Biological Applications

Biological applications encompass a potentially broad area ranging from the analysis of biopolymers and lower unicellular or multicellular organisms, to plant and animal tissues or even whole ecological systems. Most of this vast area still remains unexplored by pyrolytic techniques. The analysis of biopolymer preparations (refs. 46 - 48) and the differentiation of yeasts and fungi (refs. 70, 167 - 169) represent areas where Py-MS techniques have made some progress. Classification of fungi presents challenging problems in view of the inaccessibility of some types of fungi to conventional morphological classification techniques. Examples are the differentiation of Endogonaaeae species reported by Weijman and Meuzelaar (ref. 170) using Curie-point Py-MS, and the characterization of rust spores, including the economically highly important coffee rust Hemileia vastatrix by Meuzelaar (ref. 171). A Curie-point Py-MS spectrum of Hemileia vastatrix is shown in Figure 44. Analysis of this spectrum reveals the presence of considerable amounts of N-acetylami-no sugar fragments, probably originating mainly from chitin (see Atlas) localised in the spores, which could point the way to new approaches towards coffee rust control. As already mentioned in Section 6.7, factor analysis techniques have been used for the comparative analysis of pyrolysis mass spectra of yeasts and provide a powerful method for chemotaxonomic studies of yeast species.

Boon et al. (ref. 172) studied the variations in the cell wall composition of Baaillus subtilis resulting from differences in the composition of the culturing medium. The microorganism synthesises the acidic polysaccharide teichoic acid when grown in a phosphate-rich environment, whereas under phosphate limiting conditions mainly the phosphorus-free polysaccharide teichuronic acid is produced. These differences in cell wall compositions become directly clear on Py-MS analysis of the complete cells or of the isolated cell walls. Py-MS is also a valid tool for studying the biodégradation of organic matter in sediments, as was demonstrated in a study of sediment digestion by the lugworm Areniaola marina in a benthic marine ecosystem (ref. 173).

An intriguing application of pyrolysis techniques in the detection of plant diseases was reported by Myers and Watson in 1969 (ref. 174) and more recently by Marais and Kotzé (ref. 175). Using Py-GC techniques, these authors detected characteristic changes in the pyrolysis patterns of whole plant tissues diagnostic of a

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