原虫的蛋白质组学研究进展

随着“人类基因组计划”的完成,包括双向电泳和质谱技术的蛋白质组学作为基因组学研究的补充和终点,不断增加我们对基因功能的理解,逐渐成为医学研究的中心。原虫作为医学研究的对象和工具,研究内容十分广泛。本文将从原虫生活史、致病机理、潜在疫苗以及抗药性等方面对原虫的蛋白质组学进行综述。     

Protozoan communities around conifer roots colonized by ectomycorrhizal fungi

Protozoan communities around roots with different types of ectomycorrhizae were distinct. These protozoan communities differed both qualitatively and quantitatively with the host (Pinus ponderosa, Pseudotsuga menziesii, Picea sitchensis, Tsuga heterophylla and Abies grandis) and the ectomycorrhizal fungal species. Based on the species identified and the numbers of individuals of each species, six communities of protozoa were found associated with specific ectomycorrhizae. Previous researchers have shown that mycorrhizal colonization of roots alters the amounts and types of exudates produced by roots, which in turn alters the bacterial community present. Most likely, mycorrhizal colonization of roots influences the protozoan community around roots by controlling the bacterial community. However, the protozoan community may in turn influence the successional dynamics of ectomycorrhizal fungi on different host root systems by a variety of mechanisms. These mechanisms could include: (1) preying upon individuals and perhaps removing particular species of bacteria from the mycorrhizosphere; and (2) controlling nitrogen mineralization in the rhizosphere. Further work needs to be performed to determine the interaction between these quadrate (plant-bacteria-fungi-protozoa) associations.     

Protozoan communities of the Flint River-Lake Blackshear ecosystem (Georgia,USA)

Freshwater protozoa are poorly characterized in river ecosystems. We report here the richness of the protozoan biotas in relation to environmental gradients from an ecosystematic survey of a large, coastal plain river. Communities were collected from natural and artificial substrates concurrent with water chemistry analysis at 11 sites along the Flint River and Lake Blackshear impoundment. Community similarity, the distribution of collected taxa in functional feeding groups, and the relation of communities to environmental gradients were evaluated. Two principal compenents determined from water chemistry data showed important downstream gradients of decreasing water hardness and increasing nutrient levels. Taxonomic richness was high; 200 to 450 taxa were collected depending on season and collecting technique. Artificial substrates provided the richest collections. Bactivorous species were the vast majority of all taxa collected. Community composition showed an orderly transition from upstream to downstream, and photosynthetic forms were enhanced at nutrient enriched sites. Communities were strongly influenced by increasing nutrient levels. Protozoan community analysis showed that microbial community composition reflects human influences on river ecosystems. Since microbial species exploit detrital resources and respond sensitively to human influences, they can provide important information regarding ecosystem conditions.     

Biomass and Functional Distribution According to the Feeding Modes of Two Freshwater Protozoan Communities

The study has been made concerning the composition of and the relationships among: physico-chemical factors, abundance, number of species, biomass, heterotrophic and photoautotrophic components, and functional groups with regard to the feeding patterns of a river-reservoir system. The most outstanding results concerning the system as a whole are: 1, a relationship exists between the biomass of protozoa and the biomass of ciliates; 2, the most important functional groups, in terms of the number of species, are group III (ciliate “downstream” filter feeders) and group IV (ciliate “upxtream” filter feeders), and in terms of the abundance of specimens, the most important ones are groups III and V (raptorial feeders); 3, the division into functional groups according to feeding modes is similar in the river and the reservoir studied. This correlation is quite significant with regard to the number of species, the abundance of specimens, and between the samples taken from the two areas.     

贵州晚新元古代陡山沱磷块岩中疑似磷酸盐化原生动物化石

发现于贵州省瓮安和福泉县晚新元古代陡山沱期磷块岩中的一组可疑的磷酸盐化原生动物化石,暂定为1新属——侧孔虫(Luxapertus gen．nov．)。单房室壳体,卵形、球形及椭球形,磷酸盐化外壁1—2层,房室内分布磷酸盐化微粒和原生质(?)残留物分布不均匀形成各种不规则斑纹。壳体前方一侧发育内口管的管状或乳头状口孔,管状口孔有清晰的丝状伪足伸出,其前端或壳体后方附有一团原生质(?)残留物。上述特征表明这一类化石与有孔虫(Foraminifera)似有明显的亲缘关系。根据标本的形态特征和口孔性质,本文初步记述了这批材料中的瓮安侧孔虫(Luxapertus wenganensis gen．et sp．nov．)、球形侧孔虫(Luxapertus sphaeroidolis gen．et sp．nov．)和乳头侧孔虫(Luxapertus papillaformis gen．et sp．nov．)等三种侧孔虫新种,疑为地球早期原生动物的代表。这一发现丰富了瓮安生物群的内容,证明瓮安生物群中确有可疑的原生动物化石存在。一般认为有孔虫在寒武纪开始出现。瓮安生物群中可疑的有孔虫类的发现,使有孔虫首次出现的记录大大提前。     

A Newly Revised Classification of the Protozoa*

SYNOPSIS The subkingdom Protozoa now includes over 65,000 named species, of which over half are fossil and ～ 10,000 are parasitic. Among living species, this includes ～ 250 parasitic and 11,300 free-living sarcodines (of which ～ 4,600 are foraminiferids); 1.800 parasitic and 5,100 free-living flagellates: ～ 5,600 parasitic “Sporozoa” (including Apicomplexa, Microspora, Myxospora, and Aseetospora); and ～ 2,500 parasitic and 4,700 free-living ciliates. There are undoubtedly thousands more still unmamed. Seven phyla of PROTOZOA are accepted in this classification—SARCOMASTIGOPHORA. LABYRINTHOMORPHA, APICOMPLEXA, MICROSPORA, ASCETOSPORA, MYXOSPORA, and CILIOPHORA. Diagnoses are given for these and for all higher taxa through suborders, and representative genera of each are named. the present scheme is a considerable revision of the Society's 1964 classification, which was prepared at a time when perhaps 48,000 species had been named. It has been necessitated by the acquisition of a great deal of new taxonomic information, much of it through electron microscopy. It is hoped that the present classification incorporates most of the major changes that will be made for some time. and that it will be used for many years by both protozoologists and non-protozoologists.     

Pseudomonocystis sp., an Eugregarine Protozoan Pathogen of the Coconut Root Grub, Leucopholis coneophora

Populations of the coconut root grub , Leucopholis coneophora, were infected by an eugre garine protozoan pathogen , Pseudomonocystis sp . The pathogen infected 22.7% third - instar L. coneophora larvae in the field . The infected larvae produced 1 - 84 (average 37 . 11) milky - white , membranous , elliptical cysts measuring 2 . 64 1 . 24 mm . Each cyst contained about 3 . 80 105 mucilaginous spores . The spores were elliptical with two tubular polar caps , thick - walled , ornamented with irregular ridges and furrows , and measured 26 . 04 13 . 61 mum . The LD and LT for oral inoculation of spores into third - instar larvae were 9 . 86 104 50 50 spores / larva and 27 . 62 days respectively . Ingestion of spores with or without food and connibalism of infected larvae were the modes of transmission of the pathogen .     

Sorosphaerula nom. n. for the plasmodiophorid genus Sorosphaera J. Schröter 1886 (Rhizaria: Endomyxa: Phytomyxea: Plasmodiophorida)

ABSTRACT. Sorosphaerula nom. n. is introduced to replace the phytomyxean generic name Sorosphaera J. Schröter, which is preoccupied by the foraminiferan genus Sorosphaera Brady. As it is agreed now that both the Foraminifera and the Phytomyxea belong to the Rhizaria, this homonomy within the same supergroup of eukaryotes needs to be revised. To avoid future homonomy, we recommend that the International Code of Zoological Nomenclature be applied for future taxonomic work on Phytomyxea.     

Protozoan and intracellular fungal gut endosymbionts in Drosophila: prevalence and fitness effects of single and dual infections

We report on the effect of single and mixed infections with two gut symbionts, trypanosomatids and the intracellular fungus Coccidiascus legeri, on the life history of their host, Drosophila melanogaster. We also provide the first report on the prevalence of C. legeri in natural populations of Drosophila. Prevalence overall was low (3.4%), and differed with host species, but persisted from the first to the second year of our survey. We documented delayed pupation in flies exposed to trypanosomatids, but larvae exposed to the fungus eclosed more quickly than controls. Larvae exposed to mixed infections pupated more slowly, but eclosed more quickly than controls.     

Salivary gland of the tick vector of East Coast fever. III. The ultrastructure of sporogony in Theileria parva

Sporogony of the sporozoan Theileria parva in the salivary gland of the tick vector of East Coast fever was studied in electron micrographs. The findings differ in several respects from previous interpretations based upon light microscopy. Cytokinesis of the primary sporoblast to form secondary and tertiary sporoblasts is not substantiated. Instead it is suggested that the parasite develops as a ramifying, multinucleate syncytium rapidly increasing in size and complexity until it gives rise to myriad sporozoites in a terminal episode of cytoplasmic fission. The proliferating nuclei initially occupy peripheral lobules that are continuous with a central labyrinth of branching and anastomosing processes which present a very large surface area for interchange of metabolites with the host cell cytoplasm. The membrane of the labyrinth is rich in cytostomes, but no evidence if found to bulk uptake of host cytoplasmic matrix or organelles into food vacuoles. Rhoptries are the first of the polar organelles of the parasite to develop and are associated with dense plaques irregularly distributed on the inner aspect of the parasite membrane. Micronemes form independently of the rhoptries at a later stage. After 3-4 days of tick feeding, sporogeny is complete and the infected salivary gland cell contains up to 50, 000 spherical or ovoid sporozoites about 1 micrometer in diameter. These are limited by a simple plasma membrane. The inner layer of the 'pellicle', the polar ring, and the conoid described for zoites of other Apicomplexa are lacking. Maturational changes are noted in sporozoites after sporogony is completed. Micronemes appear to increase in size, and possibly in number, from days 3-5 and the majority take up positions immediately subjacent to the plasmalemma.     

<Emphasis Type="Italic">Toxoplasma gondii</Emphasis> Expresses Two Mitogen-Activated Protein Kinase Genes That Represent Distinct Protozoan Subfamilies

All eukaryotes express mitogen-activated protein kinases (MAPKs) that govern diverse cellular processes including proliferation, differentiation, and survival. Even though these proteins are highly conserved throughout nature, MAPKs from closely related species often possess distinct signature sequences, making them well suited as drug discovery targets. Based on the central amino acid in the TXY dual phosphorylation loop, mammalian MAPKs are classified as extracellular signal-regulated kinases (ERKs), c-Jun amino-terminal kinases (JNKs), or p38 stress-response MAPKs. The presence of MAPKs in nonmetazoan eukaryotes suggests significant evolutionary conservation of these important signalling pathways. We recently cloned a novel stress-response MAPK gene (tgMAPK1) from Toxoplasma gondii, an obligate intracellular human parasite that can cause life-threatening infections in immunocompromised patients, and we now present data on a second T. gondii MAPK gene (tgMAPK2) that we cloned. We show that tgMAPK1 and tgMAPK2 are members of two distinct and previously unknown protozoan MAPK subfamilies that we have named pzMAPKl/pzMAPK3 and pzMAPK2. Our phylogenetic analysis of a collection of protozoan and metazoan MAPK genes in relation to ERK8-like genes demonstrates that an ERK8-like family, which includes the pzMAPK2 subfamily, is represented across a large variety of eukaryotic kingdoms and is evolutionarily very distant from other MAPK families.     

Acidobacteria Phylum Sequences in Uranium-Contaminated Subsurface Sediments Greatly Expand the Known Diversity within the Phylum

The abundance and composition of bacteria of the phylum Acidobacteria were surveyed in subsurface sediments from uranium-contaminated sites using amplification of 16S rRNA genes followed by clone/sequence analysis. Analysis of sequences from this study and public databases produced a revised and greatly expanded phylogeny of the Acidobacteria phylum consisting of 26 subgroups.     

The diversity of ABC transporter genes across the Phylum Nematoda

It is estimated that one billion people globally are infected by parasitic nematodes, with children, pregnant women, and the elderly particularly susceptible to morbidity from infection. Control methods are limited to de-worming, which is hampered by rapid re-infection and the inevitable development of anthelmintic resistance. One family of proteins that has been implicated in nematode anthelmintic resistance are the ATP binding cassette (ABC) transporters. ABC transporters are characterized by a highly conserved ATP-binding domain and variable transmembrane regions. A growing number of studies have associated ABC transporters in anthelmintic resistance through a protective mechanism of drug efflux. Genetic deletion of P glycoprotein type ABC transporters in Caenorhabditis elegans demonstrated increased sensitivity to anthelmintics, while in the livestock parasite, Haemonchus contortus, anthelmintic use has been shown to increase the expression of ATP transporter genes. These studies as well as others, provide evidence for a potential role of ABC transporters in drug resistance in nematodes. In order to understand more about the family of ABC transporters, we used hidden Markov models to predict ABC transporter proteins from 108 species across the phylum Nematoda and use these data to analyze patterns of diversification and loss in diverse nematode species. We also examined temporal patterns of expression for the ABC transporter family within the filarial nematode Brugia malayi and identify cases of differential expression across diverse life-cycle stages. Taken together, our data provide a comprehensive overview of ABC transporters in diverse nematode species and identify examples of gene loss and diversification in nematodes based on lifestyle and taxonomy.     

Protozoan protein tyrosine phosphatases

The aim of this review is to provide a synthesis of the published experimental data on protein tyrosine phosphatases from parasitic protozoa, in silico analysis based on the availability of completed genomes and to place available data for individual phosphatases from different unicellular parasites into the comparative and evolutionary context. We analysed the complement of protein tyrosine phosphatases (PTP) in several species of unicellular parasites that belong to Apicomplexa (Plasmodium; Cryptosporidium, Babesia, Theileria, and Toxoplasma), kinetoplastids (Leishmania and Trypanosoma spp.), as well as Entamoeba histolytica, Giardia lamblia, Trichomonas vaginalis and a microsporidium Encephalitozoon cuniculi. The analysis shows distinct distribution of the known families of tyrosine phosphatases in different species. Protozoan tyrosine phosphatases show considerable levels of divergence compared with their mammalian homologues, both in terms of sequence similarity between the catalytic domains and the structure of their flanking domains. This potentially makes them suitable targets for development of specific inhibitors with minimal effects on physiology of mammalian hosts.     

Protozoan parasite-specific carbohydrate structures

The carbohydrate moieties displayed by pathogenic protozoan parasites exhibit many unusual structural features and their expression is often developmentally regulated. These unique structures suggest a specific relationship between such carbohydrates and parasite pathogenicity. Studies of infected humans indicate that immune responses to protozoan parasites are elicited by glycan determinants on cell-surface or secreted molecules. Infections by protozoa are a major worldwide health problem, and no vaccines or efficacious treatments exist to date. Recent progress has been made in elucidating the structure and function of carbohydrates displayed by major protozoan parasites that infect man. These structures can be used as prototypes for the chemical or combined chemo-enzymatic synthesis of new compounds for diagnosis and vaccine development, or as inhibitors specifically designed to target parasite glycan biosynthesis.     

The temperate-tropical gradient of planktonic Protozoa and Rotifera

Many flagellates, ciliates and rhizopods appear to be cosmopolitan, at least when considered at the morphospecies level. There are indications of tropical endemics among the ciliates and the rhizopods, but the percentage of endemics appears to be low. Among the rotifers there is a well marked latitudinal gradient, but the picture is complicated by the occurrence of warm water species during hot summers in temperate regions. A further complication has been introduced by the artificial development of heated water associated with power stations. The characteristic rotifer associations of the tropics are governed largely by temperature and salinity. A study of the altitudinal distribution of rotifers in Africa reveals an interplay between latitude and altitude in determining the similarities of the associations to those found in the temperate Old World.     

Protozoan communities in chalk streams

This study assessed the individual effects of three mayflies (Paraleptophlebia sp., Ephemerella subvaria McDunnough and Epeorus sp.) and one caddisfly (Psilotreta sp.) on periphyton communities associated with clay tiles and leaves. Algal densities were estimated for leaf discs and tiles from experimental chambers (with individual grazers) and control chambers (i.e., no grazers). Scanning electron micrographs (SEM) of leaf discs and tiles also were taken for all mayfly grazing experiments. Densities of algae on leaf discs were two to five times lower than on tiles. Mouthpart morphology influenced how different insects grazed the periphyton community. Paraleptophlebia had typical collector-gatherer mouthparts and had no effect on diatom densities associated with leaves whereas diatom densities on grazed tiles were higher than densities on tiles from control chambers. Epeorus had brusher mouthparts and had little impact on diatom densities regardless of substratum type. The other two grazers had the blade-like mandibles of a scraper. Psilotreta did not reduce the numerical abundance of diatoms on either substratum, but did alter community structure by significantly reducing densities of stalked Gomphonema olivaceum and large species of Navicula and Nitzschia; densities of smaller diatoms (Achnanthes spp) increased. However, E. subvaria reduced densities of most algal species regardless of size on both substrata and also significantly altered community structure. SEMs of substrata grazed by mayflies showed reductions in fungal hyphae on all grazed leaf discs, decreases in filamentous algal forms on grazed tiles, and greatly shortened stalks of G. olivaceum (Paraleptophlebia only). Thus, periphyton communities are different on leaves versus tiles and grazers with different mouthpart morphologies have varying effects on both algal and heterotrophic microbial community structure.