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|Title:||Regulation of Ammonia Assimilating Enzymes in the Ruminal Bacteria Selenomonas Ruminantium and Succinivibrio Dextrinosolvens|
|Author(s):||Patterson, John Andrews|
|Department / Program:||Dairy Science|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Agriculture, Animal Culture and Nutrition|
|Abstract:||Selenomonas ruminantium was grown in continuous culture under glucose-limitation at dilution rates of .05, .10, .20, .30 and .42 and under ammonia-limitation at dilution rates of .05, .10 and .20, to determine the effects of dilution rate and growth-limiting nutrients on cell physiology, efficiency of growth and ammonia assimilating enzymes. Culture viability was decreased at low dilution rates for both growth-limiting conditions, but the decrease in viability was more severe in glucose-limited cultures. Cell composition changed little under the conditions tested; however, the amount of nitrogen containing material (as % dry weight) was lower in ammonia-limited than in glucose-limited cultures of S. ruminantium.
Cell yields decreased at low dilution rates and were lower for ammonia-limited cultures of Selenomonas ruminantium. The decrease in yields at low dilution rates was due to the increasing influence of the maintenance requirement at low dilution rates. Part of decrease in yields due to ammonia-limitation was attributed to increase utilization of the ATP-requiring glutamine synthetase/glutamate synthase pathway for ammonia assimilation.
Glutamine synthetase activity was high and glutamated ehydrogenase activity was low in ammonia-limited cultures of Selenomonas ruminantium. The reverse was observed in glucose-limited cultures. Under ammonia-limitation, glutamine synthetase activity increased with increasing dilution rate. Under glucose-limitation, glutamate dehydrogenase activity was maximal at an intermediate dilution rate.
The major ammonia-assimilating enzymes detected in Succinivibrio dextrinosolvens were glutamate dehydrogenase and glutamine synthetase. The regulation of glutamine synthetase activity by adenylation-deadenylation mechanisms was indicated by the rapid loss of activity upon ammonia-shocking of the culture and the recovery of this activity upon incubation with snake venom phosphodiesterase. The adenylation state of Succinivibrio dextrinosolvens glutamine synthetase could not be determined using gamma glutamyl transferase assay procedures. Preliminary data indicated that glutamine synthetase was also regulated by feedback inhibition and by regulation of its synthesis in response to culture ammonia concentration.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1982.
|Date Available in IDEALS:||2014-12-16|