Nitrogen fixation

N2 + H + electrons to NH4 + H2

reaction, costs two ATP

Nitrogenase

Irreversibly damaged by oxygen, nif genes encode, highly regulated enzyme

induction by nitrogen demand

only when nitrogen is needed nitrogenase is made, ntrB and C regulate, low glutamine induces

inhibition by ammonium

high ammonium concetrations inhibit (end product), enzymes assimilate the NH4 quickly or send to linked cells or partners

regulation by oxygen

For aerobes/microaerobes, fixLJ system and hemeprotein binds oxygen to protect

Clostridium

a genus of bacteria that can fix nitrogen in anaerobic conditions, often found in the soil and in association with plant roots.

K. Pneumonia

a bacterium that can fix nitrogen only when oxygen is not present

azobacter

aerobic N fixer that has FeSII which binds nitrogenase and protects from oxygen, use oxygen very quickly

respiratory protection

use oxygen to quickly for nitrogenase damage

azospirillum

terminal oxidases with high oxygen affinity protect nitrogenase by burning all oxygen to quckly

heterocysts

compartmentalize the anaerobic n fixing cells preventing oxygen exposure and allow NH4 export