绿草履虫-小球藻共生系统中共生藻对宿主细胞超微结构的影响

应用透射电镜术显示了含小球藻绿草履虫和人工诱导获得的无小球藻绿草履虫细胞的超微结构特征,无小球藻绿草履虫细胞内有大量处于不同消化阶段的食物泡及膜性小泡,在细胞质内常见有线粒体聚集分布以及内质网分布其中,细胞大核内核仁数目增多,并聚集形成多个核仁区。含小球藻绿草履虫中细胞膜性结构较少见,细胞大核中核仁数目较少。结果表明,小球藻共生体可能影响了宿主草履虫细胞中所述细胞器的功能,数量和分布,并影响了核仁的功能,数量和分布。     

草履虫的有性生殖

以尾草履虫的接合生殖为主叙述了草履虫有性生殖期间核及皮层胞器更替的细节,并指出它与多细胞动物有性生殖的相似性不同点。相似性在不同是通过受精作用建造下一代新个体的过程;不同点是履虫没有亲子两代并存的时期。     

草履虫的核和生殖

草履虫有两种核,即大核和小核,小核是二倍体,含 DNA 而不含 RNA,它参与有性生殖过程,具有传递遗传信息的功能,但不为蛋白质合成提供模板,因此它不产生RNA。大该为多倍体,既含 DNA 又含 RNA,因为大核是由小核形成的(有性生殖时,大核消失,并被合子的小核形成的一个新大核所代替),所以它不能携带比小核更多的基因信息,然而它含有更多的 DNA,至少是小核的8倍,大核中的 RNA 能为蛋白质的合成提供模板。草履虫借无性生殖(二裂法)和有性生殖(接合法)进行生殖,无性生殖时,小核     

含小球藻和无小球藻绿草履虫的基因组DNA多态性的研究

以“绿草履虫－小球藻”共生系统为材料,选用２０种随机引物对光培养下含小球藻共生体的草履虫和暗培养诱导除去小球藻共生体的草履虫基因组ＤＮＡ进行遗传多态分析,由扩增产物电泳图谱显示,用Ｓ４０１、Ｓ１４７、Ｓ７８６、Ｓ７５９、Ｓ８６、Ｓ１５５、Ｓ１４０等随机引物扩增出８６６、１３９３、１６３７ｂｐ等具有相同特征的电泳条带;随机引物Ｓ１７４、Ｓ７５０、Ｓ７５５、Ｓ１０３等则扩增出１３８５、１８５２、１５７     

共生小球藻对宿主绿草履虫形态、生长、抗氧化能力及细胞质糖含量的影响

以含共生藻绿草履虫 (CCP)、恢复型绿草履虫 (RCCP)和无共生藻绿草履虫 (CFP)为材料 ,探讨共生体对宿主生长、细胞大小、抗氧化能力和细胞质糖含量的影响。 3种细胞培养液中 ,细胞培养密度峰值分别为 15 0 0、 80 0和 5 0 0个 /mL ,对应的生长峰值期分别在第 14天、第 14天和第 8天。CCP细胞比CFP约长 2 2μm ,约宽 16 μm ;RCCP在CCP和CFP之间。对邻苯三酚自氧化产生O2 化学发光的抑制效果不同 :随匀浆液浓度 (μL/mL)从 2 0增加到 10 0时 ,CCP抑制率提高了 6 7% ,RCCP提高了 4 2 % ,而CFP和小球藻仅分别为 2 7%和<10 %。细胞质葡萄糖和麦芽糖含量差异巨大 :CCP分别为RCCP的 4和 2倍 ,而CFP是RCCP的 1/ 4和 1/ 2。看来 ,绿草履虫在这个共生系统中受益。     

免疫荧光染色揭示草履虫接合生殖过程中静止原核的空间位置(英文)

在尾草履虫的接合生殖过程中,共有三次配前核分裂。在配前第三次分裂结束后,两个接合的细胞内均形成一个迁移原核和一个静止原核。迁移原核位于口旁锥内,而且紧贴于接合面,静止原核则位于迁移原核的外侧,两者呈左右排列,距离接近。但是,目前对导致两种原核近距离的原因尚不清楚。该文通过α-微管蛋白的单克隆抗体对受精核形成前的接合对进行了免疫荧光染色,结果发现,配前第三次分裂不同于前两次分裂,连接迁移原核和静止原核的核间连丝伸向细胞的后方,呈"U"或"V"型,结果导致两个原核左右排列,而不是前后排列,两者间的距离缩短。这个结果也阐明了造成两种原核近距离的原因。     

第四双小核草履虫减数分裂产物的退化特征分析

通过吖啶橙和Hoechst 33342两种活体荧光染料双染的方法对第四双小核草履虫(Paramecium tetraurelia)接合生殖过程中小核减数分裂产物进行观察,结果发现位于口旁锥外的小核分裂产物呈蓝绿色或黄绿色,表明它们以凋亡的方式发生退化.     

不同染色方法揭示纤毛原生动物草履虫接合生殖过程的新细节

通过石炭酸品红、Hoechst 33342、蛋白银及免疫荧光标记等染色方法对草履虫接合生殖过程进行了重新观察,结果发现:1)新月核是第一次减数分裂前期小核的主要形态学特征,在核内有一未被石炭酸品红、Hoechst 33342着色区域,蛋白银染色则清楚显示该结构;2)4个单倍体减数分裂产物中的1个核进入口旁锥完成配前第三次核分裂,其余3核退化.蛋白银染色和抗α微管蛋白单克隆抗体进行免疫荧光标记显示,核进入口旁锥的时期在第二次减数分裂末期而非减数分裂结束后;3)配前第三次分裂末期,核间连丝的中间段有一被蛋白银识别的结构,但免疫荧光标记却无显示,只表现为纤维状结构与两侧核间连丝相连.观察结果为草履虫接合生殖过程中相关分子生物学机制研究奠定了必要的形态学基础.     

纤毛虫与藻类共生关系的研究现状与展望

纤毛虫与藻类的共生关系在水体环境中广泛存在并有着重要的生态功能。文章回顾了国内外纤毛虫与藻类共生研究的发展历程,主要介绍了纤毛虫与藻类共生的生态功能,以及显微观察与分子生物学技术在纤毛虫与藻类共生研究中的应用;阐述了包括草履虫与小球藻共生关系建立的4个过程及其互作机制、红色中缢虫与隐藻的共生关系、宿主与共生体之间的互作等内容;提出了纤毛虫与藻类共生研究中亟待解决的科学问题,包括草履虫食物泡膜(digestive vacuole, DV)与围藻膜(perialgal vacuole, PV)发挥作用的分子机制、红色中缢虫与隐藻共生关系的建立过程、红色中缢虫在共生过程中的功能作用等,并展望未来的研究方向。     

Association of Paramecium bursaria Chlorella viruses with Paramecium bursaria cells: ultrastructural studies

Paramecium bursaria Chlorella viruses were observed by applying transmission electron microscopy in the native symbiotic system Paramecium bursaria (Ciliophora, Oligohymenophorea) and the green algae Chlorella (Chlorellaceae, Trebouxiophyceae). Virus particles were abundant and localized in the ciliary pits of the cortex and in the buccal cavity of P. bursaria. This was shown for two types of the symbiotic systems associated with two types of Chlorella viruses - Pbi or NC64A. A novel quantitative stereological approach was applied to test whether virus particles were distributed randomly on the Paramecium surface or preferentially occupied certain zones. The ability of the virus to form an association with the ciliate was investigated experimentally; virus particles were mixed with P. bursaria or with symbiont-free species P. caudatum. Our results confirmed that in the freshwater ecosystems two types of P. bursaria -Chlorella symbiotic systems exist, those without Chlorella viruses and those associated with a large amount of the viruses. The fate of Chlorella virus particles at the Paramecium surface was determined based on obtained statistical data and taking into account ciliate feeding currents and cortical reorganization during cell division. A life cycle of the viruses in the complete symbiotic system is proposed.     

Mechanism of Photoaccumulation in Paramecium bursaria

Responses of Paramecium bursaria to light intensity changes were investigated. The resting paramecia show a direction changing response (photophobic response) to a sudden decrease of light intensity, whereas no response was shown to an increase in intensity. The critical intensity decrease dI_c necessary to show the response was measured at various values of initial light intensity, and the ratio dI_c/I was found to be equal to ～0.15. The swimming paramecia show different behavior depending on their swimming direction in the spatial gradient of light intensity. Paramecia show direction change more frequently when they are swimming down the gradient than in the opposite direction. This difference in the rate of direction changing is 13–17%. These results may offer an explanation for the mechanism of photoaccumulation.     

Intracellular digestion and symbiosis in Paramecium bursaria

Electron microscopic cytochemical methods reveal that acid phosphatase activity appears exclusively in vacuoles containing recently ingested bacteria or inert particles such as carmine, Celkate or latex spheres, and not in the vacuoles surrounding established symbionts. Although newly ingested symbiotic algae are digested in large numbers, some remain to reestablish the symbiosis. Since symbiotic algae are able to delay the digestion of heat-killed algae when they coexist in a phagosome, we propose that symbiotic Chlorella actively interfere with an early event in the host digestive process.