Effect of temperature on the protein and nucleic acid content of thermotolerant yeasts

Summary The effect of growth at 30°, 35° and 40° on the biomass yield and on the nucleic acid and protein content of twelve isolates of yeast has been studied. Although yields of 41.6% and a true protein content of 34% were obtained, each of the strains exhibited a lower yield and protein content at 40° than at the lower temperatures. Nucleic acid levels were also reduced at 40°.     

温度胁迫对马铃薯叶片抗坏血酸代谢系统的影响

采用盆栽试验,研究了高温（40 ℃）和低温（5 ℃）胁迫下,马铃薯叶片抗坏血酸（AsA）含量、L-半乳糖-1,4-内酯脱氢酶（GalLDH）和脱氢抗坏血酸还原酶（DHAR）基因表达与相应酶活性,以及抗坏血酸过氧化物酶（APX）、单脱氢抗坏血酸还原酶（MDHAR）、谷胱甘肽还原酶（GR）活性及H₂O₂和丙二醛（MDA）含量的变化规律,探讨温度胁迫对AsA代谢系统的影响.结果表明：40 ℃下,AsA含量快速增加,在6 h达到最高值,最高值比对照增加43.7％,而后急速减少;5 ℃下,在9 h达到最高值,最高值比对照增加27.7％,而后也开始减少.GalLDH、DHAR、APX、MDHAR和GR活性在40 ℃和5 ℃下均呈先升后降的变化趋势;GalLDH和DHAR基因表达与其酶活性的变化趋势一致.温度胁迫下,H₂O₂和MDA含量均显著增加.说明在温度胁迫初期,马铃薯叶片以AsA为核心的抗氧化系统对抵御高温和低温胁迫发挥了重要作用,但是随着胁迫时间的延长,AsA代谢系统的抗氧化功能逐渐降低.     

Reduction of the nucleic acid content of single-cell protein concentrates

Methods for reducing the content of nucleic acid in protein concentrates from disintegrated yeast and microalgae were investigated. Protein concentrates were prepared by acid precipitation of extracted protein after cell wall separation. The influence of alkaline protein extraction on the content of RNA in isoelectrically precipitated protein concentrates was studied. It was found that when a strong decrease in the RNA content was obtained, this was followed by a decrease in the yield of protein concentrate. Protein concentrates were also prepared without cell wall separation by precipitation with different agents after cell disintegration. In the precipitates from microalgae, a RNA reduction was obtained. Precipitation of yeast, protein gave no essential reduction with the precipitants used. Precipitation of yeast protein by heating at an alkaline pH gave a protein concentrate with a low content of RNA. A slightly lower RNA content was obtained when the precipitation was performed in the presence of NaCl. The yield of amino acid nitrogen was 70–80% and the RNA content was 1–2%. A process with precipitation at alkaline pH for the production of microbial protein concentrates with a low content of nucleic acid is suggested.     

Increase of ascorbic acid content and nutritional quality in spinach leaves during physiological acclimation to low temperature

The effect of acclimation to 10 °C on the leaf content of ascorbic and oxalic acids, was investigated in spinach (Spinacia oleracea L.). At 10 °C the content of ascorbic acid in leaves increased and after 7 days it was about 41% higher than in plants remaining under a 25 °C/20 °C day/night temperature regime. In contrast, the content of oxalate, remained unchanged. Transfer to 10 °C increased the ascorbic but not the oxalic acid content of the leaf intercellular washing fluid (IWF). Oxalate oxidase (OXO EC 1.2.3.4) activity was not detected in extracts of leaf blades. Therefore, oxalic acid degradation via OXO was not involved in the control of its content. Our results show that low temperature acclimation increases nutritional quality of spinach leaves via a physiological rise of ascorbic acid that does not feed-forward on the content of oxalic acid.     

Effects of low temperature acclimation upon photosynthetic induction in barley primary leaves

Oxygen evolution and chlorophyll fluorescence were measured in cold-hardened and unhardened leaves of barley ( Hordeum vulgare L. cv. Asa) during the induction period of photosynthesis. The lag phase of light-saturated photosynthesis was increased and steady-state rates of photosynthesis were higher in cold-hardened than in unhardened barley leaves. Fluorescence was quenched more rapidly during the first minutes of induction in hardened than unhardened leaves, largely because of greater energy-dependent quenching (q_E). Also, slow fluorescence transients through the M peak were delayed and less pronounced in cold-hardened than in unhardened leaves. Based upon the combined fluorescence and oxygen evolution data it was concluded that cold-hardening delayed light activation of the energy consuming carbon reduction cycle, thereby delaying the use of ATP and NADPH formed in the light reaction. Measurements of oxygen evolution and fluorescence kinetics during photosynthetic induction under oxygenic and anoxygenic conditions suggest that oxygen photoreduction is important for additional ATP generation during both the onset of photosynthetic carbon assimilation and during steady-state photosynthesis.     

3种淡水环境中低核酸含量细菌的滤过性

【目的】增加低核酸含量(LNA)细菌与过滤性细菌之间的认识。【方法】采用流式细胞技术(FCM)、变性梯度凝胶电泳(DGGE)及统计学分析研究3种典型淡水环境中细菌群落与滤过性。【结果】LNA细菌与过滤性细菌在数量上具有很好的相关性(y=0.646x+22.42,R2=0.984,P0.01),细菌的滤过性不仅与细菌大小有关,还与细胞整体形状及其伸缩性有关;细菌群落组织与LNA细菌比重呈负相关性,而与HNA细菌呈正相关性。【结论】0.45μm膜过滤对水样微生物群落中的LNA细菌具有极强的筛选效果;细菌群落组织与其基于流式细胞技术测定的基因含量具有密切联系。     

The nucleic acid content of some edible mushrooms

Summary An improved method for the determination of nucleic acid content in edible mushrooms is described. Details of tissue homogenization and extraction are also included. In regard to the limit suggested by the Protein Advisory Group of the United Nations System, the amount of nucleic acids found in Agaricus bisporus, Pleurotus cystidiosus, Pleurotus sajor-caju and Volvariella volvacea indicates that it is safe to consume mushrooms as daily vegetable. No significant changes have been found in the nucleic acid content of V. volvacea at different degrees of maturity. V. volvacea loses around 20% of its nucleic acids upon boiling for 10 min. Possible reasons for the discrepancy between the present finding and that given in an earlier report have been discussed.     

干旱和ABA对同核异质冬小麦叶片蛋白的影响

利用双向凝胶电泳研究了冬小麦核质杂种NC4、NC37和它们的核供体丰抗13的3个品种幼苗在水分胁迫和外施ABA条件下叶片中蛋白质代谢的变化。结果表明水分胁迫可抑制3种小麦叶片中一些蛋白质合成,使蛋白数量减少,而在NC4、NC37两个核质杂种中有1个PI5.8、20kD的新合成蛋白点出现,根部外伤ABA也可诱导该蛋白合成,核供体丰抗13幼苗中,ABA可诱导合成该蛋白,而水分胁迫时该蛋白没有出现,表明该蛋白由核基因编码,而其表达可能由细胞质中与ABA有关的某种机制调控。     

Effect of ambiol and 2-chloroethylphosphonic acid on the content of phytohormones in potato leaves and tubers

The effects of the antioxidant Ambiol and 2-chlorethylphosphonic acid (2-CEPA) on individual concentrations and concentration ratios of phytohormones, photosynthesis and photophosphorylation rates, sucrose and starch content in tubers, and plant productivity were studied in potato (Solanum tuberosum L). Ambiol increased the ratio of indoleacetic acid (IAA) to abscisic acid (ABA), IAA/ABA, and that of zeatin (Z) and zeatin riboside (ZR) to ABA, (Z + ZR)/ABA. These effects were underlain by an increase in the content of auxins and cytokinins and a decrease in ABA. Unlike Ambiol, 2-CEPA increased the level of ABA, the effect being the most pronounced in the tubers. Ambiol increased the rates of photosynthesis and noncyclic photophosphorylation in chloroplasts isolated from potato leaves. The relation of this phenomenon to auxin and cytokinin accumulation, Ambiol- and 2-CEPA-induced changes in the hormonal balance of potato tubers, carbon metabolism, and plant productivity is discussed.