DIFFERENTIATION OF ERWINIA SPECIES IN THE AMYLOVORA GROUP BY CLASS ANALYSIS OF CELLULAR FATTY-ACIDS

Cellular fatty acids of Erwinia species in the Amylovora group (E. amylovora, E. nigrifluens, E. quercina, E. rubrifaciens, E. salicis and E. tracheiphila), grown on King's medium B agar for 1, 3, and 6 days at 28-degrees-C, were analyzed by gas-liquid chromatography, grouped by chemical class, and compared in order to differentiate the species. For the group in general, the average percentage in 1-day-old cells ranged 36.4-41.5% for the saturated straight-chain even-carbon fatty acids (Class A), 0.3-0.7% for saturated straight-chain odd-carbons (Class B), 43.4-53.3% for unsaturated acids (Class C), 4.5-7.1% for hydroxy-substituted acids (Class D), 0.2-2.0% for branched-chain acids (Class E), and 0-7.5% for cyclopropane fatty acids (Class F). Species could be differentiated in 4 sequential steps based on: 1) percentage of the 12 : 0 fatty acid (E. amylovora > 3.6%, E. quercina < 1%); 2) sum of Classes E + F (E. tracheiphila < 0.3%); 3) ratio Class A/(E + F) (E. salicis < 8); and percentage of 18 : 1 (E. rubrifaciens > 14%, E. nigrifluens < 14%). Physiological age significantly affected relative percentages of Classes B, C and F in E. amylovora and E. salicis; of Classes A, C and F in E. quercina; of Class A in E. tracheiphila; and of Class C in E. nigrifluens.