The contribution of phytoplankton productivity in turbid freshwaters to their trophic status

Certain factors influencing phytoplankton productivity are accentuated in turbid waters. They include mixing, spectral quality shifts, scattering, light fluctuations, and overall light attenuation. Measurements of productivity is influenced by the presence of inorganic turbidity. Together with the above factors high turbidity causes difficulties to assess and model phytoplankton productivity. Estimations of ^B, P_m ^B, I_k and _m only reflect on the physiological condition of the phytoplankton, which differs little between water types of temperate regions. Measurement of integral vertical productivity, efficiency and fractional absorption by the phytoplankton of light energy conversion, however, are greatly influenced by inorganic turbidity. Because of high ratios of mixing to euphotic depth, the critical mixing depth is one of the most important factors influencing overall productivity in turbid waters.     

Synthesis of FimH receptor-active manno-oligosaccharides by reverse hydrolysis using α-mannosidases from Penicillium citrinum,Aspergillus phoenicis and almond

Recombinant Penicillium citrinum -1,2-mannosidase, expressed in Aspergillus oryzae, was employed to carry out regioselective synthesis of -d-mannopyranosyl-(12)-d-mannose. Yields (w/w) of 16.68% disaccharide, 3.07% trisaccharide and 0.48% tetrasaccharide were obtained, with 12 linkages present at 98.5% of the total linkages formed. Non-specific -mannosidase from almond was highly efficient in reverse hydrolysis and oligosaccharide yields of 45–50% were achieved. The products of the almond mannosidase were a mixture of disaccharides (30.75%, w/w), trisaccharides (12.26%, w/w) and tetrasaccharides (1.89%, w/w) with 12, 13 and 16 isomers. -1,2-linkage specific mannosidase from P. citrinum and -1,6-linkage-specific mannosidase from Aspergillus phoenicis were used in combination to hydrolyse the respective linkages from the mixture of isomers, resulting in -d-mannopyranosyl-(13)-d-mannose in 86.4% purity. The synthesised oligosaccharides can potentially inhibit the adhesion of pathogens by acting as "decoys" of receptors of type-1 fimbriae carried by enterobacteria.     

Novel Type of Signaling Molecules: Protein Kinases Covalently Linked with Ion Channels

Recently we identified a new class of protein kinases with a novel type of catalytic domain structurally and evolutionarily unrelated to the conventional eukaryotic protein kinases. This new class, which we named alpha-kinases, is represented by eukaryotic elongation factor-2 kinase and the Dictyosteliummyosin heavy chain kinases. Here we cloned, sequenced, and analyzed the tissue distribution of five new putative mammalian -kinases: melanoma -kinase, kidney -kinase, heart -kinase, skeletal muscle -kinase, and lymphocyte -kinase. All five are large proteins of more than 1000 amino acids with an -kinase catalytic domain located in the carboxyterminal part. We expressed the catalytic domain of melanoma -kinase in Escherichia coli, and found that it autophosphorylates at threonine residues, demonstrating that it is a genuine protein kinase. Unexpectedly, we found that long aminoterminal portions of melanoma and kidney -kinases represent new members of the TRP ion channel family, which are thought to mediate the capacitative Ca²⁺entry in nonexcitable mammalian cells. This suggests that melanoma and kidney -kinases, which represent a novel type of signaling molecule, are involved in the regulation of Ca²⁺influx in mammalian cells.     

Amylase activity and growth in internodes of deepwater rice

Isoelectrofocusing, product analysis, thermal denaturation studies and affinity chromatography on cycloheptaamylose-Sephadex were used to identify the amylolytic enzymes in internodes of deepwater rice (Oryza sativa L.). Amylolytic activity in internodes of deepwater rice consists of -amylase (sometimes separated into two isoforms) and of -amylase. During submergence of whole plants, -amylase activity increases in young, growing internodes, but -amylase activity declines. Although non-growing, mature internodes contain higher levels of -amylase than do the elongating younger internodes, the effect of submergence on amylase activities in both tissues follows the same trend. Submergence, gibberellic acid (GA₃) and ethylene all promote -amylase activity in growing and non-growing internodes of excised deepwater-rice stem sections. Inhibitor studies showed that submergence and ethylene promote -amylase activity in the absence of endogenous gibberellin (GA), and GA₃ enhances -amylase activity when ethylene action is inhibited. Therefore, ethylene and GA appear to increase -amylase activity independently of each other. Enhanced -amylase activities are probably responsible for the mobilization of carbohydrates which are needed to support internode elongation during submergence of deepwater rice.Abbreviations CHA cycloheptaamylose - GA₃ gibberellic acid - NBD 2,5-norbornadiene - TCY tetcyclacis     

Degradation stages of the oak forests in the area of Algiers

Long lasting human impact on the natural Mediterranean vegetation is the reason for its degradation. Uncontrolled felling of trees, fire and overgrazing are the most important ecological causes of this process.Geobotanical investigations made in the area of Algiers facilitated the characterization of degradation changes in the structure of vegetation and in the floristic composition in all the degradation stages.Under the influence of the degradation factors, mentioned above, the oak forests, growing on different, more or less calcareous substrates, are transformed into various shrub formations, mainly into many types of maquis and garrigue. The floristic composition of these communities is given in Table 2.Further degradation leads to widespread Cistus-formations and then to palmitto, a formation created by the dwarf palm (Chamaerops humilis).When the anthropopressure becomes stronger even this dwarf palm retreats. Loose swards, replacing the palmitto formation, often cannot stop the subsequent degradation. Bare rock is the extreme, relatively rare stage of forest degradation in this area.The most common form of natural regeneration is the invasion of Pinus halepensis, observed in all degradation stages identified. This pine is also one of trees, most commonly planted on mountain slopes to prevent their erosion.     

1H NMR studies of the mercuric ion binding protein MerP: Sequential assignment,secondary structure and global fold of oxidized MerP

Summary The oxidized form of the mercuric ion binding protein MerP has been studied by two-dimensional NMR. MerP, which is a periplasmic water-soluble protein with 72 amino acids, is involved in the detoxification of mercuric ions in bacteria with resistance against mercury. The mercuric ions in the periplasmic space are first scavenged by the MerP protein, then transported into the cytoplasm by the membrane-bound transport protein MerT, and finally reduced to elementary (nontoxic) mercury by the enzyme mercuric reductase. In this work, the ¹H NMR spectrum of oxidized MerP (closed disulfide bridge) has been assigned by using homonuclear 2D NMR techniques. The secondary structure and global fold have been inferred from the nuclear Overhauser effect (NOE) data. The secondary structure comprises four -strands and two -helices, in the order ₁₁₂₃₂₄. The protein folds into an antiparallel -sheet, ₂₃₁₄, with the two antiparallel helices on one side of the sheet. The folding topology is similar to that of acylphosphatase, the activation domain of porcine pancreatic procarboxypeptidase B, the DNA-binding domain of bovine papillomavirus-1 E2 and the RNA-binding domains of the U1 snRNP A and hnRNP C proteins. However, there is no structural similarity between MerP and other bacterial periplasmic binding proteins.     

Dispersion patterns of phytoplankton in lakes

The spatial distribution of phytoplankton is considered in relation to factors which may cause deviations from a random distribution. Such deviations may arise over a wide range of scales and attention is focused on small-scale contagion and its possible significance. Evidence is presented that contagion may occur at scales smaller than have previously been considered. Samples covering a range of volumes from 0.1 ml to 10 ml were taken from a small lake and total numbers of several phytoplankton species were counted in each sample to avoid problems arising from sub-sampling. The counts were used to calculate different indices of dispersion. All indices indicated contagion to occur at the scale being considered. Within the range examined the patch size appeared variable between species. The possible derivation and relevance of such micro-patchiness is discussed.     

Excretion of ureide and other nitrogenous compounds by the root system of soybean at different growth stages

Direct excretion of nitrogenous compounds into a N-free nutrient solution, which was allowed to drip onto the root system of soybean (Glycine max (L) Merr. cv. Kurosengoku) was examined at different growth stages; vegetative, flowering and pod-filling. Considerable amounts of nitrogenous compounds were excreted at all the growth stages, with the highest amount recorded at the pod-filling stage.The root was found to be the major site of N compound excretion and its dry weight was linearly correlated with N amount excreted. Maximum nitrogen excretion rate during vegetative and flowering stages was recorded during the day, however at the pod-filling stage, the highest was recorded during the night. Ureide was excreted at all growth stages, but the highest amount was recorded at the pod-filing stage. The root was found to be the active site of ureide excretion. Composition of the total nitrogen examined i. e. ureide, soluble proteins, ammonia and amino acids, was found to be changing during the growth stages, suggesting possible different major pathways of excretion at different plant age. Among the N compounds monitored, were soluble proteins, ammonia and amino acids. Only a few of the several amino acids found in the root tissues were observed in the excreted solution, notably phosphoserine and phosphoethanolamine, at all the growth stages, whilst -amino-butyric-acid and serine were observed in trace amounts during vegetative and flowering stages. Quantitatively the ammonia found in the excreted solution was far greater than in the tissues.     

Effects of aquatic macrophytes on water quality and phytoplankton communities in shallow lakes

We investigated aquatic macrophytes, water quality, and phytoplankton biomass and species composition in three shallow lakes with different levels of vegetation cover and nutrient concentration in Kushiro Moor, during August 2000. Trapa japonica can live in a wide range of nutrient levels. This species forms an environment with a steeper extinction of light, higher concentrations of dissolved organic carbon (DOC), lower concentrations of dissolved oxygen (DO) near the bottom, and lower concentrations of nitrate+nitrite and soluble reactive phosphorus (SRP) than other vegetation types. The pH was much higher in a Polygonum amphibium community, and the DO near the bottom did not decrease compared to a T.japonica community in the summer. The relationship between chlorophyll a and the limiting nutrient (total phosphorus (TP) when total nitrogen (TN):TPis 10 and TN/10 when TN:TP is <10) significantly differed between lakes with and without submerged vegetation. The chlorophyll a concentrations at a given nutrient level were significantly lower in water with submerged macrophytes than in water without them. Correspondence analysis showed that the difference in phytoplankton community structure across sites was largely due to the presence or absence of submerged macrophytes, and the ordination of phytoplankton species in the lakes with submerged macrophytes is best explained by environmental gradients of TN, chlorophyll, pH and SRP.     

Zooplankton, phytoplankton and the microbial food web in two turbid and two clearwater shallow lakes in Belgium

Components of the pelagic food web in four eutrophic shallow lakes in two wetland reserves in Belgium (Blankaart and De Maten) were monitored during the course of 1998–1999. In each wetland reserve, a clearwater and a turbid lake were sampled. The two lakes in each wetland reserve had similar nutrient loadings and occurred in close proximity of each other. In accordance with the alternative stable states theory, food web structure differed strongly between the clearwater and turbid lakes. Phytoplankton biomass was higher in the turbid than the clearwater lakes. Whereas chlorophytes dominated the phytoplankton in the turbid lakes, cryptophytes were the most important phytoplankton group in the clearwater lakes. The biomass of microheterotrophs (bacteria, heterotrophic nanoflagellates and ciliates) was higher in the turbid than the clearwater lakes. Biomass and community composition of micro- and macrozooplankton was not clearly related to water clarity. The ratio of macrozooplankton to phytoplankton biomass – an indicator of zooplankton grazing pressure on phytoplankton – was higher in the clearwater when compared to the turbid lakes. The factors potentially regulating water clarity, phytoplankton, microheterotrophs and macrozooplankton are discussed. Implications for the management of these lakes are discussed.     

Linkage mapping of quantitative trait loci controlling seed weight in pea (Pisum sativum L.)

Quantitative trait loci (QTLs) affecting seed weight in pea (Pisum sativum L.) were mapped using two populations, a field-grown F₂ progeny of a cross between two cultivated types (Primo and OSU442-15) and glasshouse-grown single-seed-descent recombinant inbred lines (RILs) from a wide cross between a P. sativum ssp. sativum line (Slow) and a P. sativum ssp. humile accession (JI1794). Linkage maps for these crosses consisted of 199 and 235 markers, respectively. QTLs for seed weight in the Primo x OSU442-15 cross were identified by interval mapping, bulked segregant analysis, and selective genotyping. Four QTLs were identified in this cross, demonstrating linkage to four intervals on three linkage groups. QTLs for seed weight in the JI1794 x Slow cross were identified by single-marker analyses. Linkage were demonstrated to four intervals on three linkage groups plus three unlinked loci. In the two crosses, only one common genomic region was identified as containing seed-weight QTLs. Seed-weight QTLs mapped to the same region of linkage group III in both crosses. Conserved linkage relationships were demonstrated for pea, mungbean (Vigna radiata L.), and cowpea (V. unguiculata L.) genomic regions containing seed-weight QTLs by mapping RFLP loci from the Vigna maps in the Primo x OSU442-15 and JI1794 x Slow crosses.     

Bacterial regeneration of ammonium and phosphate as affected by the carbon:nitrogen:phosphorus ratio of organic substrates

The effect of carbonnitrogenphosphorus (CNP) ratio of organic substrates on the regeneration of ammonium and phosphate was investigated by growing natural assemblages of freshwater bacteria in mineral media supplemented with the simple organic C, N, and P sources (glucose, asparagine, and sodium glycerophosphate, respectively) to give 25 different substrate CNP ratios. Both ammonium and phosphate were regenerated when CN and NP atomic ratios of organic substrates were 101 and 161, respectively. Only ammonium was regenerated when CN and NP ratios were 101 and 10–201, respectively. On the other hand, neither ammonium nor phosphate was regenerated when CN and NP ratios were 151 and 51, respectively. In no case was phosphate alone regenerated. As bacteria were able to alter widely the CNP ratio of their biomass, the growth yield of bacteria appeared primarily dependent on the substrate carbon concentration, irrespective of a wide variation in the substrate CNP ratio.     

Carbon-isotope discrimination by leaves of Flaveria species exhibiting different amounts of C3-and C4-cycle co-function

Carbon-isotope ratios were examined as ¹³C values in several C₃, C₄, and C₃–C₄ Flaveria species, and compared to predicted ¹³C, values generated from theoretical models. The measured ¹³C values were within 4 of those predicted from the models. The models were used to identify factors that contribute to C₃-like ¹³C values in C₃–C₄ species that exhibit considerable C₄-cycle activity. Two of the factors contributing to C₃-like ¹³C values are high CO₂ leakiness from the C₄ pathway and pi/pa values that were higher than C₄ congeners. A marked break occurred in the relationship between the percentage of atmospheric CO₂ assimilated through the C₄ cycle and the ¹³C value. Below 50% C₄-cycle assimialtion there was no significant relationship between the variables, but above 50% the ¹³C values became less negative. These results demonstrate that the level of C₄-cycle expression can increase from, 0 to 50% with little integration of carbon transfer from the C₄ to the C₃ cycle. As expression increaces above 50%, however, increased integration of C₃- and C₄-cycle co-function occurs.Abbreviations and symbols RuBP carboxylase ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) - PEP carboxylase phosphoenolpyruvate carboxylase (EC 4.1.1.31) - pa atmospheric CO₂ partial pressure - pi intercellular CO₂ partial pressure - isotope ratio - quantum yield for CO₂ uptake     

Autotrophic carbon sources for heterotrophic bacterioplankton in a floodplain lake of central Amazon

The relative contribution of autotrophic carbon sources (aquatic macrophytes, flooded forest, phytoplankton) for heterotrophic bacterioplankton was evaluated in a floodplain lake of the Central Amazon. Stable carbon isotopes (¹³C) were used as tracers. Values of ¹³C of different autotrophic sources were compared to those of dissolved organic carbon (DOC) and those of bacterially produced CO₂.The percentage of carbon derived from C₄ macrophytes for bacterially produced CO₂ was the highest, on average 89%. The average ¹³C value of CO₂ from bacterial respiration was –18.5 ± 3.3. Considering a fractionation of CO₂ of 3 by bacterial respiration, ¹³C value was –15.5, near C₄ macrophyte ¹³C value (–13.1).The average value of total DOC ¹³C was –26.8 ± 2.4. The percentage of C₄ macrophytes carbon for total DOC was on average 17%. Considering that bacteria consume mainly carbon from macrophytes, the dominance of C₃ plants for total DOC probably reflects a faster consumption of the former source, rather than a major contribution of the latter source.Heterotrophic bacterioplankton in the floodplain may be an important link in the aquatic food web, transferring the carbon from C₄ macrophytes to the consumers.     

The chemical composition of ‘canjica’, a polymeric material found in Brazilian cane sugar industry

A polymeric water-insoluble material, the so called canjica, was collected in nine Brazilian sugar and alcohol plants. It was found that all the samples were very similar to each other regarding the moisture and variable in ash contents, whereas CHNS analysis showed that they were carbohydrates. Trace amounts of nitrogen and sulphur compounds were also found to be present, and their source were attributed to proteinaceous material from sugarcane juice contaminants. Paper chromatography and gas chromatography-mass spectrometry (GC-MS) analysis showed that the polymers are formed by repeated glucose moieties bond by 1,6-linkages. Infrared spectroscopy revealed a dextran polysaccharide structure, while X-ray fluorescence determined that various other elements (Ca, Al, Fe, K, Cl, Mn, P and traces of Si and Ti) were also associated with the polymer, in amounts that varied considerably from sample to sample. X-ray diffraction analysis confirmed the polysaccharide dextran structure while identifying a certain amount of different (polysaccharide) material present in the canjica.     

Dynamics of carbon assimilation by St Lawrence estuary phytoplankton at the end of summer

This study presents data of in situ measurements of inorganic carbon assimilation by phytoplankton communities of the St Lawrence estuary during the end of summer 1982. We used carboxylase activity measurements (ribulose-1,5-bisphosphate carboxylase, carboxylases) and the ¹³C/¹²C ratio of phytoplankton organic carbon, expressed as ¹³C, to study patterns of assimilation. Upper estuary phytoplankton communities showed a smaller turn-over rate in carbon assimilation than lower estuary phytoplankton communities. Carbon assimilation was limited by light intensity in the upper estuary and by CO₂ availability in the lower estuary. In the St Lawrence estuary, stable carbon isotope ratios of phytoplankton organic carbon seemed to be controlled by inorganic carbon availability rather than by phytoplankton metabolism.     

Correlations between phytoplankton,organic detritus and carbon in North Sea waters during the Fladenground Experiment (FLEX' 76)

Quantitative analysis of phytoplankton, organic detritus and dissolved organic carbon was carried out, during the spring bloom, in a specific North Sea area (58° 55 N, O° 32 E) in the course of an international and multidisciplinary marine investigation (FLEX' 76). An attempt was made to correlate the fluctuations of these variables; the analysis, however, was complicated by massive water movements. A maximum of the phytoplankton bloom coincided with a maximum of organic detritus, while both variables turned out to be inversely correlated with the dissolved organic carbon content. The initial, high amount of dissolved organic carbon declined at a daily rate of ca. 13% during a period of non-interference by water movements. Two thirds of the dissolved organic carbon content are assumed to be transformed into particulate organic matter whilst the rest disappears through still unknown channels.     

A comparison of different methods used for the quantitative evaluation of biomass of freshwater phytoplankton

Although in a strict sense the term phytoplankton biomass only refers to living algal material, in aquatic ecology the term has been associated with a variety of biological and biochemical procedures used to quantify the particulate matter suspended in natural waters. Relative merits of different biomass characteristics have been studied in three Dutch freshwater lakes with great differences in absolute biomass. Parallel determinations have been made of seston dry weight and supplementary elementary and caloric analyses of seston, of chlorophyll-a concentration and supplementary paper chromatographic analyses of pigment extracts, of particle concentration and particle size distribution as studied with an electronic particle counter, and of phytoplankton cell volume as calculated from the results of microscopic enumeration and sizing of algae. In this way an attempt was made to create a detailed picture of the nature of the seston of the three freshwater lakes.Different analytical techniques give strikingly different information, the accuracy of any method is largely dependent on the circumstances present, and different biomass characteristics therefore are only of value in limited spheres. It is suggested to distinguish between total seston characteristics (e.g. seston dry weight, particulate organic carbon, total particle volume) and strictly algological biomass characteristics (e.g. chlorophyll-a concentration, phytoplankton cell volume). The pattern of growth of phytoplankton populations shown by e.g. chlorophyll-a concentration may differ markedly from that indicated by e.g. total particle volume or seston dry weight. Also, to more or less extent the wax and wane of phytoplankton populations may go undetected among the total seston. Apparently, there is no one method of estimating biomass and no conversion factor that may serve for general purposes. In general, unambiguous information on the nature of the seston of natural waters may only be obtained by estimating total seston characteristics and algological biomass characteristics simultaneously. Depending on the objective of the investigation supplementary component analyses should be carried out to guarantee the correct interpretation of the results.     

DNA fragmentation and detachment of enterocytes induced by anti-CD3 mAb-activated intraepithelial lymphocytes

To elucidate the role of intraepithelial lymphocytes (IEL) and enterocytes in the defense mechanism of the small intestine, we designed experiments to stimulate the IEL by anti-CD3, anti-TCR, or anti-TCR monoclonal antibodies (mAbs), and to examine the subsequent changes to the enterocytes. The enterocytes of the duodenum and jejunum, but not of the ileum, showed massive DNA fragmentation 30 min after intraperitoneal injection of anti-CD3 mAb. These responses were also induced by anti-TCR mAb, but not by anti-TCR mAb, and were completely inhibited by cyclosporin A. Nearly half of the enterocytes of the villi in the duodenum and jejunum were exfoliated into the lumen 4 h after the injection of the mAb. Administration of anti-CD3 mAb also induced DNA fragmentation in Fas-deficient MRL/lpr mice, indicating that the Fas-Fas ligand system was not involved in these events. The anti-CD3 mAb treatment also induced massive DNA fragmentation in the intestinal epithelium of the duodenum and jejunum in TNF-receptor-1-deficient mice, whereas TNF- induced only the detachment of intestinal epithelium of wild-type mice, implying the dissociation of two independent factors and/or mechanisms for DNA fragmentation and the subsequent epithelial cell detachment in the murine duodenum and jejunum. The mAb failed to exfoliate the epithelium in TNF-R1-deficient mice. Thus, TCR⁺ IEL, when treated with anti-CD3 or anti-TCR mAbs, induced rapid DNA fragmentation and subsequent detachment of the duodenal and jejunal epithelia, but not in the ileum (the silent ileum), partly because of the paucity of TCR⁺ IELs in the ileum.K. Yaguchi and S. Kayaba contributed equally to this workThis work was in part supported by a Grant-in-aid for Scientific Research from the Ministry of Education, Science and Culture, Japan (07407066, 10470002, and 13670002 to T.I., and 10770001 to H.S.), and by The Funds for Comprehensive Research on Long Term Chronic Diseases from the Ministry of Health and Welfare of Japan (to T.I.)     

Diel periodicity in phytoplankton productivity

Daily variation in phytoplankton productivity influences the dynamics and linkages between several large scale processes in aquatic ecosystems. As part of an opening address to the 5th International workshop for the Group for Aquatic Productivity (GAP), the daily patterns of variability in photosynthesis for different algal classes was introduced and accompanied by a discussion of the sources of environmental and endogenous regulation of repeating biological oscillations that occur in phytoplankton on timescales of one day. It is suggested that one way to develop a database that serves to sort and predict phytoplankton variability over the day may be to encourage the creation of a temporal library. Such a library would be comprised of temporally fixed maps of circadian clock-controlled rhythms for individual species, as well as temporally variable maps of diel periodicities that only can be defined for a selected set of environmental conditions.