Endomyces tetrasperma, sp. n

A new fungal species has been described and placed in the genus Endomyces. Endomyces tetrasperma forms a true septate, multinucleate mycelium which breaks up into arthrospores. Ascus formation occurs after isogamous copulation between sexual protuberances which develop at the ends of arthrospores or between two cells, adjacent mycelial cells, or arthrospores. The asci which dehisce at maturity release two to four smooth, ovoid, thick-walled spores, each containing two oil droplets. The proposed life cycle is based on morphological and cytological observations.     

SEXUAL REPRODUCTION IN NAVICULA CRYPTOCEPHALA (BACILLARIOPHYCEAE)1

Homothallic sexual reproduction and auxosporulation were studied in monoclonal cultures and seminatural populations of the freshwater epipelic diatom Navicula cryptocephala Kütz. Gametangia paired via the girdle, one gamete was formed per gametangium (and hence one zygote per pair of gametangia), and gamete fusion took place without the formation of any copulation envelope or copulation canal. Superfluous nuclei from meiosis survived unusually long, so that gametes and young zygotes were probably functionally polyploid; later, all but two haploid nuclei degenerated. Expanded auxospores had a swollen center, but during formation of the initial valves, the auxospore contracted away from the perizonium to produce linear‐lanceolate valves. The pattern of reproductive behavior found in N. cryptocephala can be classified as type IIA2a auxosporulation in Geitler's system. The same type of zygote and auxospore formation seen in clonal cultures was observed in seminatural material from four lakes in Scotland and the Czech Republic. Variation in nuclear structure and auxosporulation in the N. cryptocephala species complex is discussed, as is the evolution of type II auxosporulation (one zygote per pair of gametangia) from type I auxosporulation (two zygotes per pair). The penalty of smaller numbers of zygote produced in type II may be outweighed by formation of larger auxospores (prolonging the vegetative phase) or more vigorous auxospores. The variation present among members of the N. cryptocephala complex indicates that biogeographical analyses based on use of the name N. cryptocephala, as performed recently to support the ubiquity hypothesis of protist distributions, are almost meaningless.     

Properties of cell surface carbohydrates in sexual reproduction of the Closterium peracerosum–strigosum–littorale complex (Zygnematophyceae,Charophyta)

The Closterium peracerosum–strigosum–littorale complex is a best characterized zygnematophycean green alga with respect to the process of sexual reproduction. Intercellular communication mediated by two sex pheromones has been well documented in this organism, but information concerning direct cell–cell recognition and fusion of cells involved in conjugation processes has not yet been clarified. In this study, we examined the properties of cell surface carbohydrates in vegetative and reproductive cells using a variety of fluorescein isothiocyanate labeled lectins as probes. Among 20 lectins tested, 10 bound to the Closterium cell surface, and eight of these were specific for the cells involved in sexual reproduction. In addition, some of the lectins inhibited the progress of zygote formation. In particular, Lycopersicon esculentum lectin (LEL) and ConcanavalinA (ConA) considerably inhibited zygote formation (23.6% and 0% of zygotes formed, respectively, compared with the control). LEL mainly accumulated on conjugation papillae and on the surface and lumens of empty cell walls remaining after zygote formation. ConA bound to both vegetative and sexually reproductive cells and strongly accumulated on the conjugation papillae of the latter, indicating ConA binding material(s) are non‐specifically present in Closterium cells but some of the material(s) would be essential for zygote formation. These results suggest that different carbohydrates specifically recognized by these lectins are involved in cell recognition and/or fusion during conjugation processes in the C. psl. complex.     

Development, Characterization, and Use of Monoclonal and Polyclonal Antibodies against the Myxosporean, Ceratomyxa shasta

Both monoclonal and polyclonal antisera were produced against Ceratomyxa shasta. Ascites containing trophozoites of the parasite was collected from infected fish and used as antigen for immunization of mice. The resulting monoclonal antibodies reacted specifically with trophozoite and sporoblast stages but did not react with C. shasta spores by either indirect fluorescent antibody techniques or in Western blots. This indicates that some C. shasta antigens are specific to certain life stages of the parasite. Polyclonal antiserum was produced in a rabbit by injecting a spore protein electro-eluted from an SDS-polyacrylamide gel. This antiserum reacted with both trophozoites and spores by indirect fluorescent antibody techniques and in Western blots. All antisera were tested for cross-reactivity to trout white blood cells, a contaminant of the ascites, and to other myxosporea. Two monoclonal antibodies reacted with white blood cells and myxosporea of the genera Sphaerospora and Myxobilatus. One hybridoma produced antibodies of high specificity for C. shasta pre-spore stages. This is the first report of a monoclonal antibody produced against a myxosporean parasite.     

Programmed ascospore death in the homothallic ascomycete Coniochaeta tetraspora

Immature asci of Coniochaeta tetraspora originally contain eight uninucleate ascospores. Two ascospore pairs in each ascus survive and mature, and two die and degenerate. Arrangement of the two ascospore types in individual linear asci is what would be expected if death is controlled by a chromosomal gene segregating at the second meiotic division in about 50% of asci. Cultures originating from single homokaryotic ascospores or from single uninucleate conidia are self-fertile, again producing eight-spored asci in which four spores disintegrate, generation after generation. These observations indicate that differentiation of two nuclear types occurs de novo in each sexual generation, that it involves alteration of a specific chromosome locus, and that the change occurs early in the sexual phase. One, and only one, of the two haploid nuclei entering each functional zygote must carry the altered element, which is segregated into two of the four meiotic products and is eliminated when ascospores that contain it disintegrate. Fusion of nuclei cannot be random-a recognition mechanism must exist. More study will be needed to determine whether the change that is responsible for ascospore death is genetic or epigenetic, whether it occurs just before the formation of each ascus or originates only once in the ascogonium prior to proliferation of ascogenous hyphae, and whether it reflects developmentally triggered alteration at a locus other than mating type or the activation of a silent mating-type gene that has pleiotropic effects. Similar considerations apply to species such as Sclerotinia trifoliorum and Chromocrea spinulosa, in which all ascospores survive but half the spores in each ascus are small and self-sterile. Unlike C. tetraspora, another four-spored species, Coniochaetidium savoryi, is pseudohomothallic, with ascus development resembling that of Podospora anserina.     

The pattern of sporulation in Anabaena circinalis and comments on the role of heterocysts in sporulation in blue-green algae.

Cells between two intercalary heterocysts differentiate at random into spores in A. circinalis. One or more cells, which fail to transform into spores, are present between the two adjacent spores, and these cells disorganize later. A critical C:N ratio regulates sporulation and heterocyst formation. During sporulation the reductive ability of the heterocyst gradually diminishes. It is concluded on the basis of this and other evidence that sporulation is regulated by interactions between heterocysts and vegative cells which are manifested in diverse patterns in different species of blue-green algae.     

子囊菌交配型位点与交配型基因研究进展

有性生殖是真菌的生殖方式之一,是真菌遗传重组的重要驱动力。交配型(mating-type,MAT)位点控制真菌性别,在有性生殖过程中起决定性作用。不同类型真菌MAT位点的基因组成、排列方式和编码蛋白不尽相同。近年来,MAT位点和MAT基因的功能与调控网络研究进展较快。本文对子囊菌交配型位点的基因组成及分布、MAT基因的功能、MAT位点与有性生殖调控通路的关系等进行了综述。     

Differences between Brachiola (Nosema) algerae isolates of human and insect origin when tested using an in vitro spore germination assay and a cultured cell infection assay

Brachiola (Nosema) algerae is a microsporidian species generally believed to be an intracellular parasite of insects, especially mosquitoes. However, both mosquito and human isolates have been shown to infect mammalian cells. The present study was undertaken to determine if spores of two insect and two human isolates of B. algerae cultured at 30 degrees C and 37 degrees C differed in their ability to germinate and infect cultured green monkey kidney cells at these two temperatures. Spores from all four isolates exhibited an optimum pH of 9.5 for germination. Mercury (Hg2+) inhibited germination of all isolates equally. Germination of spores from all four isolates was significantly greater when the parasite was cultured at 30 degrees C than when cultured at 37 degrees C. However, spores from the insect isolates cultivated at 30 degrees C or 37 degrees C infected significantly fewer mammalian cells at 37 degrees C than did spores from the human isolates under the same conditions. Thus, there is no correlation between the effects of temperature on the germination and the infectivity of an isolate. In addition, while exposure of B. algerae to 37 degrees C has been reported to cause spore dysmorphism, we failed to observe any consistent ultrastructural changes that explained the greater infectivity of the human isolates at 37 degrees C.     

AUXOSPORE FORMATION IN TWO MARINE CLONES OF THE DIATOM GENUS COSCINODISCUS

Auxospore formation has been observed in two marine clones of the diatom genus Coscinodiscus. In each of these clones the variation in valve morphology and structure before and after auxospore formation is appreciable. This variability suggests a reappraisal of the taxonomic characters within the genus will be required if the kinds and types of variation noted are substantiated in other clones. The clones are monecious and the 32 uniflagellate colorless monads, inferred from indirect evidence to be male gametes, form within an undifferentiated mother cell. The method of release of the male gametes differs in the two clones; otherwise their development is similar. The zygote is recognizable and the formation of large diameter cells within the zygote membranes has been observed.     

Identification and the developmental formation of carotenoid pigments in the yellow/orange Bacillus spore-formers

Spore-forming Bacillus species capable of synthesising carotenoid pigments have recently been isolated. To date the detailed characterisation of these carotenoids and their formation has not been described. In the present article biochemical analysis on the carotenoids responsible for the yellow/orange pigmentation present in Bacilli has been carried out and the identity of the carotenoids present was elucidated. Chromatographic, UV/Vis and Mass Spectral (MS) data have revealed the exclusive presence of a C(30) carotenoid biosynthetic pathway in Bacillus species. Apophytoene was detected representing the first genuine carotenoid formed by this pathway. Cultivation in the presence of diphenylamine (DPA), a known inhibitor of pathway desaturation resulted in the accumulation of apophytoene along with other intermediates of desaturation (e.g. apophytofluene and apo-ζ-carotene). The most abundant carotenoids present in the Bacillus species were oxygenated derivatives of apolycopene, which have either undergone glycosylation and/or esterification. The presence of fatty acid moieties (C(9) to C(15)) attached to the sugar residue via an ester linkage was revealed by saponification and MS/MS analysis. In source fragmentation showed the presence of a hexose sugar associated with apolycopene derivatives. The most abundant apocarotenoids determined were glycosyl-apolycopene and glycosyl-4'-methyl-apolycopenoate esters. Analysis of these carotenoids over the developmental formation of spores revealed that 5-glycosyl-4'-methyl-apolycopenoate was related to sporulation. Potential biosynthetic pathways for the formation of these apocarotenoids in vegetative cells and spores have been reconstructed from intermediates and end-products were elucidated.     

Ethylene as a potent inducer of sexual development

A novel and critical function of ethylene, a potent plant hormone, has been well documented in Dictyostelium, because it leads cells to the sexual development (macrocyst formation) by inducing zygote formation. Zygote formation (sexual cell fusion) and the subsequent nuclear fusion are the characteristic events occurring during macrocyst formation. A novel gene, zyg1 was found to be predominantly expressed during the sexual development, and its enforced expression actually induces zygote formation. As expected, the zygote inducer, ethylene enhances the expression of zyg1. Thus the function of ethylene has been verified at all of individual (macrocyst formation), cellular (zygote formation), and molecular levels (zyg1 expression). Based on our recent studies concerning the behavior and function of the zyg1 product (ZYG1 protein), the signal transduction pathways involved in zygote formation are proposed in this review.     

Correlation of the DNA nucleotide makeup with the physiological and cytological characteristics of spore-forming anaerobic bacteria]

The nucleotide composition of DNA from 12 studied species of anaerobic bacteria belongs to AT type, with G+C varying from 28.4 to 36.8 mole%. In the anaerobic group of Clostridium bifermentans, a correlation has been established between the nucleotide composition of DNA, the type of appendages on spores, and some physiologo-biochemical characteristics. The nucleotide composition of DNA in the spores of four anaerobic species is shifted toward GC type as compared to DNA in the vegetative cells. Data on the content of GC pairs in DNA of the spores may sometimes be of a higher taxonomic value than the corresponding evidence on DNA of the vegetative cells.     

Plastid Replication in Vegetative Cells, Sporangia, Spores and Sporelings of Red Algae

Ultrastructural aspects of proplastid and chloroplast replicationare described as seen in sections of vegetative cells, sporangia,released spores and sporelings of the red algae Palmaria palmataand Plumaria elegans. Proplastids in apical vegetative cellsshow internal thylakoid formation from peripheral thylakoidsin both species, and proplastid formation by budding from maturechloroplasts has also been observed. Proplastid replicationby fission has been occasionally observed, and genophore divisionin the stroma of proplastids. In vegetative cells, sporangia,spores and sporelings chloroplast formation from mature plastidscan take place by elongation and fission, or by formation ofa discrete group of thylakoids which become pinched off fromthe parent chloroplast, and by irregular expansions of the parentchloroplasts with subsequent multiple fission. Plastid replication, vegetative cells, sporangia, spores, red algae     

Myxosporean parasites of the catfish,Clarias lazera (Valenciennes)

Summary Five new species of myxosporean were found in the catfish Clarias lazera (Val.) in Israel. These species are described as: Henneguya laterocapsulata n. sp. (cyst-like trophozoites in the skin), H. suprabranchiae n. sp. (cyst-like trophozoites in the suprabranchial respiratory organs), Sphaerospora inaequalis n. sp. (spores in the lumen of the kidney tubules), Myxidium clariae n. sp. (spores in the gall bladder) and Myxobolus heterofilamentatus n. sp. (spores in the kidney, spleen, liver, suprabranchial respiratory organ, gills, heart and urinary bladder). Their taxonomic affinities to other species are discussed. ac]19860407     

Promotion of Zygote Formation by Protein Kinase Inhibitors during the Sexual Development of Dictyostelium mucoroides

To analyze the possible involvement of protein kinases in the sexual development (macrocyst formation) of the cellular slime mold Dictyostelium mucoroides-7 (Dm7), the effects of several protein kinase inhibitors were examined. K252a, a potent inhibitor of protein kinase activities, promoted the sexual cell fusion, through enhancement of gamete formation. In contrast, staurosporine (structurally and functionally similar to K252a) inhibited markedly the progress of development including cell aggregation, thus resulting in the failure of cells to form mature macrocysts. The effective period of K252a was 5–7 hr after starvation, during which Dm7 cells could acquire fusion competence, and the inhibitory effect of cAMP on zygote formation was nullified by the co-application of K252a. Although KT5720 (a specific inhibitor of cAMP-dependent protein kinase) and W7 (a calmodulin inhibitor) had no effects on zygote formation when applied separately, their combined application enhanced zygote formation like K252a did. Neither calphostin C (a specific inhibitor of Ca²⁺-dependent protein kinase) nor herbimycin A (a specific inhibitor of tyrosine kinase) exerted a stimulative influence upon macrocyst formation. These results strongly suggest that the two signal transduction pathways mediated by cAMP-dependent protein kinase (PKA) and calmodulin are closely related to zygote formation, their blockage being favorable to zygote formation.     

Temperature sensitivity of flocculation induction,conjugation and sporulation in fission yeast

Homothallic cultures of Schizosaccharomyces pombe, anaerobically grown to stationary phase in broth at 32°C, were induced by aeration to flocculate. Flocculation was followed by copulation, conjugation, zygote formation, meiosis and sporulation. Cultures grown to stationary phase at 32°C and then aerated at 37°C did not sporulate. Grown to stationary phase at 37°C, cultures were not immediately inducible when aerated at 32°C. To identify which events in the developmental sequence were thermosensitive, we grew and induced cultures at 32°C and then shifted them at various times to 37°C. We observed the following events to be thermosensitive: development of respiratory sufficiency, readiness (inducibility of a culture within 1 h), flocculation induction, copulation, conjugation and early sporulation (including meiosis). Respiration, flocculation and spore maturation were thermoresistant. Conjugation-induced lysis and post-developmental deflocculation were enhanced at 37°C.NRCC no. 17775     

Bile salts and glycine as cogerminants for Clostridium difficile spores

Spore formation by Clostridium difficile is a significant obstacle to overcoming hospital-acquired C. difficile-associated disease. Spores are resistant to heat, radiation, chemicals, and antibiotics, making a contaminated environment difficult to clean. To cause disease, however, spores must germinate and grow out as vegetative cells. The germination of C. difficile spores has not been examined in detail. In an effort to understand the germination of C. difficile spores, we characterized the response of C. difficile spores to bile. We found that cholate derivatives and the amino acid glycine act as cogerminants. Deoxycholate, a metabolite of cholate produced by the normal intestinal flora, also induced germination of C. difficile spores but prevented the growth of vegetative C. difficile. A model of resistance to C. difficile colonization mediated by the normal bacterial flora is proposed.     

Site preference of myxozoans in the kidneys of Hungarian fishes

Myxozoans are common parasites of fish kidneys, with most having specific sites of development. Five specific sites of development include (1) the lumen of renal tubules, (2) the renal corpuscles followed by location in renal tubules, (3) intracellular location within the tubular epithelium followed by a stage in the lumen of the ducts, (4) haematopoietic tissue with dispersed trophozoites, and (5) haematopoietic tissue with large, localized plasmodia. A coelozoic development preceded by presporogonic multiplication characterises most Sphaerospora spp. Early plasmodial stages of Myxidium and Chloromyxum spp. are frequently found in the renal glomerules, while spores develop in the urinary channels in plasmodia released from the renal corpuscles. In Hoferellus and Myxobilatus spp., spores are formed in small plasmodia inside the lumen of the urinary ducts after several internal cleavages in the epithelium of renal tubules. The presence of dispersed trophozoites among haematopoietic tissue cells of the renal interstitium characterises the development of Sphaerospora tincae and Tetracapsuloides bryosalmonae, the causative agent of proliferative kidney disease (PKD). Spores of S. tincae are formed at the place of plasmodial development, while spore formation of PKD is in the renal tubules. A large mass of spores, often surrounded by a connective tissue capsule, can appear in the renal interstitium during infections by several Myxobolus spp.; furthermore, a large number of these spores formed in plasmodia in distant tissues can also accumulate in melano-macrophage centres.     

Dimorphic spore production in the genus Acaulospora

Species of the genus Acaulospora are partly characterized by the production of ‘acaulosporoid’ spores. The simultaneous formation of glomoid and acaulosporoid spores by some species in the Glomeromycota has been used as a basis for taxonomic classification. We report the presence of both glomoid and acaulosporoid spores in four Acaulospora species. Analysis of the 18S rRNA gene confirmed that only A. spinosa was present in a pot culture that produced two morphs. The functional significance of dimorphic spore production is unknown but the production of blastic spores is not a characteristic that can have any significance as a taxonomic character.