Candidatus Carsonella ruddii
| Candidatus Carsonella ruddii | |
|---|---|
| Scientific classification | |
| Kingdom: | Bacteria |
| Phylum: | Proteobacteria |
| Class: | Gamma Proteobacteria |
| Order: | unclassified |
| Genus: | Candidatus Carsonella |
| Species: | Ca. C. ruddii |
| Binomial name | |
| Candidatus Carsonella ruddii Thao et al. 2000 | |
Candidatus Carsonella ruddii is an obligate endosymbiotic Gamma Proteobacterium[1] with one of the smallest genomes of any characterised bacteria.[2]
Endosymbiosis
The species is an endosymbiont that is present in all species of phloem sap-feeding insects known as psyllids.[3][4] The endosymbionts occurs in a specialised structure known as the bacteriome.
C. ruddii is not completely parasitic in its relationship with its host insect, but it supplies the host with some essential amino acids. It is therefore probably in the evolutionary process of becoming an organelle, like the mitochondria of mammalian cells.[5]
Genome
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 pairs and that it has a high coding density (97%) with many overlapping genes and reduced gene length. The number of predicted genes 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.[2]
At the time of its sequencing, C. ruddii was thought to have the smallest genome of any characterized bacterial species.[6] Nasuia deltocephalinicola is now considered to have the known smallest bacterial genome (112kb).[7]
C. ruddii and related species appear to be actively undergoing gene loss.[8]
References
- ↑ Spaulding, A. W.; von Dohlen, C. D. (1998). "Phylogenetic Characterization and Molecular Evolution of Bacterial Endosymbionts in Psyllids (Hemiptera: Sternorrhyncha)". Molecular Biology and Evolution. 15 (11): 1506–1513. doi:10.1093/oxfordjournals.molbev.a025878.
- 1 2 Nakabachi A, Yamashita A, Toh H, Ishikawa H, Dunbar H, Moran N, Hattori M (2006). "The 160-kilobase genome of the bacterial endosymbiont Carsonella.". Science. 314 (5797): 267. doi:10.1126/science.1134196. PMID 17038615.
- ↑ Thao, M.L. (2000). "Cospeciation of Psyllids and Their Primary Prokaryotic Endosymbionts". Applied and Environmental Microbiology. 66: 2898–2905. doi:10.1128/aem.66.7.2898-2905.2000.
- ↑ Thao, M.L. (2001). "Phylogenetic analysis of vertically transmitted psyllid endosymbionts (Candidatus Carsonella ruddii) based on atpAGD and rpoC: comparisons with 16S-23S rDNA-derived phylogeny". Current Microbiology. 42: 419–21. doi:10.1007/s002840010240. PMID 11381334.
- ↑ Tortora(1), Funke(2), Case(3), Gerard J(1), Berdell R(2), Christine L(3) (2016). Microbiology: An Introduction (12th Edition). USA: Pearson. p. 315. ISBN 978-0321929150.
- ↑ Moran, Nancy A.; Bennett, Gordon M. (8 September 2014). "The Tiniest Tiny Genomes". Annual Review of Microbiology. 68 (1): 195–215. doi:10.1146/annurev-micro-091213-112901.
- ↑ Bennett, G. M.; Moran, N. A. (5 August 2013). "Small, Smaller, Smallest: The Origins and Evolution of Ancient Dual Symbioses in a Phloem-Feeding Insect". Genome Biology and Evolution. 5 (9): 1675–1688. doi:10.1093/gbe/evt118. PMID 23918810.
- ↑ Sloan, D. B.; Moran, N. A. (19 July 2012). "Genome Reduction and Co-evolution between the Primary and Secondary Bacterial Symbionts of Psyllids". Molecular Biology and Evolution. 29 (12): 3781–3792. doi:10.1093/molbev/mss180.
External links
- Scientific American – Tiny Genome May Reflect Organelle in the Making