Localization of sulfate reduction in planted and unplanted rice field soil

Rates of in situ sulfate reduction (SRR) in planted and unplanted rice fieldsoil were measured by the ³⁵SO^2– ₄-radiotracermethod using soil microcosms. The concentration of ³⁵SO^2– ₄ decreased exponentially with time.However, time course experiments indicated that incubation times of10–30 min were appropriate for measurements of SRRusing a single time point in routine assays. Unplanted microcosmsshowed high SRR of 177 nmol cm^-3 d^-1 inthe uppermost centimeter where average sulfate concentrations were<33 µM. Fine scaled measurements (1 mmresolution) localized highest SRR (<100 nmol cm^-3d^-1) at the oxic/anoxic interface at 2–5 mmdepth. In planted rice field soil, SRR of <310 nmolcm^-3 d^-1 were observed at 0–2cm depth. Sulfate reduction rates were determined at a millimeter-scalewith distance to a two dimensional root compartment. The SRR was highestat 0–1.5 mm distance to the root layer with rates up to500 nmol cm^-3 d^-1, indicating a highstimulation potential of the rice roots. SRR seemed to be mainlydependent on the in situ sulfate porewater concentrations. At thesoil surface of unplanted microcosms sulfate concentration decreasedfrom <150 µM to <10 µM within the first 8 mm of depth. In planted microcosmssulfate concentration varied from 87–99 µMsulfate at the 0–3 mm distance to the root layer to48–62 µM sulfate at a root distance>4 mm from the roots.The depth distribution of inorganic sulfur compounds was determinedfor planted and unplanted rice field soil. Sulfate, acid volatilesulfide (AVS) and chromium reducible sulfide (CRS) were up to 20 foldhigher in planted than in unplanted microcosms. CRS was the majorinsoluble sulfur fraction with concentrations >1.7µmol cm^-3. Organic sulfur accounted for25–46% of the total sulfurpresent (269 µg/g dw) in an unplanted microcosm.The biogeochemical role of sulfate reduction forshort-term accumulation of inorganic sulfur compounds(FeS, FeS_{_2} and S°) in rice soil wasdetermined in a time course experiment with incubationperiods of 5, 10, 20, 30 and 60 min. The relativedistribution of CRS and AVS formation showedlittle depth dependence, whereas the formation of³⁵S° seemed to be the highest in themore oxidized upper soil layers and near the root surface.AV³⁵S was the first major product of sulfatereduction after 20–30 min, whereas CR³⁵Swas formed, as AV³⁵S and ³⁵S°decreased, at longer incubation periods of >30 min.     

Hepatitis C Virus Infection-Associated Markers in Sera from Blood Donors in Surabaya,Indonesia

Among 2,233 sera obtained from volunteer blood donors, 259 (11.6%) showed elevated alanine aminotransferase (ALT) levels. A second-generation enzyme-linked immunosorbent assay (ELISA) revealed that 23 (8.9%) of the 259 sera were positive for antibodies against hepatitis C virus (HCV), whereas only 9 (1.4%) of 646 sera randomly collected from blood donors with normal ALT levels were positive (P<0.001). The overall prevalence of anti-HCV antibodies among blood donors was estimated to be 2.3%. HCV RNA was detected in 19 (83%) of the 23 anti-HCV-positive sera with elevated ALT levels, and 8 (89%) of the 9 sera with normal ALT levels. Among the anti-HCV-positive sera, IgM anti-HCV was detected in 5 (22%) of 23 sera with elevated ALT levels and in 2 (22%) of 9 sera with normal ALT levels. All of the IgM anti-HCV-positive sera were positive for HCV RNA, irrespective of ALT levels.     

Transformation of carbon tetrachloride under sulfate reducing conditions

The removal of carbon tetrachloride under sulfate reducing conditions was studied in an an aerobic packed-bed reactor. Carbon tetrachloride, up to a concentration of 30 μM, was completely converted. Chloroform and dichloromethane were the main transformation products, but part of the carbon tetrachloride was also completely dechlorinated to unknown products. Gram-positive sulfate-reducing bacteria were involved in the reductive dechlorination of carbon tetrachloride to chloroform and dichloromethane since both molybdate, an inhibitor of sulfate reduction, and vancomycin, an inhibitor of gram-positive bacteria completely inhibited carbon tetrachloride transformation. Carbon tetrachloride transformation by these bacteria was a cometabolic process and depended on the input of an electron donor and electron acceptor (sulfate). The rate of carbon tetrachloride transformation by sulfate reducing bacteria depended on the type of electron donor present. A transformation rate of 5.1 nmol·ml^-1·h^-1 was found with ethanol as electron donor. At carbon tetrachloride concentrations higher than18 μM, sulfate reduction and reductive dechlorination of carbon tetrachloride decreased and complete inhibition was observed at a carbon tetrachloride concentration of 56.6 μM. It is not clear what type of microorganisms were involved in the observed partial complete dechlorination of carbon tetrachloride. Sulfate reducing bacteria probably did not play a role since inhibition of these bacteria with molybdate had no effect on the complete dechlorination of carbon tetrachloride. This revised version was published online in August 2006 with corrections to the Cover Date.     

三种林分生物量估算方法的比较

区域森林生物量的估算方法是人们目前关注的焦点,建立林分生物量模型成为一种趋势.本文以吉林省落叶松人工林固定样地为例,采用非线性似乎不相关回归法构建2种林分生物量模型,即基于林分变量的林分生物量模型(模型系统Ⅰ)和基于生物量换算系数的林分生物量模型(模型系统Ⅱ),给出落叶松人工林固定生物量换算系数值,并比较了3种林分生物量估算方法的预估精度.结果表明: 所建立的2种林分生物量模型中,总生物量和树干生物量模型拟合和预测效果较好,其R_a²>0.95,且均方根误差(RMSE)、平均预测误差(MPE)和平均绝对误差(MAE)都较小.树叶和树枝生物量模型拟合和预测效果相对较差,其模型的R_a²<0.95.模型系统Ⅰ和模型系统Ⅱ的预测精度均优于固定生物量换算系数法.基于生物量换算系数的林分生物量模型属于材积源生物量法,其本质与基于林分变量的林分生物量模型不同,但二者的预测效果相当.固定生物量换算系数的预测能力较差,将生物量与蓄积量之比假定为恒定常数是不恰当的.此外,为了使模型参数估计更有效,所建立的生物量模型应当考虑林分总生物量及各分项生物量的可加性.     

The Mendelian inheritance of rare flesh and shell colour variants in the black‐lipped pearl oyster (Pinctada margaritifera)

Pinctada margaritifera is French Polynesia's most economically important aquaculture species. This pearl oyster has the specific ability to produce cultured pearls with a very wide range of colours, depending on the colour phenotypes of donor oysters used. Its aquaculture is still based on natural spat collection from wild stocks. We investigated three rare colour variants of P. margaritifera – orange flesh, and red and white shell colour phenotypes – in comparison with the wild‐type black flesh and shell commonly found in this species. The study aimed to assess the geographic distribution and genetic basis of these colour variants. Colour frequencies were evaluated during transfer and graft processes of pearl oyster seed captured at collector stations. Among the collection locations studied, Mangareva Island showed the highest rate of the orange flesh phenotype, whereas Takaroa and Takume atolls had relatively high rates of red and white shell phenotypes respectively. Broodstocks were made of these rare colour variants, and crosses were performed to produce first‐ and second‐generation progenies to investigate segregation. The results were consistent with Mendelian ratios and suggest a distinct model with no co‐dominance: (i) a two‐allele model for flesh trait, whereby the orange allele is recessive to the black fleshed type, and (ii) a three‐allele model for shell trait, whereby the black wild‐type allele is dominant to the red coloration, which is dominant to the white shell. Furthermore, the proposed model provides the basis for producing selected donor pearl oyster lines through hatchery propagation.     

Structure Evolution of Oligomer Fused‐Ring Electron Acceptors toward High Efficiency of As‐Cast Polymer Solar Cells

The structure evolution of oligomer fused‐ring electron acceptors (FREAs) toward high efficiency of as‐cast polymer solar cells (PSCs) is reported. First, a series of FREAs (IC‐(1‐3)IDT‐IC) based on indacenodithiophene (IDT) oligomers as cores are designed and synthesized, effects of IDT number (1–3) on their basic optical and electronic properties are investigated, and more importantly, the relationship between device performance of as‐cast PSCs and donor(D)/acceptor(A) matching (absorption, energy level, morphology, and charge transport) of IC‐(1‐3)IDT‐IC acceptors and two representative polymer donors, PTB7‐Th and PDBT‐T1 is surveyed. Then, the most promising D/A system (PDBT‐T1/IC‐1IDT‐IC) with the best D/A harmony among the six D/A combinations, which yields a power conversion efficiency (PCE) of 7.39%, is found. Finally, changing the side‐chains in IC‐1IDT‐IC from alkylphenyl to alkyl enhances the PCE from 7.39% to 9.20%.     

Purification of Photosystem II particles from Phormidium laminosum using the detergent dodecyl-β-d-maltoside. Properties of the purified complex

The purification and properties of a new oxygen-evolving Photosystem (PS) II particle from the thermophilic blue-green alga Phormidium laminosum are described. The activity of the lauryldimethylamine N-oxide PS II-enriched supernatant described previously (Stewart, A.C. and Bendall, D.S. (1979) FEBS Lett. 107, 308–312) was found to be stabilized for several days at 4°;C by the addition of a second detergent, dodecyl-β-d-maltoside (lauryl maltoside). The lauryl maltoside/lauryldimethylamine N-oxide extract could be fractionated by sucrose density gradient centrifugation. Very high rates of oxygen evolution, typically 1900–2400 μmol O₂/mg chlorophyll a per h at pH 7 with dimethylbenzoquinone and ferricyanide as acceptors, were observed for the lowest green band from the gradient. This fraction contained cytochromes b-559 (high-potential) and c-549, but was completely devoid of P-700 and cytochromes b-563 and f. The purified oxygen-evolving particles comprised seven major polypeptides (M_r 58 900, 52 400, 43 200, 33 900, 30 000, 16 000 and 15 000) and approximately five minor polypeptides. The particles contained 3–4 Mn atoms per reaction centre and had a chlorophyll antenna of approx. 50 chlorophyll a. The fast phase of fluorescence induction curves in the presence of hydroxylamine and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) could be described by an exponential, suggesting that no energy transfer was occurring between the PS II units responsible for this phase. Comparison of the area above the fluorescence induction curves in the absence and presence of DCMU suggested an acceptor pool size of 2–3 equivalents per centre.     

Reduction of oxygen-pulsed cytochrome c oxidase by cytochrome c and other electron donors

1. Stopped-flow experiments were performed in which solutions containing dithionite were mixed with air-saturated buffer. Cytochrome c oxidase present in the dithionite-containing syringe is fully oxidized within the mixing time and the oxygen-pulsed form of the oxidase is produced.2. The reduction of this form by dithionite, by dithionite plus cytochrome c and by dithionite plus methyl viologen or benzyl viologen was followed and compared with the corresponding reduction reactions of the ‘resting’ oxidized enzyme. Reduction by dithionite is relatively slow, but the rate of reduction is greatly increased by addition of cytochrome c or the viologens, which are even more effective than cytochrome c on a molar basis.3. Profound differences between the transient kinetics of the reduction of the two oxidized oxidase derivatives were observed. The results are consistent with a direct reduction of cytochrome a followed by an intramolecular electron transfer to cytochrome a₃ (k^obs₁ = 7.5 s^?1 for the oxygen-pulsed oxidase).4. The spectrum of the oxygen-pulsed oxidase formed within 5 ms of the mixing closely resembles that of the ‘oxygenated’ compound, but there were small differences between the two spectra.     

Quantum efficiency and antenna size of Photosystems IIα, IIβ and I in tobacco chloroplasts

Reaction center concentrations were determined in chloroplasts of tobacco, cv John William's Broadleaf, and its mutants Su/su and Su/su var. Aurea. Quantum yields of the primary reactions of Photosystems I, II_α and II_β (Melis, A. and Homann, P.H. (1975) Photochem. Photobiol. 21, 431–437) were obtained by measurement of their rate constants and the absorbed energy, under conditions where all three photosystems operated simultaneously and produced almost irreversibly a single charge separation.The concentrations and reaction rates of the photosystems were different in chloroplasts from the wild type and the mutants, but in chloroplasts of each type of plant used essentially all quanta absorbed by chlorophyll caused a charge separation in PS I, PS II_α or PS II_β. Since the quantum efficiency of each photosystem was close to one, kinetic differences between the photosystems and between different kinds of chloroplasts were only due to differences in antenna size. From the rate constants the number of chlorophyll molecules in the antenna of each photosystem could be calculated. It is argued that PS II_α and PS II_β must be different, independent structures.