6 Wood Discoloration

2.4 Identification 33
2.4.2
Molecular Methods
Molecular methods to characterize, identify, and classify organisms do not
depend on the subjective judgment of a human being as it might occur using
classical methods, but are based on the objective information (molecules)
deriving from the target organism. Thus, molecular methods are increasingly
used to identify organisms and for taxonomy research (molecular systematic).
In the 1980s, molecular methods were established for wood-decay and staining
fungi. Mainly, the fungal proteins (enzymes) and nucleic acids are used. It is
outside the intention of this book to describe all molecular techniques that are
currently used in the field of biology. The following overview comprises only
some methods and results that are related to the characterization, identification,
and phylogeny of wood-inhabiting fungi, particularly wood-decay fungi.
Genome sequencing (meanwhile over 100 genomes are sequenced), molecular
engineering, cloning, etc. are briefly addressed in other chapters. As an example
of the latter, Lee et al. (2002) transformed the wild-type and the albino
strain of the blue-stain fungus Ophiostoma piliferum with a green fluorescent
protein (GFP) to microscopically differentiate the GPF-expressing fungi from
other fungi in wood.
2.4.2.1
Protein-Based Techniques
SDS polyacrylamide gel electrophoresis (SDS-PAGE)
In SDS-PAGE, the whole cell protein is extracted from fungal tissue, denatured,
and negatively charged with mercaptoethanol and sodium dodecyl sulfate
(SDS). The proteins are separated according to size on acrylamide gels and
visualized by Coomassie blue, amido black, fast green, imidazole-zinc or silver
staining. The banding pattern obtained discriminates at the species level and
slightly below.
SDS-PAGE was used for wood-inhabiting Ascomycetes and Deuteromycetes
like the Cancer stain disease fungus of plane, Ceratocystis fimbriata f. platani,
(Granata et al. 1992) and Trichoderma species (Wallace et al. 1992).
The technique also differentiated a number of wood-decay fungi (Schmidt
and Kebernik 1989; Vigrow et al. 1989, 1991a; Schmidt and Moreth-Kebernik
1991a, 1993; Palfreyman et al. 1991; McDowell et al. 1992; Schmidt and Moreth
1995). For example, the closely related Serpula lacrymans, S. himantioides and
the “American dry rot fungus”, Meruliporia incrassata, weredistinguished
(Schmidt and Moreth-Kebernik 1989a). Figure 2.19 shows that the technique
also detected a misnamed isolate of S. lacrymans.
In addition, monokaryons and F1 dikaryons of S. lacrymans exhibited the
typical species profile (Schmidt and Moreth-Kebernik 1990). There was no need
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