EFFECT OF GROWTH MEDIUM AND PHYSIOLOGICAL AGE ON THE FATTY ACID ANALYSIS OF ERWINIA AMYLOVORA

With the perfection and increasing use of capillary columns in gas-liquid chromatography (GLC), fatty acid analysis may now be used as a primary taxonomic tool in the identification of bactera.
Fatty acid composition and analysis, however, is affected by experimental conditions, the more important of which are defined in this report.

Three strains of Erwinia amylovora (NCPPB-595, RIF-NY and WV-55 Jonnee), were grown at 27 C for 1, 3, and 6 days on 4 different agar media (King’s medium B (KB), nutrient broth agar (NA), tripticase soy agar (TSA) and glucose yeast-extract carbonate agar (GYCA)), and analyzed for total cellular fatty acids by GLC. A loopful of cells from each sample was saponified and methylated in the presence of boron trichloride, and the final ether-hexane extract concentrated almost to dryness under a stream of purified N₂ gas.
Methyl esters were separated on a 0.5 mm x 1 M capillary glass column coated with 3% SP-2100 DOH as a non-polar stationary phase.
Helium carrier gas was adjusted to 30 cc/min and temperature operating conditions were: initial 160 C, final 270 C, program rate 5 C/min.
Fatty acids were classified into one of 7 chemical classes which were the basis of a profile for each sample.

Profiles for all samples averaged 42.9% saturated even-carbon straight chains, 5.1% saturated odd-carbon straight chains, 34.3% unsaturated acids, 6.3% hydroxy-substituted acids, 0.7% branched-chain acids, 3.9% cyclic acids and 5.7% unidentified components.
Major fatty acids were 12:0 (4.9%), 14:0 (4.3%), 16:0 (32.7%), 15:0 (1.8%), 17:0 (2.6%), 16:1 (25.2%), 18:1 (9.1%), 30H-14:0 (6.0%), and cyclic 17:0 (3.7%). Ratios of saturated-to-unsaturated acids and of even-to-odd saturated straight chains averaged 1.45 and 20.32, respectively.

Saturated and odd-carbon and cyclic fatty acids were most affected by growth medium.
On NA and TSA average percentage of saturated odd-carbon and cyclic acids were 7–10% and 4–5%, respectively.
On KB and GYCA the averages were 1–2% and 2–3%, respectively.
Ratios of even-to-odd saturated straight chain acids were above 30 for NA and TSA, and below 6.5 for KB and GYCA.

IV International Workshop on Fire Blight

F. J. Casano, J.M. Wells, T. van der Zwet

https://doi.org/10.17660/ActaHortic.1987.217.4