Two years ago, whenever members of Jon Lundberg's team at Karolinska University wanted to get near their lab mice, they donned sterile gloves and reached into a steel isolator box. Not typical research rodents, these creatures had been bred to be completely germ-free. The technicians in the animal lab delivered the baby mice by cesarean section and kept them in complete isolation to eliminate the chance that bacteria would enter the rodents' bodies.
By comparing the germ-free mice's nitrate metabolism with that of regular bacteria-ridden mice, the researchers were hoping to get a better glimpse of how strongly the mammals depended on the bacteria to get their systemic supply of nitric oxide (NO) - an essential molecule for mammals, which can function as a neurotransmitter, vasodilator, and cytotoxin. But mammals, unable to produce NO's precursor nitrite themselves, depend on two well-established pathways for generating NO. In the first pathway, bacteria ...
