Conidial Apparatus Research Articles

From on-site to in-lab: Microscopic observation of fungal proliferation on 17th century mural paintings

The fungal community of biodeteriorated 17th century mural paintings within the nave and altar portion of the old Church of the Holy Ascension (Veliki Krcimir, Nisava District, Serbia) has been studied via an array of microscopic analyses in order to detect actively growing fungi and assess their potential damage to the painted layer and mortar. In situ microscopy, performed with portable microscopes, together with optical and scanning electron microscopy, has revealed impairments of the painted layer in the form of cracks and biopitting, along with surface salt deposits and hidden, symptomless fungal growth. Various structures, such as fully developed fruiting bodies and melanized mycelia, clusters of microcolonial fungi and lichen soredia, as well as a conidial apparatus and numerous conidia in mass have been observed, all attesting to the presence of actively growing fungal community on the surface of the painted layer and in the interspaces between the painted layer and mortar. Based on the observed reproductive structures, the main agents of biodeterioration have been identified as fungi of Chaetomium and Cladosporium genera. The documented deterioration symptoms are most likely due to hyphal penetration and formation of fruiting bodies and other fungal structures.

Characterization of Aureobasidium pullulans isolated from airborne spores in Thailand.

Isolates from air in several locations in Thailand were identified as Aureobasidium pullulans PR with dark pigmentation (Loei province), A. pullulans SU with an unusual conidial apparatus (Chiangmai province), and A. pullulans CU with burgundy-red pigmentation (from a shady area in Bangkok). The internal transcribed spacer sequences of the rDNA of A. pullulans SU and A. pullulans CU confirmed that they were A. pullulans. Both A. pullulans CU and A. pullulans PR preferred 30 degrees C and pH 7.5 for exopolysaccharide (EPS) production, while A. pullulans SU preferred 25 degrees C and pH 6.5. All three isolates preferred glucose over sucrose and (NH(4))(2)SO4 over peptone for EPS production. Under optimal conditions, A. pullulans PR produced EPS yields of up to 0.225 g g(-1), followed by A. pullulans CU (0.185 g g(-1)) and A. pullulans SU (0.158 g g(-1)). Amylase activities were detected during the course of EPS production but gradually decreased as the EPS yields increased. IR spectra suggest that the EPS from these isolates was pullulan. EPS from the three isolates were partially sensitive to pullulanase.

Conidia of Polyporus varius

The asexual conidial apparatus of Polyporus varius is illustrated. Both clamped (dikaryotic) and unclamped (monokaryotic) mycelia produce aerial conidiophores with sparingly branched chains of dry, ovoid, unicellular conidia. Most conidia from the mycelium with clamp-connections germinate to give unclamped mycelia, but about 10% give mycelia with clamps.

Dicellomyces scirpi: Its conidial stage and taxonomic position

The conidial apparatus of Dicellomyces scirpi is described and compared with the very similar one in Auricularia, Exidia and Myxarium, and with the rather different one in Exobasidium japonicum.

Ultrastructure of conidium development in Erysiphe pisi

The ultrastructure of all vegetative and reproductive cell types throughout the cycle of conidium development in Erysiphe pisi has been examined using light and electron microscopy. The conidial apparatus comprises a conidiophore with, in succession above, a generative cell, and first- and second-stage conidial initials. At approximately 23 °C in a 16 h light: 8 h dark period, the onset of elongation and division of the generative cells, onset of elongation of first-stage conidia, and maturation and abscission of second-stage conidia were individually synchronized in one diurnal cycle. Synchrony was also maintained between 24 and 30 °C, and 12 h light: 12 h dark photoperiods but the generative cells elongated more slowly, achieving greater lengths than at lower temperatures. At 23 °C in continuous light, development was not synchronized. The ultrastructure of each cell was characteristic of its type and developmental phase. Glycogen became progressively abundant in maturing conidia and occurred in all other cells except hyphal apices and generative cells. In addition to the organelles usually found in Ascomycetes, two special endomembrane components have been found. One is a reticular vacuolar system which is expanded as a major vacuole at one end. The whole system encloses a region (vacuole-associated body) 1-2 μm across, rarely 8 μm, which is continuous with the main ground plasm via pores in the network. The vacuole-associated bodies always lacked ribosomes but sometimes contained glycogen. The other component is a compact endoplasmic reticulum organized as spheres 0.5–5 μm in diameter and composed of branching tubules which terminated in diverticulae and were sometimes interspersed with 8-nm filaments. Evidence for the functions of these organelles is discussed. The development and structure of the septa, of cytoplasmic components associated with conidial abscission, and of the walls of hyphae and conidia are discussed. All subaerial cell walls are covered with an osmiophilic cuticle with characteristic trilamellar structure and sometimes bearing granules and platelets. Evidence is presented that the cuticle is renewed following damage.

Phenotypes of Double Conidiation Mutants of Aspergillus nidulans

A series of strains, doubly mutant at conidiation loci, have been made. The phenotypes of these strains reflected the epistasy of earlier blocking mutants over later ones and confirmed the order of gene sequence predicted from the phenotypes of single mutants. Oligosporogenous mutants gave complex interactions, especially between brl and med mutants. These results indicated that (i) gene action overlapped in time, (ii) several parts of the conidial apparatus were interchangeable and (iii) nuclei leaving the vesicle were not irreversibly programmed. Structures produced by mutants were reminiscent of the conidial apparatus of other Aspergillus species and of related genera.

Anthopsis deltoidea, a new genus and species of Dematiaceae from soil

Anthopsis deltoidea n.gen. et n.sp. of dematiaceous Hyphomycetes, isolated from horticultural soil in Italy, is described. The new fungus is characterized by a peculiar conidial apparatus and by triangular conidia.

Influence of light on hülle cell and aleuriospore formation in Aspergillus

Hülle cell formation was directly dependent on darkness in strains of Aspergillus versicolor, A. ustus, A. flavipes , and A. niveus . On four different nutrient media hülle cells were observed exclusively or more abundantly in colonies grown in the dark. Aleuriospores in one strain of A. flavipes , although present in colonies cultivated in light, were produced in significantly greater quantities in cultures grown in the dark. Such effects are similar to those in other Aspergillus species where Sclerotium and cleistothecium formation are influenced by dark. Two divergent chains of events seem operative: one, affected by light, is conducive to early differentiation of hyphae and formation of the conidial apparatus; the other, affected by darkness, favours the normal development of mycelium and the successive events which lead to the production of such structures as sclerotia, aleuriospores, hülle cells, and cleistothecia.

Cell volume per nucleus in haploid and diploid strains of Aspergillus nidulans.

Summary: Diploid conidiospores of Aspergillus nidulans are uninucleate and have twice the volume of haploid conidiospores. On the other hand, the hyphae are coenocytic, and it has been found that the dimensions of the hyphal cell are unaffected by ploidy but that diploid cells have half as many nuclei as haploid ones. It is concluded from this that both cessation of growth in cells of fixed size and the timing of mitoses in coencytes are determined by a critical volume of cytoplasm per genome, rather than per nucleus. In the conidial apparatus, the dimensions of the coenocytic conidiophore, like the hyphae, are unaffected by ploidy, while the uninucleate sterigmata are larger in the diploid. In the case of the primary sterigmata, however, the volume in the diploid is less than twice that in the haploid, suggesting that the mechanism controlling cytoplasmic volume is not fully operative at this stage.

Spore dispersal in Alternaria porri (Ellis) Neerg. on onions in Nebraska

SUMMARYIn spore‐trapping studies in 1965, conidia of Alternaria porri (Ellis) Neerg. were detected in the atmosphere immediately above onions affected by purple blotch disease. On calm summer days, peak conidium concentration occurred between 08.00 and 14.00 hr., few conidia being trapped between 20.00 and 06.00 hr. On windy days, there were marked increases in concentration. Concentration tended to increase with increasing wind velocity. Increased conidium concentrations were also recorded after rainfall and irrigation, and during spraying operations.Laboratory observations indicate that in A. porri, the attachment of conidium to conidiophore is weakened, if not broken, by movements in the conidial apparatus which occur in response to a decrease in vapour pressure.Possible causes of fluctuations in atmospheric content of A. porri conidia are discussed.

Observations on dual phenomenon in Aspergillus

Two soil-inhabiting strains ofAspergillus niger van Tieghem have been found to showDual phenomenon, i.e., separation of the thallus into M-, C-and MC-types. Temperature of incubation has been found to effect such changes in the thallus and governs the pattern of separation. MC-type of one of the strains has a tendency to change its normal conidial apparatus to a state where thick-walled, smooth and hyaline bodies are produced in chains directly from the hyphal tips. A naturally occurring soilMycelia sterilia has been found to be identical with M-type of one of the strains.

Aspergillus gracilis Bainier var. sartoryi (Biourge) Batista, Lima and Vital n. var.; phylogenetic importance

We deal with a new variety ofAspergillus which we callAspergillus gracilis Bainiervar. sartoryi (Biourge) Batista, Lima and Vital. This variety appears to be very important under the phylogenetic point of view, apparently being an intermediate form betweenAspergillus andPenicillium. Its morphology resemblesA. gracilis but the conidia characteristics are distinct; we took the epithetsartoryi fromA. sartoryi Biourge which was not described by the respective author. We suggest, too, the transfer of the seriesA. restrictus, where we put our new variety, from the groupA. glaucus, to become independant, as a connective series in the phylogenetic development betweenAspergillus andPenicillium, since the type of the series and the other elements that it embraces does not produce sclerotia or cleistothecia and the conidial apparatus offers curious similarity toPenicillium. Besides, some fungi of the series grow well in certain culture media, in complete discordance with the members of the groupA. glaucus.

Conidia of Acrospermum compressum and A. graminum

Acrospermum compressum and A. graminum , which have earlier been considered as synonyms, produce different types of conidial apparatus in culture. A. compressum forms two-celled conidia, whilst A. graminum forms unicellular conidia.

A Dactylella with Conidia Resembling those of Dactylella Stenobrocha in Size and Shape

Several maizemeal-agar plate cultures, which, after being overgrown with mycelium of Pythium mamillatum Meurs, had been further planted with small quantities of leaf mold collected in deciduous woods near Newport News, Virginia, on October 15, 1948, became abundantly infested in about ten days with free-living nematodes as well as with different species of Amoebae and testaceous rhizopods. In all the cultures the eelworms then began to suffer losses from the capture and destruction of many individuals by the predacious hyphomycete I described earlier (2: 508-513) as Dactylella gephyropaga. After this hyphomycete had extended its mycelium throughout the substratum it continued for weeks to destroy eelworms and to produce conidia on its sparsely scattered conidiophores. Two of the cultures on being examined 35 days after the leaf mold had been added showed, besides, in areas near the deposits of forest detritus some development of erect conidio? phores that bore solitary conidia manifestly alien not only to Dacty? lella gephyropaga but also to all congeneric species hitherto made known. During the ensuing weeks the new fungus gradually spread over both of the aging cultures, putting forth additional conidial apparatus rather sparingly though in ample quantity for study. The colorless procumbent mycelial fllaments (fig. 1, A-D: a) from which the erect conidiophores (fig. 1, A-D: b) of the new

Studies on some diseases of sainfoin ( Onobrychis sativa) : II. The life history of Ramularia onobrychidis Allescher

Summary Ramularia onobrychidis causes a leaf spot of sainfoin in Glamorgan, Wales. In field material, chains of conidia are produced on conidiophores of sub-stomatal sporodochia from late spring to early autumn. Conidia vary from phragmospores through didymospores to amerospores; moist conditions promote the formation of shorter conidia with fewer septa, and very dry conditions some longer, somewhat narrower conidia with up to four septa. Sclerotia develop in winter in the substomatal cavities and are arranged usually in a ring around an old spot. They germinate very readily in the field under moist conditions without any resting period and retain their viability for at least nine months indoors, when kept dry. Sclerotia consist essentially of a more or less globose ‘body’ of homogeneous plectenchy-matic cells with brown and slightly thickened walls, and a ‘neck’ of regularly columnar cells. It is from the apices of these neck cells that conidiophores arise. Sclerotia store oil, which disappears during the production of a single crop of conidia. Single spore isolations of the different spore forms from summer spots and from germinating sclerotia have given similar cultures. The disease was reproduced with difficulty when healthy sainfoin leaflets were inoculated with spore suspensions and R. onobrychidis was re-isolated from the spots. No perithecial stage in the life history has been discovered and it is probable that the fungus overwinters, in South Wales, by means of its sclerotia. A (?)pycnidial form, found near spots caused by Ramularia may represent the slimy conidial apparatus. The fate of the original species of Ramularia is discussed and a history of the genus is given.