DIFFERENTIAL CHARACTERIZATION OF AGROBACTERIUM SPECIES USING CARBON-SOURCE UTILIZATION PATTERNS AND FATTY-ACID PROFILES

Pathogenic and nonpathogenic strains of Agrobacterium tumefaciens (i.e ., biovar 1), A. rhizogenes (i.e., biovar 2), A. vitis (i.e., biovar 3 ), and A. rubi were tested for their ability to utilize 95 different c arbon sources available in the GN Microplate system and analyzed for f atty acid content using the MIDI gas-liquid chromatography system. Sev eral carbon sources were identified as being of diagnostic value. With the exception of the A. rubi strain, hydroxy-L-proline and i-erythrit ol were exclusively metabolized by A. tumefaciens and A. rhizogenes, r espectively. Analysis of fatty acid composition confirmed that cis-vac cenic acid (18:1omega cis) is the predominant acid in all the Agrobact erium strains. The amount of 3-hydroxypalmitic acid (16:0 3-OH) differ ed in A. rhizogenes, A. tumefaciens, and A. vitis, providing a quantit ative measure of differentiation; this acid was not detected in A. rub i ICPB TR2. Another fatty acid with diagnostic value was 15:0 iso 3-OH , which was found exclusively in A. rhizogenes cells. Cluster analyses based on fatty acid composition and metabolic fingerprints confirmed the phenotypic differences between members of the four Agrobacterium s pecies investigated; both systems grouped the strains according to the ir respective species. These rapid and simple methods are major improv ements over the classical methods of identification of Agrobacterium s pecies and should prove useful for the rapid classification of large n umbers of bacterial strains, such as those isolated in ecological stud ies.