Assays on experimental methods for the obtention of auxotrophic mutants from xanthomonas campestris

Abstract

Different methods were tried with the aim of obtaining auxotrophic mutants from the phytopathogenic bacteria Xanthomonas campestris, isolated from Brassica oleraeea. The most effective method was by combining the method of Gorini and Kaufman, (using 0,54 M sucrose to avoid the lysis of prototrophic bacteria) and the method of Lubin (by recycling the growing of the bacterial cells with penicillin. Three types of mutants were produced: a) a group of unstable mutants; b) a group of mutants with residual growth; c) a group of auxotrophic mutants requiring one of the following aminoacids: proline, tryptophane, and phenylalanine; one mutant requiring isoleucine plus valine; one mutant requiring histidine and leucine; and one mutant requiring glycine and lysine. The mutant deficient for the synthesis of glycine and lysine showed a relationship toward ornithine and citrulline, since lysine could be substituted by either one of the latter aminoacids.