Syringomicin production is stimulated by cysteine in Pseudomonas syringae pv. syringae

Abstract The influence of cysteine and serine in the production of syringomycin by Pseudomonas syringae pv. syringae has been studied. Both amino acids increased toxin synthesis in wild-type strains, although cysteine has a higher stimulatory effect than serine. To corroborate the role of cysteine in the production of syringomycin, a Cys^? mutant of P. syringae pv. syringae was isolated by transpositional mutagenesis with Tn5; this Cys^? mutant did not produce syringomycin. Nevertheless, and after the addition of high concentrations of cysteine, the cys ∷Tn5 mutant recovered its ability to produce syringomycin. On the other hand, the addition of serine did not return the production of syringomycin to the sys ∷ Tn5 strain: all these data indicated that cysteine modulates the synthesis of syringomycin in P. syringae pv. syringae positively.