The endosymbiotic bacteria have a very small genome Examine

Solution

One very good example for bacterial endosymbiont is the Carsonella ruddii, endosymbiont of the psyllium, Pachypsylla Venusta. It is considered to be the most smallest bacterial endosymbiont consisting of a small genome size and was sequenced successfully. It\'s genome contains only 182 ORFs ( Open Reading Frame), less than 3% intergenic DNA and has a GC content of 16.5%.

Another example for obligately intracellular bacteria is Blochmannia Pennsylvanicus, an obligate endosymbiont of Camponotus pennsylvanicus, helps to trace evolutionary changes through bacterial - ant interaction. B.pennsylvanicus genome consists of 792 kb, 654 bp circular chromosome was sequenced. This is AT rich genome has a relatively low percentage of coding DNA of 76.7 %, Ribosomal binding sites ( RBS) for 479 of 610 ORFs, but only 42 has canonical AGGAG motif. It largely reflects differential gene loss. Gene loss in the B. pennsylvanicus lineage is approximately ~6.5 times slower with loss or inactivation of one ORF per 4.0-5.0 Myr.

Endosymbionts have revealed convergent patterns of genome evolution, including genome reduction and a trend toward AT richness, also covers challenge assumptions about evolution within host cells.