Algal growth inhibition on cement mortar: Efficiency of water repellent and photocatalytic treatments under UV/VIS illumination

Building materials are regularly affected by the growth of microalgae. The consequences are mainly aesthetic but the colonization can cause biodeterioration of the material in the most extreme cases. This study investigates two building material treatments that can potentially inhibit or slow down such growth: photocatalytic coatings and water repellent treatments. The efficiency of these treatments in terms of biological growth inhibition was tested on the algae species Graesiella emersonii. Algal growth on building materials was investigated using two accelerated tests simulating different types of humidification (water capillary ascent and water run-off) under different lighting conditions. Mortars treated with photocatalytic coating or with water repellent were studied. The algal growth on the mortar surface was evaluated using image analysis (area covered and intensity of fouling). No slow down of the biological growth kinetics could be attributed to photocatalytic substrates. However, for mortars impregnated with a water-repellent preparation, algal growth slowed significantly under water run-off and even stopped under water capillary ascent.     

A precise potentiometric method for determination of algal activity in an open CO2 system

Abstract. The activity of the green alga Scenedesmus obliquus was studied in simplified nutrient solutions (20 mol m₋₃ NaNO₃, 20 mol m₋₃ NH₄C1, 20 mol m₋₃ NH₄NO₃, and 20 mol m₋₃ NaCl, respectively) at 25 °C. The experiments were performed under welldefined incident photon density fluxes ranging from 10 to 200 μmol m₂ s₋₁, Light-dependent changes in pH and alkalinity (A) were followed by means of a potentiometric method using a glass electrode. In the experiments, carbon dioxide with known partial pressure was bubbled through the algal suspension, and during dark periods ul intervals of 1 h, the solution was allowed to equilibrate with the gas phase. This technique was applied to calculate equilibrium values of pH and alkalinity at regular intervals during a 12-h period. Results obtained in NaNO₃, solution show a linear increase in A with time, at each level of illumination studied. After an initial drop, A also increases in NH₄NO₃, solution in a similar way to that in NaNO₃ solution. The change in A with time was also found to increase linearly with the photon density flux studied and no saturation level could be defined. In experiments in NaCl solution, no changes in A were registered while measurements in NH₄Cl solution showed a decrease in A with time.     

Effects of intermittent exposure to high atmospheric CO2 on vegetative growth in soybean

Short-term exposure to high CO₂ increases rates of photosynthesis and growth in soybeans, but with prolonged high CO₂ exposure, these high rates are sometimes not maintained. Growth of soybean (Glycine max (L.) Merrill cv. Fiskeby V) seedlings kept for 25 days at atmospheres of 350 or 1000 μ/l CO₂ was compared with growth of plants given 2, 4 or 6 day alternating exposure to high and low CO₂ levels (13 days of total exposure to each level). Final dry weight of plants increased with number of days in high CO₂ but leaf areas were not greatly affected. Thus dry weight gains per unit leaf area (net assimilation rates) were higher in high CO₂ than in low CO₂ throughout the entire period of the experiment and the pattern of exposure to high CO₂ did not affect the rate of dry weight gain in high CO₂.     

A pair of putative protein kinase genes (YPK1 and YPK2) is required for cell growth in Saccharomyces cerevisiae

Summary Probes derived from cDNAs encoding isozymes of rat protein kinase C (PKC) were used to screen the genome of the budding yeast Saccharomyces cerevisiae. We reported previously the isolation of the yeast PKC1 gene, a homolog of the , , and subspecies of mammalian PKC. Here we report the isolation and genetic characterization of a pair of previously described genes (YPK1 and YPK2) which are predicted to encode protein kinases that share 90% amino acid identity with each other and 44–46% identity with various isozymes of PKC throughout their putative catalytic domains. Deletion of YPK2 resulted in no apparent phenotypic defect, but loss of YPK1 resulted in slow growth. Cells deleted for both YPK1 and YPK2 were defective in vegetative growth, indicating that the protein kinases predicted to be encoded by these genes are functionally overlapping and play an essential role in the proliferation of yeast cells. The YPK1 gene was mapped to the left arm of chromosome XI and YPK2 was mapped to the right arm of chromosome XIII.     

长期CO2加富对苗期红掌（Anthurium andraeanum L.）植株生长和光合作用的影响

以开顶式塑料薄膜温室为设施,研究了红掌(Anthurium andraeanum L.)幼苗植株生长、叶片净光合速率和光合酶活性对长期高CO₂浓度的响应。结果表明：处理90 d时,处理组T1（（700±100） μmol•mol^-1 CO₂）的株高、单叶面积、株鲜重分别比对照组（（360±30）μmol•mol^-1）增加了15.76%、14.30%、29.62％,而处理组T2 （（1000±100）μmol•mol^-1 CO₂）的株高、单叶面积、株鲜重分别比对照增加了15.00%、9.63%、3622％;处理150 d时T1的株高、单叶面积、株鲜重与对照相比分别增加了1608％、17.30％、49.09％,而T2增加了16.61％、10.10％、48.87％。在各自生长环境下处理组T1、T2的净光合速率在整个处理期间均高于对照,处理150 d时,T1、T2的净光合速率分别比对照高8.25％、20.62％;但处理90 d时,在对照CO₂浓度下测定的净光合速率处理组开始低于对照组,可能此时处理组的红掌叶片开始出现光合适应现象;CO₂浓度升高促进了叶片中可溶性糖和淀粉积累,处理90 d时T1、T2处理组中淀粉含量分别比对照高52.60％、67.66％;处理150 d时,T1组红掌叶片中淀粉与可溶性糖含量比对照高53.43％、6.32％,T2比对照高58.44％、8.07％,叶绿素含量在处理90 d时也开始低于对照组;整个实验过程中,Rubisco活性前期增加,90 d以后开始下降;乙醇酸氧化酶活性则明显下降,T1、T2处理组试验结束时与对照组相比分别下降了41.28％、45.35％。一定处理时间（90 d）的高浓度CO₂处理提高了红掌叶片的净光合速率和碳水化合物的积累,促进了营养生长,但随着处理时间的延长,这种促进作用逐渐降低。     

二氧化钛纳米颗粒对沼泽土壤反硝化和N2O排放的影响

近年来,二氧化钛纳米颗粒（TiO₂NPs）环境释放量不断增加,并通过多种途径进入湿地生态系统,不可避免地影响到湿地生态系统环境和功能。然而,关于TiO₂NPs对沼泽土壤反硝化作用和氧化亚氮（N₂O）排放的影响机及制尚不明确。选择典型沼泽土壤,通过室内培养实验研究土壤理化性质、反硝化酶活性、反硝化速率（DNR）和N₂O排放对不同剂量TiO₂NPs 0 mg/kg （CK）、10 mg/kg （A10）、100 mg/kg （A100）、1000 mg/kg （A1000）输入的响应,探讨TiO₂NPs输入对沼泽土壤反硝化作用和N₂O排放影响的内在机制。结果表明：不同剂量TiO₂NPs处理显著降低了土壤pH （P<0.05）,A10处理显著降低土壤总有机碳（TOC）含量（P<0.01）,A1000处理显著降低硝态氮（NO₃^--N）和亚硝态氮（NO₂^--N）含量（P<0.05）。TiO₂NPs处理抑制硝酸盐还原酶（NAR）活性,促进一氧化氮还原酶（NOR）和氧化亚氮还原酶（NOS）活性（P<0.01）,A1000处理先促进后抑制了亚硝酸盐还原酶（NIR）活性（P<0.05）。不同剂量TiO₂NPs处理抑制了土壤DNR,促进了N₂O排放,TiO₂NPs处理通过抑制NIR活性,降低土壤DNR,同时通过促进NOR活性,提高N₂O排放。综上,TiO₂NPs输入通过影响反硝化还原酶活性改变沼泽土壤反硝化过程,导致沼泽土壤N₂O排放增加,改变湿地氮的源、汇功能,影响全球气候变化。为TiO₂NPs输入的湿地环境风险评估研究提供理论基础。     

PCR amplification of microalgal DNA for sequencing and species identification: studies on fixatives and algal growth stages

Cultured strains and individually isolated dinoflagellate cells from field samples were preserved in different fixatives to find a method of cell preservation that could provide DNA template in PCR reactions and preserve cell morphology for microscopic studies. Lugol’s solution and various ethanol concentrations all showed shortcomings, whereas an initial formalin preservation step followed by storage in 100% methanol fulfilled both demands. Cells could be stored up to 1 year and still provide functional DNA template for positive PCR reactions. The amplified fragment was approximately 700 bp of the D1/D2 region of the LSU rDNA, which is to our knowledge significantly longer than the low-molecular-weight DNA typically reported from formalin preserved samples. By cloning and sequencing the PCR product and subsequently aligning the sequences with previously sequenced fragments of the same or similar species, we confirmed that no base pair alteration had taken place during the time that the cells were fixed and frozen. In another experiment it was demonstrated that the growth phase of cultured Alexandrium minutum did not have any influence on the result of PCR reactions. This was true for extracted DNA from cultures and for direct PCR with a small number of disrupted cells. Phenol/chlorophorm/isoamylalcohol extraction proved to be an unpredictable method for DNA extraction, whereas direct PCR on isolated cells was more reliable. Extracted DNA purified with a commercial DNA cleaning kit always rendered a positive PCR. The environmental condition for cells to be used as DNA template in PCR is discussed.     

Effects of β-glucanase supplementation of barley diets on growth performance of broilers

A trial was performed to examine the effects of levels of barley substitution and supplementation with β-glucanase in a corn–soybean diet on growth performance and intestinal characteristics of broiler chickens. The experiment involved five levels of barley substituted for corn (0, 125, 250, 500, and 1000 g/kg) and two levels of β-glucanase supplement (with 0.5 g/kg and without) in a factorial arrangement with two replicates. Four hundred day-old commercial strain Harber broiler chickens were randomly allocated into twenty groups of ten dietary treatments for a six-week feeding trial, growing (0–3 week) and finishing period (4–6 week). Unless supplemented with β-glucanase, broilers receiving the diet with more than 250 g/kg of the barley substitute gained slower during the growth period. Conversely, supplementing β-glucanase did not improve total weight gain (0–6 weeks) with a diet of 500 g/kg barley substitution. As the level of barley substitution increased, feed intake in the growing period decreased significantly and viscosity of the intestinal contents increased. However, such an increase did not significantly influence feed conversion (P>0.05). Supplementation with β-glucanase on diet up to 250 g/kg of barley substitute not only enhanced body weight gains of growing broilers, but also improved the live-weight of six-week-old broilers (P<0.05).     

Cadmium effect on the growth, photosynthesis, ultrastructure and phytochelatin content of green microalga Scenedesmus armatus: A study at low and elevated CO2 concentration

Short-term experiments were carried out to examine the toxicity of cadmium chloride (CdCl₂) at a concentration of 93 μM (EC_50/24) to green microalga Scenedesmus armatus, cultured at low (0.1%) and elevated (2%) concentration of CO₂. Cadmium did not affect the viability of cells cultured for 24 h in both CO₂ variants but markedly inhibited the growth of algae. This inhibition was more pronounced in cultures aerated with 0.1% (about 50% of control) than with 2% CO₂ (about 75% of control) and did not change during 72 h of culture. Cadmium inhibited the rate of oxygen evolution (P_oxy.) (70% of control) of cells cultured at 0.1% CO₂ and had no effect on P_oxy. of cells cultured at 2% CO₂. The values of the chlorophyll fluorescence parameters, i.e. F_M (maximum fluorescence yield), F_V (variable fluorescence), F_V/F_M (maximum quantum yield of PSII), Φ_PSII (effective quantum yield of PSII) and qP (photochemical quenching) were reduced by cadmium treatment in algae grown at 0.1% CO₂ concentration, whereas F₀ (initial fluorescence yield) remained unaffected. In high-CO₂ grown cells only F_V was significantly reduced. Cd-treated cells synthesized several thiol-containing peptides identified by HPLC as a dimer (PC₂), a trimer (PC₃) and a tetramer (PC₄) of phytochelatins (PC_S). High-CO₂ grown cells produced significantly more PCs than low-CO₂ grown cells and their individual appearance depended on the time of exposure and CO₂ level. The ultrastructural analysis of low-CO₂ grown cells showed in chloroplasts an increased number of small starch grains visible around the pyrenoid. In the enhanced vacuome compartment, various types of vacuoles were clearly seen in Cd-treated cells. Vacuoles containing non-membranous, electron-opaque deposits of an undefined structure and myelin-like figures were especially observed. The results suggest that algae living in conditions of elevated CO₂ are better protected against cadmium than those at ordinary CO₂ level, and productive processes are less affected than the growth ones.     

浒苔干粉末提取物对东海原甲藻和中肋骨条藻的克生作用

研究不同溶剂的浒苔干粉末组织提取液对两种赤潮藻—东海原甲藻和中肋骨条藻生长的克生效应。结果表明, 浒苔提取物中确实含有可以影响赤潮藻类生长的克生物质,克生作用具有较明显的浓度效应,添加浓度低时可能会表现为一定的促进生长的作用,添加浓度较高时表现为抑制作用,添加浓度越大,抑制作用越强,即“低促高抑”的特点,这与浒苔提取物对其他微藻的作用相似。其中,蒸馏水提取物对这两种赤潮藻的克生作用小于有机溶剂提取物,有机溶剂中,甲醇和乙酸乙酯提取物对这两种赤潮藻的克生效果最好,正己烷相对较差。根据相似相溶原理,可以初步推断最有效的克生物质应为具有相对较高的极性的有机物。两种赤潮藻对克生物质的敏感程度不同。东海原甲藻对克生物质的敏感性高于中肋骨条藻。蒸馏水、甲醇、乙酸乙酯、正己烷的浒苔干粉末提取物影响东海原甲藻生长的致死作用阈值浓度分别为5.00 g/L、0.50 g/L、0.50 g/L、0.63 g/L（相当于浒苔新鲜藻体浓度为22.00 g-wet/L、2.20 g-wet/L、2.20 g-wet/L、2.75 g-wet/L）;影响中肋骨条藻生长的致死作用阈值浓度则分别为20.00 g/L、1.25 g/L、1.25 g/L、2.50 g/L（相当于新鲜藻体浓度为88.00 g-wet/L、5.50 g-wet/L、5.50 g-wet/L、11.00 g-wet/L）。     

A novel glass fiber disc culture system for testing of small amounts of compounds on growth and aflatoxin production byAspergillus flavus

A new method for growingAspergllius flavus for experimental studies is presented. The system consists of a humidified vial with a thick septum pierced by a pin on which a glass fiber disc is affixed. The disc contains the test solution and inoculum plus medium. The method has been used to assess the effect of variations in culture conditions on production of aflatoxin B₁ (AFB₁). The AFB₁ level was affected by the amount of medium placed on the disc and type of disc material. The results for different types of glass fiber and quartz discs were compared with AFB₁ produced by fungus grown in liquid medium or on paper discs. When compared to a liquid medium culture there was a 15 to 20-fold increase in AFB₁ for one type of disc. Incubations with less than 14 µl of medium gave satisfactory results. A crude phosphatidylcholine preparation at a concentration of 0.7% of the medium resulted in a 4-fold increase in AFB₁.Abbreviations AFB₁ aflatoxin B₁ - CV coefficient of variation - PC phosphatidylcholine - SD suspended disc     

Pb2+胁迫对绿球藻(Chlorococcum sp.)的影响研究

研究了不同Pb²⁺浓度(0.1、1、10、50、100、200、400 mg/L)处理对绿球藻(Chlorococcum sp.)生长、形态结构及生理特性的影响。与对照BG11培养的绿球藻比较,Pb²⁺浓度≤50 mg/L条件下培养的绿球藻细胞壁无明显增厚,色素变化不大;而暴露到Pb²⁺浓度>50 mg/L条件下培养,绿球藻细胞壁明显增厚,蛋白核消失。低浓度Pb²⁺(0.1~10 mg/L)对绿球藻生长基本没有影响;浓度在50 mg/L时,绿球藻仍能维持一定的生长速率;但当Pb²⁺浓度≥100 mg/L时,绿球藻的生长受到显著抑制。绿球藻的Chl a+Chl b以及Chl a含量均随培养基中Pb²⁺浓度的升高而逐渐减少。绿球藻净光合作用强度随培养基中Pb²⁺浓度的增大而逐渐降低,Pb²⁺浓度≥100 mg/L时净光合作用强度检测不到;当Pb²⁺浓度<50 mg/L时,绿球藻呼吸作用强度逐渐升高,之后呼吸作用强度逐渐降低。在实验的浓度下,绿球藻的丙二醛(MDA)含量、超氧化物歧化酶(SOD)和过氧化物酶(POD)活性都随培养基中Pb²⁺浓度的升高而逐渐增强;过氧化氢酶(CAT)则随Pb²⁺浓度的增大酶活性先升高后降低。当Pb²⁺浓度≤100 mg/L时,绿球藻对Pb²⁺的去除率都在95%以上;之后逐渐降低,浓度到400 mg/L时仍然达56.7%。结果显示,绿球藻是一种耐受Pb²⁺胁迫的藻类,对铅的去除率也高,可以应用于含铅污水的处理。     

The effect of imidazole and imidazole-analogues on bone resorption in vitro: A suggested role for thromboxane A2

The effects of imidazole, 1-methyl-imidazole and benzimidazole on bone metabolism $\text{in vitro}$ were investigated. The relative potencies of these compounds with respect to the inhibition of bone resorption was found to be comparable to their relative effectiveness as inhibitors of platelet microsome thromboxane synthetase activity. Since studies by others have shown that thromboxanes are produced by resorbing bone $\text{in vitro}$, these results suggest that the inhibition of bone resorption by imidazole is related to the inhibition of thromboxane A₂ formation. This could imply that thromboxane A₂ is an additional arachidonic acid oxidation product that is of importance in the regulation of bone metabolism.     

Growth of methanogens on cyclopentanol/CO2 and specificity of alcohol dehydrogenase

Abstract Growth of 5 strains of secondary alcohol-utilizing methanogens on cyclopentanol/CO₂ was demonstrated. Cultures reached only low optical densities, comparable to those observed during growth on 2-propanol/CO₂ or 2-butanol/CO₂. The conversion of cyclopentanol to cyclopentanone was reversible in the presence of hydrogen. The specificity of ADHs of nine secondary alcohol-utilizing methanogens for coenzyme requirement and substrates was tested using crude enzyme preparations. The ADH of Methanobacterium bryantii M.o.H.G, Methabobacterium palustre, Methanocorpusculum parvum and Methanocorpusculum bavaricum was only active with NADP⁺, the ADH of Methanomicrobium paynteri, Methanogenium marisnigri, Methanogenium bourgense , strain GKZPZ and strain INSLUZ with F₄₂₀ as electron carrier. FAD, FMN, methylene blue, benzyl viologen and tetrazolium, chloride could be used as electron carriers by the F₄₂₀-dependent ADHs if endogenous F₄₂₀ was introduced with the crude ADH preparation. No reaction with these electron carriers occurred if dialyzed extracts were used as a source of ADH. The ADH of all tested strains oxidized 2-propanol, 2-butanol, 2-pentanol and cyclopentanol, while the ADH of Mg. marisnigri and Mm. paynteri oxidized cyclohexanol, of Mb. palustre and Mcp. bavaricum cyclopentanol and 2,3-butanediol,and of Mcp. parvum cyclopentanol, 2,3-butanediol, ethanol and 1-propanol in addition.     

A method for measuring the transfer of fixed nitrogen from free-living bacteria to higher plants using 15N2

An apparatus is described in which the root systems of up to ten plants can be simultaneously incubated with ¹⁵N₂ gas mixtures, while the aerial environment remains undisturbed. The size of incubation chamber and the number of chambers can be adjusted depending on the size and growth stage of the plants being tested. The apparatus has the facility for the recovery of gas mixtures, sampling and adjustment of gas concentrations, and control of soil moisture status within a sealed system. Possible experimental applications are suggested and some preliminary results presented which demonstrate bacterial nitrogen fixation and uptake into Sorghum seedlings.     

CO2浓度升高对凤梨叶片生长和光合特性的影响

研究了CO2浓度升高对开顶式气室中凤梨叶片的生长与光合生理的影响。结果表明:高CO2浓度(1000±100μmolmol-1)下生长的凤梨植株的株高、叶面积、鲜重和干重均高于对照(360±30μmolmol-1),处理90d时分别为对照的120.19%、119.22%、177.91%和161.04%;凤梨叶片的净光合速率也增加了136%-259%,且促进了叶片中可溶性糖和淀粉的积累,但叶绿素含量则下降了33.91%。高CO2浓度处理的凤梨叶片中RuBP羧化酶活性没有明显变化,乙醇酸氧化酶活性则明显下降。     

Lethality of hydrogen peroxide in wild type and superoxide dismutase mutants of Escherichia coli. (A hypothesis on the mechanism of H2O2-induced inactivation of Escherichia coli)

The toxicity of H₂O₂ in Escherichia coli wild type and superoxide dismutase mutants was investigated under different experimental conditions. Cells were either grown aerobically, and then treated in M9 salts or K medium, or grown anoxically, and then treated in K medium. Results have demonstrated that the wild type and superoxide dismutase mutants display a markedly different sensitivity to both modes of lethality produced by H₂O₂ (i.e. mode one killing, which is produced by concentrations of H₂O₂ lower than 5 mM, and mode two killing which results from the insult generated by concentrations of H₂O₂ higher than 10 mM). Although the data obtained do not clarify the molecular basis of H₂O₂ toxicity and/or do not explain the specific function of superoxide ions in H₂O₂-induced bacterial inactivation, they certainly demonstrate that the latter species plays a key role in both modes of H₂O₂ lethality. A mechanism of H₂O₂ toxicity in E. coli is proposed, involving the action of a hypothetical enzyme which should work as an O₂^-• generating system. This enzyme should be active at low concentrations of H₂O₂ (<5 mM) and high concentrations of the oxidant (>5 mM) should inactivate the same enzyme. Superoxide ions would then be produced and result in mode one lethality. The resistance at intermediate H₂O₂ concentrations may be dependent on the inactivation of such enzyme with no superoxide ions being produced at levels of H₂O₂ in the range 5–10 mM. Mode two killing could be produced by the hydroxyl radical in concert with superoxide ions, chemically produced via the reaction of high concentrations of H₂O₂ (>10 mM) with hydroxyl radicals. The rate of hydroxyl radical production may be increased by the higher availability of Fe²⁺ since superoxide ions may also reduce trivalent iron to the divalent form.     

超微粒TiO2对U937细胞光杀伤效应及机理研究

超微粒TiO₂经光催化氧化后对U937白血病细胞有明显的杀伤作用,DNA琼脂糖凝胶电泳图证明了光激发TiO₂能够损伤细胞内的DNA,从而导致细胞死亡,提出了一种杀伤癌细胞的新思路.