RNA editing of 10 Didymium iridis mitochondrial genes and comparison with the homologous genes in Physarum polycephalum

Regions of the Didymium iridis mitochondrial genome were identified with similarity to typical mitochondrial genes; however, these regions contained numerous stop codons. We used RT-PCR and DNA sequencing to determine whether, through RNA editing, these regions were transcribed into mRNAs that could encode functional proteins. Ten putative gene regions were examined: atp1, atp6, atp8, atp9, cox1, cox2, cytb, nad4L, nad6, and nad7. The cDNA sequences of each gene could encode a functional mitochondrial protein that was highly conserved compared with homologous genes. The type of editing events and editing sequence features were very similar to those observed in the homologous genes of Physarum polycephalum, though the actual editing locations showed a variable degree of conservation. Edited sites were compared with encoded sites in D. iridis and P. polycephalum for all 10 genes. Edited sequence for a portion of the cox1 gene was available for six myxomycetes, which, when compared, showed a high degree of conservation at the protein level. Different types of editing events showed varying degrees of site conservation with C-to-U base changes being the least conserved. Several aspects of single C insertion editing events led to the preferential creation of hydrophobic amino acid codons that may help to minimize adverse effects on the resulting protein structure.     

Centriole maturation in the amoebae ofPhysarum polycephalum

Summary The precise geometry of pro-centriole formation has been studied inPhysarum polycephalum amoebae. The spatial references used were the posterior and the anterior kinetosomes which are unequivocally defined by the presence of the posterior para-kinetosomal structure, the microtubular array 4 and the microtubular arrays 1, 2, and 3. The observations made suggest that pro-centrioles follow a maturation process. A pro-centriole formed during the n^th cell cycle becomes the posterior kinetosome during the (n + 1)^th cell cycle and the anterior one during all the following cell cycles. Pro-centriole formation occurs late in the cell cycle. This observation disagrees with a role of pro-centriole formation in the regulation of S phase in contrast to what has been suggested in other eucaryotic cells.     

Ultrastructural events and kinetics of microcyst germination in the myxomycete Didymium iridis

Microcysts of the myxomycete Didymium iridis were induced to excyst by transfer to 5mM potassium phosphate buffer. After 1 h in suspension, 90% of the microcysts had germinated into myxamoebae distinguishable by phase contrast microscopy and staining with Lugol's iodine. Both pH and osmolarity affected the kinetics of excystment. The rate and extent of excystment were decreased by cycloheximide but remained unaffected by actinomycin D, suggesting a requirement for protein synthesis but not RNA synthesis. Initially, the outer wall layers separated from the inner layer, which gradually expanded and loosened. The protoplast rehydrated and reverted to a vegetative morphology. Excysting cells were characterized by nucleolar inclusions, changes in the nuclear envelope and plasma membrane, appearance of ringed cisternal elements and microbodies in the cytoplasm, and formation of a densely fibrous zone adjacent to the site of emergence. Excysting populations have been classified into characteristic stages: mature, initiated, swollen, and pre-emergent microcysts.Florida Agricultural Experiment Station Journal Series No. 2407     

中国粘菌Ⅷ.中国新纪录属贫丝菌属Oligonema及其新种:膨丝贫丝菌O.oedonema

贫丝菌属Oligonema是由Rostafinski在1875年建立的,至今仅承认4个种,中国前此尚无记载。作者在长白山采到的这份标本,孢丝极少且短小,中部膨肿,有不甚清晰的螺纹带,具贫丝菌的特征,与已知的种明显不同,因此确认为本属的新成员,定名为膨丝贫丝菌O. oedonema,主模式保存在中国科学院微生物研究所真菌标本室。     

中国粘菌IX:团毛菌属(Trichia)一新种

本文报告了粘菌一新种,分枝团毛菌Trichia ramosa Y. Li et H: z. Li sp nov.文中对该新种作了拉丁文描述,讨论了新种与本属近似种的区别,并附有显微照片和绘图。模式标本保存在中国科学院微生物研究所真菌标本室。     

Foraging strategies of the acellular slime moulds Didymium iridis and Didymium bahiense

Organisms can increase their foraging efficiency by modifying their behaviour according to information about the quality of currently exploited resource patches. Here we examine the effect of food concentration on the foraging strategies of two previously unstudied species of slime mould: Didymium iridis and Didymium bahiense. We studied two main foraging decisions: how long to wait before commencing exploration of the surrounding environment (exploitation strategy) and how intensely to search the environment for new opportunities (exploration strategy). Food concentration did not affect exploitation behaviour in either D. iridis or D. bahiense. Food concentration did affect exploration behaviour in D. iridis, but not in D. bahiense. Encounters with food resources, irrespective of concentration, resulted in increased exploitation and decreased exploration in D. iridis but did not influence foraging behaviour in D. bahiense. We suggest that the varying foraging strategies of slime moulds may have evolved to exploit different resource distributions in their natural environments. We also discuss the potential impact of microbial contamination and differences in handling regimes.     

小绒泡菌生活史及其形态建成期显微结构的观察

在完成小绒泡菌Physaum pusillum生活史的同时,观察了小绒泡菌P. pusillum生活史不同阶段显微结构的形成。生活史研究结果表明：小绒泡菌P. pusillum的孢子萌发方式为裂式,黏变形体具两根鞭毛,较短一根不易观察到,原质团类型为显型原质团,子实体形态建成过程约需12-13h。显微结构观察结果表明：石灰结和孢丝结构在原质团隆起约6h后开始形成,孢子在原质团隆起约9h后开始形成,石灰结和孢丝先于孢子形成。     

煤绒菌Fuligo septica显型原质团细胞核及菌核的超微结构

从煤绒菌显型原质团中提纯细胞核、核仁,诱导原质团形成菌核,并在透射电镜下观察。研究结果表明:细胞核具有中央核仁,核仁可以看到明显的纤维中心、致密纤维中心和颗粒结构。原质团中存在大量的黏液颗粒。菌核具有双层膜,内含有细胞器及脂滴。     

TAXONOMIC STUDIES ON PHYSARUM FROM CHINA I. THREE NEW SPECIES FROM NORTHEASTERN CHINA

在近年来对中国绒泡菌属粘菌的分类学研究中,观察到许多不寻常和有趣的标本,其中一些与目前已知的绒泡菌均不吻合,形态学研究表明它们是新种。本文报告了３个产自我国东北的绒泡菌属新种,它们是：产自吉林省的环柄绒泡菌Ｐｈｙｓａｒｕｍａｎｎｕｌｉｐｅｓ和青灰绒泡菌Ｐｈｙｓａｒｕｍｃａｅｓｉｕｍ及产自内蒙古自治区的木生绒泡菌Ｐｈｙｓａｒｕｍｘｙｌｏｐｈｉｌｕｍ。环柄绒泡菌的孢囊柄具有环带,较为特殊;青灰绒泡菌的囊被有一粉状物质层,但其中的钙含量远低于其它大多数绒泡菌;木生绒泡菌的球形白色的孢囊有柄、群生、直立,具纵皱的柄褐色而不透明,囊基盘状,石灰结较小、多角形或伸长,孢子匀生小疣但一侧色浅。文中对它们进行了形态学描述和讨论,并附有扫描电镜下的特征照片,模式标本保存在中国科学院微生物研究所真菌标本室（ＨＭＡＳ）。     

中国西藏黏菌记录(英文)

报道和记录了中国西藏的黏菌75种1变种。研究标本中,225份由第一作者采自西藏的林芝(八一和鲁朗)、波密和米林,37份来自于树皮基物的湿室培养,8份保存于中国科学院菌物标本馆,26份保存于中国科学院昆明植物研究所隐花植物标本馆。通过对这些标本的鉴定和复核,明确了52种1变种为西藏新记录种,叶生钙丝菌Badhamia foliicola和齿孢团毛菌Trichia crenulata为中国新记录种。