Fumarate reduction inProteus mirabilis

Abstract

1. Proteus mirabilis formed fumarate reductase under anaerobic growth conditions. The formation of this reductase was repressed under conditions of growth during which electron transport to oxygen or to nitrate is possible. In two of three tested chlorate-resistant mutant strains of the wild type, fumarate reductase appeared to be affected. 2. Cytoplasmic membrane suspensions isolated from anaerobically grown P. mirabilis oxidized formate and NADH with oxygen and with fumarate, too. 3. Spectral investigation of the cytoplasmic membrane preparation revealed the presence of (probably at least two types of) cytochrome b, cytochrome a1 and cytochrome d. Cytochrome b was reduced by NADH as well as by formate to approximately 80%. 4. 2-n-Heptyl-4-hydroxyquinilone-N-oxide and antimycin A inhibited oxidation of both formate and NADH by oxygen and fumarate. Both inhibitors increased the level of the formate/oxygen steady state and the formate/fumarate steady state. 5. The site of inhibition of the respiratory activity by both HQNO and antimycin A was located at the oxidation side of cytochrome b. 6. The effect of ultraviolet-irradiation of cytoplasmic membrane suspensions on oxidation/reduction phenomena suggested that the role of menaquinone is more exclusive in the formate/fumarate pathway than in the electron transport route to oxygen. 7. Finally, the conclusion has been drawn that the preferential route for electron transport from formate and from NADH to fumarate (and to oxygen) includes cytochrome b as a directly involved carrier. A hypothetical scheme for the electron transport in anaerobically grown P. mirabilis is presented.

Respiration-induced Changes in the Adenine Nucleotide Pool Composition of Harvested Beneckea natriegens

“…The experiment was carried out using various sizes of HzOz pulses in the manner described in , 1973;Gadkari & Stolp, 1976). However, this could be due to preconditioning of the various bacteria by changes in aeration of the bacteria prior to experimentation (see below).…”

“…In both cases measurements had to be made at 12 "C to slow the respiratory activity; the maximum ATP concentration was then reached after 15 to 25 s enabling the initial rate of oxygen uptake to be accurately measured. Van der Beek & Stouthamer (1973) hamer (1973): anaerobic suspensions of bacteria were mixed with limited amounts of oxygen and the degree of phosphorylation was compared with the oxygen pulse size. It is crucial, when determining ATP/O quotients in experiments of this type, to quench metabolic activity at exactly the moment of oxygen depletion, yet neither group reported how they achieved this.…”

“…To estimate PI0 ratios, we have used a modification of the methods of Knowles & Smith (1970) and van der Beek & Stouthamer (1973): small pulses of oxygen were added to anaerobic suspensions and metabolic activity was quenched slightly before anaerobiosis was regained, correcting for the residual oxygen in calculating the P/O quotient.…”

Purification and characterization of fumarate reductase from Methanobacterium thermoautotrophicum

“…Fumarate reductase isolated from Proteus mirabilis was also found to be repressed when oxygen or nitrate was available as an electron acceptor (46). This enzyme is also coupled to the synthesis of ATP.…”

“…Its properties are summarized in Table VII Table VII. Preliminary studies were also carried out on the membrane-bound fumarate reductases from Clostrodium formicoaceticum (47) and Proteus mirabilis (46).…”