Formation of conidia by Aspergillus and Penicillium. (A) Aspergillus (left graph) and Penicillium (right graph) form distinct conidiophores. (B) Morphological features of the Penicillium conidiophore used in species determination. Scanning Electron Microscopy (SEM) micrographs of conidiophores of A. niger (C) and P. discolor (E) with the conidia producing phialides located on the vesicle (D) or within the penicillus (F), respectively. Bar represents 10 µm.

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... the order Eurotiales, within the phylum of Ascomycota ( Frisvad and Samson, 2004;Geiser et al., 2007). The fungi are able to form numerous single-celled asexual spores, conidia, on structures that are called conidiophores. Aspergillus forms conidiophores that are characterized by a large thick walled stipe with a swollen apex, termed the vesicle (Fig. 1A). Conidia are formed from flask-shaped phialides that are in many species placed on short branches (metulae) that develop from the vesicle. The conidia are produced in chains by basipetal succession: the youngest conidium is formed at the base, pressing the older conidia further away from the phialide. Conidiophores of Penicillium also ...

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... produced in chains by basipetal succession: the youngest conidium is formed at the base, pressing the older conidia further away from the phialide. Conidiophores of Penicillium also consist of a single stipe. This stipe terminates into a whorl of conidia-producing phialides (monoverticilate, e.g. P. glabrum), or more generally, forms a penicillus (Fig. 1). The penicillus consists of metulae bearing the phialides that originate from, one-stage branched (biverticilate), two-staged branched (terverticilate), or three-staged branched (quaterverticilate) aerial hypha (Fig. 1B). Aspergilli and Penicilli are saprophytic and natural habitants of soil and decaying organic matter. They are ...

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... terminates into a whorl of conidia-producing phialides (monoverticilate, e.g. P. glabrum), or more generally, forms a penicillus (Fig. 1). The penicillus consists of metulae bearing the phialides that originate from, one-stage branched (biverticilate), two-staged branched (terverticilate), or three-staged branched (quaterverticilate) aerial hypha (Fig. 1B). Aspergilli and Penicilli are saprophytic and natural habitants of soil and decaying organic matter. They are extremely common as spoilage fungi in foods and in stored commodities such as grains, nuts and spices. Because of their global distribution, species of Aspergillus and Penicillium are competitors in soil and decaying matter, as ...

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... conidia showed no or very faint staining during early stages of germination (designated as stage I cells). After 8 h of germination different staining patterns could be discerned, which are correlated with different stages of germination ( Fig. 1). Stage II was characterized by uniformly distributed low fluorescence around the spore membrane. Stage III exhibited an intensive staining at a restricted site on the plasma membrane representing a "cap", at the presumptive site of germination. The staining of the remainder of the membrane was comparable with stage II. Stage IV cells ...

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... at the presumptive site of germination. The staining of the remainder of the membrane was comparable with stage II. Stage IV cells showed a distinct germ tube possessing an intensively stained cap at the apex. A population of conidia exhibited different staining patterns at a certain time, but the proportion of these patterns varied in time. Fig. 1B shows that the proportion of stage IV cells increased, and that stage I and II cells decreased in number between 6 and 8 h of germination. Stage III cells remained approximately constant in number indicating that germination proceeds at a fixed speed when conidia enter this stage. During stage II, equal values of fluorescence intensity ...

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... of the membrane (see Fig. 2) and to the novel membrane added to the spore due to isotropic growth. We measured ergosterol levels in cells of 5.5 h and 6.5 h in triplo and found levels of 44 and 73 fg/ spore, respectively. The number of caps at 5.5 h of germination was 5% (18 caps in 364 spores) and 28% in case of 6.5 h cells (as extrapolated from Fig. 1). It is stated that 80% of the sterols is free in conidia (of A. niger) that have germinated for 6-7 h (Morozova Filipin is a reliable in situ marker of ergosterol in the plasma membrane et al., 2002). There are also estimations that 60% of the free ergosterol might be present in the plasma membrane of yeasts (Sullivan et al., 2006). ...

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... the MIC for 60 min show 87% and 88% stained cells after nystatin and filipin treatment respectively. However, only 2.6% of the natamycin-incubated conidia were stained and no fluorescence was observed with untreated cells. The effect of filipin and nystatin showed dose and time dependent characteristics as judged from the number of stained cells (Fig. 1B). Nystatin reaches high killing rates especially after longer treatment. Filipin shows more concentrationdependent effects where the number of killed cells increases with concentration (Fig. 1B). Accurate measurements of conidial size during treatment are shown in figure 1C. Control spores exhibited an increase in size (swelling) of 17% ...

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... with untreated cells. The effect of filipin and nystatin showed dose and time dependent characteristics as judged from the number of stained cells (Fig. 1B). Nystatin reaches high killing rates especially after longer treatment. Filipin shows more concentrationdependent effects where the number of killed cells increases with concentration (Fig. 1B). Accurate measurements of conidial size during treatment are shown in figure 1C. Control spores exhibited an increase in size (swelling) of 17% during 1 h of measurement. All polyene-treatments showed effects on spore size, but the 2x MIC treatment with natamycin did not prevent swelling of the spore within 30 min while after 60 min ...

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... shows more concentrationdependent effects where the number of killed cells increases with concentration (Fig. 1B). Accurate measurements of conidial size during treatment are shown in figure 1C. Control spores exhibited an increase in size (swelling) of 17% during 1 h of measurement. ...

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... formation was visualized by cryo SEM (Schubert et al., 2007). This technique does not disrupt the very delicate conidiophores. Aspergillus niger and P. discolor (Fig. 1A, B) form chains of the round single-celled conidia on phialidic (flask-shaped) cells. Verticillium fungicola and F. oxysporum (Fig. 1C, D) form spores in large (spherical) clusters and on the surface of the colony, respectively. Markedly, the spore masses are present amidst the hyphae of the colony and not present as a chain. (An). ESR ...

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... formation was visualized by cryo SEM (Schubert et al., 2007). This technique does not disrupt the very delicate conidiophores. Aspergillus niger and P. discolor (Fig. 1A, B) form chains of the round single-celled conidia on phialidic (flask-shaped) cells. Verticillium fungicola and F. oxysporum (Fig. 1C, D) form spores in large (spherical) clusters and on the surface of the colony, respectively. Markedly, the spore masses are present amidst the hyphae of the colony and not present as a chain. (An). ESR spectra of the conidia contain a central line, flanked by a low-field and high-field line (h 0 , h -1 , and h +1 , respectively) after ...

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... germination of A. niger has a maximal rate between 30 -34°C, with more than 90% germination after 6 h ( Abdel-Rahim and Arbab, 1985). In this study A. niger was grown at 25°C to increase separation of the different stages of germination in time (Fig. 1A). During the first 2 h after addition of medium, the size of the spores increased from 17 to 22.5 µm² (Fig. 1B). The surface area of conidia increased further to 46 µm² between 2 and 6 h. After 6 h, 10% of the germinating conidia had signs of germ tube emergence. By 8 h, over 80% had formed germ tubes (Fig. 1C). In the presence of 10 µM ...

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... of A. niger has a maximal rate between 30 -34°C, with more than 90% germination after 6 h ( Abdel-Rahim and Arbab, 1985). In this study A. niger was grown at 25°C to increase separation of the different stages of germination in time (Fig. 1A). During the first 2 h after addition of medium, the size of the spores increased from 17 to 22.5 µm² (Fig. 1B). The surface area of conidia increased further to 46 µm² between 2 and 6 h. After 6 h, 10% of the germinating conidia had signs of germ tube emergence. By 8 h, over 80% had formed germ tubes (Fig. 1C). In the presence of 10 µM natamycin, the surface area of conidia remained 23 µm² and germ tubes were not formed throughout culturing ...

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... stages of germination in time (Fig. 1A). During the first 2 h after addition of medium, the size of the spores increased from 17 to 22.5 µm² (Fig. 1B). The surface area of conidia increased further to 46 µm² between 2 and 6 h. After 6 h, 10% of the germinating conidia had signs of germ tube emergence. By 8 h, over 80% had formed germ tubes (Fig. 1C). In the presence of 10 µM natamycin, the surface area of conidia remained 23 µm² and germ tubes were not formed throughout culturing (Fig. 1C). At 3 µM natamycin, isotropic swelling did occur, but to a lower extent than the untreated cells. However, no polarization and germ tube formation was observed during the 8 h incubation time ...

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... µm² (Fig. 1B). The surface area of conidia increased further to 46 µm² between 2 and 6 h. After 6 h, 10% of the germinating conidia had signs of germ tube emergence. By 8 h, over 80% had formed germ tubes (Fig. 1C). In the presence of 10 µM natamycin, the surface area of conidia remained 23 µm² and germ tubes were not formed throughout culturing (Fig. 1C). At 3 µM natamycin, isotropic swelling did occur, but to a lower extent than the untreated cells. However, no polarization and germ tube formation was observed during the 8 h incubation time (Fig. 1C). These results show that natamycin can inhibit isotropic growth (at higher concentrations) and polarization and germ tube formation (at ...

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... (Fig. 1C). In the presence of 10 µM natamycin, the surface area of conidia remained 23 µm² and germ tubes were not formed throughout culturing (Fig. 1C). At 3 µM natamycin, isotropic swelling did occur, but to a lower extent than the untreated cells. However, no polarization and germ tube formation was observed during the 8 h incubation time (Fig. 1C). These results show that natamycin can inhibit isotropic growth (at higher concentrations) and polarization and germ tube formation (at low ...

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... be detected by filipin staining in dormant and swollen conidia. However, after 6 h of incubation in medium, a fluorescent cap was observed at the presumptive site of germ tube emergence. The fluorescence intensity of the cap increased as the formation of the germ tube proceeded. This indicates an important role of ergosterol in polarized growth (Fig. 1). Sterols associate with sphingolipids into a liquid ordered phase (L o ) surrounded by largely unsaturated phospholipids in a liquid-disordered (L d ) state. This phase segregation results in the formation of micro-domains or lipid rafts . It has been suggested that the ergosterol-enriched cap functions as a lipid raft and captures ...

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... the micro-array analysis. Interestingly, changes in the mRNA pool were not accompanied by morphological changes. However, central carbon metabolism increased as indicated by the degradation of the compatible solutes trehalose and mannitol and the increase of glycerol and glucose levels. Concomitantly, the microviscosity of the cytoplasm dropped (Fig. 1). Levels of compatible solutes and microviscosity did not change between 2 and 6 h (Chapter 5). During this time interval the extent of differential expression had decreased strongly and every functional category was down-regulated except for genes related to cell cycle and DNA processing. This can be explained by the fact that the ...

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... transcription, protein synthesis and cellular communication/signal transduction. The fact that the amount of differential expression as well as up-regulation of transcripts is low between 2-8 h suggests that there is a relatively loose correlation between the transcriptional program and the timing of morphological development during germination (Fig. ...