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Chapter 36 : Systematic Challenges
Microbiology in Munich was headed by Otto Kandler, a botanist and microbiologist whose scientific emphasis in microbiology was on the physiology and taxonomy of gram-positive bacteria. Previous analysis of peptidoglycan already pointed toward the discrepancy between classification based on classical phenotypic properties and grouping according to chemotaxonomy. A logical next step was to investigate the taxonomic potential of other characteristics, such as the qualitative and quantitative formation of ethanol, acetate, and lactic acid and the reconstruction of the glycolytic and the pentose phosphate pathways. The results of this study had no major impact on one's understanding of the relationships among the coryneform bacteria. The author spent years to understand that all the approaches used in taxonomic studies were different jigsaw puzzles using pieces that did not yet fit together. The rate of evolution between the genotype (as measured by the 16S rDNA) and the phenotype (representing many different genes) does not run isochronically, and clusters defined by high 16S rDNA similarity values may show significant differences in phenotype, which does not necessarily correlate with results of DNA reassociation studies. The introduction of molecular sequencing into systematics and the consequent stability of prokaryotic taxa raised the interest of scientists from different bacteriological disciplines. Derived and catalyzed by the development of polymerase chain reaction (PCR) technology, diagnostic methods were developed that began to change bacterial identification in natural samples. The last twenty years have witnessed radical changes in one's understanding about the role and importance of prokaryotic organisms.