Biomedical subjects
Publications and source records attributed to L Bongers.
Molar growth yields were determined from chemostat cultures of Hydrogenomonas eutropha on succinate and on fumarate. The yields from culture on succinate were about 12 g higher than on fumarate. Assuming this difference to be equivalent to 1 molecule of adenosine triphosphate, it is concluded that the oxidation by oxygen of the Hydrogenomonas cytochrome b yields 1 molecule of adenosine triphosphate.
Studies on the relationship between cell synthesis and energy utilization in Hydrogenomonas eutropha have shown that the amount of oxidative energy required for synthetic reactions depends on the conditions of growth. The energy of hydrogen oxidation was most efficiently used when growth conditions were optimal (continuous culture, cells in exponential growth phase) and when the rate of growth was limited by H(2) or O(2) supply. Under these conditions, 2 to 2.5 atoms of oxygen were consumed by the oxyhydrogen reaction for the concomitant conversion of 1 mole of CO(2) to cell matter. This conversion efficiency, expressed as the O/C energyyield value, was observed with continuous cultures. A less efficient conversion was found with batch cultures. With limiting concentrations of CO(2) the rate of hydrogen oxidation was relatively high, and the O/C value was dependent on the growth rate. With nonlimiting concentrations of CO(2), the rate of hydrogen oxidation was strictly proportional to the rate of CO(2) fixation, and the O/C value was independent of growth rate. This proportionality between the rate of H(2) oxidation and the rate of CO(2) fixation suggested that energy supply regulates the (maximum) rate of growth. From the energy-yield measurements, we concluded that the oxidation of 1 mole of H(2) yields the equivalent of 2 moles of adenosine triphosphate for H. eutropha, and that at least 5 moles of this high-energy phosphate is required for the conversion of 1 mole of CO(2) into cellular constituents.
The electron-transport system of cell-free extracts obtained from Hydrogenomonas H-20 has been studied with particular reference to phosphorylation associated with the oxyhydrogen reaction. Cell-free preparations of this organism exhibit oxidative phosphorylation with hydrogen and succinate as electron donors. This activity could be uncoupled with a number of agents. Ratios of phosphorylative activity to oxidative activity observed varied from 0.2 to 0.7. Factors affecting the efficiency of phosphorylation were examined. Inhibitor and spectrophotometric studies indicated that phosphorylation with hydrogen as electron donor occurs exclusively at a site in an abbreviated electron transport chain between H(2) and cytochrome b. The possible occurrence of a cytochrome b oxidase and the requirement for a quinone are discussed, as well as the correlation between the abbreviated pathway and the energy generation by the cell. Evidence is presented which indicates that nicotinamide adenine dinucleotide does not participate in the hydrogen oxidation path which is coupled to adenosine triphosphate formation.