Article

Couplage saisonnier entre nucléotides adényliques et activité photosynthétique de diverses fractions de taille phytoplanctoniques en milieu lacustre eutrophe

Authors:
To read the full-text of this research, you can request a copy directly from the author.

Abstract

As part of the study of the eutrophic lake Aydat (Massif Central, France), the energy charge (CE = ATP + 1/2 ADP/ATP + ADP + AMP) and photosynthetic activity of size fractionated phytoplankton (0,2–160 μn; 0,2–45 μm and 12–160 μm) were assessed from April to November (1985). Weekly samples were gathered from several depths in both the euphotic and dysphotic zones. The fraction 0,2–45 μm showed elevated primary production and weak energy charge percentages confirming the generally accepted idea about the increase of metabolical cell processes with lower cell size. We have also looked for the ecophysiological significance of the energy charge through its seasonal coupling with primary production. The highly significant negative correlations obtained between CE and primary production for the three fractions indicate that the pool of adenine nucleotides evolves towards forms less charged with a high energy phosphate bond. However, some exceptions to this rule were noticed in April and June (both CE and photosynthetic activity were high). This observation derived from in situ studies showed the difficulties encountered in natural environments when we try to check the ecophysiological significance of the energy charge.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the author.

Article
Full-text available
In the eutrophic Ghar El Melh Lagoon (GML, Tunisia), the distribution of heterotrophic prokaryotes, pico- and nanophytoplankton was studied at five stations in November 2012 at the single cell level, along with environmental factors. Flow cytometry analysis of ultraplankton (<10 µm) resolved (i) two heterotrophic prokaryote groups: LNA and HNA (low and high nucleic acid content, respectively), and (ii) eight to nine ultraphytoplankton groups (cryptophyte-like cells, two nanoeukaryote subgroups, two picoeukaryote subgroups and three Synechococcus-like cells subgroups). Prochlorococcus was not detected. According to redundancy analysis (RDA), a significant difference was found in the distribution of the ultraplankton between stations (F = 2.61, p < 0.05), maximum proliferations of heterotrophic prokaryotes were observed in the inner parts of the lagoon at stations 3, 4 and 5 affected by urban, agricultural and industrial discharges. Ultraphytoplankton concentrations were the highest near the outlet of the lagoon at stations 1 and 2 influenced by freshwater outflow and oligotrophic Mediterranean water inflow, respectively. At station 1 the large ultraphytoplankton concentration derives from the high abundance of cryptophyte-like cells favoured by the freshwater outflow whereas at station 2 the input of oligotrophic Mediterranean water enhanced the abundance of Synechococcus and picoeukaryotes at the expense of nanoeukaryotes. Two trophic regimes were thus differentiated in GML.
Article
Full-text available
The authors investigated the microbial composition of phototrophic biofilms proliferating in a show cave using flow cytometry for the first time in such a context. Results are based on several biofilms sampled in the Moidons Caves (France) and concern both heterotrophic prokaryotes and autotrophic microorganisms. Heterotrophic microorganisms with low nucleic acid content were dominant in biofilms, as can be expected from the oligotrophic conditions prevailing within the cave. Analysis of the biofilm autotrophic components revealed the presence of several taxa, particularly the unicellular green algae Chlorella minutissima, specifically well adapted to this cave. Relationships between flow cytometry results and environmental variables determined in the cave were established and discussed so as to better understand biofilm proliferation processes in caves.
Article
Full-text available
The summer spatial distribution of the phytoplankton community in the Gulf of GabHannibalopen sea gradient, was dominated by Dictyochophyceae (41%) followed by Dinophyceae (25%), Bacillariophyceae (16%), Cyanobacteriae (17%) and Euglenophyceae (1%). The phytoplankton found along the coast was dominated by opportunistic species (e.g. Dictyocha fibula) associated with high nutrient availability. In the open sea, phytoplankton development seemed influenced by Atlantic hydrodynamics. In addition, the Gulf of Gabs.
Article
Full-text available
An ecological model for the solar saltern of Sfax (Tunisia) was established and validated by comparing simulation results to observed data relative to horizontal distributions of temperature, nutrients and phytoplankton biomass. Sensitivity analysis was performed in order to assess the influence of the main ecological model parameters. First applied at the saltern's pond A1, the model was calibrated with field data measured over 4 years of study (from 2000 to 2003), which allowed an evaluation of parameters such as maximum growth rate of phytoplankton, optimal growth temperature and constant of half saturation for P/N assimilation by phytoplankton. Simulation results showed that the model allowed us to predict realistic phytoplankton variations of the study area, though we were unable to accurately reproduce the nutrient variation. The model was then applied to simulations of the impact of changes in phytoplankton biomass through scenarios such as hypothetic climate changes and saltern restoration.
Article
a b s t r a c t The distribution of phytoplankton abundance, biomass and species composition coupled with environ-mental factors and metazooplankton was studied relatively intensively and over a period of four consecutive years in five ponds featuring a gradient of increasing salinity from near to that of sea water to a nine-fold concentration from 2000 to 2003. The results indicate that the physical characteristics of the water (temperature and salinity) were quite similar over the years. Nutrients, which were concentrated in pond A1, decreased with increases in salt concentration. The composition of the phytoplankton community showed strong seasonality. Diatoms dominated in the first ponds A1, A16 and C2-1, followed by dinoflagellates. Chlorophyceae dominated the phytoplankton community in the hypersaline ponds M2 and TS. Cyanobacteriae were relatively abundant in ponds M2 and TS. The highest phytoplankton density and biomass were found in the ponds with the highest salinity due to the proliferation of Dunaliella salina (Chlorophyta: Volvocales). The inter-annual study of phytoplankton succession in the Sfax solar salterns showed slight differences among the years of study due to the stability of the envi-ronmental conditions. Phytoplankton communities were permanently primitive, stage 1 e structured as they failed to build complexity because of salt stress which operates for longer and above any other variables. This reduced frequency of disturbance to the existing course of regulation, allowed the community to "mature" from its "primitive" state, rather than experience frequent structural setbacks.
Article
The distribution of abundance and biomass of prokaryotes, flagellates, ciliates and phytoplankton, were studied in five ponds of increasing salinity in the Sfax solar saltern (Tunisia) coupled with environmental factors. The results showed that abundance of eukaryotic microorganisms decreased with increasing salinity of the ponds whereas prokaryotes (heterotrophic bacteria and Archaea) were abundant in the hyper-saline ponds. Phototrophic picoplankton was found in a large range of salinity values (70 and 200‰). Phototrophic non-flagellated nanoplankton which dominated in the first sampled pond was substituted by phototrophic flagellated nanoplankton in the other ponds. Heterotrophic nanoplankton dominated in the crystallizer pond but its quantitative importance declined in the less saline ponds. Diatoms and dinoflagellates were the major contributors to phytoplankton abundance in the first ponds (>90% of total abundance). Ciliated protozoa were found in all the ponds except in the crystallizer in which prokaryotes proliferated. Oligotrichida and Heterotrichida were the most abundant ciliate groups. Overall, species richness decreased with salinity gradient. We propose a simplified diagram of the Sfax saltern's food web showing the dominant role of the microbial loop along the salinity gradient.
Article
Full-text available
The paper presents a laboratory investigation of the temperature- and light- dependence of autotrophic growth of the alga Chlorella minutissima. It was isolated from the storage basin of a spring in the mountains of the Massif Central, France. The alga was grown at temperatures between (10 and 35 °C) and under irradiances from 30 to 550 μmol m(-2) s(-1), under a light/dark cycle. The results were fitted to selected descriptive models, seeking to express, as far as possible, the observed physiological behaviour of the strain and the minimum irradiance required to sustain net growth. At all temperatures, the maximum rates of growth observed are strikingly slower than those of other Chlorella strains and of other small algae, reported in the literature, even when correction is made for continuous light. The Q10 statistic for growth at temperatures>20 °C rates is also noticeably lower than in other species, while the apparent threshold of any growth is about 8 °C. Growth rates are readily light-saturated at all temperatures but with little evidence of adaptation of photosynthesis to low photon-flux rates. No short-term flexibility in these properties (over a time-scale of days) was demonstrated during the course of our experiments. We deduce that the algal strain had become genetically adapted to the relatively constant, even-temperature and low-light conditions of the spring-water habitat whence it was originally isolated.
Article
Nanoplankton biomass represented a low part (mean 22%) of total biomass, in accordance with the trophic status of lac d'Aydat, Massif Central, France. Microplankton energy charge were higher. -from English summary
Article
Large single phytoplankton cells are likely to catabolize a smaller fraction of their biomass than do small phytoplankton cells. Under certain environmental conditions, this characteristic may be highly important in regulating the growth rates of large versus small phytoplankton. A model is developed incorporating experimental data on phytoplankton growth, respiration, and sinking rates as a function of cell size. Application of the model to specific oceanic regions shows that the net growth rate of large cells may exceed that of small cells when the mixed layer is relatively deep, despite the larger gross production rates characteristics of the smaller cells.
Article
(1) Measurements were made of ATP, ADP and AMP concentrations and the corresponding adenylate energy charge quotient (EC), in cultures and field studies, to assess their potential as indicators of the metabolic state of freshwater micro-organisms in situ. (2) Decreases in EC from 0.81 to 0.68, during filtration, and from 0.90 to 0.69, during light/dark shocks, may result in errors of over 60% in the estimated ATP content of cells, if care is not taken during extraction. (3) The EC values, during logarithmic growth in culture, of the blue-green algae Oscillatoria agardhii and O. redekei were 0.82 and 0.83 respectively. These declined to 0.57 and 0.63 after nitrogen limitation in culture. (4) In a well-mixed lake (L. Neagh, N. Ireland), where both these species occur, no change in the EC quotient (0.79 ± 0.04) was detected in the water column between April and November. (5) Greater variation was found in a range of deep, stratified lakes in Austria (Wallersee, Mondsee, Attersee) and the factors influencing the depth differences in EC quotients, ranging from 0.47 to 0.82, are discussed.
Article
La production primaire phytoplanctenique et l'activite heterotrophe bacterienne ont ete etudiees parallelement sur le lac d'AYDAT en 1985. L'activite photosynthetique, mesuree au alentours du midi solaire evolue entre 10 et 141 mg C m-2h-1, le maximum etant atteint en juillet. La vitesse maximale, V max, d'assimilation de glucose par les bacteries, (en presence de concentrations de traceur non limitantes) se situe entre 0,06 - 1,26 mg C m-2h-1. Le compartiment phytoplanctonique, de par sa production, semble etre l'un des elements regulateurs de l'activite heterotrophe bacterienne en zone epilimnique.
Article
The size of phytoplankton species present in the ocean may be in part determined by environmental and Dhvsioloeical factors as demonstrated with two phytoplankters, DityZum brightwellii and Cokblithu~ huxleyi.
Article
Influences of unsalted waters penetration, in the Gulf of Fos, are marked as much on the primary step structuration level as on the component cellular physiology one. At their outlet, the weak structuration and the considerable biomasses resulting from an intense eutrophication go with a strong mortality clearly shown as well as by ATP/chlorophyll ratio than these of ATP, ADP and AMP inside the adenylic nucleotides pool. The primary step acquires a larger maturity in the salt share of the south eastern area. Spectrum variations of the population specific cellular volumes in terms of population importance can in a certain measure explain the intracellular rate variations into biochemical components.
Article
Algal chlorophyll, carbon fixation and alkaline phosphatase activity were net-fractionated using 22-μm, and 75-μm screens in three lakes with contrasting zooplankton communities. Size distributions of algal biovolume were also determined through microscopic examination. Relatively good correspondence was found between size distributions obtained through net fractionation and those determined by microscopic examination. Biovolume-specific carbon fixation and chlorophyll decreased with increasing fraction size but no differences were observed among fractions for chlorophyll-specific carbon fixation. High algal standing stocks and low phosphorus deficiency in Tuesday Lake were attributed to low grazing pressure by small, inefficient zooplankton and possible limitation by nutrients other than phosphorus. Algal standing stocks were low and phosphorus deficiency was high in Peter and Paul Lakes, in which the zooplankton was dominated by large grazers. Different algal size fractions experienced differing degrees of phosphorus deficiency. These size fraction differences in P-deficiency in Peter and Paul Lakes were attributed to differences in algal species composition and to differing levels of zooplankton grazing pressure and nutrient regeneration. A unimodal relationship between relative nanoplankton biovolume and zooplankton biomass was found and reflects the positive (nutrient regeneration) and negative (grazing mortality) effects of zooplankton on the algal community.
Article
Guidelines for submitting commentsPolicy: Comments that contribute to the discussion of the article will be posted within approximately three business days. We do not accept anonymous comments. Please include your email address; the address will not be displayed in the posted comment. Cell Press Editors will screen the comments to ensure that they are relevant and appropriate but comments will not be edited. The ultimate decision on publication of an online comment is at the Editors' discretion. Formatting: Please include a title for the comment and your affiliation. Note that symbols (e.g. Greek letters) may not transmit properly in this form due to potential software compatibility issues. Please spell out the words in place of the symbols (e.g. replace “α” with “alpha”). Comments should be no more than 8,000 characters (including spaces ) in length. References may be included when necessary but should be kept to a minimum. Be careful if copying and pasting from a Word document. Smart quotes can cause problems in the form. If you experience difficulties, please convert to a plain text file and then copy and paste into the form.
Article
Autoradiographs of nannoplankton show high photosynthetic fixation rates relative to net plankton during early daylight hours. However, net plankton contribute increasingly to community fixation during the afternoon and early evening. During darkness nannoplank- ton show losses of fixed 14C greatly exceeding those from net plankton. This lack of uni- formity in (14C)C02 fixation and losses will affect the short term daylight '"C measurements routinely used to assess long term trends in eutrophication.
Article
Discovery of minute (0.2-2.0 mu m) algal picoplankton in the late 1970s in both marine and freshwater ecosystems has led to a resurgence of research activity throughout the world, addressing questions related to taxonomy, distribution and abundance, physiology and biochemistry, and ecological considerations of their role in aquatic food webs. To many, their discovery provided the 'missing link' in the controversial carbon supply-demand question in the world's oceans and gave further credibility to the emerging new paradigm on the importance of microbial food webs in energy transfer and nutrient recycling in aquatic systems. -from Authors
Article
Nannoplankton and netplankton primary productivity and standing crop were measured in a wide variety of neritic and oceanic environments in the eastern tropical Pacific and Caribbean region. Nannoplankters were the most important producers in all the environ- ments studied, but netplankton productivity was significantly (P = 0.05) higher in neritic than in oceanic waters. Mean neritic netplankton-nannoplankton productivity and chloro- phyll ratios were 0.50 + 0.14 and 0.62 -C 0.22 respectively, significantly higher than those observed in oceanic waters. Relative levels of netplankton standing crop and productivity were not systematically related to corresponding levels of primary productivity and standing crop as a whole. The patterns of variation in the relative importance of netplankton and nannoplankton could be accounted for by the high netplankton growth rates and low grazing pressure indices observed in neritic as compared to oceanic waters.
Article
A method is described for the quantitative determination of adenosine triphosphate (ATP) in quantities as low as lo4 pg. Using sample volumes of less than 2 liters, two profiles of ATP concentration have been made down to 1,025 m off the California coast. The biomass of living material in the water has been estimated from these data, using the ATP content of laboratory cultured microorganisms as indicators of endogenous ATP levels. When equated to numbers of bacteria, the ATP levels found at various depths in the ocean indicate bacterial populations between 50-2,000 times those found by plating techniques.
Article
Literature values for the phosphorus and nitrogen subsistence quotas of several bacteria and unicellular algae are presented in a comparable form. Both these parameters depend on cell size.
Article
The annual cycle of phytoplankton biomass was followed in a eutrophic lake (Lake Aydat, Massif Central, France), using classic descriptors (biovolumes and chlorophyll a) as well as adenosine-5'-phosphate (ATP) levels. ATP is the metabolite indicating living biomass. ATP/Cell count and ATP/Chlorophyll a ratios were elevated due to the presence of heterotrophic organisms, such as several species of ciliates. The first ratio is greater than the second. The difference can be explained either by an underestimation of the nanoplankton fraction through the cell count method, or by a lack of sedimentation in the settling chambers used for counting cells.
Article
The diel pattern of cell division, cell carbon, adenine nucleotides and vertical migration was determined for laboratory cultures of the photosynthetic marine dinoflagellate, Ceratium furca (Ehr.) Clap. & Lachm., entrained on an alternating 12:12 LD schedule at 20 C. Cell division was initiated during the latter portion of the dark period with ca. 30% of the population undergoing division. Cell C increased during the light period and exhibited a linear decrease with a loss of 33% during the dark period. ATP · cell−1 increased during the light period and decreased by ca. 40–50% during the dark period. The diel patterns of cell C and ATP tended to “buffer” the magnitude of the change in C:ATP ratios around an overall mean value of 89. There was no obvious trend in the concentration of [GTP + UTP] · cell−1 over the cell cycle. The cellular adenylate energy charge was maintained at values between 0.8 to 0.9 throughout the 24 h LD cycle, despite a ca. 40% decrease in total adenylates (AT= ATP + ADP + AMP) during the dark period on 12:12 LD, and over a 68% decrease in ATP during 42 h of continuous darkness. These data lend experimental support to the theory of cellular metabolic control by the adenine nucleotides. With lateral illumination on 12:12 LD cycles, the cells began to concentrate at the surface of the experimental tubes shortly before the lights were turned on, and at the bottom of the tubes shortly before the lights were extinguished. This pattern continued for 6 days in continuous darkness, suggesting that the vertical migration pattern is independent of a phototactic response and may be under the control of an endogenous rhythm.
Article
The distribution of three phytoplanktonic size fractions was studied in an eutrophic lake. Size fractionation experiments were performed using cell enumeration by inverted microscopy and chlorophyll a estimation. The results were also compared with the ATP content in the analysed algal fractions. The (1–12 µm) fraction represented only on average 5 % of the total biomass, when estimated by the cell enumeration method, but made up 26 % of the total chlorophyll a and 33 % of the total ATP. This discrepancy confirms that cell enumeration with an inverted microscope seriously underestimates the ‘nanoplankton’ biomass. The (12–45 µm) fraction made up to 50% of the total biomass regardless the method of analysis used. The chlorophyll a and biovolume estimation in this fraction were positively correlated. The contribution of algal species with large cell size (45–160 µm) to the total algal biomass was higher (39%) when based on their biovolume estimation than when on the chlorophyll a (27%). The low ATP contribution of this fraction (17%) may be attributable to high percentage of dead cells.
Article
In a subtropical Hawaiian ecosystem, phytoplanton size structure analyses (November–December, 1980) showed that ultraplankton (>3m), nanoplankton (>20m) and netplankton (>20m) accounted for ca. 80, 98, and 2% of total chlorophyll standing stock, respectively, on the basis of chlorophyll. Similar trends were evident, for other biomass indices (e.g. cell numbers, total cell volume, ATP, particulate organic carbon, particulate organic nitrogen). The ultraplankton fraction consisted primarily of small flagellates (1 to 3 m diam) and coccoid cells (1 m diam); the 3 to 20 m fraction was represented by dinoflagellates, coccolithophores, diatoms, and chrysophytes; and the netplankton fraction consisted principally of dinoflagellates and centric diatoms. Community photosynthesis had a size distribution similar to that of biomass. Sinking rates for the 3 m, 3 to 20 m, and >20 m fractions averaged 0.0, 0.09, and 0.29m d–1, respectively. The absence of measurable sinking rates for the ultraplankton, together with the relative abundance of biomass in this fraction, result in very small phytoplankton losses due to sinking in such subtropical surface waters.
Article
A method for measuring ATP, ADP and AMP levels in environmental samples was devised, and applied to seawater and bacterial cell extracts. This procedure is specifically designed for measuring the extremely low concentrations of total adenine nucleotides ([AT]=[ATP]+[ADP]+[AMP]) that are apt to occur in most natural ecosystems (i.e., 10 ng AT ml-1 of sample extract). Although the current assay methodology can be used with purified firefly luciferase reagents, it has been suitably modified to accept crude luciferase preparations as well. ATP, ADP and AMP levels have been measured, and the corresponding energy charge (EC) ratios determined for seawater samples collected off the Southern California coast. The EC ratios ranged from 0.50 to 0.89, with peak values corresponding to the subsurface maxima in ATP and chlorophyll a concentrations, and the minimum values corresponding to the deepest water sampled (1500 m). The measurement of adenylate energy charge ratios in environmental samples can be a useful indicator of mean community metabolic activity and potential for cell growth.
Article
Photosynthetic parameters for netplankton (>22 μm) and nanoplankton (<22 μm) varied over similar ranges but exhibited different seasonal and geographic patterns of variation. Nanoplankton a was relatively constant (0.06 mg C [mg Chl · h]-1 [μE m-2 s-1]-1), but P mB(mg C [mg Chl · d]-1) was an exponential function of temperature independent of nutrient concentration and vertical stability in the euphotic zone. The temperature function gives a P mBof 24 at 25°C for nanoplankton growing in an estuarine environment characterized by high nutrient concentrations and a shallow, stratified euphotic zone. Variations in netplankton a and P mBwere less predictable and were not correlated with temperature, nutrients or vertical stability. Chain forming diatoms with small cells were able to achieve high α (0.10 to 0.15) and P mB(20 to 24) that were 3 to 5 times higher than large-celled diatoms and dinoflagellates were able to achieve.
Article
The qualitative and quantitative significance of nannoplankton in Lake Superior in terms of taxonomy and primary production was studied during 1973. The size analysis of algae into netplankton (≥64μm) and nannoplankton (<64μm) and its various size fractions (<5; 5-10; 10-20; 20-44; 44-64μm) was based on microscopic enumeration and measurements by means of the Utermöhl procedure. Primary production experiments and their subsequent fractionation by means of Carbon-14 technique were undertaken to determine the relative photosynthetic rate of different size fractions of algae. Production /biomass quotients (activity coefficients) were computed and related to species composition. On a lakewide basis the nannoplankton was the major component of the algal biomass contributing from 57-80% and comprised mainly of Cryptophyceae, Diatomeae, and Chrysophyceae. Nannoplankton were also abundant vertically. The most common nannoplankton were: Chlorella sp., Scenedesmus bijuga (Turp.) Lagerheim, Ochromonas spp., Chrysochromulina parva Lackey, Chrysocapsa sp., Chromulina elegans Doflein, Cyclotella comta (Ehr.) Kütz. C. ocellata Pant., C. bodanica Eulen., Asterionella formosa Hass., Rhodomonas minuta Skuja, R. minuta var. nannoplanctica Skuja, Cryptomonas erosa Ehr., C. marsonii Skuja, Katablepharis ovalis Skuja, and Gymnodinium spp.
Article
Des fractionnements par taille et des autoradiographies au microscope électronique ont été utilisés pour déterminer si, dans le lac eutrophe de Nantua, l'espèce d'algue dominante #Oscillatoria rubescens$ D.C., peut entrer en compétition avec les bactéries vis-à-vis des acides aminés en solution. Les fractions supérieures à 12 (microns) où 97% des biovolumes étaient liés aux oscillaires, ont assimilés, en moyenne 64% des acides aminés 14C introduits. L'autoradiographie en section ultra mince a confirmé l'incorporation des acides aminés dans les cellules d'oscillaires. Les résultats suggèrent qu'#Oscillatoria rubescens$ peut commencer les bactéries pour l'assimilation des acides aminés dissous aux concentrations naturelles. (Résumé d'auteur)
Article
The value of the adenylate energy charge, [(adenosine triphosphate) + (1/2) (adenosine diphosphate)]/[(adenosine triphosphate) + (adenosine diphosphate) + (adenosine monophosphate)], in Escherichia coli cells during growth is about 0.8. During the stationary phase after cessation of growth, or during starvation in carbon-limited cultures, the energy charge declines slowly to a value of about 0.5, and then falls more rapidly. During the slow decline in energy charge, all the cells are capable of forming colonies, but a rapid fall in viability coincides with the steep drop in energy charge. These results suggest that growth can occur only at energy charge values above about 0.8, that viability is maintained at values between 0.8 and 0.5, and that cells die at values below 0.5. Tabulation of adenylate concentrations previously reported for various organisms and tissues supports the prediction, based on enzyme kinetic observations in vitro, that the energy charge is stabilized near 0.85 in intact metabolizing cells of a wide variety of types.
Article
The energy charge of the adenylate system, half of the average number of anhydride-bound phosphate groups per adenine moiety, has been proposed as a metabolic regulatory parameter. For several reactions that participate in biosynthesis or other adenosine triphosphate utilizing sequences, plots of enzyme activity against energy charge have positive slopes that increase with charge; thus these curves (type U) are concave upward and steep in the region of high charge. End-product feedback inhibition of the type demonstrated for many biosynthetic regulatory enzymes must be reflected in a decrease in the slope of such curves on the addition of the end product. The area between the curve representing absence of end product and that representing a saturating level of it should indicate the operational range of the regulatory enzyme. Within this range, if either end-product concentration or energy charge is constant the enzyme will respond only to variation in the other; but it may be expected that both parameters affect the behavior of the enzyme in the intact cell. For several reactions that participate in adenosine triphosphate regenerating sequences, plots of enzyme activity against energy charge have negative slopes that increase with charge; thus these curves (type R) are concave downward and steep in the region of high charge. Such sequences also supply primary metabolic intermediates needed as starting points in biosyntheses, and in some cases have been shown to be regulated also by the concentration of one or more of these intermediates. Inhibition of this type should be reflected in an increase in the negative slope of such curves on addition of the regulatory metabolite. As in the case of type U curves, a regulatory area will exist between the curves representing zero concentration and saturating concentration of the modifying metabolite. Experimental examples of both types of pattern are provided in the following two papers. It is proposed that the overlap of such regulatory type R and type U patterns illustrates graphically some of the ways in which energy charge and the concentrations of primary intermediates and of biosynthetic end products interact to stabilize the energy charge and to adjust the partitioning of substrates among competing metabolic functions in response to changing metabolic situations in the cell.
Article
The principles of ecological succession bear importantly on the relationships between man and nature. The framework of successional theory needs to be examined as a basis for resolving man’s present environmental crisis. Most ideas pertaining to the development of ecological systems are based on descriptive data obtained by observing changes in biotic communities over long periods, or on highly theoretical assumptions; very few of the generally accepted hypotheses have been tested experimentally. Some of the confusion, vagueness, and lack of experimental work in this area stems from the tendency of ecologists to regard “succession” as a single straightforward idea; in actual fact, it entails an interacting complex of processes, some of which counteract one another.
Article
1.1. Three types of light-measuring devices have been used to measure the effect of various chemical agents on firefly luminescence. They are the commercially available Farrand photofluorometer, a recording DC IP21 photomultiplier, and a liquid-nitrogen-temperature quantum counter whose ultimate sensitivity is of the order of 10−9 g. ATP/ml.2.2. It has been possible to use both the crude and partially purified water extracts of Photinus pyralis to measure light production in the presence of “potential” or actual ATP by using arsenate buffer.3.3. Differential-determination of ATP and ADP in the presence of each other is possible through the use of myokinase.4.4. Phosphocreatine may be determined by the use of the appropriate transphosphorylase and adenylic acid.5.5. Glucose may be determined by the use of hexokinase and ATP, measuring the depression in luminescence.6.6. Chloride ion has a strong inhibitory effect on luminescence which must be controlled rigorously.7.7. Myokinase, hexokinase, apyrase, and creatine adenylic transphosphorylase may be determined in small concentrations with this system.8.8. Preliminary examination of certain biological processes with this tool suggests its wide applicability for routine surveys of phosphorylative energetic mechanisms.
Bioenergetique, 238 pp. Ediscience, Paris. Traduction de l'ouvrage Bioenergetics
  • A L Lehninger
23 Lehninger A. L. (1969): Bioenergetique, 238 pp. Ediscience, Paris. Traduction de l'ouvrage Bioenergetics. Ed. W. A. Benjamin, New York (1965).
Biochemie, 834 pp. Ed. Flammarion medecine-sciences,Traduction de I'ouvrage Biochemistry
  • A L Lehninger
24 Lehninger A. L. (1972): Biochemie, 834 pp. Ed. Flammarion medecine-sciences,Traduction de I'ouvrage Biochemistry. Ed. North Publishers, Inc. (1970).
Sinking and floating The physiological ecology of phytoplankton
  • A E Walsby
  • C S Reynolds
Walsby A. E. and Reynolds C. S. (1980): Sinking and floating. In: Morris I. (ed.): The physiological ecology of phytoplankton, pp. 371-412. University of California Press, Berkeley and 1.. A. (Calif.).
The phytoplankton of Gorwain, a bay of Malare. Oikos Key words: Lake phytoplankton -Size fractionation -Photosynthetic activity
  • T Willen
Willen T. (1959): The phytoplankton of Gorwain, a bay of Malare. Oikos, 10,241-274. Key words: Lake phytoplankton -Size fractionation -Photosynthetic activity -Energy charge Lotfi Aleya, Laboratoire de Zoologie et Protistologie, Universite Blaise Pascal, UA CNRS: 138, 63177 Aubiere Cedex, France
Impact de la pollution sur un ecosysteme mediterraneen cotier
  • P Benon
  • R Blanc
  • B Bourgade
  • P David
  • R Kantin
  • M Leveau
  • J C Romano
  • D Et Sautriot
  • Adp Atp
Benon P., Blanc R., Bourgade B., David P., Kantin R., Leveau M., Romano J. c.et Sautriot D. (1977): Impact de la pollution sur un ecosysteme mediterraneen cotier. II. Relations entre la composition specifique des populations phytoplanctoniques et les taux de pigments et de nucleotides adenyliques (ATP, ADP, AMP). Int. Revue Ges. Hydrobiol., 62(5), 631-648.
Contribution ai'erude du lac d' Aydat
  • G Millerioux
Millerioux G. (1976): Contribution ai'erude du lac d' Aydat.
Dynamique des populations phytoplanctoniques du lac d' Aydat (Puy-de-Dorne, France) Biomasse et activite metabolique de diverses fractions de taille
  • L Aleya
Aleya L. (1987): Dynamique des populations phytoplanctoniques du lac d' Aydat (Puy-de-Dorne, France). Biomasse et activite metabolique de diverses fractions de taille. These Doct. Jeme cycle, Univ. Clermont II.
Abondance, biomasse, activite et relations trophiques des cornrnunautes hacteriennes heterotrophes du lac d'Aydat. Contribution al'etude des systernes aquatiques
  • O Marvalin
Marvalin O. (1988): Abondance, biomasse, activite et relations trophiques des cornrnunautes hacteriennes heterotrophes du lac d'Aydat. Contribution al'etude des systernes aquatiques. These Universire. Universite Blaise Pascal, Clermont II.