USEFULNESS OF NUTRITIONAL SCREENING FOR THE IDENTIFICATION OF XANTHOMONAS-CAMPESTRIS DNA HOMOLOGY GROUPS AND PATHOVARS

A nutritional screen of 143 carbon sources was done on 88 strains of x anthomonads from 39 different Xanthomonas campestris pathovars, X. alb ilineans, X. fragariae, and 'X. gardneri'. Six compounds, cellobiose, fructose, fumarate, glucose, L-malate and succinate supported growth o f all strains except X. albilineans, whereas 92 substrates were not ut ilized by any strain. Substrate utilization patterns appeared sufficie ntly uniform among the various genomic groups within Xanthomonas to al low their differentiation. The most easily distinguished pathovars wer e X. cam. pv. oryzicola and X. cam. secalis of genomic groups 4 and 3, respectively, because they used few substrates. Genomic group 1 was t he most difficult to distinguish because utilization patterns differed substantially among the pathovars that comprise the group. Substrate utilization was useful for distinguishing pathovars within genomic gro ups. For example, X. campestris pv. pelargonii of genomic group 5 was differentiated from X. cam. carotae, X. cam. taraxaci, and 'X. gardner i' by growth on aconitate but not D-tartrate. Similarly, use of D-tart rate differentiated X. celebensis from X. cam. pv. juglandis within gr oup 6. Sorbitol was utilized only by X. cam. pv. plantaginis of group 2 and arabitol was a useful substrate for identifying X. cam. pv. pisi and pv. eucalypti. Most patterns of carbon utilization were confirmed with Biolog tests but there were exceptions as was found with utiliza tion of glycerol and D-arabitol. The Biolog test also revealed some di fferences in carbon utilization not detected by standard tests of carb on substrates. It is concluded that nutritional screening has promise for identifying genomic groups and various pathovars within the genus Xanthomonas.