Low CO2 Levels Research Articles

Modeling the respiration rate of Golden papayas stored under different atmosphere conditions at room temperature

The present study aimed to measure the respiration rate of papayas (cv. Golden) stored under controlled atmosphere at room temperature, with decreasing O2 and increasing CO2 levels, in order to identify mathematical models capable of predicting respiration rate throughout storage. A model was proposed based on the Michaelis–Menten equation with uncompetitive inhibition and kinetic parameters that change during storage time. A second-order nonlinear regression model was used as reference for the mathematical approach. Nine experiments with three replicates were conducted under different controlled atmospheres to generate respiration data. A closed system method was used to measure the respiration rate at 2d intervals over 13d of storage at ambient temperature (23°C). Peel color measurements indicated total ripening of fruit stored in high O2 atmospheres, whereas ripening was minimal in atmospheres containing low O2 and high CO2 levels. The respiration rate remained at the lowest value, but gradually increased during storage at the lowest O2 level associated with the highest CO2 concentration. The nonlinear regression model obtained the lowest AICc value with VarPow variance, indicating a better fit than the Michaelis–Menten model. However, the latter, whose kinetic parameters change according to a polynomial second-order equation (MMQ), displayed a better fit than the nonlinear regression model evaluated by homoscedastic variance. Additionally, MMQ was more sensitive than nonlinear regression in detecting the real change in respiration rate in a biological system as a function of different gas compositions during storage.

Microfluidic chip for automated screening of carbon dioxide conditions for microalgal cell growth.

This paper reports on a microfluidic device capable of screening carbon dioxide (CO2) conditions for microalgal cell growth. The device mainly consists of a microfluidic cell culture (MCC) unit, a gas concentration gradient generator (CGG), and an in-line cell growth optical measurement unit. The MCC unit is structured with multiple aqueous-filled cell culture channels at the top layer, multiple CO2 flow channels at the bottom layer, and a commercial hydrophobic gas semipermeable membrane sandwiched between the two channel layers. The CGG unit provides different CO2 concentrations to support photosynthesis of microalgae in the culture channels. The integration of the commercial gas semipermeable membrane into the cell culture device allows rapid mass transport and uniform distribution of CO2 inside the culture medium without using conventional agitation-assisted convection methods, because the diffusion of CO2 from the gas flow channels to the culture channels is fast over a small length scale. In addition, automated in-line monitoring of microalgal cell growth is realized via the optical measurement unit that is able to detect changes in the light intensity transmitted through the cell culture in the culture channels. The microfluidic device also allows a simple grayscale analysis method to quantify the cell growth. The utility of the system is validated by growing Chlamydomonas reinhardtii cells under different low or very-low CO2 levels below the nominal ambient CO2 concentration.

CO2 induced growth response in a diatom dominated phytoplankton community from SW Bay of Bengal coastal water

The ongoing increase in surface seawater CO2 level could potentially impact phytoplankton primary production in coastal waters; however, CO2 sensitivity studies on tropical coastal phytoplankton assemblages are rare. The present study investigated the interactive impacts of variable CO2 level, light and zinc (Zn) addition on the diatom dominated phytoplankton assemblages from the western coastal Bay of Bengal. Increased CO2 supply enhanced particulate organic matter (POC) production; a concomitant depletion in δ13CPOM values at elevated CO2 suggested increased CO2 diffusive influx inside the cell. Trace amount of Zn added under low CO2 level accelerated growth probably by accelerating Zn-Carbonic Anhydrase activity which helps in converting bicarbonate ion to CO2. Almost identical values of δ13CPOM in the low CO2 treated cells grown with and without Zn indicated a low discrimination between 13C and 12C probably due to bicarbonate uptake. These evidences collectively indicated the existence of the carbon concentration mechanisms (CCMs) at low CO2. A minimum growth rate was observed at low CO2 and light limited condition indicating light dependence of CCMs activity. Upon the increase of light and CO2 level, growth response was maximum. The cells grown in the low CO2 levels showed higher light stress (higher values of both diatoxanthin index and the ratio of photo-protective to light-harvesting pigments) that was alleviated by both increasing CO2 supply and Zn addition (probably by efficient light energy utilization in presence of adequate CO2). This is likely that the diatom dominated phytoplankton communities benefited from the increasing CO2 supply and thus may enhance primary production in response to any further increase in coastal water CO2 levels and can have large biogeochemical consequences in the study area.

Recent advances in modified atmosphere packaging and edible coatings to maintain quality of fresh-cut fruits and vegetables

ABSTRACTProcessing of fruits and vegetables generates physiological stresses in the still living cut tissue, leading to quality deterioration and shorter shelf life as compared with fresh intact produces. Several strategies can be implemented with the aim to reduce the rate of deterioration of fresh-cut commodities. Such strategies include low temperature maintenance from harvest to retail and the application of physical and chemical treatments such as modified atmosphere packaging (MAP) with low O2 and high CO2 levels and antioxidant dips. Other technologies such as edible coatings with natural additives, new generation of coatings using nanotechnological solutions such as nanoparticles, nanoencapsulation, and multilayered systems, and nonconventional atmospheres such as the use of pressurized inert/noble gases and high levels of O2 have gained a lot of interest as a possibility to extend the shelf life of minimally processed fruits and vegetables. However, the high perishability of these products challenges in many cases their marketability by not achieving sufficient shelf life to survive the distribution system, requiring the combination of treatments to assure safety and quality. This review reports the recent advances in the use of MAP, edible coatings, and the combined effect of both technologies to extend the shelf life of fresh-cut fruits and vegetables.

Atmospheric CO2 Alters Resistance of Arabidopsis to Pseudomonas syringae by Affecting Abscisic Acid Accumulation and Stomatal Responsiveness to Coronatine.

Atmospheric CO2 influences plant growth and stomatal aperture. Effects of high or low CO2 levels on plant disease resistance are less well understood. Here, resistance of Arabidopsis thaliana against the foliar pathogen Pseudomonas syringae pv. tomato DC3000 (Pst) was investigated at three different CO2 levels: high (800 ppm), ambient (450 ppm), and low (150 ppm). Under all conditions tested, infection by Pst resulted in stomatal closure within 1 h after inoculation. However, subsequent stomatal reopening at 4 h, triggered by the virulence factor coronatine (COR), occurred only at ambient and high CO2, but not at low CO2. Moreover, infection by Pst was reduced at low CO2 to the same extent as infection by mutant Pst cor-. Under all CO2 conditions, the ABA mutants aba2-1 and abi1-1 were as resistant to Pst as wild-type plants under low CO2, which contained less ABA. Moreover, stomatal reopening mediated by COR was dependent on ABA. Our results suggest that reduced ABA levels at low CO2 contribute to the observed enhanced resistance to Pst by deregulation of virulence responses. This implies that enhanced ABA levels at increasing CO2 levels may have a role in weakening plant defense.

Effects of ocean acidification on the physiological performance and carbon production of the Antarctic sea ice diatom Nitzschia sp. ICE-H

Ocean acidification (OA) resulting from increasing atmospheric CO2 strongly influences marine ecosystems, particularly in the polar ocean due to greater CO2 solubility. Here, we grew the Antarctic sea ice diatom Nitzschia sp. ICE-H in a semicontinuous culture under low (~400ppm) and high (1000ppm) CO2 levels. Elevated CO2 resulted in a stimulated physiological response including increased growth rates, chlorophyll a contents, and nitrogen and phosphorus uptake rates. Furthermore, high CO2 enhanced cellular particulate organic carbon production rates, indicating a greater shift from inorganic to organic carbon. However, the cultures grown in high CO2 conditions exhibited a decrease in both extracellular and intracellular carbonic anhydrase activity, suggesting that the carbon concentrating mechanisms of Nitzschia sp. ICE-H may be suppressed by elevated CO2. Our results revealed that OA would be beneficial to the survival of this sea ice diatom strain, with broad implications for global carbon cycles in the future ocean.

Inorganic-organic based novel nano-conjugate material for effective cobalt(II) ions capturing from wastewater

Simultaneous detection and removal of heavy metals with high sensitivity and adsorption capacity of a suitable material is an ultimate goal in industry for the purification of contaminated water samples. This study was investigated the use of functional ligand immobilized mesoporous silica based nano-conjugate materials for efficient detection and removal of cobalt (Co(II)) ions from wastewaters with optical color optimization. The mesoporous silica, newly prepared organic ligand and the nano-conjugate materials were characterized systematically. The effect of pH on the sensitivity and selectivity of the formed complexes was studied after adding the Co(II) ions in specific condition. Under optimum conditions, the nano-conjugate materials was formed visible color after capturing of the Co(II) ions. The data of calibration graphs were linear in the low concentration level of Co(II) ions with the detection limit of 0.33µg/L. The performance of the solid-phase adsorption was enriched the Co(II) ions efficiently into the materials surface. The kinetic performance was high and the isotherm study was conducted using the Langmuir adsorption model. The results exhibited very high adsorption capacity of 170.17mg/g and this capacity was compared with different forms of materials. In addition, the materials was adsorbed the Co(II) ions with higher 96% from the synthetic multi-mixture metal ions containing samples and this is confirmed the materials high selectivity for efficient detection and adsorption of Co(II) ions. Desorption experiments were carried out with 0.30MHCl proved that without significant loss in its original performance that could be reused in several cycles. Therefore, the proposed materials here is an interesting and promising attempt for the trace Co(II) ions capturing in water samples and will have much more applied field.

Simultaneously reducing CO2 and particulate exposures via fractional recirculation of vehicle cabin air

Prior studies demonstrate that air recirculation can reduce exposure to nanoparticles in vehicle cabins. However when people occupy confined spaces, air recirculation can lead to carbon dioxide (CO2) accumulation which can potentially lead to deleterious effects on cognitive function. This study proposes a fractional air recirculation system for reducing nanoparticle concentration while simultaneously suppressing CO2 levels in the cabin. Several recirculation scenarios were tested using a custom-programmed HVAC (heat, ventilation, air conditioning) unit that varied the recirculation door angle in the test vehicle. Operating the recirculation system with a standard cabin filter reduced particle concentrations to 1000 particles/cm3, although CO2 levels rose to 3000 ppm. When as little as 25% fresh air was introduced (75% recirculation), CO2 levels dropped to 1000 ppm, while particle concentrations remained below 5000 particles/cm3. We found that nanoparticles were removed selectively during recirculation and demonstrated the trade-off between cabin CO2 concentration and cabin particle concentration using fractional air recirculation. Data showed significant increases in CO2 levels during 100% recirculation. For various fan speeds, recirculation fractions of 50–75% maintained lower CO2 levels in the cabin, while still reducing particulate levels. We recommend fractional recirculation as a simple method to reduce occupants’ exposures to particulate matter and CO2 in vehicles. A design with several fractional recirculation settings could allow air exchange adequate for reducing both particulate and CO2 exposures. Developing this technology could lead to reductions in airborne nanoparticle exposure, while also mitigating safety risks from CO2 accumulation.

Analysis of CO2 monitoring data demonstrates poor ventilation rates in Albanian schools during the cold season

Poor ventilation in schools is associated with accumulation of indoor-generated pollutants, which is associated with “stuffy” air, elevated risk of infectious diseases and impaired learning outcomes. This survey in Albania was conducted as part of WHO’s efforts to facilitate assessments of indoor air quality and other environmental factors in schools in the European Region. The survey was conducted in 36 classrooms in 12 middle schools (eight urban and four rural) from December 2011 through March 2012. In each school, carbon dioxide (CO2) was continuously measured in three classrooms during one school week. Ventilation rates during classes were estimated using the build-up and steady-state mass balance equations utilizing CO2 concentration data, classroom occupancy and classroom volume. All 12 schools had gravimetric ventilation systems. Heating systems were absent or not operational in most schools. Average classroom temperatures during lessons varied from 9.1 to 14.4 °C (median 11.7 °C) with lower temperature associated with poorer ventilation. Weekly average CO2 levels during classes ranged from 1286 to 5546 ppm (median 2776 ppm) while average ventilation rates ranged from 0.8 to 3.6 (median 1.8) litres per second per person. Classrooms with indoor combustion heaters had higher indoor temperature, lower CO2 levels and higher levels of carbon monoxide (CO). WHO guidelines on 1- and 8-h CO exposure levels were exceeded in one classroom. Classroom CO2 levels were substantially above and ventilation rates below existing national and international guidelines. Detrimental impacts of poor ventilation on health and learning outcomes are likely to be substantial in Albanian schools during the cold season. Indoor temperature in most classrooms was below the commonly recommended levels.

Competition between cyanobacteria and green algae at low versus elevated CO2: who will win, and why?

Traditionally, it has often been hypothesized that cyanobacteria are superior competitors at low CO2 and high pH in comparison with eukaryotic algae, owing to their effective CO2-concentrating mechanism (CCM). However, recent work indicates that green algae can also have a sophisticated CCM tuned to low CO2 levels. Conversely, cyanobacteria with the high-flux bicarbonate uptake system BicA appear well adapted to high inorganic carbon concentrations. To investigate these ideas we studied competition between three species of green algae and a bicA strain of the harmful cyanobacterium Microcystis aeruginosa at low (100 ppm) and high (2000 ppm) CO2. Two of the green algae were competitively superior to the cyanobacterium at low CO2, whereas the cyanobacterium increased its competitive ability with respect to the green algae at high CO2. The experiments were supported by a resource competition model linking the population dynamics of the phytoplankton species with dynamic changes in carbon speciation, pH and light. Our results show (i) that competition between phytoplankton species at different CO2 levels can be predicted from species traits in monoculture, (ii) that green algae can be strong competitors under CO2-depleted conditions, and (iii) that bloom-forming cyanobacteria with high-flux bicarbonate uptake systems will benefit from elevated CO2 concentrations.

Hydrogen Production VIA Catalytic Decomposition of Methane

Methane decay on different Ni-bolstered impetuses has been examined as a strategy for generation of sans co hydrogen for use in energy components. The low levels of CO shaped because of the collaboration of surface carbon (framed from methane disintegration) with the help have been quantitatively investigated (part per million levels) by methanation of the CO and consequent examination by fire ionization location (FID). This examination highlights the reliance of the sort of carbon shaped and the measure of CO developed on the idea of the help. No filamentous carbon was seen on Ni/H-ZSM-5 at hoisted methane deterioration temperatures, though Ni/HY and Ni/SiO2 indicated filamentous carbon arrangement over the whole temperature go examined (723 K to 873 K). While two types of carbon (carbidic and graphitic) were seen on the Ni/SiO2 after methane disintegration at 723 K, just graphitic carbon was seen at 823 K. The rate of CO development was seen to be most elevated on Ni/H-ZSM-5 and least on Ni/SiO2. The CO arrangement rates demonstrated a typical pattern for every one of the impetuses: high starting rates taken after by a lower balanced out rate. The CO development rates were found to increment with expanding temperature. The CO content in the hydrogen stream was ca. 50 ppm and 250 ppm for Ni/SiO2 and Ni/HY, individually, after the CO creation rates settled. The low levels of CO combined with the dependability of the impetuses for methane decay make this a fascinating theoretical process for hydrogen creation for energy component applications. Recovery considers have demonstrated that there is no loss of movement for methane deterioration at 723 K on Ni/H-ZSM-5 over numerous response cycles.

An easy and fast IC-CL procedure for the monitoring of Cu(II) and Co(II) in environmental samples

A luminol chemiluminescence (CL) detection/flow injection analysis technique coupled with ion chromatography (IC) has been employed for the determination of low levels of Cu(II) and Co(II) in drinking water samples. The detection system was the CL of luminol/perborate or luminol/percarbonate in alkaline medium catalyzed by these transition metals. Oxalic acid in a solution of KOH and N(CH3)4OH was used as an eluent in the IC to improve the column selectivity (Dionex CS5A). Concentration and pH of the eluent affected simultaneously the CL intensity and the retention times (t R). Under the elution conditions used here, the retention times of both metal ions were much greater when the concentration of oxalic acid was decreased. Thus, R t(Cu) = 2.15 min and t R(Co) = 4.50 min were measured at 80 mM oxalic acid concentration, while t R raised to 4.12 and 18 min for Cu(II) and Co(II), respectively, using a 10-mM concentration, but on the other hand, the CL signals showed substantially higher values when the concentration of oxalic acid was lesser in the eluent. An optimum oxalic acid concentration of 20 mM and an eluent pH = 4.7 were selected in order to have reproducible signals with a total analysis time of 10 min. The optimum flow rate for the mobile phase was 1.5 mL min−1. The concentration and pH of the postcolumn reagents also affected the CL signal, obtaining optimum concentrations of 5 mM for both oxidants (perborate or percarbonate) and luminol, this last dissolved in a 0.1-M borate buffer at pH 12. The optimum flow rate for the postcolumn reagents was 1 mL min−1. Linear calibrations for both transition metal ions were established, with calculated detection limits of 0.15 ng mL−1 for Co(II) and 0.20 μg mL−1 for Cu(II). Others ions commonly present in natural waters showed little or no interference. The method was successfully applied to water samples spiked with Cu(II) and Co(II), obtaining recoveries in the range of 85–128%, depending on the metal concentrations.

Environmental assessment of domestic boilers: A comparison of condensing and traditional technology using life cycle assessment methodology

This study has carried out a life cycle assessment of two different domestic natural gas boilers in Italy, taking into account 3 different climatic regions and two dwellings with different energy classes. The aim of this research was to compare traditional and condensing boiler technologies. Primary data relating to the two products under analysis was supplied by an international boiler manufacturer, whilst the Ecoinvent database v2.2 was used as a secondary source of data. The assessment was performed using the CML and Cumulative Energy Demand (CED) methods, by considering the categories required by “Environmental Product Declaration” (EPD) certification systems. The results of the analysis show that on average, the condensing technology has a 23% lower environmental impact than its traditional counterpart for each scenario in the six impact categories considered. This is essentially due to its lower fuel consumption during the use phase and the lower levels of CO and NOx emitted during the combustion of natural gas. The study also shows that the use phase is by far the biggest contributor to the environmental impact, and on average is responsible for more than 90% of the total impact.

Efficacy of Controlled Atmosphere Treatments to Manage Arthropod Pests of Dry-Cured Hams.

Research here explored the use of controlled atmospheres (CA) for managing arthropod pests that infest dry-cured hams. Experiments were conducted with low oxygen (O2) achieved with low pressure under a vacuum, high carbon dioxide (CO2), and ozone (O3). Results showed that both low O2 and high CO2 levels required exposures up to 144 h to kill 100% of all stages of red-legged ham beetle, Necrobia rufipes (De Geer) (Coleoptera: Cleridae) and ham mite Tyrophagus putrescentiae (Schrank) (Sarcoptiformes: Acaridae) at 23 °C. In addition, both low O2 and high CO2 had no significant mortality against the ham beetle and ham mites at short exposures ranging from 12 to 48 h. Ham beetles were more tolerant than ham mites to an atmosphere of 75.1% CO2 and low pressure of 25 mm Hg, which imposed an atmosphere estimated at 0.9% O2. Both low O2 and high CO2 trials indicated that the egg stages of both species were more tolerant than other stages tested, but N. rufipes eggs and pupae were more susceptible than larvae and adults to high concentration ozone treatments. The results indicate that O3 has potential to control ham beetles and ham mites, particularly at ≈166 ppm in just a 24 h exposure period, but O3 is known from other work to have poor penetration ability, thus it may be more difficult to apply effectively than low O2 or high CO2. would be. CA treatment for arthropod pests of dry-cured hams show promise as components of integrated pest management programs after methyl bromide is no longer available for use.

Rapid adaptation of harmful cyanobacteria to rising CO2

Rising atmospheric CO2 concentrations are likely to affect many ecosystems worldwide. However, to what extent elevated CO2 will induce evolutionary changes in photosynthetic organisms is still a major open question. Here, we show rapid microevolutionary adaptation of a harmful cyanobacterium to changes in inorganic carbon (Ci) availability. We studied the cyanobacterium Microcystis, a notorious genus that can develop toxic cyanobacterial blooms in many eutrophic lakes and reservoirs worldwide. Microcystis displays genetic variation in the Ci uptake systems BicA and SbtA, where BicA has a low affinity for bicarbonate but high flux rate, and SbtA has a high affinity but low flux rate. Our laboratory competition experiments show that bicA + sbtA genotypes were favored by natural selection at low CO2 levels, but were partially replaced by the bicA genotype at elevated CO2 Similarly, in a eutrophic lake, bicA + sbtA strains were dominant when Ci concentrations were depleted during a dense cyanobacterial bloom, but were replaced by strains with only the high-flux bicA gene when Ci concentrations increased later in the season. Hence, our results provide both laboratory and field evidence that increasing carbon concentrations induce rapid adaptive changes in the genotype composition of harmful cyanobacterial blooms.

Low atmospheric CO2 levels during the Little Ice Age due to cooling-induced terrestrial uptake

Land carbon uptake reduced atmospheric CO2 levels during the Little Ice Age. Numerical simulations of atmospheric carbonyl sulfide levels and ice-core carbon isotope data reveal that temperature change, not land-cover change, was responsible.

Low Temperature and Short-Term High-CO2 Treatment in Postharvest Storage of Table Grapes at Two Maturity Stages: Effects on Transcriptome Profiling.

Table grapes (Vitis vinifera cv. Cardinal) are highly perishable and their quality deteriorates during postharvest storage at low temperature mainly because of sensitivity to fungal decay and senescence of rachis. The application of a 3-day CO2 treatment (20 kPa CO2 + 20 kPa O2 + 60 kPa N2) at 0°C reduced total decay and retained fruit quality in early and late-harvested table grapes during postharvest storage. In order to study the transcriptional responsiveness of table grapes to low temperature and high CO2 levels in the first stage of storage and how the maturity stage affect these changes, we have performed a comparative large-scale transcriptional analysis using the custom-made GrapeGen GeneChip®. In the first stage of storage, low temperature led to a significantly intense change in grape skin transcriptome irrespective of fruit maturity, although there were different changes within each stage. In the case of CO2 treated samples, in comparison to fruit at time zero, only slight differences were observed. Functional enrichment analysis revealed that major modifications in the transcriptome profile of early- and late-harvested grapes stored at 0°C are linked to biotic and abiotic stress-responsive terms. However, in both cases there is a specific reprogramming of the transcriptome during the first stage of storage at 0°C in order to withstand the cold stress. Thus, genes involved in gluconeogenesis, photosynthesis, mRNA translation and lipid transport were up-regulated in the case of early-harvested grapes, and genes related to protein folding stability and intracellular membrane trafficking in late-harvested grapes. The beneficial effect of high CO2 treatment maintaining table grape quality seems to be an active process requiring the induction of several transcription factors and kinases in early-harvested grapes, and the activation of processes associated to the maintenance of energy in late-harvested grapes.

Nitrogen transfer properties in tantalum nitride based materials

Ta3-xMxNy (M=Re, Fe, Co; x=0, 0.25, 0.5, 1) materials with different microstructural features (e.g. surface area) were successfully prepared using different synthesis techniques. The dependence of nitrogen transfer properties upon tantalum nitride microstructure and its chemical composition was evaluated using the ammonia synthesis with a H2/Ar feedstream (a reaction involving lattice nitrogen transfer). It was shown that nitrogen reactivity for tantalum nitride is more dominated by lattice nitrogen stability rather than microstructural properties. In the case of non-doped tantalum nitride, only a limited improvement of reactivity with enhanced surface area was observed which demonstrates the limited impact of microstructure upon reactivity. However, the nature of the transition metal dopant as well as its content was observed to play a key role in the nitrogen transfer properties of tantalum nitride and to impact strongly upon its reactivity. In fact, doping tantalum nitride with low levels of Co resulted in enhanced reactivity at lower temperature.

Identification and phylogeny of putative PEPC genes in three toxin‐producing Karenia (Dinophyta) species

Dense blooms of toxin-producing Karenia brevis increase local surface ocean pH through CO2 uptake. To identify genes that may contribute to bloom-related environmental pH and pCO2 changes, transcriptomes with RNA from K.brevis Wilson cultures that had been acclimated to low CO2 (250ppm) or recent CO2 (350ppm) pCO2 levels were assembled. Among the annotated transcripts were PEPC, PPDK, and PEPCK enzymes found in the model C4 carbon fixation pathway. Previous studies have demonstrated that the enzymatic activity of PEPC, PPDK, and/or PEPCK in some algae species, including marine diatoms, is influenced by variations in dissolved inorganic carbon. We found significantly similar PEPC, PPDK, and PEPCK enzymes in the transcriptomes of K.brevis and two sister species Karenia papilionacea, and Karenia mikimotoi. One or more isoforms of PEPC were also identified in the transcriptomes of thirty additional photosynthetic phytoplankton species from nine phyla. Phylogenetic trees were constructed with neighbor joining and maximum likelihood techniques to characterize the evolutionary relationship among phytoplankton, terrestrial plant C4, and terrestrial plant C3 PEPC sequences. Based on the nucleotide trees constructed during this study, the Karenia PEPC transcripts were more closely related to the terrestrial C4 genes than the terrestrial C3 genes. Furthermore, PEPC phylogeny among phytoplankton closely resembles phylogenetic trees constructed with ribosomal RNA. This study confirmed that the toxin-producing dinoflagellates K.brevis, K.mikimotoi, and K. papilionacea express putative PEPC, PEPCK, and PPDK transcripts.

Impaired antibody response and phagocytosis in goats fed a diet low in cobalt

Cobalt (Co) is utilized by rumen microflora to produce vitamin B12. The aim of the present study was to determine whether feeding newly-weaned goats a diet containing low levels of Co results in impairment of neutrophil function, antibody production and/or lymphocyte proliferative responses. Forty, ten week old goats were fed a commercially-prepared concentrate (150g/day) and Rhodesgrass hay ad libitum. This diet contained Co at <0.1mg/kg dry matter. The goats were divided into a control group and a treated group (both n=20). Goats in the treated group were supplemented with bi-monthly subcutaneous injections of 2mg of hydroxycobalamin. Two months after weaning, the goats were immunized with keyhole limpet haemocyanin (KLH). A luminol-dependent chemiluminescence (CL) assay was employed to measure the oxidative respiratory burst of neutrophils during phagocytosis of zymosan A. The lymphocyte proliferative response to phytohaemagglutinin (PHA) and pokeweed mitogen (PWM) was assessed. The controls goats demonstrated a significantly lower antibody (IgG) response to KLH compared with the Co-supplemented goats that was apparent 1 week post immunization and was maintained for the 8 week observation period. Neutrophils from the Co-restricted group demonstrated significantly lower CL responses to opsonized zymosan A. Lymphocytes from the control and treated goats did not differ in their mitogenic responses to PHA and PWM. These results demonstrate that goats fed a diet low in Co exhibited impaired antibody and phagocytic responses.