FNTA and infection: Since the host lung microbiome is able to guard against colonization and infection of pathogens by competing for the nutrient metal iron (40), the P. aeruginosa is warranted to increase its metal iron acquisition function to overcome the iron limitation which could be a selective pressure facilitating the microevolution of fptA gene, thus in favor of the fitness and adaptation of P. aeruginosa isolates in relapse and prolonged infections.