ATP production in "Rickettsia" is the same as that in mitochondria. In fact, of all the microbes known, the "Rickettsia" is probably the closest relative (in a phylogenetic sense) to the mitochondria. Unlike the latter, the genome of "R. prowazekii", however, contains a complete set of genes encoding for the tricarboxylic acid cycle and the respiratory chain complex. Still, the genomes of the "Rickettsia", as well as the mitochondria, are frequently said to be "small, highly derived products of several types of reductive evolution".