Figure 2.

The number of B. subtilis essential gene homologues depends on genome size. (Top) All genes. Bacilli and close relatives denote Bacillus species and other low-G+C Gram-positive bacteria, but not clostridia, mycoplasma, and ureaplasma. (Middle and Bottom) Different bacterial gene categories. Empty red circles in Bottom refer to Bacilli and close relatives, whereas filled red circles refer to other bacteria. Interpolated lines throughout the figure correspond to the best fitting polynomial of the second or the fourth order. The number of genes is: information processing, 136; envelope, respiration, cell shape, and division, 76; cofactors, other, and unknown, 41; and nucleotides and glycolysis, 18.