''Coxiella'' refers to a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

Gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wa ...

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...

in the family Coxiellaceae. It is named after Herald Rea Cox (1907–1986), an American bacteriologist. It is one of the Gammaproteobacteria. ''

Coxiella burnetii ''Coxiella burnetii'' is an obligate intracellular bacterial pathogen, and is the causative agent of Q fever. The genus ''Coxiella'' is morphologically similar to ''Rickettsia'', but with a variety of genetic and physiological differences. ''C. ...

'' is the best known member of this genus. It is an intracellular parasite and it survives within the

phagolysosome In biology, a phagolysosome, or endolysosome, is a cytoplasmic body formed by the fusion of a phagosome with a lysosome in a process that occurs during phagocytosis. Formation of phagolysosomes is essential for the intracellular destruction of mic ...

s of its host. It causes

Q fever Q fever or query fever is a disease caused by infection with ''Coxiella burnetii'', a bacterium that affects humans and other animals. This organism is uncommon, but may be found in cattle, sheep, goats, and other domestic mammals, including ...

. The majority of ''Coxiella''’s described members are non pathogenic forms which are often found in ticks. Approximately two-thirds of tick species harbour ''Coxiella''-like endosymbionts required for tick survival and reproduction. Genomes of ''Coxiella''-like endosymbionts encode pathways for the biosynthesis of major B vitamins and co-factors that fit closely with the expected nutritional complements required for strict haematophagy. The experimental elimination of ''Coxiella''-like endosymbionts typically results in decreased tick survival, molting, fecundity and egg viability, as well as in physical abnormalities. ''Coxiella''-like endosymbionts are often misidentified as ''Coxiella burnetii''; however, ''Coxiella''-like endosymbionts lack virulence genes and cannot infect humans.

Molecular Signatures

Seven

conserved signature indels Conserved signature inserts and deletions (CSIs) in protein sequences provide an important category of molecular markers for understanding phylogenetic relationships. CSIs, brought about by rare genetic changes, provide useful phylogenetic markers ...

(CSIs) were identified through genomic analyses as exclusively shared by ''C. burnetii'' and other unnamed ''Coxiella''-related species in the

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

s glutamine-hydrolyzing

GMP synthase Guanosine monophosphate synthetase, () also known as GMPS is an enzyme that converts xanthosine monophosphate to guanosine monophosphate. In the de novo synthesis of purine nucleotides, IMP is the branch point metabolite at which point the path ...

, type I methionyl aminopeptidase, ribonucleoside-diphosphate reductase subunit alpha, translation initiation factor IF-3, phosphomannomutase-phosphoglucomutase, LPS export

ABC transporter The ATP-binding cassette transporters (ABC transporters) are a transport system superfamily that is one of the largest and possibly one of the oldest gene families. It is represented in all extant phyla, from prokaryotes to humans. ABC transpo ...

ATP-binding protein, and

NADH-quinone oxidoreductase NADH:ubiquinone reductase (non-electrogenic) (, '' NDH-2'', ''ubiquinone reductase'', ''coenzyme Q reductase'', ''dihydronicotinamide adenine dinucleotide-coenzyme Q reductase'', ''DPNH-coenzyme Q reductase'', ''DPNH-ubiquinone reductase'', ''NADH ...

subunit G. These CSIs serves to reliably demarcate the genus from other ''Legionellales'' species in molecular terms. Additionally, three CSIs were identified as uniquely shared between the genus ''Coxiella,'' and two other genera belonging to the family '' Coxiellaceae, Diplorickettsia'' and '' Rickettsiella.'' The absence of '' Aquicella'' species (the remaining genus within the family '' Coxiellaceae)'' from the shared CSIs suggests that the genera ''Coxiella, Diplorickettsia and Rickettsiella'' share a common ancestor exclusive of '' Aquicella.''

References

External links

Coxiella
genomes and related information a
PATRIC
a Bioinformatics Resource Center funded b
NIAID
Legionellales Monotypic bacteria genera Bacteria genera {{Legionellales-stub