Bottom-up controls on a mixed-species HAB assemblage: A comparison of sympatric Chattonella subsalsa and Heterosigma akashiwo (Raphidophyceae) isolates from the Delaware Inland Bays, USA

Recent novel mixed blooms of several species of toxic raphidophytes have caused fish kills and raised health concerns in the highly eutrophic Inland Bays of Delaware, USA. The factors that control their growth and dominance are not clear, including how these multi-species HAB events can persist without competitive exclusion occurring. We compared and contrasted the relative environmental niches of sympatric Chattonella subsalsa and Heterosigma akashiwo isolates from the bays using classic Monod-type experiments. C. subsalsa grew over a temperature range from 10 to 30 °C and a salinity range of 5–30 psu, with optimal growth occurring from 20 to 30 °C and 15 to 25 psu. H. akashiwo had similar upper temperature and salinity tolerances but also lower limits, with growth occurring from 4 to 30 °C and 5 to 30 psu and optimal growth between 16 and 30 °C and 10 and 30 psu. These culture results were confirmed by field observations of bloom occurrences in the Inland Bays. Maximum nutrient-saturated growth rates (μ_max) for C. subsalsa were 0.6 d⁻¹ and half-saturation concentrations for growth (K_s) were 9 μM for nitrate, 1.5 μM for ammonium, and 0.8 μM for phosphate. μ_max of H. akashiwo (0.7 d⁻¹) was slightly higher than C. subsalsa, but K_s values were nearly an order of magnitude lower at 0.3 μM for nitrate, 0.3 μM for ammonium, and 0.2 μM for phosphate. H. akashiwo is able to grow on urea but C. subsalsa cannot, while both can use glutamic acid. Cell yield experiments at environmentally relevant levels suggested an apparent preference by C. subsalsa for ammonium as a nitrogen source, while H. akashiwo produced more biomass on nitrate. Light intensity affected both species similarly, with the same growth responses for each over a range from 100 to 600 μmol photons m⁻² s⁻¹. Factors not examined here may allow C. subsalsa to persist during multi-species blooms in the bays, despite being competitively inferior to H. akashiwo under most conditions of nutrient availability, temperature, and salinity.     

Foreign exploration for Scirtothrips perseae Nakahara (Thysanoptera: Thripidae) and associated natural enemies on avocado (Persea americana Miller)

Scirtothrips perseae Nakahara was discovered attacking avocados in California, USA, in 1996. Host plant surveys in California indicated that S. perseae has a highly restricted host range with larvae being found only on avocados, while adults were collected from 11 different plant species. As part of a management program for this pest, a “classical” biological control program was initiated and foreign exploration was conducted to delineate the home range of S. perseae, to survey for associated natural enemies and inventory other species of phytophagous thrips on avocados grown in Mexico, Guatemala, Costa Rica, the Dominican Republic, Trinidad, and Brazil. Foreign exploration efforts indicate that S. perseae occurs on avocados grown at high altitudes (>1500 m) from Uruapan in Mexico south to areas around Guatemala City in Guatemala. In Costa Rica, S. perseae is replaced by an undescribed congener as the dominant phytophagous thrips on avocados grown at high altitudes (>1300 m). No species of Scirtothrips were found on avocados in the Dominican Republic, Trinidad, or Brazil. In total, 2136 phytophagous thrips were collected and identified, representing over 47 identified species from at least 19 genera. The significance of these species records is discussed. Of collected material 4% were potential thrips biological control agents. Natural enemies were dominated by six genera of predatory thrips (Aeolothrips, Aleurodothrips, Franklinothrips, Leptothrips, Scolothrips, and Karnyothrips). One genus each of parasitoid (Ceranisus) and predatory mite (Balaustium) were found. Based on the results of our sampling techniques, prospects for the importation of thrips natural enemies for use in a “classical” biological control program in California against S. perseae are not promising.     

Decomposition of four macrophytes in wetland sediments: Organic matter and nutrient decay and associated benthic processes

Decomposition rates of Phragmites australis, Carex riparia, Nuphar luteum and Salvinia natans and benthic processes were measured from December 2003 to December 2004 in a shallow wetland (Paludi di Ostiglia, Northern Italy) by means of litter bags and intact cores incubations. Decay rate was highest for N. luteum (k = 0.0152 d⁻¹), intermediate for S. natans (k = 0.0041 d⁻¹) and similar for P. australis (k = 0.0027 d⁻¹) and C. riparia (k = 0.0028 d⁻¹).Benthic metabolism followed a seasonal pattern with summer peaks of O₂ demand and TCO₂, CH₄ and NH₄⁺ efflux whilst soluble reactive phosphorus (SRP) fluxes were negligible also under hypoxic conditions, indicating that P was mainly retained by sediment. The initial C:P ratio was similar in N. luteum and S. natans (170) and significantly lower than that of P. australis and C. riparia (360). During the detritus decay P was progressively lost by N. luteum and S. natans tissues, whereas, after an initial leaching, it was probably re-used during the microbial decomposition of the more refractory P. australis and C. riparia detritus. Nuphar luteum, P. australis and S. natans had comparable initial C:N mass ratio (15), significantly lower than that of C. riparia (26). The C:N ratio was rather constant for N. luteum (12.9 ± 1.5) and S. natans (14.6 ± 0.9), decreased slightly to below 20 for C. riparia and increased up to 30 for P. australis. Overall, differences among species were likely due to the recalcitrance of decomposing detritus, whilst process rates were controlled by limitation of microbial processes by nutrients and electron acceptor availability.     

The effect of host size on the sex ratio of Syngaster lepidus, a parasitoid of Eucalyptus longhorned borers (Phoracantha spp.)

The solitary larval ectoparasitoid, Syngaster lepidus Brullé, parasitizes the cryptic larvae of two wood-boring beetles, Phoracantha recurva Newman and Phoracantha semipunctata F. The objective of this study was to determine how the female parasitoids allocated the sex of progeny when presented with larval hosts of uniform size classes. Host size was directly correlated with age of the Phoracantha larval hosts. Groups of Phoracantha larvae of a single age class (2-, 3-, 4-, or 5-week-old) were exposed to parasitoids, and sex ratios of the resulting parasitoid progeny from each host age class were determined. A significant relationship was observed among the sizes of P. recurva and P. semipunctata hosts and the sex ratio of emerging parasitoids. Parasitized 2-week-old beetle larvae of both Phoracantha spp. produced only male S. lepidus progeny, whereas older larval hosts produced increasing proportions of female parasitoids (up to 80% females from 5-week-old hosts). Two-week-old Phoracantha larvae of both species produced fewer parasitoids than host larvae 3–5-week-old. The size of parasitoid progeny consistently increased with host larval age (size), and female parasitoids were larger than males across all host size classes. Male S. lepidus developed in approximately 25 days from 2-week-old hosts, and 19–21 days in 3–5-week-old hosts. Female S. lepidus developed in 22–25 days, with developmental time increasing with host size.     

Historical biogeography, phylogenetic relationships and intraspecific diversity of agamid lizards in the Central Asian deserts of Kazakhstan and Uzbekistan

The Central Asian agamid lizards are ecologically and morphologically diverse, occurring across a broad range of desert environments in this biogeographically important region. It is probable that past climatic shifts have significantly influenced the diversification patterns and distributions of the agamid lizards of this region. To assess this within a phylogenetic framework we sequenced a 1200 bp region of mitochondrial DNA and a 1200 bp nuclear gene (RAG-1), incorporating both inter- and intraspecific sampling across Central Asian agamids. Our topology and divergence time estimates support an Eocene origin of the Agaminae subfamily on the Indian subcontinent, coinciding with the collision of India into Eurasia. The onset of aridification in Central Asia during the Late Oligocene, resulting from the retreat of the Paratethys Sea and the intensified uplift of the Tibetan–Himalayan complex, probably played an important role in the diversification of Phrynocephalus, one of the three genera studied. Intensification of aridity and geologic events in the Plio-Pleistocene and Quaternary glacial cycling probably had a significant influence on intraspecific diversification patterns within Phrynocephalus.     

Influence of culture temperature on the growth,biochemical composition and fatty acid profiles of six Antarctic microalgae

The growth, biochemical composition and fatty acid profiles of six Antarctic microalgae cultured at different temperatures, ranging from 4, 6, 9, 14, 20 to 30 ^∘C, were compared. The algae were isolated from seawater, freshwater, soil and snow samples collected during our recent expeditions to Casey, Antarctica, and are currently deposited in the University of Malaya Algae Culture Collection (UMACC). The algae chosen for the study were Chlamydomonas UMACC 229, Chlorella UMACC 234, Chlorella UMACC 237, Klebsormidium UMACC 227, Navicula UMACC 231 and Stichococcus UMACC 238. All the isolates could grow at temperatures up to 20 ^∘C; three isolates, namely Navicula UMACC 231 and the two Chlorella isolates (UMACC 234 and UMACC 237) grew even at 30 ^∘C. Both Chlorella UMACC 234 and Stichococcus UMACC 238 had broad optimal temperatures for growth, ranging from 6 to 20 ^∘C (μ = 0.19 – 0.22 day^–1) and 4 to 14 ^∘C (μ = 0.13 – 0.16 day^–1), respectively. In contrast, optimal growth temperatures for NaviculaUMACC 231 and Chlamydomonas UMACC 229 were 4 ^∘C (μ = 0.34 day^–1) and 6–9 ^∘C (μ = 0.39 – 0.40 day^–1), respectively. The protein content of the Antarctic algae was markedly affected by culture temperature. All except Navicula UMACC 231 and Stichococcus UMACC 238 contained higher amount of proteins when grown at low temperatures (6–9 ^∘C). The percentage of PUFA, especially 20:5 in Navicula UMACC 231 decreased with increasing culture temperature. However, the percentages of unsaturated fatty acids did not show consistent trend with culture temperature for the other algae studied.     

Nitrogen source effects on the growth and toxicity of two strains of the ciguatera-causing dinoflagellate Gambierdiscus toxicus

Two Caribbean strains (1651 and 1655) of the ciguatera-causing dinoflagellate Gambierdiscus toxicus were grown in xenic, batch culture under defined, measured nutrient conditions with nitrate, ammonium, urea, a mix of free amino acids (FAA), or putrescine as the nitrogen source. Cultures were maintained at 27 °C, salinity 35, 110 μmol m⁻² s⁻¹ (12 h:12 h light:dark cycle) on L2 medium at an initial nitrogen concentration of 50 μM N. Toxicity was determined using a ouabain/veratridine-dependent cytotoxicity assay (N2A assay) standardized to a ciguatoxin standard. Nitrate, ammonium, FAA, and putrescine supported growth, but urea did not. The appearance of ammonium in the organic nitrogen cultures indicated that G. toxicus and/or associated bacteria remineralized the available organic nitrogen. Both strains were exposed to nitrogen-limiting conditions as evidenced by chlorophyll a content per cell, nitrogen content, and nitrogen (N) to phosphorus (P) (N:P) ratio significantly declining once nitrogen was no longer available in the medium and cells entered stationary phase. Strain 1651 grew significantly faster than strain 1655 when nitrate, FAA, and putrescine was the nitrogen source, but not ammonium. Nitrogen source had no effect on growth rate (0.14 d⁻¹) in strain 1651. The growth rate of strain 1655 (0.10–0.13 d⁻¹) was significantly faster on ammonium than the other nitrogen sources. Strain 1655 was significantly more toxic (10-fold) than strain 1651 except when growing on ammonium at exponential phase. Toxicity ranged from 1.3 to 8.7 fg C-CTX1-Eq cell⁻¹ in strain 1651 and from 30.7 to 54.3 fg C-CTX1-Eq cell⁻¹ in strain 1655. Nitrogen source had no significant affect on toxicity. Toxicity was greater in stationary versus exponential phase cells for strain 1651 when grown on nitrate and strain 1655 regardless of nitrogen source. The difference in toxicity between growth phases may result from an increase in ciguatoxin and/or maitotoxin. Our results suggest that some strains of G. toxicus when associated with bacteria are able to take advantage of organic as well as inorganic nitrogen sources on short time scales to support future growth. The uncoupling of total nitrogen and phosphorus pools from conditions in the water column suggest that instantaneous growth rates can be supported by nutrients acquired hours to days earlier.     

Morphology and infraciliature of Holosticha bradburyae nov. spec. (Ciliophora,Hypotrichida) from the Yellow Sea,China

The living morphology and infraciliature of a new marine hypotrichous ciliate, Holosticha bradburyae nov. spec., collected from the coastal water off Qingdao (Tsingtao), China, are investigated. This species is characterized by: body size 150–320 × 25–75 m with brownish to dark brown cell colour, ca. 53 adoral membranelles and 1 anteriorly positioned buccal cirrus; 3 frontal, 2 frontoterminal and 20–26 transverse cirri; midventral rows comprising 27-32 pairs of cirri; one conspicuous gap always present between anterior and posterior parts of AZM, and 2–5 distinctly elongated membranelles are always present at the posteriormost end; cortical granules conspicuous, round and flattened with central depression, arranged in about 10 lines on dorsal side; 28–33 irregularly arranged macronuclear nodules; 9–11 complete dorsal kineties; caudal cirri absent.     

Gas exchange of Ginkgo biloba leaves at different CO2 concentration levels

One and a half year-old Ginkgo saplings were grown for 2 years in 7 litre pots with medium fertile soil at ambient air CO₂ concentration and at 700 μmol mol⁻¹ CO₂ in temperature and humidity-controlled cabinets standing in the field. In the middle of the 2nd season of CO₂ enrichment, CO₂ exchange and transpiration in response to CO₂ concentration was measured with a mini-cuvette system. In addition, the same measurements were conducted in the crown of one 60-year-old tree in the field. Number of leaves/tree was enhanced by elevated CO₂ and specific leaf area decreased significantly.CO₂ compensation points were reached at 75–84 μmol mol⁻¹ CO₂. Gas exchange of Ginkgo saplings reacted more intensively upon CO₂ than those of the adult Ginkgo. On an average, stomatal conductance decreased by 30% as CO₂ concentration increased from 30 to 1000 μmol mol⁻¹ CO₂. Water use efficiency of net photosynthesis was positively correlated with CO₂ concentration levels. Saturation of net photosynthesis and lowest level of stomatal conductance was reached by the leaves of Ginkgo saplings at >1000 μmol mol⁻¹ CO₂. Acclimation of leaf net CO₂ assimilation to the elevated CO₂ concentration at growth occurred after 2 years of exposure. Maximum of net CO₂ assimilation was 56% higher at ambient air CO₂ concentration than at 700 μmol mol⁻¹ CO₂.     

Lichen-like colonies of pure Trentepohlia on limestone monuments

Biofilms were collected on discoloured limestone samples and on adhesive tape from historic buildings at the Mayan site of Edzna, in Campeche, Mexico. Grey, brown, and black areas were colonised predominantly by coccoid and colonial cyanobacteria, also detected as endoliths. The major biomass on the pink stone surface was Trentepohlia. At low power, surface micropits containing crustose-lichen-like black colonies were seen within these pink areas. These were apparently pure colonies of T. umbrina; no filamentous fungi were detected here. The black colour was produced by dense, amorphous pigment deposits in the colony centres. Insolation levels were high (400 μmphotons m⁻² s⁻¹) and the moisture content of the stone was 0.7%. The high carotenoid:chlorophyll-α ratio of Trentepohlia biofilms (3.9:1) is an adaptation protecting against environmental stress. Trentepohlia caused severe local erosion (pitting) and, when present as a more uniform biofilm, the well-known pink surface discoloration.     

The differential effect of Eriobotrya japonica hydrophilic leaf extract on cytokines production and modulation

Stimulating or modulating the release of cytokines by immunomodulators or immunostimulating agents is an attractive mode for treating several diseases such as viral infections. For instance, patients with viral infections may be in need of increasing or inducing T helper 1 (Th1) or proinflammatory cytokines, which ultimately activate T cytotoxic and Natural killer lymphocytes to kill virally infected cells. Of these agents, we found that Eriobotrya japonica hydrophilic leaf extract (EJHE) can induce and modulate cytokines in dose-dependent manner. Twenty-four hour exposure of increasing concentrations of EJHE increased significantly (p < 0.001) the production of IFN-γ and TNF-α, from PHA+LPS-stimulated whole blood. However, the production of IFN-γ and TNF-α plateaued at high EJHE concentrations (10–100 μg/ml). No significant changes in the production of IL-10 were seen. In addition, EJHE at 1 and 10 μg/ml reversed significantly (p < 0.01) the inhibitory effect of hydrocortisone on the IL-12 p70, IFN-γ and TNF-α production from PHAS+LPS stimulated whole blood. Without PHA and LPS, EJHE was found to induce significantly (p < 0.001) IFN-γ, IL-12 p70, TNF-α, and IL-10 from whole blood culture in concentration dependent manner. The maximum induction of IFN-γ, IL-12 p70, and TNF-α by EJHE was at 1 and 10 μg/ml. On the other hand, IL-10 induction kept increasing even at the highest concentration used (100 μg/ml) of EJHE. Furthermore, intra-peritoneal injection of EJHE into mice increased significantly serum cytokines level mainly at 10 and 100 μg/ml. Two-hour post i.p. injection, EJHE increased serum IFN-γ, TNF-α, and IL-10 to 750, 1000, and 250 pg/ml, respectively. However, 24 h post i.p. injection, the levels of TNF-α, and IL-10 were similar to basal levels but IFN-γ levels were 200 pg/ml. These results indicate that EJHE induces proinflammatory and Th1 cytokines in concentration dependent manner and the effect of this induction should be studied further in viral models to check the efficacy of such cytokine induction.     

Purification and characterization of a novel ribosome-inactivating protein from seeds of Trichosanthes kirilowii Maxim

A novel ribosome-inactivating protein, designated Trichosanthrip, was purified from mature seeds of Trichosanthes kirilowii Maxim by cation-exchange and gel-filtration chromatography. Trichosanthrip migrated as a single band in SDS–PAGE, with an apparent molecular mass of 13 kDa. The molecular mass of Trichosanthrip was 10,964.617 Da as determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Trichosanthrip showed N-glycosidase activity on 28 S rRNA and strongly inhibited cell-free protein synthesis, with an IC₅₀ of 1.6 ng/ml. Liquid chromatography–tandem mass spectrometry showed that Trichosanthrip was a novel protein with similar sequence to other proteins present in members of the Cucurbitaceae.     

Structural elucidation of an exopolysaccharide from mycelial fermentation of a Tolypocladium sp. fungus isolated from wild Cordyceps sinensis

A novel polysaccharide designated EPS-1A with an average molecular weight around 40 kDa was fractionated and purified by anion-exchange and gel-filtration chromatography from the crude exopolysaccharide (EPS) isolated from fermentation broth of Cs-HK1, a Tolypocladium sp. fungus isolated from wild Cordyceps sinensis. The structural characteristics of EPS-1A were determined with various methods (e.g. GC, GC–MS, FT-IR, ¹H NMR and ¹³C NMR) and through acid hydrolysis, methylation, periodate-oxidation and Smith degradation. The results suggested that EPS-1A was composed of glucose, mannose and galactose at 15.2:3.6:1.0 M ratio. EPS-1A was a slightly branched polysaccharide and its backbone was composed of (1 → 6)-α-d-glucose residues (77%) and (1 → 6)-α-d-mannose residues (23%). Branching occurred at O-3 position of (1 → 6)-α-d-mannose residues of the backbone with (1 → 6)-α-d-mannose residues and (1 → 6)-α-d-glucose residues, and terminated with β-d-galactose residues.     

Kinetics of ammonium, nitrate and phosphorus uptake by Canna indica and Schoenoplectus validus

Canna indica L. is an upright perennial rhizomatous herb, and Schoenoplectus validus (Vahl) A. Löve and D. Löve is a tall, perennial, herbaceous sedge. The nutrient uptake kinetics of C. indica and S. validus were investigated using the modified depletion method after plants were grown for 4 weeks in simulated secondary-treated wastewater. The maximum uptake rate (I_max) and Michaelis–Menten constant (K_m) were estimated by iterative curve fitting. The I_max for NH₄N (623 μmol g⁻¹ dry root weight h⁻¹) was significantly higher than that for NO₃N (338 μmol g⁻¹ dry root weight h⁻¹) in S. validus. In contrast, no difference was observed in C. indica. The I_max values for NO₃N and NH₄N were higher in S. validus than in C. indica. A significantly lower K_m was detected for NO₃N uptake in C. indica (385 μmol L⁻¹) compared to that in S. validus (1908 μmol L⁻¹). The I_max for PO₄P did not differ between the plant species. The K_m for PO₄P was significantly higher in C. indica (157 μmol L⁻¹) than in S. validus (60 μmol L⁻¹). In conclusion, we found that S. validus preferred NH₄N over NO₃N, had greater capacity for N uptake and higher affinity for PO₄P, but C. indica had greater affinity for NO₃N. Nutrient uptake capacity is likely related to habitat preference, and is influenced by the structure of roots and rhizomes.     

Fine structure characterization of amylopectins from grain amaranth starch

The aim of this study was to determine the fine structure of amylopectin from grain amaranth. Amaranthus amylopectin was hydrolyzed with α-amylase, and single clusters and a group of clusters (domain) were isolated by methanol precipitation. The domain and the clusters were treated with phosphorylase a and then β-amylase to remove all external chains, whereby the internal structure was obtained. The ,β-limit dextrins were analyzed on Sepharose CL 6B. The average DP (degree of polymerization) and peak-DP values of fractions of clusters were 57 and 82, respectively; the values of the domain were 137 and 309, respectively. The unit chain length profiles were analyzed by high-performance anion-exchange chromatography with pulsed amperometric detector (HPAEC–PAD). The results showed that the domain fraction contained 2.2 clusters, and single clusters were composed of 13 chains. The ,β-limit dextrins of the clusters were further hydrolyzed with α-amylase to characterize their building block composition. The average DP of the branched blocks was 11 and they contained on average 2.5 chains. Their average chain length, internal chain length, and degree of branching were approximately 4.3, 2.8, and 14, respectively. A cluster consisted of 6 branched blocks, and the internal chain length between the blocks was 6.8.     

Molecular cloning of a multidomain cysteine protease and protease inhibitor precursor gene from the tobacco hornworm (Manduca sexta) and functional expression of the cathepsin F-like cysteine protease domain

A Manduca sexta (tobacco hornworm) cysteine protease inhibitor, MsCPI, purified from larval hemolymph has an apparent molecular mass of 11.5 kDa, whereas the size of the mRNA is very large (9 kilobases). MsCPI cDNA consists of a 9,273 nucleotides that encode a polypeptide of 2,676 amino acids, which includes nine tandemly repeated MsCPI domains, four cystatin-like domains and one procathepsin F-like domain. The procathepsin F-like domain protein was expressed in Escherichia coli and processed to its active mature form by incubation with pepsin. The mature enzyme hydrolyzed Z-Leu–Arg–MCA, Z-Phe–Arg–MCA and Boc–Val–Leu–Lys–MCA rapidly, whereas hydrolysis of Suc–Leu–Tyr–MCA and Z-Arg–Arg–MCA was very slow. The protease was strongly inhibited by MsCPI, egg-white cystatin and sunflower cystatin with K_i values in the nanomolar range. When the MsCPI tandem protein linked to two MsCPI domains was treated with proteases, it was degraded by the cathepsin F-like protease. However, tryptic digestion converted the MsCPI tandem protein to an active inhibitory form. These data support the hypothesis that the mature MsCPI protein is produced from the MsCPI precursor protein by trypsin-like proteases. The resulting mature MsCPI protein probably plays a role in the regulation of the activity of endogenous cysteine proteases.     

Spread and persistence of a rugulosin-producing endophyte in Picea glauca seedlings

We have studied Picea glauca (white spruce) endophyte colonization and its affect on the growth of Choristoneura fumiferana (spruce budworm). Here we examine the spread and persistence of a rugulosin-producing endophyte and rugulosin in needles from trees maintained in the nursery, as well as in trees planted in a test field site. Additionally, we report toxicity of rugulosin against three P. glauca needle herbivores: C. fumiferana, Lambdina fiscellaria (hemlock looper) and Zeiraphera canadensis (spruce budmoth). Reduction in body weight for both the C. fumiferana and L. fiscellaria were observed at 25 and 50 μm, respectively, and head capsules were reduced at 100 and 150 μm. Z. canadensis larvae did not perform as well in tests due to an Aspergillus fumigatus infection, but were shown to be lighter when tested with 100 and 150 μm compared with controls. The endophyte and its toxin were shown to spread throughout the nursery-grown seedlings. After 3.5 and 4.5 y post-inoculation (one and two years in the test site), the inoculated endophyte and its toxin had remained present with an average rugulosin concentration of 1 μg g⁻¹.     

Ecophysiological characterization of carnivorous plant roots: Oxygen fluxes,respiration, and water exudation

Various ecophysiological investigations on carnivorous plants in wet soils are presented. Radial oxygen loss from roots of Droseraceae to an anoxic medium was relatively low 0.02 – 0.07 mol(O₂) m^{– 2} s^–1 in the apical zone, while values of about one order of magnitude greater were found in both Sarracenia rubra roots and Genlisea violacea traps. Aerobic respiration rates were in the range of 1.6 – 5.6 mol kg^–1 (f.m.) s^–1 for apical root segments of seven carnivorous plant species and 0.4 – 1.1 mol kg^–1 (f.m.) s^–1 for Genlisea traps. The rate of anaerobic fermentation in roots of two Drosera species was only 5 – 14 % of the aerobic respiration. Neither 0.2 mM NaN₃ nor 0.5 mM KCN influenced respiration rate of roots and traps. In all species, the proportion of cyanide-resistant respiration was high and amounted to 65 – 89 % of the total value. Mean rates of water exudation from excised roots of 12 species ranged between 0.4 – 336 mm 3 kg^–1 (f.m.) s^–1 with the highest values being found in the Droseraceae. Exudation from roots was insensitive to respiration inhibitors. No significant difference was found between exudation rates from roots growing in situ in anoxic soil and those kept in an aerated aquatic medium. Carnivorous plant roots appear to be physiologically very active and well adapted to endure permanent soil anoxia.     

Evaluation of antiprotozoal and antimycobacterial activities of the resin glycosides and the other metabolites of Scrophularia cryptophila

Resin glycosides are secondary metabolites exclusive to the convolvulaceous plants. In this study, crypthophilic acids A–C (1–3), the first resin glycosides occurring in another family (Scrophulariaceae), and the other constituents of Scrophularia cryptophila were examined for in vitro antiprotozoal and antimycobacterial potentials. Except for crypthophilic acid B (2), all tested compounds exhibited growth-inhibitory effect against Trypanosoma brucei rhodesiense, with l-tryptophan (6) and buddlejasaponin III (7) being the most potent ones (IC₅₀'s 4.1 and 9.7 μg/ml). In contrast, the activity towards Trypanosoma cruzi was poor, and only crypthophilic acid C (3), 6 and 7 were trypanocidal at concentrations above 40 μg/ml. With the exception of 2 and 6, all compounds were active against Leishmania donovani. Harpagide (4) and 3 emerged as the best leishmanicidal agents (IC₅₀'s 2.0 and 5.8 μg/ml). Only compounds 3, 6 and 7 showed antimalarial activity against Plasmodium falciparum with IC₅₀ values of 4.2, 16.6 and 22.4 μg/ml. Overall the best and broadest spectrum activity was presented by compounds 3 and 7, as they inhibited all four parasitic protozoa. None of the isolates had significant activity against Mycobacterium tuberculosis (MICs >100 μg/ml) or were toxic towards mammalian (L6) cells. This is the first report of antiprotozoal activity for natural resin glycosides, as well as for harpagide (4), acetylharpagide (5), tryptophan (6) and buddlejasaponin III (7).     

Effects of amino acids on methionine-sulfoximine-induced heterocyst formation in Anabaena

Heterocyst development in ammonia-grown cultures of Anabaena variabilis and Anabaena 7120 was fully induced by the amino-acid analog methionine sulfoximine (MSO) at concentrations of 0.5–1.0 M. Glutamine, glutamate, aspartate, and alanine at 0.5 mM blocked the induction of heterocysts by MSO in A. variabilis. With Anabaena 7120, glutamine and glutamate were fully effective and alanine partially effective in preventing MSO-induced heterocyst formation. In MSO-treated algae, glutamine synthetase activity was reduced to less than 15% of control values within 4–6 h. Inactivation of the enzyme was prevented by all four amino acids tested.