An immunological assessment of lysosomal enzymes and other macromolecules sulfated during vegetative growth of Dictyostelium discoideum

Western blotting and immunoprecipitation data indicated that lysosomal enzymes represent a subset of the sulfated macromolecules present in vegetative Dictyostelium discoideum amoebae and account for less than 2.5% of the total sulfate incorporated during vegetative growth. These data suggest that the majority of the highly sulfated macromolecules of vegetative D. discoideum amoebae are not related to the lysosomal enzymes.     

黏菌分类学史研究

黏菌是菌物中一个特殊和有趣的类群。为了准确而深刻地认识黏菌的内涵、多样性和系统发育关系等分类学问题,本文从黏菌命名起点开始循览黏菌分类学的发展历程,结合黏菌分类学的最新研究进展,考证了黏菌纲Myxomycetes内涵的变化和分类系统的演变及黏菌分类学研究的重要事件,并论述了中国黏菌分类学研究史,从而系统阐述了国内外黏菌分类学研究历史的沿革和演化。     

Phylogeny of Physarida (Amoebozoa,Myxogastria) Based on the Small‐Subunit Ribosomal RNA Gene,Redefinition of Physarum pusillum s. str. and Reinstatement of P. gravidum Morgan

Myxomycetes (also called Myxogastria or colloquially, slime molds) are worldwide occurring soil amoeboflagellates. Among Amoebozoa, they have the notable characteristic to form, during their life cycle, macroscopic fruiting bodies, that will ultimately release spores. Some 1,000 species have been described, based on the macroscopic and microscopic characteristics of their fruiting bodies. We were interested in Physarum pusillum (Berk. & M.A. Curtis) G. Lister, a very common species described with two variants, each bearing such morphological differences that they could represent two distinct species. In order to test this, we observed key characters in a large selection of specimens attributed to P.  pusillum, to its synonyms (in particular Physarum gravidum), and to related species. In addition, the small‐subunit ribosomal RNA gene was obtained from seven of these specimens. Based on these data, we provide a comprehensive phylogeny of the order Physarida (Eukaryota: Amoebozoa: Conosa: Macromycetozoa: Fuscisporidia). Morphology and phylogeny together support the reinstatement of P. gravidum Morgan 1896 with a neotype here designated, distinct from P. pusillum, here redefined.     

Functional analysis of actin fibrils in Physarum polycephalum

Summary Fluorochromed heavy meromyosin (TRITC-HMM) was microinjected as a molecular probe into small sandwich-plasmodia of Physarum polycephalum with the aim to demonstrate the spatial morphology and to analyze the dynamic activity of the fibrillar actin system in the living state. The plasmodia display different fibrillar organizations with a polygonal arrangement in the front region (FR) and a parallel or helical arrangement along protoplasmic veins in the intermediate (IR) and uroid region (UR). Quantitative evaluations by measuring the total length, lifetime, dynamic activity, long-term stability and optical density of fibrils reveal distinct differences between the three plasmodial regions: The total length (FR = 27.1 ± 18.5 m, IR = 24.8 ± 12.9 m, UR= 12.3 ± 4.7 m), the lifetime (FR = 12.2 ± 3.4 min, IR=10.5 ± 3.7 min, UR = 6.0 ± 3.4 min), and the dynamic activity as measured in length changes per min (FR = 17.9 ± 11.3 m, IR = 13.1 ± 3.9 m, UR = 8.3 ± 3.9 m) distinctly decrease from the front to the uroid region. On the other hand, the greatest stability as determined by lifetime changes in length (FR = -2.4 ± 16.2 m, IR = 0.3 ± 10.1 m, UR = -6.6 ± 8.9 m) and the highest optical density as expressed in grey-values (FR = 57.0 ± 14.1 gv, IR = 115.6 ± 26.1 gv, UR 62.5 ± 8.1 gv) were found for actomyosin fibrils of the intermediate region. The morphological and physiological data of the present paper are discussed with respect to the biological significance of the fibrillar microfilament system in Physarum polycephalum.     

网柄细胞状黏菌的化学成分及药理作用研究进展

文中综述了从网柄细胞状黏菌中分离得到的DIF-1及其衍生物、氯代苯并呋喃、三联苯化合物等芳香族化合物,脂肪酸和磷酸化合物、酶以及糖类等,并介绍了各成分的药理或生理作用等。表明网柄细胞状黏菌可以成为某些活性成分及药物的新来源。     

Phenotypic variability in unicellular organisms: from calcium signalling to social behaviour

Historically, research has focused on the mean and often neglected the variance. However, variability in nature is observable at all scales: among cells within an individual, among individuals within a population and among populations within a species. A fundamental quest in biology now is to find the mechanisms that underlie variability. Here, we investigated behavioural variability in a unique unicellular organism, Physarum polycephalum. We combined experiments and models to show that variability in cell signalling contributes to major differences in behaviour underpinning some aspects of social interactions. First, following thousands of cells under various contexts, we identified distinct behavioural phenotypes: ‘slow–regular–social’, ‘fast–regular–social’ and ‘fast–irregular–asocial’. Second, coupling chemical analysis and behavioural assays we found that calcium signalling is responsible for these behavioural phenotypes. Finally, we show that differences in signalling and behaviour led to alternative social strategies. Our results have considerable implications for our understanding of the emergence of variability in living organisms.     

Effects of medium composition on the growth and lipid production of microplasmodia of Physarum polycephalum

Physarum polycephalum is a plasmodial slime mold. One of the trophic stages in the life cycle of this organism is a plasmodium. In submerged culture, plasmodia are fragmented into microplasmodia. The latter both lack cell walls and are capable of rapid growth. There has been limited information on the effects of medium composition on the growth and lipid accumulation of microplasmodia. In this study, optimization of medium components by response surface methodology showed that tryptone and yeast extract concentrations had the most significant effects on lipid and biomass production; significant synergistic interactions between glucose and tryptone concentration on these responses were also recorded. The optimal medium was composed of 20 g/L of glucose, 6.59 g/L of tryptone, and 3.0 g/L of yeast extract. This medium yielded 13.86 g/L of dry biomass and 1.97 g/L of lipids. These amounts are threefold higher than those of the American Type Culture Collection (ATCC) medium. In addition, biomass and lipid production reached maximal values between only 4 and 5 days. Fatty acid compositions analysis by gas chromatography-mass spectrometer (GC–MS) revealed that P. polycephalum lipids consisted mainly of oleic acid (40.5%), linoleic acid (10%), and octadecynoic (15.8%). This is the first report on the fatty acid composition of P. polycephalum microplasmodia. These results suggest that the biomass of microplasmodia could be used as a source of material for direct conversion into biodiesel because of the absence of cell walls or it could also be used as a supplemental source of beneficial fatty acids for humans, albeit with some further evaluation needed.     

黏菌学的发展

黏菌是一类在陆地生态系统中广泛分布的真核生物,在其生活史的不同阶段,既有体现原生动物运动性的营养体,也具有高度特异化的繁殖体,其形态结构与生理特征,兼具了“菌物”与“动物”的特性,独特的进化地位以及与环境、人类健康的密切关系,使得以黏菌为模式生物的研究在生物学、遗传学、生理学、生态学、信息科学等学科均具有广泛的科学意义和重要的应用价值。自17世纪以来,黏菌研究者们从早期的经典分类学,逐步拓展到从生物学各分支学科领域系统全面地认识黏菌类群。在近几十年中,黏菌研究在系统学、生物学、生态学等方向取得了长足的进步。本文扼要介绍了黏菌学在各领域内的代表性研究进展和前沿性科学问题,同时对相关领域未来的发展进行了展望。     

煤污病菌表皮生态位适应性进化机制研究进展

煤污病是一类外寄生性植物真菌病害。煤污病菌在果实表面形成黑色污斑和污点,导致外观品质降低影响销售,给果农造成严重经济损失。真菌的适应性进化分子机制一直是植物病原真菌生态学领域的研究前沿。煤污病菌在进化过程中为适应寄主表面营养贫瘠、干旱、紫外线照射等非生物胁迫,以及与表面其他微生物竞争生物胁迫等极端环境,进化出一系列独特机制,从而成功定殖于植物表皮。本文从基因组结构趋同进化、致病相关基因家族收缩与扩张和胁迫响应等方面,系统综述了煤污菌群对表皮生态位的适应性进化分子机制。