Summary: The size of the amino acid pool in , a rumen bacterium, was limited by the availability of ammonia in the growth medium. Alanine was the major pool constituent irrespective of the growth-limiting nutrient. In steady-state ammonia-limited chemostat cultures, glutamine synthetase (GS) activity was tenfold higher and glutamate dehydrogenase (GDH) activity up to fivefold lower than in maltose-limited cultures. No glutamate synthase (GOGAT) activity was demonstrated. When excess ammonia was pulsed into an ammonia-limited chemostat culture, the glutamine pool expanded rapidly and GS was inactivated. This was consistent with the observation that, in a number of bacteria, GS functions to assimilate ammonia when the prevailing concentration is low. However, GDH was always very active in extracts of and its Michaelis constant for ammonia was relatively low (1 to 2 mM). This suggested that GDH could continue to function bio-synthetically when GS was derepressed.


Article metrics loading...

Loading full text...

Full text loading...


Most cited this month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error