Basal oxygen consumption,ventilatory frequency,and heart rate during the protracted spawning run of the Southern Hemisphere lamprey Geotria australis

Summary Basal oxygen consumption, ventilatory frequency, and heart rate were recorded at four different times during the unusually protracted 15–16-month spawning run of the Southern Hemisphere lamprey Geotria australis. At 15°C, the mean basal oxygen consumption of G. australis caught immediately after they had left the sea and embarked on the spawning run (45 l · g^-1 · h^-1) was less than in young adults about to commence their marine feeding phase (64 l · g^-1 · h^-1), but greater than in large ammocoetes (26.5 l · g^-1 · h^-1). Basal oxygen consumption fell progressively during the spawning-run of to 33 l · g^-1 · h^-1 after 5 months and 25 l · g^-1 · h^-1 after 10 months, before rising to 35 l · g^-1 · h^-1 after 15 months when the animals were approaching sexual maturity. The downwards trend in basal oxygen consumption contrasts with that recorded during the spawning run of Lampetra fluviatilis. Furthermore, these values for spawning-run of G. australis are far lower than those measured at any time during the upstream migration of L. fluviatilis or during the parasitic phase of landlocked Petromyzon marinus. A low and declining metabolic rate during much of the spawning run of G. australis would facilitate the conservation of energy reserves during this very long non-feeding period. Trends shown by ventilatory frequency and heart rate essentially parallel those of basal oxygen consumption. The Q₁₀s for basal oxygen consumption, ventilatory frequency and heart rate over the temperature range 5–25°C were 1.6, 1.6, and 1.7, respectively. The trends shown by basal oxygen consumption during metamorphosis and the upstream migration did not parallel those exhibited by circulating thyroid hormones.     

Dependency of growth yield,maintenance and K s-values on the dissolved oxygen concentration in continuous cultures of Azotobacter vinelandii

Azotobacter vinelandii was grown diazotrophically in sucrose-limited chemostat cultures at either 12, 48, 108, 144 or 192 M dissolved oxygen. Steady state protein levels and growth yield coefficients (Y) on sucrose increased with increasing dilution rate (D). Specific rate of sucrose consumption (q) increased in direct proportion to D. Maintenance coefficients (m) extrapolated from plots of q versus D, as well as from plots of 1/Y versus 1/D exhibited a nonlinear relationship to the dissolved oxygen concentration. Constant maximal theoretical growth yield coefficients (Y ^G) of 77.7 g cells per mol of sucrose consumed were extrapolated irrespective of differences in ambient oxygen concentration. For comparison, glucose-, as well as acetate-limited cultures were grown at 108 M oxygen. Fairly identical m- and Y ^G-values, when based on mol of substrate-carbon with glucose and sucrose grown cells, indicated that both substrates were used with the same efficiency. However, acetate-limited cultures showed significantly lower m- and, at comparable, D, higher Y-values than cultures limited by either sucrose or glucose. Substrate concentrations (K _s) required for half-maximal growth rates on sucrose were not constant, they increased when the ambient oxygen concentration was raised and, at a given oxygen concentration, when D was decreased. Since biomass levels varied in linear proportion to K _s these results are interpreted in terms of variable substrate uptake activity of the culture.Abbreviations D dilution rate - K _s substrate concentration required for half maximal growth rate - m maintenance coefficient - q specific rate of substrate consumption - Y growth yield coefficient - Y ^G maximum theoretical growth yield coefficient     

Myocardial oxygen consumption and mechanical efficiency of a perfused dogfish heart preparation

Summary Oxygen consumption of an in-pericardium heart preparation from the spiny dogfish (Squalus acanthias) was linearly related to cardiac power output. Basal oxygen consumption, predicted from the regression, was 0.127 l · s^-1 · g ventricle mass^-1 and increased by 0.189 l · s^-1 · g ventricle mass^-1 per milliwatt of power generated. From the relationship between cardiac power output and mechanical efficiency, mechanical efficiency was predicted to increase with cardiac power output to a maximum of 21 %. Mechanical efficiency was measured during volume loading and pressure loading at two power outputs (50% and 72% of maximum power output). At 50% of maximum power output, mechanical efficiency increased significantly by 2.87%, from 11.9±0.3% to 14.8±0.5% (n=7), when flow was halved and output pressure doubled to achieve the same power output. Similarly, at 72% of maximum power output, mechanical efficiency increased from 14.74±0.92% to 17.61±0.84% (n=6) when flow was halved and output pressure doubled to generate the same higher level of power output. The increased mechanical efficiency at higher output pressures is believed to result from cardiac myocytes working within a length range where they are able to generate the most tension during contraction and are most efficient. We speculate that the loss of mechanical efficiency associated with large changes in sarcomere length, when stroke volume is large, is a driving force behind the use of frequency as the principal means of increasing cardiac output as observed in more active fishes, birds and mammals.Abbreviations BM body mass - CO cardiac output - HR heart rate - P _i mean cardiac input pressure - P _o mean cardiac output pressure - PO partial pressure of oxygen - SV stroke volume of heart - VM ventricle mass     

Protein synthesis and oxygen consumption in fish cells

Oxygen consumption and protein synthesis were measured concurently in four fish cell types: BF-2 and TRG-2 cell lines, rainbow trout macrophages and scale cells. The fractional rates of protein synthesis (percentage of the protein mass synthesised per day) were ranked: BF-2 cells > macrophages > RTG-2 cells > scale cells. Oxygen consumption rates were ranked BF-2 cells = macrophages = RTG-2 cells > scale cells. Within three of the cell types (BF-2, RTG-2 and scale cells) oxygen consumption and protein synthesis were linearly correlated, whereas comparison between the four cell types gave rise to an exponential relationship between fractional rates of protein synthesis and oxygen consumption. Inhibition of protein synthesis with cycloheximide by 41–65% resulted in a 62–89% reduction in oxygen consumption depending on cell type. Calculations of the aerobic cost of protein synthesis using the cycloheximide-sensitive protein synthesis and oxygen consumption rates resulted in estimates ranging from 11 to 217 mol O₂·mg protein^-1 synthesised depending on the cell type. The lowest net protein synthesis costs, which are close to theoretical values for peptide bond formation, were associated with the most rapid rates of protein synthesis.Abbreviations ANOV A analysis of variance - BDH British Drug Housing - BOC British Oxygen Company - ADT A ethylenediaminetetra-acetic acid - FCS foetal calf serum - HEPES N-[2-hydroxyethyl] piperazine-N-[2-ethane-sulphonic acid] - LCD least square differnece - MEM munimum essential media - PBS phosphate-buffered saline - PCA perchloric acid - SIS spectral index of the sample - tSIE transformed spectral index of the external standard spectrum     

Sulfate formation via ATP sulfurylase in thiosulfate- and sulfite-disproportionating bacteria

Disproportionation of thiosulfate or sulfite to sulfate plus sulfide was found in several sulfate-reducing bacteria. Out of nineteen strains tested, eight disproportionated thiosulfate, and four sulfite. Growth with thiosulfate or sulfite as the sole energy source was obtained with three strains (Desulfovibrio sulfodismutans and the strains Bra02 and NTA3); additionally, D. desulfuricans strain CSN grew with sulfite but not with thiosulfate, although thiosulfate was disproportionated. Two sulfur-reducing bacteria, four phototrophic sulfur-oxidizing bacteria (incubated in the dark), and Thiobacillus denitrificans did not disproportionate thiosulfate or sulfite. Desulfovibrio sulfodismutans and D. desulfuricans CSN formed sulfate from thiosulfate or sulfite even when simultaneously oxidizing hydrogen or ethanol, or in the presence of 50 mM sulfate. The capacities of sulfate reduction and of thiosulfate and sulfite disproportionation were constitutively present. Enzyme activities required for sulfate reduction (ATP sulfurylase, pyrophosphatase, APS reductase, sulfite reductase, thiosulfate reductase, as well as adenylate kinase and hydrogenase) were detected in sufficient activities to account for the growth rates observed. ADP sulfurylase and sulfite oxidoreductase activities were not detected. Disproportionation was sensitive to the uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP) but not to the ATPase inhibitor dicyclohexylcarbodiimide (DCCD). It is proposed that during thiosulfate and sulfite disproportionation sulfate is formed via APS reductase and ATP sulfurylase, but not by sulfite oxidoreductase. Reversed electron transport must be assumed to explain the reduction of thiosulfate and sulfite by the electrons derived from APS reductase.Abbreviations CCCP Carbonylcyanide m-chlorophenylhydrazone - DCCD N,N-dicyclohexylcarbodiimide - APS adenosine 5-phosphosulfate (adenylylsulfate)     

Competition for limiting amounts of oxygen between Nitrosomonas europaea and Nitrobacter winogradskyi grown in mixed continuous cultures

Chemolithotrophic nitrifying bacteria are dependent on the presence of oxygen for the oxidation of ammonium via nitrite to nitrate. The success of nitrification in oxygen-limited environments such as waterlogged soils, will largely depend on the oxygen sequestering abilities of both ammonium- and nitrite-oxidizing bacteria. In this paper the oxygen consumption kinetics of Nitrosomonas europaea and Nitrobacter winogradskyi serotype agilis were determined with cells grown in mixed culture in chemostats at different growth rates and oxygen tensions.Reduction of oxygen tension in the culture repressed the oxidation of nitrite before the oxidation of ammonium was affected and hence nitrite accumulated. K _m values found were within the range of 1–15 and 22–166 M O₂ for the ammonium- and nitrite-oxidizing cells, respectively, always with the lowest values for the N. europaea cells. Reduction of the oxygen tension in the culture lowered the half saturation constant K _m for oxygen of both species. On the other hand, the maximal oxygen consumption rates were reduced at lower oxygen levels especially at 0 kPa. The specific affinity for oxygen indicated by the V _max/K _m ratio, was higher for cells of N. europaea than for N. winogradskyi under all conditions studied. Possible consequences of the observed differences in specific affinities for oxygen of ammonium-and nitrite-oxidizing bacteria are discussed with respect to the behaviour of these organisms in oxygen-limited environments.     

Immunoreactivity of the corpuscles of Stannius of the garpike,Lepisosteus osseus,to antisera against salmon and trout stanniocalcins

Stanniocalcin-immunoreactive cells were localized in the corpuscles of Stannius of a holostean fish, the garpike (Lepisosteus osseus), using antisera against salmon and trout stanniocalcins and the peroxidase-antiperoxidase and protein A-gold immunohistochemical methods. The stanniocalcin-immunoreactive cells were periodic acid-Schiff-positive, and antibody staining was abolished if the antiserum was preabsorbed with corpuscle homogenate. Immunocytochemistry revealed two reactive cell types in the glandular parenchyma, and immunoreactivity was confined to the secretory granules. Staining of the granules was also abolished when the antisera were blocked with crude corpuscle homogenate. When corpuscle extracts from garpike were subjected to sodium dodecyl sulphate-polyacrylamide gel electrophoresis and Western blot analysis, a single dense band was evident with a molecular weight of 68 kDa under non-reducing conditions, whereas three bands were observed (29, 31, and 34 kDa) under reducing conditions. Staining of all bands disappeared following preabsorption of the antiserum with salmon stanniocalcin, trout stanniocalcin, or garpike corpuscle extract. The results are compared with stanniocalcins from another extant holostean, the bowfin (Amia calva), and from more modern bony fishes, the teleosts.     

Glyoxylate decreases the oxygen sensitivity of nitrogenase activity and photosynthesis in the cyanobacterium Anabaena cylindrica

Raising the pO₂ reduced nitrogenase activity (C₂H₂ reduction) of Anabaena cylindrica for both glyoxylate-treated (5 mM) and untreated cells. The stimulation caused by glyoxylate, however, increased with increases of pO₂ from 2 to 99 kPa. As the pO₂ increased the net CO₂ fixation was lowered (Warburg effect) while the CO₂ compensation point increased. Glyoxylate partly relieved this sensitivity of net photosynthesis to oxygen and reduced the compensation point considerably. The cells used were preincubated in the dark to exhaust photosynthetic pools. A more pronounced reduction in sensitivity of nitrogenase to oxygen for glyoxylate-treated cells was evident when a preincubation in air with reduced pCO₂ (13 l l^-1) was used. This was, however, not evident until after a 10-h incubation in air. Before this point 2 kPa O₂ sustained the highest nitrogenase activity. Addition of 0.5 and 5 mM of HCO ₃ ^- to Anabaena cultures preincubated at low CO₂ levels (29 l l^-1) abolished the stimulatory effect of glyoxylate on the nitrogenase. Thus, the results sustain the suggestion that glyoxylate may act as an inhibitor of photorespiratory activities in cyanobacteria and can be used as a means of increasing their nitrogen and CO₂ fixation capacities.Abbreviation RuBP ribulose 1,5-bisphosphate     

DNA and RNA strand scission by copper, zinc and manganese superoxide dismutases

Copper/zinc (Cu/ZnSOD) and manganese (MnSOD) superoxide dismutases which catalyze the dismutation of toxic superoxide anion, O _inf2 ^sup– , to O₂ and H₂O₂, play a major role in protecting cells from toxicity of oxidative stress. However, cells overexpressing either form of the enzyme show signs of toxicity, suggesting that too much SOD may he injurious to the cell. To elucidate the possible mechanism of this cytotoxicity, the effect of SOD on DNA and RNA strand scission was studied. High purity preparations of Cu/ZnSOD and MnSOD were tested in an in vitro assay in which DNA cleavage was measured by conversion of phage X174 supercoiled double-stranded DNA to open circular and linear forms. Both types of SOD were able to induce DNA strand scission generating single- and double-strand breaks in a process that required oxygen and the presence of fully active enzyme. The DNA strand scission could be prevented by specific anti-SOD antibodies added directly or used for immunodepletion of SOD. Requirement for oxygen and the effect of Fe(II) and Fe(III) ions suggest that cleavage of DNA may be in part mediated by hydroxyl radicals formed in Fenton-type reactions where enzyme-bound transition metals serve as a catalyst by first being reduced by superoxide and then oxidized by H₂O₂. Another mechanism was probably operative in this system, since in the presence of magnesium DNA cleavage by SOD was oxygen independent and not affected by sodium cyanide. It is postulated that SOD, by having a similar structure to the active center of zinc-containing nucleases, is capable of exhibiting non-specific nuclease activity causing hydrolysis of the phosphodiester bonds of DNA and RNA. Both types of SOD were shown to effectively cleave RNA. These findings may help explain the origin of pathology of certain hereditary diseases genetically linked to Cu/ZnSOD gene.     

Asymbiotic association of Rhizobium with pea epicotyls treated with a plant hormone

Treatment of epicotyls of dark-grown pea (Pisum sativum L.) seedlings with indole-3-acetic acid causes swelling of the tissue. Application of Rhizobium to the cut surface of the swollen tissue results in the development of an infection. The infection spreads in the cortical cells and proceeds 2–3 mm deep into the stem within 3–4 days. An acetylene reduction assay used for detecting nitrogen-fixation capacity of the infected tissue was negative at 10% [O₂]; however, if [O₂] was reduced to below 1%, some activity could be detected. Ultrastructural observations indicate that the cytoplasmic contents of the infected cells are destroyed and no membrane structure around the bacteria is formed during this infection. Rhizobium does not appear to have developed any symbiotic relationship with the host. Failure to develop symbiosis appears to result in a parasitic or saprophytic association and the nitrogen fixed under such conditions may not be of any use to the plant.     

Inhibition of nitrate reduction by light and oxygen in Rhodobacter sphaeroides forma sp. denitrificans

Light inhibited each step of the denitrification process in whole cells of Rhodobacter sphaeroides forma sp. denitrificans. This inhibition by light was prevented in the presence of exogenous electron donors like N,N,N,N-tetramethyl-p-phenylenediamine (TMPD) plus ascorbate or in the presence of an uncoupler (carbonyl cyanide m-chlorophenylhydrazone). Addition of myxothiazol restored the inhibition by light in uncoupled cells. Measurements of light-induced absorbance changes under these conditions showed that this inhibition is due, for the steps of reduction of nitrite to dinitrogen, to the photooxidation of cytochromes c ₁ plus c ₂ and not due to the photoinduced membrane potential. Moreover, the presence of oxygen inhibited almost all of the reduction of nitrate and nitrous oxide but only 70% of the reduction of nitrite to nitrous oxide. These inhibitions were overcome in the presence of TMPD plus ascorbate. This implies that the inhibition in presence of oxygen was due to a diversion of the reducing power from the denitrifying chain to the respiratory chain. It was concluded from this series of experiments that the reduction of nitrate to nitrite is inhibited when the ubiquinone pool is partly oxidized and that nitrite and nitrous oxide reductions are inhibited when cytochromes c ₁ plus c ₂ are oxidized by photosynthesis or respiration.Abbreviations R Rhodobacter - TMPD N,N,N,N-tetramethyl-p-phenylenediamine - HOQNO 2-n-heptyl-4-hydroxyquinoline N-oxide - CCCP carbonyl cyanide m-chlorophenylhydrazone - cytochrome c ₁ cytochrome c ₂ plus cytochrome c ₁     

The activity of powdery-mildew haustoria after feeding the host cells with different sugars,as measured with a potentiometric cyanine dye

The biotrophic parasite Erysiphe graminis f. sp. hordei produces haustoria within the cells of its host Hordeum vulgare. To determine the physiological activity of these haustoria, the electric potential across the membranes in the mitochondria of the haustorium was studied. The membrane potential was estimated with the fluorescent potentiometric cyanine dye 3,3-dibutyloxacarbocyanine iodide. The addition of depolarizing agents (carbonylcyanide m-chlorophenylhydrazone, 2,4-dinitrophenol or KCN) to infected cells resulted in an increase of fluorescence after the addition of low concentrations or a decrease of fluorescence after the addition of higher concentrations. When the infected host cell was fed with increasing concentrations of d-glucose (25, 50, 75 mM), corresponding decreases of fluorescence were measured immediately in the mitochondria of the fungal haustoria. Sucrose induced a similar reduction of fluorescence about 20 min late. d-Galactose and d-fructose induced a somewhat smaller reduction of fluorescence, l-glucose and d-glucitol had no effect. The results indicate that haustoria take up glucose from the host cells immediately. Sucrose, d-galactose and d-fructose seem to require time to be metabolized before their products reach the fungal haustorium or mitochondria.Abbreviations CCCP carbonylcyanide m-chlorophenylhydrazone - DiOC₄(3) 3,3-dibutyloxacarbocyanine iodide - DNP 2,4-dinitrophenol     

Cytokinin inhibition of respiration by cells and mitochondria of soybean,Glycine max (L.) Merrill

Cells of a soybean tissue strain, suspended in an aerated liquid medium, caused disappearance of p-coumaric acid from the medium and oxidation of guaiacol, benzidine, pyrogallol, L-dihydroxyphenylalanine and L-epinephrine. Both the disappearance and the oxidations were inhibited by 6-benzylaminopurine (BAP) at a concentration of 0.5 mM. BAP at other concentrations either promoted or inhibited oxidation of epinephrine in precisely the pattern reported earlier for the disappearance of coumarate; therefore, the disappearance of coumarate probably involves its oxidation. The effectiveness of other cytokinins in inhibiting the oxidation was studied.At 0.5 mM, and perhaps even at 0.5 M, some of the several cytokinins tested inhibited oxygen consumption by the soybean cells. This inhibition, which did not require any of the above metabolizable compounds, was especially marked in the presence of cyanide, azide or Antimycin A, and was detectable in 10 min or less. Either Antimycin A or salicylhydroxamic acid alone promoted O₂ consumption but together they were quite inhibitory. The soybean cells apparently have an alternate respiratory pathway and cytokinins may influence its operation.Several cytokinins at 0.5 mM, and perhaps at 0.5 M, also inhibited oxygen consumption by mitochondrial preparations from the soybean cells, the inhibition being evident in about 20 s. The consumption required a substrate such as malate, succinate or NADH. Cytokinins and related compounds varied in effectiveness as follows: BAP and 6-isopentenyla-minopurine 9-tetrahydropyranyl-BAP > kinetin, ribosyl-isopentenylaminopurine, 9-methyl-BAP and 9-methoxymethyl-BAP > 6,6-dimethylaminopurine and zeatin (slight activity) > 6-methylaminopurine, nicotinamide and adenine (ineffective). To a great extent this order parallels the order of effectiveness of the compounds in causing cell division. Mitochondria, therefore, may contain a site for an important cytokinin action.Abbreviations BAP 6-benzylaminopurine - IPA 6-(²-isopentenyl)aminopurine     

Evaluation of monitoring approaches and effects of culture conditions on recombinant protein production in baculovirus-infected insect cells

The baculovirus infection process ofSpodoptera frugiperda (Sf9) insect cells in oxygen-controlled bioreactors in serum-free medium was investigated using a recombinantAutographa californica (AcNPV) virus expressing -galactosidase enzyme as a model system. A variety of monitoring techniques including trypan blue exclusion, fluorescent dye staining, oxygen uptake rate (OUR) measurements, and glucose consumption were applied to infected cells to determine the best way of evaluating cell integrity and assessing the course of baculovirus infection. The metabolism of newly-infected cells increased 90% during the first 24 hours, but as infection proceeded, and cells gradually succumbed to the baculovirus infection, the cytopathic effect of the baculovirus on the cells became evident. Oxygen and glucose uptake rate measurements appeared to more accurately assess the condition of infected cells than conventional trypan blue staining, which tended to overestimate cell viability in the mid stages of infection. The optimal harvest time varied, depending on which technique — SDS-PAGE, chromogenic (ONPG) or fluorometric (C₁₂FDG) — was used to monitor -galactosidase production. Specific -galactosidase production was found to be insensitive to a wide range of culture dissolved oxygen tensions, whereas resuspending cells in fresh medium prior to infection increased volumetric productivity approximately two-fold (800,000 units -galactosidase/ml) compared to cultures infected in batch mode and allowed successful infections to occur at higher cell densities.Abbreviations ONPG ortho-phenyl 2--D-galactopyranoside - OUR oxygen uptake rate (-mol O₂/liter/hour) - q_glucose specific glucose uptake rate (mg glucose/10⁶cell/hour) - q_glutamine specific glutamine uptake rate (mg glutamine/10⁶cell/hour) - qO₂ specific oxygen uptake rate (-mol O₂/10⁶cell/hour) - MOI virus multiplicity of infection (viral plaque forming units/cell)     

Physiology of nitrogen fixation in Azospirillum lipoferum Br 17 (ATCC 29 709)

Changes of cellular activities during batch cultures with Azospirillum lipoferum strain Br 17 (ATCC 29 709) were observed within the growth cycle, at optimal pO₂ (0.002–0.003 atm). The relative growth rate for cells growing with N₂ as sole nitrogen source during log phase was =0.13 h^-1 and the doubling time was 5.3 h. Nitrogenase activity was not accompanied by hydrogen evolution at any growth stage, and a very active uptake hydrogenase was demonstrated. The hydrogenase activity increased towards the end of the growth period when glucose became limiting and N₂ fixation reached its maximal specific activity. Oxygen consumption and oxygen tolerance at the various growth stages, increased simultaneously with the uptake hydrogenase activity indicating a possible role of this enzyme in an oxygen protection mechanism of A. lipoferum nitrogenase. The efficiency of nitrogen fixation expressed as mg total nitrogen fixed in cells and supernatant per g glucose consumed, was 20 at the early log phase and increased to 48 at the late log phase. About 25% of the total fixed nitrogen was recovered in the culture supernatant.Abbreviations DOT Dissolved oxygen tension - PHB Poly--hydroxybutyric acid - O.D. Optical density (560 nm) - A.T.C.C. American type culture collection - NTA Nitrilotriacetic acid Graduate student of the Universidade Federal Rural do Rio de Janeiro, Brazil     

Oxygen consumption of the lobster,Homarus americanus milne-edwards

Summary 1. Oxygen consumption by a group of 25 lobsters was essentially constant over a range of ambient oxygen concentrations from 1.0 to 8.5 mg/l. Consumption by groups of 35 and 50 lobsters at 15° C decreased as the concentration decreased.2. Oxygen consumption by individuals at 10° and 15° C increased as the oxygen concentration increased.3. Oxygen consumption increased as activity increased with crowding.4. Oxygen consumption almost doubled after feeding.5. Oxygen consumption per unit weight decreased with increasing size.6. The average rate of oxygen consumption by individuals doubled over the temperature range 12° to 25° C.7. Oxygen consumption in air at 6° to 25° C was much less than in water.

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Sauerstoffverbrauch des HummersHomarus americanus Milne-Edwards

Kurzfassung Bei einer Gruppe von 25 Hummern wurde der Sauerstoffverbrauch in Dauerfluß-Respirometern gemessen. Bei 10° C erwies er sich als im wesentlichen konstant über einen Bereich der Sauerstoffkonzentration im umgebenden Wasser von 1,0 bis 8,5 mg/l. Bei Gruppen von 35 und 50 Hummern, welche bei 15° C getestet wurden, nahm der Sauerstoffverbrauch jedoch mit fallender Sauerstoffkonzentration etwas ab. Anstieg der Individuenzahl pro Raumeinheit (crowding) führte zu steigender Bewegungsaktivität und zu erhöhtem Sauerstoffverbrauch. Nahrungsaufnahme verursachte fast eine Verdoppelung des Sauerstoffverbrauchs. Kleine Individuen verbrauchen pro Gewichtseinheit mehr Sauerstoff als große. In manometrischen Respirometern stieg der Sauerstoffverbrauch bei hohen Sauerstoffkonzentrationen im umgebenden Wasser mit der Temperatur. Bei 6° bis 25° C war der Sauerstoffverbrauch in der Luft wesentlich geringer als im Wasser.

     

Effect of oxygen on the metabolism of Zymomonas mobilis

The specific growth rate of the ethanol producing bacterium Zymomonas mobilis was 25–40% lower in the presence of oxygen than under anaerobic conditions, provided the cultures were supplied with a low substrate concentration (20 g glucose/l). However, the molar growth yield of these cultures was not influenced by oxygen. With washed cell suspensions, an oxygen consumption could be initiated by the addition of either glucose, fructose, or ethanol. Cell extracts catalyzed the oxidation of NADH with oxygen at a molar ratio of 2:1. Further experiments showed that this NADH oxidase is located in the cell membrane. The specific oxygen consumption rates of cell suspensions correlated with the intracellular NADH oxidizing activities; both levels decreased with increasing concentrations of the fermentation end-product ethanol. The addition of 5 mM NaCN completely inhibited both the intracellular oxygen reduction and also the oxygen consumption of whole cells. Both catalase and superoxide dismutase were present even in anaerobically grown cells. Aeration seemed to have little effect on the level of catalase, but the superoxide dismutase activity was 5-fold higher in cells grown aerobically. Under aerobic conditions considerable amounts of acetaldehyde and acetic acid were formed in addition to the normal fermentation products, ethanol and carbon dioxide.Dedicated to Professor Dr. H. G. Schlegel on the occasion of his 60th birthday     

Elemental sulfur as an intermediate of sulfide oxidation with oxygen byDesulfobulbus propionicus

The sulfate-reducing bacteriumDesulfobulbus propionicus oxidized sulfide, elemental sulfur, and sulfite to sulfate with oxygen as electron acceptor. Thiosulfate was reduced and disproportionated exclusively under anoxic conditions. When small pulses of oxygen were added to washed cells in sulfide-containing assays, up to 3 sulfide molecules per O₂ disappeared transiently. After complete oxygen consumption, part of the sulfide reappeared. The intermediate formed was identified as elemental sulfur by chemical analysis and turbidity measurements. When excess sulfide was present, sulfur dissolved as polysulfide. This process was faster in the presence of cells than in their absence. The formation of sulfide after complete oxygen consumption was due to a disproportionation of elemental sulfur (or polysulfide) to sulfide and sulfate. The uncoupler tetrachlorosalicylanilide (TCS) and the electron transport inhibitor myxothiazol inhibited sulfide oxidation to sulfate and caused accumulation of sulfur. In the presence of the electron transport inhibitor 2-n-heptyl-4-hydroxyquinoline-N-oxide (HQNO), sulfite and thiosulfate were formed. During sulfur oxidation at low oxygen concentrations, intermediary formation of sulfide was observed, indicating disproportionation of sulfur also under these conditions. It is concluded that sulfide oxidation inD. propionicus proceeds via oxidation to elemental sulfur, followed by sulfur disproportionation to sulfide and sulfate. Dedicated to Prof. Dr. Dr. h.c. Norbert Pfennig on the occasion of his 70th birthday     

Adenine nucleotide contents and energy charge of Azotobacter vinelandii grown at low phosphate concentration

The effect of a low phosphate concentration on intracellular adenine nucleotide content, oxygen consumption and poly--hydroxybutyrate deposition was investigated with N-free and NH ₄ ⁺ batch cultures of Azotobacter vinelandii. When the microorganisms were cultured under low-phosphate concentrations the cells contained much larger amounts of poly--hydroxybutyrate, but displayed lower oxygen consumption activities and energy charge values than did control cells. Also, the ratio ATP to ADP was much higher in control cells and the intracellular levels of ATP were lower in low-phosphate cells.     

Fungal elicitors induce a transient release of active oxygen species from cultured spruce cells that is dependent on Ca2+ and protein-kinase activity

Cell-wall components from the ectomycorrhizal fungi Amanita muscaria and Hebeloma crustuliniforme and from the spruce pathogen Heterobasidion annosum elicited a transient release of active oxygen species from cultured spruce cells (Picea abies (L.) Karst.). Since the detection of active oxygen was suppressed by catalase, H₂O₂ was assumed to be the prevailing O₂ species. On the other hand, superoxide dismutase enhanced the concentration of detectable H₂O₂ indicating that the superoxide anion was formed before dismutating to H₂O₂. The elicitors induced the formation of active oxygen in a dose-dependent manner. Interestingly, elicitors from mycorrhizal fungi had a lower H₂O₂-inducing activity than equal amounts of cell-wall preparations from the pathogen H. annosum. In Ca²⁺-depleted medium the production of active oxygen by elicitor-treated spruce cells was suppressed. Additionally, the ionophore A 23187 induced active oxygen formation in a medium with Ca²⁺ but not in a Ca²⁺-depleted medium. Furthermore, the protein-kinase inhibitor staurosporine inhibited the oxidative burst. At a concentration of 34 nM the effect was diminished to 50%. From these results it is suggested that the release of active oxygen species from cultured spruce cells triggered by cell-wall-derived fungal elicitors depends on external Ca²⁺ and a protein-kinase activity. In these respects the effect shows similarities with the well-studied respiratory burst of mammalian neutrophils.Abbreviations EGTA ethylene glycol-bis(-aminoethyl ether)-N,N,N,N-tetraacetic acid - KP_i potassium phosphate This work was supported by grants from Deutsche Forschungsgemeinschaft and Fonds der Chemischen Industrie.