EFFECT OF ELEVATED BICARBONATE CONCENTRATION ON GROWTH, CHLOROPHYLL A FLUORESCENCE AND ULTRA-STRUCTURE OF Microcystis aeruginosa (CYANOBACTERIUM)

The influence of bicarbonate (HCO3-) on Microcystis aeruginosa FACHB 905 was assessed in this study. Growth curves, chlorophyll a fluorescence and ultrastructure were measured at two HCO3- concentrations, 2.3 mM and 12.4 mM. A treatment of sodium chloride (NaCl) was also conducted alongside to establish the influence level of sodium. It was found that upon treatment with elevated HCO3- concentrations of 2.3 mM and 12.4 mM, cell densities were 13% and 27% (respectively) higher than controls. In photosynthetic performance, elevated HCO3- concentration initially stimulated Fv/Fm at the prophase of culture and then subsequently inhibited it. The inhibition of 2.3mM was higher than that of 12.4mM HCO3-. The maximum relative electron transport rate (ETRmax) exhibited inhibition at elevated HCO3- concentrations. DI0/CS was decreased at 2.3 mM and increased at 12.4mM. In the case of both treatments. ABS/CSI TR0/CS, ET0/CS, RC/CS0 and RC/CSm were decreased by elevated HCO3- concentrations, which indicated damage to photosynthetic apparati and an inactivation of a fraction of reaction centers. This point was also proven by ultrastructural photos. High HCO3--exposed cells lost the characteristic photosynthetic membrane arrangement compared with the control and high salinity treated samples. At the 2.3mM concentration of HCO3-. damage to photosynthetic apparati caused decreased photosynthetic activity. These findings suggested that elevated HCO3- concentration stimulated the growth and photosynthesis of M. aeruginosa FACHB 905 in a short time. Exposure to high HCO3- concentrations for a longer period of time will damage photosynthetic apparatus. In addition, the ultrastructure indicated that elevated HCO3--concentration lead to photosynthetic apparati damage. In our experiment, it was observed that the inhibition effect of 2.3mM HCO3- was higher than that of 12.4mM HCO3-. We hypothesized that M. aeruginosa FACHB 905 induced a protective mechanism under high concentrations of HCO3-.

Photosynthetic bicarbonate utilization in Porphyra haitanensis (Bangiales, Rhodophyta)

The activities of carbonic anhydrase (CA) and photosynthesis of Porphyra haitanensis were investigated in order to see its photosynthetic utilization of inorganic carbon source. Both intra- and extra-cellular CA activities existed in the thallus. CA inhibitors, acetazolamide (AZ) and ethoxyzolamide (EZ), remarkably depressed the photosynthetic oxygen evolution in seawater of pH 8.2 and 10.0, and EZ showed stronger inhibition than AZ. The observed net photosynthetic rate In seawater of pH 8.2 was much higher than that of CO2 supply theoretically derived from spontaneous dehydration of HCO3-. P. haitanensis also showed a rather high pH compensation point (9.9). The results demonstrated that P. haitanensis could utilize bicarbonate as the external inorganic carbon source for photosynthesis. The bicarbonate utilization was closely associated with HCO3- dehydration catalyzed by extracellular CA activity. The inorganic carbon composition in seawater could well saturate the photosynthesis of P. haitanensis. The low K-m value and compensation points for inorganic carbon reflected the existence of CO2-concentrating mechanism in this alga.

Photosynthetic bicarbonate utilization by a terrestrial cyanobacterium, Nostoc flagelliforme (Cyanophyceae)

The photosynthetic characteristics of the terrestrial cyanobacterium, Nostoc flagelliforme, after complete recovery by rewetting, was investigated to see whether it could use bicarbonate as the external inorganic carbon source when submerged. The photosynthesis-pH relationship and high pH compensation point suggested that the terrestrial alga could use bicarbonate to photosynthesize when submerged. The photosynthetic oxygen evolution rates were significantly inhibited in Na+-free and Na+ + Li+ media but were not affected by the absence of Cl-, implying that the bicarbonate uptake was associated with Na+/HCO3- symport rather than Cl-/HCO3- exchange system.

新型光系统II电子传递抑制剂的抑制特性及作用位点的研究

本文由两部分组成，一部分是关于一组新型除草剂(K-15，K-23)的抑制特性及作用位点的研究;另一部分是关于碳酸氢盐对细胞色素b-559高电势的保护作用的研究。 在第一部分，我们首先研究了抑制剂K-23对Psn放氧活性、DCIP光还原和可变荧光等光合特性的影响。研究发现，K-23在低浓度时刺激放氧活性，而在相对高浓度时抑制放氧活性。但是，K-23在低浓度时却有效地抑制了可变荧光。这些数据表明了新型抑制剂的抑制反应是基于氧化还原作用而不是猝灭作用。此外，通过采用胰蛋白酶消化类囊体膜的方式初步检测了新型抑制剂的作用部位，其结果表明：虽然新型抑制剂抑制受体侧电子传递，但它的抑制部位与DCMU不同。 其次，研究了新型抑制剂对光系统II色素蛋白复合体与多肽组分的影响及抑制剂的键合蛋白。应用SDS-PAGE技术，发现新型抑制剂主要作用于光系统II的反应中心蛋白。用温和的Deriphat-PAGE分析也证实了新型抑制剂作用于核心复合物，导致核心复合物二聚体消失。 进一步用SDS-PAGE分析新型抑制剂对Psn多肽组分的影响，发现新型抑制剂主要影响D．、D2、CP43和CP47。用荧光发射的方法确定了K-15键合在D2蛋白上。 最后，结合荧光动力学和HPLC方法，分别从定性和定量的角度，以核心复合物以及抑制剂存在下从BBY中分离的核心复合物为研究对象，详细研究了抑制剂对QA的取代作用。研究发现，在无去垢剂或低浓度去垢剂存在情况下，由于不能创造出适合于QA存在的疏水环境，我们没有得到QA被K-15取代的实验证据。而在抑制剂K-15存在下，用2.2% HTG从BBY分离的核心复合物的实验中，检测不到正的可变荧光Fv，而是得到了降低的FM，这个结果表明QA已被抑制剂在它的作用位点处所取代。 在第二部分，研究了pH5.0—7.0范围内碳酸氢盐对Cyt b-559氧化还原状态转变的影响。首先研究了pH5.0～7.0条件下碳酸氢盐对PSII Cyt b-559还原减氧化差异吸收光谱的影响，发现铁氰化钾还原的PSII Cyt b-559 HP的含量随介质pH值的降低而减少。然而，碳酸氢盐的加入阻止了由于介质pH降低而引起的Cyt b-559由高电势向低电势的转化。比如，当样品温育在pH5.0的介质中，铁氰化钾还原的Cyt b-559 HP含量占总量的25%-30%，当介质中加入2mmol/L碳酸氢盐后Cyt b-559 HP的含量上升，占总量的50%-56%。碳酸氢盐效应对氢醌还原的Cyt b-559HP含量的影响尤为显著。pH6.5时碳酸氢盐对Cyt b-559的还原氧化状态的影响不显著。其次，分别研究了PSII经Tris处理去除锰簇和三个外周蛋白及NH20H处理去除锰簇和17 kDa和23 kDa后，碳酸氢盐对Cytb一559 HP影响的pH依赖值，发现不论在pH5.0还是pH6.5的介质中碳酸氢盐效应都不存在。 综合以上实验结果，我们认为碳酸氢盐对酸化引起的Cyt b-559氧化还原状态的影响与它和锰的作用有关，但也不能排除钙离子与碳酸氢盐之间的协同作用。

Photosynthetic utilization of inorganic carbon in the economic brown alga, Hizikia Fusiforme (Sargassaceae) from the South China Sea

The mechanism of inorganic carbon (C-i) acquisition by the economic brown macroalga, Hizikia fusiforme (Harv.) Okamura (Sargassaceae), was investigated to characterize its photosynthetic physiology. Both intracellular and extracellular carbonic anhydrase (CA) were detected, with the external CA activity accounting for about 5% of the total. Hizikia fusiforme showed higher rates of photosynthetic oxygen evolution at alkaline pH than those theoretically derived from the rates of uncatalyzed CO2 production from bicarbonate and exhibited a high pH compensation point (pH 9.66). The external CA inhibitor, acetazolamide, significantly depressed the photosynthetic oxygen evolution, whereas the anion-exchanger inhibitor 4,4'-diisothiocyano-stilbene-2,2'-disulfonate had no inhibitory effect on it, implying the alga was capable of using HCO3- as a source of C-i for its photosynthesis via the mediation of the external CA. CO2 concentrations in the culture media affected its photosynthetic properties. A high level of CO2 (10,000 ppmv) resulted in a decrease in the external CA activity; however, a low CO2 level (20 ppmv) led to no changes in the external CA activity but raised the intracellular CA activity. Parallel to the reduction in the external CA activity at the high CO2 was a reduction in the photosynthetic CO2 affinity. Decreased activity of the external CA in the high CO2 grown samples led to reduced sensitiveness of photosynthesis to the addition of acetazolamide at alkaline pH. It was clearly indicated that H. fusiforme, which showed CO2-limited photosynthesis with the half-saturating concentration of C-i exceeding that of seawater, did not operate active HCO3- uptake but used it via the extracellular CA for its photosynthetic carbon fixation.

Chemical liquid phase deposition of thin aluminum oxide films

Thin aluminum oxide films were deposited by a new and simple physicochemical method called chemical liquid phase deposition (CLD) on semiconductor materials. Aluminum sulfate with crystallized water and sodium bicarbonate were used as precursors for film growth, and the control of the system's pH value played an important role in this experiment. The growth rate is 12 nm/h with the deposition at [Al-2(SO4)(3)]=0.0837 mol.L-1, [NaHCO3]=0.214 mol.L-1, 15 degreesC. Post-growth annealing not only densifies and purifies the films, but results in film crystallization as well. Excellent quality of Al2O3 films in this work is supported by electron dispersion spectroscopy, Fourier transform infrared spectrum, X-ray diffraction spectrum and scanning electron microscopy photograph.

Photo-sensitized oxidation in natural water via .OH radicals

A method is presented for determining production and consumption rates of .OH radicals produced photochemically in natural surface waters. It is based on the determination of the kinetics by which the concentration of a specified trace compound decreases during irradiation. In samples from Lake Greifensee (Switzerland) low production rates for .OH limit its possible effects. In addition, fast consumptions by the natural dissolved organic solutes and by the bicarbonate protect organic micropollutants from oxidation by .OH. Neither direct nor indirect H2O2 photolysis was a significant source of .OH in the lakewater studied lacking iron, whereas nitrate photolysis could have been a source. Comparison with reaction kinetic formulations allows generalizations for other types of waters.

Sequence analysis of Arthrospira maxima based on fosmid library

Arthrospira (Spirulina) (Setchell& Gardner) is an important cyanobacterium not only in its nutritional potential but in its special biological characteristics. An unbiased fosmid library of Arthrospira maxima FACHB438 that contains 4300 clones was constructed. The size distribution of insert fragments is from 15.5 to 48.9 kb and the average size is 37.6 kb. The recombination frequency is 100%. Therefore the library is 29.9 equivalents to the Arthrospira genome size of 5.4 Mb. A total of 719 sample clones were randomly chosen from the library and 602 available sequences, which consisted of 307,547 bases, covering 5.70% of the whole genome. The codon usage of A. maxima was not strongly biased. GC content at the first position of codons (46.9%) was higher than the second (39.8%) and the third (45.5%) positions. GC content of the genome was 43.6%. Of these sequences, 287 (47.7%) showed high similarities to known genes, 63 (10.5%) to hypothetical genes and the remaining 252 (41.8%) had no significant similarities. The assigned genes were classified into 22 categories with respect to different biological roles. Remarkably, the high presence of 25 sequences (4.2%) encoding reverse transcriptase indicates the RT gene may have multiple copies in the A. maxima genome and might play an important role in the evolutionary history and metabolic regulation. In addition, the sequences encoding the ATP-binding cassette transport system and the two-component signal transduction system were the second and third most frequent genes, respectively. These genomic features provide some clues as to the mechanisms by which this organism adapts to the high concentration of bicarbonate and to the high pH environment.