Isolation and characterization of a glucocerebroside (monoglucosylceramide) from Sporothrix schenckii

A glucocerebroside from yeast forms of the pathogenic fungus Sporothrix schenckii has been isolated and its components characterized by thin-layer and gas-liquid chromatography and by mass spectrometry. The purified molecule contained glucose, sphingosine and α-hydroxy stearic acid (1:1:1) and it seemed homogenous since no other fatty acid was detected.     

BALB/c mice produce blister-causing antibodies upon immunization with a recombinant human desmoglein 3

Pemphigus vulgaris (PV) is an Ab-mediated autoimmune blistering disease of mucotaneous surfaces. Over 95% of the patients with PV express DR4 or DRw6, and the disease is characterized by the presence of autoantibodies directed against desmoglein 3 (Dsg 3), a protein expressed on keratinocytes. An appropriate animal model is required to understand immunoregulation and to address the role of immunogenetic components in the production of pathogenic Abs that are characteristic of PV. Therefore, we turned to the development of a mouse model. Four strains of female mice (BALB/c, DBA/1, SJL/J, and HRS/J) were screened for their ability to produce pathogenic anti-Dsg 3 Abs. We demonstrated that only BALB/c mice immunized with a full-length Dsg 3 can produce pathogenic Abs capable of causing acantholysis of human foreskin in culture and blistering in neonatal mice. This observation suggested that either H-2d or the BALB background contains the immunogenetic makeup necessary for the production of pathogenic anti-Dsg 3 Abs. No correlation was noted between a given isotype and the pathogenic potential of autoantibodies from different strains of mice. Similarly, the pattern of reactivity of Abs with a panel of 46 synthetic peptides that span the entire Dsg 3 failed to reveal any association between binding specificity and the pathogenic potential, and suggested that pathogenic Abs might recognize conformational epitopes. Moreover, our studies showed that the epitopes recognized by pathogenic Abs are contained within the extracellular Dsg 3.     

Increased pathogenicity in a pseudorecombinant bipartite geminivirus correlates with intermolecular recombination.

Most whitefly-transmitted geminiviruses possess bipartite DNA genomes, and this feature may facilitate viral evolution through pseudorecombination and/or recombination. To test this hypothesis, the DNA-A and DNA-B components of the geminiviruses bean dwarf mosaic virus (BDMV) and tomato mottle virus (ToMoV) were exchanged, and the resultant pseudorecombinants were serially passaged through plants. Both pseudorecombinants were infectious in Nicotiana benthamiana but induced attenuated symptoms and had reduced DNA-B levels. Serial passage experiments revealed that the BDMV DNA-A plus ToMoV DNA-B pseudorecombinant could not be maintained beyond three passages. In contrast, the ToMoV DNA-A plus BDMV DNA-B pseudorecombinant was maintained during serial passage through N. benthamiana and Phaseolus vulgaris and, after three to five passages, became highly pathogenic. Furthermore, the increased pathogenicity of this pseudorecombinant was consistently associated with an increased level of DNA-B, which eventuated in equivalent levels of both components. Sequence analysis of the DNA-B component of the more pathogenic pseudorecombinant revealed that intermolecular recombination had taken place in which most of the BDMV DNA-B common region was replaced with the ToMoV DNA-A common region. This recombinant DNA-B component, which contained the ToMoV origin of replication, was the predominant DNA-B component associated with the more pathogenic pseudorecombinant. These results provide the first demonstration of recombination between distinct bipartite geminiviruses and establish that the bipartite genome can facilitate viral evolution through pseudorecombination and intermolecular recombination.     

Functional genomics of pathogenic bacteria

Microbial diseases remain the commonest cause of global mortality and morbidity. Automated-DNA sequencing has revolutionized the investigation of pathogenic microbes by making the immense fund of information contained in their genomes available at reasonable cost. The challenge is how this information can be used to increase current understanding of the biology of commensal and virulence behaviour of pathogens with particular emphasis on in vivo function and novel approaches to prevention. One example of the application of whole-genome-sequence information is afforded by investigations of the pathogenic role of Haemophilus influenzae lipopolysaccharide and its candidacy as a vaccine.     

Effect of the fever reaction on the kallikrein-kinin system of the lymph and blood

The dynamics of kallikrein-kinin system components in the lymph of thoracic duct and blood following fever reaction of various duration has been studied in the experiment on rabbits. The experiments have shown that in prolonged fever reaction there are qualitative disorders in kinin system components ratio indicative of break in the system of regulatory links, its exhaustion and transformation of the physiological reactions into the pathogenic ones. One may assume that changes in kallikrein-kinin system activity in body fluid are the links in the complex of pathogenic disorders in the organ and system functional activity during prolonged fever reaction.     

真菌侵染引发的茶树内源糖苷酶基因差异表达

通过探讨顺-3-己烯醇、芳樟醇氧化物、芳樟醇、水杨酸甲酯、香叶醇、苯甲醇和苯乙醇7种茶叶游离态香气组分和糖苷类香气前体对茶炭疽病菌、茶云纹叶枯病菌、茶轮斑病菌和茶赤叶斑病菌4种致病菌的抑制作用,以及真菌侵染引发的茶树（Camellia sinensis）内源β-樱草糖苷酶、β-木糖苷酶、β-葡萄糖苷酶I、β-葡萄糖苷酶II、β-葡萄糖基转移酶基因的表达差异,结果表明：7种游离态香气组分和糖苷类香气前体对4种致病菌均有明显的抑制作用,其中香叶醇的抑制作用最强,在浓度为0.1mg.mL-1时即对茶炭疽病菌的抑制率达到100%。实时定量PCR结果显示：真菌侵染可不同程度诱导茶树内源糖苷酶和β-葡萄糖基转移酶基因的表达上调,且上调多发生于染病初期。     

Substrate recognition by the Yersinia type III protein secretion machinery

Type III secretion is the designation given to those protein secretion pathways, primarily in pathogenic Gram-negative bacteria, whose secretion machinery components share an amino acid sequence homology to components of the flagellar basal body. In Yersinia spp., these secretion machineries inject virulence proteins called Yops into the cytosol of target macrophages in an effort to evade phagocytic killing. To date, a clear mechanism by which Yops are recognized by the type III secretion machinery has not been elucidated. Unlike most, if not all, previously characterized protein sorting pathways, the information that identifies Yops as substrates for secretion seems not to be wholly encoded within the Yop peptide sequence. In fact, it appears that at least some of this information is contained within yop mRNAs. This review summarizes recent observations that have been made in this unusual field and proposes models by which proteins may be initiated into this pathway.     

蛋白磷酸化修饰在植物-病原微生物互作中的作用研究进展

蛋白磷酸化修饰是植物细胞信号调控的普遍机制。植物-病原微生物互作过程中, 关键调控蛋白的磷酸化状态影响免疫信号的激活。多种病原微生物通过干扰宿主蛋白的磷酸化状态攻击免疫系统, 以提高致病性。该文对植物免疫调控过程中关键元件的磷酸化修饰及其在免疫信号中的调控作用进行了综述。研究植物-病原菌互作过程中关键蛋白的磷酸化修饰, 有助于深入探讨植物-病原微生物互作的分子机理。该文将为寻找广谱抗病的新途径提供理论依据。     

Role of a membrane glycoprotein in Friend virus erythroleukemia: nucleotide sequences of nonleukemogenic mutant and spontaneous revertant viruses.

We previously isolated spontaneous env gene mutants of Friend spleen focus-forming virus that are nonleukemogenic in adult mice but form leukemogenic revertants in newborns; we found that the revertants contain secondary env mutations. To identify sites in the encoded membrane glycoprotein that are important for its pathogenic function, we molecularly cloned and partially sequenced the env genes of two mutant viruses (clone 63 and clone 4) and one revertant (clone 4REV). Clone 63 contained three noncontiguous point mutations that caused nonconservative amino acid substitutions of Gly-119----Arg-119, Cys-180----Tyr-180, and Gly-203----Arg-203 in the xenotropic-related domain of the env glycoprotein. These substitutions were presumably responsible for the altered electrophoretic and pathogenic properties of the mutant glycoprotein. The presence of these and several other G-A nucleotide substitutions at different sites in one spontaneous mutant provided striking evidence that error-rich proviruses can form during retroviral replication. Clone 4 contained a point mutation that generated a premature termination condon at amino acid residue 304 (Gln-304----Ochre-304). This termination codon was located immediately after the proposed xenotropic-ecotropic recombination site and eliminated the ecotropic-related domain, including the putative membrane anchor of the glycoprotein. Clone 4REV was a true revertant derived from clone 4 in which the premature termination codon had back-mutated to re-form the wild-type sequence. These results confirm an essential role for the env gene in Friend spleen focus-forming virus pathogenesis and suggest that the encoded membrane glycoprotein contains different domains that contribute to its pathogenic function.     

Special effects of a complex probiotic containing cellulolytic bacteria Cellulomonas on actively growing rabbits

It was shown that the association of probiotic bacteria of the genuses Bacillus and Cellulomonas form biolayers on the surface of beet marc particles. The positive effect of a fodder additive that contained the biolayer on the basis of a phytomatrix on the growth and development of young rabbits was shown. Feeding of animals with a mixed fodder that contained 0.1% preparation resulted in stimulation of digestion of all components of the food. Among other components of the mixed fodder, cellulose was digested most effectively. An increase in the biomass of symbiotic bacteria and enzymatic activity in the blindgut chymus was also observed. The positive nitrogen balance demonstrated an increase in the nitrogen content in animals and a decrease of its losses with excretion. The mechanism of response of the rabbit’s organism to introduction of the complex probiotic preparation into the digestive tract is discussed.     

Antifungal activity of essential oil and its constituents from Calocedrus macrolepis var. formosana Florin leaf against plant pathogenic fungi

Resistance to conventional fungicides causes the poor disease control of agriculture. Natural products from plants have great potential as novel fungicide sources for controlling pathogenic fungi. In this study antipathogenic activity of the leaf essential oil and its constituents from Calocedrus macrolepis var. formosana Florin were evaluated in vitro against six plant pathogenic fungi. Chemical analysis of leaf oil by GC/MS allowed identification of alpha-pinene (44.2%), limonene (21.6%), beta-myrcene (8.9%), beta-caryophyllene (8.2%), caryophyllene oxide (2.4%), alpha-cadinol (1.6%), beta-pinene (1.2%), and T-muurolol (1.1%) as main components. Sesquiterpenoid components of the oil were more effective than monoterpenoid components of the oil. In particular, T-muurolol and alpha-cadinol strongly inhibited the growth of Rhizoctonia solani and Fusarium oxysporum, with the IC(50) values < 50 microg ml(-1). These compounds also efficiently inhibited the mycelial growths of Colletotrichum gloeosporioides, P. funerea, Ganoderma australe and F. solani. These results showed that T-muurolol and alpha-cadinol possess antifungal activities against a broad spectrum of tested plant pathogenic fungi and could be used as potential antifungal agents for the control of fungal diseases in plants.     

A relative of the broad-host-range plasmid RSF1010 detected in Erwinia amylovora.

Streptomycin- and sulfonamide-resistant Erwinia amylovora CA3R from California contained an 8.7-kb plasmid, pEa8.7, with a sulII-strA-strB resistance region; furthermore, PCR, sequencing, hybridization, and restriction analyses showed that pEa8.7 was closely related or identical to broad-host-range plasmid RSF1010. Although RSF1010 has been found in a variety of bacteria, this is the first report of its presence in plant pathogenic bacteria.     

鱼腥草抑菌有效成分的醇提、鉴定及抑菌效果研究

以大肠埃希菌抑菌效果为指标,采用正交实验的方法对鱼腥草抑菌有效成分的醇提条件进行优化,同时对鱼腥草醇提液进行分极分离,采用HPLC和GC-MS的方法对抑菌有效部的成分进行鉴定,并对该有效部的抑菌效果进行初步研究。实验结果表明鱼腥草抑菌有效成分醇提的最佳条件为醇浓度70%,温度80℃、料液比1?15,提取时间4 h,该条件下所获得的醇提液分极分离所获得的氯仿部抑菌效果最好,GC-MS和HPLC分析表明氯仿部中含有13种酚类物质及少量的鱼腥草素和甲基正壬酮,该有效部对大肠埃希菌(MIC:16.0 mg/mL)、金黄色葡萄球菌(MIC:8.0 mg/mL)、白色念珠菌(MIC:4.0 mg/mL)、黄曲霉(MIC:8.0 mg/mL)以及黑曲霉(MIC:8.0mg/mL)均有较好的抑菌效果。     

B．animalis V9对腹泻动物的保护性作用及其机制研究

目的研究益生菌B.animalis V9对腹泻动物的保护作用及其对腹泻致病菌的拮抗效果。方法采用自制的腹泻SPF鼠,喂服B．animalis V9,观察并检测腹泻致病菌,并在体外试验益生菌B．animalisV9对腹泻致病菌的拮抗作用。结果SPF鼠致泻动物模型喂食B．animalisV9,剂量为1．0×10^8CFU/（只·d）,3d后腹泻治愈率为90％,死亡率为9％,对照组自然恢复率为16％,死亡率为41％,其余仍有不同程度的腹泻现象。B．animalis V9在体外对志贺痢疾杆菌、沙门菌、铜绿假单胞菌和大肠埃希菌有不同程度的拮抗作用,共同培养60h后均未检测到上述4种致病菌。结论B．animalisV9可以有效的对腹泻小鼠进行治疗,其机制在于B．animalisV9对致泻菌株具有一定程度的拮抗作用。     

Characterization of the gut bacterial community in Manduca sexta and effect of antibiotics on bacterial diversity and nematode reproduction

The tobacco hornworm, Manduca sexta , is a model lepidopteran insect used to study the pathogenic and mutualistic phases of entomopathogenic nematodes (EPNs) and their bacterial symbionts. While intestinal microbial communities could potentially compete with the EPN and its bacterial partner for nutrient resources of the insect, the microbial gut community had not been characterized previously. Here, we show that the midgut of M. sexta raised on an artificial diet contained mostly Gram-positive cocci and coryneforms including Staphylococcus, Pediococcus, Micrococcus and Corynebacterium . Major perturbation in the gut community was observed on addition of antibiotics to the diet. Paenibacillus and several Proteobacteria such as Methylobacterium, Sphingomonas and Acinetobacter were primary genera identified under these conditions. Furthermore, the reproduction of the nematode Steinernema carpocapsae was less efficient, and the level of nematode colonization by its symbiont Xenorhabdus nematophila reduced, in insects reared on a diet containing antibiotics. The effect of antibiotics and perturbation of gut microbiota on nematode reproduction is discussed.     

炭疽杆菌S层的研究进展

S层是广泛存在于古细菌和真细菌细胞壁最外层的结构独特、功能特殊的成分,对它的研究具有重要的意义。炭疽杆菌是引起人畜炭疽病的病原体,对其S层的研究将为深入认识该菌的生理特性及致病机制等提供坚实的基础。就近年来对炭疽杆菌S层的结构、功能特点及应用前景等方面的研究进展做一简要的综述。     

通过导入几丁质酶基因提高巨大芽孢杆菌的生防效果

以质粒pMSDChi113为模板,经PCR扩增,获得了几丁质酶基因1.8 kb DNA片段,将该基因与大肠杆菌-芽孢杆菌穿梭质粒pHY300PLK连接,获得重组质粒pHYChi113。重组质粒经芽孢杆菌感受态方法转入巨大芽孢杆菌(Bacillus megaterium) Ap25中,获得的工程菌株B.megateriums Ap25-chi113同时具有几丁质酶和内切葡聚糖酶酶活。平板对峙实验结果表明,工程菌株对病原真菌Rhizoctonia solani,Coniothyrium fuckellii,Fusarium graminearum,Macrophoma kawatsukai,Fusarium oxysporium,Botrytis cinerea,Rhizoctonia cerea-lis,Colletotrichum gloeosporioides,Bipolarls sorohlulana的拮抗性能明显提高,尤其是对Coniothyrium fuckellii的抑制率相对于野生菌Ap25提高了13%以上。盆栽防病实验结果表明,工程菌株显著降低纹枯病菌(Rhi-zotonia cerealis)对小麦(Triticum aestivum L.)及枯萎病菌(Fusarium oxysporum)对棉花(Gossypium hirsutumLinn.)的致病能力,对这两种病原菌的防效分别是70.34 %和58.51 %,同原始菌株相比,防效分别提高了27.54 %和21.28 %。