The golden colour help it resist killing by neutrophils, white blood cells with a front line role in immune defense against invading microbes.

This is the proof: “The UCSD team used a molecular genetic approach for their studies, knocking out the genes for carotenoid synthesis to generate a mutant strain of Staph that appeared white in color instead of the normal gold.

“We found that the nonpigmented Staph mutant became much more susceptible to oxidants such as hydrogen peroxide and singlet oxygen produced by neutrophils,” said George Liu, M.D., Ph.D., a research fellow in the UCSD department of pediatrics who spearheaded the studies. “Without its golden pigment, the Staph lost its ability to survive in human neutrophils or blood, and could no longer form an abscess when injected into the skin of experimental mice.”

refrence: http://www.innovations-report.com/html/reports/life_sciences/report-46413.html

http://www.jem.org/cgi/content/full/202/2/209

btw: I always thought of microbiology as boring (sorry) but now i totally changed my opinion!!
Thank you Dr.Ramy

i read that scientists suggest that anti biotic which can impair the golden pigment can be effective against S.aureus,
could this (theoritically) be done by modifing the oxidation potential of the carotenoid pigment and (thus decreasing its affinity towards electons to be lower than the bacterial structure it protects) ??
this a suggestion i thought about in the biochemistery lecture about redox potential!