The research, which is featured on the cover of the July 17, 2005 issue of The Journal of Experimental Medicine, focused on the major human pathogen Staphylococcus aureus and the characteristic yellow-orange color for which it is named ("aureus" is Latin for "golden").
Among the deadliest of all disease-causing organisms, "Staph" is the leading cause of human infections in the skin and soft tissues, bones and joints, abscesses and normal heart valves. Staph especially flourishes in the hospital setting, producing bloodstream and surgical wound infections. The spread of antibiotic resistant strains of Staph, referred to as methicillin-resistant Staphylococcus aureus or MRSA, has reached epidemic proportions and poses a major threat to the public health.
The UCSD team proved for the first time that the golden pigment that coats the surface of Staph is not just for decoration; rather, the molecules that give the bacteria its golden hue also help it resist killing by neutrophils, white blood cells with a front line role in immune defense against invading microbes.
Staph's coloration reflects the production of molecules called carotenoids, similar to those present in carrots and other colorful vegetables and fruits. Dietary carotenoids have long been touted for their antioxidant properties with hope that they could slow aging or fight off cancer. The scientists found that pathogenic Staph took advantage of the antioxidant effects of its carotenoid pigment to extend its own life, by inactivating chemicals deployed by neutrophils that are lethal to most bacteria.
The UCSD team u
Contact: Leslie Franz
University of California - San Diego