棉花品系Ｙ18对草甘瞵应激反应机理的研究

5-烯醇丙酮酰-莽草酸-3-磷酸合成酶（5-enolpyruvyl-shikimate-3-phosphate synthase, EPSPS）是植物和微生物体内合成芳香族氨基酸所必需的一个关键酶,但此酶受广谱性除草剂草甘膦的强烈抑制。本试验对草甘膦胁迫下的棉花品系（Y18）研究发现：棉花品系Y18具有两个不同的5-烯醇丙酮酰-莽草酸-3-磷酸合成酶基因epsps1和epsps2,两个基因的编码区与其他植物的epsps基因具有较高的同源性,在草甘膦胁迫作用下,棉花的epsps1基因表达较为稳定,epsps2基因表达提高了1.85-2.3倍,初步认为epsps基因表达量的提高是生物对胁迫作用的一种应激反应。     

Influence of the herbicide glyphosate on soil microbial community structure

The side effects of glyphosate on the soil microflora were monitored by applying a range of glyphosate concentrations (0, 2, 20, and 200 μg g⁻¹ herbicide) to incubated soil samples, and following changes in various microbial groups over 27 days. Bacterial propagule numbers were temporarily enhanced by 20 μg g⁻¹ and 200 μg g⁻¹ glyphosate, while actinomycete and fungal propagule numbers were unaffected by glyphosate. The frequency of three fungal species on organic particles in soil was temporarily enhanced by 200 μg g⁻¹ glyphosate, while one was inhibited. One species was temporily enhanced on mineral particles. However, many of these fungi were inhibited by 200 μg g⁻¹ glyphosate in pure culture. There was little agreement between species responses to glyphosate in incubated soil samples and in pure culture.     

Survival of inoculated Saccharomyces cerevisiae strain on wine grapes during two vintages

AIMS: To investigate the influence of a specific ecological niche, the wine grape, on the survival and development of Saccharomyces cerevisiae. METHODS AND RESULTS: A strain with a rare phenotype was sprayed onto the grape surfaces and monitored through two vintages using a specific indicative medium and analysing the internal transcribed spacer regions in the 5.8S rDNA. During the ripening process, there was a progressive colonization of the surface of the undamaged and damaged grapes by epiphytic yeasts, up to the time of harvest. The damaged wine grapes showed a much greater epiphytic yeast population. However, the inoculated S. cerevisiae strain showed a scarce persistence on both undamaged and damaged wine grapes, and the damaged grapes did not appear to improve the grape surface colonization of this strain. CONCLUSIONS: Results indicated that wine grape is not a favourable ecological niche for the development and colonization of S. cerevisiae species. SIGNIFICANCE AND IMPACT OF THE STUDY: Results of this work are further evidence that S. cerevisiae is not specifically associated with natural environments such as damaged and undamaged wine grapes.     

Differential sensitivity of bacterial 5-enolpyruvylshikimate-3-phosphate synthases to the herbicide glyphosate

Abstract The potent inhibition of the shikimate pathway enzyme 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase by the broad-spectrum herbicide glyphosate ( N -[phosphonomethyl]glycine) was confirmed for the enzymes extracted from various bacteria, a green alga and higher plants. However, 5 out of 6 species belonging to the genus Pseudomonas were found to have EPSP synthases with a 50- to 100-fold decreased sensitivity to the inhibitor. Correspondingly, growth of these 5 species was not inhibited by 5 mM glyphosate, and the organisms did not excrete shikimate-3-phosphate in the presence of the herbicide.     

Accumulation of magnesium ions during fermentative metabolism in Saccharomyces cerevisiae

When cells of Saccharomyces cerevisiae were grown aerobically under glucose-repressed conditions, ethanol production displayed a hyperbolic relationship over a limited range of magnesium concentrations up to around 0.5 mM. A similar relationship existed between available Mg²⁺ and ethanol yield, but over a narrower range of Mg²⁺ concentrations. Cellular demand for Mg²⁺ during fermentation was reflected in the accumulation patterns of Mg²⁺ by yeast cells from the growth medium. Entry of cells into the stationary growth phase and the time of maximum ethanol and minimum sugar concentration correlated with a period of maximum Mg²⁺ transport by yeast cells. The timing of Mg²⁺ transport fluxes by S. cerevisiae is potentially useful when conditioning yeast seed inocula prior to alcohol fermentations. Received 04 March 1996/ Accepted in revised form 21 August 1996     

Microsatellite PCR profiling of Saccharomyces cerevisiae strains during wine fermentation

AIMS: Use of microsatellite PCR to monitor populations of Saccharomyces cerevisiae strains during fermentation of grape juice. METHOD AND RESULTS: Six commercial wine strains of S. cerevisiae were screened for polymorphism at the SC8132X locus using a modified rapid PCR identification technique. The strains formed four distinct polymorphic groups that could be readily distinguished from one another. Fermentations inoculated with mixtures of three strains polymorphic at the SC8132X locus were monitored until sugar utilization was complete, and all exhibited a changing population structure throughout the fermentation. CONCLUSIONS: Rapid population quantification demonstrated that wine fermentations are dynamic and do not necessarily reflect the initial yeast population structure. One or more yeast strains were found to dominate at different stages of the fermentation. SIGNIFICANCE AND IMPACT OF THE STUDY: The population structure of S. cerevisiae during mixed culture wine fermentation is dynamic and could modify the chemical composition and flavour profile of wine.     

Molecular cloning of the ADE1 gene of Saccharomyces cerevisiae and stability of the transformants

Plasmid YEp(ADE1)1a, containing a 2.7-kb Sau3A fragment of Saccharomyces cerevisiae DNA inserted at the BamHI site of the yeast shuttle vector pBTI-1 (Morris et al., 1981), results in high frequency, unstable transformation of ade1 yeast strains. A second plasmid, YRp(ADE1)2, containing adjacent 0.5-kb and 3.0-kb BamHI fragments in pBR322 gave three types of yeast transformants: (1) transformants carrying extrachromosomal copies of the plasmid which indicate the presence of a functional ars sequence, (2) transformants indistinguishable from ade1 strains by hybridization analyis, and (3) a transformant carrying a multimeric form of YRp(ADE1)2. Cells transformed with either of the plasmids are free of the red pigment characteristic of ade1 mutants and indicate potential for direct colour-based selection of yeast transformants using ADE1 plasmids.     

Modeling the influence of slurry concentration on Saccharomyces cerevisiae cake porosity and resistance during microfiltration

Filtration of an isotonic suspension of baker's yeast through a 0.45‐μm membrane was studied at two different pressures, 40 and 80 kPa, for yeast concentrations ranging from 0.14 to 51 kg/m³ (dry weight). For a yeast volume fraction above 0.06 (～21.8 kg/m³), the porosity of the yeast cake is less dependent on the suspension concentration. For highly diluted suspensions, the specific cake resistance approaches a minimum that depends on the filtration pressure. Correlation functions of cake porosity and specific cake resistance were obtained for the concentration range investigated showing that the Kozeny–Carman coefficient increases when the applied pressure increases. Both filtration pressure and slurry concentration can be process controlled. In the range of moderate yeast concentration, the filtrate flux may be increased by manipulating the filtration pressure and the slurry concentration, thereby improving the overall process efficiency. The complex behavior of yeast cakes at high slurry concentration can be described by a conventional model as long as part of yeast cells are assumed to form aggregates, which behave as single bigger particles. The aggregation effect may be accounted for using a binary mixture model. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2012     

Stress effect of ethanol on fermentation kinetics by stationary-phase cells of Saccharomyces cerevisiae

When 4% (v/v) ethanol was added progressively to two strains exhibiting different fermentative abilities, K1 (a commercial wine strain) and V5 (a strain derived of a wine yeast), the fermentation rate correlated directly to the ethanol concentration for both strains. In contrast, the effect of sudden addition of 2%, 4% or 6% (v/v) ethanol was different depending on the strain. While the same effect was observed for K1 whatever the way of ethanol addition, V5 required an adaptation period after the shock addition of ethanol.     

The effect of sulfite on the yeast Saccharomyces cerevisiae

After a short period of tolerance, living cells of Saccharomyces cerevisiae were irreversibly damaged by low concentrations of sulfite. The length of the period of tolerance and the rate of the damaging effect depended on the concentration on sulfite, pH-value, temperature, the physiological state of the cells, and incubation time.Inhibitors of protein synthesis and mitochondrial ATP synthesis did not alter the deleterious effect of sulfite on living cells. Furthermore, cell damage leading to inhibition of colony formation occured under aerobic as well as under anaerobic conditions.Prior to cell inactivation sulfite induced the formation of respiratory deficient cells.The active agent was shown to be SO₂.     

百草枯和草甘膦对多刺裸腹溞的毒性效应

采用急性毒性实验方法研究了两种常见除草剂百草枯和草甘膦对多刺裸腹溞(Moina macrocopa)的48hLC50值,应用生命表实验方法研究了亚致死浓度的百草枯(0、0.01和0.04mg·L-1)和草甘膦(0、0.4和1.6mg·L-1)对多刺裸腹溞生命表统计学参数的影响。结果表明:百草枯和草甘膦对多刺裸腹溞的48hLC50值分别为0.626和26.287mg·L-1;百草枯浓度对多刺裸腹溞的生命期望、世代时间、净生殖率和种群内禀增长率有显著影响(P<0.01),草甘膦浓度对多刺裸腹溞的生命期望、世代时间和种群内禀增长率有显著影响(P<0.01),百草枯和草甘膦的交互作用对多刺裸腹溞的世代时间和种群内禀增长率有显著影响(P<0.01)。多重比较显示:当忽略草甘膦的影响时,0.01mg·L-1的百草枯使多刺裸腹溞的生命期望显著延长,而0.04mg·L-1的百草枯则相反,0.04mg·L-1的百草枯使多刺裸腹溞的净生殖率显著降低;当忽略百草枯的影响时,0.4和1.6mg·L-1的草甘膦均使多刺裸腹溞的生命期望显著缩短;与空白对照组相比,0.01mg·L-1的百草枯和1.6mg·L-1的草甘膦混合液使多刺裸腹溞的世代时间显著延长;而0.04mg·L-1的百草枯和0、0.4、1.6mg·L-1的草甘膦混合液均使多刺裸腹溞的世代时间显著缩短,种群内禀增长率显著降低。随着草甘膦浓度的升高,0.04mg·L-1的百草枯对多刺裸腹溞的毒性显著降低,表现出明显的拮抗作用。     

Proteomic analysis of a distilling strain of Saccharomyces cerevisiae during industrial grain fermentation

The fermentation performance of industrial yeast strains is influenced, among other things, by their genetic composition and the nature of the fermentable sugar, availability of nitrogen, and temperature. Therefore, to manipulate the fermentation process, it is important to understand, at a molecular level, the changes occurring in the yeast cell throughout industrial fermentation processes. With this aim in mind, using two-dimensional gel electrophoresis and matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF MS), we have examined the proteome of distillers yeast in an industrial context. Using yeast sampled from a local grain whisky distillery, we have prepared a detailed reference map of the proteome of distillers yeast and have examined in some detail the alterations in protein levels that occur throughout fermentation. In particular, as fermentation progresses, there is a significant increase in the levels of a variety of proteins involved in protecting against stress and nitrogen limitation. These results therefore give an insight into the stresses that yeast are exposed to in industrial fermentations and reveal some of the proteins and enzymes that are either necessary or important for efficient fermentation.     

The chronological life span of Saccharomyces cerevisiae

Simple model systems have played an important role in the discovery of fundamental mechanisms of aging. Studies in yeast, worms and fruit flies have resulted in the identification of proteins and signalling pathways that regulate stress resistance and longevity. New findings indicate that these pathways may have evolved to prevent damage and postpone aging during periods of starvation and may be conserved from yeast to mammals. We will review the yeast S. cerevisiae model system with emphasis on the chronological life span as a model system to study aging and the regulation of stress resistance in eukaryotes.     

Saccharomyces cerevisiae: the effect of different forms and concentrations of iodine on uptake and yeast growth

The essentiality of iodine for humans, especially in the early stages of life, is well recognized. The chemical forms of iodine in food supplements, infant formulae and iodated salt are either iodide (KI) or iodate (KIO₃). Because there are no or rare data about iodine uptake by yeasts, we investigated the influence of different sources of iodine, as KI, KIO₃ and periodate (KIO₄), on its uptake in and growth of the model yeast Saccharomyces cerevisiae . KIO₃ inhibited the growth of the yeast the most and already at a 400 μM initial concentration in the growth medium; the OD was reduced by 23% in comparison with the control, where no KIO₃ was added. The uptake of different iodine sources by the yeast S. cerevisiae was minimal, in total <1%. Tracer experiments with radioactive ¹³¹I added as KI showed that the yeast S. cerevisiae does not have the ability to transform KI into volatile species. We investigated the specificity of iodine uptake added as KIO₃ in the presence of Na₂SeO₄ or ZnCl₂ or K₂CrO₄ in the growth medium, and it was found that chromate had the most influence on reduction of KIO₃ uptake.     

The role of GAP1 gene in the nitrogen metabolism of Saccharomyces cerevisiae during wine fermentation

Aim:  The aim of this study was to analyse the relevance of the general amino acid permease gene ( GAP1 ) of the wine yeast Saccharomyces cerevisiae on nitrogen metabolism and fermentation performance.
Methods and Results:  We constructed a gap1 mutant in a wine strain. We compared fermentation rate, biomass production and nitrogen consumption between the gap1 mutant and its parental strain during fermentations with different nitrogen concentrations. The fermentation capacity of the gap1 mutant strain was impaired in the nitrogen-limited and -excessive conditions. The nitrogen consumption rate between the wild strain and the mutant was different for some amino acids, especially those affected by nitrogen catabolite repression (NCR). The deletion of GAP1 gene also modified the gene expression of other permeases.
Conclusions:  The Gap1 permease seems to be important during wine fermentations with low and high nitrogen content, not only because of its amino acid transporter role but also because of its function as an amino acid sensor.
Significance and Impact of the Study:  A possible biotechnological advantage of a gap1 mutant is its scarce consumption of arginine, whose metabolism has been related to the production of the carcinogenic ethyl carbamate.     

The effect of oxygen deficiency on the stability of the yeast Saccharomyces cerevisiae to the polyenic antibiotic nystatin

Oxygen deficiency was shown to affect the resistance of different Saccharomyces cerevisiae strains to nystatin, a polyenic antibiotic. This resistance decreased upon oxygen deficiency in the wild-type strains alpha'1 and 7A-P192 as well as in the mutant strains NYS 2, NYS 3 and NYS 4, but remained unchanged in the mutants NYS-1 and NYS 5. The qualitative composition of sterols was studied in the strains with a modified ergosterol synthesis, which were grown under the conditions of oxygen deficiency. Such conditions exerted a considerable effect on the accumulation of intermediate products in ergosterol biosynthesis.