Expression,subcellular localization,and <Emphasis Type="Italic">cis</Emphasis>-regulatory structure of duplicated phytoene synthase genes in melon (<Emphasis Type="Italic">Cucumis melo</Emphasis> L.)

The emission of molecular iodine (I₂) from the stipe, the meristematic area and the distal blade of the brown macroalga Laminaria digitata (Hudson) Lamouroux (Phaeophyceae) was monitored under low light and dark conditions. Photosynthetic parameters were determined to investigate both the extent of stress experienced by different thallus parts and the effects of emersion on photosynthesis. Immediately after air exposure, intense I₂ emission was detectable from all thallus parts. I₂ emission declined continuously over a period of 180 min following the initial burst, but was not affected by the light regime. The total number of mole of I₂ emitted by stipes was approximately 10 times higher than those emitted from other thallus parts. Initial I₂ emission rates (measured within 30 min of exposure to air) were highest for stipes (median values: 2,999 and 5,222 pmol g⁻¹ dw min⁻¹ in low light and dark, respectively) and lower, by one order of magnitude, for meristematic regions and distal blades. After exposure to air for between 60 and 180 min, I₂ emission rates of all thallus parts were reduced by 70–80%. Air exposure resulted in a decrease of the maximum photosystem II (PSII) efficiency (F _v/F _m) by 3%, and in a 25–55% increase of the effective PSII quantum efficiency ( \Updelta F/F^￠_\textm \Updelta F/F^{\prime}_{\text{m}} ); this was caused by a higher fraction of open reaction centres (q_P), whereas the efficiency of the latter in capturing energy ( F^￠_\textv /F^￠_\textm F^{\prime}_{\text{v}} /F^{\prime}_{\text{m}} ) remained constant. The results indicate the presence of an iodine pool which is easily volatilised and depleted due to air exposure, even under apparently low stress conditions.     

Photosynthetic induction in leaves of co-occurring <Emphasis Type="Italic">Fagus lucida</Emphasis> and <Emphasis Type="Italic">Castanopsis lamontii</Emphasis> saplings grown in contrasting light environments

Photosynthetic induction times and photoinhibition in relation to simulated sunflecks (sudden increase of irradiance from 20 to 1,500 μmol m⁻² s⁻¹) were examined in leaves of co-occurring Fagus lucida (a deciduous tree) and Castanopsis lamontii (an evergreen tree) saplings grown either in a beech forest understory or in an adjacent open site during a late rainy season. Two hypotheses were tested: (1) understory leaves would display faster photosynthetic induction times and greater photoinhibition than open-grown leaves; and (2) evergreen species would have slower photosynthetic induction times and lighter photoinhibition than deciduous species. Times to reach 90% of maximal CO₂ assimilation rate (t _90%A ) and stomatal conductance did not differ between species, but showed faster by 3–5 min in open-grown leaves than understory leaves due to higher initial stomatal conductance (g _{s initial}) and induction state 1 min into simulated sunflecks (IS_1min) in the former. Our analysis across the published data on photosynthetic induction of 48 broad-leaved woody species again revealed the negative correlations between t _90%A and either g _{s initial} or IS_1min, and the similarity of t _90%A and between evergreen and deciduous species. Measurements of maximum PSII photochemical efficiency (F _v/F _m) indicated that photoinhibition occurred in saplings in any of the growth habitats during sunfleck-induced photosynthetic induction. Despite no interspecific differences in the degree of photoinhibition, understory leaves of both species suffered heavier photoinhibition than open-grown leaves, as indicated by a stronger decrease of F _v/F _m in the former. Dynamic changes in the quantum yields of PSII photochemistry and ΔpH- and xanthophyll-regulated thermal dissipation and adjustments in the partitioning of electron flow between assimilative and non-assimilative processes were functional to resist photoinhibition. However, such photoinhibition, together with stomatal and biochemical limitations, would decrease carbon gain during simulated sunflecks, particularly in understory leaves.     

Transition from octahedral to tetrahedral geometry causes the activation or inhibition by Zn<Superscript>2+</Superscript> of <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> phosphorylcholine phosphatase

Pseudomonas aeruginosa phosphorylcholine phosphatase (PchP) catalyzes the hydrolysis of phosphorylcholine, which is produced by the action of hemolytic phospholipase C on phosphatidylcholine or sphyngomielin, to generate choline and inorganic phosphate. Among divalent cations, its activity is dependent on Mg²⁺ or Zn²⁺. Mg²⁺ produced identical activation at pH 5.0 and 7.4, but Zn²⁺ was an activator at pH 5.0 and became an inhibitor at pH 7.4. At this higher pH, very low concentrations of Zn²⁺ inhibited enzymatic activity even in the presence of saturating Mg²⁺ concentrations. Considering experimental and theoretical physicochemical calculations performed by different authors, we conclude that at pH 5.0, Mg²⁺ and Zn²⁺ are hexacoordinated in an octahedral arrangement in the PchP active site. At pH 7.4, Mg²⁺ conserves the octahedral coordination maintaining enzymatic activity. The inhibition produced by Zn²⁺ at 7.4 is interpreted as a change from octahedral to tetrahedral coordination geometry which is produced by hydrolysis of the [ \textZn ²⁺ \textL ₂ ^{- 1} \textL ₂⁰ ( \textH ₂ \textO ) ₂ ] \left[ {{\text{Zn}}^{ 2+ } {\text{L}}_{ 2}^{ - 1} {\text{L}}_{ 2}^{0} \left( {{\text{H}}_{ 2} {\text{O}}} \right)_{ 2} } \right] complex.     

Analysis of the activation mechanism of <Emphasis Type="Italic">Pseudomonas stutzeri</Emphasis> cytochrome <Emphasis Type="Italic">c</Emphasis> peroxidase through an electron transfer chain

The activation mechanism of Pseudomonas stutzeri cytochrome c peroxidase (CCP) was probed through the mediated electrochemical catalysis by its physiological electron donor, P. stutzeri cytochrome c-551. A comparative study was carried out, by performing assays with the enzyme in the resting oxidized state as well as in the mixed-valence activated form, using cyclic voltammetry and a pyrolytic graphite membrane electrode. In the presence of both the enzyme and hydrogen peroxide, the peak-like signal of cytochrome c-551 is converted into a sigmoidal wave form characteristic of an \textE_\textr \textC_\texti^￠ {\text{E}}_{\text{r}} {\text{C}}_{\text{i}}^{\prime } catalytic mechanism. An intermolecular electron transfer rate constant of (4 ± 1) × 10⁵ M⁻¹ s⁻¹ was estimated for both forms of the enzyme, as well as a similar Michaelis–Menten constant. These results show that neither the intermolecular electron transfer nor the catalytic activity is kinetically controlled by the activation mechanism of CCP in the case of the P. stutzeri enzyme. Direct enzyme catalysis using protein film voltammetry was unsuccessful for the analysis of the activation mechanism, since P. stutzeri CCP undergoes an undesirable interaction with the pyrolytic graphite surface. This interaction, previously reported for the Paracoccus pantotrophus CCP, induces the formation of a non-native conformation state of the electron-transferring haem, which has a redox potential 200 mV lower than that of the native state and maintains peroxidatic activity.     

Cell-to-cell pathway dominates xylem-epidermis hydraulic connection in<Emphasis Type="Italic"> Tradescantia fluminensis</Emphasis> (Vell. Conc.) leaves

A steady supply of water is indispensable for leaves to fulfil their photosynthetic function. Understanding water movement in leaves, especially factors that regulate the movement of water flux from xylem to epidermis, requires that the nature of the transport pathway be elucidated. To determine the hydraulic linkage between xylem and epidermis, epidermal cell turgor pressure (P _t) in leaves of Tradescantia fluminensis was monitored using a cell pressure probe in response to a 0.2 MPa step change in xylem pressure applied at the leaf petiole. Halftime of P _t changes were 10–30 times greater than that of water exchange across an individual cell membrane suggesting that cell-to-cell water transport constitutes a significant part of the leaf hydraulic path from xylem to epidermis. Furthermore, perfusion of H₂O₂ resulted in increases of both and by a factor of 2.5, indicating that aquaporins may play a role in the xylem to epidermis hydraulic link. The halftime for water exchange did not differ significantly between cells located at the leaf base (2.5 s), middle (2.6 s) and tip (2.5 s), indicating that epidermal cell hydraulic properties are similar along the length of the leaf. Following the pressure application to the xylem (0.2 MPa), P _t changed by 0.12, 0.06 and 0.04 MPa for epidermal cells at the base, middle and the tip of the leaf, respectively. This suggests that pressure dissipation between xylem and epidermis is significant, and that the pressure drop along the vein may be due to its structural similarities to a porous pipe, an idea which was further supported by measurements of xylem hydraulic resistance using a perfusion technique.     

Expression of yeast <Emphasis Type="Italic">Hem1</Emphasis> controlled by <Emphasis Type="Italic">Arabidopsis HemA1</Emphasis> promoter enhances leaf photosynthesis in transgenic tobacco

A gene encoding aminolevulinate synthase (ALA-S) in yeast (Saccharomyces cerevisiae YHem1) was introduced into the genome of tobacco (Nicoliana tabacum) under the control of Arabidopsis thaliana HemA1 gene promoter (AtHemA1 P). All transgenic lines transcribed the YHem1 gene, especially under light condition. The capacity to synthesize ALA and therefore chlorophyll was increased in transformed plants. Determination of gas exchange suggested that transgenic plants had significantly higher level of net photosynthetic rate (P _n ), stomatal conductance (G _s ) and transpiration rate (T _r ), compared to the wild type (WT). Analysis with a modulated chlorophyll fluorometer demonstrated that the genetic transformation also caused a significant increase in photochemical efficiency of PSII (F^￠_v /F^￠_m F^{\prime}_{v} /F^{\prime}_{m} ), actual photochemical efficiency (Ф _PSII ), photochemical quenching (qP), electron transfer rate (ETR) and the energy proportion in photochemistry (Pc), but decrease in proportion in heat dissipation (Hd). Chlorophyll-a fast fluorescence measurement and JIP-test indicated that photosynthetic performance index on cross section basis (PI _CS ) and electron transport flux (ET _o /CS) of transgenic tobacco were increased remarkably. And the probability that a trapped exciton can move a electron into the electron transport chain beyond Q _A ⁻ (Ψ _o ) and the density of active reaction centers (RC/CS) were also increased obviously in transgenic tobacco. These results imply that transgenic tobacco plants expressing YHem1 gene had higher photosynthetic capacity and energy conversion efficiency than the WT plants.     

Population genetics of <Emphasis Type="Italic">Collisella subrugosa</Emphasis> (Patellogastropoda: Acmaeidae): evidence of two scales of population structure

Marine invertebrate populations usually show high levels of genetic variability that has frequently been associated with spatial and temporal environmental heterogeneity. One of the most heterogeneous marine environments is the intertidal zone, the habitat of Collisella subrugosa, the most widespread and abundant Brazilian limpet. C. subrugosa has planktonic larvae that can disperse over long distances, what can promote gene flow among shores, working against interpopulational differentiation. In this study we investigated the genetic variability and populational substructure of C. subrugosa through analysis of 24 allozyme loci in 14 samples (590 individuals) collected along 2,700 km of the Brazilian coast. The genetic variability was high ( and ), as expected for intertidal species. Genetic differentiation among samples was low (F _ST = 0.03) what may reflect intensive gene flow associated with larval dispersal. However, we detected an isolation-by-distance pattern of population substructure in one sampled region. High levels of heterozygote deficiency were also observed for many loci in each sample. Alternative hypothesis are discussed, and the “breeding groups” is suggested to explain these pattern, indicating the main cause as environmental heterogeneity.     

Life history of the nonnative convict cichlid <Emphasis Type="Italic">Amatitlania nigrofasciata</Emphasis> in the Haebaru Reservoir on Okinawa-jima Island,Japan

Life history parameters associated with reproductive biology, age, and growth of the convict cichlid (also known as the zebra cichlid) Amatitlania nigrofasciata, which was introduced into the Haebaru Reservoir on Okinawa-jima Island, were estimated using 437 specimens that ranged from 13.7 to 82.9 mm standard length (SL). Lengths of females at first maturity (SL) and 50% maturity (L ₅₀) were estimated to be 32.2 and 37.3 mm SL, respectively. The spawning period continued throughout the year, with a peak spawning cycle from March to May 2006–2007. Observations of postovulatory follicles and tertiary yolk stage oocytes indicate that convict cichlids spawn multiple times within a year. Female cichlids that hatched during the peak spawning seasons matured after October of the same year. Batch fecundity of females (32.2–61.2 mm SL) ranged from 65 to 345 (mean ± SD = 155 ± 63). Opaque zones along the outer margins of otoliths formed annually. The maximum age of male and female cichlids was 3 years. The von Bertalanffy growth formulae (VBGF) were expressed as L_t = 57.4( 1 - e ^{- 0.78( t + 0.91 )} ) {{\hbox{L}}_{\rm{t}}}{ = 57}{.4}\left( {1 - {e^{ - 0.78\left( {t + 0.91} \right)}}} \right) for females and L_t = 69.5( 1 - e ^{- 1.07( t + 0.24 )} ) {{\hbox{L}}_{\rm{t}}}{ = 69}{.5}\left( {1 - {e^{ - 1.07\left( {t + 0.24} \right)}}} \right) for males. Males grew larger than females beginning from the first year. Certain life history characteristics, such as year-round spawning and early maturation, probably contributed to the successful establishment of the convict cichlid, and this species in particular is thought to adapt and become established quickly upon introduction to freshwater systems on Okinawa-jima Island.     

Anaerobic growth and potential for amino acid production by nitrate respiration in <Emphasis Type="Italic">Corynebacterium glutamicum</Emphasis>

Oxygen limitation is a crucial problem in amino acid fermentation by Corynebacterium glutamicum. Toward this subject, our study was initiated by analysis of the oxygen-requiring properties of C. glutamicum, generally regarded as a strict aerobe. This organism formed colonies on agar plates up to relatively low oxygen concentrations (0.5% O₂), while no visible colonies were formed in the absence of O₂. However, in the presence of nitrate (), the organism exhibited limited growth anaerobically with production of nitrite (), indicating that C. glutamicum can use nitrate as a final electron acceptor. Assays of cell extracts from aerobic and hypoxic cultures yielded comparable nitrate reductase activities, irrespective of nitrate levels. Genome analysis revealed a narK2GHJI cluster potentially relevant to nitrate reductase and transport. Disruptions of narG and narJ abolished the nitrate-dependent anaerobic growth with the loss of nitrate reductase activity. Disruption of the putative nitrate/nitrite antiporter gene narK2 did not affect the enzyme activity but impaired the anaerobic growth. These indicate that this locus is responsible for nitrate respiration. Agar piece assays using l-lysine- and l-arginine-producing strains showed that production of both amino acids occurred anaerobically by nitrate respiration, indicating the potential of C. glutamicum for anaerobic amino acid production.     

A new medium formulation for <Emphasis Type="Italic">in vitro</Emphasis> rooting of carob tree based on leaf macronutrients concentrations

Experiments were performed to optimize the macronutrients concentrations for in vitro rooting of Ceratonia siliqua micropropagated shoots. Several dilutions of Murashige and Skoog (MS) medium were tested: full-strength MS, half-strength MS ( MS), and MS + full N. The frequency of in vitro rooting was enhanced when the MS was used (50 % rooted shoots). Mature leaves from 20 – 30 year-old carob trees and from 2 year-old micropropagated plants were collected and the concentrations of macronutrients (N, P, K, Ca, Mg) assessed. Based on the mineral composition of the leaves a new medium was formulated and compared with the previous ones showing an increment of the rooting frequency to 80 %. Moreover, shoots rooted in the new medium did not show symptoms of apical necrosis that occurred in the other tested media.     

Secondary production,calcification and CO<Subscript>2</Subscript> fluxes in the cirripedes <Emphasis Type="Italic">Chthamalus montagui</Emphasis> and <Emphasis Type="Italic">Elminius modestus</Emphasis>

Calcification, a process common to numerous marine taxa, has traditionally been considered to be a significant source of CO₂ in tropical waters only. A number of relatively recent studies, however, have shown that significant amounts of CO₂ are also produced in temperate waters, although none of these studies was carried out on rocky shores, which are considered to be very productive systems. We compared the CO₂ fluxes due to respiration and calcification in two temperate species, the cirripedes Chthamalus montagui and Elminius modestus. The population dynamics of both species were estimated at two sites during a 1-year experimental period in order to establish mean organic (ash-free dry weight) and CaCO₃ (dry shell weight) production. Based on these parameters, we estimated the CO₂ fluxes due to respiration and calcification. CaCO₃ production was estimated to be 481.0 and at each site, representing 3.4 and respectively, of released CO₂. These fluxes represent each 47% of the CO₂ released as a result of respiration and calcification. The production of CaCO₃ at the high-density site was: (1) among the highest values obtained for temperate organisms, and (2) comparable to the estimated CO₂ fluxes for coral reefs. As calcifying organisms are well represented in temperate ecosystems in terms of both density and biomass, our results provide clear evidence that calcification of temperate organisms should not be underestimated. Additional studies on other rocky shore taxa are needed before the relative importance of calcification in rocky intertidal carbon budgets can be generalized.     

Cardiorespiratory responses to hypoxia in the African catfish, <Emphasis Type="Italic">Clarias gariepinus</Emphasis> (Burchell 1822), an air-breathing fish

The African catfish, Clarias gariepinus, possesses a pair of suprabranchial chambers located in the dorsal-posterior part of the branchial cavity having extensions from the upper parts of the second and fourth gill arches, forming the arborescent organs. This structure is an air-breathing organ (ABO) and allows aerial breathing (AB). We evaluated its cardiorespiratory responses to aquatic hypoxia. To determine the mode of air-breathing (obligate or accessory), fish had the respiratory frequency (f _R) monitored and were subjected to normoxic water (PwO₂ = 140 mmHg) without becoming hyperactive for 30 h. During this period, all fish survived without displaying evidences of hyperactivity and maintained unchanged f _R, confirming that this species is a facultative air-breather. Its aquatic O₂ uptake ( [(V)\dot]\textO₂ \dot{V}{\text{O}}_{2} ) was maintained constant down to a critical PO₂ (PcO₂) of 60 mmHg, below which [(V)\dot]\textO₂ \dot{V}{\text{O}}_{2} declined linearly with further reductions of inspired O₂ tension (PiO₂). Just above the PcO₂ the ventilatory tidal volume (V _T) increased significantly along with gill ventilation ( [(V)\dot]_\textG \dot{V}_{\text{G}} ), while f _R changed little. Consequently, the water convection requirement ( [(V)\dot]_\textG /[(V)\dot]\textO₂ ) \left( {\dot{V}_{\text{G}} /\dot{V}{\text{O}}_{2} } \right) increased steeply. This threshold applied to a cardiac response that included reflex bradycardia. AB was initiated at PiO₂ = 140 mmHg (normoxia) and air-breathing episodes increased linearly with more severe hypoxia, being significantly higher at PiO₂ tensions below the PcO₂. Air-breathing episodes were accompanied by bradycardia pre air-breath, to tachycardia post air-breath.     

Genetic diversity,genetic drift and mixed mating system in small subpopulations of <Emphasis Type="Italic">Dyckia ibiramensis</Emphasis>, a rare endemic bromeliad from Southern Brazil

Dyckia ibiramensis is a naturally rare, endemic and threatened bromeliad which occurs naturally on 4 km of rocky river outcroppings in Southern Brazil. For this study, subpopulations of the species were characterized based on size and genetics, to compile information for in situ and ex situ conservation strategies. A census of the rosettes was undertaken for each subpopulation and seven allozyme polymorphic loci were used to estimate genetic diversity and structure of adults and offspring and assess the mating system. In general, the subpopulations were small and most of the rosettes were aggregated into clumps. The species showed a high genetic diversity ([^(H)]_e = 0.219 \hat{H}_{e} = 0.219 ) and significant fixation index ([^(f)] = 0.642, \hat{f} = 0.642, P ≤ 0.05). The estimate of differentiation among all adult subpopulations indicate pronounced genetic structure ([^(G)]^￠_ST = 0.674 \hat{G}^{\prime}_{ST} = 0.674 ). D. ibiramensis has a mixed mating system and multilocus outcrossing rates [^(t)]_m \hat{t}_{m} were variable between subpopulations. This study demonstrates the importance of in situ preservation of all subpopulations for the maintenance of species diversity. For effective ex situ conservation, it would be necessary to collect seeds from 52 to 99 seed-rosettes, depending on the target population.     

Nitric oxide promotes in vitro organogenesis in <Emphasis Type="Italic">Linum usitatissimum</Emphasis> L.

The effects of nitric oxide (NO) on caulogenesis, shoot organogenesis and rhizogenesis from hypocotyl explants of Linum usitatissimum were investigated. Exogenously supplied NO donors, 5 μM sodium nitroprusside (SNP), 2 μM S-nitroso-N-acetylpenicillamine (SNAP) and 2 μM 3-morpholinosydnonimine (SIN-1), significantly promoted shoot differentiation from the hypocotyl explants of L. usitatissimum excised from its in vitro raised seedlings. Potassium ferrocyanide, a structural analogue of SNP, lacking NO group, did not promote shoot organogenesis. Likewise, products of NO, \textNO₂ ^- {\text{NO}}_{2}^{ - } and \textNO₃ ^- {\text{NO}}_{3}^{ - } supplied as 5 μM NaNO₂ and 5 μM NaNO₃ did not enhance shoot differentiation. Another source of NO, a mixture of sodium nitrite (SN) provided along with ascorbic acid (AsA), also caused significant promotion in the average number of shoots per responding explant. SNP also augmented the rhizogenic response of the microshoots in terms of percentage of responding explants, number of roots per responding explant and average root length. The NO scavengers, 2-(4-carboxy-phenyl)-4, 4, 5, 5-tetramethylimideazoline-1-oxyl-3-oxide (cPTIO) or methylene blue (MB), provided along with SNP, SNAP, SIN-1 or SN + AsA, at concentrations equimolar to the optimum concentration of the donors, reversed the promotory influence, thereby, confirming the role of NO in promotion of in vitro morphogenesis. However, NO scavengers individually did not affect the observed morphogenic processes. Morphological and histological studies of hypocotyl segments cultured on BM or BM + SNP for 4, 8 and 12 days demonstrated that SNP enhanced shoot differentiation by inducing a higher number of shoot primordia, each of which develops into a single shoot.     

Phenol biodegradation by the thermoacidophilic archaeon <Emphasis Type="Italic">Sulfolobus solfataricus</Emphasis> 98/2 in a fed-batch bioreactor

Toxic at low concentrations, phenol is one of the most common organic pollutants in air and water. In this work, phenol biodegradation was studied in extreme conditions (80°C, pH = 3.2) in a 2.7 l bioreactor with the thermoacidophilic archaeon Sulfolobus solfataricus 98/2. The strain was first acclimatized to phenol on a mixture of glucose (2000 mg l⁻¹) and phenol (94 mg l⁻¹) at a constant dissolved oxygen concentration of 1.5 mg l⁻¹. After a short lag-phase, only glucose was consumed. Phenol degradation then began while glucose was still present in the reactor. When glucose was exhausted, phenol was used for respiration and then for biomass build-up. After several batch runs (phenol < 365 mg l⁻¹), specific growth rate (μ_X) was 0.034 ± 0.001 h⁻¹, specific phenol degradation rate (q_P) was 57.5 ± 2 mg g⁻¹ h⁻¹, biomass yield (Y_X/P) was 52.2 ± 1.1 g mol⁻¹, and oxygen yield factor ( \textY_{\textX/\textO 2} ) \left( {{\text{Y}}_{{{\text{X}}/{\text{O}}_{ 2} }} } \right) was 9.2 ± 0.2 g mol⁻¹. A carbon recovery close to 100% suggested that phenol was exclusively transformed into biomass (35%) and CO₂ (65%). Molar phenol oxidation constant ( \textY_{\textO 2 /\textP} ) \left( {{\text{Y}}_{{{\text{O}}_{ 2} /{\text{P}}}} } \right) was calculated from stoichiometry of phenol oxidation and introducing experimental biomass and CO₂ conversion yields on phenol, leading to values varying between 4.78 and 5.22 mol mol⁻¹. Respiratory quotient was about 0.84 mol mol⁻¹, very close to theoretical value (0.87 mol mol⁻¹). Carbon dioxide production, oxygen demand and redox potential, monitored on-line, were good indicators of growth, substrate consumption and exhaustion, and can therefore be usefully employed for industrial phenol bioremediation in extreme environments.     

Applicability of <Emphasis Type="Italic">Penicillium</Emphasis><Emphasis Type="Italic">chrysogenum</Emphasis> rheological correlations to broths of other fungal strains

Existing correlations of Power law consistency index with Penicillium chrysogenum biomass concentration and morphology were revised using a microscope magnification of 50 times to characterize the latter, rather than the 80 times used previously. This allowed tests of the correlations on broths of Aspergillus oryzae and Aspergillus niger, which have such large mycelial sizes that a lower magnification is required for accurate morphological analysis. The new correlations were successful at predicting the rheology of A. oryzae broths but not A. niger broths, which may be because of a change in the exponent on the biomass concentration in the correlations for the latter. Because the mean maximum dimension of clumps is magnification independent, the preferred correlation was:

An investigation of the peroxidase activity of <Emphasis Type="Italic">Vitreoscilla</Emphasis> hemoglobin

In order to investigate the ability of the Vitreoscilla hemoglobin (VHb) to act as a peroxidase, the protein was overexpressed in Escerichia coli and purified using a 6xHis-tag. The peroxidase activity of VHb was studied using 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), ferrocene carboxylic acid (FcCOOH) dopamine and l-dopa as substrates. The effects of external agents such as pH, salt concentration/ionic strength, and the thermal stability of VHb on the catalytic activity were assessed. The optimum pH for VHb using ABTS as a substrate was estimated to be 6–7. The VHb protein proved to be stable up to 80 °C, as judged by its peroxidase activity. Furthermore, NaCl concentrations up to 100 mM did not exert any significant effect on the activity. The catalytic activity against ABTS and FcCOOH was similar to that measured for horseradish peroxidase, whereas in the case of the phenolic substrates dopamine and l-dopa the activity was several orders of magnitude lower. The Michaelis constants, were in good agreement with the data for human and bovine hemoglobin. No activity could be detected for the negative controls lacking VHb. These results demonstrate that VHb exhibits peroxidase activity, a finding in line with the hypothesis that VHb has cellular functions beyond the role as an oxygen carrier. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Malin Kvist and Ekaterina S. Ryabova contributed equally to this work.     

Nitrate and phosphate removal by<Emphasis Type="Italic"> Spirulina platensis</Emphasis>

The cyanobacterium Spirulina platensis was used to verify the possibility of employing microalgal biomass to reduce the contents of nitrate and phosphate in wastewaters. Batch tests were carried out in 0.5 dm³ Erlenmeyer flasks under conditions of light limitation (40 mol quanta m^–2 s^–1) at a starting biomass level of 0.50 g/dm³ and varying temperature in the range 23–40°C. In this way, the best temperature for the growth of this microalga (30°C) was determined and the related thermodynamic parameters were estimated. All removed nitrate was used for biomass growth (biotic removal), whereas phosphate appeared to be removed mainly by chemical precipitation (abiotic removal). The best results in terms of specific and volumetric growth rates ( =0.044 day^–1, Q _x =33.2 mg dm^–3 day^–1) as well as volumetric rate and final yield of nitrogen removal ( =3.26 mg dm^–3 day^–1, =0.739) were obtained at 30°C, whereas phosphorus was more effectively removed at a lower temperature. In order to simulate full-scale studies, batch tests of nitrate and phosphate removal were also performed in 5.0 dm³ vessels (mini-ponds) at the optimum temperature (30°C) but increasing the photon fluence rate to 80 mol quanta m^–2 s^–1 and varying the initial biomass concentration from 0.25 to 0.86 g/dm³. These additional tests demonstrated that an increase in the inoculum level up to 0.75 g/dm³ enhanced both NO₃ ^– and PO₄ ^3– removal, confirming a strict dependence of these processes on biomass activity. In addition, the larger surface area of the ponds and the higher light intensity improved removal yields and kinetics compared to the flasks, particularly concerning phosphorus removal ( =0.032–0.050 day^–1, Q _x =34.7–42.4 mg dm^–3 day^–1, =3.24–4.06 mg dm^–3 day^–1, =0.750–0.879, =0.312–0.623 mg dm^–3 day^–1, and =0.224–0.440).     

Effects of low night temperature on pigments,chl <Emphasis Type="Italic">a</Emphasis> fluorescence and energy allocation in two bitter gourd (<Emphasis Type="Italic">Momordica charantia</Emphasis> L.) genotypes

Using two different inbred lines of Momordica charantia (bitter gourd), Y-106-5 and Z-1-4, the cell membrane stability, leaf water potential, pigment contents and the chlorophyll a fluorescence were investigated with different low night temperature (LNT) treatments over a 7 day time period and the sequent a 7 day recovery. Under LNT treatments, electrolyte leakage increased in both inbred lines and it increased more significantly in Y-106-5 plants than that in Z-1-4. The content of Chl b and total Chl decreased, while the Chl a/b ratio increased in stressed plants of the two lines. Almost all LNT treatments induced little change in Chl a content in Z-1-4 whereas obvious decreases in 5 and 8°C treated Y-106-5 plants were observed. Chilling changed the water status of plants and induced decreases of leaf water potential (LWP) in 5 and 8°C treated plants. LNT treatments also resulted in changes in the chlorophyll fluorescence parameters in bitter gourd leaves. The potential PSII activity (F _v/F _o) was reduced obviously by LNT stress and showed more sensitive to LNT than the maximum quantum efficiency of PSII primary photochemistry (F _v/F _m). The efficiency of open PSII centers exhibited a slight decrease whereas the photochemical quenching efficient (q _P) was affected more seriously by LNT stress in both two inbred lines. The allocation of energy was rearranged by LNT stress. The light fraction used for PSII photochemistry (P) was reduced, while that used for heat dissipation (D) and the third fraction of absorbed light defines excess energy (E) increased due to the chilling stress. The impacts of LNT stress on bitter gourd generally increased with the number of LNT chilling and the severe night chilling. Plants were little affected by 12°C night chilling and the most acute damage was found in 5°C night chilling treatments. A 7 day recovery mitigated the adverse effects of LNT for both lines and almost all LNT treated plants restored to control levels except 5°C night chilling treated Y-106-5 plants. The two lines have a variance in tolerance to LNT stress and display obvious differences of phenotypes under extreme conditions.     

Nitrogen sink strength of ectomycorrhizal morphotypes of <Emphasis Type="Italic">Quercus douglasii</Emphasis>, <Emphasis Type="Italic">Q. garryana</Emphasis>, and <Emphasis Type="Italic">Q. agrifolia</Emphasis> seedlings grown in a northern California oak woodland

Little information is known on what the magnitude of nitrogen (N) processed by ectomycorrhizal (ECM) fungal species in the field. In a common garden experiment performed in a northern California oak woodland, we investigated transfer of nitrogen applied as ¹⁵NH₄ or ¹⁵NO₃ from leaves to ectomycorrhizal roots of three oak species, Quercus agrifolia, Q. douglasii, and Q. garryana. Oak seedlings formed five common ectomycorrhizal morphotypes on root tips. Mycorrhizal tips were more enriched in ¹⁵N than fine roots. N transfer was greater to the less common morphotypes than to the more common types. ¹⁵N transfer from leaves to roots was greater when , not , was supplied. ¹⁵N transfer to roots was greater in seedlings of Q. agrifolia than in Q. douglasii and Q. garryana. Differential N transfer to ectomycorrhizal root tips suggests that ectomycorrhizal morphotypes can influence flows of N from leaves to roots and that mycorrhizal diversity may influence the total N requirement of plants.