Antifungal activity in vitro of Baccharis glutinosa and Ambrosia confertiflora extracts on Aspergillus flavus, Aspergillus parasiticus and Fusarium verticillioides

The aims of this study were to evaluate the antifungal properties of Baccharis glutinosa and Ambrosia confertiflora extracts against Aspergillus flavus, A. parasiticus and Fusarium verticillioides, and to isolate the group of compounds that are responsible for the antifungal activity. Samples of aerial parts from each plant were extracted with 70% methanol and sequentially partitioned with hexane, ethyl acetate, and n-butanol. The partitioned fractions were evaluated in their capacity to inhibit the radial growth of the three species of fungi. The active fraction was used for an assay-guided chromatography of antifungal extracts. The results showed that the extract from B. glutinosa partitioned in ethyl acetate (Bea) showed the highest antifungal activity against the three fungi. Bea completely inhibited the growth of F. verticillioides at 0.8 mg/ml, whereas the radial growth of A. flavus and A. parasiticus was inhibited 70% at 1.5 mg/ml. The purified antifungal fraction from Bea showed 72, 54, and 52% of antifungal activity, respectively.     

(Na + K)-ATPase activity of crude homogenates of rat skeletal muscle as estimated from their K-dependent 3-O-methylfluorescein phosphatase activity

A highly sensitive fluorimetric assay using 3-O-methylfluorescein phosphate as substrate was used in the determination of K⁺-dependent phosphatase activity in preparations of rat skeletal muscle. The gastrocnemius muscle was chosen because of mixed fibre composition. Crude, detergent treated homogenate was used so as to avoid loss of activity during purification. K⁺-dependent phosphatase activities in the range 0.19–0.37 μmol · (g wet weight)⁻¹ · min⁻¹ were obtained, the value decreasing with age and K⁺-deficiency. Complete inhibition of the K⁺-dependent phosphatase was obtained with 10⁻³ M ouabain. Using a KSCN-extracted muscle enzyme the intimate relation between K⁺-dependent phosphatase activity and (Na⁺ + K⁺)-activated ATP hydrolysis could be demonstrated. A molecular activity of 620 min⁻¹ was estimated from simultaneous determination of K⁺-dependent phosphatase activity and [³H]ouabain binding capacity using the partially purified enzyme preparation. The corresponding enzyme concentration in the crude homogenates was calculated and corresponded well with the number of [³H]ouabain binding sites measured in intact muscles or biopsies hereof.     

药用植物青蒿不同种类的内生菌抑菌活性分析

为了研究青蒿不同种类的内生菌抑制细菌和抑制真菌的活性,该研究采用组织块法和研磨法从青蒿的根、茎、叶中分离内生细菌、放线菌和真菌,以大肠埃希菌(Escherichia coli)(CICC 23657)、枯草芽孢杆菌(Bacillus subtilis)(CICC 10275)、金黄色葡萄球菌(Staphylococcus aureus)(CICC 10384)、黑曲霉(Aspergillus niger)(CICC 2487)、酿酒酵母(Saccharomyces cerevisiae)(CICC 33032)为指示菌,采用琼脂块法和双层平板法检测内生菌的抑菌活性。结果表明:(1)从青蒿植株中共分离到76株内生菌,其中内生细菌19株、内生放线菌34株、内生真菌23株。从分离部位来看,56株来自于茎段、17株来自于根段、3株来自叶片。(2)内生细菌中抑菌活性菌株占总菌株的比例最高,为95%,内生放线菌和内生真菌中抑菌活性菌株的比例分别为41%、35%。(3)内生细菌的抗菌谱较广;虽然内生放线菌的抗菌谱较窄,但其中高抗菌株较多,尤其对酿酒酵母的抑菌效果好。综上结果显示,药用植物青蒿中存在着丰富的有抑菌活性的内生菌,且不同种类的内生菌抑菌活性不同。     

A previously unrecognized glutamine synthetase expressed in Klebsiella pneumoniae from the glnT locus of Rhizobium leguminosarum

Summary Using glnT DNA of Rhizobium meliloti as a hybridization probe we identified a R. leguminosarum biovar phaseoli (R. l. phaseoli) locus (glnT) expressing a glutamine synthetase activity in Klebsiella pneumoniae. A 2.2 kb DNA fragment from R. l. phaseoli was cloned to give plasmid pMW5a, which shows interspecific complementation of a K. pneumoniae glnA mutant. The cloned sequence did not show cross-hybridization to glnA or glnII, the genes coding for two glutamine synthetase isozymes of Rhizobium spp. While in previous reports on glnT of R. meliloti and Agrobacterium tumefaciens no glutamine synthetase activity was detected, we do find activity with the glnT locus of R. l. phaseoli. The glutamine synthetase (GSIII) activity expressed in a K. pneumoniae glnA strain from pMW5a shows a ratio of biosynthetic to transferase activity 10³-fold higher than that observed for GSI or GSII. GSIII is similar in molecular weight and heat stability to GSI.     

富硒条件下蜜环菌菌株硒耐受性及胞外酶生物活性的研究

[目的]通过对蜜环菌(Armillaria mellea)的富硒驯化,研究各菌株硒耐受性、有机硒含量及生物活性的变化规律,从而获得生物活性更强的蜜环菌,并对富硒蜜环菌的生物学特征进行初步研究.[方法]以Na2SeO3为无机硒试剂对蜜环菌进行富硒驯化;采用氢化物原子荧光光谱法测定蜜环菌的硒含量,热水浴法测定蜜环菌的无机硒...     

Phytotoxic effects of Lantana camara, Eucalyptus camaldulensis and Eriocephalus africanus essential oils in weeds of Mediterranean summer crops

The essential oil composition of Lantana camara, Eucalyptus camaldulensis and Eriocephalus africanus was analyzed by means of GC and GC–MS and bioassayed in order to determine their activity against Amaranthus hybridus and Portulaca oleracea. E. camaldulensis essential oil, with spathulenol as the main compound, was the most effective, completely inhibiting germination and seedling growth on both weeds. The essential oil of E. africanus, rich in artemisia ketone, showed activity similar to that of E. camaldulensis on A. hybridus, but it was not so effective against P. oleracea, and L. camara essential oil, with high percentages in sesquiterpene hydrocarbons, also showed higher phytotoxic activity against A. hybridus, inhibiting its germination and seedling length; however, it showed no effect against P. oleracea germination, whereas was effective in significantly reducing its seedling growth at all concentrations assayed. The results suggest the possible use of these essential oils as natural herbicides.     

拮抗北细辛菌核病木霉菌的分离、鉴定及生防效果

【背景】菌核病是北细辛根部主要病害之一,木霉菌作为目前应用最广泛的生物防治真菌,利用木霉菌防治北细辛菌核病是目前研究的热点。【目的】通过稀释分离法对健康北细辛植株根际土壤进行菌株分离,以期筛选出有效拮抗北细辛菌核病的生防木霉菌。【方法】以北细辛菌核病菌为靶标菌,采用平板对峙培养、挥发性与非挥发性物质抑菌的方法对分离得到的木霉菌进行筛选,采用生长速率法对筛选出的木霉菌的发酵液进行抑菌效果测定,并采用硫代巴比妥酸法测定筛选出的木霉对北细辛菌核病菌的丙二醛(Malondialdehyde,MDA)含量、紫外吸收法测定过氧化氢酶(Catalase,CAT)活性、氮蓝四唑法测定超氧化物歧化酶(Superoxide Dismutase,SOD)活性、愈创木酚法测定过氧化物酶(Peroxidase,POD)活性的影响。【结果】从土壤中分离出木霉菌共14株,通过形态学和ITS-RPB2双基因联合构建系统发育树,鉴定其为哈茨木霉(Trichoderma harzianum)、钩状木霉(Trichoderma hamatum)、拟康氏木霉(Trichoderma koningiopsis)、深绿木霉(Tr...     

Regulation of expression of nif and hut operons in Klebsiella pneumoniae by glnA linked genes of Escherichia coli

Summary Recombinant DNA plasmids containing inserts from the glnA region of Escherichia coli were used to study the expression of gln, hut, and nif operons in a regulation defective mutant (Gln^–Hut^–Nif^–) of Klebsiella pneumoniae, KP5060. Genes adjacent to the C-terminal end of glnA on the E. coli chromosome were able to derepress hut and nif operons in K. pneumoniae in the absence of glnA product. However, complete derepression of nif operons required inclusion of the segment adjacent to the N-terminal end of the glnA region of the E. coli chromosome along with the C-terminal end segment. In the absence of functional glnA, such a fully derepressed strain expressed nif and hut constitutively indicating a role for the catalytic activity of glutamine synthetase in repression of the genes under nitrogen control.     

尖吻蝮蛇毒碱性磷脂酶A2的表达及其生化特征

将尖吻蝮蛇毒碱性磷脂酶A₂（A.aBPLA₂）基因克隆至温敏表达载体pBLMVL2,在大肠杆菌RR1中成功诱导表达.表达产物A.aBPLA₂约占细菌蛋白质总量的20％,并以包涵体的形式存在.纯化包涵体后,将产物变性、复性,然后用FPLC Superose^TM12纯化,产物经过SDS-聚丙烯酰胺凝胶电泳检测只有单一条带.对纯化后的表达A.aBPLA₂进行了酶活性、抑制血小板聚集活性和溶血活性的测定.结果显示,表达A.aBPLA₂的酶活性与变性后复性江浙蝮蛇酸性磷脂酶A₂酶活性相近,具有类似变性后复性江浙蝮蛇碱性磷脂酶A₂的溶血活性,没有抑制血小板聚集活性.最后对磷脂酶A₂的结构与这些活性的关系进行了讨论.     

Investigation of the cyt gene in Bacillus thuringiensis and the biological activities of Bt isolates from the soil of China

The presence of cyt genes was investigated in 80 type strains of Bacillus thuringiensis and 143 isolates obtained from soil samples of China by PCR amplification using two pairs of primers for the cyt1 and cyt2 genes. Three type strains of serotypes H11ac, H14 and H36, eight isolates belonging to H3, H14, H18 and H21, and one isolate of unknown serotype harbored cyt genes. We also tested the cytolytic activity for mammal cells, the hemolytic activity for sheep erythrocytes and insecticidal activity against mosquitoes of five isolates that contained cyt genes but did not belong to B. thuringiensis serovar israelensis. The protein profiles of the five isolates were different from those of the type strains of B. thuringiensis serovar israelensis, and among the five isolates, only Y-5 showed mosquitocidal activity against larvae of Culex quinquefasciatus. All five of the isolates exhibited hemolytic activity, but only three could cause the cell death of A549 cells. The cytopathological changes induced by NX-4 in some A549 cells were characterized with cell-ballooning.     

Hyper-recombination in uvrD mutants of Escherichia coli K-12

Summary A mutant strain of E. coli which was isolated initially because of its strong hyper-recombination phenotype was shown to carry a lesion in uvrD. The presence of this mutation, designated uvrD210, increased the frequency of recombination between chromosomal duplications in F-prime repliconant cells and reduced linkage between closely linked markers in crosses with Hfr donors. A comparable hyper-rec phenotype was demonstrated in strains carrying other alleles of uvrD previously referred to as mutU4, uvr502 and recL152. The recombination activity of a uvrD210 strain was abolished by mutation of recA but the mutator activity associated with this allele proved to be independent of recA. It is suggested that uvrD mutations reduce the fidelity of DNA replication and that the accumulation of lesions in the newly synthesized strand provides additional sites for initiating recombination.     

黄芩苷对嗜水气单胞菌生物膜形成的影响及体内外的抑菌作用

[目的]探讨中药单体黄芩苷对嗜水气单胞菌在体内外生长及生物膜形成的影响.[方法]体外实验中,利用牛津杯法检测抑菌圈直径,结晶紫法检测生物膜的形成,通过泳动实验检测黄芩苷对嗜水气单胞菌运动性的影响,紫外吸收法检测细胞膜完整性,用透射电镜技术观察黄芩苷对细菌形态的影响.体内实验利用草鱼为对象检测黄芩苷对嗜水气单胞菌增殖的影...     

Utilization of O2 in the metabolic optimization of C4 photosynthesis

The combined effects of O₂ on net rates of photosynthesis, photosystem II activity, steady‐state pool size of key metabolites of photosynthetic metabolism in the C₄ pathway, C₃ pathway and C₂ photorespiratory cycle and on growth were evaluated in the C₄ species Amaranthus edulis and the C₃ species Flaveria pringlei. Increasing O₂ reduced net CO₂ assimilation in F. pringlei due to an increased flux of C through the photorespiratory pathway. However, in A. edulis increasing O₂ up to 5–10% stimulated photosynthesis. Analysis of the pool size of key metabolites in A. edulis suggests that while there is some O₂ dependent photorespiration, O₂ is required for maximizing C₄ cycle activity to concentrate CO₂ in bundle sheath cells. Therefore, the response of net photosynthesis to O₂ in C₄ plants may result from the balance of these two opposing effects. Under 21 versus 5% O₂, growth of A. edulis was stimulated about 30% whereas that of F. pringlei was inhibited about 40%.     

Cloning and expression inEscherichia coli of the sucrase gene fromBacillus subtilis

Summary A recombinant cosmid carrying the sucrase gene (sacA) was obtained from a colony bank ofE. coli harboring recombinant cosmids representative of theB. subtilis genome. It was shown that thesacA gene is located in a 2 kbEcoRI fragment and that the cloned sequence is homologous to the corresponding chromosomal DNA fragment. A fragment of 2 kb containing the gene was subcloned in both orientations in the bifunctional vector pHV33 and expression was further looked for inB. subtilis andE. coli. Complementation of asacA mutation was observed in Rec⁺ and Rec^- strains ofB. subtilis. Expression of sucrase was also demonstrated inE.coli, which is normally devoid of this activity, by SDS-polyacrylamide gel electrophoresis, specific immunoprecipitation and assay of the enzyme in crude extracts. The specific activity of the enzyme depended on the orientation of the inserted fragment. The saccharolytic activity was found to be cryptic inE. coli since the presence of the recombinant plasmids did not allow the transport of [U¹⁴C] sucrose and the growth of the cells.It was shown also that the recombinant cosmid contained part of the neighboring locus (sacP) which corresponds to a component of the PEP-dependent phosphotransferase system of sucrose transport ofB. subtilis.     

Formation of NADPH-nitrate reductase activity in vitro from Aspergillus nidulans niaD and cnx mutants

Summary Mutants of A. nidulans at several loci lack detectable NADPH-nitrate reductase activity. These loci include niaD, the structural gene for the nitrate reductase polypeptide, and five other loci termed cnxABC, E, F, G and H which are presumed to be involved in the formation of a molybdenum-containing component (MCC) necessary for nitrate reductase activity. When frozen mycelia from A. nidulans deletion mutant niaD26 were homogenized in a Ten Broeck homogenizer together with frozen mycelia from either enzA6, cnxE29, cnxF12, enxG4 or cnxH3 strains grown on urea+nitrate as the nitrogen source, nitrate reductase activity was detectable in the extract. Similar results were obtained by co-homogenizing niaD mycelia with Neurospora crassa nit-1 mycelia induced on nitrate. Thus, all A. nidulans cnx mutants are similar to the N. crassa nit-1 strain in their capacity to yield NADPH-nitrate reductase in the presence of the presumed MCC. As judged by the amounts of nitrate reductase formed, niaD26 mycelia grown on urea±nitrate contained much more available MCC than ammonium-grown mycelia. No NADPH-nitrate reductase activity was found in extracts prepared by co-homogenizing mycelia from all five A. nidulans cnx strains. Wild-type A. nidulans NADPH-nitrate reductase acid dissociated by adjustment to pH 2.0–2.5 and re-adjusted to pH 7 could itself re-assemble to form active nitrate reductase and thus was not a sueful source of MCC for these experiments. These results are consistent with the conclusion that the active nitrate reductase complex is composed of polypeptide components which are the niaD gene product, plus the MCC which is formed through the combined action of the cnx gene products. Further, the production of MCC may be regulated in response to the nitrogen nutrition available to the organism.     

连翘提取物对嗜水气单胞菌群体感应系统的影响

【背景】传统抑菌剂的大量使用导致细菌产生多重耐药性与抗性,而基于细菌群体感应靶点调控的新型抑菌剂可缓解细菌耐药性与抗性,是未来抑菌剂的发展方向之一。【目的】研究连翘(Forsythiasuspensa)提取物对嗜水气单胞菌(Aeromonashydrophila)群体感应系统的影响及可能的作用机制,为新型抑菌剂的开发提供理论依据。【方法】以紫色杆菌(Chromobacterium violaceum)CV026为报告菌株,以嗜水气单胞菌为供试菌株,采用倍比稀释法测定连翘提取物对2种菌的最小抑菌浓度(minimal inhibitory concentration,MIC),通过微量法测定提取物对嗜水气单胞菌生长、群集运动及蛋白酶活性的影响,利用高效液相色谱串联质谱法分析提取物中的主要成分,采用分子对接模拟探究提取物对嗜水气单胞菌群体感应系统的作用机制。【结果】连翘提取物对紫色杆菌CV026和嗜水气单胞菌的MIC均为16.00mg/mL。在亚抑菌浓度下,连翘提取物处理显著抑制了CV026紫色菌素的产生,最大抑制率高达56.30%。经8.00mg/mL连翘提取物处理后,嗜水气单胞菌的群集运...     

小花老鼠簕可培养细菌多样性及其生物学活性研究

小花老鼠簕(Acanthus ebracteatus)是一种生长在红树生态系统的珍稀真红树植物,具有较高的药用价值。为研究小花老鼠簕内生及根际可培养细菌多样性,挖掘其潜在新物种及具有特殊生物学活性的菌株,该文利用7种不同培养基,通过传统稀释涂布法对小花老鼠簕各植物组织及根际土壤可培养细菌进行分离,基于16S rRNA基因序列解析其内生及根际细菌群落结构和多样性特征,应用植物病原菌平板对峙实验和平铺捕食活性测试分析其可培养细菌的抗菌活性。结果表明：(1)基于16S rRNA基因序列分析,发现从小花老鼠簕的根、茎、叶、花及根际土壤中分离得到144株可培养细菌,这些细菌隶属于18目26科37属66种,芽孢杆菌属(Bacillus)和链霉菌属(Streptomyces)为优势菌属,分别占细菌种数的15.1%和13.6%;(2)拮抗多种植物病原菌试验结果显示,获得29株具有拮抗植物病原菌活性的细菌,10株具有广谱抑菌活性,其中链霉菌属菌株拮抗作用最强且菌株Y129为潜在新物种。(3)捕食活性测试结果显示,有5株细菌对金黄色葡萄球菌(Staphylococcus aureus)、耐甲氧西林金黄色葡...