||Caption: Serratia marcescens - Gram-negative, facultative anaerobic prokaryote (bacterium). Serratia species occur as commensal fauna in the intestinal mucosal lining of man and mammals. It also occurs in soil, water, on plants and has a characteristic red pigment. S. marcescens is occasionally pathogenic in humans, as a nocosomial infection and septicemia. It can be associated with urinary and respiratory tract infections, endocarditis, osteomyelitis, septicemia, wound infections, eye infections, conjunctivitis, keratitis, endophthalmitis, and tear duct infections, and meningitis. In the 1950s S. marcescens was erroneously believed to be non-pathogenic and its reddish coloration was used in school experiments to track infections for demonstrating the importance of hand washing. It has also been used in biological warfare tests by the United States Military. In corals, it is the cause of the disease known as White pox. Serratia species appear to thrive in saline breast implants, living on the glucose that diffuses across the implant's outer shell.