Effect of peptones on the ability of plant pathogenic bacteria to grow on media supplemented with copper sulphate
The extensive use of copper compounds for control of bacterial plant pathogens could lead to selecting strains of the pathogens that are copper-resistant. The ability to grow on a medium supplemented with copper, and therefore the concentration of copper to which bacterial strains are resistant, depends on the composition of the medium used for the test. The effects of different peptones (casitone and proteose peptone No. 3) and different media on the ability of strains of Pseudomonas syringae to grow in presence of copper were determined. Similar results were obtained when casitone was substituted with proteose peptone No. 3 in casitone yeast extract medium, but not when those two peptones were interchanged in King’s B medium. In water, casitone allowed strains of P. syringae pv. actinidiae (Psa) to grow in the presence of higher amounts of copper than proteose peptone No. 3 did. In all cases, resistance to copper was increased with increased peptone concentration.