Selective Media for Isolation of Agrobacterium, Corynebacterium, Erwinia, Pseudomonas, and Xanthomonas

Abstract

Five selective plating media (designated as D-series media) were developed for plant-pathogenic bacteria in the genera Agrobacterium, Corynebacterium (including species pathogenic for animals and man), Erwinia, Pseudomonas, and Xanthomonas. The active constituents of these media were lithium chloride, sodium dodecyl sulfate, polymyxin, and glycine, all of which are known to affect the permeability of bacterial membranes. These selective media were designed using one or a combination of these compounds to permit the growth of bacteria of one genus and restrict the growth of all others. Using inoculum containing a mixture of different bacteria, the efficiencies of these media are as follows: Plating efficiencies ([colony numbers on selective medium : colony numbers on nonselective medium] × 10 2) were 90.3% for A. tumefaciens on medium D1; 27.1% for C. michiganense on medium D2; 77.7% for E. amylovora on medium D3; 6.5% for P. syringae on medium D4; and 78.4% for X. campestris on medium D5. Recovery efficiencies ([colony numbers from soil on selective medium: colony numbers without soil on the same selective medium] × 10 2) of the respective bacteria from soil artificially inoculated with a mixture of bacteria were 48.1% on D1, 79.8% on D2, 57.0% on D3, 26.9% on D4, and 79.9% on D5. Recovery of the pathogenic bacteria from diseased tissues was facilitated by these media.