Candidatus Carsonella ruddii
Encyclopedia
Candidatus
Carsonella ruddii is an obligate
endosymbiotic Gamma Proteobacterium; it has the smallest genome
of any characterised bacteria.
The species is an endosymbiont
that is present in all species of phloem
sap-feeding insects known as psyllids. The endosymbionts occurs in a specialised structure known as the bacteriome
.
In 2006 the genome of Ca. C. ruddii strain Pv
(Carsonella-Pv) of the hackberry petiole gall psyllid, Pachypsylla venusta, was sequenced at RIKEN
in Japan and the University of Arizona
. It was shown that the genome consists of a circular chromosome of 159,662 base pair
s and that it has a high coding density (97%) with many overlapping genes and reduced gene length. The number of predicted gene
s was 182, also the lowest on record (NCBI-Genome). In comparison, Mycoplasma genitalium
, which has the smallest genome of any free-living organism, has a genome of 521 genes. Numerous genes considered essential for life seem to be missing, suggesting that the species may have achieved organelle
-like status.
Candidatus
Candidatus is in scientific classification a component of the taxonomic name for a bacterium that cannot be maintained in a Bacteriology Culture Collection. It is an interim taxonomic status for noncultivable organisms. An example would be "Candidatus Phytoplasma allocasuarinae"...
Carsonella ruddii is an obligate
Obligate
Obligate means "by necessity" and is used mainly in biology in phrases such as:* Obligate aerobe, an organism that cannot survive without oxygen* Obligate anaerobe, an organism that cannot survive in the presence of oxygen...
endosymbiotic Gamma Proteobacterium; it has the smallest genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
of any characterised bacteria.
The species is an endosymbiont
Endosymbiont
An endosymbiont is any organism that lives within the body or cells of another organism, i.e. forming an endosymbiosis...
that is present in all species of phloem
Phloem
In vascular plants, phloem is the living tissue that carries organic nutrients , in particular, glucose, a sugar, to all parts of the plant where needed. In trees, the phloem is the innermost layer of the bark, hence the name, derived from the Greek word "bark"...
sap-feeding insects known as psyllids. The endosymbionts occurs in a specialised structure known as the bacteriome
Bacteriome
A bacteriome is a specialized organ, found mainly in some insects, that hosts endosymbiotic bacteria.Bacteriomes contain specialized cells, called bacteriocytes, that provide nutrients and shelter to the bacteria while protecting the host animal....
.
In 2006 the genome of Ca. C. ruddii strain Pv
Pathovar
A pathovar is a bacterial strain or set of strains with the same or similar characteristics, that is differentiated at infrasubspecific level from other strains of the same species or subspecies on the basis of distinctive pathogenicity to one or more plant hosts.Pathovars are named as a ternary or...
(Carsonella-Pv) of the hackberry petiole gall psyllid, Pachypsylla venusta, was sequenced at RIKEN
RIKEN
is a large natural sciences research institute in Japan. Founded in 1917, it now has approximately 3000 scientists on seven campuses across Japan, the main one in Wako, just outside Tokyo...
in Japan and the University of Arizona
University of Arizona
The University of Arizona is a land-grant and space-grant public institution of higher education and research located in Tucson, Arizona, United States. The University of Arizona was the first university in the state of Arizona, founded in 1885...
. It was shown that the genome consists of a circular chromosome of 159,662 base pair
Base pair
In molecular biology and genetics, the linking between two nitrogenous bases on opposite complementary DNA or certain types of RNA strands that are connected via hydrogen bonds is called a base pair...
s and that it has a high coding density (97%) with many overlapping genes and reduced gene length. The number of predicted gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s was 182, also the lowest on record (NCBI-Genome). In comparison, Mycoplasma genitalium
Mycoplasma genitalium
Mycoplasma genitalium is a small parasitic bacterium that lives on the ciliated epithelial cells of the primate genital and respiratory tracts. M. genitalium is the smallest known genome that can constitute a cell, and the second-smallest bacterium after the recently-discovered endosymbiont...
, which has the smallest genome of any free-living organism, has a genome of 521 genes. Numerous genes considered essential for life seem to be missing, suggesting that the species may have achieved organelle
Organelle
In cell biology, an organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid bilayer....
-like status.
External links
- Scientific American – Tiny Genome May Reflect Organelle in the Making