紫细菌光合机构及光合作用基因的表达调控

紫细菌是研究细菌光合作用的重要生物。介绍了紫细菌光合机构捕光色素蛋白复合体Ⅰ(light-harvesting I)、捕光色素蛋白复合体Ⅱ(light-harvesting II)和光化学反应中心(reaction center)的结构, 并探讨了其光合作用基因的转录调控机制, 重点阐述了PpsR/AppA系统对紫细菌光合作用基因的转录调控。     

Affinity purification of a siderophore that exhibits an antagonistic effect against soft rot bacterium

Bacterial colonies were isolated from different Egyptian soil samples. From these isolates, one bacterial species was found to produce siderophore. Using classical and biochemical identification methods, the siderophore producing isolate was identified as Pseudomonas fluorescens. Based on the affinity of siderophores for metal ions, an affinity chromatography system was designed for the purification of the siderophore in one step. It was possible to isolate 25 mg siderophore per liter of culture media. The purified siderophore was found to exist in two forms of approximately 30 and 90 kD. They are believed to be polymers of several siderophore molecules. Both forms were found to be active against the pathogen Erwinia carotovora var. carotovora, the causal bacteria of soft rot disease on potato tubers. The advantage of this method over other purification methods is that it uses metal ion so it can be applied for the purification of the known types of siderophores. Moreover, the purification is based on affinity chromatography, so the siderophore purity state permits several biotechnological applications without further treatments.     

几种重金属离子对光合细菌生长的抑制效应

光合细菌因其在自然生态系统中的意义与较大的应用价值 ,一直受到国内外科学工作者的重视 ,无论基础研究 ,还是应用研究 ,都取得了重大的进展。其应用研究主要为 3方面 :①用于高负荷有机废水处理 ;②用于水产养殖。它具有作为养殖水质净化剂、用于鱼虾贝幼体培育、作为动物性生物饵料的饵料、作为成鱼成虾的饲料添加剂、防治病等方面作用[6] ;③在农业上的应用。在光照嫌气条件下 ,大多数细菌能有效地固定Ｎ2 ,故在淹水的耕作土壤(如水稻田 )里 ,它能提高土壤Ｎ素水平 ,从而提高土壤肥力 ,光合细菌还能氧化或分解土壤中Ｈ2 Ｓ和胺等有毒化…     

禾谷缢管蚜体内的病毒结合蛋白基因的克隆与原核表达

利用一对特异性引物,用PCR的方法从禾谷缢管蚜体内扩增出了病毒结合蛋白基因,序列测定结果表明其长度 为1647 bp,编码548个氨基酸,与GenBank中的禾谷缢管蚜美国生物型Buchnera groELNT核苷酸序列同源性为97%,氨基酸同源性为97.4%。构建了2个原核表达载体并进行表达得到了69kD融合蛋白和63kD的非融合蛋白。     

Rheological properties of polysaccharides produced by a Zoogloea sp.

A newly isolated marine bacterium, identified as Zoogloea sp., produced two different polysaccharides: one was water-soluble and the other was cell-bound. Both had non-Newtonian, pseudoplastic fluid behaviour and the solutions had low activation energies. The solutions of these polysaccharides showed rheological behaviour over a wide range of pH (2–12) and temperature (20–80 °C), and compatibility with NaCl.     

Soil biosensor for the detection of PAH toxicity using an immobilized recombinant bacterium and a biosurfactant

A biosensor for detecting the toxicity of polycylic aromatic hydrocarbons (PAHs) contaminated soil has been successfully constructed using an immobilized recombinant bioluminescent bacterium, GC2 (lac::luxCDABE), which constitutively produces bioluminescence. The biosurfactant, rhamnolipids, was used to extract a model PAH, phenanthrene, and was found to enhance the bioavailability of phenanthrene via an increase in its rate of mass transfer from sorbed soil to the aqueous phase. The monitoring of phenanthrene toxicity was achieved through the measurement of the decrease in bioluminescence when a sample extracted with the biosurfactant was injected into the minibioreactor. The concentrations of phenanthrene in the aqueous phase were found to correlate well with the corresponding toxicity data obtained by using this toxicity biosensor. In addition, it was also found that the addition of glass beads to the agar media enhanced the stability of the immobilized cells. This biosensor system using a biosurfactant may be applied as an in-situ biosensor to detect the toxicity of hydrophobic contaminants in soils and for performance evaluation of PAH degradation in soils.     

Inhibition of the Bacterial Cell Wall Synthesis in vitro by Enduracidin,a New Polypeptide Antibiotic

Adenosine 5′-phosphosulfate (APS) kinase from a thermophilic bacterium, Bacillus st ear other mophilus, was purified to apparent homogeneity. The apparent molecular weight was 50 kDa, consisting of two 26-kDa subunits. The enzyme was very thermostable and lacked cysteine and methionine residues. Enzyme activity was more stimulated with Mn^{2 +} , Zn^{2 +}, or Co^{2 +} than with Mg^{2 +} and the K_m for ATP and APS were 220 µM and 42 µM, respectively.