Serratia marcescens is found everywhere, according to Scientific American. It is found in the grout between tiles in shower stalls, in toilet bowls, and in catheters, feeding tubes and respirators. It is notorious for causing infection in neonates, and it is found in contact lenses that are not washed as often or thoroughly as they should be.
It is also found in soaps and cleansers, says Scientific American. Benign versions of the bacteria are found in the soil, water and in the guts of mammals. It is found at seasides and in canals and animals that live by the shore, and to the surprise of scientists, it has been found in the ocean. As of 2002, it has been causing a die-off of elkhorn coral. This strain of Serratia marcescens is the same as that found in human feces, and scientists believe that it escaped from septic tanks. The bacteria also has a gruesome symbiotic relationship with a type of nematode, or roundworm.
Serratia marcescens is a Gram-negative bacteria that is notable for prodigiosin, a pigment that turns it red, claims Scientific American. The bacteria form in great pink sheets and are eaten by slime molds, which turn pink because of this pigment. If the bacteria infect a holy statue, they have been known to make it "bleed." The pigment might be used to protect the bacteria from free radical damage.