Current Knowledge on Phylogeny and Taxonomy of Rickettsia spp.

Abstract

Due to improved diagnostic methods and increased interest, the number of representatives of the genus Rickettsia has increased dramatically over the past 20 years, with 25 currently validated species. These arthropod-associated intracellular bacteria are now recognized in all parts of the world. The comparison of the phylogenic organizations obtained from the study of several genes with different functions, and more recently from genomic sequences, provided basis to establish a reliable taxonomy of the bacteria induded in the genus Rickettsia. These data were incorporated into polyphasic consensus guidelines that provide clear recommendations for the taxonomic classification and nomenclature of rickettsiae and rickettsial diseases.

Spotted fever group Rickettsia infecting ticks (Acari: Ixodidae) in the state of Santa Catarina, Brazil

“…However, we are aware that the species definition for Rickettsia remains a controversial issue, without a major consensus among rickettsiologists (Walker & Ismail 2008, Fournier & Raoult 2009, Goddard 2009). …”

Serologic evidence of the exposure of small mammals to spotted-fever Rickettsia and Rickettsia bellii in Minas Gerais, Brazil

“…Spotted-fever Rickettsia is a group strongly associated with ticks as vectors and includes both pathogenic species such as Rickettsia rickettsii, R. conorii, R. parkeri, R. africae, as well as Rickettsia with undetermined pathogenicity. The world has witnessed the discovery of several Rickettsia species in the last two decades and description of new species can be expected [1]. At the same time, the knowledge about the relationship between human disease and specific Rickettsia has also increased with the use of molecular diagnosis.…”

The Rebirth of Culture in Microbiology through the Example of Culturomics To Study Human Gut Microbiota

“…A DNA-DNA hybridization value of Յ70% is considered the cutoff, permitting the definition of new species (256,257). However, various limitations have been reported, including its elevated cost; the lack of interlaboratory and interassay reproducibility, preventing the creation of a reference database (254); and the cutoff value not being applicable to all prokaryotic genera, as is the case for members of the genus Rickettsia (48). Similarly, the16S rRNA sequence identity discriminatory power varies greatly from one genus to another (252,258).…”