Pseudobalanion planctonicum (Ciliophora, Prostomatida): ecological significance of an algivorous nanociliate in a deep meso-eutrophic lake

Pseudobalanion plancioracum was the most abundant ciliate speciesin the pelagic zone of Lake Constance, FRG, over a 3 year period.Annual averages accounted for 30, 35 and 43% of total ciliatenumbers in the uppermost 20 m of the water column in 1987, 1988and 1989 respectively. Highest cell numbers were observed inearly spring, simultaneously with the first phytoplankton maximum.The small ciliate (mean length 15 µm, mean cell volume1300 µm³) is a raptorial feeder and predominantly consumesphytoplankton. In laboratory cultures, P planctonicum grew wellon a diet of Rhodomonas sp. (Cryptophyceae). Maximum growthrates increased from 0.46 day^–1 at 5 5°C to 1.52 day^–1at 18.5° C, while temperatures above 21°C were lethal.Depending on food concentration, 0.2–4.4 Rhodomonas cellswere ingested per ciliate and hour.     

Thermal Properties of Membrane Lipids from two Cyanobacteria, Anacystis nidulans and Synechococcus sp.

The composition and positional distribution of fatty acids inmonogalactosyldiacylglycerol, digalactosyldiacylglycerol, phosphatidylglyceroland sulphoquinovosyldiacylglycerol from two cyanobacteria, Anacystisnidulans and Synechococcus sp. grown at 25°C have been determinedand compared with measurements of the phase separation temperaturesof the lipids. Only monogalactosyldiacylglycerol in Anacystisand sulphoquinovosyldiacylglycerol in Synechococcus showed phaseseparation temperatures above 0°C. The phase transitiontemperature of a sample of sulphoquinovosyldiacylglycerol containingover 90% of the dihexadecanoyl molecular species has been determinedto be 43°C for the Na⁺ salt and 38°C for the Mg⁺⁺ salt. ^*Deceased. September 14, 1986. (Received June 25, 1986; Accepted August 25, 1986)     

Metabolism and Biosynthesis of Cytokinins in Tobacco Crown Gall Cells

The metabolism of ribosylzeatin (RZ) was studied using tobaccocrown gall cells which produce RZ as one of the major endogenouscytokinins. When [8-¹⁴C]RZ was fed to the cells, it was convertedinto its phosphate (which was rigorously determined to be the5'-monophosphate), RZ-O-glucoside, inosine (or its phosphate),adenosine and adenosine-O-glucoside. When [8-¹⁴C]N⁶-(²-isopentenyl)adenosine(i⁶Ado), a probable precursor of RZ, was fed to the cells, itwas converted into (i⁶Ado)-O-glucoside, inosine (or its phosphate),adenosine, adenosine-O-glucoside and adenosine phosphate, butno incorporation of radioactivity into RZ was observed. Thepresent study led to the following conclusions: i) i⁶Ado isnot a precursor of RZ in the cells, ii) both deaminase and cytokininoxidase are involved in the catabolism of cytokinin, and iii)the metabolism of RZ is quite different from that of i⁶Ado. (Received December 24, 1985; Accepted April 1, 1986)     

Dioxindole-3-Acetic Acid Conjugates Formation from Indole-3-Acetylaspartic Acid in Vicia Seedlings

When indole-3-acetic acid (IAA) is applied to the cotyledonsof broad bean seedlings (Vicia faba L. cv Chukyo), the majormetabolites found in the roots are 3-(O-ß-glucosyl)-2-indoIone-3-acetylaspartic acid (Glc-DIA-Asp) and 3-hydroxy-2-indolone-3-acetylasparticacid (DIA-Asp). In this report, the metabolic pathway from IAAto the two dioxindole-3-acetic acid (DIA) conjugates was investigatedby using [¹⁴C]IAA, [¹⁴C]DIA, [¹⁴C]indole-3-acetylaspartic acid(IAA-Asp), and [¹⁴C]IAA-[³H]Asp. The precursor of DIA-Asp wasfound to be IAA-Asp but not DIA. Incorporation of the doublelabeled IAA-Asp into the DIA conjugates demonstrated that hydrolysisof IAA-Asp was not involved in the formation of the DIA conjugates.DIA-Asp was further metabolized to Glc-DIA-Asp in the cotyledons,while formation of Glc-DIA-Asp in the roots was very low. Glc-DIA-Aspformed in the cotyledons was transported to the roots. (Received April 21, 1986; Accepted September 10, 1986)     

The Effect of Gabaculine on Germination and Gametophyte Morphogenesis of Anemia phyllitidis L.Sw.

Gabaculine, applied to germinating spores of the fern Anemiaphyllitidis in concentrations between 10^–4 M and 10^–6M inhibits chlorophyll synthesis together with considerablesimplification of chloroplast ultrastructure. Though gabaculinereduced phytochrome-induced morphogenetic effects (cell shape,inhibition of hormonal antheridium induction), the rate of redlight-induced spore germination, however, has not been affectedby the inhibitor. This indicates significant differences betweenthe two types of photomorphogenetic reactions regarding theirdependency on phytochrome homeostasis. (Received April 21, 1986; Accepted October 22, 1986)     

Biosynthesis of Purine Alkaloids in Camellia Plants

The metabolism of [8-¹⁴C]adenine and [8-¹⁴C]hypoxanthine infour species of Camellia plants was investigated in relationto the synthesis of purine alkaloids, caffeine and theobromine.Young leaves of C. sinensis had the ability to synthesize caffeine,but in C. irrawadiensis, these labelled precursors were incorporatedinto theobromine, not caffeine. No synthesis of purine alkaloidscould be detected in C. japonica and C. sasanqua leaves. Conventional"salvage" and degradation pathways of purines were present inall species of Camellia plants examined. ¹ Present address: Research Center, Mitsubishi Chemical IndustriesLtd., 1000 Kamisida-cho, Midori-ku, Yokohama, 227 Japan. (Received September 29, 1986; Accepted January 22, 1987)     

Complement-Mediated Cytolysis of Cell-Wall Mutants of Chlamydomonas reinhardtii

Treatment of the cell wall-less mutant CW 15 of Chlamydomonasreinhardtii with human serum leads to a marked increase of thecell volume, followed by an irreversible cytolysis. Heat-inactivatedserum as a control reveals no cytotoxic effects on CW 15. Experimentswith C4-, properdin-, C3-, and factor H-depleted sera indicatethe alternative pathway of complement as being responsible forthe serum-mediated lysis. After immunofluorescence marking aswell as electromicroscopically after negative staining the membraneattacking complex of complement, C5b-9, could be demonstratedon the surface of CW 15. These results together with the observationthat cells of the wild-type strain 11-32c of C. reinhardtiiare not lysed by active serum suggest that only protoplastsof Chlamydomonas carry surface structures capable to activatethe alternative pathway of complement. In order to find out whether other cell wall mutants of C. reinhardtii,besides CW 15, can also activate the human complement system,we tested three strains each of the three known mutant categories.Strains CW 4, CW 9, and CW 19, representing category A, andstrains CW 3, CW 10, and CW 92, representing category C, andCW 8 and CW 18, accounting for category B, were cytolysed bynormal human serum. Only one type used in our experiments, CW20 of category B, resisted serum treatment, suggesting the needto redefine this category. ¹This paper is dedicated to Professor Dr. Andr? Pirson on theoccasion of his 80th birthday (Received December 1, 1989; Accepted April 5, 1990)     

Intracellular pH Regulation in an Acidophilic Unicellular Alga, Cyanidium caldarium: 31P-NMR Determination of Intracellular pH

The intracellular pH of an acidophilic unicellular alga, Cyanidiumcaldarium, was determined as a function of external pH by ³¹Pnuclear magnetic resonance. The algal cells incubated underaerobic conditions or under anaerobic and illuminated conditionsmaintained the intracellular pH in the range from 6.8 to 7.0even when the external pH was changed from 1.2 to 8.4. Underanaerobic and dark conditions, however, the intracellular pHacidified at the acidic pH region of the external medium. Theacidified intracellular pH reversibly returned to neutral eitheron aeration or illumination. The results indicate that, in Cyanidiumcells growing in extremely acidic environments, an active H⁺efflux (H⁺ pump) which depends on metabolic activity (respirationor photosynthesis) is essential to maintain the intracellularpH at a constant physiological level against the passive H⁺leakage due to the steep pH gradient across the cell membrane. (Received March 19, 1986; Accepted July 17, 1986)     

Mesozooplankton grazing under conditions of extreme eutrophication in Guanabara Bay, Brazil

The objective of the present study was to quantify mesozooplanktongrazing in the eutrophic waters of Guanabara Bay. Mesozooplankton(>200 µm) was dominated by the copepods Acartia lilljeborgi,Acartia tonsa, Parvocalanus crassirostris and Paracalanus furcatus.Dinoflagellates, specifically the species Prorocentrum triestinum,were an important group for mesozooplankton nutrition, beingingested in significant amounts during all experiments. On average,12.3 ± 2.9 P. triestinum cells were ingested copepod^–1min^–1 (other dinoflagellates: 11 ± 8 cells copepod^–1min^–1). Filamentous cyanophyceae and nanoplankton wereingested in one experiment each, but the mesozooplankton communitygenerally preferred dinoflagellates to these groups, which werealways abundant in the water column. Euglenophyceae were notingested, although they dominated in one experiment. Mesozooplanktoningested, on average, only 0.2% of the nano- and microplanktonbiomass per day. The results suggest that grazing was not acontrolling process for the nano- and microplankton communityin the study area. Addition of zoeae larvae of Chasmagnatusgranulata (Decapoda: Brachyura: Grapsidae) in one experimenthad a significant effect on the mortality of adult copepods,probably due to a predator–prey relationship.     

Ion Effluxes during Excitation of Characeae

Ion effluxes during excitation of Chara and Nitellopsis measuredby conductometry method were compared with results obtainedby two other analytical methods, Ag-AgCl method for Cl^–and ion chromatography method for K⁺. In both species, the averageefflux measured by the conductometry method was very close tothose of K⁺ and Cl^–. (Received May 12, 1986; Accepted June 25, 1986)     

Effects of Osmotic Stress, Ionic Stress and IAA on the Cell-Membrane Resistance of Vigna Hypocotyls

The cell-membrane resistance (R_m) of Vigna hypocotyls was examined,and the effects of osmotic stress, ionic stress and IAA on R_mwere investigated. R_m decreased by 64 to 77% under osmotic stressin the presence of absorbable solutes (40 mM sorbitol, 15 mMKC1, 30 mM sucrose; or 40 mM sorbitol, 15 mM KC1, 30 mM sucroseplus 10^–4 M IAA) or under ionic stress (50 mM NaCl or50 mM KC1). R_m was not changed by perfusion with 10^–4M IAA. Therefore, the hyper-polarizations of the membrane potentialobserved in both cases should be ascribed totally to the activationof the electrogenic proton pump. Although R_m showed an increaseof 1.6 fold when the hypocotyls were subjected to osmotic stress(100 mM sorbitol or 100 mM sorbitol plus 10^–4 M IAA),83.6% or 92.4% of the hyperpolarization of the membrane potential(V_px was also the result of the activation of the pump. Theresults, calculated on the basis of the current source model,support the viewpoint that the hyperpolarization of the cellmembrane potential of Vigna hypocotyls under osmotic stress,ionic stress or in the presence of IAA is an expression of theactivation of the proton pump, and is not caused by an increasein R_m. ¹ Present address: Researchers and Planners of Natural Environment, Yotsugi Bldg. (2F), 1-5-4 Horinouchi, Suginami-Ku, Tokyo,166 Japan ² Present address: Graduate School of Integrated Science, YokohamaCity University, 22-2 Seto, Kanazawa-Ku, Yokohama, 236 Japan (Received February 14, 1991; Accepted July 24, 1991)     

Plasma Membrane H+-ATPase in Guard-Cell Protoplasts from Vicia faba L.

The activity of plasma membrane H⁺-ATPase was measured withmembrane fragments of guard-cell protoplasts isolated from Viciafaba L. ATP hydrolytic activity was slightly inhibited by oligomycinand ammonium molybdate, and markedly inhibited by NO₃^–and vanadate. In the presence of oligomycin, ammonium molybdateand NO₃^–, the ATP-hydrolyzing activity was strongly inhibitedby vanadate. It was also inhibited by diethylstilbestrol (DES),p-chloromercuribenzoic acid (PCMB) and Ca²⁺, but slightly stimulatedby carbonyl cyanide m-chlorophenylhydrazone (CCCP). The acitivityhad higher specificity for ATP as a substrate than other phosphoricesters such as ADP, AMP, GTP and p-nitrophenylphosphate; theK_m was 0.5 mM for ATP. The activity required Mg²⁺ but was notaffected by K⁺, and it was maximal around pH 6.8. When guard-cellprotoplasts were used instead of membrane fragments, the ATPaseactivity reached up to 800µmol Pi.(mg Chl)^–1.h^–1in the presence of lysolecithin. These results indicate thatthe guard cell has a high plasma membrane H⁺-ATPase activity. (Received December 23, 1986; Accepted April 28, 1987)     

Modification in Cell Shape Unrelated to Cellulose Microfibril Orientation in Growing Thallus Cells of Chaetomorpha moniligera

Cellulose microfibril orientation patterns in thallus cellsof Chaetomorpha moniligera were studied, and the relationshipbetween the microfibril and the peripheral microtubule arrangementsduring cell-shape modification by colchicine was examined. Inthe cuttings from growing thalli, linearly arranged cylindricalcells developed into cask-shaped cells during 4–6 daysof culture at 27?C. In the cylindrical cells, microfibrils formingthe innermost portion of the wall were arranged alternatelyin longitudinal and transverse directions, but peripheral microtubuleswere always arranged only in a longitudinal direction. Thesefeatures were also noted in the cask-shaped cells. Colchicineat 10^–3M and 3?10^–3M accelerated both cell expansionand wall thickening with matrix deposition, but the directionsin which both microfibrils and microtubules were arranged werethe same as those of the cylindrical cells. These results indicatethat (1) the microfibril and microtubule arrangements of Chaetomorphaare not necessarily correlated, (2) changes in cell shape ofChaetomorpha are not necessarily accompanied by changes in thearrangement of cell-wall microfibrils, and (3) colchicine playsa role in the loosening and thickening of cell walls by enhancingmatrix deposition. (Received June 2, 1986; Accepted February 13, 1987)     

Regulation of Sterol Biosynthesis in Solanum Species

Regulation of sterol synthesis was studied in Solanum species.A significant negative correlation was found between sterolcontent and rate of sterol synthesis from (1-¹⁴C) acetate inplant organs of Solanum nigrum and cell cultures of S. dulcamara.Exogenous cholesterol significantly inhibited the rate of sterolsynthesis from (¹⁴C) acetate in cell cultures of S. dulcamarawithout affecting synthesis from (³H) mevalonate. Exogenouscholesterol stimulated the rate of total lipid synthesis fromboth (¹⁴C) acetate and (³H) mevalonate. Thus, cholesterol inhibitedconversion of acetate to mevalonate; this is taken as evidenceof a negative feedback control on sterol synthesis. Key words: Feedback control, Phytosterol biosynthesis, Plant cell culture, Solanum species     

Intra-Leaf and Intracellular Gradients in Chloroplast Ultrastructure of Dorsiventral Leaves Illuminated from the Adaxial or Abaxial Side during their Development

The number of thylakoids per granum, which is smaller in sun-typechloroplasts than in shade-type chloroplasts, was counted forthe chloroplasts at various positions within the single leavesof Spinacia oleracea L. and Glycine max (L.) Merrill. The thylakoidnumber increased with depth from the adaxial surface, but thistrend was not evident within respective cells. Therefore, photosyntheticproperties of chloroplasts should be similar within a cell butdifferent among cell layers. The similarity within a cell maybe due to the nuclear control of the chloroplast developmentand/or to chloroplast movement along the cell walls. Illumination of the leaves of G. max from the abaxial side duringtheir expansion resulted in the complete inversion of the intra-leafgradient in the thylakoid number, indicating that the formationof the intra-leaf gradient in chloroplast properties is influencedby the intra-leaf light environment during the later phase ofleaf development. ¹presennt address: Department of Environmental Biology, ResearchSchool of Biological Sciences, Australian National University,P.O. Box 475, Canberra, A.C.T. 2601, Australia. (Received March 13, 1986; Accepted May 30, 1986)     

Oxidative Damages and Repair in Euglena gracilis Exposed to Ozone. I. SH Groups and Lipids

Malondialdehyde, a product of lipid oxidation, increased graduallywhen Euglena gracilis cells were bubbled with 240 µ1.liter^–1ozone (delivery rate of 1µmolO₃.min^–1) for 120 min.Simultaneously, the sulfhydryl group content decreased by 36%during the treatment, which was mainly due to oxidation of proteinsulfhydryl groups. The molar amount of SH groups oxidized was3 times higher than that of fatty acid oxidized, indicatingthat sulfhydryl groups were more accessible or more easily oxidizedby O₃ than fatty acids. When Euglena cells were allowed to recoverunder autotrophic growth conditions following O₃ treatment,viable cells were incapable of dividing during the first 5 hof the recovery period but regenerated SH groups nearly to thecontrol level. The increase of SH content during this periodpreceded the resumption of cell division and the restorationof normal growth. These results suggest that the regenerationof SH groups by Euglena cells is a part of a mechanism involvedin the repair of oxidative damage caused by ozone and is anessential step for the initiation of cell division. (Received July 20, 1987; Accepted December 14, 1987)     

Development and fate of Eutreptiella gymnastica bloom in nutrient-enriched enclosures in the coastal Baltic Sea

Response of the phytoplankton community to bottom-up (nutrients,organic carbon source) and top-down (fish) manipulations, bothsingly and together, were studied daily during a 3 week periodin July 1993 by using eight 50 m³ mesocosms in the coastal northernBaltic Sea. Nutrient additions (once per week) invoked a seriesof blooms of Eutreptiella gymnastica Throndsen (Euglenophyceae)(up to 13 x 10³ cells ml^–1) which formed the major part(60–90%) of the total autotrophic biomass. After rapiddepletion of nutrients (2–3 days) from the surface layer(0–6 m) downwards migration and a subsequent peak of E.gymnasticain the lower part of the water columns (6–12 m) followed.Settled material collected from the bottom of the enclosurescontained a considerable amount of E.gymnastica cells and restingcysts. Nevertheless, sinking loss rates of E.gymnastica wereestimated to be less than 1% day^–1 of the suspended cellnumbers. The fate of E.gymnastica blooms was estimated to begrazing through mesozooplankton. However, provided the nutrientsare plentiful in the water column, the growth potential of E.gymnasticaappears to exceed the ambient grazing pressure. If the nutrientsbecome depleted, it seems to be effectively controlled by mesozooplanktongrazing, which is probably limiting the likelihood of massiveE.gymnastica blooms in the coastal Baltic Sea. Our study suggeststhat E.gymnastica appears to be a fast-growing fugitive (bloom)species with flexible behavioural (vertical migration) and lifehistory (cyst formation) adaptations which is able to exertdominant role and direct trophic relations similar to otherbloom species adapted for decaying turbulence and high nutrientenvironments.     

The afternoon depression in primary productivity in a high rate oxidation pond (HROP)

Algae (mainly Euglena sp.) from a high rate oxidation pond (HROP)were used for studying the afternoon depression in primary productivity.The phenomenon was observed on the same date by laboratory measurementsof photosynthesis and respiration (oxygen evolution method)as well as by in situ determinations of ¹⁴C incorporation. Thefollowing values of were calculated: morning, 0.014 µmolO₂/mg Chi a/min//mol quanta.m².s; afternoon, 0.008. Assuminga constant k_c of 0.006 m²/mg Chi a we found the quantum requirement(^–1) in the morning sample to be considerably lower thanin the afternoon sample (surface: morning 44 mol quanta/molO₂; afternoon, 71). Besides this reduction in photosyntheticefficiency the afternoon sample also exhibited reduced lightsaturated photosynthetic rates (P_max) and enhanced dark respirationrates. The combination of these three effects led to considerablylower areal primary productivity in the HROP in the afternoon.We suggest that this phenomenon is brought about by carbon limitationand cell overloading by photosynthetic products.     

Biomass and production of the major dominant crustacean zooplankton in a tropical Rift Valley lake, Awasa, Ethiopia

Seasonal variation of the biomass (B), production (P) and P/Bratio of the numerically dominant crustaceans in Lake Awasa(Mesocydops aequatonalis stmilts, Thermocyclops consunilis andDiaphanosoma exisum) were studied during 1986 and 1987. Quantitativenet samples (64 (xm mesh) were taken at three stations on 10day intervals throughout 1986, and the dry weights and developmenttimes for each life stage were obtained from laboratory measurementsand cultures Total biomass of most of the dominant crustaceans,determined from 390 samples during 1986, was 44.85 mg m^–3(dry weight, DW) with adult females of Mesocyclops making >43.5%.Alona diaphana, another common crustacean, is dealt with ina separate paper, as are the Rotifera. Production of the dominantcrustaceans during 1986 was estimated by the growth incrementsummation (Winberg) and instantaneous growth (Ricker) methodsThe annual integrated production of the two dominant cyclopoidsis 535.2 mg (DW) m^–3 (Winberg) while annual crustaceanproduction totals 2.5 g (DW) m^–3 (Ricker) The mean annualP/B ratio for individual species and stages varied from 221.0for Diaphanosoma, to 121.7-143.0 for nauplii and 9.8–187 for copepodites of the cyclopoids It was 55 8 for the dominantzooplankton species Low or high zooplankton production and biomassturnover rates (P/B) cannot be used to characterize all tropicallakes consistently However, production per unit biomass is likelyto be higher in tropical lakes.     

Transport and Fixation of Inorganic Carbon during Photosynthesis of Anabaena Grown under Ordinary Air. I. Active Species of Inorganic Carbon Utilized for Photosynthesis

Inorganic carbon transport during photosynthesis of cyanobacteriumAnabaena variabilis grown under ordinary air was investigatedby supplying ¹⁴CO₂ or H¹⁴CO₃^– solution to three differentstrains. Both CO₂ and HCO₃^– were accumulated within thealgal cells. In the cell suspension from which dissolved inorganiccarbon had been depleted by pre-illumination, CO₂ was transportedand accumulated faster than HCO₃^–. When the concentrationof HCO₃^– injected into the cell suspension of A. variabilisM3 was 25 times as high as that of CO2 (the expected ratio atequilibrium at pH 7.8), the initial rates of fixation of bothinorganic carbon species were practically the same. On the otherhand, when ¹⁴CO₂ or H¹⁴CO₃^– was added under steady statephotosynthetic conditions, both carbon species were transportedat similar rates. The ratio of fixed to transported carbon measuredafter the initial 5 s was only 23–27% regardless of thecarbon species supplied. This percentage is much lower thanthat reported for Chlorella cells. ¹ To whom reprint requests should be addressed (Received June 30, 1986; Accepted December 16, 1986)