Effect of iron and salt on prodigiosin synthesis in Serratia marcescens

Abstract

S. marcescens wild types ATCC 264 and Nima grew but did not synthesize prodigiosin in a glycerol alanine medium containing 10 ng of Fe per ml. Wild type 264 required the addition of 0.2 μg of Fe per ml for maximal growth and prodigiosin synthesis; Nima required 0.5 μg of Fe per ml. Three percent, but not 0.1%, sea salts inhibited prodigiosin synthesis in a complex medium containing up to 10 μg of Fe per ml. NaCl was the inhibitory sea salt component. The inhibition was not specific for NaCl; equimolar concentrations of Na2SO4, KCl, and K2SO4 also inhibited prodigiosin synthesis. Experiments with strains 264 and Nima and with mutant WF which cannot synthesize 4 methoxy 2-2' bipyrrole 5 carboxaldehyde (MBC), the bipyrrole moiety of prodigiosin, and with mutant 9-3-3 which cannot synthesize the monopyrrole moiety 2 methyl 3 amylpyrrole (MAP) showed that both MBC synthesis and the reaction condensing MAP and MBC to form prodigiosin were relatively more sensitive to NaCl inhibition than the MAP synthesizing step. The capacity of whole cells to condense MAP and MBC was present, but inactive, in cells grown in NaCl; removal of the NaCl from non proliferating salt grown cells restored the activity. Other evidence suggests the existence of a common precursor to the MAP and MBC synthesizing pathways.