SELECTIVE INHIBITION OF PROLINE-INDUCED PIGMENTATION IN WASHED CELLS OF SERRATIA MARCESCENS

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Abstract
Streptomycin, chloramphenicol and tetracyclines inhibited the synthesis of prodigiosin by Serratia marcescens strain Dl. This occurred at concentrations of the antibiotic too low to inhibit the growth of the organism in either agar or broth cultures. Nonpigmented cells were produced in broth by either adding streptomycin or incubating at 37 C. After being washed and resuspended in aqueous saline containing either casein hydrolysate, L-poline or a glycine-succinate mixture and incubated at 27 C for 24 hr, these cells formed pigment. The appearance of pigment was preceded by a lag period of 10 hr. Prodigiosin production by these washed suspensions of cells was completely inhibited by either streptomycin or glucose, or by incubation at 37 C instead of 27 C. Even though pigmentation by washed-cell suspensions was induced by proline, the utilization of proline was not affected by streptomycin or glucose or by incubation at 37 C. To block pigmentation completely, streptomycin had to be added to proline-supplemented cells before they were 10 hr. old. Addition of the antibiotic after the end of the induction period caused either partial or no inhibition of pigment production. Streptomycin caused an increase in the endogenous respiration of S. marcescens but failed to affect the constitutive enzymes that oxidize glucose. The possible relationships of these phenomena are discussed.