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ARS Home » Northeast Area » Ithaca, New York » Robert W. Holley Center for Agriculture & Health » Research » Publications at this Location » Publication #85992
Title: RELATIONSHIP BETWEEN INTRACELLULAR PHOSPHATE, PROTON MOTIVE FORCE, AND RATE OF NONGROWTH ENERGY DISSIPATION (ENERGY SPILLING) IN STREPTOCOCCUS BOVIS JB1

Author
item BOND, DANIEL - CORNELL UNIVERSITY
item Russell, James

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: In ruminant animals, microbial protein is the major source of amino acids reaching the small intestine, and the efficiency of microbial protein synthesis can have a large impact on animal performance. Previous work indicated that ruminal bacteria could spill energy in futile reactions and decrease microbial protein flow to the intestines. Using the ruminal bacterium Streptococcus bovis as a model, we demonstrated that the membran bound ATPase was the energy spilling enzyme. In this paper we showed that increases in intracellular phosphate caused an increase in membrane voltage and energy spilling rate. Information on energy spilling may provide a means of increasing microbial flow from the rumen and improving the efficiency of animal production.

Technical Abstract: When the rate of gluclose addition to non-growing S. bovis cell suspensions was increased, the fermentation was homolactic, fructose 1,6 diphosphate (FDP) increased, intracellular phosphate (Pi) declined and the energy spilling rate increased. The FDP-dependent decline in Pi increased the dg**1 of ATP hydrolysis and was correlated with an increase in protonmotive force (dp). S. bovis continuous cultures (dilution rate of 0.6 h-1) that were forced to use ammonia as a nitrogen source also had high rates of lactate production and energy spilling. When Trypticase was added to the culture medium as a source of amino acids, lactate production decreased, a greater fraction of the glucose was converted to acetate, formate and ethanol, and the energy spilling rate decreased. Trypticase caused a decrease in FDP, an increase in Pi and a decrease in dp. The change in dp could be explained by Pi-dependent changes in the free energy of ATP hydrolysis (dG**1p). When Pi declined, dG**1p increased. The ratio of dG**1p to dp (mV/mV) was always greater (>4) at low rates of energy spilling, but declined (<3.5) when the energy spilling rate increased. Based on these results, it appears that dp and the energy spilling rate are coordinately regulated by intracellular phosphate.