Effect of Iron and Salt on Prodigiosin Synthesis in Serratia marcescens
Serratia 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-carboxyaldehyde (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.
Prodigiosin Synthesis in Mutants of Serratia marcesens
Morrison, D. A. (Harvard College, Cambridge, Mass.). Prodigiosin synthesis in mutants of Serratia marcescens. J. Bacteriol. 91:1509–1604. 1966.—Exchange of biosynthetic intermediates through the culture medium was used to characterize several hundred new color mutants of Serratia marcescens. The general scheme of prodigiosin synthesis as a bifurcated pathway, in which monopyrrole and bipyrrole precursors are synthesized separately and then coupled to form pigment, was confirmed and extended. Mutants of one new class excreted a product likely to be a new intermediate in monopyrrole synthesis, those of a second excreted a new product in the bipyrrole pathway, and those of a third were blocked at early steps in both pathways. Two novel classes of mutants were isolated, in each of which a lack of some product present in Serratia and Escherichia cultures resulted in loss of all steps in prodigiosin biosynthesis.
Highly enantio- and diastereoselective synthesis of β-methyl-γ-monofluoromethyl-substituted alcohols.
Enanatiopure β-methyl-γ-monofluoromethyl alcohols were prepared from the allylic alkylation between fluorobis(phenylsulfonyl)methane with Morita-Baylis-Hillman carbonates. The reaction was catalyzed by using the Cinchona alkaloid derivative, (DHQD)(2)AQN. The origin of the stereoselectivity was verified by DFT methods. Calculated geometries and relative energies of various transition states strongly support the observed stereoselectivity.