Optimization of Mixed Cultivation of the Moderate Thermophilic Bioleaching Microorganisms for High Cell Density Using Statistical Methodology

The low functional microbial population density in the industrial bioleaching process has been a limiting factor for the high leaching efficiency, making the microbial cultivation and continuous inoculation an alternative for sustaining the microbial activity. In the present experiment, the defined mixed cultivation of Leptospirillum ferriphilum YSK, Sulfobacillus acidophilus TPY, Acidithiobacillus caldus S2, and Ferroplasma thermophilum L1 was evaluated and optimized by Statistical Methodology. Going through the Plackett–Burman experimental design, pH value, temperature, and c(MgSO₄·7H₂O) were considered as the most significant factors in the defined range. Then, the relationships were analyzed using the steepest ascent design, the central composite design, and finally the response surface methodology. It was suggested that the optimum parameters were pH 1.38, MgSO₄·7H₂O 0.552?g/L, temperature 44?°C, FeSO₄·7H₂O 40?g/L, sulfur 8?g/L, yeast 0.02% w/v, (NH₄)₂SO₄ 3g/L, K₂HPO₄ 0.5g/L, KCl 0.1g/L, Ca(NO₃)₂ 0.01?g/L, in which allowed total cell density of the microbial community to reach 7.63?×?10⁸ cells/mL in the cultivation period. The lab experiments were routinely undertaken with the expectation that the L. ferriphilum YSK, S. acidophilus TPY, A. caldus S2, F. thermophilum L1 could rapid grown from initial cell density of 0.25?×?10⁷ cells/mL to 2.82?×?10⁸ cells/mL, 1.68?×?10⁸ cells/mL, 2.76?×?10⁸ cells/mL, 2.51?×?10⁷ cells/mL, respectively in 58?h. It demonstrates a possibility to co-culture these microbes in a single reactor, providing an efficient way to regenerate of inoculation for biomining process.     

Picolinic acid spray stimulates the antioxidative metabolism and minimizes impairments on photosynthesis on wheat leaves infected by Pyricularia oryzae

Fungal pathogens produce toxins that are important for their pathogenesis and/or aggressiveness towards their hosts. Picolinic acid (PA), a non‐host selective toxin, causes lesions on rice leaves resembling those originated from Pyricularia oryzae infection. Considering that non‐host selective toxins can be useful for plant diseases control, this study investigated whether the foliar spray with PA on wheat (Triticum aestivum L.) plants, in a non‐phytotoxic concentration, could increase their resistance to blast, stimulate the anti‐oxidative metabolism, and minimize alterations in photosynthesis. The PA spray at concentrations greater than 0.1 mg ml^?1 caused foliar lesions, compromised the photosynthesis and was linked with greater accumulation of hydrogen peroxide (H₂O₂) and superoxide anion radical (O₂^??). Fungal mycelial growth, conidia production and germination decreased by PA at 0.3 mg ml^?1. Blast severity was significantly reduced by 59 and 23%, respectively, at 72 and 96 h after inoculation for plants sprayed with PA (0.1 mg ml^?1) at 24 h before fungal inoculation compared to non‐sprayed plants. Reduction on blast symptoms was linked with increases on ascorbate peroxidase (EC 1.11.1.11), catalase (EC 1.11.1.6), glutathione peroxidase (EC 1.11.1.9), glutathione reductase (EC 1.8.1.7), glutathione‐S‐transferase (EC 2.5.1.18), peroxidase (EC 1.11.1.7), and superoxide dismutase (EC 1.15.1.1) activities, lower H₂O₂ and O₂^?? accumulation, reduced malondialdehyde production as well as less impairments to the photosynthetic apparatus. A more efficient antioxidative metabolism that rapidly scavenges the reactive oxygen species generated during P. oryzae infection, without dramatically decreasing the photosynthetic performance, was a remarkable effect obtained with PA spray.     

Effects of carbonyl sulfide, methyl iodide, and sulfuryl fluoride on fruit phytotoxicity and insect mortality

Three potential chemical fumigants: carbonyl sulfide (COS), methyl iodide (MI) and sulfuryl fluoride (SF) were tested at selected dosages on lemons against California red scale (Aonidiella aurantii) and MI and COS were tested on nectarines against codling moth (Cydia pomonella). In nectarines, COS was tested at 0, 20, 40, 60 and 80 mg litre^?1, MI at 0, 10, 15, 20 and 25 mg litre^?1. Both fumigants intensified nectarine peel color, delayed fruit softening, but did not alter overall fruit quality. COS at 80 mg litre^?1 resulted in 87% codling moth mortality, but the fumigant dosage was insufficient to reach the desired probits 9 level (99.9968%). MI gave 100% codling moth mortality at 25 mg litre^?1. Lemons were treated with MI at 0,10,20,40,60 mg litre^?1, SF at 0,10,20,40, 80 mg litre^?1 and COS at 0,20,40, 60 and 80 mg litre^?1. MI gave 100% red scale mortality at ≥40 mg litre^?1 but caused significant fruit injury. Conditioning lemons at 15°C for 3 days before MI fumigation lessened lemon phytotoxicity. Forced aeration at 3.5 standard litres per minute of lemons for 24 h following MI fumigation at 20 mg litre^?1 significantly reduced phytotoxicity compared to 2 h postfumigation aeration after MI treatment. SF at ≥40 mg litre^?1 gave 100% red scale mortality but resulted in commodity phytotoxicity. Lemons treated with the highest selected dose of 80 mg litre^?1 COS gave only 87% kill of red scale, but failed to reach the desired probit 9 level.     

Effects of boron fertilization on `Conference' pear tree vigor, nutrition, and fruit yield and storability

The aim of the study was to examine the response of pear (Pyrus communis L.) trees to soil and foliar applications of boron (B). The experiment was carried out during 2000–2001 in a commercial orchard in Central Poland on mature `Conference' pear trees grafted on Pyrus communis var. caucasica seedlings planted at a spacing of 4 × 2.5 m on a sandy loam soil with a low hot water-extractable B status. Annually, foliar sprays with B were applied. (i) before full bloom (at green and white bud stage, and when 1–5% of flowers was at full bloom), (ii) after flowering (at petal fall, and 7 and 14 days after the end of flowering), or (iii) postharvest in fall (approximately 6 weeks before leaf fall). Spray treatments involved application of B at a rate of 0.2 kg ha^–1 in spring or 0.8 kg ha^–1 in fall. Additionally, other trees were supplied with soil-applied B at the bud break stage at a rate of 2 kg ha^–1. Trees untreated with B served as the control. The results revealed that foliar applications of B before full bloom or after harvest increased fruit set and fruit yield. Tree vigor, mean fruit weight, firmness, soluble solids concentration and titratable acidity of fruits at harvest were not affected by B treatments. Foliar B sprays before full bloom or after harvest increased B concentrations in flowers, and both leaves and fruitlets at 40 days after flowering. Only the foliar treatments after flowering and soil fertilization with B increased the content of this microelement in fruit and leaves at 80 and 120 days after full bloom. Foliar B application before full bloom or after harvest increased calcium (Ca) in fruitlets at 40 days after full bloom, in fruit, and in leaves at 80 and 120 days after full bloom. Nitrogen (N), phosphorus (P), potassium (K), and magnesium (Mg) in plant tissues were not affected by B fertilization. After storage, and also after the ripening period, fruits from the trees sprayed with B before full bloom or after harvest had higher firmness and titratable acidity than those from the control trees. After the ripening period, fruits from the trees sprayed with B before full bloom or after harvest had lower membrane permeability and were less sensitive to internal browning than the control fruits. These findings indicate that prebloom and postharvest B sprays are successful in increasing pear tree yielding and in improving fruit storability under the conditions of low B availability in the soil.     

Sunflower seed deterioration as related to moisture content during ageing, energy metabolism and active oxygen species scavenging

The objectives of the present work were to investigate whether loss of sunflower (Helianthus annuus L.) seed viability was affected by the embryo moisture content (MC) during seed pretreatment at 35°C, and was related to changes in energy metabolism and in the antioxidant defence system. Non‐dormant seeds were equilibrated at MC of the embryonic axis ranging from 0.037 to 0.605 g H₂O g^?1 dry matter (DM) for 1 day at 15°C, and they were then placed at 35°C for various durations up to 14 days before the germination assays at 15°C. As expected, the higher the MC, the faster was seed deterioration. There existed a negative linear relationship between the time taken for germination to drop to 50% (P₅₀) and the embryonic axis MC ranging from 0.108 and 0.438 g H₂O g^?1 DM. In dry seeds, adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate represented 6.3, 14.8 and 70.9% of the adenylate pool, respectively, and the energy charge (EC) was very low (0.14). ATP and ADP levels and EC increased sharply during the first day of equilibrium of seeds at a MC above 0.158 g H₂O g^?1 DM. Subsequent controlled deterioration at 35°C resulted in a decrease in the adenylate pool, and consequently in ATP level. The higher the energy metabolism during ageing, the lower was seed viability. Loss of seed viability was associated with an accumulation of H₂O₂, and then of malondialdehyde (MDA) suggesting that lipid peroxidation was not the only cause of seed deterioration. When there was a sublinear relationship between H₂O₂ content in the embryonic axis and seed viability, MDA accumulation only occurred when 50% of the seed population died within 7 days, i.e. when MC was higher than 0.248 g H₂O g^?1 DM. Ageing was associated with a decrease in the activity of superoxide dismutase, catalase and glutathione reductase, the main enzymes involved in cell detoxification. The involvement of seed MC, as key factor of ageing is discussed with regards to energy metabolism and the regulation of active oxygen species accumulation.     

In vitro anti‐enterovirus 71 activity of gallic acid from Woodfordia fruticosa flowers

Aims: The anti‐enterovirus 71 (EV71) activity of six Nepalese plants’ extracts and gallic acid (GA) isolated from Woodfordia fruticosa Kurz (family; Lythaceae) flowers were evaluated in Vero cells. Methods and Results: The anti‐EV71 activity of tested compounds was evaluated by a cytopathic effect reduction method. Our results demonstrated that flowers’ extracts of W. fruticosa exerted strong anti‐EV71 activity, with a 50% inhibitory concentration (IC₅₀) of 1·2 μg ml^?1 and no cytotoxicity at a concentration of 100 μg ml^?1, and the derived therapeutic index (TI) was more than 83·33. Rivabirin showed no antiviral activity against EV71. Furthermore, GA isolated from W. fruticosa flowers exhibited a higher anti‐EV71 activity than the extract of W. fruticosa flowers, with an IC₅₀ of 0·76 μg ml^?1 and no cytotoxicity at a concentration of 100 μg ml^?1, and the derived TI was 99·57. Conclusions: This study demonstrated that flower extracts of W. fruticosa possessed anti‐EV71 activity and GA isolated from these flowers showed stronger anti‐EV71 activity than that the extracts. Significance and Impact of the Study: Our results suggest that the GA from W. fruticosa flowers may be used as a potential antiviral agent.     

Strong links between teleconnections and ecosystem exchange found at a Pacific Northwest old-growth forest from flux tower and MODIS EVI data

Variability in three Pacific teleconnection patterns are examined to see if net carbon exchange at a low‐elevation, old‐growth forest is affected by climatic changes associated with these periodicities. Examined are the Pacific Decadal Oscillation (PDO), Pacific/North American Oscillation (PNA) and El Niño‐Southern Oscillation (ENSO). We use 9 years of eddy covariance CO₂, H₂O and energy fluxes measured at the Wind River AmeriFlux site, Washington, USA and 8 years of tower‐pixel remote sensing data from the Moderate Resolution Imaging Spectroradiometer (MODIS) to address this question. We compute a new Composite Climate Index (CCI) based on the three Pacific Oscillations to divide the measurement period into positive‐ (2003 and 2005), negative‐ (1999 and 2000) and neutral‐phase climate years (2001, 2002, 2004, 2006 and 2007). The forest transitioned from an annual net carbon sink (NEP=+217 g C m^?2 yr^?1, 1999) to a source (NEP=?100 g C m^?2 yr^?1, 2003) during two dominant teleconnection patterns. Net ecosystem productivity (NEP), water use efficiency (WUE) and light use efficiency (LUE) were significantly different (P<0.01) during positive (NEP=?0.27 g C m^?2 day^?1, WUE=4.1 mg C g^?1 H₂O, LUE=0.94 g C MJ^?1) and negative (NEP=+0.37 g C m^?2 day^?1, WUE=3.4 mg C g^?1 H₂O, LUE=0.83 g C MJ^?1) climate phases. The CCI was linked to variability in the MODIS Enhanced Vegetation Index (EVI) but not to MODIS Fraction of absorbed Photosynthetically Active Radiation (FPAR). EVI was highest during negative climate phases (1999 and 2000) and was positively correlated with NEP and showed potential for using MODIS to estimate teleconnection‐driven anomalies in ecosystem CO₂ exchange in old‐growth forests. This work suggests that any increase in the strength or frequency of ENSO coinciding with in‐phase, low frequency Pacific oscillations (PDO and PNA) will likely increase CO₂ uptake variability in Pacific Northwest conifer forests.     

Butanol production from sweet sorghum bagasse with high solids content: Part I—comparison of liquid hot water pretreatment with dilute sulfuric acid

In these studies, we pretreated sweet sorghum bagasse (SSB) using liquid hot water (LHW) or dilute H₂SO₄ (2 g L^?1) at 190°C for zero min (as soon as temperature reached 190°C, cooling was started) to reduce generation of sugar degradation fermentation inhibiting products such as furfural and hydroxymethyl furfural (HMF). The solids loading were 250–300 g L^?1. This was followed by enzymatic hydrolysis. After hydrolysis, 89.0 g L^?1 sugars, 7.60 g L^?1 acetic acid, 0.33 g L^?1 furfural, and 0.07 g L^?1 HMF were released. This pretreatment and hydrolysis resulted in the release of 57.9% sugars. This was followed by second hydrolysis of the fibrous biomass which resulted in the release of 43.64 g L^?1 additional sugars, 2.40 g L^?1 acetic acid, zero g L^?1 furfural, and zero g L^?1 HMF. In both the hydrolyzates, 86.3% sugars present in SSB were released. Fermentation of the hydrolyzate I resulted in poor acetone‐butanol‐ethanol (ABE) fermentation. However, fermentation of the hydrolyzate II was successful and produced 13.43 g L^?1 ABE of which butanol was the main product. Use of 2 g L^?1 H₂SO₄ as a pretreatment medium followed by enzymatic hydrolysis resulted in the release of 100.6–93.8% (w/w) sugars from 250 to 300 g L^?1 SSB, respectively. LHW or dilute H₂SO₄ were used to economize production of cellulosic sugars from SSB. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:960–966, 2018     

Acute effects of Cu on oxygen consumption and 96 hr-LC50 values in the freshwater fish Tilapia sparrmani (Teleostei: Cichlidae) in Mooi River hard water,South Africa

The median lethal copper (Cu) concentration (96 hr-LC₅₀) values for acute Cu toxicity for Tilapia sparrmanii (live mass: 30 ± 8g) in Mooi River hard water of dolomitic origin at 20 °C, pH 7.9, was 68.1 μmol l^?1. At this 96 hr-LC₅₀ value the specific oxygen consumption rate (∈ O₂) decreased by 44.2 (± 2.1) % from a non-exposed value of 6.6 (±0.32) mmol O₂ kg^?1 hr^?1 to 3.63 (±0.23) mmol O₂ kg ^?1 hr^?1. At 46.4 μmol Cu l^?1, 100% of the exposed T. sparrmanii were still alive after 96 hours, but the ∈ O₂ decreased by a mean value of 1.65 (± 0.16) mmol O₂ kg^?1 fish hr^?1 or 25% (± 2.4). Contrary to Pb and Cd, Cu as CuCl₂ 2H₂O was not precipitated in hard water four days after it was dissolved. Thus T. sparrmanii and other cichlids are shown to be more than an order of magnitude more resistant to Cu as a toxicant than most salmonids.     

Optimization of D-xylose to xylitol biotransformation by Candida guilliermondii cells permeabilized with Triton X-100

Abstract

The effect of NADP⁺ and glucose-6-phosphate (G6P) on the biotransformation of D-xylose to xylitol by cells of Candida guilliermondii permeabilized with surfactant Triton X-100 was evaluated. The experimental runs were performed with 12 g L^?1 of permeabilized cells and a reaction medium composed of Tris–HCl buffer (0.1 M pH 7), D-xylose (57 g L^?1), and MgCl₂.6H₂O (5 mM). The levels of NADP⁺ (from 0.0 to 1.7 mM) and G6P (from 0.00 to 0.17 M) were varied according a 2²-full factorial composed design. Under optimized conditions (NADP⁺ 0.5 mM and 0.05 M G6P), the xylitol volumetric productivity (Q_P) and yield factor (Y_P/S) predicted were 1.86 ± 0.03 g L^?1 h^{? 1} and 0.64 ± 0.03 g g^?1, respectively. These values were 94% and 19% higher than those obtained with unpermeabilized cells under fermentation conditions (0.97 g L^?1 h^?1 and 0.53 g g^?1, respectively). On the basis of the results, it can be concluded that xylitol production by biotransformation with cells of C. guilliermondii permeabilized with Triton X-100 is a promising alternative to the fermentative process.     

Distribution of a model biocontrol agent (Serenade® MAX) in apple and pear by mason bees and bumble bees

1. Biocontrol agents (BCAs) are commonly sprayed on flowering pipfruit trees to prevent them from getting infected by various pathogens. By entomovectoring, BCAs can be directly delivered onto the flowers. However, we currently lack knowledge on the distribution dynamics of BCAs by pollinators.
2. Here, managed bees, both bumble bees (Bombus terrestris) and mason bees (Osmia bicornis and Osmia cornuta), were placed in the vicinity of flowering pipfruit trees (pear -‘Conference’, and apple—‘Svatava’ and ‘Jonagold’), and this allowed us to investigate the distribution of a model BCA, namely, Serenade® MAX, from spray-inoculated flowers of a centralized tree to non-inoculated flowers of surrounding receiver trees by bees in an experimental setup in outdoor conditions.
3. One hour after inoculation, we detected an enrichment of BCA in the flowers of the receiver trees and this for each tested pipfruit.
4. The distribution of BCA from treated to untreated flowers was homogenous between the receiver trees for ‘Svatava’, while significantly different loads were detected for both ‘Conference’ and ‘Jonagold’, which might be due to differences in environmental factors, and/or bee characteristics.
5. More research is needed to understand the distribution dynamics of BCAs by pollinators in field conditions, such as in commercial orchards or crop fields, and how this could result in an efficient control.

     

Ethylene and carbon dioxide production by developing strawberries show a correlative pattern that is indicative of ripening climacteric fruit

Laser photoacoustic spectroscopy continuously quantified the ethylene (C₂H₄) produced by strawberry flowers and fruits developing in planta. C₂H₄ was first detected as flower buds opened and exhibited diurnal oscillations (to approximately 200 pl flower^?1 h^?1) before petal abscission. Exogenous application of silver thiosulphate (STS) to detached flowers inhibited petal abscission and flower senescence. In fruit, C₂H₄ production was maintained at a ‘low level’ (10–60 pl fruit^?1 h^?1) until fruit expanded when levels increased in a diurnal pattern (to 200 pl fruit^?1 h^?1). After expansion, C₂H₄ production declined to a low level until fruit attained the red‐ripe stage for at least 24 h. After this time, C₂H₄ levels increased linearly (no diurnal fluctuation) to approximately 1 nL fruit^?1 h^?1. Twenty‐four hours after the re‐initiation of C₂H₄ production by red fruit, CO₂ levels increased approximately three‐fold, indicative of a respiratory climacteric. STS applied to fruits developing in planta and dissected fruit parts ex situ established that C₂H₄ production is regulated by negative feedback until fruits had expanded. The C₂H₄ produced by red‐ripe fruit was regulated by positive feedback. Anti‐1‐amino‐cyclopropane‐1‐carboxylic acid oxidase IgG localization identified immunoreactive antigens of 40 and 30 kDa (M_r) within the fruit achenes of expanding and red‐ripe fruit. Analysis of dissected fruit showed that seed C₂H₄ accounts for 50% the C₂H₄ that is detectable from ripe fruit.     

Direct plant regeneration from leaf explants of Plumbago species and its genetic fidelity through RAPD markers

In vitro plant regeneration was achieved from leaf explants of Plumbago rosea and Plumbago zeylanica on Murashige & Skoog (1962) medium supplemented with 1.5 mg litre^?1 6‐benzylaminopurine, 0.25 mg litre^?1 indole‐3‐acetic acid, 50 mg litre^?1 adenine sulfate and 3% (w/v) sucrose. The shoot initials developed within 2–3 wk on the leaf margin as well as from the wounds of the leaf. High frequency shoot‐bud regeneration was achieved on similar medium in subsequent subcultures. The semi‐mature leaves produced more shoot‐buds as compared to the younger leaves. Mature leaves did not show any response for shoot bud initiation. More than 85% of the semi‐mature explants produced shoot‐buds per leaf explant within 4 wk of culture. Shoots rooted easily on medium having half‐strength basal Murashige & Skoog (1962) medium supplemented with 0.25 mg litre^?1 indole‐3‐butyric acid and 2% (w/v) sucrose; 84–92% of the in vitro rooted plantlets survived in the greenhouse. The regenerated plantlets appeared morphologically similar to the mother plants. No variation was detected among the regenerated plants by the use of Randomly Amplified Polymorphic DNA (RAPD) markers. This method might be useful for assessing plant improvement programmes.     

Effects of Cadmium,Copper, Lead,and Zinc Contamination on Metal Accumulation by Safflower and Wheat

Accumulation of heavy metals (HMs) in cultivated soils is a continuing environmental problem in many parts of the world. An increase in HM concentration can enhance uptake of toxic metals by crops and enter the human food chain. In this study, the uptake behavior of wheat and safflower was evaluated in a calcareous soil by using 12 undisturbed columns in which half were artificially contaminated. Heavy metals in the form of CdCl₂ (15 mg Cd kg^{? 1}), CuSO₄ (585 mg Cu kg^{? 1}), Pb(NO₃)₂ (117 mg Pb kg^{? 1}), and ZnCl₂ (1094 mg Zn kg^{? 1}) were sprayed on the soil surface and completely mixed in the top 10 cm. The background total concentrations of Cd, Cu, Pb and Zn were 1.6, 29.5, 17.5 and 61.2 mg kg^{? 1}, respectively. After metal application, half of the columns (3 contaminated and 3 uncontaminated) were sown with wheat (Triticum aestivum) and the other half with safflower (Carthamus tinctorious) and grown for 74 days until maturity. After harvesting, soil columns were cut into 10-cm sections and analyzed for HNO₃- and DTPA-extractable metal concentrations. Metal concentrations were also measured in different plant tissues. The results showed that artificial contamination of topsoil decreased the transpiration rate of wheat by 12% and that of safflower by 6%. In contaminated columns, Cd, Cu, Pb, and Zn accumulation in wheat shoot was greater by 8.0-, 1.9-, 3.0-, and 2.1-fold than the control, respectively. Accordingly, these numbers were 46.0-, 1.3-, 1.7-, and 1.6-fold in safflower shoot. Soil contamination with HMs resulted in a 55% decrease in shoot dry matter yield of wheat while it had no significant effect on shoot dry matter of safflower. The normalized water consumption for safflower was therefore not affected by metal contamination (≈ 13 mm H₂O g^{? 1} of dry weight for all safflower and uncontaminated wheat treatments), while contaminated wheat was much less water efficient at about 27 mm H₂O g^{? 1} dry weight. It was concluded that although artificial contamination had a negative effect on wheat growth, it did not affect safflower's normal growth and water efficiency.     

Transition of stable isotope ratios of leaf water under simulated dew formation

Dew formation, a common meteorological phenomenon, is expected to intensify in the future. Dew can influence the H₂¹⁸O and HDO isotopic compositions of leaf water (δ_L), but the phenomenon has been neglected in many experimental and modelling studies. In this study, the dew effect on δ_L was investigated with a dark plant chamber in which dew formation was introduced. The H₂¹⁸O and HDO compositions of water vapour, dew water and leaf water of five species were measured for up to 48 h of dew exposure. Our results show that the exchanges of H₂¹⁸O and HDO in leaf water with the air continued in the darkness when the net H₂¹⁶O flux was zero. Our estimates of the leaf conductance using the isotopic mass balance method ranged from 0.035 to 0.087 mol m^?2 s^?1, in broad agreement of the night‐time stomatal conductance reported in the literature. In our experiments, the conductance of the C₄ species was 0.04 ± 0.01 mol m^?2 s^?1 and that of the C₃ plants was 0.10 ± 0.04 mol m^?2 s^?1. At the end of 16 h dew exposure, 72 (±17) and 94 (±11)% of the leaf water came from dew according to the ¹⁸O and D tracer, respectively.     

Growth of Methanobacterium thermoautotrophicum on H2CO2: High CH4 productivities in continuous culture

The thermophilic methanogenic bacterium, Methanobacterium thermoautotrophicum, was grown on H₂CO₂. In continuous culture, high CH₄ productivities were obtained (288 litres litre⁻¹ day⁻¹) with 96% CH₄ in the effluent gas, i.e. the productivity was twice as high as that obtained previously by other authors, with pure or mixed cultures; the biomass was 3·6 g dry wt litre⁻¹.     

Carbon storage and fluxes in ponderosa pine forests at different developmental stages

We compared carbon storage and fluxes in young and old ponderosa pine stands in Oregon, including plant and soil storage, net primary productivity, respiration fluxes, eddy flux estimates of net ecosystem exchange (NEE), and Biome‐BGC simulations of fluxes. The young forest (Y site) was previously an old‐growth ponderosa pine forest that had been clearcut in 1978, and the old forest (O site), which has never been logged, consists of two primary age classes (50 and 250 years old). Total ecosystem carbon content (vegetation, detritus and soil) of the O forest was about twice that of the Y site (21 vs. 10 kg C m^?2 ground), and significantly more of the total is stored in living vegetation at the O site (61% vs. 15%). Ecosystem respiration (R_e) was higher at the O site (1014 vs. 835 g C m^?2 year^?1), and it was largely from soils at both sites (77% of R_e). The biological data show that above‐ground net primary productivity (ANPP), NPP and net ecosystem production (NEP) were greater at the O site than the Y site. Monte Carlo estimates of NEP show that the young site is a source of CO₂ to the atmosphere, and is significantly lower than NEP(O) by c. 100 g C m^?2 year^?1. Eddy covariance measurements also show that the O site was a stronger sink for CO₂ than the Y site. Across a 15‐km swath in the region, ANPP ranged from 76 g C m^?2 year^?1 at the Y site to 236 g C m^?2 year^?1 (overall mean 158 ± 14 g C m^?2 year^?1). The lowest ANPP values were for the youngest and oldest stands, but there was a large range of ANPP for mature stands. Carbon, water and nitrogen cycle simulations with the Biome‐BGC model suggest that disturbance type and frequency, time since disturbance, age‐dependent changes in below‐ground allocation, and increasing atmospheric concentration of CO₂ all exert significant control on the net ecosystem exchange of carbon at the two sites. Model estimates of major carbon flux components agree with budget‐based observations to within ± 20%, with larger differences for NEP and for several storage terms. Simulations showed the period of regrowth required to replace carbon lost during and after a stand‐replacing fire (O) or a clearcut (Y) to be between 50 and 100 years. In both cases, simulations showed a shift from net carbon source to net sink (on an annual basis) 10–20 years after disturbance. These results suggest that the net ecosystem production of young stands may be low because heterotrophic respiration, particularly from soils, is higher than the NPP of the regrowth. The amount of carbon stored in long‐term pools (biomass and soils) in addition to short‐term fluxes has important implications for management of forests in the Pacific North‐west for carbon sequestration.     

Raman spectra of polypeptides containing L-histidine residues and tautomerism of imidazole side chain

Raman spectra were measured for poly(L -histidine) in H₂O, poly(L -histidine-d₂ and -d₃) in D₂O, L -histidine in H₂O, L -histidine-d₃ (and d₄) in D₂O, and 4-methylimidazole in H₂O with various pH (or pD) values. The Raman scattering peaks observed for these samples were ascribed to the neutral and positively charged imidazole groups on the basis of the spectral changes due to the pH variation and to the deuterium substitution of the imino protons. The vibrational modes of these peaks were deduced from the normal coordinate analysis made on the positively charged and neutral 4-ethylimidazoles. The Raman scattering peaks from the imidazole groups in the neutral form clearly indicate that these imidazole groups exist in the equilibrium between the two tautomeric forms, the 1-N protonated from (tautomer I) and the 3-N protonated one (tautomer II). For example, the breathing vibration of the 1-N protonated form is observed at 1282 cm^?1 for L -histidine and at 1304 cm^?1 for 4-methylimidazole, while the breathing vibration of the 3-N protonated form is observed at 1260 cm^?1 for L -histidine and 4-methylimidazole. From the temperature dependence of the relative intensities of the tautomer I peak to that of the tautomer II, it was concluded that the tautomer I is energetically more stable than the tautomer II, and the ΔH value is 1.0 ± 0.3 kcal/mol for L -histidine and 0.4 ± 0.1 kcal/mol for 4-methylimidazole. Poly(L -histidine) with the neutral imidazole side chains shows the amide I peak at 1672 cm^?1, indicating that the sample assumes the antiparallel pleated-sheet structure. Poly(L -Ala⁷⁵L -His²⁵) and poly(L -Ala⁵⁰L -His⁵⁰) were found to take the α-helical and β-form conformations, respectively.     

Seasonal soil‐surface carbon fluxes from the root systems of young Pinus radiata trees growing at ambient and elevated CO2 concentration

Elevated atmospheric CO₂ concentration may result in increased below‐ground carbon allocation by trees, thereby altering soil carbon cycling. Seasonal estimates of soil surface carbon flux were made to determine whether carbon losses from Pinus radiata trees growing at elevated CO₂ concentration were higher than those at ambient CO₂ concentration, and whether this was related to increased fine root growth. Monthly soil surface carbon flux density (f) measurements were made on plots with trees growing at ambient (350) and elevated (650 μmol mol^?1) CO₂ concentration in large open‐top chambers. Prior to planting the soil carbon concentration (0.1%) and f (0.28 μmol m^?2 s^?1 at 15 °C) were low. A function describing the radial pattern of f with distance from tree stems was used to estimate the annual carbon flux from tree plots. Seasonal estimates of fine root production were made from minirhizotrons and the radial distribution of roots compared with radial measurements of f. A one‐dimensional gas diffusion model was used to estimate f from soil CO₂ concentrations at four depths. For the second year of growth, the annual carbon flux from the plots was 1671 g y^?1 and 1895 g y^?1 at ambient and elevated CO₂ concentrations, respectively, although this was not a significant difference. Higher f at elevated CO₂ concentration was largely explained by increased fine root biomass. Fine root biomass and stem production were both positively related to f. Both root length density and f declined exponentially with distance from the stem, and had similar length scales. Diurnal changes in f were largely explained by changes in soil temperature at a depth of 0.05 m. Ignoring the change of f with increasing distance from tree stems when scaling to a unit ground area basis from measurements with individual trees could result in under‐ or overestimates of soil‐surface carbon fluxes, especially in young stands when fine roots are unevenly distributed.     

Influence of stomatal distribution on transpiration in low-wind environments

Abstract According to computer energy balance simulations of horizontal thin leaves, the quantitative effects of stomatal distribution patterns (top vs. bottom surfaces) on transpiration (E) were maximal for sunlit leaves with high stomatal conductances (g_s) and experiencing low windspeeds (free or mixed convection regimes). E of these leaves decreased at windspeeds > 50 cm s^?1, despite increases in the leaf-to-air vapour density deficit. At 50 cm s^?1 wind-speed, rapidly transpiring leaves had greater E when one-half of the stomata were on each leaf surface (amphistomaty; 10.16 mmol H₂O m^?2 s^?1) than when all stomata were on either the top (hyperstomaty; 9.34 mmol m^?2s^?1) or bottom (hypostomaty; 7.02 mmol m^?2s^?1) surface because water loss occurred in parallel from both surfaces. Hyperstomatous leaves had larger E than hypostomatous leaves because free convection was greater on the top than on the bottom surface. Transpiration of leaves with large g, was greatest at windspeeds near zero when ～60–75% of the stomata were on the top surface, while at high windspeeds E was greatest with, 50% of the stomata on top. For leaves with low g_s, stomatal distribution exerted little influence on simulated E values. Laboratory measurements of water loss from simulated hypo-, hyper-, and amphistomatous leaf models qualitatively supported these predictions.