In 2006, scientists found the smallest collection of genes known (to date): tiny, endosymbiotic bacteria that live inside special cells of a small insect—a sap-feeder, psyllid insect called Pachypsylla venusta. Although it is not uncommon to find bacteria helping out an insect in such a symbiotic relationship, this insect was examined because it had only one species of endosymbiotic bacteria. The researchers sequenced the genome (the complete complement of DNA) for the bacteria Carsonella ruddii, and discovered it was one-third the size of the previously reported “smallest” cellular genome.

Bacteria reproduce by binary fission. It has nothing to do with computers, but is the way certain organisms reproduce asexually. In this case, a cell divides into two similar cells. First the circular, bacterial DNA replicates, then a transverse wall is formed by an ingrowth of both the plasma membrane and the cell wall. In a favorable environment, bacteria can reproduce very rapidly. Favorable circumstances include laboratory cultures or its natural habitat. For example, under good conditions, E. coli can divide every twenty minutes—and a laboratory culture started with a single cell can produce a colony of 10,000,000 to 100,000,000 (or 107 to 108) bacteria in about twelve hours.