Tissue culture ofKarwinskia humboldtiana—a plant producing toxins with antitumoural effects

Isolated embryos ofKarwinskia humboldtiana were cultured in vitro. The growth of embryos and development to plantlets on woody plant medium supplemented with indole-3-acetic acid 6.10^-2 mol l^–1, gibberellic acid (GA₃) 3.10^-2 mol l^–1, and 6-benzylaminopurine (BA) 2 mol l^–1 was obtained. Multiplication of shoots and rooting of excised shoots has been achieved. Callus formation on modified Murashige-Skoog medium supplemented with 1-naphthaleneacetic acid 10 mol l^–1, GA₃ 14 mol l^–1, and kinetin 5 mol l^–1 on hypocotyls, or on root cultures on medium supplemented with 2.4-dichlorophenoxyacetic acid 10 mol l^–1 and BA 10 mol l^–1 was induced.Abbreviations BA 6-benzylaminopurine - 2,4-d 2,4-dichlorophenoxyacetic acid - GA₃ gibberellic acid - IAA indole-3-acetic acid - NAA 1-naphthaleneacetic acid - TEM transmission electron microscopy     

Active hexose uptake in Lemna gibba G1

Growth of autotrophically growing duck-weeds (Lemna gibba L., G1) was stimulated by sucrose. The rate of respiration increased when plants had been grown on sucrose (8.7 mol O₂ g^-1 fresh weight (FW) h^-1) and was reduced after growth without sucrose in the dark or under longday conditions (2.5 mol O₂ g^-1 FW h^-1). Photosynthesis was induced already by low light intensities (0.1 klx).Short-time application of glucose or sucrose stimulated respiration in proportion to the hexose uptake rate. Sucrose is probably not taken up as the disaccharide. The transported sugar species after addition of sucrose are its hexose moieties produced by the high activity of the cell wall invertase. Fructose stimulated to a lesser extent; mannitol induced no enhancement; 2-deoxyglucose slightly inhibited O₂ uptake. After mild carbon starvation of the plants the uptake of glucose and 3-O-methylglucose proceeded without any lag phase, with similar saturation kinetics in both cases. The initial uptake rate at substrate saturation was 2.6 mol glucose g^-1 FW h^-1 in the dark. Light stimulated hexose uptake by 2 to 3 times. The results show that Lemna gibba has an energy-dependent constitutive system for hexose uptake.Abbreviation FW fresh weight - LD long day - SD short day     

Mixed-acid fermentation and polysaccharide production by Lactobacillus helveticus in milk cultures

Lactobacillus helveticus grown in milk with pH control at 6.2 had a slower growth rate (=0.27 h^–1) and produced less exopolysaccharide (49 mg l^–1) but increased lactic acid production (425 mM) compared to cultures without pH control (=0.5 h^–1, 380 mg exopolysaccharide l^–1, and 210 mM lactate), respectively. Both cultures displayed a mixed-acid fermentation with formation of acetate, which is linked not only to citrate metabolism, but also to alternative pathways from pyruvate.     

Effect of dilution rate on the release of pertussis toxin and lipopolysaccharide ofBordetella pertussis

Summary The kinetics ofBordetella pertussis growth was studied in a glutamate-limited continuous culture. Growth kinetics corresponded to Monod's model. The saturation constant and maximum specific growth rate were estimated as well as the energetic parameters, theoretical yield of cells and maintenance coefficient. Release of pertussis toxin (PT) and lipopolysaccharide (LPS) were growth-associated. In addition, they showed a linear relationship between them. Growth rate affected neither outer membrane proteins nor the cell-bound LPS pattern.Nomenclature X cell concentration (g L^–1) - specific growth rate (h^–1) - _m maximum specific growth rate (h^–1) - D dilution rate (h^–1) - S concentration of growth rate-limiting nutrient (glutamate) (mmol L^–1 or g L^–1) - Ks substrate saturation constant (mol L^–1) - m_s maintenance coefficient (g g^–1 h^–1) - Y_x/s theoretical yield of cells from glutamate (g g^–1) - Y_x/s yield of cells from glutamate (g g^–1) - Y_PT/s yield of soluble PT from glutamate (mg g^–1) - Y_KDO/s yield of cell-free KDO from glutamate (g g^–1) - Y_PT/x specific yield of soluble PT (mg g^–1) - Y_KDO/x specific yield of cell-free KDO (g g^–1) - q_PT specific soluble PT production rate (mg g^–1 h^–1) - q_KDO specific cell-free KDO production rate (g g^–1 h^–1)     

Photoautotrophic growth of Marchantia polymorpha L. cells in suspension culture

A cell line of M. polymorpha was grown photoautotrophically in liquid suspension culture using 1% CO₂ in air as sole carbon source. The growth rate in terms of cell dry-weight during the exponential phase was 0.171 and the doubling time was 1.76 d. The rate of increase in chlorophyll was 1.6 times higher than the growth rate. The highest content of chlorophyll was 24 mg g^-1 dry weight, and the photosynthetic activity of the cells in the exponential phase, as calculated from the growth rate, was at least 60 mol mg^-1 chlorophyll h^-1.     

Accumulation of silver by growing and non-growing populations of Citrobacter intermedius B6

Summary Accumulation of silver is reported for growing and non-growing populations of Citrobacter intermedius B6. In non-growing cultures a maximum uptake of 4.35% (w/w) was observed at an initial silver concentration of 2111.2 mol Ag⁺ l^-1. In contrast the maximum uptake of silver by growing bacteria was 2.81% (w/w) at an effective concentration of silver of 217.8 mol·l^-1. Silver accumulation rates in both resting (460 mol Ag⁺ g^-1 per hour) and continuously grown (41 mol Ag⁺ g^-1 per hour) bacteria are higher than previously reported. Cell fractionation and electron microscopy of continuously grown bacteria indicated that accumulation of silver was associated with the cell envelope, in the form of dense deposits of macromolecular proportions. This observation discounts simple surface adsorption as the process of accumulation in growing cultures.     

Degradation of polyaromatic hydrocarbons by Burkholderia cepacia 2A-12

A new strain of bacterium degrading polyaromatic hydrocarbons (PAHs), Burkholderia cepacia 2A-12, was isolated from oil-contaminated soil. Of three PAHs, the isolated strain could utilize naphthalene (Nap) and phenanthrene (Phe) as a sole carbon source but not pyrene (Pyr). However, the strain could degrade Pyr when a cosubstrate such as yeast extract (YE) was supplemented. The PAH degradation rate of the strain was enhanced by the addition of other organic materials such as YE, peptone, glucose, and sucrose. YE was a particularly effective additive in stimulating cell growth as well as PAH degradation. When 1 g YE l^–1, an optimum concentration, was supplemented into the basal salt medium (BSM) with 215 mg Phe l^–1, the specific growth rate (0.30 h^–1) and Phe-degrading rate (29.6 mol l^–1 h^–1) were enhanced approximately ten and three times more than those obtained in the BSM with 215 mg Phe l^–1, respectively. Both cell growth and PAH degradation rates were increased with increasing Phe and Pyr concentrations, and B. cepacia 2A-12 had a tolerance against Phe and Pyr toxicity at the high concentration of 730–760 mg l^–1. Through kinetic analysis, the maximum specific growth rate ( _max) and PAH degrading rate ( _max) for Phe were obtained as 0.39 h^–1 and 300 mol l^–1 h^–1, respectively. Also, _max and _max for Pyr were 0.27 h^–1 and 52 mol l^–1 h^–1, respectively. B. cepacia 2A-12 could simultaneously degrade crude oil as well as PAHs, indicating that this bacterium is very useful for the removal of oils and PAHs contaminants.     

Species-specific N and P release rates in Daphnia

Bioavailable N and P release rates by juveniles and adults of three Daphnia taxa (D. hyalina, D. galeata and its interspecific hybrids D. hyalina × galeata) were measured to assess the effect of weight and interspecific differences on these rates in Daphnia. Immobilized Scenedesmus obliquus cells were used to estimate the release rates. The specific release rate of N varied between 5.19–5.71 g N mg C^-1 h^-1 for juveniles and 3.00–3.42 g N mg C^-1 h^-1 for adults. P excretion rate ranged between 1.93–2.37 g P mg C^-1 h^-1 for juveniles and 1.00–1.24 g P mg C^-1 h^-1 for adults. Our results show that the taxonomic affiliation of Daphnia individuals did not affect their N and P release rates.     

Effect of washing on the plasma membrane and on stress reactions of cultured rose cells

The effects of plant growth regulators, light intensity, and end-of-day (EOD) light quality treatments on node and microtuber induction (% of cultures with microtubers) and development (fresh weight of microtubers) in yam (Dioscorea alata L. cv. Oriental) cultures were investigated. Nodal segments were excised from plantlets cultured on tuberization medium containing growth regulators and exposed to various light treatments. Absciscic acid (1 M) stimulated and cytokinins (2.5 M) inhibited microtuber development from yam nodal segments cultured on Mantell's and Hugo's full-strength tuberization medium under 8-h photoperiods. EOD far-red (FR) light inhibited microtuber induction and development and enhanced node formation. EOD FR light effects were nullified by immediately following the FR treatment with red light. This suggested the involvement of phytochrome in these processes. The lowest light intensity evaluated (12 mol m^–2 s^–1) inhibited microtuber, root and shoot production as compared to light intensities of 42, 72 and 102 mol m^–2 s^–1. Kinetin (2.5 m) in half-strength tuberization medium inhibited microtuber induction and development but did not affect node production in the light intensity evaluation.Abbreviations ABA abscisic acid - BA 6-benzylaminopurine - 2iP 6-(c,c-dimethylallylamino)-purine - NAA napthaleneacetic acid - R light red light - FR light far-red light - EOD light end-of-day light     

Induction of phytoalexin formation in crown gall and hairy root culture of Salvia miltiorrhiza by methyl viologen

Methyl viologen (MV) (20–150 M), a generator of superoxide anion (O₂ ^–), but not hydrogen peroxide (H₂O₂) (10 M–2 mM) triggered the formation of cryptotanshinone (a phytoalexin) in cultures of both crown galls and hairy roots of Salvia miltiorrhiza. MV also inhibited the biomass formation and decreased the contents of phenolic acids in both cultures whereas H₂O₂ did not. In addition, MV and yeast elicitor induced cryptotanshinone formation synergistically only in crown gall cultures. Treatment of the cultures with 3.3 M diphenylene iodonium, an inhibitor of NAD(P)H oxidase, did not exhibit any detrimental effect on the yeast elicitor-induced cryptotanshinone formation in hairy root cultures whereas 1 M diphenylene iodonium was inhibitory on yeast elicitor-induced cryptotanshinone formation in crown gall cultures.     

Phosphate-limited growth of Chromatium vinosum in continuous culture

Chromatium vinosum DSM 185 was grown in continuous culture at a constant dilution rate of 0.071 h^-1 with sulfide as the only electron donor. The organism was subjected to conditions ranging from phosphate limitation (S _R-phosphate=2.7 M and S _R-sulfide=1.8 mM) to sulfide limitation (S _R-phosphate=86 M and S _R-sulfide=1.8 mM). At values of S _R-phosphate below 7.5 M the culture was washed out, whereas S _R-phosphate above this value resulted in steady states. The saturation constant (K ) for growth on phosphate was estimated to be between 2.6 and 4.1 M. The specific phosphorus content of the cells increased from 0.30 to 0.85 mol P mg^-1 protein with increasing S _R-phosphate. The specific rate of phosphate uptake increased with increasing S _R-phosphate, and displayed a non-hyperbolic saturation relationship with respect to the concentration of phosphate in the inflowing medium. Approximation of a hyperbolic saturation function yielded a maximum uptake rate (V _max) of 85 nmol P mg^-1 protein h^-1, and a saturation constant for uptake (K _t) of 0.7 M. When phosphate was supplied in excess 8.5% of the phosphate taken up by the cells was excreted as organic phosphorus at a specific rate of 8 nmol P mg^-1 protein h^-1.Non-standard abbreviations BChla bacteriochlorophyll a - D dilution rate; _max, maximum specific growth rate - maximum specific growth rate if the substrate were not inhibitory - K saturation constant for growth on phosphate - V _max maximum rate of phosphate uptake - K _i saturation constant for phosphate uptake - K _i inhibition constant for growth in the presence of sulfide - S _R concentration of substrate in the inflowing medium     

Induction characteristics of reductive dehalogenation in the ortho-halophenol-respiring bacterium,Anaeromyxobacter dehalogenans

Anaeromyxobacter dehalogenans strain 2CP-C dehalogenatesortho-substituted di- and mono-halogenated phenols and couples this activity to growth. Reductive dehalogenation activity has been reported to be inducible, however,this process has not been studied extensively. In this study, theinduction of reductive dehalogenation activity by strain 2CP-C is characterized. Constitutive 2-chlorophenoldechlorination activity occurs in non-induced fumarate-grown cells, with rates averaging 0.138 mol of Cl^- h^-1 mg of protein^-1. Once induced, these cultures dechlorinate 2-chlorophenol (2-CP) at rates as high as 116 mol of Cl^-1 h^-1 mg of protein^-1. Dechlorination of 2-CP is induced by phenol,2-chlorophenol, 2,4-dichlorophenol, 2,5-dichlorophenol, 2,6-dichlorophenol,and 2-bromophenol. Of the substrates tested, 2-bromophenol shows the highestinduction potential, yielding double the 2-chlorophenol dechlorination rate when compared to other inducing substrates. No induced dechlorination is observed at concentrations less than5 M 2-CP. When fumarate cultures were diluted 100-fold, fumarate reduction rates were reduced roughly according to the dilution factor, while dechlorination rates were similar in fumarate grown cells amended with 2-CP and cells diluted 100-fold prior to the addition of chlorophenol. This indicates that the majority of the fumarate-grown cells in late log phase were not induced when exposed to inducing substrates such as 2-CP. This observation may have ramifications on the success of bioaugmentation using halorespiring bacteria, which traditionally relies on growing culturesusing more readily utilized substrates. The rapid dechlorination rate and unique induction pattern also make strain 2CP-C a promising model organism for understanding the regulationof reductive dehalogenation at the enzymatic level.     

Adventitious shoot regeneration from in vitro-cultured leaves of Rubus genotypes

Regeneration of adventitious shoots from leaves of several in vitro-cultured Rubus genotypes was affected by media components and incubation conditions. Leaves cultured at 20°C with a photosynthetic photon flux (PPF) of 40 mol m^-2 s^-1 had a higher regeneration frequency and more shoots per regenerating leaf than ones cultured at 25°C with a PPF of either 40 or 80 mol m^-2 s^-1. Thidiazuron (TDZ) was significantly more effective than benzyladenine. Medium containing 1 M TDZ had the highest percentage regeneration for leaves of Autumn Bliss, Canby, Summit and Sentry red raspberries, whereas leaves of MD-ETCE-1 blackberry hybrid responded more to 10 M TDZ. Higher regeneration frequencies were obtained with 0.5 M indolebutyric acid (IBA) than with 1 M, but no significant difference was observed between 0.5 M and no IBA in other experiments. More shoots per regenerating leaf formed on Murashige and Skoog (MS) and N6 media, than on half-strength MS, Anderson, or Woody Plant media for all genotypes tested. The youngest two expanding leaves near the shoot apex were the most regenerative and yielded the highest number of shoots per regenerating leaf.Abbreviations AND Anderson (1980) - BA benzyladenine - IBA indolebutyric acid - MS Murashige & Skoog (1962) - N6 Chu et al. (1975) - NAA naphthaleneacetic acid - PPF photosynthetic photon flux - TDZ thidiazuron (N-phenyl-N'-1, 2, 3-thiadiazol-5-ylurea) - WPM Woody Plant Medium [Lloyd & McCown (1980)]     

The effect of carbon dioxide on the growth kinetics of fructose-limited chemostat cultures of Acetobacterium woodii DSM 1030

The growth of the anaerobic acetogenic bacterium Acetobacterium woodii DSM 1030 was investigated in fructose-limited chemostat cultures. A defined medium was developed which contained fructose, mineral salts, cysteine · HCl and Ca pantothenate (1 mg · 1^–1) supplied in a vitamin supplement. Growth at high dilution rates was dependent on the presence of CO₂ in the gas phase. The ^max was found to be 0.16 h^–1 and the fructose maintenance requirement was 0.1 to 0.13 mmol fructose · (g dry wt)^–1 · h^–1. A growth yield of 61 g dry wt · (mol fructose)^–1, corrected for the cell maintenance requirement and for incorporation of fructose carbon into cell biomass, was determined from the fructose consumption. A corresponding growth yield of 69 g dry wt · (mol fructose)^–1 was calculated from the acetate production assuming that fructose fermentation was homoacetogenic. A Y_ATP of 12.2 to 13.8 g dry wt · (mol ATP)^–1 was calculated from these growth yields using a value of 5 mol ATP · (mol fructose)^–1 as an estimate of the amount of ATP synthesised from fructose fermentation. The addition of yeast extract (0.5 g · 1^–1) to the medium did not influence the ^max or cell yield. After prolonged growth under fructose-limited conditions the requirement of the culture for CO₂ in the gas phase was reduced.Abbreviations YE yeast extract - IC inorganic carbon - D fermenter dilution rate : h^–1 - M_X maintenance requirement for X: mmol X · (g dry wt)^–1 · h^–1 - X may be fructose (Fruct), fructose consumed in energy metabolism (Fruct [E]), acetate (Ac) - ATP CO₂, NH _inf4 ^sup+ or Pi - qX specific rate of utilisation or consumption of X: mmol X · (g dry wt)^–1 · h^–1 - V fermenter volume: litre - rC · Cell, fermenter cell carbon production: mmol C · h^–1 - Y_X yield of cells on X: g dry wt · (mol X)^–1 - Y _infx ^supmax the yield corrected for cell maintenance: g dry wt · (mol X)^–1 - S_ATP stoichiometry of ATP synthesis from fructose: mol ATP · (mol frucose)^–1 - x cell concentration: g dry wt · 1^–1 - specific growth rate : h^–1 - ^max maximum specific growth rate: h^–1     

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     

Quantification of multiple-substrate controlled growth-simultaneous ammonium and glucose limitation in chemostat cultures of Klebsiella pneumoniae

In chemostat cultures of Klebsiella pneumoniae (K. aerogenes) NCTC 418 we measured the concentrations of glucose and ammonium and we varied the ratio of the (limiting) concentrations of glucose and ammonium in the feed medium. By doing this at different dilution rates we found a range where growth rate varies with either concentration in the culture when the other concentration in the culture is held constant. This proves that within this range, dual-substrate controlled growth occurs. Dual substrate-controlled growth was accompanied by yield coefficients for glucose and for ammonium that were intermediate between the yield coefficients obtained for single glucose or single ammonium limitation. We quantified the control by either substrate in terms of the flux control coefficient with respect to that substrate, where flux refers to growth rate. Dualsubstrate controlled growth is reflected by the finding that both flux control coefficients exceed zero, simultaneously. In the transition of glucose to ammonium limitation, the control gradually shifts from glucose to ammonium.Abbreviations Symbol Units Meaning s Steady-state concentration of substrate in the culture - S_r M Concentration of substrate in reservoir medium - Y gDWmol^-1 Yield - D h^-1 Dilution rate - h^–1 Specific growth rate - _max h^–1 Maximal growth rate - C ₂ Control coefficient, of s on - J h^-1 Rate or flux - J_ATP mmolgDW^-1h^-1 ATP synthesis rate - a Anabolism - c Catabolism - l Leak     

The spermatozoon of Oikopleura dioica Fol (Larvacea,Tunicata)

Summary The spermatozoon of Oikopleura dioica is about 30 m long, with a spherical head, about 1 m wide, a 3 m long and 1 m wide midpiece, and a 25 m long tail with a tapered end piece. The head contains a nucleus with the chromatin volume limited to about 0.1 m³. A small acrosome is found in an anterior inpocketing, and a flagellar basal body in a posterior inpocketing of the nucleus. The midpiece contains a single mitochondrion with the flagellar axoneme embedded in a groove along its medial surface. The flagellar axoneme has the typical 9 + 2 substructure, and the basal body the typical 9+0 substructure. A second centriole and special anchoring fibres are absent.     

Metabolism of Acetivibrio cellulolyticus during optimized growth on glucose,cellobiose and cellulose

Summary The growth of Acetivibrio cellulolyticus in 2.5 l batch cultures was optimized by controlling the growth pH at 6.7, the dissolved inorganic sulphide concentration at 0.4–0.6 mM, and by constant removal of hydrogen from the cultures by sparging with N₂/CO₂ or N₂ gas. An initial ethanol concentration of 0.15% (w/v) in cellobiose media resulted in specific growth rates which were reduced by about 75% compared to growth rates of 0.17 h^–1 in control cultures. Acetivibrio cellulolyticus had to be adapted for growth on glucose and ¹⁴C-radiotracer studies indicated that glucose was metabolized by the Embden-Meyerhof pathway. The specific growth rate (=0.03h^–1) and molar growth yield (Y_glucose=21.5) were considerably lower than those obtained (=0.17 h^–1, Y_cellobiose=68.9) in cellobiose media. A Y_ATP of 12.8 was obtained during growth on cellobiose. The mol product formed per mol Avicel cellulose fermented (on anhydroglucose equivalent basis) were 3.70 H₂, 2.64 CO₂, 0.73 acetate, 0.39 ethanol and 0.03 total soluble sugars on glucose basis. Maximum cellulase activity was observed in cellulose-grown cultures.National Research council of Canada No. 20826     

Transient state characteristics of adaptation to changes in light conditions for the cyanobacterium Oscillatoria agardhii

Transitions in growth irradiance level from 92 to 7 Em^-2 s^-1 and vice versa caused changes in the pigment contents and photosynthesis of Oscillatoria agardhii. The changes in chlorophyll a and C-phycocyanin contents during the transition from high to low irradiance (HL) were reflected in photosynthetic parameters. In the LH transition light utilization efficiencies of the cells changed faster than pigment contents. This appeared to be related to the lowering of light utilization efficiencies of photosynthesis. As a possible explanation it was hypothesized that excess photosynthate production led to feed back inhibition of photosynthesis. Time-scales of changes in the maximal rate of O₂ evolution were discussed as changes in the number of reaction centers of photosystem II in relation to photosynthetic electron transport. Parameters that were subject to change during irradiance transitions obeyed first order kinetics, but hysteresis occurred when comparing HL with LH transients. Interpretation of first order kinetic analysis was discussed in terms of adaptive response vs changes in growth rate.Non-standard abbreviations Chla chlorophyll a - CPC C-phycocyanin - PS II photosystem II - PS I photosystem I - RC II reaction center of photosystem II - P photosynthetic O₂-evolution - I irradiance, Em^-2 s^-1 - light utilization efficiency of cells, mmol O₂·mg dry wt^-1·h^-1/Em^-2 s^-1 - light utilization efficiency of photosynthetic apparatus, mol O₂·mol Chla ^-1·h^-1/Em^-2 s^-1 - P_max maximal rate of O₂ evolution by cells, mol O₂·mg dry wt^-1·h^-1 - P_max maximal rate of O₂ evolution by photosynthetic apparatus, mol O₂·mol·Chla ^-1·h^-1 - LL low light, E m^-2 s^-1 - HL high light, E m^-2 s^-1 - LH low to high light transition - HL high to low light transition - k specific rate of adaptation, h^-1 - specific growth rate, h^-1 - Q pool size of cell constituent, mol·mg dry wt^-1 - q net synthesis rate of cell constituent, mol·mg dry wt^-1·h^-1     

The bactericidal effects of Lactobacillus acidophilus,garcinol and Protykin® compared to clarithromycin,on Helicobacter pylori

Chronic infection with Helicobacter pylori causes peptic ulcers, gastric cancer and lymphoma. We evaluated the inhibitory effects of the probiotic Lactobacillus acidophilus DDS-1J, the antibiotic clarithromycin and the natural antioxidants garcinol and Protykin^® (containing 50% trans-resveratrol) on Helicobacter pylori strain ATCC 49503. The findings of this study indicate that Lactobacillus acidophilus DDS-1J exerts a growth inhibitory effect on H. pylori at a ratio of 1:1 or higher in vitro. In the case of clarithromycin, garcinol and resveratrol, the bactericidal effect is time and concentration dependent. Clarithromycin completely inhibited growth at 62.5 g/ml at 6 h and at 31.5 g/ml at 12 h. For garcinol the highest concentration needed for complete inhibition was 31.5 g/ml at 6 h and 3.9 g/ml after 12 h incubation. For resveratrol, significant inhibition was noted at 1000 g/ml at 12 h only. The bactericidal effect of garcinol was reduced by the addition of resveratrol at all concentrations 125 g/ml at 6 and 12 h. We conclude from this study that Lactobacillus acidophilus DDS-1J inhibits H. pylori at 1:1 and higher ratios. Also, between the two antioxidants, garcinol is much more potent than resveratrol as a bactericidal agent against H. pylori, and that resveratrol may antagonize this effect. Finally, our study showed equivalent or better bactericidal activity of garcinol compared to clarithromycin against H. pylori at 6 and 12 h incubation, indicating a potential role for this antioxidant in treatment for H. pylori infection.