单孢节丛孢--中国新记录种

<正>捕食线虫真菌是指以营养菌丝特化形成的捕食器官捕捉线虫的一类真菌,主要包括节丛孢属Arthrobotrys、隔指孢属Dactylella和单顶孢属Monacrosporium等3个属。我国现已报道节丛孢属     

一株自发产生孢子捕食器的捕食线虫真菌——Dactylellina parvicolla WZ27

对云南省大理苍山火烧遗迹地土壤中的捕食线虫真菌资源进行调查过程中,发现一株能自发产生孢子捕食器官的捕食线虫真菌,编号WZ27,经形态和分子鉴定为细颈亚隔指孢Dactylellina parvicolla。该株菌的主要特征为不需要经过任何物质的诱导即可自发产生孢子捕食器,其自发形成孢子捕食器官的百分率达到18.3%,通过线虫与牛粪的诱导,孢子捕食器官的形成明显增加。同时与细颈亚隔指孢D.parvicolla参考菌株相比,捕食器官生成时间要更短(P0.001),且捕食率高于参考菌株(P=0.003)。     

食线虫真菌28S rDNA PCR扩增片段的RFLPs分析*

本文对16个食线虫真菌(节丛孢属、隔指孢属和单顶孢属)菌株和3个其他相关丝孢菌(顶辐孢属和单端孢属)菌株的28S rDNA 片段进行了扩增, 并用限制性内切酶Sau3A I, Msp I, Rsa I and Hae III对PCR产物进行了消化。采用UPGMA法对 PCR 产物的限制性图谱特征进行了聚类分析。结果表明,捕食性真菌的聚类群与捕食器官类型相对应,顶辐孢属和单端孢属与捕食性真菌的遗传距离较远。该结果与rDNA 的ITS区间、5.8S和18S的序列分析结果一致。     

食线虫真菌28S rDNA PCR扩增片段的RFLPs分析

本文对16个食线虫真菌(节丛孢属、隔指孢属和单顶孢属)菌株和3个其他相关丝孢菌(顶辐孢属和单端孢属)菌株的28S rDNA 片段进行了扩增, 并用限制性内切酶Sau3A I, Msp I, Rsa I and Hae III对PCR产物进行了消化。采用UPGMA法对 PCR 产物的限制性图谱特征进行了聚类分析。结果表明,捕食性真菌的聚类群与捕食器官类型相对应,顶辐孢属和单端孢属与捕食性真菌的遗传距离较远。该结果与rDNA 的ITS区间、5.8S和18S的序列分析结果一致。     

捕食线虫真菌少孢节丛孢Arthrobotrys oligospora线粒体基因组的异质性

捕食线虫真菌少孢节丛孢Arthrobotrys oligospora是子囊菌中的一个食肉性丝状真菌,其菌丝体可变态为各种结构精巧的捕食器官用于捕食线虫,在生物防治和进化上极具研究潜力.线粒体基因细胞色素c氧化酶亚基Ⅰ基因(COX1)在真菌物种鉴定中的效果饱受争议.本研究对A.oligospora的不同单孢培养的菌株进行...     

节丛孢属丝孢菌对松材线虫和拟松材线虫的捕食*

利用节丛孢属捕食线虫真菌的 8个种 ,1 1个菌株 ,对松材线虫 (Bx)和拟松材线虫(Bm)进行了捕食力的测定。结果显示节丛孢属真菌对这两种线虫的捕食能力既存在种间差异 ,也存在同种不同菌株间的差异。指状节丛孢的 3个菌株Ad 1 ,Ad 2 ,Ad 3菌株对两种线虫均表现出较高的捕食率 ,接种 7d后对Bx和Bm的捕食率分别达到了 98.08%,91.16 %,86.3 %和 96.28%,90.45 %,85.38%;同一菌株对松材线虫和拟松材线虫的捕食没有选择性。此外 ,通过对松材线虫和拟松材线虫     

食线虫真菌致病相关丝氨酸蛋白酶的研究进展

食线虫真菌是一类土壤微生物,作为线虫的天敌,它们对于维持线虫在土壤生态环境中的种群动态平衡发挥着十分重要的作用。食线虫真菌通过形成特殊的捕食器官或产生毒素等方式来捕捉和杀死线虫。丝氨酸蛋白酶是食线虫真菌侵染线虫的重要毒力因子,近年来,研究人员对不同食线虫真菌来源的致病相关丝氨酸蛋白酶进行了大量的研究,尤其在丝氨酸蛋白酶的晶体结构和分子进化方面的研究取得了较大的进展。本文对食线虫真菌致病相关丝氨酸蛋白酶的生物化学性质和功能进行了系统的总结,对丝氨酸蛋白酶的晶体结构、催化机制及分子进化等最新的进展进行了评述。     

食线虫真菌资源研究概况

食线虫真菌是指寄生、捕捉、定殖和毒害线虫的一类真菌,这类真菌是自然界中线虫种群控制的重要因子,也是动植物病害生物防治的重要研究材料,具有特殊的研究意义和经济价值。目前全世界共报道700余种食线虫真菌,包括捕食线虫真菌380余种,线虫内寄生真菌120余种,产毒真菌270余种和大量机会真菌。针对丰富的食线虫真菌资源,近年来世界各国尤其是中国科学家对其进行了广泛研究,在捕食线虫真菌资源的分类、系统进化、生态分布、有性无性联系等方面的研究取得了重要进展,在线虫内寄生真菌侵染宿主的方式及产毒真菌的次生代谢产物挖掘等方面也进行了广泛研究,文章综述了以上研究进展并简述了食线虫真菌资源的生物防治应用概况。     

圆盘菌科真菌及其无性型的研究*

圆盘菌科Orbiliaceae真菌是小型盘菌,由于不清楚其经济价值,人们一直认为它是个不重要的类群,很少有人进行过研究(Alexopoulos et al.,1996)。Pfister(1994)报道粪生圆盘菌Orbilia fimicola Jeng & Krug是捕食线虫丝孢菌节丛孢属Arthrobotrys的有性型,从而引起真菌学家们的关注。捕食线虫丝孢菌以其巧妙的菌丝变态器官捕食线虫,长期以来一直吸引着众多真菌学家的注意,进行了广泛的研究。在分类学方面,捕食线虫丝孢菌分类的主要依据靠分生孢子的形态,没有真正体现出其自然发育的亲缘关系(Hagedorn & Scholler, 1999)。圆盘菌属Orbilia F…     

食线虫真菌28S rDNA PCR扩增片段的RFLPs分析

本文对16个食线虫真菌（节丛孢属,隔指孢属和单顶孢属）菌株和3个其他相关丝孢菌（顶辐孢属和单端孢属）菌株的28S rDNA片段进行了扩增,并用限制性内切酶Sau3 A,I,Msp I,RsaIand HaeⅢ对PCR产物进行了消化,采用UPGMA法对PCR产物的限制性图谱特征进行了聚类分析。结果表明,捕食性真菌的聚类群与捕食器官类型相对应,顶辐孢属和单端孢属与捕食性真菌的遗传距离较远。该结果与rDNA的ITS区间,5．8S和18S的序列分析结果一致。     

Incorporating Genomics into the Toolkit of Nematology

The study of nematode genomes over the last three decades has relied heavily on the model organism Caenorhabditis elegans, which remains the best-assembled and annotated metazoan genome. This is now changing as a rapidly expanding number of nematodes of medical and economic importance have been sequenced in recent years. The advent of sequencing technologies to achieve the equivalent of the $1000 human genome promises that every nematode genome of interest will eventually be sequenced at a reasonable cost. As the sequencing of species spanning the nematode phylum becomes a routine part of characterizing nematodes, the comparative approach and the increasing use of ecological context will help us to further understand the evolution and functional specializations of any given species by comparing its genome to that of other closely and more distantly related nematodes. We review the current state of nematode genomics and discuss some of the highlights that these genomes have revealed and the trend and benefits of ecological genomics, emphasizing the potential for new genomes and the exciting opportunities this provides for nematological studies.     

The multimeric beta-thymosin found in nematodes and arthropods is not a synapomorphy of the Ecdysozoa

The Ecdysozoa hypothesis proposes a clade of animals including arthropods and nematodes that share the characteristic of periodic molting or ecdysis. The original evidence supporting this hypothesis came from molecular phylogenies based on ribosomal RNA gene sequences. Contrary evidence has come from studies of multiple protein coding genes. One of the most convincing bits of supporting evidence for this theory has been the observation of an unusual multimeric form of the beta-thymosin gene in the genomes of Drosophila melanogaster and Caenorhabditis elegans where, in other metazoans that had been studied, a monomeric form has been found. Here I show that recently deposited sequence data reveal that the multimeric form is in fact a characteristic of all major subdivisions of the Metazoa. The multimeric form is present in a deuterostome, Ciona intestinalis, a lophotrochozoan, Hermissenda crassicornis, and in the ecdysozoans and also exists outside the Metazoa in a fungus. The presence of the multimeric form in nematodes and arthropods, therefore, although not contradicting the Ecdysozoa hypothesis, gives it no support. The absence of the monomeric form in the completely sequenced flies and nematodes may suggest they are linked but, lacking the complete genomes of other ecdysozoans, proving its total absence from the Ecdysozoa is not possible. Furthermore, the absence of the monomeric form from the genome of the deuterostome Ciona suggests that the absence of this character is an unreliable indicator of relationships.     

Mitochondrial genomes of parasitic nematodes--progress and perspectives

Mitochondria are subcellular organelles in which oxidative phosphorylation and other important biochemical functions take place within the cell. Within these organelles is a mitochondrial (mt) genome, which is distinct from, but cooperates with, the nuclear genome of the cell. Studying mt genomes has implications for various fundamental areas, including mt biochemistry, physiology and molecular biology. Importantly, the mt genome is a rich source of markers for population genetic and systematic studies. To date, more than 696 mt genomes have been sequenced for a range of metazoan organisms. However, few of these are from parasitic nematodes, despite their socioeconomic importance and the need for fundamental investigations into areas such as nematode genetics, systematics and ecology. In this article, we review knowledge and recent progress in mt genomics of parasitic nematodes, summarize applications of mt gene markers to the study of population genetics, systematics, epidemiology and evolution of key nematodes, and highlight some prospects and opportunities for future research.     

Phylogenetic relationships of the Wolbachia of nematodes and arthropods

Wolbachia are well known as bacterial symbionts of arthropods, where they are reproductive parasites, but have also been described from nematode hosts, where the symbiotic interaction has features of mutualism. The majority of arthropod Wolbachia belong to clades A and B, while nematode Wolbachia mostly belong to clades C and D, but these relationships have been based on analysis of a small number of genes. To investigate the evolution and relationships of Wolbachia symbionts we have sequenced over 70 kb of the genome of wOvo, a Wolbachia from the human-parasitic nematode Onchocerca volvulus, and compared the genes identified to orthologues in other sequenced Wolbachia genomes. In comparisons of conserved local synteny, we find that wBm, from the nematode Brugia malayi, and wMel, from Drosophila melanogaster, are more similar to each other than either is to wOvo. Phylogenetic analysis of the protein-coding and ribosomal RNA genes on the sequenced fragments supports reciprocal monophyly of nematode and arthropod Wolbachia. The nematode Wolbachia did not arise from within the A clade of arthropod Wolbachia, and the root of the Wolbachia clade lies between the nematode and arthropod symbionts. Using the wOvo sequence, we identified a lateral transfer event whereby segments of the Wolbachia genome were inserted into the Onchocerca nuclear genome. This event predated the separation of the human parasite O. volvulus from its cattle-parasitic sister species, O. ochengi. The long association between filarial nematodes and Wolbachia symbionts may permit more frequent genetic exchange between their genomes.     

The evolutionary position of nematodes

Background  

The complete genomes of three animals have been sequenced by global research efforts: a nematode worm (Caenorhabditis elegans), an insect (Drosophila melanogaster), and a vertebrate (Homo sapiens). Remarkably, their relationships have yet to be clarified. The confusion concerns the enigmatic position of nematodes. Traditionally, nematodes have occupied a basal position, in part because they lack a true body cavity. However, the leading hypothesis now joins nematodes with arthropods in a molting clade, Ecdysozoa, based on data from several genes.     

Mitochondrial genome diversity in parasites

Mitochondrial genomes have been sequenced from a wide variety of organisms, including an increasing number of parasites. They maintain some characteristics in common across the spectrum of life-a common core of genes related to mitochondrial respiration being most prominent-but have also developed a great diversity of gene content, organisation, and expression machineries. The characteristics of mitochondrial genomes vary widely among the different groups of protozoan parasites, from the minute genomes of the apicomplexans to amoebae with 20 times as many genes. Kinetoplastid protozoa have a similar number of genes to metazoans, but the details of gene organisation and expression in kinetoplastids require extraordinary mechanisms. Mitochondrial genes in nematodes and trematodes appear quite sedate in comparison, but a closer look shows a strong tendency to unusual tRNA structure and alternative initiation codons among these groups. Mitochondrial genes are increasingly coming into play as aids to phylogenetic and epidemiologic analyses, and mitochondrial functions are being recognised as potential drug targets. In addition, examination of mitochondrial genomes is producing further insights into the diversity of the wide-ranging group of organisms comprising the general category of parasites.     

Bacterial symbionts in insects: balancing life and death

Arthropods, particularly insects, form successful long-term symbioses with endosymbiotic bacteria. The associations between insects and endosymbionts are remarkably stable; many stretch back several hundred million years in evolutionary time. With the exception, perhaps, of the filarial nematodes no other group of metazoans shows such a proclivility for their intracellular symbionts. The identification and classification of bacterial symbionts and hosts has grown rapidly over the last two decades and these relationships form a continuum from classical mutualism to parasitism. Complete genomes have been sequenced for many of these bacteria and some of their hosts. Now more intractable questions regarding endosymbiosis are being addressed. Investigations on the role of the host immune system in the maintenance of symbiosis, the nature of bacteriophages and transposable elements found in the genomes of many bacterial symbionts, and the molecular mechanisms involved in establishing reproductive phenotypes such as parthenogenesis, male killing, cytoplasmic incompatibility and feminization have been recently reported. This review will focus on the impact of the secondary endosymbionts Wolbachia, Cardinium, and Spiroplasma on host fitness and immunity and will revisit the question of whether these bacteria are friend or foe from an insect’s point of view.     

The effects of dsRNA mycoviruses on growth and murine virulence of Aspergillus fumigatus

Some isolates of the opportunistic human pathogenic fungus Aspergillus fumigatus are known to be infected with mycoviruses. The dsRNA genomes of two of these mycoviruses, which include a chrysovirus and a partitivirus, have been completely sequenced and an RT-PCR assay for the viruses has been developed. Through curing virus-infected A. fumigatus isolates by cycloheximide treatment and transfecting virus-free isolates with purified virus, as checked by RT-PCR, isogenic virus-free and virus-infected lines of the fungus were generated whose phenotypes and growth have been directly compared. Mycovirus infection of A. fumigatus with either the chrysovirus or the partitivirus resulted in significant aberrant phenotypic alterations and attenuation of growth of the fungus but had no effect on susceptibility to common antifungals. Chrysovirus infection of A. fumigatus caused no significant alterations to murine pathogenicity.