The Pseudomonas aeruginosa ferripyoverdine receptors are iron regulated outer membrane proteins, a part of this book explains how experimental Polymerase Chain Reaction (PCR) procedures was used to determine the complete (about 2.5 kb) gene sequences of these receptors,however, it has been previously shown that the extracellular and outer membrane protein encoding genes in Pseudomonas aeruginosa evolve faster than cytoplasmic protein encoding genes, from the Phd work done , comparison of the ferripyoverdine receptors (fpvA) genes of Pseudomonas aeruginosa suggest a more rapid evolution of the type II pyoverdine receptor genes.