Serratia marcescens

Bacteria, Gram-Negative

Structure and Physiology

This bacteria is a Gram-negative, rod-shaped, facultative anaerobe that has been classified as an opportunistic pathogen for immunocompromised individuals. This bacteria can be commonly found in damp environments like bathrooms, where it manifests as a pink-orange film due to a reddish-orange pigment called prodigiosin.

Transmission and Disease

S. marcescens can be responsible for infections at several sites on the human body including the eyes, urinary tract, and respiratory system.


This is a clinically relevant organism and is used as a standard organism in Hand Sanitizer testing.


Due to the red pigmentation and the relative ease of picking this organism out in a lawn of other microorganisms because of this trait, S. marcescens has been utilized as an enviromental indicator to trace such things as bacterial activity and, most notably, the possibility of tranmission of biological weapons by air currents. "Operation Sea-Spray"  was carried out by the U.S. Navy in the summer of 1950, and included releasing S. marcescens off of the shore of San Francisco. This secret experiment was performed before it was known that this organism is an oppotunistic pathogen.

  • Williams, Robert P. "Biosynthesis of prodigiosin, a secondary metabolite of Serratia marcescens." Applied microbiology 25.3 (1973): 396-402.