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Jan Dijksterhuis

Publications and source records attributed to Jan Dijksterhuis.

7 recordsLinked to original sources
PubMed2006

Compatible solutes and fungal development.

Compatible solutes are components that can be quickly accumulated and degraded inside fungal cells. They do not disturb the functioning of proteins and protect the cell under adverse conditions. In this issue of the Biochemical Journal, Solomon and co-workers evaluate the role of mannitol, one of these components, in Stagonospora nodorum, a plant-pathogenic fungus, and find surprising effects on the development of spores and spore-forming structures.

Mannitol↗
PubMed2005

1-Octen-3-ol inhibits conidia germination of Penicillium paneum despite of mild effects on membrane permeability, respiration, intracellular pH, and changes the protein composition.

1-Octen-3-ol is a volatile germination self-inhibitor produced by Penicillium paneum that blocks the germination process. The size of conidia treated with 1-octen-3-ol was similar to that of freshly harvested conidia. Exposure to 1-octen-3-ol resulted in staining of 10-20% of the conidia with PI and TOTO, fluorescent DNA probes that cannot enter cells with an intact membrane, whereas only 3-5% of non-treated conidia were stained. Addition of 1-octen-3-ol to germinating conidia resulted in transient dissipation of the pH gradient. From this, we conclude that slight permeabilisation of the fungal membrane occurs in the presence of the inhibitor. Two-dimensional gel electrophoresis analysis of protein patterns revealed striking differences between non-germinated conidia, germinated conidia and 1-octen-3-ol-treated conidia. In conclusion, 1-octen-3-ol has mild effects on the plasma membrane, but interferes with essential metabolic processes, such as swelling and germination of the conidia, but in a reversible manner.

Cell Membrane Permeability↗
PubMed2005

Differentiation inside multicelled macroconidia of Fusarium culmorum during early germination.

Multicelled conidia are formed by many fungal species, but germination of these spores is scarcely studied. Here, the germination and the effects of antimicrobials on multicompartment macroconidia of Fusarium culmorum were investigated. Germ-tube formation was mostly from apical compartments. The intracellular pH (pH(in)) of the different individual cells of the macroconidia was monitored during germination. The pH(in) varied among different compartments and during different stages of germination. The internal pH was lowest in ungerminated cells and rose during germ-tube formation and was highest in new germ tubes. Antifungal compounds affect the pH(in) and differentiation of the conidia. The pH(in) inside the macroconidial compartments was lowered very fast in the presence of nystatin (1 and 4 microg/ml). At sublethal doses (0.3 microg/ml), the apical compartments were preferentially targeted showing lower pH(in) values. The reduced germination capacity of apical compartments under these conditions was compensated by an increased germination capacity of middle compartments.

Fusarium↗
PubMed2004

Germination of penicillium paneum Conidia is regulated by 1-octen-3-ol, a volatile self-inhibitor.

Penicillium paneum is an important contaminant of cereal grains which is able to grow at low temperature, low pH, high levels of carbon dioxide, and under acid conditions. P. paneum produces mycotoxins, which may be harmful to animals and humans. We found that conidia in dense suspensions showed poor germination, suggesting the presence of a self-inhibitor. A volatile compound(s) produced by these high-density conditions also inhibited mycelial growth of different species of fungi belonging to a variety of genera, suggesting a broad action range. The heat-stable compound was isolated by successive centrifugation of the supernatant obtained from spore suspensions with a density of 10(9) conidia ml(-1). By using static headspace analyses, two major peaks were distinguished, with the highest production of these metabolites after 22 h of incubation at 25 degrees C and shaking at 140 rpm. Gas chromatography coupled with mass spectra analysis revealed the compounds to be 3-octanone and 1-octen-3-ol. Notably, only the latter compound appeared to block the germination process at different developmental stages of the conidia (swelling and germ tube formation). In this study, 1-octen-3-ol influenced different developmental processes during the P. paneum life cycle, including induction of microcycle conidiation and inhibition of spore germination. Therefore, the compound can be considered a fungal hormone during fungal development.

Culture Media↗
PubMed2002

Trehalose degradation and glucose efflux precede cell ejection during germination of heat-resistant ascospores of Talaromyces macrosporus.

Talaromyces macrosporus forms ascospores that survive pasteurization treatments. Ascospores were dense (1.3 g ml(-1)), relatively dry [0.6 g H(2)O (g dry weight)(-1)] and packed with trehalose (9-17% fresh weight). Trehalose was degraded to glucose monomers between 30 and 100 min after heat activation of the spores. The maximal activity of trehalase was calculated as 400-520 nmol glucose formed min(-1) (mg protein)(-1) as judged by measurements of the trehalose content of spores during germination. During early germination, glucose was released from the cell (10% of the cell weight or more). The intracellular concentration of glucose only peaked briefly. After 160-200 min, the protoplast encompassed by the inner cell wall was ejected through the outer cell wall in a very quick process. Subsequently, respiration of spores increased strongly. The data suggested that trehalose is primarily present for the protection of cell components as glucose is released from the cell. Then, an impenetrable outer cell wall is shed before metabolic activity increases.

Ascomycota↗
PubMed2002

Aspergillus oryzae in solid-state and submerged fermentations. Progress report on a multi-disciplinary project.

We report the progress of a multi-disciplinary research project on solid-state fermentation (SSF) of the filamentous fungus Aspergillus oryzae. The molecular and physiological aspects of the fungus in submerged fermentation (SmF) and SSF are compared and we observe a number of differences correlated with the different growth conditions. First, the aerial hyphae which occur only in SSFs are mainly responsible for oxygen uptake. Second, SSF is characterised by gradients in temperature, water activity and nutrient concentration, and inside the hyphae different polyols are accumulating. Third, pelleted growth in SmF and mycelial growth in SSF show different gene expression and protein secretion patterns. With this approach we aim to expand our knowledge of mechanisms of fungal growth on solid substrates and to exploit the biotechnological applications.

Aspergillus oryzae↗