History of classification
The history of the classification of bacteria clearly demonstrates that changes were caused by the availability of new techniques (Table 1). The late 19th century was the beginning of bacterial taxonomy and Ferdinand Cohn in 1872 was the first to classify six genera of bacteria (as members of the plants) mainly based on their morphology. However, at that time, the majority of scientists were interested in the description of pathogenic bacteria. Actually, many of the pathogenic bacteria known today were described between 1880 and 1900. At that time, besides morphology, growth requirements and pathogenic potential were the most important taxonomic markers .
At the beginning of the 20th century more and more physiological and biochemical data were used, in addition to morphology, as important markers for the classification and identification of microorganisms. Numerous biochemical and physiological properties of bacterial cultures were determined for their characterization and identification. Later, enzymes were studied and metabolic pathways were elucidated. The first