Biomedical subjects

J B Russell

Publications and source records attributed to J B Russell.

At least 91 records · Page 5Linked to original sources

PubMed1994

Ability of Acidaminococcus fermentans to oxidize trans-aconitate and decrease the accumulation of tricarballylate, a toxic end product of ruminal fermentation.

Mixed ruminal bacteria convert trans-aconitate to tricarballylate, a tricarboxylic acid which chelates blood divalent cations and decreases their availability (J. B. Russell and P. J. Van Soest, Appl. Environ. Microbiol. 47:155-159, 1984). Decreases in blood magnesium in turn cause a potentially fatal disease known as grass tetany. trans-Aconitate was stoichiometrically reduced to tricarballylate by Selenomonas ruminantium, a common ruminal bacterium in grass-fed ruminants (J. B. Russell, Appl. Environ. Microbiol. 49:120-126, 1985). When mixed ruminal bacteria were enriched with trans-aconitate, a trans-aconitate-oxidizing bacterium was also isolated (G. M. Cook, F. A. Rainey, G. Chen, E. Stackebrandt, and J. B. Russell, Int. J. Syst. Bacteriol. 44:576-578, 1994). The trans-aconitate-oxidizing bacterium was identified as Acidaminococcus fermentans, and it converted trans-aconitate to acetate, a nontoxic end product of ruminal fermentation. When S. ruminantium and A. fermentans were cocultured with trans-aconitate and glucose, tricarballylate never accumulated and all the trans-aconitate was converted to acetate. Continuous-culture studies (dilution rate, 0.1 h-1) likewise indicated that A. fermentans could outcompete S. ruminantium for trans-aconitate. When mixed ruminal bacteria were incubated in vitro with 10 mM trans-aconitate for 24 h, 45% of the trans-aconitate was converted to tricarballylate. Tricarballylate production decreased 50% if even small amounts of A. fermentans were added to the incubation mixes (0.01 mg of protein per mg of mixed bacterial protein). When A. fermentans (2 g of bacterial protein) was added directly to the rumen, the subsequent conversion of trans-aconitate to tricarballylate decreased 50%, but this effect did not persist for more than 18 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Aconitic Acid↗

PubMed1994

Dual Mechanisms of Tricarboxylate Transport and Catabolism by Acidaminococcus fermentans.

Acidaminococcus fermentans utilized citrate or the citrate analog aconitate as an energy source for growth, and these tricarboxylates were used simultaneously. Citrate utilization and uptake showed biphasic kinetics. High-affinity citrate uptake had a K(t) of 40 muM, but the V(max) was only 25 nmol/mg of protein per min. Low-affinity citrate utilization had a 10-fold higher V(max), but the K(s) was greater than 1.0 mM. Aconitate was a competitive inhibitor (K(i) = 34muM) of high-affinity citrate uptake, but low-affinity aconitate utilization had a 10-fold-lower requirement for sodium than did low-affinity citrate utilization. On the basis of this large difference in sodium requirements, it appeared that A. fermentans probably has two systems of tricarboxylate uptake: (i) a citrate/aconitate carrier with a low affinity for sodium and (ii) an aconitate carrier with a high affinity for sodium. Citrate was catabolized by a pathway involving a biotin-requiring, avidin-sensitive, sodium-dependent, membrane-bound oxaloacetate decarboxylase. The cells also had aconitase, but this enzyme was unable to convert citrate to isocitrate. Since cell-free extracts converted either aconitate or glutamate to 2-oxoglutarate, it appeared that aconitate was being catabolized by the glutaconyl-CoA decarboxylase pathway. Exponentially growing cultures on citrate or citrate plus aconitate were inhibited by the sodium/proton antiporter, monensin. Because monensin had no effect on cultures growing with aconitate alone, it appeared that citrate metabolism was acting as an inducer of monensin sensitivity. A. fermentans cells always had a low proton motive force (<50 mV), and cells treated with the protonophore TCS (3,3',4',5-tetrachlorosalicylanide) grew even though the proton motive force was less than 20 mV. On the basis of these results, it appeared that A. fermentans was depending almost exclusively on a sodium motive force for its membrane energetics.

Journal Article↗

PubMed1994

Electrogenic glutamine uptake by Peptostreptococcus anaerobius and generation of a transmembrane potential.

Peptostreptococcus anaerobius converted glutamine stoichiometrically to ammonia and pyroglutamic acid, and the Eadie-Hofstee plot of glutamine transport was biphasic. High-affinity, sodium-dependent glutamine transport (affinity constant [Kt] of 1.5 microM) could be driven by the chemical gradient of sodium, and more than 20 mM sodium was required for half-maximal velocity. High-affinity glutamine transport was not stimulated or inhibited by a membrane potential (delta psi). Low-affinity glutamine transport had a rate which was directly proportional to the external glutamine concentration, required less than 100 microM sodium, and was inhibited strongly by a delta psi. Cells which were treated with N,N-dicyclohexylcarbodiimide to inhibit the F1F0 ATPase still generated a delta psi but did so only if the external glutamine concentration was greater than 15 mM. Low-affinity glutamine uptake could not be saturated by as much as 200 mM glutamine, but glutamine-1 accounts for only a small fraction of the total glutamine at physiological pH values (pH 6 to 7). On the basis of these results, it appeared that the low-affinity glutamine transport was an electrogenic mechanism which was converting a chemical gradient of glutamine-1 into a delta psi. Other mechanisms of delta psi generation (electrogenic glutamine-pyroglutamate or -ammonium exchange) could not be demonstrated.

Biological Transport↗

PubMed1994

Binding of radiolabeled monensin and lasalocid to ruminal microorganisms and feed.

Gram-negative, ionophore-resistant ruminal bacteria and Gram-positive, ionophore-sensitive species bound similar amounts of [14C]lasalocid, but neither group bound large amounts of [14C]monensin. Membrane vesicles also bound more lasalocid than monensin (P < .05). The binding was first-order at low cell or vesicle concentrations and saturable at high cell or vesicle densities. Streptococcus bovis was inhibited by both monensin and lasalocid (5 microM), but cells that were re-incubated in medium lacking ionophore grew rapidly. Lasalocid-treated cells grew very slowly when they were resuspended in fresh medium. Based on these results, it seemed that lasalocid had a higher affinity for bacterial membranes than monensin. Mixed bacteria, however, bound nearly equal amounts of [14C]monensin and [14C]lasalocid (P > .05). Monensin binding was greatly reduced when the mixed ruminal bacteria were pretreated with Tris+EDTA (P < .05), but Tris+EDTA did not affect the binding of lasalocid. Mixed ruminal protozoa always took up more lasalocid than monensin (P < .05), but feed particles bound equal amounts of [14C]lasalocid and [14C]monensin (P > .05). Based on the binding capacity of mixed ruminal bacteria, ruminal protozoa, and feed particles, there would be little free ionophore in ruminal fluid.

Animal Feed↗

PubMed1993

The glutamine cyclotransferase reaction of Streptococcus bovis: a novel mechanism of deriving energy from non-oxidative and non-reductive deamination.

Streptococcus bovis deaminated glutamine by a mechanism that did not involve glutaminase. Since pyroglutamate and ammonia were the only end-products, it appeared that glutamine deamination was catalyzed by a cyclotransferase reaction. Stationary S. bovis cells had essentially no intracellular ATP or membrane potential (delta psi), however, when they were provided with glutamine, intracellular ATP and delta psi increased to 0.52 mM and 158 mV, respectively. When glutamine-energized cells were treated with N,N-dicyclohexylcarbodiimide (DCCD, 150 microM), there was an even greater increase in intracellular ATP (> 5-fold) and the delta psi was dissipated. Because toluene-treated cells produced ATP from ADP and Pi, it did not appear that the cell membrane was directly involved in glutamine-dependent ATP generation. The rate of ammonia production was directly proportional to the glutamine concentration, but the stoichiometry of ATP to ammonia was always 1 to 1. Based on these results, it appeared that glutamine was deaminated by glutamine cyclotransferase which was coupled to ATP formation. The membrane bound ATPase then used the ATP to create a delta psi.

Acyltransferases↗

PubMed1993

Mediators of leukocyte adhesion in rat mesenteric venules elicited by inhibition of nitric oxide synthesis.

BACKGROUND: Inhibitors of nitric oxide production promote leukocyte adherence and emigration in postcapillary venules. The objective of this study was to determine if the enhanced leukocyte adherence and emigration associated with inhibition of NO production involves inflammatory agents such as platelet-activating factor (PAF) and leukotriene B4 (LTB4) and/or phospholipase A2 (PLA2). METHODS: The rat mesentery was superfused with the inhibitor of NO production NG-nitro-L-arginine methyl ester (L-NAME) either alone or in combination with WEB2086 (PAF receptor antagonist), SC41930 (LTB4 receptor antagonist), or quinacrine (PLA2 inhibitor). The number of adherent and emigrated leukocytes, leukocyte rolling velocity, erythrocyte velocity, venular blood flow, and shear rate were monitored in mesenteric venules. RESULTS: L-NAME alone induced a dramatic increase in leukocyte adherence (10-fold) and emigration (4-fold). Treatment with SC41930 significantly reduced, whereas either WEB2086 or quinacrine completely abolished, the increased leukocyte adherence and emigration induced by L-NAME. CONCLUSIONS: These observations suggest that the increased leukocyte adherence and emigration associated with inhibition of NO synthesis involves PLA2 activation and is mediated by PAF and LTB4.

Animals↗

PubMed1993

Phylogeny of the ammonia-producing ruminal bacteria Peptostreptococcus anaerobius, Clostridium sticklandii, and Clostridium aminophilum sp. nov.

In previous studies, gram-positive bacteria which grew rapidly with peptides or an amino acid as the sole energy source were isolated from bovine rumina. Three isolates, strains C, FT (T = type strain), and SR, were considered to be ecologically important since they produced up to 20-fold more ammonia than other ammonia-producing ruminal bacteria. On the basis of phenotypic criteria, the taxonomic position of these new isolates was uncertain. In this study, the 16S rRNA sequences of these isolates and related bacteria were determined to establish the phylogenetic positions of the organisms. The sequences of strains C, FT, and SR and reference strains of Peptostreptococcus anaerobius, Clostridium sticklandii, Clostridium coccoides, Clostridium aminovalericum, Acetomaculum ruminis, Clostridium leptum, Clostridium lituseburense, Clostridium acidiurici, and Clostridium barkeri were determined by using a modified Sanger dideoxy chain termination method. Strain C, a large coccus purported to belong to the genus Peptostreptococcus, was closely related to P. anaerobius, with a level of sequence similarity of 99.6%. Strain SR, a heat-resistant, short, rod-shaped organism, was closely related to C. sticklandii, with a level of sequence similarity of 99.9%. However, strain FT, a heat-resistant, pleomorphic, rod-shaped organism, was only distantly related to some clostridial species and P. anaerobius. On the basis of the sequence data, it was clear that strain FT warranted designation as a separate species. The closest known relative of strain FT was C. coccoides (level of similarity, only 90.6%). Additional strains that are phenotypically similar to strain FT were isolated in this study.(ABSTRACT TRUNCATED AT 250 WORDS)

Ammonia↗

PubMed1993

Effect of monensin on the specific activity of ammonia production by ruminal bacteria and disappearance of amino nitrogen from the rumen.

When unadapted mixed ruminal bacteria (312 mg of protein per liter) were treated with monensin (5 mM) in vitro, the rates of ammonia production from enzymatic digests of casein, gelatin, and soy protein (0.5 g of N per liter) were decreased from 46 +/- 2 to 24 +/- 1, 20 +/- 1 to 7 +/- 1, and 40 +/- 2 to 18 +/- 2 nmol/mg of protein per min, respectively. Monensin also caused a decrease in ammonia production in vivo. Nonlactating dairy cows which were fed 0.56 kg of timothy hay 12 times per day had a steady-state ruminal ammonia concentration of 2.7 +/- 0.1 mM, and the ammonia concentration decreased to 1.2 +/- 0.2 mM when monensin (350 mg/day) was added to the diet. The decrease in ammonia production was associated with a 10-fold reduction (4.1 x 10(6) versus 4.2 x 10(5)/ml) in the most probable number of ammonia-producing ruminal bacteria that could use protein hydrolysate as an energy source. Monensin had little effect on the most probable number of carbohydrate-utilizing ruminal bacteria (6.5 versus 7.0 x 10(8)/ml). The addition of protein hydrolysates (560 g) to the rumen caused a rapid increase in the ammonia concentration, but this increase was at least 30% lower when the animals were fed monensin.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗

PubMed1993

Effect of amino acids on the heat production and growth efficiency of Streptococcus bovis: balance of anabolic and catabolic rates.

Streptococcus bovis JB1 grew nearly twice as fast (0.9 versus 1.6 h-1) and had a 40% greater growth yield (18 versus 12.5 mg of protein per mmol of glucose) when an ammonia-based medium was supplemented with amino acids, but the glucose consumption rate (88 mumol mg of protein-1 h-1) and specific rate of heat production (2.1 mW/mg of protein) were unaffected. Amino acid availability had little effect on the catabolic rate, but the specific heat decreased 40% (8.8 to 5.2 J/mg of protein). These growth rate-dependent changes in metabolic efficiency were fivefold greater than the maintenance energy. Chloramphenicol (100 mg/l), an inhibitor of protein synthesis, caused a gradual decrease in anabolic (growth) rate, but there was little change in the rate of glucose consumption and the specific heat increased. When growth was inhibited by iodoacetate, the catabolic and anabolic rates both declined and there was not increase in specific heat. On the basis of these results, the benefit of amino acid supplementation was largely explained by the balance of anabolic and catabolic rates. When amino acids were available, the anabolic and catabolic rates were more closely matched and less energy was spilled as heat.

Amino Acids↗

PubMed1993

Glucose toxicity in Prevotella ruminicola: methylglyoxal accumulation and its effect on membrane physiology.

When the ruminal bacterium prevotella ruminicola B(1)4-M was grown in a defined medium with an excess of glucose (3.6 mM ammonia and 50 mM glucose), the cells accumulated large amounts of cellular polysaccharide and the viable cell number decreased at least 1,000-fold. This decrease in viability was correlated with an accumulation of methylglyoxal in the supernatant (3 to 4 mM). Other genetically distinct strains of P. ruminicola produced methylglyoxal, but methylglyoxal production was not ubiquitous among the strains. When P. ruminicola B(1)4-M was grown in continuous culture (dilution rate, 0.1 h-1) with an excess of glucose, there was an oscillating pattern of growth and cell death which was correlated with the accumulation and washout of methylglyoxal from the culture vessel. Mutants which resisted an excess of glucose took up glucose at a slower rate and produced less methylglyoxal than the wild type. These mutants were, however, not stable. There was always a long lag time, and the mutants could only be maintained with a daily transfer schedule. When the mutants were transferred less frequently, methylglyoxal eventually accumulated and the cultures died. The mutants transported glucose at a threefold-slower rate than the wild type, and in each case the carrier had more than one binding site for glucose. Because glucose transport could not be driven by phosphoenolpyruvate or ATP, the glucose carrier of P. ruminicola is probably a proton symport system. When P. ruminicola B(1)4-M cultures were treated with 4 mM methylglyoxal, the delta psi decreased even though intracellular ATP concentrations were high.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

The effect of monensin supplementation on ruminal ammonia accumulation in vivo and the numbers of amino acid-fermenting bacteria.

When nonlactating Holstein cows (685 +/- 59 kg) were fed chopped timothy hay (9% CP, 7.0 kg/d) 12 times daily, the steady-state ruminal ammonia concentration was 2.6 mM, and the specific activity of ammonia production by mixed ruminal bacteria was 27.4 nmol/mg of protein-1.min-1. The addition of soybean meal (53% CP, 1 or 2 kg/d) to the basal diet caused a linear increase in ruminal ammonia (7.0 and 12.4 mM, respectively; P < .001), but there was only a small increase in the specific activity of ammonia production (30.7 and 33.8 nmol/mg of protein-1.min-1, respectively; P < .05). The addition of monensin (350 mg/d) to the diets caused more than a 30% decrease (P < .01) in ruminal ammonia at all levels of soybean supplementation, and there was a similar decrease (P < .001) in the specific activity of ammonia production. Before monensin addition, the most probable number of bacteria that could utilize peptides and amino acids, but not carbohydrates, as an energy source for growth was 5.8 to 7.0 x 10(6)/mL. When monensin was added to the diets, these bacteria decreased (P < .001) nearly 10-fold. Based on these results, it seemed that monensin inhibited highly active amino acid-fermenting ruminal bacteria, and this inhibition, in turn, decreased ruminal amino acid deamination and ammonia production. Because monensin did not increase soluble protein, peptides, or amino acids in ruminal fluid, it did not seem that the decrease in ammonia increased flow of dietary amino N to the lower gut.(ABSTRACT TRUNCATED AT 250 WORDS)

Ammonia↗

PubMed1993

Another theory for the action of ruminal buffer salts: decreased starch fermentation and propionate production.

Sodium carbonates have been fed to ruminants for more than 20 yr and, in many cases, have alleviated milk fat depression. These effects usually have been ascribed to increased ruminal buffering capacity, but this mode of action has several problems. For the buffering capacity to increase, the concentrations of ruminal bicarbonate, dissolved CO2, and Na have to increase. Ruminal fluid already is saturated with CO2, and the cation concentration of ruminal fluid is regulated closely to prevent hemoconcentration or hemodilution. Based on these latter observations, a significant increase in ruminal buffering capacity is unlikely. The action of bicarbonates is explained more easily by increased water intake, increased ruminal fluid dilution rate, increased flow of undegraded starch from the rumen, and decreased ruminal propionate production.

Animals↗

PubMed1992

The effect of pH on the heat production and membrane resistance of Streptococcus bovis.

Non-growing cultures of Streptococcus bovis JB1 which were incubated in 2-[N-moropholino] ethane-sulfonic acid (MES)-phosphate buffer (pH 6.8) and glucose (2 g/l) produced heat at a rate of 0.17 mW/mg protein, and this rate was proportional to the enthalpy change of the homolactic fermentation. Since the growth-independent heat production could be eliminated by dicyclohexylcarbodiimide (DCCD), an inhibitor of F1F0 ATPases, it appeared that virtually all of the energy was being used to counteract proton flux through the cell membrane. When the pH was decreased from 6.8 to 5.8, heat production and glucose consumption increased, the electrical potential (delta psi) declined, the chemical gradient of protons (Z delta pH) increased, and there was a small increase in total protonmotive force (delta p). Further decreases in pH (5.8 to 4.5) caused a marked decrease in heat production and glucose consumption even though there was only a small decline in membrane voltage. Based on the enthalpy of ATP (4 kcal or 16.8 kJ/mol), it appeared that 38% of the wattage was passing through the cell membrane. The relationship between membrane voltage and membrane wattage or glucose consumption was non-linear (non-ohmic), and it appeared that the resistance of the membrane to current flow was not constant. Based on the electrical formula, resistance = voltage2/wattage and resistance = voltage/amperage, there was a marked increase in membrane resistance when the pH was less than 6.0. The increase in membrane resistance at low pH allowed S. bovis to maintain its membrane potential and expend less energy when its ability to ferment glucose was impaired.

Cell Membrane↗

PubMed1992

Laser micromanipulation in the mouse embryo: a novel approach to zona drilling.

OBJECTIVE: To introduce the use of excimer lasers for penetration of the zona pellucida for micromanipulation purposes. DESIGN: Cryopreserved two-cell mouse embryos were thawed and exposed to the 248-nm line of a krypton fluoride excimer laser (Lambda Physik EMG 202, Goettingen, Germany) creating a 2 to 4-micron opening in the zona pellucida. SETTING: The Laser Ablation Laboratory at DuPont and the in Vitro Fertilization Laboratory at The Medical Center. INTERVENTIONS: The embryos were exposed in either phosphate-buffered solution (PBS) or modified human tubal fluid (HTF) with the laser power varying from 1 to 2 J/cm2 and cultured in Ham's F-10 medium (GIBCO, Grand Island, NY) with 0.4% bovine serum albumin. MAIN OUTCOME MEASURES: The outcome of each experiment was measured by blastocyst formation of laser-exposed embryos as compared with a set of unexposed control embryos handled in a similar fashion. RESULTS: Successful laser penetration of the zona pellucida was achieved using the 248-nm line of a krypton fluoride excimer laser. A higher blastocyst formation was found for embryos exposed in PBS. The higher optical absorption of the modified HTF partially inhibited embryo development. The blastocyst statistics increased 2.5-fold times by reducing the exposure of the embryos to ablation by-products. CONCLUSIONS: The use of a krypton fluoride excimer laser was introduced as a new method to open the zona pellucida of two-cell mouse embryos without interrupting blastocyst formation.

Animals↗

PubMed1992

Properties of a genetically reconstructed Prevotella ruminicola endoglucanase.

A pUC19-derived plasmid was constructed that coded for a hybrid cellulase with the Thermomonospora fusca E2 cellulose-binding domain at its C terminus joined to the Prevotella ruminicola 40.5-kDa carboxymethyl cellulase (CMCase). The hybrid enzyme was purified and characterized enzymatically. It bound tightly to cellulose, and its specific activities on carboxymethyl cellulose, amorphous cellulose, and ball-milled cellulose were 1.5, 10, and 8 times that of the 40.5-kDa CMCase, respectively. Furthermore, the modified enzyme gave synergism with an exocellulase in the degradation of filter paper, while the 40.5-kDa CMCase did not.

Actinomycetales↗

PubMed1992

Resistance of proline-containing peptides to ruminal degradation in vitro.

Mixed ruminal bacteria utilized an enzymatic digest of casein at a rate faster than that for an enzymatic digest of gelatin, but neither amino acid source was completely utilized even when the incubation period was as long as 96 h. Since the reaction of ninhydrin with the residual nonammonia, nonprotein nitrogen was more than twofold stronger when the samples were hydrolyzed with 6 N HCl, it appeared that much of the residual nitrogen was from peptides. Approximately 66% of the nonammonia, nonprotein, ninhydrin-reactive material could not be recovered as amino acids, but there was a significant decrease in total amino acid nitrogen when the samples were pretreated with a C18 Sep-Pak column to remove peptides. The resistant peptides had an abundance of proline, and subsequent incubations showed that synthetic dipeptides which contained proline were hydrolyzed slowly. Lysine appears to be the amino acid which is most apt to limit ruminant production. Dipeptides containing proline and lysine were hydrolyzed at least fivefold slower than lysine-alanine. Methionine, another potentially limiting amino acid, was also degraded at a slower (2.5-fold) rate when it was present as part of a proline dipeptide.

Animals↗

PubMed1992

Energetics of arginine and lysine transport by whole cells and membrane vesicles of strain SR, a monensin-sensitive ruminal bacterium.

Strain SR, a monensin-sensitive, ammonia-producing ruminal bacterium, grew rapidly on arginine and lysine, but only if sodium was present. Arginine transport could be driven by either an electrical potential or a chemical gradient of sodium. Arginine was converted to ornithine, and it appeared that ornithine efflux created a sodium gradient which in turn drove arginine transport. There was a linear decline in arginine transport as pH was decreased from 7.5 to 5.5, and the cells did not grow at a pH less than 6.0. The Eadie-Hofstee plot was biphasic, and arginine could also be taken by a high-capacity diffusion mechanism. Because arginine was a strong inhibitor of lysine transport and lysine was a weak inhibitor of arginine transport, it appeared that both lysine and arginine were taken up by an arginine-lysine carrier which had a preference for arginine. The rate of lysine fermentation was always proportional to the extracellular lysine concentration, and facilitated diffusion was the dominant mechanism of lysine transport. When SR was grown in continuous culture on arginine or lysine, the theoretical maximal growth yield was similar (13 g of cells per mol of ATP), but the apparent maintenance energy requirement for arginine was greater than lysine (9.4 versus 4.4 mmol of ATP per g of cells per h). On the basis of differences in yield and maintenance energy, it appeared that active arginine transport accounted for approximately 40% of the total ATP.

Animals↗

PubMed1992

Effect of pH and Monensin on Glucose Transport by Fibrobacter succinogenes, a Cellulolytic Ruminal Bacterium.

Fibrobacter succinogenes S85, a cellulolytic ruminal bacterium, required sodium for growth and glucose uptake. Cells which were deenergized with iodoacetate (500 muM) could not take up [C]glucose. However, deenergized cells which were treated with valinomycin, loaded with potassium, and diluted into sodium or sodium plus potassium to create an artificial electrical gradient (DeltaPsi) plus a chemical gradient of sodium (DeltapNa) or DeltapNa alone transported glucose at a rapid rate. Cells which were loaded with potassium plus sodium and diluted into sodium (DeltaPsi with sodium, but no DeltapNa) also took up glucose at a rapid rate. Potassium-loaded cells that were diluted into buffers which did not contain sodium (DeltaPsi without sodium) could not take up glucose. An artificial ZDeltapH which was created by acetate diffusion could not drive glucose transport even if sodium was present. The maximum rate and affinity of glucose transport (pH 6.7) were 62.5 nmol/mg of protein per min and 0.51 mM, respectively. S85 was unable to grow at a pH of less than 5.5, and there was little glucose transport at this pH. When the extracellular pH was decreased, the glucose carrier was inhibited, intracellular pH declined, the cells were no longer able to metabolize glucose, and DeltaPsi declined. Monensin (1 muM) or lasalocid (5 muM) decreased intracellular ATP and dissipated both the DeltaPsi and DeltapNa. Since there was no driving force for transport, glucose transport was inhibited. These results indicated that F. succinogenes used a pH-sensitive sodium symport mechanism to take up glucose and that either a DeltaPsi or a DeltapNa was required for glucose transport.

Journal Article↗