Life cycle of the endoparasitic nematophagous fungus Meria coniospora: a light and electron microscopic study

The obligate endoparasitic fungus Meria coniospora lives its entire vegetative life within infected nematodes. Conidia of M. coniospora infect the nematode Panagrellus redivivus mainly in the mouth region. The infection, starting with adhesion of conidia to the nematode surface, growth of trophic hyphae, production of conidiophores and conidia, was followed using light, scanning and transmission electron microscopy.This work was supported by grants from the Swedish Natural Science Research Council.     

Dactylella chichisimensis, sp. nov. in the Bonin (Ogasawara) Islands, Japan

ADactylella isolate obtained from soil in the Bonin (Ogasawara) Islands, Japan is described and illustrated as a new species,D. chichisimensis. The fungus is characterized by single terminal multiseptate clavate or ellipsoidal conidia at the apex of simple conidiophores and mycelium that forms chlamydospores and sclerotia. A key is provided for sixDactylella species that produce primary clavate or ellipsoidal conidia at the apex of simple conidiophores.     

Association of ergot alkaloids with conidiation in Aspergillus fumigatus

Ergot alkaloids are mycotoxins that affect the nervous and reproductive systems of exposed individuals through interactions with monoamine receptors. They have been studied more widely in ergot fungi and grass endophytes but also are found in Aspergillus fumigatus, an opportunistic human pathogen that reproduces and disseminates exclusively through conidia. The ergot alkaloids festucla-vine and fumigaclavines A, B and C are present in or on conidia of A. fumigatus. Cultures of the fungus that are free of conidia are difficult to obtain, obscuring comparisons of conidia versus vegetative hyphae as sources of the ergot alkaloids. To create conidiation-deficient strains of A. fumigatus we manipulated the bristle A gene (brlA), which controls vesicle formation or budding growth necessary for conidiation in Aspergillus spp. Disruption of brlA in A. fumigatus, via homologous recombination, resulted in a nonconidiating mutant that produced bristle-like structures instead of conidiophores and conidia. Moreover the disrupted strain failed to produce ergot alkaloids as verified by HPLC analyses. Complementation with a wild-type allele restored conidiation and ergot alkaloid production. These results suggest that ergot alkaloids are not produced within the vegetative mycelium of the fungus and are associated directly with conidiation.     

Four new coprophilous hyphomycetes

Four new and interesting coprophilous Hyphomycetes are described from India: (1)Sympodina coprophila gen. et sp. n. isolated from goat dung from Jaipur; this fungus produces 2-celled, brown, solitary, dry blastospores developing acrogenously at the tips of conidiophores and at their sympodially produced successive growing points; (2)Adhogamina ruchira gen. et sp. n. isolated from pony dung from Rishikesh; the fungus produces one-celled, brown, solitary, dry blastospores without longitudinal germ slit developing in basipetal order on conidiophores; (3)Bahupaathra samala gen. et sp. n. occurring on cow dung from Chakrata; the fungus produces distinct, erect, intricately branched conidiophores with fertile and sterile branches and one-celled slimy phialospores forming globose masses at the tips of characteristic collarettes; and (4)Angulimaya sundara gen. et sp. n. occurring on cow dung from Chakrata; the fungus produces erect conidiophores bearing crowded clusters of annellophores from which one-celled conidia are produced in simple dry basipetal chains. The forms are compared with related genera.     

Association of melanin content with conidiogenesis in Bipolaris Sorokiniana of barley (Hordeum vulgare L.)

Sixty-seven isolates of Bipolaris sorokiniana of barley, belonging to three groups (black, white and mixed) were studied to find an association of melanin with the spore production of the fungus. Conidiogenesis in black, white and mixed subpopulation of B. sorokiniana was positively correlated with melanin content/g of mycelium. Primary hyphae of black and mixed subpopulation differentiated into secondary hyphal structures which subsequently produced conidiophores and conidia. Primary hyphae could not differentiate into secondary hyphae and subsequently conidiophores and conidia in white subpopulation. A melanin containing mutant developed from white subpopulation regained its ability to differentiate into secondary hyphae, conidiophores and conidia. Results showed that melanization of mycelia B. sorokiniana mycelia is an important factor for conidia production.     

A new hyphomycete genus and species with pectinate conidia from a rainforest in Panama—a living fungal fossil?

A species of hyphomycetes, characterized by hyaline cells and asymmetric, pectinate (comblike) conidia, was collected on a dead fern rachis and on old conidiophores of the dematiaceous hyphomycete Dischloridium sp. in a rainforest in Western Panama. The structure of the conidia of the new species was previously known only for species of the fossil genus Ctenosporites. A new genus and species are proposed for the fungus from Panama.     

Fusarium kyushuense sp. nov. from Japan

Four trichothecene-producing strains originally isolated from diseased wheat and a vinyl plate in Kyushu and Shikoku, Japan are described and illustrated as a new species,Fusarium kyushuense. This species does not produce chalamydospores, which is the key morphological character which distinguishes it fromF. sporotrichioides with which it has been mistaken.Fusarium kyushuense is also differentiated from another morphologically similar species,F. arthrosporioides, by absence of sclerotia and by differences in conidiogenesis of obovate, conidia. InF. arthrosporioides conidia are partly holoblastic from the aerial conidiophores and mostly phialidic from the sporodochial conidiophores, while inF. kyushuense conidia are mostly holoblastic and only produced from aerial conidiophores.     

Materials for the fungus flora of Japan (54).Stenella persicae, a new species from peach

A new species,Stenella persicae, isolated from peach is described and illustrated. The fungus, pathogenic to peach fruits, is distinguished from other known species in the genus by its morphological characteristics. A stroma is absent, and conidia, verruculose and usually catenate in appearance, are produced blastically on simple and smooth conidiophores.     

Three newAspergillus species isolated from clinical sources as a causal agent of human aspergillosis

Three new species ofAspergillus isolated from clinical sources in China are described and illustrated:A. beijingensis, A. qizutongii andA. wangduanlii. The first species is characterized by spreading colonies, yellow to grayish green conidial heads, smooth-walled conidiophores with a clavate vesicle, uniseriate aspergilla and nearly globose, micro-verrucose conidia. The second is characterized by spreading colonies, olive-yellow conidial heads, conspicuously roughened conidiophores with a flask-shaped vesicle, uniseriate but often secondarily proliferating aspergilla and globose, smooth conidia. The third is characterized by rapidly growing colonies, dull green conidial heads, smooth to irregularly roughened conidiophores which are often surrounded by coiled hyphae in the basal part and are terminally swollen into a globose or irregular shaped vesicle, uniseriate aspergilla and globose, micro-verrucose conidia.     

<Emphasis Type="Italic">Synnemapestaloides rhododendri</Emphasis>, a new genus and new species of synnematous hyphomycete,causing synnemapestaloides twig blight disease of <Emphasis Type="Italic">Rhododendron brachycarpum</Emphasis> in Japan

A hyphomycete with black synnema and appendaged phragmoconidia was collected on Rhododendron brachycarpum showing twig blight symptom in Aomori Prefecture, Japan. The twig blight is macroscopically similar to the disease symptoms caused by Pycnostysanus azaleae. The fungus, however, has determinate synnemata, (1–)3-level verticillately branched conidiophores, and Pestalotia-like conidia. It cannot be accommodated by any existing genus of anamorphic fungi. A new genus Synnemapestaloides is established to accommodate the fungus, which is named S. rhododendri. The pathogenicity of the fungus on Rhododendron leaves and shoots is confirmed by inoculation. Synnemapestaloides twig blight is proposed for the disease of R. brachycarpum caused by the fungus.     

A new basidiomycetous anamorph genus with cruciform conidia

An undescribed hyphomycete with clamped septa, conidiophores aggregated in sporodochia, and cruciform, aseptate conidia apically borne on clamps was found on a branch of a deciduous tree lying on the ground. The septal pores are dolipores with perforate parenthesomes indicating a homobasidiomycetous relationship. The morphology and ecology of the fungus are discussed in relation to morphologically similar anamorphic basidiomycetes. Because the fungus could not be classified in any known genus, the new genus and new speciesCruciger lignatilis is proposed to accommodate this species.     

Developmental gene regulation in Aspergillus nidulans

The Ascomycete fungus Aspergillus nidulans reproduces asexually by differentiating conidiophores and conidia. Gene regulation during asexual reproduction was investigated by comparing poly(A) RNA populations derived from somatic hyphae, conidiating cultures and purified conidia. Single-copy and complementary DNA hybridization experiments showed that vegetative cells contained 5600–6000 diverse, average-sized poly(A) RNA sequences distributed into three prevalence classes. cDNA hybridization experiments indicated that a significant proportion of the poly(A) RNA derived from either conidiating cultures or spores consisted of sequences absent from somatic hyphae. To assess accurately the degree to which the poly(A) RNA populations differed, cDNA preparations were isolated which were complementary to sequences present only in conidia or in conidiating cultures. Hybridization of these cDNAs with poly(A) RNA from conidiating cultures showed that approximately 18.5% of the poly(A) RNA mass comprised 1300 diverse sequences not present in somatic cells. Of these, about 300 were present only in conidia. The remainder were accumulated specifically during sporulation, but were absent from spores. Analogous experiments showed that the great majority of the poly(A) RNA sequences accumulated by vegetative hyphae were also present in conidiating cultures. Thus, cell differentiation during A. nidulans asexual reproduction involves the accumulation of many new poly(A) RNA sequences, but not the loss of preexisting ones.     

Three new species and a new record of Diplococcium from plant debris in Spain

Diplococcium dimorphosporum sp. nov., D. racemosum sp. nov., D. singulare sp. nov. and D. pulneyense Subram. & Sekar collected from plant debris in natural areas of Spain are described and illustrated. The first species is characterized principally by the production of branched conidiophores and short chains of conidia. Diplococcium singulare has unbranched conidiophores, and conidia produced usually at the tip of conidiophores and from lateral spherical conidiogenous cells. In addition, both species develop a Selenosporella synanamorph with narrow falcate conidia. Diplococcium racemosum produces branched, verrucose conidiophores, and verrucose conidia in long branched chains. Diplococcium pulneyense is the second record, being described for first time on the natural substratum and re-described in pure culture. A key to currently accepted species of Diplococcium is provided.     

Taxonomy of an anamorphic xylariaceous fungus from a termite nest found together with <Emphasis Type="Italic">Xylaria angulosa</Emphasis>

Two xylariaceous fungi were isolated from a nest of a termite, Odontotermes formosanus, that was incubated in a laboratory after collecting from Iriomote Is., Okinawa Pref., in Japan. One of the two fungi was identified as Xylaria angulosa on the basis of the morphology of branched stroma produced on medium, tiny asci, and ascospores having a germ slit. Another fungus is an anamorphic fungus that produces synnemata up to 50 mm long from which dendritic conidiophores branch out. Unicellular conidia are holoblastically produced on a sympodially proliferating conidiogenous cell. Such morphological characters resemble those of the genus Geniculosporium. However, its distinctive synnema formation and dendritic conidiophores do not assign the fungus to Geniculosporium or other known genera and warrant establishment of a new genus. The phylogenetic tree based on the ITS regions of rDNA shows that the fungus is nested in the cluster of the genus Nemania (Xylariaceae), whose species have mainly Geniculosporium-like anamorphs. We describe here the present anamorphic fungus as Geniculisynnema termiticola gen. et sp. nov., and discuss its phylogenetic and ecological relationships to xylariaceous fungi, especially termiticolous species.     

Light stimulates conidiation of the entomopathogenic fungus Beauveria bassiana

Beauveria bassiana is a commercially important entomopathogenic fungus. Like other insect fungal pathogens, B. bassiana usually produces asexual reproductive bodies, conidia, for dispersal, transmission and infection of insects. Adequate mass-production of high quality conidia is crucial to development of an efficient B. bassiana insecticide. However, little is known about details of conidiation in this fungus in response to environmental signals, which limits understanding of the mechanism of conidiation and improvement in conidia production. Here, morphologenetic changes of B. bassiana under different light conditions are reported. When cultured in total darkness, B. bassiana hyphae can grow continuously with few reproductive structures differentiated, while illumination with white light resulted in prolific formation of conidiophores bearing abundant conidia, indicating that light could stimulate conidiation of B. bassiana. Among the single colour lights tested, blue light was the most effective to stimulating sporulation. Colonies became adapted for blue light stimulus only after hyphae had grown in total darkness for at least 96 h, whereas the photoadaptation obviously declined after 144 h. For the exposure time, 3 min of blue light pulse was enough to stimulate conidiation in the photoadapted mycelia, while prolonged light exposure over 3 min resulted in a decrease in conidia yield. Our results provided useful clues for understanding the mechanism of conidiation mediated by light in B. bassiana.     

Talaromyces lagunensis,a new species from Philippine soil

A new species ofTalaromyces (Ascomycetes; Trichocomaceae) with aPenicillium anamorph,T. lagunensis, is described and illustrated. This fungus is characterized by its extremely restricted growh on Czapek-yeast extract agar, light yellow to light orange ascomata with a telaperidium, catenate, pyriform or ellipsoidal asci, ellipsoidal or subglobose ascospores with a microtuberculate wall, short conidiophores with an irregular, mostly monoverticillate to biverticillate penicillus, and subglobose to ovoid conidia. The holotype was isolated from forest soil in the Philippines.     

<Emphasis Type="Italic">Myrothecium dimorphum</Emphasis>, sp. nov., a soil fungus from beach sand in the Bonin (Ogasawara) Islands,Japan

A new Myrothecium species isolated from beach sand in the Bonin Islands, Japan, is characterized by dark green sporodochia composed of conidiophores with verticillate phialides and ovate and ellipsoidal, often curved conidia on their apexes mixed with erect, straight setae, and seta-like conidiophores with terminal polytomous structures composed of 2–8 digitate polyphialides bearing single globose conidia at each apex.     

Leptographium pini-densiflorae sp. nov. from Japanese red pine

ALeptographium species was isolated from deadPinus densiflora at six sites in Japan. The fungus is morphologically most similar toL. lundbergii but could be distinguished from that species by its short stipes, primary branches of conidiophores, and conidia with a rounded to sub-truncate base. In addition, the colony morphology, growth rate and tolerance to the antibiotic cycloheximide of theLeptographium species andL. lundbergii differed markedly. Here we describe the fungus as a new species,Leptographium pini-densiflorae. Contribution No. 144, Laboratory of Plant Pathology and Mycology, Institute of Agriculture and Forestry, University of Tsukuba.     

Consecutive monitoring of lifelong production of conidia by individual conidiophores of Blumeria graminis f. sp. hordei on barley leaves by digital microscopic techniques with electrostatic micromanipulation

Conidial formation and secession by living conidiophores of Blumeria graminis f. sp. hordei on barley leaves were consecutively monitored using a high-fidelity digital microscopic technique combined with electrostatic micromanipulation to trap the released conidia. Conidial chains formed on conidiophores through a series of septum-mediated division and growth of generative cells. Apical conidial cells on the conidiophores were abstricted after the conidial chains developed ten conidial cells. The conidia were electrically conductive, and a positive charge was induced in the cells by a negatively polarized insulator probe (ebonite). The electrostatic force between the conidia and the insulator was used to attract the abstricted conidia from the conidiophores on leaves. This conidium movement from the targeted conidiophore to the rod was directly viewed under the digital microscope, and the length of the interval between conidial septation and secession, the total number of the conidia produced by a single conidiophore, and the modes of conidiogenesis were clarified. During the stage of conidial secession, the generative cells pushed new conidial cells upwards by repeated division and growth. The successive release of two apical conidia was synchronized with the successive septation and growth of a generative cell. The release ceased after 4-5 conidia were released without division and growth of the generative cell. Thus, the life of an individual conidiophore (from the erection of the conidiophore to the release of the final conidium) was shown to be 107 h and to produce an average of 33 conidia. To our knowledge, this is the first report on the direct estimation of life-long conidial production by a powdery mildew on host leaves.     

The life cycle of the insect pathogenic fungus Metarhizium anisopliae in the termite Nasutitermes exitiosus

In in vitro and in vivo studies the mode of penetration from Metarhizium anisopliae through the termite integument is elucidated. Serial sections and haemolymph studies elucidate the infective cycle within the host.Conidia germinate and penetrate the cuticle after a not-obligate formation of one or more appressoria. A penetration plate or hyphal bodies between cuticle layers form the base for the invasion of the body cavity, where the haemolymph distributes the multiplicating hyphal bodies. After the death of the insect due to various fungal toxins, organs and tissues are penetrated. Before the gut is invaded, the fungus breaks through to the outside and grows with a special air mycelium, which forms the conidiophores. From these structures the conidia, which stick together in bunches of chains, develope. These conidia can infect the nest mates.