Current classification
It has to be emphasized that there is still no officially recognized system for the classification of prokaryotes. The currently applied classification systems rely – for practical reasons – on methods and do not depend on theoretical concepts. The most widely used system is the so-called polyphasic approach [43]. This approach includes phenotypic, chemotaxonomic and genotypic data, as well as phylogenetic information. 16S rRNA gene sequencing is applied for determining the phyloge-netic position of the organisms. Based on these results, organisms are selected for DDH studies and species are defined using the 70% DDH cut-off criterion [44]. Each taxon should be described and differentiated from related taxa by its phenotypic, chemotaxonomic and