prog detail - International Mycological Association

S37IS2 - 0486
Visualization of the endocytic pathway and endosomal structures in the filamentous fungus Aspergillus
oryzae
Y Higuchi, T Nakahama, JY Shoji, M Arioka, K Kitamoto
Department of Biotechnology, The University of Tokyo, Tokyo, Japan
Endocytosis is an important process for cellular activities. However, in filamentous fungi, the existence of endocytosis
has been so far elusive. In this study, we used AoUapC-EGFP, the fusion protein of a putative uric acid-xanthine
permease with EGFP (enhanced green fluorescent protein) in the filamentous fungus Aspergillus oryzae, to examine
whether the endocytic process occurs or not. Upon the addition of ammonium into the medium the fusion protein was
internalized from the plasma membrane. The internalization of AoUapC-EGFP was completely blocked by sodium
azide, cold, and cytochalasin A treatments, suggesting that the internalization possesses the general features of
endocytosis. These results demonstrate the occurrence of endocytosis in filamentous fungi. Moreover, we discovered
the endosomal compartments that appeared upon the induction of endocytosis. The endosomal compartments
displayed intermittent and bidirectional movement longitudinally along the hyphae, in a microtubule-dependent
manner. Effects of the deletion of the motor proteins will be also included in the presentation.
S37IS3 - 0727
Network structyure and dynamics of fungal mycelia
D P Bebber 1, J Hynes 2, P R Darrah 1, L Boddy 2, M D Fricker 1
1. University of Oxford, Oxford, UK
2. University of Cardiff, Wales, UK
Many physical phenomena, from road systems to the internet, can be modelled as networks. Network analyses have
revealed important properties of, and commonalities among, diverse experimental structures. The fungal mycelium is
a transport network that competes in a complex and changing environment. The architecture of the network
continuously adapts to local nutritional or environmental cues, damage or predation, through growth, branching,
fusion and regression. We investigate whether mycelial network architecture optimizes resource capture, exploration,
translocation, or defence.
We use image analysis techniques to digitize the growing mycelia of cord-forming saprotrophic fungi, and to assign
transport capacities and physical resiliences to the cords (Fig. 1). These models are then analysed using a variety of
network-based statistics. We compare modelled transport capacity and routing with real values derived from
scintillation imaging of radiolabelled mycelia, and compare in silico attack with responses of real mycelia to
experimental attack by fungivorous collembola.
As the mycelium grows, some cords thicken to increase transport capacity, such that the network’s effective diameter
remains static even as its physical size increases. We term this property a ‘physiological small world’ effect. Differential
cord thickening also increases the resilience of the network to attack, by protecting a central core component at the
expense of weaker peripheral cords. The network responds to actual physical damage by increasing redundancy in
transport routes.
Our analyses have revealed that the fungal mycelium is a self-organised network that balances transport and
defence. Further investigation of variation in mycelial structure among fungal species may reveal trade-offs between
properties such as exploration and resilience, and suggest adaptations to different ecological niches. Network theory
provides a new and exciting way of understanding fungal biology and ecology.
S37PS1
Advanced microscopic imaging coupled with x-ray absorption spectroscopy to characterise fungal metal
and mineral transformations
Geoffrey M. Gadd 1, John Charnock 2, Andrew D. Bowen 1 and Marina Fomina 1
1 Division of Environmental and Applied Biology, Biological Sciences Institute, College of Life Sciences, University of
Dundee, Dundee, DD1 4HN, UK 2 SRS Daresbury Laboratory, Daresbury, Warrington, WA4 4AD, UK
In this study, scanning electron microscopy (SEM)-based techniques were used to study metal-mineral transformations
by fungi, especially the formation of mycogenic minerals, while X-ray absorption spectroscopy (XAS) was used to
determine the speciation of metals within biomass. It was found that fungal-mineral interactions at the microscale
level could be successfully studied using different SEM approaches which preserved living fungal microstructures and
the microenvironment where the precipitation of mycogenic minerals occurred. Environmental scanning electron
microscopy (ESEM) in the wet mode was the best method for observing such interactions in their natural
microenvironment; X-ray element mapping demonstrated sequestration and localization of metals. Cryo-SEM allowed
the observation of both interior and exterior morphology and appeared to preserve the complex structure of
ectomycorrhizal roots better than other microscopic techniques. The amorphous state or poor crystallinity of metal
complexes within the biomass and relatively low metal concentrations makes the determination of the metal
speciation a challenging problem but this can be overcome by using synchrotron-based element-specific XAS
techniques. Here, we exposed fungi and ectomycorrhizas to a variety of copper-, zinc- and lead-containing minerals.
XAS revealed that oxygen ligands (phosphate, carboxylate) played a major role in toxic metal coordination within
fungal biomass during the accumulation of mobilized toxic metals. The use of state-of-the-art SEM techniques and
XAS has provided new information about the role of fungi in metal-mineral transformations and their importance in
“geomycological” processes.
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