A new target for nitric oxide has been revealed in studies of how it inhibits the growth of Salmonella.
This bacterium is a common cause of food-poisoning.
“Nitric oxide is naturally produced in the nose and the gut and other tissues in the body to ward off infection,” explained the senior author of the paper, Dr. Ferric Fang. He is a University of Washington (UW) professor of laboratory medicine, microbiology and medicine.
Nitric oxide — not to be confused with nitrous oxide, the laughing gas in dentists’ offices — is similar to the preservatives in hotdogs, Fang said. Reactive nitrogen species, like nitric oxide, make brown meat an appetizing pink. They also weed out microorganisms that spoil food or cause food poisoning.
Fang’s lab has made several important discoveries on ways mammals exploit the biochemical properties of nitric oxide to defend themselves from germs. Nitric oxide, a key actor in the body’s innate immune defenses, apprehends a rogue’s gallery of disease-causing organisms.
The newest results underscore that nitric oxide’s antimicrobial actions are due to its interference with the metabolism, or energy production, of pathogens.
“Nitric oxide imposes substantial metabolic restrictions on bacteria,” the researchers noted. Fang explained that its reactions with numerous metabolic targets accounts for the broad-spectrum nature of its success. It keeps many types of disease-causing bacteria at bay. It also prevents an overgrowth of the body’s many helpful bacteria.
The latest report on the versatility of nitric oxide in arming hosts against pathogens is published in the July 21 issue of Cell Host & Microbe. Dr. Anthony R. Richardson, who is now at the University of North Carolina at Chapel Hill, led the research while he was a postdoctoral fellow in the Fang lab.
Fang’s team looked at the multi-pronged action of nitric oxide on Salmonella enterica serovar Typhimurium. This type of Salmonella can contaminate food and is similar to the bacteria that cause typhoid fever.
Nitric oxide and related chemicals put Salmonella into a difficult situation called nitrosative stress. When exposed to nitric oxide, Salmonella is unable to make two essential amino acids, methionine and lysine.
Without these, Salmonella cannot grow.
“This is bad news for the bacteria, but not for the host,” Fang said. “Nitric oxide doesn’t damage the host that produces it.”