The Littlest Genome—Organism Or Organelle?


Japanese and American scientists report that they have discovered the smallest genome so far in an organism. The organism is the bacterium Carsonella rudii, which lives as an endosymbiont inside a small insect. While humans take around 23,000 genes to make it through the world, the bacterium can keep body (cell) and soul together with only 182 genes. However, it cannot live outside the insect. Scientists speculate that Carsonella rudii may be on its way to becoming an organ rather than organism. Scientists think that this happened to the organism that evolved hundreds of millions years ago into the mitochondria that now serve as thousands of cellular powerplants in each animal cell including humans. Apparently most mitochondrial genes eventually migrated to the nuclei of cells leaving in human mitochondria a genome consisting of 37 genes in the mitochondria themselves.

Researchers like human genome sequencer Craig Venter are trying to figure out the minimum number of genes it takes for an organism to live in the outside world. Even then such a minimized bacterium would require a specialized and protected environment in which to live. Naturally, some bioethicists are concerned about the minimum genome project.