrococcus bacteria use
>ammonia or the ammonium ions to make energy?

Actually, it is other bacteria, the nitrogen fixers, that reduce N2 to
ammonia and ammonium ions.

Nitrifying bacteria oxidize these reduced products to nitrite and nitrate
ions.  _Nitrosomonas_ and _Nitrosococcus_ oxidize ammonia to nitrite;
_Nitrobacter_ oxidizes nitrite to nitrate.

In this type of chemosynthesis, electrons are passed (from nitrite, in
the case of _Nitrobacter_) through an electron transport chain, generating
ATP as in respiratory metabolism.  In photosynthesis, photophosphorylation
provides ATP and NADPH for carbon dioxide fixation; in the chemosynthesis
of nitrifiers, ATP and NADH derived from electron transport can be used
to fix carbon dioxide.

I hope this brief account is of use to you.


William K. Purves               The Mona Group LLC
2817 N. Mountain Avenue        phone: 909.626.4859   
Claremont, CA 91711-1550         fax: 909.626.7030
           e-mail: purves at

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