The Effect of Sodium Azide on the Thermotolerance of the Yeasts Saccharomyces cerevisiae and Candida albicans

The addition of sodium azide (a mitochondrial inhibitor) at a concentration of 0.15 mM to glucose-grown Saccharomyces cerevisiae or Candida albicans cells before exposing them to heat shock increased cell survival. At higher concentrations of azide, its protective effect on glucose-grown cells decreased. Furthermore, azide, even at low concentrations, diminished the thermotolerance of galactose-grown yeast cells. It is suggested that azide exerts a protective effect on the thermotolerance of yeast cells when their energy requirements are met by the fermentation of glucose. However, when cells obtain energy through respiratory metabolism, the azide inhibition of mitochondria enhances the damage inflicted on the cells by heat shock.     

The Effect of Sodium Azide on Basic and Induced Thermotolerance in Saccharomyces cerevisiae

The action mechanism of the mitochondrial inhibitor sodium azide on thermotolerance in Saccharomyces cerevisiae was studied. At ambient growth temperature, pretreatment with sodium azide was shown to improve the thermotolerance of parent cells and the hsp104 mutant. Treating with the inhibitor during a mild heat shock suppressed the development of induced thermotolerance due to the inhibition of heat shock protein (Hsp104) synthesis. Treating with the inhibitor immediately before lethal heat shock produced a variety of effects on thermotolerance depending on whether the yeast metabolism was oxidative or fermentative. The conclusions are: (1) the protective effect of sodium azide on the thermotolerance of S. cerevisiae cells grown on glucose-containing medium is not related to Hsp104 functioning, and (2) the mechanisms of basic and induced thermotolerance differ considerably.     

The Effect of Cytochrome Oxidase Inhibitors on the Thermotolerance of Yeasts

The investigation of the effect of the cytochrome oxidase inhibitors sodium cyanide and sodium azide on the thermotolerance of the yeasts Rhodotorula rubra, Debaryomyces vanriji, and Saccharomyces cerevisiae showed that these inhibitors diminish the thermotolerance of R. rubraand D. vanriji, but do not affect the thermotolerance of S. cerevisiae. Taking into account the fact that, unlike the latter yeast, R. rubra and D. vanriji are nonfermentative yeasts, the difference in the effects of the inhibitors on the yeast thermotolerance can be readily explained by the different types of glucose utilization (either oxidative or fermentative) in these yeasts. The data obtained also provide evidence that there is a correlation between the functional activity of mitochondria and the thermotolerance of yeast cells.     

The Effect of Sodium Malonate on Yeast Thermotolerance

The study of the effect of malonate (an inhibitor of the succinate dehydrogenase complex of the respiratory chain of mitochondria) on the thermotolerance of the fermentative Saccharomyces cerevisiae and nonfermentative Rhodotorula rubra yeasts showed that malonate augmented the damaging effect of heat shock on the yeasts utilizing glucose (or other sugars) by means of oxidative phosphorylation. At the same time, malonate did not influence, and sometimes even improved, the thermotolerance of the yeasts utilizing glucose through fermentation. The suggestion is made that cell tolerance to heat shock depends on the normal functioning of mitochondria. On the other hand, their increased activity at elevated temperatures may accelerate the formation of cytotoxic reactive oxygen species and, hence, is not beneficial to cells.     

叠氮化钠诱变玉扇愈伤组织的研究

在含不同浓度叠氮化钠（0、0.01、0.05、0.1、0.5和1.0mmol·L~（-1））的诱导培养基上诱导玉扇愈伤组织发生变异。结果表明,叠氮化钠对玉扇愈伤组织的半致死浓度为0.1～0.5 mmo1·L~（-1）,0.1 mmol·L~（-1）有利于保证一定量的有效变异率和再生率。再生芽多发生叶片失绿、畸形和叶序改变,其中较多的叶序变异,有望为研究叶序决定提供材料。     

Effect of sodium azide on heat-shock resistance in Saccharomyces cerevisiae and Debaryomyces vanriji yeasts]

The pretreatment of Saccharomyces cerevisiae and Debaryomyces vanriji with sodium azide was found to induce thermotolerance in both yeasts, whereas sodium azide used in combination with heat shock enhanced the thermotolerance of S. cerevisiae and substantially decreased the thermotolerance of D. vanriji. It is suggested that the different responses of the yeasts to sodium azide during heat shock are due to the different functional organizations of their mitochondrial apparatus.     

The Interaction of Azide with Polyphenol Oxidase II from Tobacco

Spectroscopy studies of absorption and circular dichroism of native PPO II and azide PPO II complex demonstrate two new absorptions at 375 nm and 500 nm after azide's binding with PPO II, which are assigned as the terminal azide to copper charge transfer transitions _o ^nb-to-copper and _v ^nb-to-copper charge transfer transitions respectively. FT-IR spectra also demonstrate that the azide binds in terminal geometry with one of type-3 coppers. The interaction between azide and PPO II is discussed. One terminal azide's binding with one type-3 copper improves the activity of PPO II and the other three azides' further binding in terminal geometry with the type-3 coppers decreases the activity. We theorize that steric hindrance of azides makes oxygen difficult to bind in the active site.     

酿酒酵母菌耐热性快速鉴别的方法研究

目的:找出快速有效的鉴别酵母耐热性的方法。方法:酿酒酵母菌经过不同温度热激处理后,用美兰染色计数、稀释平板计数、发酵活力直接测定法和浊度测定法对酿酒酵母菌耐热性进行了测定,同时对酵母菌的形态也进行了观察。结果:表明浊度测定的结果和发酵活力直接测定法测定的结果关系没有相关性,不便用来测定酵母菌的活力。用美兰染色计数、稀释平板计数和发酵活力直接测定法所得的结果有同样的趋势,通过相关性分析,这些方法都可以表示酵母菌的活力,但各有其特点。其中,美兰染色计数是鉴别酵母耐热性的快速有效的方法。     

Azide resistant mutants of Acetobacter diazotrophicus and Azospirillum brasilense increase yield and nitrogen content of cotton

Abstract

Evolution of symbiotic plant-microbe interactions has provided mankind a powerful and environment-friendly means to increase yield of agricultural crops. Here, we report that some azide resistant mutants of two microbial strains can significantly enhance the productivity of cotton varieties, as an attractive and cheap biological substitute of chemical fertilizers, for improved yield of an important cash crop, without any untoward impacts. Sodium azide resistant mutants were isolated from each strain of Azospirillum brasilense and Acetobacter diazotrophicus on different concentrations of sodium azide ranging from 5–60µg/ml. These azide resistant mutants were assessed for their performance on cotton (varieties H-117, HD-123) for various parameters. Inoculation of cottonseeds with mutants obtained better results than inoculation with their respective parental strains. Azide resistant mutants, when used as biofertilizers, showed increased plant height, early flowering, more yield, and high biomass and total nitrogen content. They also increased, in cotton genotypes, the indole acetic acid production and ammonia excretion due to high nitrogenase activity.     

Hemolysis of Human Red Blood Cells by Riboflavin-Cu(II) System: Enhancement by Azide

Photoactivated riboflavin in the presence of Cu(II) generates reactive oxygen species (ROS) which can hemolyze human red blood cells (RBC). In the present work we examined the effect of sodium azide (NaN3) on RBC in the presence of riboflavin and Cu(II). The addition of NaN3 to the riboflavin-Cu(II) system enhanced K+ loss and hemolysis. The extent of K+ loss and hemolysis were time and concentration dependent. Bathocuproine, a Cu(I)-sequestering agent, inhibited the hemolysis completely. Among various free radical scavengers used to identify the major ROS involved in the reaction, thiourea was found to be the most effective scavenger. Thiourea caused almost 85% inhibition of hemolysis suggesting that *OH is the major ROS involved in the reaction. Using spectral studies and other observations, we propose that when NaN3 is added to the riboflavin-Cu(II) system, it inhibits the photodegradation of riboflavin resulting in increased *OH generation. Also, the possibility of azide radical formation and its involvement in the reaction could not be ruled out.     

Changes in Salicylic and Abscisic Acid Contents during Heat Treatment and Their Effect on Thermotolerance of Grape Plants

Heat treatment (38°C) of young grape plants (Vitis vinifera L., cv. Jingxiu) or leaf spraying with 100 µM salicylic acid (SA) increased leaf thermotolerance. Both treatments led to an increase in ABA content and a decrease in lipoxygenase (LOX) activity. ABA content showed a drastic rise by one hour after treatments and then sharply declined while LOX activity continuously decreased. In the course of heat treatment of grape plants, endogenous SA level and phenylalanine ammonia-lyase activity rapidly increased during the first hour, then declined. These results showed that endogenous SA and ABA can be involved in grape plant response to heat treatment resulted in improved thermotolerance.From Fiziologiya Rastenii, Vol. 52, No. 4, 2005, pp. 578–583.Original English Text Copyright © 2005 by Wang, Huang, Liu, Zhan.The text was submitted by the authors in English.     

GABA Enhances Thermotolerance of Seeds Germination by Attenuating the ROS Damage in Arabidopsis

Seeds germination is strictly controlled by environment factor such ashigh temperature (HT) through altering the balance between gibberellin acid (GA)and abscisic acid (ABA). Gama-aminobutyric acid (GABA) is a small moleculewith four-carbon amino acid, which plays a crucial role during plant physiologicalprocess associated with pollination, wounding or abiotic stress, but its role inseeds germination under HT remains elusive. In this study we found that HTinduced the overaccumulation of ROS, mainly H₂O₂ and O₂^-, to suppress seedsgermination, meanwhile, HT also activated the enzyme activity of GAD for therapid accumulation of GABA, hinting the regulatory function of GABA in controlling seeds germination against HT stress. Applying GABA directly attenuatedHT-induced ROS accumulation, upregulated GA biosynthesis and downregulatedABA biosynthesis, ultimately enhanced seeds germination. Consistently, geneticanalysis using the gad1/2 mutant defective in GABA biosynthesis, or pop2-5mutant with high endogenous GABA content supported the potential functionof GABA in improving seeds germination tolerance to HT through scavengingROS overaccumulation. Based on these data, we propose that GABA acts as anovel signal to enhance thermotolerance of seeds germination through alleviatingthe ROS damage to seeds viability.     

超声波对酵母过氧化氢酶及多酚氧化酶活性的影响

用微超声处理酵母过氧化氢酶(CAT)和多酚氧化酶(PPO),结果表明,在一定参数范围内CAT和PPO活性都升高。对CAT来说,其最适当的超声参数是135kHz、40Wcm2、处理10min。对PPO来说,其最适当参数是135kHz、25Wcm2、处理10min。经光谱分析,PPO超声处理后紫外差示光谱在一定的波长下呈现出明显的正峰和负峰 。     

Sodium azide as a specific quencher of singlet oxygen during chemiluminescent detection by luminol and Cypridina luciferin analogues

Reactive oxygen species (ROS) are presently thought to play important role in an increasing number of the physiological and pathological processes in living organisms. Various chemiluminescent (CL) compounds have been studied in order to find suitable and specific probes for the detection of particular ROS species. The CL of luminol is known to be non‐specific and can be induced by various oxidants. Two Cypridina luciferin analogues, CLA and MCLA, have been used for the detection of ROS in vivo. CLAs are thought to emit light only when reacting with superoxide and singlet oxygen. It is possible to distinguish the particular ROS by using a specific quencher or scavenger, e.g. superoxide dismutase (SOD) or sodium azide (NaN₃). The CL reactions of luminol (3‐aminophthalhydrazide), CLA [2‐methyl‐6‐phenyl‐3,7‐dihydroimidazo(1,2α) pyrazin‐3‐one] and MCLA [2‐methyl‐6‐(p‐methoxyphenyl)‐3,7‐dihydroimidazo(1,2α) pyrazin‐3‐one] were studied in three hydrogen peroxide decomposition systems (H₂O₂–HRP; H₂O₂–CuSO₄; and H₂O₂–NaOCl). The measurements were carried out in phosphate buffer, pH 7.4, at 25 °C, using a luminometer (Fluoroskan Ascent FL and Sirius C). NaN₃ was used as the specific quencher of singlet oxygen. The results demonstrate that the proclaimed specifity of the CL of Cypridina luciferin analogues towards singlet oxygen has to be discussed. Copyright © 2011 John Wiley & Sons, Ltd.     

PAG-OA衍生物Ⅰ5对酿酒酵母转化合成ATP的影响

一种新型促渗透剂PAG-OA(聚氧烯油酸二醇)I 5,甲苯、气流干燥及吐温100等,对酿酒酵母进行细胞渗透性增强处理,考察了酿酒酵母的促渗透性对三磷酸腺苷生产的影响.结果表明,与其他促渗透方式相比,I 5对酿酒酵母三磷酸腺苷的产量有很大的提高.加入0.022 mol/L腺苷,三磷酸腺苷得率为0.038 mol/L,转化率98%;三磷酸腺苷合成时间缩短为1.5 h.经促渗透化处理的酿酒酵母细胞能很好的释放胞内代谢的极性物质;其三磷酸腺苷生产活性大幅度提高.