Small-scale turbulence affects the division rate and morphology of two red-tide dinoflagellates

The effects of small-scale turbulence on two species of dinoflagellates were examined in cultures where the turbulent forces came randomly from all directions and were intermittent both spatially and temporally; much like small-scale turbulence in the ocean. With Lingulodinium polyedrum (Stein) Dodge (syn. Gonyaulax polyedra), division rate increased linearly (from 0.35 to 0.5 per day) and the mean cross-sectional area (CSA) decreased linearly (from 1100 to 750 μm²) as a function of the logarithmic increase in turbulence energy dissipation rate (). These effects were noted when values increased between 10⁻⁸ and 10⁻⁴ m² s⁻³. However, when increased to 10⁻³ m² s⁻³, division rate sharply decreased and mean CSA increased. Over the same range of , Alexandrium catenella (Wheedon and Kofoid) Balech had its division rate decrease linearly (from 0.6 to 0.45 per day) and its CSA increase linearly (from 560 to 650 μm²) as a function of the logarithmic increase in . Even at the highest examined (10⁻³ m² s⁻³), which may be unrealistically high for their ambits, both L. polyedra and A. catenella still had fairly high division rates, 0.2 and 0.45 per day, respectively. Turbulence strongly affected chain formation in A. catenella. In non-turbulent cultures, the mode was single cells (80–90% of the population), but at of 10⁻⁵ to 10⁻⁴ m² s⁻³, the mode was 8 cells per chain. At the highest (10⁻³ m² s⁻³), the mode decreased to 4 cells per chain. The vertical distributions of A. catenella populations in relation to hydrographic flow fields were studied in the summers of 1997 and 1998 in East Sound, Washington, USA (latitude 48°39′N, 122°53′W). In both summers, high concentrations of A. catenella were found as a subsurface bloom in a narrow depth interval (2 m), where both current shear and turbulence intensity were at a minimum. Other researchers have shown that A. catenella orients its swimming in shear flows, and that swimming speed increases with chain length. These responses, when combined with our observations, support a hypothesis that A. catenella actively concentrates at depths with low turbulence and shear.     

Nitrogen utilization by the raphidophyte Heterosigma akashiwo: Growth and uptake kinetics in laboratory cultures

The nitrogen uptake and growth capabilities of the potentially harmful, raphidophycean flagellate Heterosigma akashiwo (Hada) Sournia were examined in unialgal batch cultures (strain CCMP 1912). Growth rates as a function of three nitrogen substrates (ammonium, nitrate and urea) were determined at saturating and sub-saturating photosynthetic photon flux densities (PPFDs). At saturating PPFD (110 μE m⁻² s⁻¹), the growth rate of H. akashiwo was slightly greater for cells grown on NH₄⁺ (0.89 d⁻¹) compared to cells grown on NO₃⁻ or urea, which had identical growth rates (0.82 d⁻¹). At sub-saturating PPFD (40 μE m⁻² s⁻¹), both urea- and NH₄⁺-grown cells grew faster than NO₃⁻-grown cells (0.61, 0.57 and 0.46 d⁻¹, respectively). The N uptake kinetic parameters were investigated using exponentially growing batch cultures of H. akashiwo and the ¹⁵N-tracer technique. Maximum specific uptake rates (V_max) for unialgal cultures grown at 15 °C and saturating PPFD (110 μE m⁻² s⁻¹) were 28.0, 18.0 and 2.89 × 10⁻³ h⁻¹ for NH₄⁺, NO₃⁻ and urea, respectively. The traditional measure of nutrient affinity—the half saturation constants (K_s) were similar for NH₄⁺ and NO₃⁻ (1.44 and 1.47 μg-at N L⁻¹), but substantially lower for urea (0.42 μg-at N L⁻¹). Whereas the α parameter (α = V_max/K_s), which is considered a more robust indicator for substrate affinity when substrate concentrations are low (<K_s), were 19.4, 12.2 and 6.88 × 10⁻³ h⁻¹/(μg-at N L⁻¹) for NH₄⁺, NO₃⁻ and urea, respectively. These laboratory results demonstrate that at both saturating and sub-saturating N concentrations, N uptake preference follows the order: NH₄⁺ > NO₃⁻ > urea, and suggests that natural blooms of H. akashiwo may be initiated or maintained by any of the three nitrogen substrates examined.     

Laccase-catalyzed oxidation of phenolic compounds in organic media

Rhus vernificera laccase-catalyzed oxidation of phenolic compounds, i.e., (+)-catechin, (−)-epicatechin and catechol, was carried out in selected organic solvents to search for the favorable reaction medium. The investigation on reaction parameters showed that optimal laccase activity was obtained in hexane at 30 °C, pH 7.75 for the oxidation of (+)-catechin as well as for (−)-epicatechin, and in toluene at 35 °C, pH 7.25 for the oxidation of catechol. E_a and Q₁₀ values of the biocatalysis in the reaction media of the larger log p solvents like isooctane and hexane were relatively higher than those in the reaction media of lower log p solvents like toluene and dichloromethane. Maximum laccase activity in the organic media was found with 6.5% of buffer as co-solvent. A wider range of 0–28 μg protein/ml in hexane than that of 0–16.7 μg protein/ml in aqueous medium was observed for the linear increasing conversion of (+)-catechin. The kinetic studies revealed that in the presence of isooctane, hexane, toluene and dichloromethane, the K_m values were 0.77, 0.97, 0.53 and 2.9 mmol/L for the substrate of (+)-catechin; 0.43, 0.34, 0.14 and 3.4 mmol/L for (−)-epicatechin; 2.9, 1.8, 0.61 and 1.1 mmol/L for catechol, respectively, while the corresponding V_max values were 2.1 × 10⁻², 2.3 × 10⁻², 0.65 × 10⁻² and 0.71 × 10⁻² δA/μg protein min); 1.8 × 10⁻², 0.88 × 10⁻², 0.19 × 10⁻² and 1.0 × 10⁻² δA/μg protein min); 0.48 × 10⁻², 0.59 × 10⁻², 0.67 × 10⁻² and 0.54 × 10⁻² δA/μg protein min), respectively. FT-IR indicated the formation of probable dimer from (+)-catechin in organic solvent. These results suggest that this laccase has higher catalytic oxidation capacity of phenolic compounds in suitable organic media and favorite oligomers could be obtained.     

Nitrogenous preference of toxigenic Pseudo-nitzschia australis (Bacillariophyceae) from field and laboratory experiments

Field and laboratory experiments were designed to determine the differential growth and toxin response to inorganic and organic nitrogen additions in Pseudo-nitzschia spp. Nitrogen enrichments of 50 μM nitrate (KNO₃), 10 μM ammonium (NH₄Cl), 20 μM urea and a control (no addition) were carried out in separate carboys with seawater collected from the mouth of the San Francisco Bay (Bolinas Bay), an area characterized by high concentrations of macronutrients and iron. All treatments showed significant increases in biomass, with chlorophyll a peaking on days 4–5 for all treatments except urea, which maintained exponential growth through the termination of the experiment. Pseudo-nitzschia australis Frenguelli abundance was 10³ cells l⁻¹ at the start of the experiment and increased by an order of magnitude by day 2. Particulate domoic acid (pDA) was initially low but detectable (0.15 μg l⁻¹), and increased throughout exponential and stationary phases across all treatments. At the termination of the experiment, the urea treatment produced more than double the amount of pDA (9.39 μg l⁻¹) than that produced by the nitrate treatment (4.26 μg l⁻¹) and triple that of the control and ammonium treatments (1.36 μg l⁻¹ and 2.64 μg l⁻¹, respectively). The mean specific growth rates, calculated from increases in chlorophyll a and from cellular abundance of P. australis, were statistically similar across all treatments.These field results confirmed laboratory experiments conducted with a P. australis strain isolated from Monterey Bay, CA (isolate AU221-a) grown in artificial seawater enriched with 50 μM nitrate, 50 μM ammonium or 25 μM of urea as the sole nitrogen source. The exponential growth rate of P. australis was significantly slower for cells grown on urea (ca. 0.5 day⁻¹) compared to the cells grown on either nitrate or ammonium (ca. 0.9 day⁻¹). However the urea-grown cells produced more particulate and dissolved domoic acid (DA) than the ammonium- or nitrate-grown cells. The field and laboratory experiments demonstrate that P. australis is able to grow effectively on urea as the primary source of nitrogen and produced more pDA when grown on urea in both natural assemblages and unialgal cultures. These results suggest that the influence of urea from coastal runoff may prove to be more important in the development or maintenance of toxic blooms than previously thought, and that the source of nitrogen may be a determining factor in the relative toxicity of west coast blooms of P. australis.     

ATP increases chemoattractant induced cyclic GMP accumulation in Dictyostelium discoideum

Changes in guanosine cyclic 3′,5′-monophosphate associated with adenosine cyclic 3′,5′-monophosphate and folic acid addition in the presence of ATP have been examined in Dictyostelium discoideum. Preincubation with 1 mM ATP had no effect on the basal cyclic GMP level but increased the cycli GMP accumulation in response to cylci AMP (5·10⁻⁸ M) or folic acid (5·10⁻⁶ M) 40–50%. ATP could not be replaced by ADP of 5′-adenylyliminodiphosphate. Because ATP has no effect on cyclic AMP receptor binding these results indicate that structural membrane alterations (e.g. membrane phosphorylation) may control the transduction of a chemotactic signal.     

Red tide blooms of Cochlodinium polykrikoides in a coastal cove

Successive blooms of the dinoflagellate Cochlodinium polykrikoides occurred in Pettaquamscutt Cove, RI, persisting from September through December 1980 and again from April through October 1981. Cell densities varied from <100 cells L⁻¹ at the onset of the bloom and reached a maximum density exceeding 3.4 × 10⁶ cells L⁻¹ during the summer of 1981. The bloom was mainly restricted to the mid to inner region of this shallow cove with greatest concentrations localized in surface waters of the southwestern region during summer/fall periods of both years. Highly motile cells consisting of single, double and multiple cell zooids were found as chains of 4 and 8 cells restricted to the late August/September periods. The highest cell densities occurred during periods when annual temperatures were between 19 and 28 °C and salinities between 25 and 30. A major nutrient source for the cove was Crying Brook, located at the innermost region at the head of the cove. Inorganic nitrogen (NH₃ and NO₂ + NO₃) from the brook was continually detectable throughout the study with maximum values of 57.5 and 82.5 μmol L⁻¹, respectively. Phosphate (PO₄-P) was always present in the source waters and rarely <0.5 μmol L⁻¹; silicate always exceeded 30 μmol L⁻¹ with maximum concentrations reaching 226 μmol L⁻¹. Chlorophyll a and ATP concentrations during the blooms varied directly with cell densities. Maximum Chl a levels were 218 mg m⁻³ and ATP-carbon was >20 g C m⁻³. Primary production by the dinoflagellate-dominated community during the bloom varied between 4.3 and 0.07 g C m⁻³ d⁻¹. Percent carbon turnover calculated from primary production values and ATP-carbon varied from 6 to 129% d⁻¹. The dinoflagellates dominated the entire summer period; other flagellates and diatoms were present in lesser amounts. A combination of low washout rate due to the cove dynamics, active growth, and life cycles involving cysts allowed C. polykrikoides to maintain recurrent bloom populations in this area.     

Enhancement of taxane production in hairy root culture of Taxus x media var. Hicksii

This study assessed the effect of two precursors (l-phenylalanine and p-amino benzoic acid) used alone or in combination with methyl jasmonate, on the growth and accumulation of paclitaxel, baccatin III and 10-deacetylbaccatin III in hairy root cultures of Taxus x media var. Hicksii. The greatest increase in dry biomass was observed after 4 weeks of culturing hairy roots in medium supplemented with 1 μM of l-phenylalanine (6.2 g L⁻¹). Addition of 1 μM of l-phenylalanine to the medium also resulted in the greatest 10-deacetylbaccatin III accumulation (422.7 μg L⁻¹), which was not detected in the untreated control culture. Supplementation with 100 μM of l-phenylalanine together with 100 μM of methyl jasmonate resulted in the enhancement of paclitaxel production from 40.3 μg L⁻¹ (control untreated culture) to 568.2 μg L⁻¹, the highest paclitaxel content detected in the study. The effect of p-amino benzoic acid on taxane production was less pronounced, and the highest yield of paclitaxel (221.8 μg L⁻¹) was observed when the medium was supplemented with 100 μM of the precursor in combination with methyl jasmonate.Baccatin III was not detected under the conditions used in this experiment and the investigated taxanes were not excreted into the medium.     

Growth of dinoflagellates, Ceratium furca and Ceratium fusus in Sagami Bay, Japan: The role of temperature, light intensity and photoperiod

Seasonal changes of field populations and growth rates of two dinoflagellates, Ceratium furca and Ceratium fusus, were examined in the temperate coastal water of Sagami Bay, Japan. Weekly field sampling was conducted from August 2002 to August 2003, and laboratory experiments were also carried out to investigate effects of temperature, irradiance and photoperiod on the growth rates of these two Ceratium species. In the field, the abundances of both species increased significantly from April to August 2003, were gradually decreased from November 2002 and were not observed in January 2003. C. fusus was able to increase at lower temperatures in February 2003 compared to C. furca. In the laboratory, the two species did not grow at <10 °C or >32 °C. The highest specific growth rate of C. furca was 0.72 d⁻¹ at 24 °C and 600 μmol m⁻² s⁻¹. Optimum growth rates (>0.4 d⁻¹) of C. furca were observed at temperatures from 18 to 28 °C and at irradiances from 216 to 796 μmol m⁻² s⁻¹. The highest growth rate of C. fusus was 0.56 d⁻¹ at 26 °C and 216 μmol m⁻² s⁻¹. Optimum growth rates of C. fusus were observed at the same irradiance rage of C. furca, whereas optimum temperature range was narrower (26–28 °C). The growth curves of both species indicated saturation of the growth rates when light intensity was above 216 μmol m⁻² s⁻¹, and did not show photoinhibition at irradiances up to 796 μmol m⁻² s⁻¹. The specific growth rates of both Ceratium species were clearly decreased at L:D = 10:14 relative to those at L:D = 14:10 and L:D = 12:12. The present study indicates the two Ceratium species can adapt to a wide range of temperature and irradiance.     

Response of cylindrospermopsin production and release in Aphanizomenon flos-aquae (Cyanobacteria) to varying light and temperature conditions

The influence of light and temperature on the cylindrospermopsin (CYN) production of two Aphanizomenon flos-aquae strains, isolated from North-eastern German lakes, was investigated with semi-continuously growing cultures. A light gradient from 10 to 60 μE m⁻² s⁻¹ in combination with temperatures of 16, 20, and 25 °C was tested.CYN concentrations varied by a maximum factor of 2.7 in strain 10E9 with a significant decrease with increasing temperature. Strain 22D11 showed less pronounced changes, i.e. by a factor of 1.6, and without clear relationship to temperature.Reaction patterns of CYN production to changing light intensities are different at different temperatures. In both strains CYN concentrations increase significantly at 20 °C between 10 and 60 μE m⁻² s⁻¹, whereas they decrease significantly at 25 °C in the same light gradient. The amount of synthesised CYN is not reflected by growth rates of the strains in a uniform manner. Nonetheless several temperature–light combinations which constitute physiological stress seem to trigger CYN production and particularly CYN release from cells. The lowest growth rate observed at 16 °C and 60 μE m⁻² s⁻¹ of strain 22D11 may reflect photoinhibition due to the lower temperature and related limited CO₂-fixation. Under these conditions, extracellular CYN concentrations increased to 58% of total CYN, while the share of extracellular CYN of all other light and temperature regimes was 11–26%. From the results and the experimental design we conclude an active release of the toxin into medium to be more likely than mere leakage from cells.     

Cyanobacteria and cyanobacterial toxins in the alkaline crater lakes Sonachi and Simbi, Kenya

The phytoplankton communities and the production of cyanobacterial toxins were investigated in two alkaline Kenyan crater lakes, Lake Sonachi and Lake Simbi. Lake Sonachi was mainly dominated by the cyanobacterium Arthrospira fusiformis, Lake Simbi by A. fusiformis and Anabaenopsis abijatae. The phytoplankton biomasses measured were high, reaching up to 3159 mg l⁻¹ in L. Sonachi and up to 348 mg l⁻¹ in L. Simbi. Using HPLC techniques, one structural variant of the hepatotoxin microcystin (microcystin-RR) was found in L. Sonachi and four variants (microcystin-LR, -RR, -LA and -YR) were identified in L. Simbi. The neurotoxin anatoxin-a was found in both lakes. To our knowledge this is the first evidence of cyanobacterial toxins in L. Sonachi and L. Simbi. Total microcystin concentrations varied from 1.6 to 12.0 μg microcystin-LR equivalents g⁻¹ DW in L. Sonachi and from 19.7 to 39.0 μg microcystin-LR equivalents g⁻¹ DW in L. Simbi. Anatoxin-a concentrations ranged from 0.5 to 2.0 μg g⁻¹ DW in L. Sonachi and from 0 to 1.4 μg g⁻¹ DW in L. Simbi. In a monocyanobacterial strain of A. fusiformis, isolated from L. Sonachi, microcystin-YR and anatoxin-a were produced. The concentrations found were 2.2 μg microcystin g⁻¹ DW and 0.3 μg anatoxin-a g⁻¹ DW. This is the first study showing A. fusiformis as producer of microcystins and anatoxin-a. Since A. fusiformis occurs in mass developments in both lakes, a health risk for wildlife can be expected.     

The effect of seasonality on oxidative metabolism in Nacella (Patinigera) magellanica

We studied the seasonal variation on aerobic metabolism and the response of oxidative stress parameters in the digestive glands of the subpolar limpet Nacella (P.) magellanica. Sampling was carried out from July (winter) 2002 to July 2003 in Beagle Channel, Tierra del Fuego, Argentina. Whole animal respiration rates increased in early spring as the animals spawned and remained elevated throughout summer and fall (winter: 0.09 ± 0.02 μmol O₂ h^− 1 g^− 1; summer: 0.31 ± 0.06 μmol O₂ h^− 1 g^− 1). Oxidative stress was assessed at the hydrophilic level as the ascorbyl radical content / ascorbate content ratio (A / AH⁻). The A / AH⁻ ratio showed minimum values in winter (3.7 ± 0.2 10^− 5 AU) and increased in summer (18 ± 5 10^− 5 AU). A similar pattern was observed for lipid radical content (122 ± 29 pmol mg^− 1 fresh mass [FW] in winter and 314 ± 45 pmol mg^− 1 FW in summer), iron content (0.99 ± 0.07 and 2.7 ± 0.6 nmol mg^− 1 FW in winter and summer, respectively) and catalase activity (2.9 ± 0.2 and 7 ± 1 U mg^− 1 FW in winter and summer, respectively). Since nitrogen derived radicals are thought to be critically involved in oxidative metabolism in cells, nitric oxide content was measured and a significant difference in the content of the Fe–MGD–NO adduct in digestive glands from winter and summer animals was observed. Together, the data indicate that both oxygen and nitrogen radical generation rates in N. (P.) magellanica are strongly dependent on season.     

Dictyostelium discoideum chemotaxis: threshold for directed motion

The chemotactic response of Dictyostelium discoideum cells to stationary, linear gradients of cyclic adenosine 3',5'-monophosphate (cAMP) was studied using microfluidic devices. In shallow gradients of less than 10(-3) nM/microm, the cells showed no directional response and exhibited a constant basal motility. In steeper gradients, cells moved up the gradient on average. The chemotactic speed and the motility increased with increasing steepness up to a plateau at around 10(-1) nM/microm. In very steep gradients, above 10 nM/microm, the cells lost directionality and the motility returned to the sub-threshold level. In the regime of optimal response the difference in receptor occupancy at the front and back of the cell is estimated to be only about 100 molecules.     

Dynamics of ATP and movement in Eurasian perch (Perca fluviatilis L.) sperm in conditions of decreasing osmolality

Repetitive activation of perch (Perca fluviatilis L.) sperm motility was investigated in this study. The first phase of sperm motility activation was initiated by dilution in a 260 mM glucose solution (75% motility). The second phase of motility was achieved by adding water to previously activated sperm, so that the glucose concentration dropped to 220 mM (24% motility). Finally, the third phase was obtained by further addition of water (down to 90 mM glucose) to the activated sperm suspension (15% motility). Parallel measurements of sperm ATP content were also made. The median value for nonactivated sperm was 43.9 nmol ATP/10⁹ spermatozoa. The ATP concentration decreased significantly from 35 to 7 nmol ATP/10⁹ spermatozoa after successive activations of motility in the above glucose solutions. Sperm velocity ranged in value from 25 to 330 μm/sec at 10 sec postactivation, from 10 to 290 μm/sec at 30 sec, and from 0 to 200 μm/sec at 45 sec. A model postulating several classes in the population of spermatozoa is developed, tentatively accounting for such successive activation. Possible further application of multiple sperm activation is discussed.     

Does uptake of Alexandrium fundyense cysts contribute to the levels of PSP toxin found in the sea scallop, Placopecten magellanicus?

Atlantic sea scallops, Placopecten magellanicus, in most areas of the Bay of Fundy, New Brunswick, Canada, have year-round concentrations of paralytic shellfish posioning (PSP) toxins greater than the regulatory concentration of 80 μg STX eq. 100 g⁻¹ wet weight. Scallops (mean shell height of 10.7 cm, age 3–5 years) were collected by SCUBA and individually tagged near Parker Island, Bay of Fundy. Half were hung 2 m below the low tide water level and the remainder were placed on the bottom (11 m depth at low tide) under the scallops held at 2 m. Scallop, water and sediment samples were collected monthly for determination of concentrations of PSP toxins and Alexandrium fundyense.In October, 1993, mean concentrations of PSP toxins in digestive gland, and mantle were 3205 and 1018 μg STX eq. 100 g⁻¹ wet weight, respectively. Eight months later (June 1994), PSP concentrations in digestive glands from the surface and bottom had declined to 504 and 682 μg STX eq. 100 g⁻¹ wet weight, respectively, whereas those in the mantle had declined to 802 and 681 μg STX eq. 100 g⁻¹ wet weight. During July 1994, A. fundyense concentrations observed at Parker Island and offshore were 320 cells l⁻¹ and 14,200 cells l⁻¹, respectively. Subsequently, toxin concentrations in surface and bottom scallop digestive glands increased to 12,720 and 11,408 μg STX eq. 100 g⁻¹ wet weight, whereas concentrations in mantles increased to 2126 and 1748 μg STX eq. 100 g⁻¹ wet weight, respectively. Concentrations of PSP toxins in these tissues in October 1994 were similar to those measured in October 1993. Concentrations of PSP toxin were less than the regulatory concentration in the gonads and non-detectable in adductor muscles of all scallops sampled.There were no statistically significant differences in profiles for uptake and depuration of PSP toxins in scallops held at the surface compared to those from bottom, suggesting that A. fundyense cysts at the concentrations found in the sediment (45 cysts cm⁻³) did not contribute significantly to the year-round presence of PSP toxins within scallop tissues. The year-round occurrence of PSP toxin is probably due to accumulation during summer blooms followed by a very slow rate of depuration.     

Molecular identification of intestinal microflora in Takifugu niphobles

We investigated the intestinal microflora of coastal fish including Takifugu niphobles using both culture techniques and library cloning. As a result, the numbers of bacteria appeared on agar media were 1.0 × 10⁴ to 1.4 × 10⁹ CFU/g (colony forming units/gram), whereas those of total bacteria stained with 4′,6-diamidino-2-phenylindole were 4.7 × 10¹⁰ to 1.9 × 10¹¹ cells/gram, irrespective of different fish species. In addition, the culture technique showed that the intestinal microflora in all specimens was mainly composed of the genus Vibrio. In contrast, the direct count method showed that spirochaetes with length of 2.5-4.5 μm were present in the intestinal contents of T. niphobles at high densities, whereas such bacteria could not be detected in those of other fish species. Library cloning yielded the sequences of 16S rRNA genes that were divided into seven taxonomic categories of bacteria including Actinobacteria, Bacilli, Clostridia, Gammaproteobacteria, Mollicutes, Spirochaetes and an unclassified bacterial group. These results demonstrate that the molecular diversity of the intestinal bacteria in T. niphobles based on the clone library method reflects the direct observation by fluorescence microscopy to some extent.     

Hydroxylation of naringin by Trichoderma harzianum to dramatically improve its antioxidative activity

Transforming naringin using the mycelium of Trichoderma harzianum CGMCC 1523 produces two metabolites, 3′,4′,5,7-tetrahydroxy flavanone-7-rhamnoglucoside (3′-OHN) and 3′,4′,5′,5,7-pentahydroxy flavanone-7-rhamnoglucoside (3′,5′-DOHN), both of which were characterized by ESI–MS, ¹H NMR and ¹³C NMR analyses. The time course of the biotransformation by T. harzianum showed that 3′-OHN and 3′,5′-DOHN appeared simultaneously at 6 h, and the conversion yield (32.6%) of 3′,5′-DOHN was higher (10.6%) than that of 3′-OHN at 56 h. The optimal biotransformation temperature was 30 °C, the optimal pH was 5.0, and the optimal concentration of naringin was 400 mg/l. The bigger volume of biotransformation mixture and lower shaking speed did not favor hydroxylation reactions. The radical scavenging activity of naringin at 2000 μM was 11.1%, whereas activity of 3′-OHN at 100 μM could reach 38.4%, which is 68.6 times more than naringin. Antioxidative activity of 3′,5′-DOHN was increased 13.5% at 100 μM compared to 3′-OHN.     

Water relations and carbon dioxide exchange of epiphytic lichens in the Namib fog desert

Although there is only negligible rainfall, frequent nocturnal fog, dew and high air humidity support a luxurious lichen vegetation in the coastal zone of the central Namib Desert (Namibia). In earlier publications, we have studied ecophysiological performance of a series of epilithic and terrestrial lichens. Here, we have extended this work to three epiphytic species (Heterodermia namaquana, Ramalina lacera, and Xanthoria turbinata) that inhabit the sparse perennial shrubs growing in this area. Our intention, monitoring lichen CO₂ exchange, their water relations and microclimate conditions, was to determine the functional mechanisms that allow these epiphytes to exist under the special conditions of a fog desert. Measurements were conducted mainly during the spring season.The epiphytic lichens showed response patterns very similar to the epilithic and epigaeic species at the same site. Their metabolism was activated through moistening by dew and/or fog during the night and, in the very early morning, they exhibited the typical brief peak of net photosynthesis (NP) between sunrise and desiccation. The thalli were almost completely dry for the remainder of the day. Average duration of the positive NP during the morning peak was about 3 h. Dew condensation, alone, resulted in activation that provided 58–63% of integrated carbon income (ΣNP) as compared to fog (plus dew). In the late afternoon, there was a tendency for hydration to increase again, due to water vapour uptake at higher air humidity, and this allowed on some days a brief additional period of very low rates of photosynthesis shortly before sunset.Light response of photosynthesis showed “sun-plant” characteristics with saturation around 1000 μmol m⁻² s⁻¹ photosynthetically active photon flux density (PPFD). Light compensation point (LCP) of CO₂ exchange after sunrise was highly dependent on actual water content (WC) for X. turbinata: at low hydration it was ca. 10 μmol m⁻² s⁻¹ PPFD whilst, at high WC, it was almost 80 μmol m⁻² s⁻¹ PPFD. In contrast, LCP of R. lacera was almost independent of WC. This phenomenon was probably due to differences in thallus structure.Maximal attained NP and daily ΣNP both showed a saturation-type response to previous maximal nocturnal WC. Neither parameter was increased substantially when higher maximal thallus WCs were produced by experimental moistening in the night. All three species, despite their different morphologies, performed optimally at the highest nocturnal moistening achieved by natural fog and were not able to make use of higher hydration.The three studied epiphytes were similar in their chlorophyll-related rates of NP. Due to lower chlorophyll content, dry weight and carbon-related NP of X. turbinata was only about one-third of that of the other two species. The average carbon income on days with fog and/or dew hydration during the spring season amounted to 2.4 and 2.1 mgC (gC)⁻¹ day⁻¹ (related to thallus carbon content) for H. namaquana and R. lacera, respectively. This primary production was of similar magnitude to those found for the terrestrial species at the same site.     

Morphology of Pyrodinium bahamense Plate (Dinoflagellata) near Isla San José, Gulf of California, Mexico

The morphology of Pyrodinium bahamense south of Isla San José in the Gulf of California, Mexico was described using light and scanning electron microscopy. Morphological and dimensional examination of whole cells and thecal patterns were conducted to discriminate between P. bahamense var. compressum and P. bahamense var. bahamense. Microscopic examinations confirmed that specimens of P. bahamense from Isla San José are closely related to P. bahamense var. bahamense. The main average dimensions were: cells 41.9 μm long, 43.8 μm wide, 55.6 μm amplitude, apical horn 7.2 μm long, and the left antapical spine 19.5 μm long. The highest cell concentration was 240 cells l⁻¹ and occurred with a bloom of Pseudo-nitzschia spp. The presence of this dinoflagellate off the east coast of the Baja California Peninsula had not been previously reported. Recently, P. bahamense from Florida tested positive for saxitoxins. Paralytic shellfish poisoning from this species has occurred in Mexican waters. Here, significant aspects of taxonomy, toxicology, life cycle, and ecology are discussed.     

In vitro cytogenetic effects of Andrographis paniculata (kalmegh) on arsenic

In vitro effects of arsenic in human peripheral lymphocytes (HPL) at three different doses – 3.6×10⁻⁴, 1.4×10⁻³ and 0.72×10⁻³ μM for 24 h before harvesting on sister chromatid exchanges (SCE), Cell cycle proliferative index/replicative index (CCPI/RI), %M₁, %M₂ and %M₃, population doubling time (PDT) and average generation time (AGT) were examined. Andrographis paniculata (commonly referred to as ‘kalmegh’) has been used for centuries in traditional Indian and Chinese herbal medicine as a safe, natural folk remedy for assorted health concerns. In the present study, kalmegh (0.01 μg/7 ml culture media) was used along with the highest dose of arsenic; the results showed that arsenic induced increase in these genotoxic endpoints were fairly diminished by kalmegh. In addition, mutagenic in vitro effect of ethyl methanesulphonate (EMS) was used as a positive control in this study. It is thus concluded from this study that Andrographis has a protective role in arsenic toxicity.