This is further evidenced by a publication which demonstrated the ability of purH mutant Salmonella (an auxotroph for purine) to survive and cause lethal infection in mice (McFarland & Stocker, 1987) since it was estimated that around 1800 molecules of purine could be transported into Salmonella cell per second from the host environment (Bumann, 2009). This evidence concerns the gene ATIC and infection.