The Killer Bacteria Hall of Fame no doubt houses the usual suspects: Yersinia pestis, perpetrator of the Plague; Treponema pallidum, the spiral-shaped culprit in syphilis; and Vibrio cholerae, the swimmer that causes cholera. But you have probably never heard of one of the inductees.
Serratia marcescens is a forgotten but ubiquitous bacterium that can produce a red pigment called prodigiosin and likes to hang out as a pink film in the shower grout and toilet bowls of less-than-scrupulously clean homes. The pigment is so persistent that giant amoebas called slime molds that dine on S. marcescens turn red just as flamingoes that eat shrimp turn pink. Yet the picture emerging of this unsung organism is increasingly sinister.
These bacterium first attracted scientific attention in early modern times when it was found oozing out of damp Italian statues, communion wafers and, of all things, polenta doing its best impersonation of "blood." And blood it was taken to be—usually miraculously—until a pharmacist named Bartolomeo Bizio started trying to get to the bottom of what peasants declared to be an outbreak of diabolically cursed polenta in 1819.
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