Reconstitution of Okenone into Light Harvesting Complexes from <Emphasis Type="Italic">Allochromatium minutissimum</Emphasis>

Okenone was reconstituted into light harvesting (LH) complexes of the purple photosynthetic bacterium Allochromatium minutissimum possessing the spirilloxanthin pathway for carotenoid biosynthesis. Suppression of this pathway by diphenylamine, an inhibitor of carotenogenesis, yielded nearly carotenoidless complexes preserving their native spectral properties. Using a previously developed technique, okenone was readily reconstituted into LH1 complex (>90%) whereas its reconstitution into LH2 complex was of low efficacy (10-20%). The absorption band of the reconstituted okenone was shifted to shorter wavelength compared with its position in vivo. This is typical for other reconstituted carotenoids. The reconstitution of okenone was confirmed by Li-DS electrophoresis (in contrast to free okenone the reconstituted okenone migrated with complexes), circular dichroism spectra (reconstituted okenone exhibited optical activity), and fluorescence excitation spectrum (energy transfer from okenone to bacteriochlorophyll was at the control level).     

Use of Zymomonas mobilis and Saccharomyces cerevisiae mixed with Kluyveromyces fragilis for improved ethanol production from Jerusalem artichoke tubers

Jerusalem artichoke mashed tubers were fermented using single yeasts and a bacterium as well as mixed culture of microorganisms. Kluyveromyces fragilis, a yeast with an active inulinase, was used together with either a commercial distillery yeast, Saccharomyces cerevisiae, or the bacterium Zymomonas mobilis. After batch fermentation the best ethanol concentration of 0.48 g g(-1) for the mixed population and 0.46 g g(-1) for the single population can be obtained. The theoretical yield of the mixed cultures was 2-12% higher than for the single microorganism.     

一株产蛋白酶南极耐冷细菌的筛选及研究

从南极中山站地区分离到1株产胞外酸性蛋白酶的革兰氏阴性杆菌,该菌能在7度,20度及30度生长并产酶;其最适生长温度在20度左右,不耐盐。碳源物质中,葡萄糖对菌株的生长有利,但对蛋白酶的生成影响不大。氮源物质中,蛋白胨对菌株的生长及蛋白酶的生成效果最好,而（NH4）2SO4则是效果最好的无机氮源。该菌所产胞外蛋白酶占其蛋白酶总量的83．2％,蛋白酶反应的最适温度为40度,最适PH为5;酶活力在35度以下保持稳定,直接以酪蛋白液为培养基,在20度条件下对该菌进行摇瓶培养,6d后菌液浓度及产酶量皆到达高值并基本保持稳定,而以LB培养基（Luria-Bertani培养基）在相同条件下培养该菌,3d后菌液浓度即到达高值并基本保持稳定,酶活力则在2d后到达高值。     

大肠埃希氏菌引起的虹鳟鱼病的初步研究

１９８８年,山西省虹鳟鱼试验场的二龄虹鳟发生一种流行病,病鱼典型症状为：体色发黑,鳃丝苍白或粉红,肛门及有的鳍条充血,内脏肠、肝、脾等充血和出血。病原菌为革兰氏阴性,杆状０．９－１．２×２．３－４．５μｍ,周鞭毛,能运动,周身还有菌毛。能还原硝酸盐来亚硝酸盐;氧化酶阴性;葡萄糖发酵并产气,甲基红和腚基质试验阳性;Ｖ－Ｐ试验阴性;不产生尿素酶,苯丙氨酸脱氨酶和硫化氢;不利用丙二酸钠;不液化明胶;在Ｋ     

Response of soybean rhizosphere communities to human hygiene water addition as determined by community level physiological profiling (CLPP) and terminal restriction fragment length polymorphism (TRFLP) analysis

A new technique is presented for analyzing subgingival bacterial plaque. Different materials (polytetrafluoroethylene, gold, dentin) kept for several days in periodontal pockets of patients suffering from periodontitis were analyzed by electron microscopy and fluorescence in situ hybridization (FISH). Those parts of the carriers extending into the deepest zone of the pockets were predominantly colonized by spirochetes and Gram-negative bacteria whereas those segments in contact with a shallower region were colonized by streptococci. Independent of the material used, the bacterial colonization of the carriers appears to be similar. FISH using eubacteria- and species-specific oligonucleotides on semi-thin cross-sections of the carriers in combination with confocal laser scanning microscopy allowed detailed analysis of the architecture of biofilms and identification of putative periodontal pathogens with single cell resolution.     

Siderophore production by the magnetic bacterium Magnetospirillum magneticum AMB-1

Siderophore production by the magnetic bacterium Magnetospirillum magneticum AMB-1 is elicited by sufficient iron rather than by iron starvation. In order to clarify this unusual pattern, siderophore production was monitored in parallel to iron assimilation using the chrome azurol sulfonate assay and the ferrozine method respectively. Iron concentration lowered approximately five times less than its initial concentration only within 4 h post-inoculation, rendering the medium iron deficient. A concentration of at least 6 microM Fe(3+) is required to initiate siderophore production. The propensity of M. magneticum AMB-1 for the assimilation of large amounts of iron accounts for the rapid depletion of iron in the medium, thereby triggering siderophore excretion. M. magneticum AMB-1 produces both hydroxamate and catechol siderophores.     

南海东海岛近海固氮细菌多样性及对菜心的促生作用

海洋固氮细菌在自然界氮循环中发挥着重要作用,筛选和开发海洋固氮促生的菌种资源,对于生物菌肥的开发应用和农业生产具有重要意义。[目的]研究海洋固氮细菌的生物多样性及对陆地作物的促生作用,筛选优良的植物根际促生菌株。[方法]通过形态特征、生理生化试验和16S rRNA基因序列比对进行菌属鉴定;将解磷、解钾、产蛋白酶和纤维素酶等性能优良的菌株作为菜心盆栽试验的组合菌液,探究对菜心能否起促生作用。[结果]本研究从南海东海岛的海岛沉积物中筛选出18株固氮菌,分布在6个属9种,不动杆菌属4株,假交替单胞菌属1株,芽孢杆菌属8株,嗜冷杆菌属1株,海单胞菌属1株,交替单胞菌属3株。菜心幼苗经过组合菌剂的浇灌,在茎高、茎粗、最大叶宽和最大叶长4个指标均表明对菜心有显著的促生作用。其中,以芽孢杆菌属和不动杆菌属的菌株在菜心的生长过程中起关键的促进作用,对菜心的促生性能最佳。[结论]南海近海具有种类丰富多样的固氮细菌,以芽孢杆菌属和不动杆菌属的菌株促生作用最为显著,具有开发成微生物菌肥的潜力,为优良的海洋促生微生物菌种资源的定向利用及蔬菜的无公害生产提供重要依据。     

不同昆虫寄主对昆虫病原线虫共生菌的敏感性比较

用菜青虫、棉铃虫、甜菜夜蛾、玉米螟、粘虫、黄粉虫等 6种昆虫对 1 0株昆虫病原线虫共生菌进行了敏感性测定。结果表明 :供试菌株对 6种昆虫都有胃毒活性 ,不同菌株对同一种昆虫的毒力差别较大 ,同一菌株对不同昆虫差别也很大。 1 0株菌在 1 2 0h对菜青虫的校正死亡率和体重抑制率均最高 ,显然是最敏感的寄主。在 1 0株共生菌中 ,XenorhabdusnematophilaHB3 1 0 5 9菌株的胃毒活性最高。     

以四氢嘧啶为主要相容性溶质的中度嗜盐菌I15的分离和特性研究

从草地土壤中分离到一株中度嗜盐菌I15,经过16S rDNA(GenBank登录号为DQ010162)序列分析、形态学和生理生化特征分析,该菌株初步鉴定为Virgibacillus marismortui。I15能在0%～25%NaCl的培养基中生长,最适生长NaCl浓度为10%,最适生长温度为30℃,最适pH为7.5～8.0。在高盐条件下,I15细胞内主要的相容性溶质为四氢嘧啶,在15%NaCl培养基中其含量达到1.608mmol/(g\5cdw),占到相容性溶质总摩尔含量的89.6%。渗透冲击试验表明I15细胞内四氢嘧啶在低渗冲击时能够快速分泌到细胞外,在高渗冲击冲剂时能够较快地重新合成。     

细菌菌膜的成分、调控及其与植物的关系

菌膜是细菌群落发展的一种高度组织化的群体状态。在菌膜形成过程中,细菌胞外物质EPS(Exopolysaccharides)、eDNA(Extracellular DNA)、胞外蛋白等都参与菌膜的形成,它们为菌膜提供机械稳定性,帮助细菌粘附到物体表面,促进菌膜中不同细菌间物质的循环及基因的水平转移。菌膜形成涉及到群体感应、C-di-GMP(Cyclic diguanylate monophosphate)和sRNA等一系列调控机制。土壤环境中栖息着大量的微生物,许多土壤微生物定殖于植物根际,从而与植物发生着密切的相互作用;菌膜的形成是细菌稳定定殖于植物根际的关键因素,有助于植物促生菌或致病菌在根际更好的生存。本文就菌膜的成分、调控及其与植物的关系等三个方面的内容进行综述。