Fusion of chromatophores derived from Rhodopseudomonas sphaeroides

Fusion of chromatophores, the photosynthetic membrane vesicles isolated from the intracytoplasmic membranes of Rhodopseudomonas sphaeroides, was achieved by the use of poly(ethylene glycol) 6000 as fusogen. Ultracentrifugation, electron microscopy, intrinsic density and isotope labeling were used to demonstrate chromatophore fusion. Although studies of the flash-induced shift in the carotenoid absorbance spectrum indicated that the membrane was rendered leaky to ions by either the fusion procedure or the increased size of the fused products, the orientation and integrity of fused chromatophores were otherwise demonstrated to be identical to control chromatophores by freeze-fracture electron microscopy, proteolytic enzyme digestion, enzymatic radioiodination, and transfer of chromatophore phospholipids mediated by phospholipid exchange protein extracted from Rps. sphaeroides.     

强化类球红细菌辅因子NADPH再生以提高法尼醇的产量

法尼醇(Farnesol,FOH)是由焦磷酸异戊烯基(IPP)和焦磷酸二甲基烯丙基(DMAPP)合成的法尼酰基焦磷酸盐(FPP)去焦磷酸化作用生成的。在类球红细菌中IPP和DMAPP是由MEP途径生成,而完整的MEP途径需要消耗大量的辅因子NADPH,增加胞内NADPH的量有可能强化FOH的合成。文中从增加NADPH的生成和降低NADPH的消耗这两个策略出发,分别干扰了编码6-磷酸葡萄糖异构酶基因(pgi)和谷氨酸脱氢酶基因(gdhA)的表达,同时强化了磷酸戊糖途径中6-葡萄糖磷酸脱氢酶基因(zwf)和6-葡萄糖酸磷酸脱氢酶基因(gnd)的表达。实验结果表明,经改造的菌株NADPH含量显著增加,干扰菌株中菌株RSpgii的产量较高,为3.91 mg/g,在过表达的菌株中同时过表达zwf和gnd基因的重组菌株(RSzg)的FOH产量提高到了3.43 mg/g。为了获得FOH产量更高的菌株,以RSpgii为出发菌株,分别与zwf和gnd组合调控,获得的菌株RSzgpi的产量达到了最高量为4.48 mg/g,是出发菌株RS-GY2产率的2.24倍。     

Rhodobacter sphaeroides和Rhodovulum sulidophilum LHII的α和β亚基的交叉作用关系

类球红细菌(Rhodobacter sphaeroides)和嗜硫小红卵菌(Rhodovulum sulidophilum)为不同属的两种光合细菌,前者的捕光系统II由pucB、pucA基因编码产生的β亚基和α亚基组装形成,后者的捕光系统II由pucsB、pucsA基因编码产生的β亚基和α亚基组装形成.将这两组基因交叉组合,克隆到包含puc启动子的表达载体中,得到两个表达质粒即pRKpucsBpucA和pRKpucBpucsA,然后通过接合转移方法分别转入LHI、LHII和RC缺陷型菌株DD13中,两种接合转移菌株都可以形成捕光系统II并进入光合细菌膜系统.     

A Simplified Colorimetry without Incineration of Phosphorus in Phosphatides

An NAD linked formate dehydrogenating enzyme which catalyzed the last step of methanol oxidation system was extracted from the methanol-grown Kloeckera sp. No. 2201. The specific activity of the enzyme in the extract of methanol-grown cells was found to be considerably higher than that of the glucose-grown cells. The enzyme was purified about 35-fold from the extract of methanol-grown cells by heat treatment, column chromatographies on DEAE-cellulose and on hydroxylapatite, and Sephadex G-200 gel filtration. The purified enzyme was shown to be homogeneous by analyses with electrophoresis and ultracentrifuga-tion. The purified enzyme was a kind of NAD: formate oxidoreductase (EC, 1.2.1.2) which catalyzed specifically the oxidation of formate to carbon dioxide. The Km values were 22 mm for formate and 0.1 mm for NAD. The enzyme was inactivated by potassium cyanide, sodium azide, and p-chloromercuribenzoate but not by any metal-chelating reagents tested. Other general properties of the enzyme were also investigated.     

Structure of Porriolide,a New Metabolite from Alternaria porri

Compounds from a soil isolate of Penicillium sp. MG-11 showed remarkable convulsive activity against silkworms. Activity-based fractionation of an acetone extract of the fermentation products resulted in the isolation of four compounds. One was identified as verruculogen, which was an active principle. Another compound, acetoxydehydroaustin, was new and was structurally characterized by spectral data and a single-crystal X-ray analysis. The two other compounds were identified as dehydroaustin and austin on the basis of the spectral data. Although the latter three compounds were not active themselves, they enhanced the convulsive activity of verruculogen in a silkworm bioassay. Three additional compounds with no identifiable activity were also isolated. Two of them were identified as austinol and dehydroaustinol, and the third was determined to be a new related compound named neoaustin by an X-ray analysis of crystals.     

含硒类球红细菌的研究

为了确定类球红细菌转硒培养的最佳条件 ,研究了无机硒的加入浓度、时间以及分批补料培养对菌体生长和转硒效率的影响。实验表明 ,无机硒的浓度低于 1× 10 -5mol/L时 ,对类球红细菌的生长基本没有影响 ,并能将6 3.9%的无机硒转化为有机硒。转硒的最佳时间是在接种后 12h左右 ,此时转硒效率最高。实验还表明 ,分批补料培养可以提高菌体浓度 ,可使转硒效率和绝对量增加。体内试验表明 ,用 5mL/kgbw和 10mL/kgbw剂量的含硒类球红细菌灌养小鼠 ,可以使其全血GSH Px酶活性提高 2 0 .9%和 2 5 .5 % ,使其血清丙二醛 (MDA)含量降低2 1.0 %和 2 3.2 %。     

球形红假单胞菌反应中心中蛋白的量子化学研究

采用重叠二体近似方法和建立在从算水平上的扩展负本征值因数计算方法（extended negative factor counter method）研究了球形红假单胞菌（Rhodobacter sphaeroides(Van Niel)Imhoff,Truper et Pfennin）中兴合反应中心中蛋白链L及M的电子结构。结果表明：（1）对组成蛋白链L（M）的前线轨道有重要贡献的氨基酸残基分布在L链的自由螺旋区（M链的α螺旋区）。由于自由螺旋是有柔曲性的,它易于在电子转移的过程中改变其构象并降低体系的能量,而α螺旋结构却相对稳定,这种差别有可能是光合反庆中心中电子转移只沿L支进行的原因之一。（2）与特殊对分子及辅助叶绿素分子形成轴向配位的组氨酸残基对于特殊对P和辅助叶绿素分子的ELUMO有重要影响,但此组氨酸的相应分子轨道的贡献并没有出现在蛋白链的前线轨道组成中。这意味着色素分子与蛋白链之间的相互作用对蛋白链前线轨道的贡献没有影响,但却能影响相应色素分子的ELUMO能级。     

Identification of two new denitrifying strains of Rhodobacter sphaeroides

Abstract Highly specific polyclonal and antibodies against either nitrate, nitrite or nitrous oxide reductases from a photosynthetic denitrifying bacterium Rhodobacter sphaeroides f. sp. denitrificans were used to show the presence of immunologically reactive proteins in strains that Pellerin and Gest had shown to grow in the dark with nitrate as a terminal acceptor [9]. Two strains of this bacterium, namely 81-3 and 2.4.3 synthesized the three denitrifying enzymes and were capable of denitrification. Strains 81-1 and 2.4.1 (neotype) both expressed nitrate reductase activities but nitrite reductase was not detected since these strains did not reduce nitrite. They also did not grow in the dark with nitrate as a terminal acceptor. Each of strains 81-1, 81-3, 2.4.1 and 2.4.3 contain four plasmids. R. sphaeroides f. sp. denitrificans , however, contains only one large 108 kb plasmid, which is distinctly different in size from those detected in the other strains. This indicates that the 108 kb plasmid is not necessarily specific for denitrification.     

氨和谷氨酰胺对浑球红假单胞菌（Rhodobacter sphaeroides）固氮酶...

浑球红假单胞菌菌株601具有迅速对外源氨作出“关闭”固氮酶活性的反应。氨对固氮酶的抑制作用,可被谷氨酰胺合成酶(GS)抑制剂MSX所解除。反之,加入Glu代谢抑制剂DON,可延长氨抑制的持续时间。Gln对固氮酶也有抑制作用。在脱腺苷化GS的透性细胞中,加入Gln可抑制固氮酶活性,同时,GS腺苷化状态提高。然而,氨则对透性细胞的固氮酶活性和GS腺苷化状态没有影响。