Book of Abstracts (PDF) - International Mycological Association

IMC7 Main Congress Theme V: CELL BIOLOGY AND PHYSIOLOGY Posters
1099 - Demonstration of DHN-melanin pathway and
genetic analysis of the gene encoding scytalone
dehydratase in sapstain fungi
C. Fleet 1 , C. Breuil 1 & A. Uzunovic 2*
1 University of British Columbia, Dept. of Wood Science,
Vancouver, B.C., Canada. - 2 Forintek Canada Corp., 2665
East Mall, Vancouver, B.C., Canada. - E-mail:
adnan@van.forintek.ca
The presence of the 1,8-dihydroxynaphthalene (DHN)
melanin biosynthesis pathway was demonstrated in several
sapstain fungi using both chemical inhibitors and molecular
techniques. The inhibitor compounds tricyclazole and
carpropamid effectively reduced pigmentation at low
concentrations in all tested fungal species, but also lead to
growth inhibition at higher concentrations. The inhibitor
cerulenin prevented fungal growth in all tested fungi at all
tested concentrations, likely due to its inhibitory effect on
another enzyme, the metabolically critical fatty acid
synthase. Partial DNA sequences for the gene encoding
scytalone dehydratase (SD) were obtained from species of
Ceratocystis and Ophiostoma and found to have homology
with known respective DHN-SD gene sequences. Sequence
analysis of the partial SD amino acid sequences showed
greater than 80% similarity among the sapstain species, and
corresponded well with known phylogenies of sapstain
fungi based on rDNA sequences. Aside from the work
carried out on the isolate O. floccosum 387N, this is the
first known documentation of the melanin pigmentation
pathway used by species of the sapstain fungi from
Ceratocystis, Leptographium and Ophiostoma (Eagen et.
al. 2001, Wang et al. 2001, Wang and Breuil submitted).
Furthermore, since no fungus has ever been found, to our
knowledge, to have more than one melanin synthesis
pathway, we can state that these species likely only use the
DHN pathway for melanin production.
1100 - Clay effects on the fungal growth morphology
and copper sorption ability
M. Fomina * & G.M. Gadd
Division of Environmental and Applied Biology, Biological
Sciences Institute, School of Life Sciences, University of
Dundee, Dundee DD1 4HN, Scotland, U.K. - E-mail:
m.fomina@dundee.ac.uk
As a prelude to the development of biomineral sorbents for
toxic metals, this study assesses the influence of clay
minerals (bentonite, kaolinite and palygorskite) on the
morphology of mycelial pellets produced by melaninforming
microfungi and on the copper sorption properties
of fungal/clay mixtures. In general, a reduction of pellet
size, an increase in the length of surface hyphae of the
pellets, and a reduction in exopolymer production were
observed with increasing clay mineral concentrations up to
5%(w/v). It was found that the clay particles were involved
in the development of pellet structure of Cladosporium
cladosporioides at all stages of growth. A general model of
the structure of a fungal pellet grown in clay-containing
medium is proposed. The pellets consist of three main
layers: a central core with densely packed mycelium
aggregated with solid clay minerals or a matrix of
clay/polysaccharides; a middle layer with looser mycelium
mixed with clay mineral flakes; and an outer, or 'hairy'
zone, with loose hyphae surrounded by clay mineral flakes.
A study of equilibrium Cu uptake from pH-buffered
solutions showed that bentonite addition to the medium
increased the sorption of Cu by Aureobasidium pullulans
and C. cladosporioides grown in this medium. The
mechanism of changed sorption capacity of the combined
biomineral sorbents is suggested to occur by blocking or
modification of binding sites on biotic and abiotic
components of the 'biomineral' association.
1101 - Effect of nutrient resources on growth and
morphology of fungal mycelia penetrating toxic metal
domains
M. Fomina 1* , K. Ritz 2 & G.M. Gadd 1
1 Department of Environmental and Applied Biology,
Biological Sciences Institute, School of Life Sciences,
University of Dundee, Dundee, DD1 4HN, Scotland, U.K. -
2 National Soil Resources Institute, Cranfield University,
Silsoe, MK45 4DT, England, U.K. - E-mail:
m.fomina@dundee.ac.uk
Natural environments contain a heterogeneous distribution
of metal concentrations, and the ability of fungi to colonise
such metal-contaminated domains will be influenced by the
resources available to fungi. The aim of this study was to
investigate the growth responses of some common soil
fungi (Trichoderma viride and Gliocladium roseum)
towards copper and cadmium under different nutritional
conditions and using a system of tessellated agar tiles. The
growth parameters recorded in this study demonstrated a
decrease in metal toxicity with increasing concentration of
available carbon source. It was shown that maximum
extension rates and efficacy of carbon substrate utilization
of both cultures decreased with increasing concentration of
toxic metals. It was observed that in the gap between
metal-free tiles and metal-containing tiles, the presence of
the toxic metals led to negative chemotropic reactions and
stopping of growth, swelling and lysis of some hyphal tips.
Penetration of the hyphae into the metal-containing domain
was often followed by the formation of very dense
mycelium or mycelial 'bushes'. After fungi entered the
toxic metal-containing domain, they often produced long
sparsely-branched or branchless explorative hyphae. Our
data have demonstrated that fungi efficiently use both
'phalanx' and 'guerrilla' states of the mycelial system as a
response to toxic metal stress combined with nutritionallypoor
conditions.
Book of Abstracts 333