高氨氮利用酵母菌的筛选及相关酶活性

[背景]蛋白饲料的缺乏,促进了蛋白含量高、安全性能好的酵母类单细胞蛋白的研究与应用.[目的]筛选氨氮利用能力强的菌株,为单细胞蛋白的发酵提供优良菌株.[方法]从土壤、奶制品、水果采集样品分离酵母菌,根据形态学和分子生物学鉴定菌株,然后以硫酸铵为唯一氮源培养基,测定菌落大小、菌体干重、蛋白质含量,复筛氨氮利用率高的酵母菌...     

云南高原湖泊抚仙湖和星云湖的酵母菌胞外酶活性

【背景】高原湖泊因其海拔高、气压低、辐射强、氧气含量低,是一类特殊环境,而其中的微生物是高原湖泊生态系统物质循环与能量流动的重要参与者,其胞外酶活性的表现决定其适应这一特殊环境的方式与能力。【目的】对分离自云南高原湖泊抚仙湖和星云湖湖水的酵母菌进行产胞外酶活性的筛选,以期获得具有潜在应用价值的活性菌株。【方法】在5°C和25°C培养温度下,采用平板筛选法对两个湖泊酵母菌进行产胞外蛋白酶、纤维素酶、淀粉酶、脂肪酶、几丁质酶、木聚糖酶、植酸酶、菊粉酶、漆酶、锰依赖过氧化物酶和木质素过氧化物酶活性的筛选。【结果】抚仙湖和星云湖的所有测试酵母菌菌株至少都能产1种胞外酶,且主要产植酸酶、菊粉酶和淀粉酶;其次为脂肪酶、纤维素酶、木聚糖酶、锰依赖过氧化物酶和木质素过氧化物酶;产几丁质酶、蛋白酶和漆酶的酵母菌很少,星云湖酵母菌都不产漆酶。培养温度为5°C时,抚仙湖和星云湖的酵母菌产5种及5种以上胞外酶的活性菌株数均多于25°C。【结论】抚仙湖和星云湖的酵母菌产胞外酶菌株多样性丰富,胞外酶种类多样,产酶酵母菌可能参与高原湖泊生态系统的物质循环;筛选得到的产胞外酶菌株为开发与利用高原湖泊酶资源提供了良好的种质资源,具有进一步研究的价值。     

控释尿素和普通尿素配比对不同氮效率玉米叶片衰老特性和土壤酶活性的影响

控释尿素和普通尿素配比施用可以同步玉米氮素需求,延缓后期衰老,增加产量。本试验以黄淮海区域两种氮效率玉米作为对象,研究控释尿素和普通尿素不同配比对其叶片衰老特性、土壤酶活性和土壤无机氮的影响。试验选取黄淮海主栽玉米品种豫禾988（氮低效）和郑单958（氮高效）作为试验材料,设置6个施氮处理（CK、N180U、N180C1、N180C2、N180C、N300U）,其中CK为不施氮处理,180、300代表施氮水平分别为180 kg/hm²和300 kg/hm²,U代表全尿素处理（基肥：追肥=2：3）,C1、C2分别代表控释氮：尿素氮为1：2和2：1（基肥一次施用）,C代表全控释尿素处理（基肥一次施用）。2018-2019年结果表明：与CK相比,豫禾988在N180C1和郑单958在N180C2处理下,能够在玉米生育后期显著提高穗位叶超氧化物歧化酶（SOD）和过氧化物酶（POD）活性,降低膜脂过氧化物（MDA）含量,同时也增加了土壤无机氮含量、脲酶和蔗糖酶活性。综上所述,针对不同氮效率玉米品种,通过控释尿素和尿素合理配施,利用速效氮和控释氮的释放来延缓玉米功能叶片衰老,延长功能期,提高生育后期土壤无机氮含量和酶活性,共同促进玉米生长,增加玉米产量,其中豫禾988和郑单958分别在N180C1和N180C2处理下效果最佳。     

控释掺混尿素对稻、麦土壤氮与酶活性的影响

通过大田试验,共设7个处理,即不施氮、常规施肥以及掺混控释氮肥10%、20%、40%、80%、100%处理,探讨了不同施肥处理对土壤中4种形态氮(全氮、铵态氮、硝态氮、微生物生物量氮)和3种氮功能性酶(脲酶、蛋白酶、硝酸还原酶)活性的影响,以探究控释掺混尿素对稻、麦土壤肥力和环境的影响.结果表明: 土壤全氮在稻、麦全生育期内趋于稳定,且掺混比例20%以上各控释氮肥处理在稻、麦季均无显著差异;掺混40%以上控释氮肥能有效促进稻、麦生育中后期土壤无机氮水平;随稻、麦生育期推进,掺混40%以上控释氮肥处理可显著提高土壤微生物生物量氮,但常规施肥处理的微生物生物量氮整体呈明显下降趋势;掺混40%以上控释氮肥能明显提升稻、麦生育中后期土壤酶活性,土壤蛋白酶与硝酸还原酶活性在作物生育后期均随掺混比例增加而提高,以100%控释氮肥处理土壤酶活性最高.掺混20%以上控释氮肥处理能明显降低水稻季分蘖期脲酶活性,推迟铵态氮峰值期,有利于减少氮损失;掺混40%以上控释氮肥处理均可保障稻、麦生育中后期的氮素供应,刺激土壤脲酶与蛋白酶参与氮素转换,促进了土壤氮素有效性;100%控释氮肥处理对稻、麦生育后期土壤硝酸还原酶活性增加最明显,与掺混40%～80%控释氮肥处理相比,可显著减少小麦季20～40 cm土壤硝态氮残留量,在减少氮素损失方面的效果明显.     

酵母出芽细胞电镜观察、颜色反应与尿素酶活性的比较研究

观察了6个属的1 2株酵母菌出芽时的胞壁结构、重氮基蓝色B盐颜色反应和尿素酶活性,认为出芽型和颜色反应二者有相关性,可以说明这些属种之间的亲缘关系。     

医院内假丝酵母菌感染菌种的分布及耐药分析

目的了解医院内假丝酵母菌感染菌种的分布及抗真菌药物的耐药谱,为临床抗真菌治疗提供正确数据。方法采用VITEK-32微生物自动鉴定仪进行假丝酵母菌菌种的鉴定,同时用ATB FUNGUS真菌药敏条作药敏试验。结果从住院患者的血液、痰、尿、分泌物、胆汁等标本中共检出真菌505株。其中白假丝酵母菌281株,热带假丝酵母菌124株,光滑假丝酵母菌21株,季也蒙假丝酵母菌17株,近平滑假丝酵母菌16株,克柔假丝酵母菌10株,皱折假丝酵母菌8株,异常汉逊假丝酵母菌6株,5氟-胞嘧啶和两性霉素抑菌效果最好,其耐药率分别为2.8%和3.4%。其他4种抗真菌药物制霉菌素、氟康唑、伊曲康唑和酮康唑的耐药率分别为6.1%、13.7%、9.3%和28.3%。结论医院假丝酵母菌感染耐药率逐年上升,非白假丝酵母菌感染明显增加。氟康唑对白假丝酵母菌有很强的抗菌活性且毒副作用小。假丝酵母菌感染的迅速增加同广泛应用超广谱抗菌药物、激素及免疫抑制剂等有关。假丝酵母菌感染死亡率高,因此早期诊断及有效性治疗是减少死亡率的关键。     

春季海南岛近岸海域尿素与浮游生物的脲酶活性

2011年春季(4-5月),对海南岛的海口湾、澄迈湾、文昌八门湾、陵水新村湾和大东海5个海湾的尿素浓度及浮游生物的脲酶活性开展调查研究,结合其它理化环境因子,分析海南岛近岸海域尿素的可利用性及其对该海区浮游植物生长可能产生的影响.结果表明,海南岛近岸水体中尿素平均浓度为2.07-3.30 μmol/L,占总溶解态氮TDN含量的14％-38％,尿素占TDN比例由北向东、南方向递增.浮游生物脲酶活性为0.30-0.84 μmolN· L-1· h-1,海口湾最高,从北部向东、南部逐渐减少.各海湾较高水平的尿素和脲酶活性主要分布在排污口、养殖区或旅游区的近岸海域.硅藻为优势种,甲藻种类少且密度低,部分甲藻密度达到104-105个/L的水体,尿素和脲酶活性也处于较高水平.海区浮游植物细胞密度与脲酶活性或尿素占TDN比例等因子存在相关性,表明尿素是海南海域浮游植物生长不可忽略的重要氮源.尿素在一定程度上促进春季海南岛近岸海域甲藻等浮游植物的生长,可能对浮游植物群落结构的改变产生重要影响.     

酵母各属间颜色反应、尿素酶活性和发酵力的比较

本文对比了28个属、37个种、74株酵母的颜色反应、分解尿素能力以及发酵力的关系,并讨论了这些特性与其它特征(如DNA碱基组成等)的一致性。这种一致性说明了一些无孢子酵母的亲缘关系。     

不同土层深度配施缓释/普通尿素对土壤氮素和酶活性及玉米产量的影响

通过2017-2018两年田间试验,研究了不同土层深度配施缓释(PCU)/普通尿素(PU)对0～ 30 cm土层土壤无机氮含量、酶活性和玉米产量的影响.试验设置不施氮肥(CK)、普通尿素一次施肥(PU1,5～10 cm土层)、普通尿素传统两次施肥(PU2,5～ 10 cm土层,60％种肥+40％追肥)、普通尿素一次分层...     

我国沙拐枣属的分类与分布

我国沙拐枣属共24种,占本属的2／3。亚洲中部是该属的起源地。我国是该属分布区的最东端,它主要分布在新疆和甘肃等省(区)。     

K+ fluxes in Schizosaccharomyces pombe

All living cells accumulate high concentrations of K+ in order to keep themselves alive. To this end they have developed a great diversity of transporters. The internal level of K+ is the result of the net balance between the activities of the K+ influx and the K+ efflux transporters. Potassium fluxes have been extensively studied and characterized in Saccharomyces cerevisiae. However, this is not the case in the fission yeast and, in addition, the information available indicates that both yeasts present substantial and interesting differences. In this paper we have reviewed and summarized the information on K+ fluxes in Schizosaccharomyces pombe. We have included some unpublished results recently obtained in our laboratory and, in particular, we have highlighted the significant differences found between the well-known yeast S. cerevisiae and the fission yeast Sch. pombe.     

Genetic analyses of yeast protein serine/threonine phosphatases

Abstract Protein phosphorylation is an important regulatory phenomenon in yeasts just as in other eukaryotic cells and controls a wide variety of cellular processes. The importance of protein phosphatases as well as protein kinases as key elements in such control is becoming increasingly clear. Over the past four years since the first yeast protein phosphatase gene was isolated, many more such genes have been described and the number of genes encoding protein phosphatase catalytic subunits in Saccharomyces cerevisiae has comfortably entered double figures. Given the genetic approaches available, yeasts offer powerful systems for addressing the cellular roles of these enzymes. This review summarises the results of genetic studies aimed at determining the functions of protein serine/threoninc phosphatases in yeast.     

On the role of Trk1 and Trk2 in Schizosaccharomyces pombe under different ion stress conditions

Trk1 and Trk2 are the major K(+) transport systems in Schizosaccharomyces pombe. Both transporters individually seem to be able to cope with K(+) requirements of the cells under normal conditions, since only the double mutant shows defective K(+) transport and defective growth at limiting K(+) concentrations. We have studied in detail the role of SpTrk1 and SpTrk2 under different ion stress conditions. Results show that the strain with only Trk1 (trk1(+)) is less sensitive to Li(+) and to hygromycin B, it grows better at low K(+) and it survives longer in a medium without K(+) than the strain expressing only Trk2 (trk2(+)). We conclude that Trk1 contributes more efficiently than Trk2 to the performance of the fission yeast under ion stress conditions. In the wild type both trk1(+) and trk2(+) genes are expressed and probably collaborate for the performance of the cells.     

细菌脲酶蛋白复合物UreABC的表达与纯化

细菌脲酶能分解尿素为氨,在瘤胃尿素氮代谢中发挥重要作用.为了表达纯化并研究蛋白脲酶复合物UreABC,通过PCR扩增脲酶基因簇的结构基因ureA、ureB、ureC,将ureB构建在含有N端His标签的pet28a+载体,ureA、ureC基因共同构建在含有N端His标签的表达载体pETDuet-1,经酶切及测序鉴定得...     

Assessment of yeast diversity in a marine environment in the south of portugal by microsatellite-primed PCR

The occurrence and diversity of yeasts in seawater was investigated in a study site located 20 Km off Faro, Portugal, above the álvares Cabral Trench. A total of 43 water samples from different layers (above the permanent thermocline, under the thermocline and near the bottom) and directly from the surface, originated 234 isolates. All the isolates were identified using a molecular approach that included, in a first stage, MSP-PCR fingerprinting. A total of 31 MSP-PCR classes were formed, 8 for the pigmented yeasts and 23 for the non-pigmented yeasts. The pink coloured isolates were identified by direct comparison of the new fingerprints with those obtained for representative strains of the various species. For identification of the non-pigmented yeasts, a representative isolate of each MSP-PCR class was selected for sequence analysis and compared with reference sequences. The five most abundant yeast species were Sakaguchia dacryoidea, Pseudozyma aphidis, Rhodosporidium babjevae, R. diobovatum and Debaryomyces hansenii. The distribution of isolates and species in the major taxonomic groups indicated that the number of basidiomycetous yeasts and their diversity are prevalent in relation to their ascomycetous counterpart. Diversity indices were determined and superficial water and water near the bottom had the highest diversity. The sampling effort effectiveness was estimated, and found to correspond to approximately 60% of the species present. MSP-PCR identification proved suitable for pigmented basidiomycetous yeasts and, when used in conjunction with sequence analysis, was effective for the characterization of non-pigmented populations. Our results indicate that the MSP-PCR fingerprinting method is appropriate for the characterization of large groups of isolates due to its simplicity and good reproducibility. This revised version was published online in August 2006 with corrections to the Cover Date.     

Functional expression of human P-glycoprotein in Schizosaccharomyces pombe

Human MDR1 cDNA was introduced into the human cultured cells KB-3-1 and Schizosaccharomyces pombe pmdI null mutant KN3. The drug sensitivity of KB-G2 and KN3/pgp, expressing human P-glycoprotein, was examined. KB-G2 was resistant to the peptide antibiotics valinomycin and gramicidin D as well as having a typical multidrug resistance (MDR) phenotype. KN3/pgp was resistant to valinomycin and actinomycin D, but not to adriamycin. The ATP-hydrolysis-deficient mutant did not confer KN3 resistance to these antibiotics. Human P-glycoprotein expressed in S. pombe seemed to lack N-glycosylation. The N-glycosylation-deficient mutant, however, conferred a typical MDR phenotype on KB-3-1. These results suggest that human P-glycoprotein functions as an efflux pump of valinomycin and actinomycin D in the membrane of S. pombe.     

A rapid permeabilization procedure for accurate quantitative determination of β-galactosidase activity in yeast cells

Abstract A procedure is described which allows the rapid permeabilization of yeast cells, Schizosaccharomyces pombe and Saccharomyces cerevisiae , for quantitative in situ assays of β-galactosidase activity. Yeast cells are permeabilized by incubation in buffer containing 0.2% of the detergent sodium lauroyl sarcosinate without any need for washing or vortexing. This procedure is equally applicable to fresh and frozen samples. It is compared to earlier reported methods and found to be superior by being more accurate and less time-consuming.     

Analyses of stress resistance under laboratory conditions constitute a suitable criterion for wine yeast selection

During wine production, yeast cells are affected by several conditions that are adverse to growth (oxidative, osmotic and ethanol stress among others) and they should detect and respond to these conditions, otherwise alcoholic fermentation can be negatively affected. In this work we have analyzed the fermentative behaviour of 14 commercial and non-commercial strains in several synthetic musts. According to the data obtained these strains have been classified into three groups depending on whether or not vinification was completed (and on the amount of residual sugar remaining in the must if it was not). Moreover, we have determined the resistance of these strains to several stress situations under laboratory growth conditions. We have been able to establish a correlation between the groups based on fermentative behaviour and resistance to several stress conditions (especially oxidative and ethanol stress), by applying discriminant analysis to the data obtained in these experiments. Our results indicate a clear relationship between stress resistance and fermentative behaviour and this opens up the possibility of using this information as a criterion for the future selection of wine yeasts.     

Urease and urea amidolyase: Determination of activity in liverworts

Using highly sensitive techniques, we have investigated urea degradation in the liverworts and found that they have high urease but no detectable urea amidolyase activity.