Nitric Oxide Has The Ability To Inhibit The Growth Of Salmonella

Nitric Oxide-Rich Foods

Nitric Oxide's Attack On Salmonella Bacteria...

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 researchers from the University of Washington (UW) specializing in laboratory medicine, microbiology and medicine.

Nitric oxide is not to be confused with nitrous oxide, the "laughing gas" in dentists' offices, is actually similar to the preservatives in hotdogs and luncheon deli meats,

Reactive nitrogen species, like nitric oxide, make brown meat a more appetizing pink. Most importantly, they also weed out microorganisms that spoil food or cause food poisoning.

New research 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 and 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 inhibited. It also prevents an overgrowth of the body's many helpful bacteria.

The research 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 specific amino acids, Salmonella cannot grow.

The ability to withstand nitrosative stress makes some forms of bacteria more virulent than milder types that can't handle it.

They found that nitric oxide and its cousins disrupt several points in the Krebs cycle, also known as the tricarboxylic acid cycle. This cycle is the second stage in cellular respiration, when fuel is broken down to release energy for cell growth
and division.

The researchers outlined how multiple interruptions in this cycle create a series of biochemical consequences that starve Salmonella of methionine and lysine. Nitric oxide also blocks certain regulatory genes that otherwise would give Salmonella an alternate chemical route out of its distress.

"Collectively, this work demonstrates that nitric oxide imposes substantial metabolic restrictions on bacteria," the authors concluded.

"More generally," they noted, "this study provides an excellent illustration that a proper understanding of host-pathogen interactions and the development of therapeutic interventions require a detailed knowledge of pathogen metabolism."

Nitric oxide's targeting of the Krebs cycle is not unique to Salmonella. In learning how the body naturally controls the energy supplies and growth of varied disease-causing organisms, scientists may be able to develop new broad-spectrum anti-microbials that mimic these effects, drugs that promote the body's own natural defenses against infection, or agents that overcome the ways virulent bacteria compensate when being starved of certain nutrients.

The research was supported by grants from the National Institutes of Health.

 Story Source: University of Washington.

Journal Reference: Multiple Targets of Nitric Oxide in the Tricarboxylic Acid Cycle of Salmonella enterica Serovar Typhimurium. Cell Host & Microbe, 21 July 2011;

This article is for informational and educational purposes only, and is not intended to provide medical advice,diagnosis or treatment. Contact your doctor or healthcare professional for medical and nutritional consultation.