The role of sugars in the respiration of differently cultivated green algae

A study of the effect of exogenous sugars (fructose, glucose, arabinose and xylose) on Qo₂ inChioreila pyrenoidosa (A 82) and inScenedesmus obliquus (A 125) showed that the effect of sugars on respiration depends on previous cultivation of the alga. In autotrophically cultivated algae all sugars contribute to the increase of Qo₂, in those cultivated rnixotrophically (with the addition of glucose or together with yeast extract, and with xylose) this occurs only in Scenedesmus when glucose or xylose are applied. The effect of cultivation was apparent in that mixotrophically cultivated algae had larger endogenous reserves of substrates than the autotrophic ones. The exogenous substrate is not preferentially respired and does not affect respiration solely as its substrate. In Chlorella, the effect of different cultivation conditions is more pronounced, the QO₂ being usually higher than inScenedesmes.     

High increment of triglycerols with ether linkages in the retina during anoxia

In the bovine retina incubated during 90 min in a medium lacking glucose without preoxygenation and gassed with O₂-free N₂ a striking rise in triglycerides with ether bonds was found. NaF and 2,4-DNP decrease the production of these molecules while cycloheximide (1.78mM) completely abolishes the phenomenon. The free fatty acid pool increases about six-fold and this rise is not affected by the inhibitors. Bovine serum albumin stimulates the free fatty acid and triglycerols production. The amount of these lipids decrease by further incubation under normoxia in the presence of glucose.     

Respiratory Response of Acer pseudoplatanus Cells to Pyruvate and 2,4-Dinitrophenol

The endogenous respiration rate of unstarved cultured cells of Acer pseudo-platanus L. is markedly stimulated by 2,4-dinitrophenol. Pyruvate is also stimulatory but to a lesser degree than dinitrophenol. Exogenously supplied sugars cause no short-term stimulation. Pyruvate does not enhance the elevated rate of O₂ uptake in the presence of dinitrophenol but does cause additional CO₂ evolution. The endogenous concentration of pyruvate is elevated in the presence of dinitrophenol. These observations suggest that the rate of O₂ uptake by the unstarved intact cells is limited by the rate of glycolysis and that rate of glycolysis is regulated by the intracellular concentration of adenine nucleotides or inorganic phosphate. Dinitrophenol stimulation of endogenous respiration is due in part to an indirect acceleration of glycolysis but also to a more direct facilitation of oxidation in the presence of excess mitochondrial substrate.     

Transport and metabolism of glucose and arabinose in Bifidobacterium breve

Glucose was required for the transport of arabinose into Bifidobacterium breve. The non-metabolisable glucose analogue 2-deoxy-d-glucose (2-DG) did not facilitate assimilation of arabinose. Studies using d-[U-¹⁴C]-labelled arabinose showed that it was fermented to pyruvate, formate, lactate and acetate, whereas the principal metabolic products of d-[U-¹⁴C]-labelled glucose were acetate and formate. In contrast to glucose, arabinose was not incorporated into cellular macromolecules. A variety of metabolic inhibitors and inhibitors of sugar transport (proton ionophores, metal ionophores, compounds associated with electron transport) were used to investigate the mechanisms of sugar uptake. Only NaF, an inhibitor of substrate level phosphorylation, and 2-DG inhibited glucose assimilation. 2-DG had no effect on arabinose uptake, but NaF was stimulatory. High levels of phosphorylation of glucose and 2-DG by PEP and to a lesser degree, ATP were seen in phosphoenolpyruvate: phosphotransferase (PEP:PTS) assays. These data together with strong inhibition of glucose uptake by NaF suggest a role for phosphorylation in the transport process. Arabinose uptake in B. breve was not directly dependent on phosphorylation or any other energy-linked form of transport but may be assimilated by glucose-dependent facilitated diffusion.Abbreviations (2,4-DNP) 2,4-dinitrophenol - (2,4-DNP) carbonylcyanide m-chlorophenylhydrazone - (CCCP) (phosphoenolpyruvate phosphotransferase system) - PEP: PTS trichloroacetic acid - (TCA) 2-deoxy-d-glucose - (2-DG) 2-deoxy-d-glucose     

Enhancement of Anaerobic Respiration in Root Tips of Zea mays following Low-Oxygen (Hypoxic) Acclimation

Root tips (10-millimeter length) were excised from hypoxically pretreated (HPT, 4% [v/v] oxygen at 25°C for 16 hours) or nonhypoxically pretreated (NHPT, 40% [v/v] oxygen) maize (Zea mays) plants, and their rates of respiration were compared by respirometry under aerobic and anaerobic conditions with exogenous glucose. The respiratory quotient under aerobic conditions with 50 millimolar glucose was approximately 1.0, which is consistent with glucose or other hexose sugars being utilized as the predominant carbon source in glycolysis. Under strictly anaerobic conditions (anoxia), glycolysis was accelerated appreciably in both HPT and NHPT root tips, but the rate of anaerobic respiration quickly declined in NHPT roots. [U-¹⁴C]Glucose supplied under anaerobic conditions was taken up and respired by HPT root tips up to five times more rapidly than by NHPT roots. When anaerobic ethanol production was measured with excised root tips in 50 millimolar glucose, HPT tissues consistently produced ethanol more rapidly than NHPT tissues. These data suggest that a period of low oxygen partial pressure is necessary to permit adequate acclimation of the root tip of maize to subsequent anoxia, resulting in more rapid rates of fermentation and generation of ATP.     

Homologous npdGI Genes in 2,4-Dinitrophenol- and 4-Nitrophenol-Degrading Rhodococcus spp.

Rhodococcus (opacus) erythropolis HL PM-1 grows on 2,4,6-trinitrophenol or 2,4-dinitrophenol (2,4-DNP) as a sole nitrogen source. The NADPH-dependent F₄₂₀ reductase (NDFR; encoded by npdG) and the hydride transferase II (HTII; encoded by npdI) of the strain were previously shown to convert both nitrophenols to their respective hydride Meisenheimer complexes. In the present study, npdG and npdI were amplified from six 2,4-DNP degrading Rhodococcus spp. The genes showed sequence similarities of 86 to 99% to the respective npd genes of strain HL PM-1. Heterologous expression of the npdG and npdI genes showed that they were involved in 2,4-DNP degradation. Sequence analyses of both the NDFRs and the HTIIs revealed conserved domains which may be involved in binding of NADPH or F₄₂₀. Phylogenetic analyses of the NDFRs showed that they represent a new group in the family of F₄₂₀-dependent NADPH reductases. Phylogenetic analyses of the HTIIs revealed that they form an additional group in the family of F₄₂₀-dependent glucose-6-phosphate dehydrogenases and F₄₂₀-dependent N⁵,N¹⁰-methylenetetrahydromethanopterin reductases. Thus, the NDFRs and the HTIIs may each represent a novel group of F₄₂₀-dependent enzymes involved in catabolism.     

Correlation Between Responses of Elongation of Wheat Coleoptile Segments to Abscisic Acid and Exogenous ATP

The time course of elongation and oxygen consumption of wheat coleoptile segments in 38μM ABA solution and 5 × 10-5 M 2,4-DNP solution were investigated. At the same time, effects of exogenous ATP (1 mM) on elongation and ABA response in wheat coleoptile segments were observed. Within the first hour of treatment, ABA and 2,4-DNP rapidly inhibited elongation in the coleoptile segments. Exogenous ATP stimulates elongation in coleoptile segments. When segments pretreated with ATP and then transfered into ABA solution, elongation in coleopfile segments were not inhibited. On the basis of the similarities of action pattern of ABA and 2,4-DNP and marked decrease of ABA inhibiting effect in presence of exogenous ATP, it is testified that uncoupling of respiration and oxidative phosphorylation is one of ABA important effects, so it is suggested that ABA inhibiting elongation of wheat coleoptile segments by decreasing tissue energy (ATP) levels necessary for synthetic reactions, including nucleic acid and protein, and associated with elongation.     

Respiration in cell development

Summary Dark oxygen uptake was measured manometrically for cells of green high-temperature alga, Chlorella 7-11-05, separated from nonsynchronized populations by centrifugation into fractions of predominantly small or large cells. In the presence of exogenous glucose, respiration activity of the smaller (younger) cell fraction was invariably higher than that of the larger (older) cell fraction. In the absence of exogenous substrate, the difference in respiration rates in two fractions of cells was inconsistent from one experiment to another both in size and in sign. The dependence of dark respiration on the amount of available substrate makes the endogenous respiration rate unsuitable as an indicator of the inherent capacity of respiratory mechanisms.In observations on synchronized heterotrophically grown cells, the glucose respiration rate expressed per dry weight of cells gradually declined over the developmental period irrespective of the adequate exogenous supply of glucose or illumination by weak light. Observations on synchronized heterotrophically grown Chlorella cells thus corroborated studies of glucose respiration in cells separated into are groups by centrifugation.The decline in metabolic activity in the course of cell development previously established for growth and photosynthesis extends to include respiration activity. Disagreements among several investigators in regard to the course of respiration during cell development are probably due to the effects of accessory factors such as strong light during the preceding growth period or the scarcity of respiratory substrate during respiration measurements which affect and distort changes in the inherent capacity of metabolic mechanisms in the course of cell development.     

Concentration-Dependent inhibition and enhancement of glutamine synthetase,glutamate dehydrogenase and nitrate reductase activities in pea roots by some respiratory inhibitors and uncouplers

The effect of 2,4-dinitrophenol (2,4-DNP), NaN₃, and iodoacetic acid (IDA) on glutamine synthetase (GS) and the effect of arsenate on GS, glutamate dehydrogenase (GDH) and nitrate reductase (NR) was studied in isolated pea roots. In sucrose supplied roots, GS level is depressed by higher concentrations of all the inhibitors tested and increased by lower (2 × and 3 × 10⁻ M) concentrations of 2,4-DNP; the decrease in GS level caused by sugar starvation is enhanced by all but IDA. GDH is enhanced by arsenate in a wider range of concentrations in sucrose-supplied roots than in roots cultivated without sucrose. NR is affected by arsenate similarly as GS.     

THE EFFECT OF CARBON DIOXIDE TENSION ON TISSUE METABOLISM (RETINA)

The metabolism of rat retina was found to be sensitive to the concentration of the carbon dioxide-bicarbonate buffer system. Increasing the carbon dioxide from 1 per cent to 5 per cent at constant pH nearly doubled both respiration and glycolysis. Increasing the carbon dioxide at constant pH from 5 per cent to 20 per cent had no effect on glycolysis, but depressed the Q _OO2 from 31 to 19. In a medium containing glucose and the 1 per cent carbon dioxide-bicarbonate buffer, the addition of succinate increased the Q _OO2 from 12 to 26, without affecting glycolysis. In a medium containing glucose and phosphate, succinate had no significant effect.     

Energy metabolism of isolated rat thymus cells

The energy metabolism of rat thymus cells has been investigated using preparations of isolated cells obtained by mechanical treatment of whole organs. The addition of glycolytic substrates such as glucose, pyruvate and lactate stimulates the endogenous respiration of these cells by 50%. On the other hand, succinate, glutamate and malate do not produce any effect. Oligomycin (10 mug/ml) inhibits both endogenous and glucose stimulated respiration by about 40%; 2, 4-DNP (50 muM) increases by 100% glucose induced respiration. The results obtained by using mitochondrial and glycolytic inhibitors as well as aminoxyacetic acid (AOA) and following pyridine nucleotides redox changes, support the idea that in thymus cells glucose is able to induce a great enhancement of O2 consumption both by raising the level of endogenous pyruvate and feeding the mitochondrial respiratory chain with cytosolic reducing equivalents, through an active malate-aspartate shuttle. Thymus cells exhibit a high Pasteur effect (74%). Both AOA and 2,4 DNP are able to stimulate aerobic lactate accumulation by 200% and 100% respectively, indicating that either the redox or phosphate potential do influence the rate of aerobic glycolysis in isolated thymus cells. Similar experiments are also reported on other cells with well known biochemical characteristics.     

Integration of algae cultivation as biodiesel production feedstock with municipal wastewater treatment: strains screening and significance evaluation of environmental factors

The objectives of this study are to find the robust strains for the centrate cultivation system and to evaluate the effect of environmental factors including light intensity, light–dark cycle, and exogenous CO₂ concentration on biomass accumulation, wastewater nutrient removal and biodiesel production. The results showed that all 14 algae strains from the genus of Chlorella, Haematococcus, Scenedesmus, Chlamydomonas, and Chloroccum were able to grow on centrate. The highest net biomass accumulation (2.01 g/L) was observed with Chlorella kessleri followed by Chlorella protothecoides (1.31 g/L), and both of them were proved to be capable of mixotrophic growth when cultivated on centrate. Environmental factors had significant effect on algal biomass accumulation, wastewater nutrients removal and biodiesel production. Higher light intensity and exogenous CO₂ concentration with longer lighting period promote biomass accumulation, biodiesel production, as well as the removal of chemical oxygen demand and nitrogen, while, lower exogenous CO₂ concentration promotes phosphorus removal.     

Microbial degradation and detoxification of 2,4-dinitrophenol in aerobic and anoxic processes

A bacterial strain was isolated from a river sediment in Buenos Aires, Argentina, owing to its ability to utilize 2,4-dinitrophenol (2,4-DNP) as the sole carbon, nitrogen and energy source. The strain was identified as Rhodococcus opacus on the basis of its 16S rRNA gene sequence. R. opacus degrades aerobically 0.27 and 0.54 mM within 22 and 28 h, respectively, and releases the nitro groups from 2,4-DNP as nitrites. Aerobic biodegradation processes were performed using a 2-l volume microfermentor at with agitation (200 rpm), and were evaluated by spectrophotometry, high performance liquid chromatography (HPLC) and microbial growth. The absence of 2,4-DNP transformation products was also confirmed by gas chromatography mass spectrometry (GC–MS). As the nitrite released during 2,4-DNP degradation is in addition an environmental toxic agent it was removed by denitrification in an anoxic process. Detoxification was assessed by using luminescent bacteria, algae and seeds toxicity tests. Toxicity was not detected after combining both the aerobic and anoxic processes.     

Polarographische Messung der Nitritreduktion von Chlorella im monochromatischen Licht

Summary In green plant cells nitrite is reduced by two systems, one dependent on photosynthesis and the other upon respiration. Using a polarographic method for continuous measurement of nitrite uptake, the relationship between light driven and respiration linked nitrite reduction of Chlorella cells was studied.Photosynthetic nitrite reduction is characterized by a pronounced increase in the velocity of nitrite uptake upon illumination. After the light is turned off the velocity immediately returns to the preillumination value. Photosynthetic nitrite reduction of Chlorella is separated from respiration linked nitrite reduction by illumination with red light under anaerobic conditions; it is stimulated by CO₂ and is inhibited by DCMU, findings which confirm earlier observations.In white light a special blue light stimulation of nitrite uptake is overlapped by photosynthetic nitrite reduction. In contrast to photosynthetic nitrite reduction this type of light stimulation is characterized by a lag period of about I min from the onset of illumination; it continues about 10 min when the light is turned off. It is separated from photosynthetic nitrite reduction by irradiation of the algae with low intensities of short wavelength light (<500 nm). Blue light stimulation of nitrite uptake of Chlorella is strongly dependent on the developmental stage of the cells. It is observed with young cells (autospores) of synchronized algae only.There is no evidence for any connection between blue light stimulation of nitrite uptake and photosynthesis. From the sensitivity of this process towards anaerobic conditions and antimycin A it is concluded to be a stimulation of respiration linked nitrite reduction.Under conditions of low exogenous nitrite concentration a temporary inhibition of steady state dark nitrite reduction appears immediately after the light is turned off. From several observations it is concluded that the inhibition already exists during the preceding illumination and decreases the rate of total nitrite uptake in the light. This process is suppressed by inhibition of respiration as well as by the inhibitor of photosynthesis, DCMU.If nitrate is the source of nitrogen an excretion of nitrite is found following illumination. The kinetics of this process agree with those observed for the light induced inhibition of steady state dark nitrite reduction immediately after illumination.     

Respiratory Physiology of a Facultative Anaerobe, Romanomermis culicivorax

The respiratory physiology of postparasitic larval and adult Romanornermis culicivorax was studied by manometric and polarographic methods. Endogenous respiration rates were relatively low and unaffected by postemergent development. The respiratory quotient (RQ) of larvae and young adults was 0.4 but increased to 0.7 about 3 wk after emergence. Exogenous glucose (0.02 mM) had no effect on QO₂ or RQ. Respiration of adults and larvae was completely inhibited by KCN (l mM) but not by NaN₃ (l mM) or 2,4-DNP (0.1 mM). The nematodes survived exposure to cyanide (l mM) for 18 h. Carbon dioxide (10%) inhibited respiration. The postparasitic stages of the nematode were mixed respiratory regulators-conformers. Exposure to anaerohic conditions resulted in an increased postanaerobic oxygen consumption which persisted for 3.5 h. The experiments confirmed that the postemergent stages of the nematode are facultative anaerobes.     

Some regulatory properties of glycogen phosphorylase from Streptococcus salivarius

Purified (200-fold) glycogen phosphorylase (EC 2.4.1.1) of Streptococcus salivarius was activated by AMP and NaF when assayed both in the direction of synthesis and in the direction of phosphorolysis. Activation by NaF + AMP was greater than the sum of their individual effects. In the direction of synthesis, the K_m for AMP was 0.25 mm and was decreased to 0.125 mm in the presence of NaF. The K_m for NaF was 0.49 m and was decreased to 0.40 m in the presence of AMP. Glycogen phosphorolysis was similarly affected by AMP and NaF, except that above a concentration of 2 mm AMP was inhibitory. The effects of AMP and NaF were reversible since preincubation with these compounds, followed by dialysis, restored activity almost to the control values although some inhibition of enzyme activity was noted with the samples preincubated with NaF. The presence of both NaF and AMP had no effect on the K_m values for glucose-1-P and glycogen in the direction of synthesis, but increased the V of the enzyme.When assayed in the absence of AMP and NaF in the direction of synthesis, the enzyme was slightly inhibited by glucose and glucose-6-P, and activated by P-enolpyruvate and ADP-glucose. In the presence of AMP and NaF, the enzyme was inhibited by glucose, glucose-6-P and ADP-glucose, but was activated by P-enolpyruvate. Fructose-1,6-P₂ had no effect on the enzyme. The enzyme was further activated in the absence of AMP and NaF by adenosine, ATP, GMP, cyclic AMP and ADP, and was slightly inhibited by GTP and GDP. In the presence of AMP and NaF, however, these compounds, with the exception of adenosine, either did not show any effect or were slightly inhibitory. Adenosine was slightly stimulatory with NaF + AMP, but not with AMP alone. In the direction of phosphorolysis, the enzyme was inhibited by glucose and ADP-glucose, and activated by P-enolpyruvate, fructose-1,6-P₂ and ATP, both in the presence and absence of AMP + NaF.     

Effects of oxytetracycline on populations and community metabolism of an aquatic microcosm

To investigate the ecological impacts of a widely-used antibiotic agent oxytetracycline (OTC), we prepared an aquatic microcosm consisting of two green algae (Chlorella sp. and Scenedesmus sp.), a blue-green alga (Tolypothrix sp.), a protozoan (Cyclidium sp.), two rotifers (Philodina sp. and Lecane sp.), an aquatic oligochaete (Aeolosoma hemprichi), and bacteria. We investigated the effects of OTC on population abundance of composite species, gross primary production (GPP), and community respiration (CR). We linked population abundance, GPP and CR to understand the relationship between these measures. First, ‘experimental respiration rate of heterotrophs’ (HR_exp) was obtained by CR minus algal respiration that is calculated by 0.35 × GPP. Next, the population respiration of each heterotroph was calculated from the direct measure of population abundance and the assumed constant of per-capita respiration. We defined the sum of the population respirations across all heterotrophs as ‘theoretical respiration rate of heterotrophs’ (HR_theo). Finally, relative community metabolism (RCM) of the heterotrophic community was obtained by calculating the ratio of HR_exp to HR_theo that indicates changes in specific respiration rates as a whole in the community. The influence of OTC on RCM was larger than on CR, thus the effect of OCT on the metabolism of heterotrophs was far more severe than expected from CR. RCM can magnify the rate of change in the original data, and facilitate the detection of influences in ecotoxicological studies.     

Inhibition of thyroid secretion by sodium fluoride in vitro

NaF mimicked the activation by thyrotropin of iodide binding to proteins and of glucose C-I oxidation but not the accumulation of intracellular colloid droplets or the stimulation of secretion in dog thyroid slices in vitro. On the contrary, NaF inhibited the two latter thyrotropin effects. The inhibitory action of F⁻ was partially relieved by the addition of glucose to the medium; it was mimicked by sodium oxamate. These data suggest that NaF depresses the endocytosis of colloid and thyroid secretion by inhibiting aerobic glycolysis in the follicular cell. NaF inhibited the activation of colloid droplet accumulation and secretion by N⁶,O^2′-dibutyryl-adenosine 3′,5′-monophosphate (dibutyryl cyclic AMP) and the accumulation of cyclic AMP in thyrotropin-stimulated slices. This suggests an inhibition at the level of both cyclic AMP accumulation and cyclic AMP action. The inhibition by NaF and sodium oxamate of colloid droplet formation and thyroid secretion but not of glucose C-I oxidation in stimulated slices further confirms our conclusion that the latter effect is not merely a consequence of the activation by thyrotropin of colloid endocytosis.     

Effects of alternative carbon sources on biological transformation of nitrophenols

The removal of nitrophenols under denitrifying conditions was studied in bench-scale upflow anaerobic sludge blanket (UASB) reactors (R1, R2, R3 and R4) using three different carbon sources. Initially acetate was used as carbon source (substrate) in all the four reactors followed by glucose and methanol. Reactor R1 was kept as control and R2, R3, R4 were fed with 30 mg/l concentration of 2-nitrophenol (2-NP), 4-nitrophenol (4-NP), and 2,4-dinitrophenol (2,4-DNP), respectively. Throughout the study the hydraulic retention time (HRT) and COD/NO₃ ^-–N ratio were kept as 24 h and 10, respectively. 2-Aminophenol (2-AP), 4-aminophenol (4-AP) and 2-amino,4-nitrophenol (2-A,4-NP) were found as the major intermediate metabolites of 2-NP, 4-NP and 2,4-DNP degradation, respectively. Methanol was found to be a better carbon source for 4-NP and 2,4-DNP degradation as compared to acetate and glucose, while 2-NP degradation was not influenced much by the change of substrate. Nitrate nitrogen removal was always more than 99%. COD removal efficiency of the nitrophenol fed reactors varied from 85.7% to 97.7%. The oxidation-reduction potential (ORP) inside the reactors dropped, up to –300 mv, with glucose as carbon source. As the reactors were switched over to methanol, ORP increased to –190 mv. The granular sludge developed inside the reactors was light brown in colour when acetate and glucose were used as substrate, which turned dark brown to black at the end of methanol run. Biomass yield in terms of volatile suspended solids was observed as 0.15, 0.089 and 0.14 g per gram of COD removal for acetate, glucose and methanol, respectively.     

Growth relationships of a lipid-producing Chlorella-alga with common microalgae in laboratory co-cultures

Co-existence growth relationships were studied in communities consisting of a lipid-producing alga Chlorella sp. HQ, another green alga and one cyanobacterium: I Scenedesmus obliquus and Microcystis aeruginosa; II Chlamydomonas reinhardtii and Anabaena flos-aquae; III Selenastrum capricornutum and Microcystis wesenbergii. The cyanobacteria and green algae except for Chlorella sp. HQ were commonly detected in Chinese reservoir and wastewater. The rate of increase of apparent cell number difference with other algae (k _app), inhibition/stimulation ratio (ISR) and the parameters of logistic model and co-existence model were determined for Chlorella. Chlorella strains were the most competitive in Combination I, and were stimulated during 75% of the cultivation time for all three combinations. Anabaena growth exceeded those of Chlorella and Chlamydomonas on the 5th cultivation day under 1 : 1 : 1 inoculum ratio. Scenedesmus colonies consisted of fewer cells, whose average length significantly shortened after the 5th cultivation day under 1 : 1 : 1 inoculum ratio. The developed co-existence model can identify the concrete growth inhibitor or stimulator among three species compared with the single method of cell number monitoring. Good correlation was found between transformed and non-transformed co-existence model through a _mn and b _mn values. Allelopathy and nutrient competition are both possible mechanisms in the above growth relationships.