Speaker: Mathias Grote, Technische Universitt Berlin - Neither natural, nor species? Ways of classifying in 20th century microbiology

Bacteria have often been considered a tough case for biological classification due to their variability and a lack of morphological characters. Moreover, an accepted method for a phylogenetic (evolutionary) classification has arisen only recently on the basis of microbial genomics. As microbiology has been quite a successful field of science since the days of Louis Pasteur and Robert Koch, one may ask how microbiologists have actually classified their objects before the age of DNA sequencing. In this talk, I will follow the development of microbial classification closely on the level of experimental practices (culturing techniques, diagnostic tests), the rules and conventions needed to implement specific ways of classifying (nomenclature, manuals), as well as the influence of fields such as botany, medical bacteriology or statistics. It will become clear that bacterial classification was (and probably still is) a scientific activity that has established the grid of nature between the laboratory, clinic and the field through carefully negotiating novel results with existing data. Moreover, there has never been any consensus on the mode of doing it right.Non-phylogenetic modes of classifying bacteria (such as based on overall similarity or the organisms ecology) have been important for most of the 20th century and even nowadays, the status of DNA-based phylogeny for classification remains disputed. This allows me to ask the philosophical question of the relevance and place of evolution in biological classification. Is a phylogenetic classification the only scientific way of putting bacteria in order?