Pathogenicity and Its Implications in Taxonomy: The and Case.

The intracellular pathogens of the genus are phylogenetically close to , a diverse group of free-living bacteria with a few species occasionally infecting medically compromised patients. A group of taxonomists recently included all organisms in the genus based on global genome analyses and alleged equivalences with genera such as . Here, we demonstrate that such equivalencies are incorrect because they overlook the complexities of pathogenicity. By summarizing and divergences in lifestyle, structure, physiology, population, closed versus open pangenomes, genomic traits, and pathogenicity, we show that when they are adequately understood, they are highly relevant in taxonomy and not unidimensional quantitative characters. Thus, the and differences are not limited to their assignments to different "risk-groups", a biologically (and hence, taxonomically) oversimplified description that, moreover, does not support ignoring the rule, as proposed. Since the epidemiology, prophylaxis, diagnosis, and treatment are thoroughly unrelated, merging free-living organisms with highly pathogenic organisms brings evident risks for veterinarians, medical doctors, and public health authorities who confront brucellosis, a significant zoonosis worldwide. Therefore, from taxonomical and practical standpoints, the and genera must be maintained apart. Consequently, we urge researchers, culture collections, and databases to keep their canonical nomenclature.