Taxonomy of the GenusBacillusand Related Genera: The Aerobic Endospore-Forming Bacteria

ABSTRACT The conspicuous morphological feature of endospore formation has lent itself from early on as an easily recognized property for taxonomic differentiation. Prior to 1980, the year of the compilation of the Approved Lists of Bacterial Names, four genera of aerobic endospore-forming bacteria had been established, with the genus Bacillus being the largest and most prominent. However, modern developments in taxonomic methodology have helped to reveal an enormous breadth in physiological and genetical diversity within the groups of aerobic bacteria that have endospore formation as a common trait. To better reflect this existing diversity and to provide more appropriate taxonomic arrangements, numerous valid descriptions of new genera and new species have been realized as well as many reclassifications that became necessary. Today, the group of aerobic endospore-forming bacteria embraces more than 25 genera and over 200 species.