6 Wood Discoloration

2.5 Classification 47
Fatty acid profiles
Microorganisms synthesize over 200 different fatty acids. The presence of
specific acids and their relative amounts are constant for a particular species.
Since the 1960s, bacteria and fungi are identified by gas chromatographic
analysis of fatty acids, which were previously derivatized to methyl esters. The
technique has also been used to identify wood-decay fungi like Phanerochaete
chrysosporium, P. sordaria, Trametes versicolor, T. hirsuta,andT. pubescens
(Diehl et al. 2003).
MALDI-TOF mass spectrometry
The technique of matrix-assisted laser desorption/ionization time-of-flight
mass spectrometry (MALDI-TOF MS) was developed in the 1980s, and was
used in many fields for peptide, protein, and nucleic acid analyses (Jürgens
2004; Welker et al. 2004). The method was suitable to differentiate and identify
viruses, bacteria, and fungi (yeasts and Deuteromycetes) (e.g., Fenselau and
Demirev 2001). In MALDI-TOF MS, biomolecules and even whole cells are
embedded in a crystal of matrix molecules, which absorb the energy of a laser.
The sample is ionized by means of the matrix, and both the matrix and the
analyte are transferred to the gas phase. The ions are accelerated in an electric
field, and their time of flight is determined in a detector. After calibration of the
instrument with molecules of known mass, the flight time of the analyte ions
is converted to mass-to-charge ratios (m/z). Organism-specific signal patterns
(“fingerprints”) in the mass range 2,000–20,000 Da were obtained. Figure 2.24
shows the first MALDI-TOF MS fingerprints of Basidiomycetes, namely the
closely related sister taxa Serpula lacrymans, S. himantioides and Coniophora
puteana, C. marmorata (Schmidt and Kallow 2005). The obtained spectra may
be used for subsequent diagnosis of unknown fungal samples by comparison.
2.5
Classification
Approximately 120,000 fungal species are described. If the numerical ratio
between vascular plants and fungi of 1:6 in botanically well-examined regions,
like Great Britain, however, is transferred to a global scale of 270,000 vascular
plants, 1.6 million fungi might exist. That is, so far only about 10% of the
actual fungal species are described (Anonymous 1992b). Robson (1999) even
estimated 3 million fungal species.
Nomenclature regulates the constitution of names, their validity, legitimacy
and priority or synonymy, and maintains a single correct name for each taxon
(International Code of Botanical Nomenclature, St. Louis Code 2000). In view
of the author names for fungi, these have to be only abbreviated when more
than two letters are saved. Names are always abbreviated between a conso-
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