枯草芽孢杆菌抗菌蛋白X98Ⅲ的纯化与性质

枯草芽孢杆菌（Bacillussubtilis）BS－98是一株能强烈抑制苹果轮纹病菌（Physalosporapiricola）等植物病原真菌的拮抗菌株。BS－98菌株培养液经硫酸铵分级盐析、SephadexG－100柱层析和DEAE－纤维素（DE32）柱层析后分离纯化出一种抗菌蛋白,命名为X98Ⅲ。蛋白电泳分析结果表明,此蛋白分子量为59000,等电点为4．50．醋酸纤维膜电泳后经特异染色证明X98Ⅲ含糖及胀。用DNS法测其含糖量为6％。此蛋白对热稳定,对蛋白酶部分敏感。氨基酸组分分析表明,该蛋白含11种不同氨基酸,尤富含谷氨酸和半胱氨酸等,而缺少天冬氨酸等。纯化后的X98Ⅲ对苹果轮纹病菌、芦笋茎枯病菌等有很强的抑制作用。X98Ⅲ的抑菌机理主要是溶解细胞壁,造成菌丝畸形、孢子不发芽或发芽异常。     

脑锌代谢与阿尔茨海默病

锌是中枢神经系统含量最丰富的过渡金属元素之一,对维持中枢神经系统正常生理功能具有重要作用,其稳态失衡与多种疾病有关。阿尔茨海默病是一种多病因神经退行性疾病,以β-淀粉样斑块形成和神经原纤维缠结为主要病理特征。研究表明,脑锌代谢紊乱在阿尔茨海默病发病过程中扮演重要角色,但确切机制尚不十分清楚。综述了脑锌代谢和稳态调控以及锌和锌转运蛋白参与β-淀粉样蛋白沉积与老年斑形成的病理过程,并探讨了金属一蛋白阻尼复合物如何通过恢复脑锌稳态延缓疾病进程、改善患者认知能力的治疗策略。     

Infection with the fungal endophyte Epichloë festucae may alter the allelopathic potential of red fescue

Red fescue (Festuca rubra) is a perennial grass used as both forage and turfgrass. Asymptomatic plants of this species are systemically infected by the fungal endophyte Epichloë festucae, which has a beneficial effect on the infected plants. The aim of this study was to determine the effect of the endophyte Epichloë festucae on the allelopathic potential of F. rubra against four associated pasture species that are also considered as weeds in lawns, Trifolium pratense, Trifolium repens, Lotus corniculatus and Plantago lanceolata. Two experiments were designed to evaluate the allelopathic effect of extracts from the roots and leaves of endophyte‐infected (E+) and non‐infected (E?) plants on the germination and seedling growth of the four target species. Regardless of the endophyte status of the host plant, leaf extracts elicited a stronger reduction in germination and seedling growth than root extracts. Extracts from E+ plants reduced the speed of germination index of Trifolium spp. to a greater extent than those from E? plants. Radicle length of the target species was the parameter most affected by the presence of the endophyte in F. rubra. Root extracts from E+ plants had a greater inhibitory effect on the radicle growth of the target species than did root extracts from E? plants. A greater concentration in total phenolic compounds was found in the roots of E+ plants than of E?; however, this difference was not observed in the leaves. Thus, the allelopathic potential of F. rubra is altered in infected plants.     

Isolation and characterization of a bacterium that mineralizes toluene in the absence of molecular oxygen

A bacterium tentatively identified as a Pseudomonas sp. was isolated from a laboratory aquifer column in which toluene was degraded under denitrifying conditions. The organism mineralized toluene in pure culture in the absence of molecular oxygen. In carbon balance studies using [ring-UL-¹⁴C]toluene, more than 50% of the radioactivity was recovered as ¹⁴CO₂. Nitrate and nitrous oxide served as electron acceptors for toluene mineralization. The organism was also able to degrade m-xylene, benzoate, benzaldehyde, p-cresol, p-hydroxybenzaldehyde, p-hydroxybenzoate and cyclohexanecarboxylic acid in the absence of molecular oxygen.     

动物气味的顶空取样技术及其在水貂肛腺成分分析中的应用

我们设计了一种用于动物气味的顶空 (headspace)取样装置 ,并结合溶剂解吸附和气质联用技术 ,通过对水貂 (Mustelavision)肛腺分泌物的挥发性成分的分析验证这种装置的可行性。出现 5个气谱峰 ,对应的质谱显示其分子量和分子式依次为峰 1:10 2 (C5H10 S)、峰 2 :10 4(C5H12 S)、峰 3:10 2 (C5H10 S)、峰 4:136(C5H12 S2 )和峰 5 :134 (C5H10 S2 )。峰 1、峰 3和峰 5分别为以前研究所鉴定出的 3种主要成分 :2 ,2 二甲基硫代环丁烷、2 乙基硫代环丁烷和 3,3 二甲基 1,2 二硫代环戊烷 ,2 ,2 二甲基硫代环丁烷为优势成分 ,组成无性别间差异。这些结果与以前研究一致 ,说明了这种顶空取样装置的可靠性。峰 2和峰 4两种成分以前在水貂肛腺中未曾发现 ,初步分析可能分别为 3 甲基 1 丙基硫醇和 1,5 戊二硫醇。尽管这两个成分有待进一步分析确定 ,但可以肯定分子量为 10 4和 136的成分不仅在水貂肛腺分泌物中没有发现过 ,而且在已经研究过的鼬属动物和食肉类的肛腺中都未发现过 ,能检测出更多的成分 ,说明这种方法的可靠性很高。     

Description of “<Emphasis Type="Italic">Desulfotomaculum nigrificans</Emphasis> subsp. <Emphasis Type="Italic">salinus</Emphasis>” as a New Species, <Emphasis Type="Italic">Desulfotomaculum salinum</Emphasis> sp. nov.

This study focused on the physiological, chemotaxonomic, and genotypic characteristics of two thermophilic spore-forming sulfate-reducing bacterial strains, 435^T and 781, of which the former has previously been assigned to the subspecies “Desulfotomaculum nigrificans subsp. salinus”. Both strains reduced sulfate with the resulting production of H₂S on media supplemented with H₂ + CO₂, formate, lactate, pyruvate, malate, fumarate, succinate, methanol, ethanol, propanol, butanol, butyrate, valerate, or palmitate. Lactate oxidation resulted in acetate accumulation; butyrate was oxidized completely, with acetate as an intermediate product. Growth on acetate was slow and weak. Sulfate, sulfite, thiosulfate, and elemental sulfur, but not nitrate, served as electron acceptors for growth with lactate. The bacteria performed dismutation of thiosulfate to sulfate and hydrogen sulfide. In the absence of sulfate, pyruvate but not lactate was fermented. Cytochromes of b and c types were present. The temperature and pH optima for both strains were 60–6°C and pH 7.0. Bacteria grew at 0 to 4.5–6.0% NaCl in the medium, with the optimum being at 0.5–1.0%. Phylogenetic analysis based on a comparison of incomplete 16S rRNA sequences revealed that both strains belonged to the C cluster of the genus Desulfotomaculum, exhibiting 95.5–98.3% homology with the previously described species. The level of DNA–DNA hybridization of strains 435^T and 781 with each other was 97%, while that with closely related species D. kuznetsovii 17^T was 51–52%. Based on the phenotypic and genotypic properties of strains 435^T and 781, it is suggested that they be assigned to a new species: Desulfotomaculum salinum sp. nov., comb. nov. (type strain 435^T = VKM B 1492^T).     

Crystal structure of Zn(trz)Cl (trz = 11,2,4,-triazolato); a layered compound with triply bridging triazolato groups

ZnCl₂ reacts with 1,2,4-1H-triazole to afford Zn(trz)Cl. A spontaneous deprotonation of Htrz occurs. The crystal structure of Zn(trz)Cl has been solved. The compound crystallizes in the space group P2₁/n. The lattice parameters are a = 8.863(4), B = 9.762(4), C = 6.146(3) Å, β = 99.56(10)°, with Z = 4. The 1,2,4-triazolato bridges three zinc atoms through its three nitrogen atoms, affording a layered structure. The zinc atom is in an N₃Cl tetrahedral coordination. The layers are not planar, but rather corrugated. The chlorine atoms point to either side of the layers, and play the role of spacers. The shortest interlayer ZnZn separation is 5.701 Å.     

Evolutionary relationships in thePodalyrieae andLiparieae (Fabaceae) based on morphological, cytological, and chemical evidence

Taxonomic relationships amongst the genera of the southern African tribesPodalyrieae andLiparieae are discussed. Data gained from morphological, cytological and chemical investigations are analyzed cladistically to determine relationships. The genusCadia (tribeSophoreae) is included in the investigation to establish whether it should be transferred to thePodalyrieae. The results clearly indicate that thePodalyrieae andLiparieae are monophyletic and that they should be united, but thatHypocalyptus andCadia should be excluded. Within the monophyletic group, there are two distinct subclades each supported by three apomorphies. The results also show that there is a strong sister relationship betweenAmphithalea andCoelidium. In the taxonomic treatment theLiparieae are placed into synonymy under thePodalyrieae and two subtribes are recognized. A key to the genera in the tribe is given, followed by a synopsis of the genera.     

玉米雄穗性状遗传结构与形成分子机制*

玉米为雌雄同株异花植物,其雄穗着生于植株顶部,雌穗腋生。雄穗一方面需产生足量花粉以保证雌穗授粉结实,另一方面由于对下部叶片的遮蔽作用和自身营养需求,其生长发育会同时影响叶片光合作用效率和能量分配,因此优化雄穗结构是提高玉米产量的重要措施之一。玉米雄穗性状包括雄穗分枝数、雄穗分枝长度、雄穗主轴长度、雄穗分枝总长度、雄穗分枝角度等,均为多基因控制的数量性状。自20世纪90年代,研究者开始利用数量性状位点(quantitative trait locus,QTL)定位方法解析玉米雄穗性状遗传结构;随着玉米自交系B73等参考基因组释放,以及DNA微阵列、基因组重测序等高通量基因分型技术的日益成熟,全基因组关联分析(genome-wide association study, GWAS)成为数量性状遗传研究的主流方法,目前已鉴定出大量玉米雄穗性状遗传位点。通过总结雄穗性状遗传定位研究结果,构建一致性图谱并挖掘定位热点区间,有助于进一步了解雄穗性状遗传结构特征及指导雄穗性状候选基因克隆。此外,通过对调控雄穗发育的已知基因进行功能分类,可为解析玉米雄穗发育的遗传网络和调控通路提供理论支撑。