Candidatus Carsonella ruddii
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.
At the time of its sequencing, C. ruddii was thought to have the smallest genome of any characterized bacterial species. Nasuia deltocephalinicola is now considered to have the known smallest bacterial genome (112kb).
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- 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.
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- Scientific American – Tiny Genome May Reflect Organelle in the Making