Handbook Part 2 - International Mycological Association

POSTER ABSTRACTS S4
POSTER SESSION 4: CELL BIOLOGY AND PHYSIOLOGY
PS4-386-0019
Becoming less protected;germination of highly stress-resistant ascospores of Talaromyces macrosporus
includes unique cellular features.
J. Dijksterhuis 1, R.A. Samson1, H.A.B. Wösten 2, E. Golovina 3, F.A. Hoekstra 3, L. Lugones 2
1 Centraalbureau voor Schimmelcultures, Utrecht, Netherlands, 2 Utrecht University, Utrecht, Netherlands, 3
Wageningen University, Wageningen, Netherlands
Ascospores of Talaromyces macrosporus are the most resilient eucaryotic structures described to date. They survive
heat (above 85 ºC), high pressure, and drought. Besides, they show constitutive dormancy and are triggered to
germinate by a heat treatment at 85 ºC. This contribution addresses activation of the spores to germination and the
changes inside the cell during early germination. Upon heat activation changes in the cell wall were observed with
different techniques. For example, fluorescence microscopy indicated a change in the permeability of the cell wall.
Electron paramagnetic resonance studies showed that the viscosity inside the cells is extremely high. Early
germination was characterised by low respiration, trehalose degradation and glucose release, but high viscosity
remained. Then, a sudden ejection of the inner cell through the outer, very thick, ascospore cell wall was observed.
The latter process was dubbed prosilition. Cryo-planing and scanning electron microscopy exhibited a connection
between the ejected cell and the emptied outer cell wall. Prosilition is thought to be important for renormalisation of
the spore while respiration increased strongly and cell viscosity dropped to a normal level.
Activation by high temperature was associated with the release of large amounts of a small protein from the cell
(wall). This protein was estimated as being the single dominant protein of ascospores and responsible for 5% or more
of the amount of protein of these cells. After terminal amino acid characterisation, we constructed a degenerative
primer and after (RACE)-PCR, the sequence of a small protein (called PLAY) was obtained and it contained one short
intron. The genome of Talaromyces macrosporus contained one copy of this gene and its expression as judged by
Northern blotting was strictly related to the formation of fruit bodies (that contain ascospores). Further research will be
done to evaluate its role in dormancy and heat-resistance.
Knowledge on the behaviour of these highly stress-resistant cell is related to protection mechanisms of biological
compounds and the identification of novel cell wall components (proteins). Furthermore, the ascospore is still a
relatively scarcely studied, but abundantly present fungal structure and its study might reveal new basic principles of
fungal biology.
PS4-388-0033
Extracellular enzymes from thermophilic fungi
Raj K. Salar
Department of Biotechnology, Chaudhary Devi Lal University, Sirsa - 125 055, Haryana, India
Thermophilic fungi comprise a small ecological group defined solely on temperature requirement for growth, ranging
between 200C to > 500C. There are about 40 known species of fungi, which have been characterized. Many bacteria
and Archaea from thermal habitats have been explored for the industry, and have provided it with the thermoactive
enzymes. In contrast fungal enzymes are much more acid tolerant than the bacterial enzyme which is an important
factor for many industries. In the present investigation 29 species of thermophilic and thermotolerant fungi belonging
to 14 genera were isolated from north Indian soils. These species were screened for their growth characteristics and
ability to produce extracellular amylase, exo-glucanase, endo-glucanase, b-glucosidase, lipase, and xylanase. Of
these 29, 4 species (Chaetomium thermophile, Thermomyces lanuginosus, Malbranchea sulfurea and Scytalidium
thermophilum) were selected to study enzyme production using different substrates. M. sulfurea exhibited maximum
amylase activity (0.22+0.005 U ml-1). Wheat straw (WS) and alkali treated wheat straw (AWS) was used to compare
the production of exo-glucanase, endo-glucanase, and b-glucosidase. S. thermophilum produced highest exoglucanase
activity, 259.4+0.5 IU ml-1 and 148+5.7 IU ml-1 on WS and AWS respectively. Highest endo-glucanase activity
was also shown by S. thermophilum being 230.2+1.7 IU ml-1 and 175.1+1.5 IU ml-1 on WS and AWS respectively.
However, b-glucosidase production was highest in the culture filtrates of C. thermophile. Similarly maximum lipase
activity was observed in the culture filtrates of M. sulfurea (92.0+8.1 IU ml-1). Maximum xylanase activity was shown by
C. thermophile and M. sulfurea on xylose containing media being 0.82+0.14 IU ml-1 and 0.81+0.11 IU ml-1 respectively.
In the present investigation, it was realized ‘Do fungal growth profiles correlate with enzyme characteristics?’ This
question is of interest both from academic and industrial point of view and can be enlighted with thermorelated
studies.
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