发菜的显微及亚显微结构的观察

通过光学显微镜、扫描电镜和透射电镜的观察、了解到一条发菜原植体大约由数十万计的念珠状细胞所组成,其藻丝多为单链,但也发现有分枝现象。整个原植体包被着厚薄不均的胶质鞘,外观粗糙,沟稜状起伏,且多裂隙。念珠状细胞为典型的原核细胞。细胞壁有三层结构,中央为色浅的核质区,四周为细胞质区其中散布着大量膜层薄而散乱的类囊体,膜上附有大量 rRNA 和藻胆体颗粒。还发现有膜层密集形如指纹的小类囊体。在细胞质中还分布着结构颗粒,多角体、聚磷酸体等嗜锇物质结构.一般细胞都具有分裂能力,方式多为横缢,先是细胞壁逐渐向中央扩展,最后将母细胞分成两个子细胞.从异形胞的结构特征来看,主要功能是渡过恶劣环境以保存物种。     

CYTOCHROME c548 IN NOSTOC SP. (CYANOPHYCEAE): AN ELECTRON ACCEPTOR FROM REDUCED NADP IN THE DARK1

A c-type, carbon monoxide-binding cytochrome was isolated and studied from an endophytic Nostoc sp. Enzymatic transfer of electrons from NADPH to this cytochrome was demonstrated in cell-free preparations under dark, anaerobic conditions, probably mediated by NADPH-cytochrome reductase or ferredoxin-NADP reductase present in the extracts. This cytochrome, with an α-peak at 548 nm, had physicochemical properties similar to the low potential c-type cytochrome, cytochrome c₅₄₉, previously described by other workers from Anacystis nidulans. The participation of such c-cytochromes in dark electron transport, possibly respiratory, of bluegreen algae is strongly indicated.     

发菜蛋白质组双向电泳技术的建立及优化

为建立适用于发菜(Nostoc flagelliforme)蛋白质组研究的双向电泳技术,对发菜蛋白质的提取、裂解、上样量、IEF及SDS-PAGE电泳等关键步骤进行了优化,结果显示:发菜蛋白质主要分布在pH 4～7范围内,采用改良TCA法可提高提取液中蛋白质的含量和双向电泳图谱的分辨率,裂解液含60 mmol/L DTT,24 cm IPG胶条上样量1.5 mg时不仅提高了蛋白质的溶解性,而且改善了双向电泳的分离效果,得到近800个蛋白点,且蛋白点清晰,图谱分辨率较好.采用优化后的双向电泳体系提高了发菜蛋白质双向电泳的分辨率和重复性,建立起一套适用于发菜蛋白质组分析的双向电泳方法.     

Biotransformation of hydrocortisone by a natural isolate of Nostoc muscorum

Hydrocortisone was converted in the culture of an isolated strain of the cyanobacterium Nostoc muscorum PTCC 1636 into some androstane and pregnane derivatives. The microorganism was, isolated during a screening program from soil samples collected from paddy fields of north of Iran. The bioproducts obtained were purified using chromatographic methods and identified as 11beta-hydroxytestosterone, 11beta-hydroxyandrost-4-en-3,17-dione and 11beta,17alpha,20beta,21-tetrahydroxypregn-4-en-3-one on the basis of their spectroscopic features.     

PHOTOSYNTHESIS OF TWO MORPHOLOGIES OF NOSTOC PARMELIOIDES (CYANOBACTERIA) AS RELATED TO CURRENT VELOCITIES AND DIFFUSION PATTERNS1

Colonies of the stream-inhabiting cyanobacterium Nostoc parmelioides Kützing often contain a single endosymbiotic dipteran larva Cricotopus nostocicola (Wirth), which induces a morphological change from small, spherical colonies to larger, ear-shaped colonies. At a current velocity of 0 cm · s^?1, whole colonies containing the midge showed overall rates of ¹⁴CO₂ uptake and nitrogenase activity that were higher than those when the midge was absent (sphere-shaped colonies). Spherical colonies incubated at current velocities of 5-10 cm · s^?1did not show higher rates of ¹⁴CO₂ or ¹⁵N₂ incorporation than those with the larvae (ear-shaped colonies). Ear-shaped colonies extended well into regions of higher current velocity, whereas spherical colonies did not. Photosynthesis of ear-shaped colonies was stimulated by increased current velocity, increased inorganic C and decreased O₂ concentrations. Moreover, levels of O₂ at the surface of midge-inhabited colonies decreased with increased current velocity. The morphological change induced by the larva is detrimental (lowers photosynthesis and N₂ fixation) in quiescent water but not at current velocities above 10 cm · s^?1. This is probably a result of higher diffusion of O₂ and CO₂ associated with the midge-induced morphology.