Enzymatic transfer of sialic acids modified at C-5 employing four different sialyltransferases

We present kinetic studies on the enzymatic transfer of several synthetic sialic acid analogues, modified at C-5, to distinct glycoprotein glycans by sialytransferases differing in acceptor- and linkage-specificity. Biochemical properties of sialic acids were modified by introducing formyl-, trifluoroacetyl-, benzyloxycarbonyl-, and aminoacetyl-groups to the amino group at C-5 of neuraminic acid. The latter substitution renders the corresponding -glyocoside resistant towards sialidases. The respective CMP-sialic acid analogues were prepared by CMP-sialic acid synthase with a yield of 13–55%.The kinetic parameters of several sialyltransferases for the 5-substituted CMP-glycosides differed significantly. Relative to parent CMP-NeuAc, reaction rates of human- and rat liver Gal1, 4GlcNAc 2,6-sialyl-transferases ranged from 50 to 170%, of GalNAc 2,6-sialyltransferases from 40–140%, and of Gal1,3Gal-NAc 2,3-sialyltransferase from 20–50%. Resialylation of asialo-₁-acid glycoprotein by 5-N-formyl- and 5-N-aminoacetyl-neuraminic acid employing rat liver Gal1,4GlcNAc 2,6-sialyltransferase proceeded to about 80% of galactose sites which is identical to the extent achieved with parent NeuAc.According to our data, neosialoglycoconjugates which carry sialic acids modified at theN-acetyl group can be prepared for structure-function analysis, as this position seems crucial for recognition of adhesion proteins and influenza viruses.     

Characterization of heterochromatin in Schistocerca gregaria by C- and N-banding methods

Mitotic and meiotic chromosomes of Schistocerca gregaria were C-, mild N- and strong N-banded. After C-banding, three out of eleven autosomes show, in addition to the centromeric C-bands, a second C-band. — The mild N-banding method produces a single N-band in each of only four chromosomes. With the exception of one N-band these mild N-bands correspond to the non-centromeric, second C-bands, indicating the heterochromatic character of at least three mild N-band regions. — The strong N-banding technique produces bands both at the C- and mild N-band positions and additionally a third band in one chromosome (M₈), not present after C- or mild N-banding. — The N-bands do not correspond to the nucleolus organizer regions. Because of the mechanisms of the N-banding methods, it is concluded that the centromeric heterochromatin, as well as the non-centromeric N-band regions, contain high quantities of non-histone proteins. Presumably a specific difference exists between the non-histone proteins in the centromeric and non-centromeric N-band regions because the centromeres are banded by the strong N-banding technique, but not after mild N-banding. It is concluded that the N-band regions (two exceptions) contain a heterochromatin type which has the following features in common with the -heterochromatin of Drosophila: C- as well as N-banding positive, high nonhistone protein content, repetitive and late replicating DNA. It is discussed whether the N-banded heterochromatin regions of Schistocerca contain that DNA fraction which is, like the Drosophila -heterochromatin, underreplicated in polyploid nuclei.     

Metadynamics modelling of the solvent effect on primary hydroxyl rotamer equilibria in hexopyranosides

Accurate modelling of rotamer equilibria for the primary hydroxyl groups of monosaccharides continues to be a great challenge of computational glycochemistry. The metadynamics technique was applied to study the conformational free energy surfaces of methyl α-d-glucopyranoside and methyl α-d-galactopyranoside, employing the glycam06 force field. For both molecules, seven to eight conformational free-energy minima, differing in the ω (O-5–C-5–C-6–O-6) and χ (C-3–C-4–O-4–HO-4) dihedral angles, were identified in vacuum or in a water environment. The calculated rotamer equilibrium of the primary hydroxyl group is significantly different in vacuum than in water. The major effect of a water environment is the destabilisation of a hydrogen bond between O-4–HO-4 and O-6–HO-6 groups. It was possible to calculate the free-energy differences of individual rotamers with an accuracy of better than 2 kJ/mol. The calculated gg, gt and tg rotamer populations in water are in close agreement with experimental measurements, and therefore support the theoretical background of metadynamics.     

A protonmotive force as the source of energy for galactoside transport in energy depletedEscherichia Coli

Summary Uracil transport inSaccharomyces cerevisiae is mediated by a specific permease which does not recognize other pyrimidines such as uridine, cytosine, thymine, 2-hydroxypyrimidine or 5-amino-uracil; hypoxanthine and 6-amino-uracil slightly inhibit the uptake of uracil in a strain lacking cytosine permease activity. Wild type cells concentrate extracellular uracil before its transformation into UMP and subsequent incorporation into nucleic acids. A strain lacking UMP pyrophosphorylase and uridine ribohydrolase (strainfur 1–8 rh, in which the endogenous production as well as the utilization of uracil are lacking) is able to concentrate¹⁴C-2 uracil from the medium. At the same time no other¹⁴C-2 labelled compound could be detected in this strain, thus suggesting that the uptake of uracil in yeast occurs by active transport which is not coupled to the UMP pyrophosphorylase. The optimal pH of uracil uptake in standard growth conditions was 4.3. It was deduced from experiments performed on strainfur 1–8 rh with³H-5 and¹⁴C-2 uracil that the intracellular pool of uracil is recycled once the steady-state has been reached. First order kinetics with similar rate constants were observed for uracil efflux in strainfur 1–8 rh (k min^–1=0.75±0.08) as well as in the strain lacking uracil permease,fur 1–8 rh fur 4–6 (k min^–1=0.60±0.08). The intracellular pool of¹⁴C-2 uracil can be chased in strainfur 1–8 rh by addition of³H uracil without inducing a large initial acceleration of the exit rate (the rate constant remained at 0.60). 2-4-dinitrophenol inhibits the uptake of uracil but also reduces the efflux of uracil in strainfur 1–8 rh fur 4–6. These data and the comparison with cytosine transport in the same organism support the hypothesis that, whereas uracil uptake is a permease mediated active transport, the efflux of uracil does not involve the uracil uptake permease. A coefficient of permeability of 7.4×10^–7 cm sec^–1 was calculated for uracil.     

Specificity ofAmaranthus leucocarpus lectin

We have demonstrated thatAmaranthus leucocarpus lectin hemagglutinating activity was powerfully inhibited by the T-antigen, containing Gal(1–3)GalNAc(1–3)Ser/Thr, and the T_n-antigen, which contains GalNAc(1–3)Ser/Thr. This suggests that the acetamido group at C-2 and the axial -OH at C-4 of theN-acetyl-D-galactopyranosylamine ring are important for lectin binding. The hemagglutination assays also established that desialylated and Pronase-treated human typeO erythrocytes with an M phenotype were better recognized than erythrocytes from all other blood groups. The recognition was dependent on pH and ionic strength.     

Biological activity of optically pure C-1 altered abscisic acid analogs in Brassica napus microspore embryos

We have examined the effects of stereochemically pure analogs of abscisic acid (ABA) on three responses in Brassica napus microspore embryos. The analogs used include modifications to natural (S-) (+)-ABA (= N-ABA) at the C-1 and C-1 positions. At the C-1 position, the carboxylic acid function was replaced with an alcohol, aldehyde, or methyl ester functional group, and at the chiral C-1 position both enantiomers were prepared. The rationale for choosing these particular analogs was that they had previously shown some potential as slow release forms of ABA (Gusta LV, Ewan B, Reaney MJT, Abrams SR (1992) Can J Bot. 70:1550–1555). The responsiveness of microspore-derived embryos of B. napus to these analogs was investigated. Three types of responses were evaluated: (1) the inhibition of precocious germination; (2) induction of oleosin gene expression; and (3) induction of napin gene expression. All of the structural analogs of ABA tested were effective in the three assays, regardless of functional group substitution or stereochemistry. However, the three assays showed differential sensitivity to the various analogs. The U-forms of abscisyl alcohol and abscisyl aldehyde were very effective in inhibiting precocious germination (greater than natural ABA). Oleosin mRNA accumulation responded most effectively to U-abscisyl alcohol, while the N-abscisyl aldehyde and ABA methyl ester were the most effective at inducing napin mRNA accumulation. This work highlights the distinct differences in activity which result from using stereochemically pure analogs. In addition, surprisingly potent responses are reported in one or more of the assays for abscisyl aldehyde and abscisyl alcohol.Abbreviations ABA abscisic acid - LEA late embryogenic abundant - HPLC high performance liquid chromatography - MOPS 4-morpholinepropanesulfonic acid - SDS sodium dodecyl sulfate     

Relationship between biosynthesis of carotenoids and increasing complexity of photosystem I in mutant C-6D of Scenedesmus obtiquus

Dark-grown cells of the pigment mutant C-6D of Scenedesmus obliquus, strain D₃ (Gaffron 1939), contain only chlorophyll (Chl) a and carotenoid precursors. In these cells a functioning photosystem I (PSI) of basic structure was characterised by a high PSI activity and a low Chl/P700 ratio. The reaction-center complex of PSI (CPI) was shown to exist in the dark-grown cells. These findings demonstrate that the assembly of the core complex of PSI and its function are independent of the presence of carotenoids. Upon illumination, carotenoids, Ch1 b and additional Chl a were synthesized. Newly formed -carotene was shown by pigment analysis using high-performance liquid chromatography (HPLC) to be incorporated into CPI. Parallel to this process a shift of the long-wavelength fluorescence emission of PSI from 712–714 to 718–719 nm was observed. In the later stages of chloroplast differentiation, when xanthophylls and Chl b were synthesized, a higher-molecular-weight complex of PSI (CPIa) could be isolated. Pigment analysis demonstrated that CPIa contained xanthophylls and Chl b in addition to Chl a and -carotene. This indicates the formation of a light-harvesting antenna closely associated with PSI (LHCI). The addition of an LHCI to the reaction-center complex of PSI caused an increase in the absorption cross-section of PSI as shown by action spectroscopy and in-vivo fluorescence measurements. A model demonstrating the changes in the molecular organization of PSI during light-induced carotenoid biosynthesis in mutant C-6D of Scenedesmus obliquus is presented.Abbreviations Chl chlorophyll - CP chlorophyll-protein complex - LHC light-harvesting complex - HPLC high-performance liquid chromatography - PSI, II photosystem I, II - PAGE polyacrylamide gel electrophoresis This work was supported by the Deutsche Forschungsgemeinschaft and a scholarship of the Studienstiftung des deutschen Volkes to S. Römer. We thank Ms. K. Bölte for technical assistance and Mr. H. Becker for drafting the figures.     

Characterization and molecular cloning of a novel endoglucanase from Trichoderma sp. C-4

A fungal strain, C-4, was isolated from etiolated leaves. Based on taxonomic studies, the fungus C-4 can be classified as a strain of Trichoderma species. When strain C-4 was cultured in Mandels medium at 28°C for 6 days, the enzyme activities detected in the broth corresponded to 8.2 U/ml (28.1 U/mg) carboxymethylcellulase activity. An endoglucanase (EG; F-I-II) was purified from the culture filtrate of the strain through a four-step procedure—chromatography on Sephacryl S-200, DEAE-Sephadex A-50, Con A-Sepharose, and Chromatofocusing on Mono-P (HPLC). The molecular weight of this EG, which was called C4endoII, was determined to be about 51 kDa. The optimum temperature and pH of C4endoII were 50°C and 5.0, respectively. Incubation at 50°C for 24 h did not destroy the cellulose degradation activity. Amino acid sequence analysis revealed the N-terminal sequence of an internal peptide of C4endoII to be Phe-Ala-Gly-Ile-Asn-Ile-Ala-Gly-Phe-Asp-Phe, which is homologous to EGII from Trichoderma reesei. A C4endoII cDNA (C4endoII) was cloned from a cDNA library constructed using the mRNA of the strain cultivated in a cellulase-induction medium. The deduced protein sequence of C4endoII was 417 amino acids long and had a putative signal sequence of 21 amino acids with a predicted cleavage site after Ala-21. A single potential N-glycosylation site was present in the amino acid sequence.     

Biochemical composition of three algal species proposed as food for captive freshwater mussels

To identify potential diets for rearing captive freshwater mussels, the protein, carbohydrate (CHO), and lipid contents of two green algae, Neochloris oleoabundans, Bracteacoccus grandis, and one diatom, Phaeodactylum tricornutum, were compared at different growth stages. The fatty acid and sterol composition were also identified. Protein was greatest (55–70%) for all species at late log growth stage (LL), and declined in late stationary (LS) growth. CHO was greatest at LS stage for all species (33.9–56.4% dry wt). No significant change in lipid levels occurred with growth stage, but tended to increase in N. oleoabundans. Mean lipid content differed significantly in the order: N. oleoabundans > P. tricornutum > B. grandis. Total fatty acids (TFA) were higher at LS stage compared to other stages in the two green algae, and stationary stage in the diatom. Mean unsaturated fatty acids (UFA) as %TFA was significantly higher in N. oleoabundans than the other species. The green algae contained high percentages of C-18 polyunsaturated fatty acids (PUFAs), while the diatom was abundant in C-16 saturated and mono-unsaturated fatty acids and C-20 PUFA fatty acids. Growth stage had no effect on sterol concentration of any species. B. grandis showed significantly higher sterol levels than the other species except P. tricornutum at S stage. B. grandis was characterized by predominantly ⁵, C-29 sterols, while N. oleoabundans synthesized ^5,7, ^5,7,22 , and ⁷, C-28 sterols. P. tricornutum produced primarily a ^5,22, C-28 sterol, and a small amount of a ^7,22, C-28 sterol.     

Poly-cis carotene pathway in the Scenedesmus mutant C-6D

The mutation of Scenedesmus obliquus strain C-6D is expressed in the dark only. Under these conditions, this strain synthesizes acyclic poly-cis carotenes. Cyclic carotenoids like -carotene or xanthophylls are absent. In the light the normal cyclic carotenes and xanthophylls are synthesized in the all-trans configuration. The poly-cis carotencs present in dark cultures have been analysed and quantitated. It could be shown that these poly-cis carotenes are identical with the poly-cis carotenes synthesized by the tomato mutant Lycopersicon esculentum var. Tangella. The poly-cis pathways, however, are different regulated in the two organisms. The tomato mutant accumulates prolycopene as the major carotene, whereas the mutant C-6D accumulates mainly pro--carotene. Furthermore, the mutation in Tangella is constitutive in light in contrast to Scenedesmus C-6D. Besides that, Scenedesmus C-6D synthesizes a further cis-carotene isomer of phytofluene as well as of -carotene. The configuration of these carotenes still have to be elucidated. The occurrence of this poly-cis carotene biosynthetic pathway by a mutation of only one enzyme, the phytoene desaturase which, however, is only expressed in darkness under heterotrophic conditions, is discussed.     

The use of hydrophobic synthetic glycosides as acceptors in glycosyltransferase assays

A general method is described for the assay of glycosyltransferase activity, which makes use of synthetic glycoside acceptors attached to hydrophobic aglycones. The products formed by incubation of an enzyme with acceptor and radiolabelled sugarnucleotide can then be rapidly (one minute) separated from interfering radioactivity by adsorption on to reverse-phase C-18 cartridges. After aqueous washing, products are easily isolated by elution with methanol. The utility of the method for the assay of (1–4)galactosyltransferase, (1–2)fucosyltransferase andN-acetylglucosaminyltransferase I and V is demonstrated.     

Five new species of coccidia (Apicomplexa: Eimeriidae) from Madagascan chameleons (Sauria: Chamaeleonidae)

Coprological examination of 19 Madagascan chameleons of the genera Furcifer and Brookesia revealed the presence of five new coccidian species. Isospora brygooi n. sp. from Furcifer pardalis has spherical to subspherical oöcysts with a slightly pitted wall, 20.7 (17–24.5) × 19.3 (16–23) m and broadly ellipsoidal sporocysts, 12.2 (11.5–13) × 8.1 (8–8.5) m, with Stieda and substieda bodies. Oöcysts of Eimeria glawi n. sp. from Furcifer pardalis are cylindrical to ellipsoidal, 27.7 (26–29.5) × 18.4 (17–19) m, with ellipsoidal sporocysts, 7.3 (6.5–8) × 5.2 (5–5.5) m. E. vencesi n. sp. described from F. pardalis has spherical to subspherical oöcysts, 14.3 (13–15.5) × 13.0 (12–13) m, with small granules, one to three globular polar granules and ellipsoidal sporocysts, 7.3 (6.5–8) × 5.2 (5–5.5) m. E. worthi n. sp., described from Furcifer oustaleti has spherical oöcysts, 17.9 (17.5–19.0) × 15.0 (14.5–16.0) m without a polar granule and ellipsoidal to cylindroidal sporocysts, 8.2 (7.0–9.5) × 5.8 (5.0–6.5) m. Oöcysts of E. brookesiae n. sp. from Brookesia decaryi are cylindrical, 25.6 (23–27) × 15.0 (13–16) m with ellipsoidal sporocysts, 10.1 (9–11) × 6.9 (6–7) m. Endogenous development of E. vencesi is confined to the intestine, while that of E. glawi occurs in the gall-bladder.     

The endogenous development of three new intranuclear species of Isospora (Apicomplexa: Eimeriidae) from agamid lizards

Three new species of Isospora Schneider, 1881 are described from agamid lizards, Isospora cannoni n. sp. in Diporiphora australis from northern Queensland, Australia, I. choochotei n. sp. in Calotes mystaceus from northern Thailand, and I. deserti n. sp. in Agama pallida from Israel. I. cannoni oöcysts are subspherical, 20–25 × 22.5–27.5 m with two ovoid sporocysts, 14–15.5 × 10–11.5 m. I. choochotei oöcysts are spherical to subspherical, 24–32 × 28–32.5 m with two ovoid sporocysts, 11 × 15.5–18 m. I. deserti oöcysts are spherical, 25–28 m in diameter with two ovoid sporocysts, 10–11 × 14–17.5 m. All species had sporocysts with Stieda bodies and underwent endogenous development in the nucleus of the host gut epithelial cells. At completion of merogony and gamogony, the host nucleus was reduced to a thin envelope. The significance of endogenous stage characteristics in Isospora taxonomy is discussed.     

Saccharide binding to three Gal/GalNAc specific lectins: Fluorescence,spectroscopic and stopped-flow kinetic studies

Fluorescence and stopped-flow spectrophotometric studies on three plant lectins fromPsophocarpus tetragonolobus (winged bean),Glycine max (soybean) andArtocarpus integrifolia (jack fruit) have been studied usingN-dansylgalactosamine as a fluorescent ligand. The best monosaccharide for the winged bean agglutinin I (WBA I) and soybean (SBA) is Me-GalNAc and for jack fruit agglutinin (JFA) is Me-Gal. Examination of the percentage enhancement and association constants (1.51×10⁶, 6.56×10⁶ and 4.17×10⁵ M^–1 for SBA, WBA I and JFA, respectively) suggests that the combining regions of the lectins SBA and WBA I are apolar whereas that of JFA is polar. Thermodynamic parameters obtained for the binding of several monosaccharides to these lectins are enthalpically favourable. The binding of monosaccharides to these lectins suggests that the-OH groups at C-1, C-2, C-4 and C-6 in thed-galactose configuration are important loci for interaction with these lectins. An important finding is that the JFA binds specifically to Galß1-3GaINAc with much higher affinity than the other disaccharides which are structurally and topographically similar.The results of stopped-flow spectrometry on the binding ofN-dansylgalactosamine to these lectins are consistent with a bimolecular single step mechanism. The association rate constants (2.4×10⁵, 1.3×10⁴, and 11.7×10⁵ M^–1 sec^–1 for SBA, WBA I and JFA, respectively) obtained are several orders of magnitude slower than the ones expected for diffusion controlled reactions. The dissociation rate constants (0.2, 3.2×10^–2, 83.3 sec^–1 for SBA, WBA I and JFA, respectively) obtained for the dissociation ofN-dansylgalactosamine from its lectin complex are slowest for SBA and WBA I when compared with any other lectin-ligand dissociation process.Abbreviations SBA Soybean agglutinin - WBA I Winged bean agglutinin (Basic) - JFA Jack fruit agglutinin - PNA Peanut agglutinin - Con A Concanavalin A - Dansyl (Dns) 5-dimethylaminonaphthalene-I-sulphonyl - 2GaINDns N-dansylgalactosamine - dGal 2-deoxygalactose - l-Ara l-arabinose - d-Fuc d-fucose - l-Rha l-rhamnose - N-acetyllactosamine Galß4GlcNAc - melibiose Gal6Glc     

The Effects of Hypoxia on Three Sympatric Shark Species: Physiological and Behavioral Responses

Behavioral and physiological responses to hypoxia were examined in three sympatric species of sharks: bonnethead shark Sphyrna tiburo, blacknose shark, Carcharhinus acronotus, and Florida smoothhound shark, Mustelus norrisi, using closed system respirometry. Sharks were exposed to normoxic and three levels of hypoxic conditions. Under normoxic conditions (5.5–6.4mg l^–1), shark routine swimming speed averaged 25.5 and 31.0cm s^–1 for obligate ram-ventilating S. tiburo and C. acronotus respectively, and 25.0cm s^–1 for buccal-ventilating M. norrisi. Routine oxygen consumption averaged about 234.6 mg O₂kg^–1h^–1 for S. tiburo, 437.2mg O₂kg^–1h^–1 for C. acronotus, and 161.4mg O₂ kg^–1 h^–1 for M. norrisi. For ram-ventilating sharks, mouth gape averaged 1.0cm whereas M. norrisi gillbeats averaged 56.0 beats min^–1. Swimming speeds, mouth gape, and oxygen consumption rate of S. tiburo and C. acronotus increased to a maximum of 37–39cm s^–1, 2.5–3.0cm and 496 and 599mg O₂ kg^–1 h^–1 under hypoxic conditions (2.5–3.4mg l^–1), respectively. M. norrisi decreased swimming speeds to 16cm s^–1 and oxygen consumption rate remained similar. Results support the hypothesis that obligate ram-ventilating sharks respond to hypoxia by increasing swimming speed and mouth gape while buccal-ventilating smoothhound sharks reduce activity.     

Function and regulation of the avian caecal bulb: influence of dietary NaCl and aldosterone on water and electrolyte fluxes in the hen (Gallus domesticus) perfused in vivo

Summary The function of the caecal bulb, and its adaptation to chronic high- or low-Na⁺ intake, was investigated by in vivo perfusion of anaesthetised birds. Effects of acute aldosterone injection (125 g·kg^–1 body mass) were also measured.Evidence was found for primary active net absorption of Na⁺, inducing parallel Na-linked absorption of water and Cl^– and secretion of K⁺. Around 20–35% of total Cl^– absorption and K⁺ secretion were independent of Na⁺ fluxes, and these components appear to be driven by passive processes with apparent conductances of 6.3×10^–3 (G _Cl) and 1.1×10^–3 (G _K) S·cm^–2.Acetate (40mM) stimulated Na⁺ fluxes (8.5–9.9 Eq·cm^–2·h^–1) and Na-linked water fluxes (27–44 l·cm^–2·h^–1). Increased coupling ratios (2.9–4.6 l·Eq^–1) and other data indicate that these effects may be due to increased osmotic permeabilities of barriers involved in the Na-linked water transfer pathway.Low-Na⁺ maintenance enhanced EPD (49–69 mV, serosa positive) and all net fluxes:J _Na (6.8–11.6);J _K (–3.2––4.3);J _Cl (4.3–5.6 Eq·cm serosal area^–2·h^–1);J _v (28–43 l·cm^–2·h^–1) (mucosal-serosal fluxes positive).Acute aldosterone enhancedJ _Na (10.8–14.0 Eq·cm^–2·h^–1) and EPD (54–66 mV) by 3 h after injection, but had no effect on the Na-linked components ofJ _K orJ _Cl.Abbreviations ECPD, EPD Electrochemical or electrical potential difference - G _Cl ,G _K ionic conductances (Cl^–, K⁺) - J _v ,J _ion net volume or ion flux rate, mucosa-serosa positive;P _d (Cl) diffusive permeability coefficient (of Cl^–) - SEDM standard error of difference between means     

Feeding rate inhibition in crowded Daphnia pulex

Feeding rates of Daphnia pulex fed a range of levels of the alga Chlamydomonas reinhardi of 15 °C are strongly density-dependent. At lower densities, Daphnia (30 1^–1) fed at higher rates than crowded (270 1^–1) Daphnia which manifest a relatively depressed saturation feeding response. At 30 individuals/liter, Daphnia consumed 8.5 – 15.7 × 10⁴ cells d^–1h^–1 (on a volume basis, 12.1 – 22.2 × 10⁶ m³), at 270 L^–1 3.7 – 3.9 × 10⁴ (5.2 – 5.5 = 10⁶ m³ cells d^–1h^–1 when feeding on algae at 80 000 cells ml^–1 (11.3 × 10⁶ m³ ml^–1). The feeding rate data best fit an Ivlev feeding function. An autoallelopath might be causing the repression. Water preconditioned with crowded Daphnia completely repressed feeding in uncrowded Daphnia after six hours.     

Sequential kinetic parameter estimation of anaerobic fluidized bed bioreactor using an optimization technique

Mathematical model parameters for the methanogenic degradation of propylene glycol were estimated in a sequential manner by means of an optimization technique. Model parameters determined from an initial experimental data set using one bioreactor were then verified with the results from a second bioreactor. The proposed methodology is a useful tool to obtain model parameters for continuous flow reactors with completely mixed regime. Abbrevations: S – substrate concentration (mg COD l^–1); S _in – influent substrate concentration (mg COD l^–1); D _L – dilution rate (day^–1); – stoichiometric coefficients (ND); nx – number of microbial species (ND); X _S – fixed biomass concentration (mg biomass l^–1); X _L – suspended biomass concentration of (mg biomass l^–1); k _d – decay rate of biomass (day^–1); b _S – specific detachment rate of biofilm (day^–1); – specific growth rate of biomass (day^–1); _m – maximum specific growth rate of biomass (day^–1); K _S – half saturation constant (mg COD l^–1); K _I – inhibition constant (mg COD l^–1).     

Description of the oöcysts of three new species of coccidia (Apicomplexa: Eimeriidae) from lizards in Namibia

Three new species of coccidian were recovered from the intestinal contents and faeces of lizards in Namibia, southwest Africa. Oöcysts of Eimeria barnardi n. sp. are described from Rhoptropus barnardi (Gekkonidae) and are ellipsoidal, 24.3 × 19.9 (21–26.5 × 16–22) m; shape index (length/width) 1.22 (1.12–1.30). A micropyle and oöcyst residuum are absent but a fragmented polar granule is present. Sporocysts are subspherical, 9.2 × 8.3 (8–11 × 7.5–9) m; shape index 1.11 (1.02–1.27). Oöcysts of Eimeria pachybibroni n. sp. were found in Pachydactylus bibroni (Gekkonidae) and are ellipsoidal, 26.2 × 18.2 (21.5–28 × 16–19) m; shape index 1.44 (1.30–1.52). A micropyle and oöcyst residuum are absent but a polar granule is present. Sporocysts are subspherical, 8.9 × 8.0 (8–9.5 × 7–8.5) m; shape index 1.12 (1.03–1.20). Oöcysts of Isospora spilogaster n. sp. are reported from Mabuya spilogaster (Scincidae) and are subspherical, 27.4 × 26.0 (21.5–35 × 21–35) m; shape index 1.05 (1.00–1.13). Micropyle, oöcyst residuum and polar granules are absent. Sporocysts are ellipsoidal, 13.2 × 9.7 (10.5–15 × 9–11) m; shape index 1.36 (1.08–1.50).