6 Wood Discoloration

34 2 Biology
Fig.2.19. Protein bands of Serpula lacrymans isolates (S) after SDS polyacrylamide gel
electrophoresis. H false naming later identified as S. himantioides (from Schmidt 2000)
to extrapolate on a possible influence of culture age or medium composition
(Schmidt and Kebernik 1989).
SDS-PAGE is fast when the sample originates from a pure culture and can
be performed within 1 day. Reproducible homemade gels require accuracy
and precautions, as acrylamide is carcinogenic in the unpolymerized form.
Prefabricated gels are expensive. At least regarding wood-decay fungi, the
method did not reach a practical application.
Isozyme analyses
Isozyme analyses have been used to distinguish similar and closely related
species and forms, for investigations on the genetical variability and on the
spread of pathogens (e.g., Blaich and Esser 1975; Prillinger and Molitoris 1981;
Micales et al. 1992). Being functional proteins, isozymes are investigated by
native electrophoresis or isoelectric focusing. There are a number of investigations
on mycorrhizal fungi, e.g., Pisolithus and Scleroderma species (Sims
et al. 1999) and on tree parasites, like Armillaria species (Bragaloni et al. 1997)
and Heterobasidion annosum (Karlsson and Stenlid 1991).
Two-dimensional gel electrophoresis, comprising isoelectric focusing and
subsequent SDS-PAGE, is able to separate a sample of a large number of proteins.
Immunological methods
Wood fungi can be also detected and identified by immunological (serological)
methods. Immunological assays use polyclonal antisera or monoclonal
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