Conidium Ontogeny Research Articles

Annellated conidiogenous cells in Trichosporium heteromorphum Nannfeldt

The present study of the type culture of Trichosporium heteromorphum by scanning electron microscopy has confirmed de Hoog's description that the mode of conidium ontogeny in this culture is annellidic. Neither phialides with collarettes nor sympodial conidiogenous cells were found. Thus, T. heteromorphum should be placed in the genus Exophiala. The taxonomic position of this fungus and its relationship to Exophiala jeanselmei and E. dermatitidis has been briefly discussed.

Taxonomy of the Pecan Scab Fungus Cladosporium caryigenum

Conidiophore morphology, conidium ontogeny and cultural characteristics of the pecan scab fungus were studied to establish its generic position. Extensive catenulate, dendritic conidial chains and multidenticulate conidiogenous ramoconidia are characteristic of the pecan scab fungus. The transfer of Fusicladium effusum to the genus Cladosporium as well as Cladosporium caryigenum comb. nov. is proposed.

Ultrastructure of thermophilic fungi: V. Conidial ontogeny in Humicola grisea var. thermoidea and H. insolens

It is proposed that Humicola grisea var. thermoidea is a synonym of Humicola insolens. H. insolens is characterized by the development of two distinct spore types, Type 1 conidia representing typical aleuriospores, and Type 2 conidia representing typical chlamydospores. Conidial ontogeny demonstrates a developmental plasticity not seen in other species, e.g. Type 1 conidia are produced both holoblastically and holothallically.

Taxonomy and morphology of dematiaceous fungi isolated from nature

The Hughes system of classification was applied to the identification of dematiaceous fungi isolated from nature. The majority of the isolates encountered could be identified with this system using brightfield microscopy. However, phase contrast microscopy was needed to determine the mode of conidial ontogeny with some species of Phialophora, Exophiala and Wangiella. The identifications based upon phase contrast microscopy were confirmed using the scanning electron microscope (SEM). Scanning electron photomicrographs are presented for Bispora betulina, Cladosporium trichoides, Exophiala jeanselmei, Phialophora revens, P. verrucosa and Wangiella dermatitidis. SEM observations of W. dermatitidis support the present classification of this organism as proposed by other workers. It is suggested that the Hughes system of classification and phase contrast microscopy be used to facilitate identification of isolates of dematiaceous fungi encountered in the clinical laboratory.

New or noteworthy aquatic hyphomycetes. Clavatospora, Heliscella, Nawawia and Heliscina

On the basis of conidium ontogeny the genus Clavatospora is redefined and subdivided. Heliscella gen.nov. is proposed for C. stellata and C. stellatacula whereas the new genus Nawawia is erected for C. filiformis. Clavatospora flagellata is transferred to Alatospora . Two species with percurrently proliferating conidiogenous cells are described in a new genus Heliscina . A key is provided for species having conidia with a clavate axis and apical outgrowths or appendages.

Conidium Ontogeny and Cytology of Tubakia dryina from Louisiana Hardwoods

SUMMARYThe nuclear condition of mycelium, fruiting body cells, conidiogenous cells and conidia was determined for Tubakia dryina. All cells in the fruiting body were uninucleate, but the conidia were binucleate. The type of conidium ontogeny was found to be proliferating phialidic.

On the taxonomy of Monilia roreri, an important pathogen of Theobroma cacao in South America

Monilia roreri Cif., the causal agent of an important pod rot of cocoa in South America, is redescribed and illustrated. The presence of dolipore septa in the vegetative mycelium indicating basidiomycetous affinities and the development of the conidia in basipetal chains necessitate the transfer of the fungus to another genus. The new genus Moniliophthora is proposed. Conidium ontogeny shows similarities with the genera Basipetospora and the anamorph of Blumeria (=Erysiphe).

Numerical taxonomy of certain genera of Fungi Imperfecti and Ascomycotina

Various clustering and ordination techniques are used on data collected from 88 cultures of Fungi Imperfecti and imperfect states of Ascomycotina to produce classifications. The data consist of 98 characters representing the morphology, conidium ontogeny, and physiology of the cultures. Although 23 genera are represented, emphasis is placed on Graphium sensu lato and Ceratocystis to which half the cultures belong. Seven groups which cluster consistently in all the techniques used are recognized, groups A to G. Group A contains species which have the annellidic type of conidiation, namely Trichurus. Scopulariopsis, Doratomyces, and Microascus. Group B contains the phialidic Chalara-type Ceratocystis species. Group C is characterized by the sympodial type of conidiation of the Sporothrix type and contains species from Petriella and Sporocybe. Group D contains an assortment of species which display the typical phialidic conidiogeny. Group E contains species from Ceratocystis and Graphium sensu lato which have holoblastic conidia with conidiogenous cells of the ramoconidium type. Group F is a loose cluster of species characterized by sympodial conidiation and contains species from Graphium sensu lato, Ceratocystis, and Verticicladiella. Group G contains species of Periconia which produce large conidia polyblastically. This numerical classification provides new evidence to support the classifications based on conidium ontogeny.

不完全菌類の分生子形成法

The conidial fungi are those members of the Deuteromycetes which produce asexual, nonmotile and usually deciduous propagules (conidia) by de novo growth from, or conversion of a fertile hypha (conidiogenous cell). Accommodated in this group of fungi are most of the important pathogens causing plant and animal, including human, mycoses, many species associated with food spoilage and release of mycotoxins (e.g., aflatoxins), numerous microbes employed in antibiotic production and other industrial processes, several fungi which are potentially useful in biological control and a large number of microorganisms which have aroused the interest of experimentalists in many disciplines of biological sciences. The conidial fungi clearly rank as a very significant group within the Division Mycota. In spite of the recognized importance of conidial fungi, the taxonomy of this group is still confusing and cumbersome. Workers are often frustrated while attempting to identify species using conventional keys for identification which are usually based on highly variable morphological characters such as conidial shape, septation and pigmentation, conidiophore arrangement and cultural features. Investigations of conidial and conidiogenous cell development have provided new, genetically stable and thus, taxonomically reliable data which the systematist can incorporate into existing classifications in order to yield a more functional system. It has been this relationship between conidiogenesis and taxonomy that has been the principal impetus for continuation of these studies. Examination of aspects of conidium ontogeny, however, has recently involved additional research areas such as ultrastructure, cytology, biochemistry, plant pathology and medical mycology. The taxonomy of medically important conidial fungi is particularly chaotic. Many species are capable of alternating between yeast and hyphal phases both in tissue and pure culture, which increases the difficulty of accurate identification of these microorganisms. The minute size of most pathogenic species of such genera as Phialophora, Exophiala, Cladosporium, Sporothrix and Histoplasma also places strain on the mycologist to identify these fungi based on light-microscopic examinations of morphological characters alone. Electron-microscopic investigations of conidial fungi have provided new and taxonomically significant information by revealing aspects of conidiogenesis which have clarified earlier developmental concepts and defined new categories of conidium and conidiogenous cell ontogeny. By correlation of data obtained by light- and electron-microscopic analyses, certain key morphological features which are recognizable with the light microscope can be used, retrospectively, for identification of a particular mode of development. Such correlation is necessary for the formulation of a functional classification in which developmental characters are employed. The categories of conidial and conidiogenous cell development described in this paper provide the basis for incorporation of such characters into existing classifications of conidial fungi.

The ultrastructure of conidium ontogeny in Pestalotiopsis neglecta

Electron microscopy has been used to study conidium ontogeny of Pestalotiopsis neglecta, an annellidic coelomycete, to compare it with previously studied phialidic fungi. It was found that phialidic fungi produce a multiplicity of conidia from a fixed conidiogenous locus within the conidiophore, but annellidic fungi produce conidia individually from progressively different, usually higher, loci within the conidiophore. With the exception of the primary phialidic conidium, both types of organism produce conidia enteroblastically.

Conidium ontogeny in the Chalara state of Ceratocystis adiposa: I. Light microscopy

The Chalara state of Ceratocystis adiposa (Butl.) C. Moreau forms two types of conidial chain, one of which is easily fragmented and composed of hyaline conidia, the other persistent and composed of hyaline or pigmented conidia. A sheath exists around the persistent chains. Both chain types are ontogenetically similar but conidia in persistent chains are variable in shape. The mode of conidium ontogeny is discussed in relation to this variability, and it is suggested that the conidiogenous locus is a meristem.

Light and electron microscopic observations of conidiogenesis in Peziza quelepidotia

Conidium ontogeny of the botryose solitary blastospores of Peziza quelepidotia Korf and O'Donnell was followed by time-lapse photomicrography using differential interference-contrast illumination in an inexpensive, commercially available, slide culture chamber. This chamber has several advantages over those previously described. Subsequent to time-lapse photomicrography, techniques are described for viewing these identical conidiophores in all stages of development in the scanning electron microscope. Transmission electron microscopic observations were conducted to fully characterize conidiogenesis and to unequivocally determine its location in hyphomycete classification schemes. This imperfect state, which belongs to Hughes' conidiogenetic section 1B, bears determinate retrogressive conidiogenous cells and single holoblastic conidia with multiple synchronous conidiogenous loci. However, unlike other members of the Botryoblastosporae, the conidia are not borne on well differentiated swollen conidiogenous cells (i.e., ampullae). Ultrastructural observations were made on the spatial relationship between the conidial state and ascogonia and on germinating conidia.

Ultrastructure of conidium ontogeny in Phoma pomorum, Microsphaeropsis olivaceum, and Coniothyrium fuckelii

The techniques of electron microscopy have been used to elucidate the details of conidium ontogeny in Phoma pomorum, Microsphaeropsis olivaceum, and Coniothyrium fuckelii. All three of these organisms were shown to be phialidic. The pyenidia of these organisms contained an electron-dense matrix, which in nature, probably functions as an aid to spore dispersal. In Phoma pomorum it was possible to trace conidia to their originating conidiophore through this matrix.

The thallic mode of conidiogenesis in the Fungi Imperfecti

The current developmental concept of the thallic mode of conidiogenesis essentially involves the simple conversion and disarticulation of preexisting hyphal elements, in which extension growth has ceased, into conidia which are delimited by transverse septa. Two kinds of thallic development were originally interpreted from light microscopic investigations. In this paper, holothallic conidium formation, which is demonstrated by Geotricluim candidum, and enterothallic development, which is exemplified by Sporendonema purpurascens and Briosia cubispora, are compared and ultrastructural and karyological characteristics of these mechanisms of conidiogenesis are illustrated. Scanning electron microscopic analyses of conidium formation in Oidiodendron trancatum and Trichosporon beigelii and light microscopic investigations of Sympodiella sp. and Amblyosporium spongiosum have revealed that additional variations exist in the thallic mode of conidium ontogeny. On the basis of these new data, and a consideration of other species of imperfect fungi which demonstrate similar mechanisms of conidiogenesis, a revised concept of thallic development is presented.

The Ultrastructure of the Formation of Chains of Conidia in Memnoniella echinata

SUMMARYThe conidial ontogeny of Memnoniella is very similar to that described for other phialidic Deuteromycotina. The persistence of the chain of conidia appears to be mostly due to the strength of the septum between spores and not to the pellicle or slime sheath which may cover the chain and the phialide. The main difference between a phialide producing chains of conidia as in Memnoniella, and one producing slimy heads, as in Stachybotrys, is in the length of time between the formation of the septum in the phialide neck and its splitting when the conidia separate.

The Ultrastructure of the Formation of Chains of Conidia inMemnoniella Echinata

The conidial ontogeny of Memnoniella is very similar to that described for other phialidic Deuteromycotina. The persistence of the chain of conidia appears to be mostly due to the strength of the s...

Conidium ontogeny in the xerophilic fungus Wallemia sebi

A simple method of slide culture is described which allowed a sequence of photomicrographs to be taken of Wallemia sebi (Fries) von Arx, showing the development of conidia on an individual fertile branch. A cylindrical structure develops above a constriction in the fertile branch. A cross wall divides the cylinder into an upper and lower cell. The upper cell is not meristematic but a cross wall forms in it, cutting it into two equal parts. Each part divides again so that a row of four cells is formed, the length of each cell being equal to its width. These cells round off to produce a row of four conidia. The lower cell of the cylinder is meristematic. It elongates and then divides into an upper and a lower cell, in the same manner as the cylinder, simultaneously with the maturation of the first four conidia. The new upper cell produces four more conidia. This cycle of conidium production in groups of four is repeated many times so that a long chain of conidia is produced. Explanations of conidium ontogeny in W. sebi by various authors since Vuillemin (1906) are discussedin the light of these observations. It is concluded that W. sebi shows characters of both Section IV (conidia produced on phialides) and Section VIIA (thallic-arthric conidia) and some unique features.

A NewGyrothrixin Culture and a Key to Species

Gyrothrix pediculata is described from culture as new. Its conidial ontogeny is readily studied in culture. The conidiogenous cells are entero-blastic, phialidic. The nonseptate conidia elongate la...

A New Gyrothrix in Culture and a Key to Species

SUMMARYGyrothrix pediculata is described from culture as new. Its conidial ontogeny is readily studied in culture. The conidiogenous cells are entero-blastic, phialidic. The nonseptate conidia elongate laterally and are produced in pseudochains. A key is given for the 15 species of Gyrothrix.

Conidium ontogeny in hyphomycetes. The meristem arthrospores of Wallemia sebi

Conidium ontogeny in Wallemia sebi (Fr.) v. Arx is analyzed and illustrated by time-lapse photomicrography. The nuclear configurations occurring during conidiogenesis are described and subsequent nuclear distribution reported. The conidia are considered to be meristem arthrospores of a unique type.