碳、氮对茄病镰刀菌与棘孢木霉菌丝生长及产孢的影响

为了解茄病镰刀菌与棘孢木霉对碳源、氮源的需求,试验在培养基I与培养基II的基础上调整碳源、氮源及C/N比,测定碳源、氮源对茄病镰刀菌和棘孢木霉菌丝生长量与产孢量的影响。结果表明,碳源对茄病镰孢菌生长的影响不明显,甘露醇有利于其产孢;氮源对茄病镰孢菌生长的影响显著,硝酸钠最有利于菌丝生长,磷酸氢二铵有利于其菌丝生长与产孢;C/N比值对茄病镰孢菌菌丝生长及产孢的影响显著,C/N达到12∶1时,菌落直径6.55 cm,每毫升产孢量3.36×10~6个。碳源对棘孢木霉菌丝生长的影响不明显,蔗糖和葡萄糖有利于其生长与产孢;氮源对棘孢木霉菌丝生长的影响显著,磷酸二氢铵与硝酸钠均有利于菌丝生长,磷酸氢二铵有利于其产孢;C/N比值对棘孢木霉菌丝生长及产孢的影响显著,C/N达到9∶1时,菌落直径6.20 cm,每毫升产孢量1.45×10~7个。     

植物精油海藻酸钠复合膜对双孢蘑菇的抑菌保鲜效果研究

为了研究植物精油对双孢蘑菇贮藏期主要腐败菌的抑制效果,该文以新鲜双孢蘑菇为试验材料,分离、纯化并鉴定引起双孢蘑菇贮藏期腐败的主要病原菌;通过体外抑菌活性试验,筛选出抑菌效果较好的植物精油,并将此精油应用于复合膜的保鲜试验中,验证其抑菌保鲜效果。通过对双孢蘑菇主要致腐微生物进行分离、纯化得到9株单菌落,经致病性试验得到主要病原真菌为3号菌,对该病原菌18S rDNA序列进行进化树分析,确定其为丰孢木霉菌(Trichoderma sp.)。选用姜黄、连翘、桉叶、当归4种精油对3号菌菌株进行抑菌活性试验,筛选出较优精油种类及浓度。结果表明,桉叶油对丰孢木霉菌的抑制效果最好,其次是连翘油,姜黄油和当归油无明显抑制作用。桉叶油最小抑菌浓度(minimum inhibitory concentration, MIC)为0.312 5μL/mL,最小杀菌浓度(minimum bactericidal concentration, MBC)为0.625μL/mL;连翘油MIC为0.625μL/mL,MBC为1.25μL/mL。通过对海藻酸钠/桉叶油复合膜和海藻酸钠单一膜的性能指标进行测定和对比发现,桉叶油的添加可显著提高膜的气体阻隔性能和机械性能。分别用海藻酸钠/桉叶油复合膜、海藻酸钠单一膜和普通PE膜对双孢蘑菇进行保鲜试验,结果表明,添加桉叶油的复合膜可有效降低双孢蘑菇子实体的衰老和致病腐烂,具有显著的抑菌保鲜效果。该研究结果可为双孢蘑菇贮藏期防腐和天然杀菌保鲜剂的选择提供一定的理论依据。     

广西龙眼真菌性病害种类调查初报

根据近几年的调查，共发现广西龙眼真菌性病害14种，其中桂圆拟茎点霉菌Phomopsis guiyuan、龙眼拟茎点霉菌Phomopsis longanae、龙眼壳二孢菌Ascochyta longan、细莲格孢菌Alternaria alternata为广西首次报道，而文中描述的龙眼盘二孢菌Marssonina dimocarpi和龙眼叶点霉菌Phyllosticta dimocarpi为新种，龙眼顶多毛孢菌Bartalinia bischofiae为国内新记录种。假链格孢菌Nimbya sp．尚需进一步鉴定。     

牛粪堆肥各阶段主要纤维素降解菌分离与作用规律分析

以纤维素降解率和糖生成率为主要指标,对堆肥各阶段主要纤维素降解菌进行分离筛选,并对其作用规律进行了初步研究.结果表明,纤维素降解分为转化为堆肥有机质及糖等小分子物质两个方面;堆肥早期糖生成量相对较多,对发酵微生物生长及堆体升温具有重要作用;堆肥中后期则更多转化为堆肥有机质,对腐殖质形成具有重要作用;嗜纤维菌、假单胞菌,小单孢菌、纤维单胞菌、纤维弧菌、芽孢杆菌,高温放线菌、小多孢菌、链霉菌、曲霉,小单孢菌、木霉、青霉、曲霉、芽孢杆菌等分别为低温、中温、高温、降温阶段纤维素降解主要功能菌;以纤维素降解率和糖生成率作为研究和筛选纤维素降解菌的主要指标,具有重要应用价值.     

外来入侵植物刺萼龙葵（Solanum rostratum Dunal）根际土壤真菌多样性及其次生代谢产物的化感作用研究

  目的  分析外来入侵植物刺萼龙葵根际土壤真菌群落多样性,了解其根际可培养真菌次生代谢产物的植物生长调节活性,并从中筛选具有开发为植物生长调节剂及生物除草剂潜力的菌株。  方法  采集刺萼龙葵根际土壤,提取总DNA,利用高通量测序技术分析土壤真菌群落多样性;同时,利用纯培养手段获得可培养真菌菌株,以乙酸乙酯萃取其发酵产物,并以单子叶植物早熟禾和双子叶植物反枝苋为受试植物,检测其次生代谢产物的促生/抑生活性。  结果  子囊菌门真菌广泛存在于刺萼龙葵根际土壤中,且占绝对优势。Alpha多样性分析发现,刺萼龙葵根际土壤中真菌群落有着非常高的多样性和丰富性。此外,菌株SR02、SR05和SR13对受试植物具有较强的生长抑制作用。  结论  刺萼龙葵根际土壤真菌优势类群明显,尖孢镰刀菌和链格孢在真菌群落中占优势地位;从根际土壤中发现多个具有显著生长促进或抑制作用的菌株,其在刺萼龙葵根际土壤中所起到的生理生态学意义,以及其次生代谢产物是否具有开发为植物生长调节剂及生物农药的潜力,值得进行深入的研究。     

枸杞鲜果霉变菌种分离鉴定及其生物学特性

为确定引起枸杞霉变的菌种类型,该文以采后鲜枸杞果实为材料,分离导致其霉变的菌种,经形态学特征及分子生物学特征鉴定确定类型,并对与其霉变速率相关的部分生物学特性进行研究。结果表明:从霉变的鲜枸杞中共分离出6株致霉菌,分别鉴定为:菌种1为镰刀菌、菌种2为交链孢霉、菌种6为尖孢镰刀菌、菌种7为青霉菌、菌种11为串珠状赤霉菌及菌种21为草酸青霉。经过回接试验发现6种霉菌均能使健康枸杞鲜果霉变,从这些病斑中再次分离得到相同霉菌。6种菌的致死温度不同,最高致死温度为54℃。菌种1的最适生长温度为40℃,菌种6的最适生长温度为35℃,其余4株菌的最适生长温度均为25℃。6种菌在相对湿度为30%~90%范围内均能生长,最适生长相对湿度为75%~85%。最适p H值范围为4~8,p H值为6时霉菌孢子萌发率最高。通过对6种霉菌与温度、相对湿度、p H值3个与干燥参数相关的生物学特性研究,为今后鲜枸杞干燥过程条件的控制提供理论依据。     

NTG诱导及核辐射改良稗草生防潜力菌研究

用亚硝基胍 (nitrosoguanidine ,NTG)诱变稗草生防潜力菌禾长蠕孢稗草专化型菌株(HGE) ,获得诱变菌株I2 62 ,其孢子产量比原始菌株 (HGE)提高 5 2 6%。以I2 62 为出发菌株 ,用60 Coγ射线 65 0Gy辐照 5 7min ,有 7 75 %的菌株产孢量高于出发菌株高 ,其中辐照菌株FⅡ12 1、FⅡ116和FⅡ14 0 的产孢量分别比I2 62 提高 5 4 4%、5 1 5 %和 41 7%。化学和物理技术相结合处理稗草生防潜力菌 ,获得的突变菌株产孢量比原始菌株提高 1倍以上。但高产孢突变菌株对稗草的致病性、防效与原始菌株相当。     

同步辐射软X射线Nk对产L-乳酸米根霉的诱变效应

采用同步辐射软X射线Nk对米根霉AS 3.3461菌株进行辐射诱变,研究其对米根霉致死、菌落形态、种子培养以及发酵培养等特性方面的影响。结果表明,致死率曲线呈现为典型的马鞍型曲线,辐射剂量为0.72 kGy时菌株致死率最低;软X射线Nk辐照对米根霉菌落形态有一定影响;种子培养特性和发酵培养特性的诱变前后对比表明,种子延滞期缩短了3h,突变株N-15的L-乳酸产量提高了25.6%,LDH活性提高了95.8%,ADH的活性降低了77.7%。     

屎肠球菌M-2所产细菌素的分离纯化与特性研究

本文以前期从内蒙古传统干酪中分离到的一株产细菌素的屎肠球菌M-2为试材,对其所产细菌素进行提取纯化和理化特性研究。经80%硫酸铵盐析及SP Sepharose Fast Flow阳离子交换树脂层析得到纯化的细菌素,其比活力可达411.204AU/mg;Tricine SDS-PAGE电泳结果显示其分子量约为3400Da;特性研究发现该细菌素有很好耐热、耐酸碱、抗表面活性剂及蛋白酶敏感特性,且抑菌谱较广,不仅对李斯特氏菌、金黄色葡萄球菌、芽孢杆菌等革兰氏阳性菌有较强的抑制作用,还对大肠杆菌、假单胞菌等阴性菌表现出抑菌活性,有作为天然食品防腐剂的良好应用前景。     

Interaction of different humic acid fractions from clayey soddy-podzolic soils with calcium

Interactions of the first and second humic acid (HA) fractions isolated from clayey soddy-podzolic soils of the Novgorod Experimental Agricultural Station with calcium were studied. It was found that the formation of calcium humates with different HA fractions followed common regularities, but significant differences in the parameters characterizing the course of the reaction and the properties of the resulting products (including the capacity of precipitates to be peptized in water and to prevent calcium from leaching) were observed between the HA-1 and HA-2 fractions. For many of the parameters studied, the difference between the HA-1 and HA-2 fractions was comparable to that between black and brown HAs. The persistence of positive changes related to liming in the soil largely depended on the functional properties of the HAs and their capacity to actively interact with calcium and prevent it from leaching.     

Composition, enantiomeric distribution, and antibacterial activity of the essential oil of Achillea ligustica All. from Corsica

The essential oil of Achillea ligustica from Corsica was investigated by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). A total of 82 compounds representing 94.0% of the oil were tentatively identified. The main constituents were the camphane derivatives, representing >30% (camphor, 21.3%; borneol, 6.2%; bornyl acetate, 3.5%) of the whole oil, and santolina alcohol (19.3%). The enantiomeric distribution of 8 chiral constituents was determined by GC-MS using two enantioselective stationary phases (DIME-beta-CD and Lipodex-E). Racemic santolina alcohol, required for optimization of the enantioselective GC conditions, was prepared by an original two-step synthesis from 2,5-dimethylhexa-2,4-diene. The whole essential oil was tested for its antibacterial activity against a wide range of bacteria using a paper disk method. The results show a promising activity against Streptomyces species.     

Larvicidal activity of lignans identified in Phryma leptostachya Var. asiatica roots against three mosquito species

The insecticidal activity of phytochemicals isolated from the roots of Phryma leptostachya var. asiatica against third instar larvae of Culex pipiens pallens, Aedes aegypti, and Ocheratatos togoi was examined. The two constituents of P. leptostachya var. asiatica roots were identified as the leptostachyol acetate (I) and 8'-acetoxy-2,2',6-trimethoxy-3,4,4',5'-dimethylenedioxyphenyl-7,7'-dioxabicyclo[3.3.0]octane (II) by spectroscopic analysis. Compound I was lethal to C. pipiens pallens, A. aegypti, and O. togoi at 10 ppm. Compound II showed weak or no insecticidal activity against three mosquito species at 10 ppm. The LC(50) values of I against C. pipiens pallens, A. aegypti, and O. togoi were 0.41, 2.1, and 2.3 ppm, respectively. Naturally occurring P. leptostachya var. asiatica root-derived compounds merit further study as potential mosquito larval control agents or lead compounds.     

Selective digestion of the peptide and polysaccharide components of synthetic humic acids by the humivorous larva of Pachnoda ephippiata (Coleoptera: Scarabaeidae)

In order to identify the potential nutrient and energy sources of humivorous beetle larvae, we carried out feeding trials with soil supplemented with specifically ¹⁴C-labeled model humic acids synthesized by peroxidase-initiated radical polymerization, using the cetoniid beetle Pachnoda ephippiata (Coleoptera: Scarabaeidae) as a model organism. Ingestion of soil by the larvae significantly increased the mineralization of humic acids labeled in their peptide (HA-*peptide) or polysaccharide components (HA-*peptidoglycan and HA-*chitin), whereas the mineralization of humic acids labeled in the aromatic components (HA-*catechol) did not increase significantly. Mineralization was accompanied by a reduction of residual radiolabel in the acid-soluble fraction and an increase in the humic acid and humin fractions of the fecal pellets. During the gut passage, the residual label in peptide or polysaccharide components was transformed into acid-soluble products, especially in the alkaline midgut. High-performance gel-permeation chromatography demonstrated that the changes in solubility were accompanied by large changes in the molecular weight of the residual material. The amount of radiolabel derived from the peptide and polysaccharide components recovered from the larval body and hemolymph was significantly higher than that derived from the aromatic component, which supports the hypothesis that humivorous beetle larvae selectively digest the peptide and polysaccharide components of humic substances, whereas the aromatic components of humic substances are not an important source of nutrients and energy. This is also the first experimental evidence that also chitin and peptidoglycan, the major structural polymers in fungal and bacterial biomass, can be protected from microbial degradation in soil by a copolymerization with phenols and might contribute substantially to the refractory nitrogen pool in soil organic matter.     

Accumulation of trehalose in the thermophilic fungus Chaetomium thermophilum var. coprophilum in response to heat or salt stress

The disaccharide trehalose, known to be an effective protectant against various kinds of stress, was observed to accumulate in the cytosol of Chaetomium thermophilum var. coprophilum during heat stress. Trehalose was apparently neither involved in the defence of C. thermophilum var. coprophilum against high concentrations of sodium chloride nor directly linked to thermophily.In C. thermophilum var. coprophilum three different trehalose hydrolyzing activities were eluted from a mono Q anion exchange column by sodium chloride concentrations of 0.10, 0.15 and 0.24 M, respectively.     

Changes in the content and composition of humus in the sandy loamy soddy-podzolic soil in a long-term liming experiment

The effect of liming on organic matter in sandy loamy soddy-podzolic soil was studied. The study was performed on samples taken from the 50-year-long experiment established by Prof. Kornilov in 1957. It was shown that liming had almost no effect on the total humus content in the soil. The humus composition was studied using two fractionation methods of the humus substances by the Ponomareva-Plotnikova procedure. The regrouping of the humus fractions occurred due to the changes in the mobility of soil mineral components, which involved a regular increase in the content of the Ca-bound fraction of humic acids (HA-2) at the expense of the HA-1 fraction bound to the mobile forms of R₂O₃ reliable at the lime rates equivalent to the total acidity and higher. The levels of the stabilization of the different HA fractions were considered, as well as the stability of the changes in the humus composition during 50 years.     

Chemical composition and antifungal activity of Arnica longifolia, Aster hesperius, and Chrysothamnus nauseosus essential oils

Essential oils from three different Asteraceae obtained by hydrodistillation of aerial parts were analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS). Main compounds obtained from each taxon were found as follows: Arnica longifolia carvacrol 37.3%, alpha-bisabolol 8.2%; Aster hesperius hexadecanoic acid 29.6%, carvacrol 15.2%; and Chrysothamnus nauseosus var. nauseosus beta-phellandrene 22.8% and beta-pinene 19.8%. Essential oils were also evaluated for their antimalarial and antimicrobial activity against human pathogens, and antifungal activities against plant pathogens. No antimalarial and antimicrobial activities against human pathogens were observed. Direct bioautography demonstrated antifungal activity of the essential oils obtained from three Asteraceae taxa and two pure compounds, carvacrol and beta-bisabolol, to the plant pathogens Colletotrichum acutatum, C. fragariae and C. gloeosporioides. Subsequent evaluation of antifungal compounds using a 96-well micro-dilution broth assay indicated that alpha-bisabolol showed weak growth inhibition of the plant pathogen Botrytis cinerea after 72 h.     

Influence of Sulfur Fertilization on Infection of Potato Tubers with Rhizoctonia solani and Streptomyces scabies

ABSTRACT

Under conditions of sulfur (S)-deficient soil, applied S fertilization had a significant repressive effect on fungal infections such as that of oilseed rape and grapes with light leaf spot (Pyrenopeziza brassicae) and powdery mildew (Uncinula necator), respectively. For potatoes (Solanum tuberosum L.) it has been shown in earlier literature that elemental sulfur fertilization increased yield of potato tubers and improved tuber quality and resistance against Streptomyces scabies; the bactericidal effect was attributed to a reduced soil pH. So far, however, no information is available about the influence of S supply on bacterial and fungal diseases in potatoes. It was the aim of the present investigation to quantify the influence of S form and dose on infections of potato tubers with Rhizoctonia solani and Streptomyces scabies as a contribution to plant nutrition strategies for healthier plants. Field experiments with potatoes were conducted in 2001 and 2002 in Poland in a split-plot design with different sulfur forms (elemental S and K₂SO₄) and rates (0, 25, and 50 kg ha^{? 1} S). The application of sulfur significantly increased tuber yield in both years of experimentation. Generally, with increasing sulfur dose a significant decrease of the infection rate with Rhizoctonia solani was found for elemental S as well as for K₂SO₄ applications. Infection rate and severity of the disease was improved only by elemental S application due to a reduction in soil pH in the case of Streptomyces scabies. Thus it can be concluded that the health-promoting effect of sulfur fertilization was related mainly to the S status of the plant in case of infections with Rhizoctonia solani, while for Streptomyces scabies no mechanisms of S-induced resistance were found. The identification of differences in the S metabolism of Rhizoctonia solani and Streptomyces scabies may therefore elucidate S-induced resistance mechanisms in plants.     

Hydrolysis of the amyloid prion protein and nonpathogenic meat and bone meal by anaerobic thermophilic prokaryotes and streptomyces subspecies

Transmissible spongiform encephalopathies are caused by accumulation of highly resistant misfolded amyloid prion protein PrPres and can be initiated by penetration of such pathogen molecules from infected tissue to intact organism. Decontamination of animal meal containing amyloid prion protein is proposed thanks to the use of proteolytic enzymes secreted by thermophilic bacteria Thermoanaerobacter, Thermosipho, and Thermococcus subsp. and mesophilic soil bacteria Streptomyces subsp. Keratins alpha and beta, which resemble amyloid structures, were used as the substrates for the screening for microorganisms able to grow on keratins and producing efficient proteases specific for hydrolysis of beta-sheeted proteic structures, hence amyloids. Secretion of keratin-degrading proteases was evidenced by a zymogram method. Enzymes from thermophilic strains VC13, VC15, and S290 and Streptomyces subsp. S6 were strongly active against amyloid recombinant ovine prion protein and animal meal proteins. The studied proteases displayed broad primary specificities hydrolyzing low molecular mass peptide model substrates. Strong amyloidolytic activity of detected proteases was confirmed by experiments of hydrolysis of PrPres in SAFs produced from brain homogenates of mice infected with the 6PB1 BSE strain. The proteases from Thermoanaerobacter subsp. S290 and Streptomyces subsp. S6 are the best candidates for neutralization/elimination of amyloids in meat and bone meal and other protein-containing substances and materials.     

Contribution of zooplankton to the total cadmium pool in Canadian shield lakes varying in acidity

Crustacean zooplankton >250 m in size contributed 0.002 to 11% (median of 1.3%) of the total Cd in the epilimnia of 39 Canadian Shield lakes that ranged in pH from 4.7 to 8.3. The contribution of zooplankton to the total Cd pool was consistently low (1%) only in clear water lakes with pH < 5.0.=" in=" three=" intensively=" studied=" lakes,=" the=" contribution=" of=" zooplankton=" to=" total=" aqueous=" cd=" varied=" with=" time=" and=" depth,=" the=" maximum=" contribution=" (4=" to=" 6%)=" occurring=" in=" the=" metalimnion=" in=" mid-summer.=" changes=" with=" depth=" and=" time=" were=" principally=" a=" product=" of=" seasonal=" changes=" in=" zooplankton=" biomass=" and=" seasonal=" succession=" of=" species=" with=" inherently=" different=" tendencies=" to=" accumulate=" cd.=" implications=" for=" the=" study=" of=" cd=" cycling=" in=" lakes=" are=">