Prodigiosin

Prodigiosin is the red pigment produced by many strains of the bacterium Serratia marcescens, other Gram-negative, gamma proteobacteria such as Vibrio psychroerythrus and Hahella chejuensis It is in a family of compounds termed "prodiginines", which are produced in some Gram-negative gamma proteobacteria, as well as select Gram-positive Actinobacteria (e.g. Streptomyces coelicolor). The name "prodigiosin" is derived from "prodigious" (i.e. something marvelous).

Secondary metabolite

Prodigiosin is a secondary metabolite of Serratia marcescens. Because it is easy to detect, it has been used as a model system to study secondary metabolism. Prodigiosin production has long been known to be enhanced by phosphate limitation. In low phosphate conditions, pigmented strains have been shown to grow to a higher density than unpigmented strains.

Religious function

The ability of pigmented strains of Serratia marcescens to grow on bread has led to a possible explanation of Medieval transubstantiation miracles, in which Eucharistic bread is converted into the Body of Christ. Such miracles led to Pope Urban IV instituting the Feast of Corpus Christi in 1264. This followed celebration of a Mass at Bolsena in 1263, led by a Bohemian priest who had doubts concerning transubstantiation. During the Mass, the eucharist appeared to bleed and each time the priest wiped away the blood, more would appear. This event is celebrated in a fresco in the Pontifical Palace in the Vatican City, painted by Raphael.