Theoretical stability diagram of solvent-containing black lipid films

Recently, we have developed an analytical, semi-microscopic theory for the macroscopic behavior of a solvent-containing black lipid film subjected to an electric cross film voltage, . Here we employ the theoretical expressions derived for the disjoining pressure, _D, the film elasticity, _F, and the film tension, _F, to construct the stability diagram of the film, in the _D-. Depending on its state (_D, ), the film is stable or is prone to squeezing or bending deformations. For a monooleate film we show how the destruction of the plane film due to a periodic thickness fluctuation (squeezing) is facilitated by two mechanisms: i) lowering of _D at fixed ; ii) lowering of at fixed _D, provided that the film is in a stable state characterized by _D<–7.03×10³ dyne/cm² and >0 mV. Bending of a low tension film (single interface tension _s 0.025 dyne/cm¹) can be achieved only for >170 mV and _D > –8.7 × 10⁴ dyne/cm². Finally, we demonstrate the existence of a marginal state ( _D ⁰ , ⁰) where the film is predicted to exhibit strong fluctuations both in the squeezing and in the bending mode.     

Protocol-dependence of equivalent circuit parameters of toad urinary bladder

Summary Determinations of current-voltage relationships are widely employed in the characterization of epithelial sodium transport. In order to determine the protocol dependence of transport parameters in the toad urinary bladder, studies were carried out in the presence and absence of amiloride, an inhibitor of active sodium transport. With symmetric positive and negative perturbations of the transepithelial electrical potential difference (0±100 mV) for 30 sec, the amiloride-sensitive current-voltage (i ^a -) relationship was near linear over the range –75+100 mV, indicating constancy of the conductance ^a and the apparent electromotive force E _Na, lumped parameters of the standard electrical equivalent circuit model of the active transport system. With a reverse protocol (±1000 mV) or 15 min perturbations thei ^a - relationships were highly nonlinear. Nonlinearity reflected voltage dependence of parameters: perturbations that increased active transport decreased E _Na and increased ^a, as evaluated from 10 sec perturbations of ; slowing of active transport produced the converse changes. These effects are usefully analyzed in both quasi-steady states and true steady states by means of a detailed equivalent circuit incorporating the significant ionic currents across each plasma membrane. Precise understanding of the significance of ^a and E _Na will require characterization of the partial ionic conductances on perturbation of .     

Steroid synthesizing cellular sites in the ovary of the domestic pigeon Columba livia (Gmelin): a histochemical study.

Synopsis The ovary of the domestic pigeon,Columba livia, has been assayed histochemically for the localization of ⁵-3-hydroxysteroid dehydrogenase (⁵-3-HSDH), 17-hydroxysteroid dehydrogenase (17-HSDH), 11-hydroxysteroid dehydrogenase (11-HSDH), glucose-6-phosphate dehydrogenase (G6P-DH) and NADH-diaphorase activities during different periods of the reproductive cycle. ⁵-3-HSDH, 17-HSDH, 11-HSDH, G6P-DH and NADH-diaphorase activity was found in the theca interna of growing, atretic and postovulatory follicles, the granulosa of ovulatory, atretic and postovulatory follicles, and interstitial gland cells during the pre-incubation and the laying periods. During the incubation and squab feeding periods only ⁵-3-HSDH, G6P-DH and NADH-diaphorase activities were observed in the above mentioned cells. The steroidogenic potential of atretic follicles depends upon the type of atresia a follicle undergoes.     

Preparation of a series of sulfated tetrasaccharides from shark cartilage chondroitin sulfate D using testicular hyaluronidase and structure determination by 500 MHz1H NMR spectroscopy

Six tetrasaccharide fractions were isolated from shark cartilage chondroitin sulfate D by gel filtration chromatography followed by HPLC on an amine-bound silica column after exhaustive digestion with testicular hyaluronidase. Their structures were determined unambiguously by one- and two-dimensional 500 MHz¹H NMR spectroscopy in conjunction with HPLC analysis of chondroitinase AC-II digests of the tetrasaccharides. One fraction was found to contain two tetrasaccharide components. All the seven tetrasaccharides shared the common core structure GlcA1-3GalNAc1-4GlcA1-3GalNAc with various sulfation profiles. Four were disulfated comprising of two monosulfated disaccharide units GlcA1-3GalNAc(4-sulfate) and/or GlcA1-3GalNAc(6-sulfate), whereas the other three were hitherto unreported trisulfated tetrasaccharides containing a disulfated disaccharide unit GlcA(2-sulfate)1-3GalNAc(6-sulfate) and a monosulfated disaccharide unit GlcA1-3GalNAc(4-or 6-sulfate). These sulfated tetrasaccharides were demonstrated to serve as appropriate acceptor substrates for serum -N-acetylgalactosaminyltransferase, indicating their usefulness as authentic oligosaccharide substrates or probes for the glycobiology of sulfated glycosaminoglycans.Abbreviations NFU National formulary unit - COSY correlation spectroscopy - HOHAHA homonuclear Hartmann-Hahn - 1D or 2D one- or two-dimensional - IdoA l-iduronic acid - GlcA d-gluco-4-enepyranosyluronic acid - Di-0S GlcA1-3GalNAc - Di-4S GlcA1-3GalNAc(4-sulfate) - Di-4S GlcA1-3GalNAc(4-sulfate) - Di-6S GlcA1-3GalNAc(6-sulfate) - Di-6S GlcA1-3GalNAc(6-sulfate) - Di-diS _d GlcA(2-sulfate)1-3GalNAc(6-sulfate) - Di-diS_E GlcA1-3GalNAc(4, 6-disulfate) - U G, U, 2S, 4S, and 6S represent GlcA, GalNAc, GlcA, 2-O-sulfate, 4-O-sulfate, and 6-O-sulfate, respectively     

Deuterium isotope effects and fractionation factors of hydrogen-bonded A:T base pairs of DNA

Deuterium isotope effects and fractionation factors of N1...H3–N3 hydrogen bonded Watson–Crick A:T base pairs of two DNA dodecamers are presented here. Specifically, two-bond deuterium isotope effects on the chemical shifts of ¹³C2 and ¹³C4, ²¹³C2 and ²¹³C4, and equilibrium deuterium/protium fractionation factors of H3, , were measured and seen to correlate with the chemical shift of the corresponding imino proton, _H3. Downfield-shifted imino protons associated with larger values of ²¹³C2 and ²¹³C4 and smaller values, which together suggested that the effective H3–N3 vibrational potentials were more anharmonic in the stronger hydrogen bonds of these DNA molecules. We anticipate that ²¹³C2, ²¹³C4 and values can be useful gauges of hydrogen bond strength of A:T base pairs.     

The relation of proton motive force,adenylate energy charge and phosphorylation potential to the specific growth rate and efficiency of energy transduction inBacillus licheniformis under aerobic growth conditions

The magnitude of the proton motive force (p) and its constituents, the electrical () and chemical potential (-ZpH), were established for chemostat cultures of a protease-producing, relaxed (rel ^–) variant and a not protease-producing, stringent (rel ⁺) variant of an industrial strain ofBacillus licheniformis (respectively referred to as the A- and the B-type). For both types, an inverse relation of p with the specific growth rate was found. The calculated intracellular pH (pH_in) was not constant but inversely related to . This change in pH_in might be related to regulatory functions of metabolism but a regulatory role for pH_in itself could not be envisaged. Measurement of the adenylate energy charge (EC) showed a direct relation with for glucose-limited chemostat cultures; in nitrogen-limited chemostat cultures, the EC showed an approximately constant value at low and an increased value at higher . For both limitations, the ATP/ADP ratio was directly related to .The phosphorylation potential (G'p) was invariant with . From the values for G'p and p, a variable H⁺/ATP-stoichiometry was inferred: H⁺/ATP=1.83+0.52µ, so that at a given H⁺/O-ratio of four (4), the apparent P/O-ratio (inferred from regression analysis) showed a decline of 2.16 to 1.87 for =0 to _max (we discuss how more than half of this decline will be independent of any change in internal cell-volume). We propose that the constancy of G'p and the decrease in the efficiency of energy-conservation (P/O-value) with increasing are a way in which the cells try to cope with an apparent less than perfect coordination between anabolism and catabolism to keep up the highest possible with a minimum loss of growth-efficiency. Protease production in nitrogen-limited cultures as compared to glucose-limited cultures, and the difference between the A- and B-type, could not be explained by a different energy-status of the cells.Abbreviations CCCP carbonylcyanide-p-trichloromethoxyphenylhydrazone - DW dry weight of biomass - F Faraday's constant, 96.6 J/(mV × mol) - Fo chemostat outflow-rate (ml/h) - FCCP carbonylcyanide-p-trifluoromethoxyphenylhydrazone - G'p phosphorylation potential, the Gibbs energy change for ATP-synthesis from ADP and P_i - G'⁰p standard Gibbs energy change at specified conditions - H⁺/ATP number of protons translocated through - ATP synthase in synthesis of one ATP - H⁺/O protons translocated during transfer of 2 electrons from substrate to oxygen - specific growth rate (1/h) - _H+ transmembrane electrochemical proton potential, J/mol - M_b molar weight (147.6 g/mol) of bacteria with general cell formula C_6.0H_10.8O_3.0N_1.2 - pH_out,in extracellular, intracellular pH - P_i (intracellular) inorganic phosphate - p proton motive force, mV - pH transmembrane pH-difference - transmembrane electrical potential, mV - P/O number of ADP phosphorylated to ATP upon reduction of one O^2– to H₂O by two electrons transferred through the electron transfer chain - P/O (H⁺/O) × (H⁺/ATP)^–1 - P/O_F, P/O_N P/O with the two electrons donated by resp. (NADH + H⁺) and FADH - q specific rate of consumption or production (mol/g DW × h) - rel ⁺,rel ^– stringent, relaxed genotype - R universal gas constant, 8.36 J/(mol × degree) - T absolute temperature - TPMP⁺ triphenylmethylphosphonium ion - TPP⁺ tetraphenyl phosphonium ion - Y growth yield, g DW/mol - Z conversion constant=61.8 mV for 310 K (37 °C) - ZpH transmembrane proton potential or chemical potential, mV     

ATP-induced ΔpH formation in chloroplast ATP synthase proteoliposomes

Summary A procedure to reconstitute CF₀CF₁ proteoliposomes by gel filtration through a Sephadex-column pre-equilibrated with valinomycin and potassium is described. Proteoliposomes reconstituted by this procedure catalyze an ATP-induced pH of 2.5 to 3.5 units. pH was measured with either 9-aminoacridine or with the pH indicator pyranine trapped inside the proteoliposomes. CF₀CF₁ proteoliposomes prepared by conventional techniques catalyzed an ATP-induced formation, but were unable to catalyze an ATP-induced pH even in the presence of valinomycin.The ATP-induced pH was sensitive to uncouplers and energy transfer inhibitors and was increased at low temperatures. It is suggested that ATP-induced pH was observed in these proteoliposomes due to the efficient removal of intravesicular ammonium introduced with the CF₀CF₁ preparation. The ammonium acted as an internal buffer, and thus prevented an observable pH formation.     

Nutrients and Primary Production in the Estuary of the Razdol’naya River (Amur Bay,Sea of Japan)

The behavior of the basic nutrients (NO₃, PO₄, SiO₂) was studied in the estuary of the Razdolnaya River in low and high water, the flow was 4.3 × 10⁶ m³/day and 10.8 × 10⁶ m³/day, respectively. It was shown that within the limits of the euphotic zone the nutrients were characterized by a pronounced nonconservative behavior caused by their removal by phytoplankton in primary production. It was determined that phytoplankton removal of nutrients occurred with ratios C : NO₃ : P : Si = 105 : 18 : 1 : 37 and C : NO₃ : P : Si = 93 : 11 : 1 : 29 at a respective ratio P : NO₃ : Si = 1 : 22 : 140 in low water and P : NO₃ : Si = 1 : 17 : 120 in high water. It was also determined that the maximum rate of nutrient removal was 4 times higher in the high water than in the low water. The maximum value of primary production of phytoplankton was 2.5–4.0 gC/m² day. The estuary area of the Razdolnaya River was specified by rather high production. Such a rate of estuarine primary production, caused by nutrients carried out by the river, being no less than 250 t of dry weight of phytoplankton a day, can provide daily production up to 800 t of biomass in the secondary chain of the ecosystem.Original Russian Text Copyright © 2005 by Biologiya Morya, Zvalinsky, Nedashkovsky, Sagalayev, Tishchenko, Shvetsova.     

Energetic basis of cadmium toxicity in Staphylococcus aureus

In washed cells of cadmium-sensitive Staphylococcus aureus 17810S oxidizing glutamate, initial Cd²⁺⁺⁺ influx via the Mn²⁺ porter down membrane potential () was fast due to involvement of energy generated by two proton pumps—the respiratory chain and the ATP synthetase complex working in the hydrolytic direction. Such an unusual energy drain for rapid initial Cd²⁺ influx is suggested to be due to a series of toxic events elicited by Cd²⁺ accumulation down generated via the redox proton pump: (i) strong inhibition of glutamate oxidation accompanied by a decrease of electrochemical proton gradient ( _H ⁺) formation via the respiratory chain, (ii) automatic reversal of ATP synthetase from biosynthetic to hydrolytic mode, which was monitored by a decrease of _H ⁺-dependent ATP synthesis, (iii) acceleration of the initial Cd²⁺ influx down generated the reversed ATP synthetase, the alternative proton pump hydrolyzing endogenous ATP. The primary, cadmium-sensitive targets in strain 17810S seem to be dithiols located in the cytoplasmic glutamate oxidizing system, prior to the membrane-embedded NADH oxidation system. Inhibition by Cd²⁺ of _H ⁺-dependent ATP synthesis and of pH gradient (pH)-linked [¹⁴C]glutamate transport is a secondary effect due to cadmium-mediated inhibition of _H ⁺ generation at the cytoplasmic level. In washed cells of cadmium-resistant S. aureus 17810R oxidizing glutamate, Cd²⁺ accumulation was prevented due to activity of the plasmid-coded Cd²⁺ efflux system. Consequently, _H ⁺-producing and -requiring processes were not affected by Cd²⁺.     

Die optischen Übertragungseigenschaften der Komplexaugen von Drosophila

Summary The transfer properties of the optical system in the arthropod compound eye are determined by the interommatidial angle , influencing the resolving power, and by the width of the visual fields of single ommatidia , influencing the response at high spatial frequencies of brightness distributions in the object space. The energy transfer/ receptor is proportional to ( )² and decreases with in-inreasing approximation of the perfect-imaging condition: gD 0; 0. However, a value > 0 has to be maintained in order to overcome the threshold of nervous excitation at a certain minimum-brightness level. Theoretical treatment yields /=0.62 to 0.88 as the corresponding optimum-imaging relation. The actual ratio can be derived from measurements of the optomotor reactions to the movement of periodic brightness patterns. The approximate value 0.76 is obtained from the fruitfly Drosophila with normal and mutant eye pigmentation. As a result, the parameters of this imaging system are found to be established in a way that enables optimum performance at sufficient illumination. An dieser Stelle möchte ich Dr. W. Reichardt für sein eingehendes Interesse und manche anregende Diskussion über die Sehvorgänge im Komplexauge meinen Dank sagen. Dr. K. Kirschfeld verdanke ich ebenfalls wertvolle Hinweise. Herrn E. Freiberg bin ich für die Anfertigung der Abbildungen sehr verbunden.     

Comparative Study of Effects of Various Sterols and Triterpenoids on Permeability of Model Lipid Membranes

Using permeability to labeled glucose as a criterion of stability for liposomal membranes, a comparative study on stabilizing properties of different sterols and triterpenes in phospholipid bilayer has been carried out as well as on structural peculiarities of sterols responsible for membranolytic properties of cucumarioside G₁ from the cucumaria Eupentacta fraudatris. Stabilizing action of the studied sterols and triterpenoides incorporated in the bilayer decreases in the following order: cholesterol sulfate > cholesterol > ⁵-sterols > -sitosterol > ergosterols > ⁷-sterols > epicholesterol > pregnane > androstane > coprosterol > 14-methylcholest-9(11)-en-3-ol > 4, 14-dimethylcholest-9(11)-en-3-ol > holothurinogenin A₁ > glucoside of cholesterol > -xylosidase of ⁷-sterols > betulin > protopanaxatriol > phosphatidylcholine liposomes without sterol > protopanaxadiol > oleanolic acid. Sterol-dependent membranolytic cucumarioside G₁ practically loses its ability to increase permeability of phospholipid membranes containing sterols obtained from this holothuria as well as coprosterol, epicholestrol, sulfated and glycosylated forms of sterols. The obtained results confirm the sterol hypothesis of the mechanism of membranotropic action of holothuria glycosides and of resistance to them of holothuria cell membranes.     

Kinetics of Δψ-Dependent Sucrose Transport in Plasma Membrane Vesicles from Higher Plant Cells

The inside-out vesicles of plasma membranes were isolated from pumpkin stem cells, and the kinetics of sucrose efflux induced by the K⁺-diffusion potential (_D) was studied by measuring light transmission. Two phases differing in their rates and duration were identified in _D-dependent changes of light transmission. The increase in _Delevated the rate and magnitude of the fast phase in light transmission changes but did not markedly affect the rate of the slow phase. These two phases also differed in their sensitivity to inhibitors and to changes in sucrose concentration in the external medium. Measurements of _Dduring sucrose transport by means of the fluorescence probe dis-C₃-(5) revealed differences in the magnitude of _Dand its stability in vesicles loaded with sucrose and mannitol, as well as under the action of inhibitors. The two-phase dependence of sucrose efflux from vesicles on the applied diffusion potential is discussed in the context of modern concepts on the functioning of sucrose carriers in the membranes.     

The occurrence of the chloroplast pyrenoid is correlated with the activity of a CO2-concentrating mechanism and carbon isotope discrimination in lichens and bryophytes

The organic-matter carbon isotope discrimination () of lichens with a wide range of photobiont and/or cyanobiont associations was used to determine the presence or absence of a carbon-concentrating mechanism (CCM). Two groups were identified within the lichens with green algal photobionts. One group was characterised by low, more C₄-like values ( < 15), the other by higher, more C₃-like values ( > 18). Tri-partite lichens (lichens with a green alga as the primary photobiont and cyanobacteria within internal or external cephalodia) occurred in both groups. All lichens with cyanobacterial photobionts had low values ( < 15). The activity of the CCM, organic-matter values, on-line values and gas-exchange characteristics correlated with the presence of a pyrenoid in the algal chloroplast. Consistent with previous findings, lichens with Trebouxia as the primary photobiont possessed an active CCM while those containing Coccomyxa did not. Organic values for lichens with Stichococcus as the photobiont varied between 11 and 28. The lichen genera Endocarpon and Dermatocarpon (Stichococcus + pyrenoid) had C₄-like organic values ( = 11 to 16.5) whereas the genus Chaenotheca (Stichococcus — pyrenoid) was characterised by high C₃-like values ( = 22 to 28), unless it associated with Trebouxia ( = 16). Gas-exchange measurements demonstrated that Dermatocarpon had an affinity for CO₂ comparable to those species which possessed the CCM, with K_0.5 = 200–215 1 · 1^–1, compensation point () = 45–48 l · l^–1, compared with K_0.5 = 195 1 · 1^–1, = 441 · 1^–1 for Trebouxioid lichens. Furthermore, lichens with Stichococcus as their photobiont released a small pool (24.2 ± 1.9 to 34.2 ± 2.5 nmol · mg^–1 Chl) of inorganic carbon similar to that released by Trebouxioid lichens [CCM present, dissolved inorganic carbon (DIC) pool size = 51.0 ± 2.8 nmol · mg^–1 Chl]. Lichens with Trentepohlia as photobiont did not possess an active CCM, with high C₃-like organic values ( = 18 to 23). In particular, Roccella phycopsis had very high on-line values ( = 30 to 33), a low affinity for CO₂ (K_0.5 = 400 1 · 1^–1, = 120 1 · ^–1) and a negligible DIC pool. These responses were comparable to those from lichens with Coccomyxa as the primary photobiont with Nostoc in cephalodia (organic = 17 to 25, on-line = 16 to 21, k_0.5 = 388 1 · 1^–1, = 85 1 · 1^–1, DIC pool size = 8.5 ± 2.4 nmol · mg^–1 Chl). The relative importance of refixation of respiratory CO₂ and variations in source isotope signature were considered to account for any variation between on-line and organic . Organic was also measured for species of Anthocerotae and Hepaticae which contain pyrenoids and/or Nostoc enclosed within the thallus. The results of this screening showed that the pyrenoid is correlated with low, more C₄-like organic values ( = 7 to 12 for members of the Anthocerotae with a pyrenoid compared with = 17 to 28 for the Hepaticae with and without Nostoc in vesicles) and confirms that the pyrenoid plays a fundamental role in the functioning of the CCM in microalgal photobionts and some bryophytes.Abbreviations and Symbols CCM carbon-concentrating mechanism - DIC dissolved inorganic carbon (CO₂ + HCO ₃ ^- + CO ₃ ^2- ) - DW dry weight - K_0.5 external concentration of CO₂ at which half-maximal rates of CO₂ assimilation are reached - photobiont photosynthetic organism present in the lichen - Rubisco ribulose-1,5-bisphosphate carboxylase-oxygenase - carbon isotope discrimination (%) - ¹³C carbon isotope ratio (%) This research was funded by Natural Environment Research Council grant no. GR3/8313. The authors would also like to thank Dr. B. Coppins, Royal Botanic Gardens Edinburgh and Prof. A. Roy Perry, National Museum of Wales, for access to herbarium collections, Dr. T. Booth for confocal microscopy work and Dr. A.J. Richards, University of Newcastle upon Tyne and Dr. O.L. Gilbert, University of Sheffield for identifying bryophytes and lichens respectively. E.S. would particularly like to thank Dr. M. Broadmeadow, The Forestry Authority, Farnham, Surrey, and Cristina Máguas, Universidade de Lisboa, for their advice and expertise at the beginning of the project.     

Sodium ions are necessary for growth and energy transduction in the marine cyanobacterium Oscillatoria brevis

The maximal growth rate of the marine cyanobacterium Oscillatoria brevis was reached at 200–400 mM NaCl and pH 9.0–9.6. NaCl was found (i) to stimulate the rate of the light-supported generation across the cytoplasmic membrane of the cells and (ii) to decrease the sensitivity of level and motility of the O. brevis trichomes to protonophorous uncouplers. The Na⁺/H⁺ antiporter, monensin, increased both and the uncoupler sensitivity of the cells. The data obtained agree with the assumption that O. brevis possesses a primary Na⁺ pump in its cytoplasmic membrane.Abbreviations ATP adenosine-5-triphosphate - TTFB tetrachlortrifluoromethylimidazol - CCCP carbonyl cyanide m-chlorophenylhydrazone - Na⁺ transmembrane electrochemical potential differences of Na⁺ - transmembrane electric potential difference - pNa transmembrane pNa difference     

Effects of competition and N and P supply on carbon isotope discrimination and <Superscript>15</Superscript>N-natural abundance in four grassland species

The effect of interspecific competition and element additions (N and P) on four grassland species (Poa pratensis, Lolium perenne, Festuca valida, Taraxacum officinale) grown under field conditions was studied. Two grasses (L. perenne, F. valida) grown in monoculture (absence of competition) showed lower carbon isotope discrimination (¹³C) and enriched ¹⁵N values. Nitrogen addition (as urea) had inconsistent effects on species ¹³C while caused enrichment of ¹⁵N of P. pratensis and F. valida but strong depletion of ¹⁵N of T. officinale. Phosphorous had no significant effect on ¹³C but depleted ¹⁵N of all species.     

Steady state changes in mitochondrial electrical potential and proton gradient in perfused liver from rats fed a high fat diet

In this work the protonmotive force (p), as well as the subcellular distribution of malate, ATP, and ADP were determined in perfused liver from rats fed a low fat or high fat diet, using density gradient fractionation in non acqueous solvents.Rats fed a high fat diet, despite an enhanced hepatic oxygen consumption, exhibit similar p to that found in rats fed a low fat diet, but when we consider the two components of p, we find a significant decrease in mitochondrial/cytosolic pH difference (pH_m) and a significant increase in mitochondrial membrane potential (_m) in rats fed a high fat diet compared to rats fed a low fat diet, which tend to compensate each other. In rats fed a high fat diet the concentration ratio of malate and ATP/ADP does not reflect the changes in pH_m and _m, which represent the respective driving force for their transport.The findings are in line with an increase in substrate supply to the respiratory chain which is, however, accompanied by a higher energy turnover in livers from HFD rats. By this way the liver could contribute to the lack of weight gain from the high caloric intake in HFD rats.     

Anaerobic biosynthesis of unsaturated fatty acids in the cyanobacterium,Oscillatoria limnetica

The mechanism for synthesis of monounsaturated fatty acids under aerobic and anaerobic conditions was studied in the facultative anaerobic cyanobacterium, Oscillatoria limnetica. The hexadecenoic acid (C161) of aerobically grown O. limnetica was shown to contain both the 7 (79%) and 9 (21%) isomers, while the octadecenoic (C181) acid was entirely the 9 acid. Incorporation of [2-¹⁴C] acetate into the fatty acids under aerobic conditions resulted in synthesis of the 7 and 9 C161 and the 9 C181. Synthesis of unsaturated fatty acids in the presence of DCMU required sulfide. Anaerobic incubations in the presence of DCMU and sulfide (less than 0.003% atmospheric oxygen) resulted in a two-fold increase in monounsaturated fatty acids of both 7 and 9 C161 and 9 and 11 C181. The synthesis of these isomers is characteristic of a bacterialtype, anaerobic pathway.Abbreviations DCMU 3(3,4-dichlorophenyl)-1,1-dimethylurea - MFA monounsaturated fatty acid     

A dominant mutation for high oleic acid content in sunflower (Helianthus annuus L.) seed oil is genetically linked to a single oleate-desaturase RFLP locus

Pervenets is a sunflower mutant with a seed oil oleic acid content greater than 65%. It was obtained after mutagenesis treatment on VNIIMK 8931. Several commercial varieties derived from Pervenets and breeding materials with a high oleic acid content have been marketed. However, the genetics of this trait are still not fully understood by breeders. To characterize the Pervenets mutation, we studied RFLP in relation to high oleic acid content. We performed diversity analyses on 239 genotypes with cDNA sequences coding for 9- and 12-desaturases as probes. The 12 RFLPs enabled us to identify at least two independent loci. One 12 RFLP allele (12HOS) was strictly correlated to high oleic acid content, whereas no correlation was found between 9-desaturase polymorphism and high oleic acid content. These results enabled to us estimate the genetic distance between the marker and the Pervenets mutation loci. An F₂ segregating population of 107 plants confirmed the correlation between high oleic acid content and 12HOS, indicating tight genetic linkage. The nature of the Pervenets dominant mutation and the complexity of the high oleic acid content trait are discussed.     

The ability of acidic pH,growth inhibitors,and glucose to increase the proton motive force and energy spilling of amino acid-fermenting <Emphasis Type="Italic">Clostridium sporogenes</Emphasis> MD1 cultures

Clostridium sporogenes MD1 grew rapidly with peptides and amino acids as an energy source at pH 6.7. However, the proton motive force (p) was only –25 mV, and protonophores did not inhibit growth. When extracellular pH was decreased with HCl, the chemical gradient of protons (ZpH) and the electrical membrane potential () increased. The p was –125 mV at pH 4.7, even though growth was not observed. At pH 6.7, glucose addition did not cause an increase in growth rate, but increased to –70 mV. Protein synthesis inhibitors also significantly increased . Non-growing, arginine-energized cells had a of –80 mV at pH 6.7 or pH 4.7, but was not detected if the F₁F₀ ATPase was inhibited. Arginine-energized cells initiated growth if other amino acids were added at pH 6.7, and and ATP declined. At pH 4.7, ATP production remained high. However, growth could not be initiated, and neither nor the intracellular ATP concentration declined. Based on these results, it appears that C. sporogenes MD1 does not need a large p to grow, and p appears to serve as a mechanism of ATP dissipation or energy spilling.Mandatory disclaimer: Proprietary or brand names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product, and exclusion of others that may be suitable.     

Regulation of proline catabolism in Pseudomonas aeruginosa PAO

Mutants of Pseudomonas aeruginosa deficient in the utilization of l-proline as the only carbon and nitrogen source have been found to be defective either in proline dehydrogenase activity or in both proline dehydrogenase and ¹-pyrroline-5-carboxylate dehydrogenase activities of the bifunctional proline degradative enzyme. The latter type of mutants was unable to utilize l-ornithine, indicating that a single ¹-pyrroline-5-carboxylate dehydrogenase activity is involved in the degradation of ornithine and proline. Proline dehydrogenase and ¹-pyrroline-5-carboxylate dehydrogenase activities were strongly and coordinately induced by proline. It was excluded that ¹-pyrroline-5-carboxylate acted as an inducer of the bifunctional enzyme and it was shown that the low level induction observed during growth on ornithine was due to the intracellular formation of proline. The formation of the proline degradative enzyme was shown to be subject to catabolite repression by citrate and nitrogen control.Abbreviations EMS Ethylmethane sulfonate - NG N-methyl-N-nitro-N-nitrosoguanidine - P Minimal medium P - Pro-DH Proline dehydro-genase - P5C ¹-Pyrroline-5-carboxylate - P5C-DH ¹-Pyrroline-5-carboxylate dehydrogenase