不同来源ATP表征冷鲜羊肉新鲜度

【目的】通过系统研究冷鲜羊肉不同来源的三磷酸腺苷（adenosine triphosphate,ATP。包括肉中ATP、微生物ATP、肉表面ATP）在贮藏期间的变化规律,筛选能够表征冷鲜羊肉新鲜度变化的ATP指标,构建菌落总数和挥发性盐基氮预测模型,探究冷鲜羊肉新鲜度的预测新方法。【方法】以小尾寒羊背最长肌为试验材料,在空气密封包装0℃条件下分别贮藏0、1、3、5、7、9、11、13、15、17和21 d,分析冷鲜羊肉贮藏期间新鲜度指标（pH、色泽、挥发性盐基氮、菌落总数）与3种来源ATP（肉中ATP、微生物ATP、肉表面ATP）的变化,利用数据统计评价不同来源ATP的变化规律,并构建新鲜度指标的预测模型。【结果】冷鲜羊肉贮藏期间新鲜度指标菌落总数、挥发性盐基氮均呈现上升趋势,并均在贮藏17 d时超过国家标准限值;肉中ATP呈现不断下降趋势,微生物ATP与肉表面ATP均呈现上升趋势,与新鲜度指标变化趋势保持一致;冷鲜羊肉贮藏期间,肉中ATP、微生物ATP、肉表面ATP含量与菌落总数、挥发性盐基氮的相关系数（R）分别为-0.399、0.910、0.943和-0.357、0.725、0.907。肉表面ATP预测冷鲜羊肉菌落总数的最优模型为Boltzmann拟合模型,其公式为TVC（lg cfu/g）=7.649-4.069/(1+exp(x-5.807)/0.632)（R ²=0.903,P<0.001）,肉表面ATP预测冷鲜羊肉挥发性盐基氮的最优模型为Expedc1拟合模型,其公式为TVB-N（mg/100 g）=2.493*exp(x/3.745)+3.057（R ²=0.888,P<0.001）。【结论】本研究明确了冷鲜羊肉表面ATP与菌落总数、挥发性盐基氮存在显著正相关性,确证了肉表面ATP可以作为冷鲜羊肉新鲜度表征指标;并构建了菌落总数和挥发性盐基氮最优预测模型,为冷鲜羊肉新鲜度快速检测提供了新的思路。     

亚热带天然林转变为毛竹林和茶园对土壤胞外酶活性的影响

为揭示我国亚热带地区天然林转变为毛竹林和茶园后土壤胞外酶活性（Extracellular enzyme activities,EEAs）的变异特征及关键驱动因子,以浙江省安吉县的天然林土壤及天然林转变的粗放经营毛竹林和集约经营茶园土壤为研究对象,测定了土壤EEAs及若干环境因子参数,通过冗余分析等分析方法筛选出了影响土壤EEAs的关键驱动因子。结果表明：与天然林相比,粗放经营毛竹林和集约经营茶园土壤酸性磷酸酶（Acid phosphatase,ACP）活性均显著降低,酚氧化酶（Phenol oxidase,POX）活性均显著升高;粗放经营毛竹林土壤亮氨酸氨基肽酶（Leucine aminopeptidase,LAP）活性显著升高;集约经营茶园土壤β-葡萄糖苷酶（β-1,4-glucosidase,BG）、纤维二糖水解酶（Cellobiohydrolase,CBH）、N-乙酰-β-D氨基葡萄糖苷酶（β-1,4-N-acetyl-glucosaminnidase,NAG）活性均显著降低。由以上结果可推知,与天然林相比,茶园土壤氮、磷养分相对充足,毛竹林土壤的磷限制有所缓解,茶园和毛竹林土壤中微生物以惰性碳作为主要的能量来源。此外,冗余分析表明,土壤pH在环境因子中的贡献率最高,是土壤总体EEAs变化的关键驱动因子。综上所述,相比天然林,转变后的粗放经营毛竹林和集约经营茶园土壤EEAs发生了明显变化,土壤pH作为关键驱动因子解释了亚热带地区天然林转变为毛竹林和茶园后土壤总体EEAs的改变。     

A review of extracellular virulence product of Vibrio species important in diseases of cultivated shrimp

Shrimp aquaculture is an important industry that experiences significant losses from Vibrio species, especially at the larval and juvenile stages. Proteinaceous virulence factors, including alkaline proteases, metalloproteases, cysteine proteases and alkaline serine proteases, have been identified as important elements in Vibrio pathogenesis. This review summarizes current knowledge regarding the principal pathogenic Vibrio species in shrimp, with emphasis on relevant exotoxins and their modes of action, principal characteristics and molecular database. This pathogenic factors and their relation with other molecules produced by microorganisms may be help to understand the virulence mechanisms present in Vibrio strain.     

鳜嗜水气单胞菌GYK1株胞外产物提取、纯化及生物学活性分析

以鳜分离的嗜水气单胞菌GYK1株为代表,采用玻璃纸覆盖技术提取了8株嗜水气单胞菌和1株温和气单胞菌的胞外产物,SDS-PAGE电泳分析显示,8株嗜水气单胞菌的胞外产物均有35kDa的共同蛋白带。酶活性和溶血性分析表明,GYK1株胞外产物具有酪蛋白酶、淀粉酶、脂肪酶、明胶酶活性,但不具备脲酶活性;溶血性较强,蛋白浓度为365μg·mL-1的胞外产物对鳜血细胞的溶血价为213,对加州鲈、银鲫、小白鼠、兔、绵羊、人O型血的红细胞的溶血价在211~214之间。应用聚丙烯酰胺葡聚糖凝胶柱层析,对GYK1株的胞外产物进行了初步纯化,得到分子量为35kDa的蛋白带,该纯化产物具溶血性,但溶血性比粗胞外产物降低,对鳜和小鼠血细胞的溶血价均为25。     

Recording cerebellar neuron activities in swimming goldfish

ABSTRACT:   Neuronal activities were investigated in the cerebellum of immobilized and swimming goldfish Carassius auratus . Extracellularly recorded neural activities of the cerebellum in immobilized goldfish were characterized and classified into five types. Based on the waveforms and recording depths, these five neural activity types were estimated to originate from three identified classes of cerebellar neurons: Purkinje cells, eurydendroid cells, and granule cells. Chronic recording of cerebellar neuron activities in unrestrained goldfish was performed for more than 100 h. During the chronic recordings, a submersible amplifier attached to the goldfish head, and a multielectrode array developed for the present study were used. Neuronal activities in the cerebellum of free-swimming fish could also be classified into five types as in the immobilized condition. Firing patterns of two neurons identified as Purkinje cells and eurydendroid cells were analyzed during turning movements of the goldfish. The firing patterns of these neurons changed in relation to turning movements. Although some improvements are required, the chronic recording method developed in the present study can be applied to further investigations concerning the direct relationship between brain neural activities and certain behavior.     

A study of goldfish oocyte meiosisin vitro: effects of 2,4-dinitrophenol and adenosine-5-triphosphate

Germinal vesicle migration (GVM) and/or dissolution (GVD) were measured in goldfish oocytes, treated with 17α, 20β dihydroxyprogesterone (DHP) and other compounds considered to effect the cytoskeleton and oxidative phosphorylation,in vitro. Administration of DHP reinitiated meiotic maturation, increasing GVM and GVD in goldfish oocytes. Addition of 2,4-dinitrophenol (DNP) to the incubation medium significantly inhibited DHP-induced GVM and GVD. The DNP effect was found to be partially reversible after 24 h and could be reversed fully after a further delay of approximately 24h. Treatment of goldfish oocytes with demecolcine (DE; a colchicine derivative also known as colcemid) induces GVM to the micropyle without effecting GVD; while Cytochalasin-B which inhibits microfilament polymerization impairs both GVM and GVD. Administration of DNP, significantly inhibited DE-induced GVM, suggesting that GVM as well as GVD are dependent upon the process of oxidative phosphorylation. Addition of adenosine-5′ -triphosphate (ATP) at low concentrations (0.01–0.1 mM) did not effect DHP-induced or DNP-inhibited GVD in goldfish oocytes. The present results are consistent with the idea that migration of the oocyte nucleus during meiosis reinitiation has an energy requirement and involves participation by the cytoskeleton.     

添加秸秆对水稻产量和土壤碳氮及微生物群落的影响

为探究添加秸秆对黄筋泥田水稻产量和土壤碳、氮含量和微生物学特性的影响,设计了5个处理,即不添加秸秆和生物炭（CK）、添加秸秆（ST）、添加秸秆和腐熟剂1号（SB1）、添加秸秆和腐熟剂2号（SB2）和添加秸秆生物炭（SC）的水稻盆栽试验,分析水稻产量和土壤全碳、全氮、腐殖质含量和磷脂脂肪酸含量。结果表明：与CK相比,ST、SB1、SB2和SC均能提高水稻产量（P<0.05）,其中SB2增产55.73%;ST、SB1、SB2和SC也提高土壤全碳、全氮、腐殖质含量、细菌磷脂脂肪酸含量、真菌磷脂脂肪酸含量和总磷脂脂肪酸含量（P<0.05）,其中SC土壤全碳提高31.36%,SB2土壤全氮提高40%,SB1腐殖质含量增加50.01%,而SB1和SB2的细菌磷脂脂肪酸含量、真菌磷脂脂肪酸含量和总磷脂脂肪酸含量增加86.49%～401.59%。因此,添加秸秆可以增加水稻产量,提高土壤全碳、全氮和腐殖质的含量,改善土壤微生物群落结构。     

黄土丘陵区垂直陡壁表面不同类型生物土壤结皮养分与微生物养分限制特征

生物土壤结皮的发育类型对土壤养分和微生物代谢起着重要作用。为进一步明确在生物结皮发育过程中微生物的限制性养分与影响因素,研究选择黄土丘陵区垂直陡壁表面上的裸土(CK)、浅色藻结皮(LA)、深色藻结皮(DA)、藻藓混合结皮(AM)和藓结皮(M)为研究对象,分析了不同生物土壤结皮类型下碳(C)、氮(N)、磷(P)养分状况与胞外酶活性,并通过胞外酶化学计量来量化微生物的代谢限制。结果表明:LA,DA,AM和M这4种类型生物土壤结皮C,N,P养分含量和微生物生物量C,N,P均显著高于CK(p<0.05),并且SOC,TN,TP和微生物生物量C,N,P随CK,LA,DA,AM和M的顺序逐渐增大,藓结皮微生物量C,N,P分别是CK处理的18.3,27.6,14.1倍。生物土壤结皮的发育显著提高了C,N,P循环酶的活性,冗余分析结果表明土壤养分与酶活性密切相关。此外,通过酶计量的矢量模型结果来看,生物土壤结皮的发育造成微生物相对碳限制的增大与相对磷限制的减小,并受到速效养分含量的影响。偏最小二乘路径模型结果也表明生物土壤结皮的类型会间接影响微生物的代谢限制。总的来说,生物土壤结皮类型的变化会改善土壤养分状况与微生物量等性质,养分资源的供应状况会造成微生物养分代谢的变化。     

苔藓结皮及其下层土壤的胞外酶活性与微生物CUE特征

为进一步明确苔藓结皮对下层土壤养分的影响及微生物对养分的利用特征,以黄土丘陵区典型退耕地上发育的苔藓结皮及其下层土壤(0—2 cm,2—5 cm,10—20 cm)为研究对象,分析在剖面尺度下土壤碳(C)、氮(N)、磷(P)养分状况、胞外酶活性以及微生物CUE特征。结果表明:苔藓结皮显著提高了表层土壤养分含量,结皮层的SOC,TN,TP,DOC,DON和Olsen-P含量分别是10—20 cm土壤养分的2.58,2.34,1.13,2.30,4.30,7.36倍。与养分含量特征一致,微生物生物量随土层深度的增加逐渐降低。在整个剖面尺度上,微生物群落存在较为稳定的元素内稳态以保持自身C,N,P的计量平衡。参与C,N,P循环的相关胞外酶活性在剖面尺度上表现出差异,β-1,4-葡萄糖苷酶(BG)随深度增加逐渐降低,而β-1,4-N-乙酰氨基葡萄糖苷酶(NAG)和碱性磷酸酶(AP)则表现为先降低后增加的趋势,底层土壤较高的NAG和AP酶活性反映出N,P养分的匮乏。微生物CUE在剖面尺度上表现为先降低后增加的趋势,平均水平为0.25,表明表层与深层土壤更有助于C的固存。此外,方差分解(VPA)和线性模型结果均指出养分状况和土壤酶是影响微生物CUE的关键因素。总的来说,苔藓结皮对表层土壤的养分和微生物代谢产生积极作用,尽管底层土壤养分匮乏,但仍保持较高的微生物C利用效率。     

不同碳氮源对苹果树腐烂病菌胞外果胶酶活性的影响

【目的】探索苹果树腐烂病菌致病力与胞外果胶酶的关系,筛选最佳产酶的碳、氮源,为揭示该病菌致病机理提供依据。【方法】用MS培养基培养苹果树腐烂病菌野生型菌株03-8及其2个突变体(致病力增强突变体X907,致病力丧失突变体T1)菌株,于5,10,15和20d取样,用3,5-二硝基水杨酸(DNS)比色法测定其培养滤液中果胶酶的活性,探讨致病力与酶活性的关系。以野生型菌株03-8为供试菌株,改变MS培养基中的碳(葡萄糖、麦芽糖、根皮苷、果胶、可溶性淀粉)、氮(硫酸铵、牛肉膏、蛋白胨、酵母膏、L-天门冬酰胺)源培养03-8菌株,于5,10,15和20d取样,分别测定各培养滤液中果胶酶的活性,确定最佳碳氮源。用不同含量的最佳碳、氮源与MS培养基培养03-8菌株,10d时取样,测定胞外果胶酶活性,确定培养基中最佳碳、氮源的含量。【结果】在MS培养基中发酵10d,苹果树腐烂病菌致病力增强突变体(X907)产生的胞外果胶酶活性最高,致病力丧失突变体(T1)产生的酶活性最低。用可溶性淀粉、果胶为碳源培养野生型菌株03-8,在第10天培养滤液中果胶酶活性均高于其他供试碳源;以可溶性淀粉为碳源,其含量为0.5%时培养滤液中果胶酶活性最高。在5种供试氮源中,以0.25%蛋白胨为氮源发酵10d产生的胞外果胶酶活性最高。【结论】3种苹果树腐烂病菌发酵10d产生的胞外果胶酶的活性与其致病力相关;含0.50%可溶性淀粉和0.25%蛋白胨的MS培养基为苹果树腐烂病菌产酶的最佳培养基,发酵10d培养滤液中果胶酶的活性最高。