title: Correlative Association between Resident Plasmids and the Host Chromosome in a Diverse Agrobacterium Soil Population.
abstract: Soil samples collected from a fallow field which had not been cultivated for 5 years harbored a population of Agrobacterium spp. estimated at 3 x 10 CFU/g. Characterization of 72 strains selected from four different isolation media showed the presence of biovar 1 (56%) and bv. 2 (44%) strains. Pathogenicity assays on five different test plants revealed a high proportion (33%) of tumorigenic strains in the resident population. All tumorigenic strains belonged to bv. 1. Differentiation of the strains by restriction fragment length polymorphism analysis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of cellular proteins, and utilization patterns of 95 carbon substrates (Biolog GN microplate) revealed a diversified bv. 1 population, composed of five distinct chromosomal backgrounds (chr A, C, D, E, and F), and a homogeneous bv. 2 population (chr B). chr A, B, C, and D were detected at similar levels throughout the study site. According to opine metabolism, pathogenicity, and agrocin sensitivity, chr A strains carried a nopaline Ti plasmid (pTi), whereas chr C strains had an octopine pTi. In addition, four of six nontumorigenic bv. 1 strains (two chr D, one chr E, and one chr F) had distinct and unusual opine catabolism patterns. chr B (bv. 2) strains were nonpathogenic and catabolized nopaline. Although agrocin sensitivity is a pTi-borne trait, 14 chr B strains were sensitive to agrocin 84, apparently harboring a defective nopaline pTi similar to pAtK84b. The other two chr B strains were agrocin resistant. The present analysis of chromosomal and plasmid phenotypes suggests that in this Agrobacterium soil population, there is a preferential association between the resident plasmids and their bacterial host.
authors.affiliation: Institut d'Agronomie, Université des Sciences et Technologies de Blida, 09000 Blida, Algeria; Gulf Coast Research and Education Center, University of Florida, Bradenton, FL 34203 ; and Institut des Sciences Végétales, Centre National de la Recherche Scientifique, F-91198 Gif-sur-Yvette, France.
authors.forename: H
authors.initials: H
authors.lastname: Bouzar
authors.forename: D
authors.initials: D
authors.lastname: Ouadah
authors.forename: Z
authors.initials: Z
authors.lastname: Krimi
authors.forename: J B
authors.initials: JB
authors.lastname: Jones
authors.forename: M
authors.initials: M
authors.lastname: Trovato
authors.forename: A
authors.initials: A
authors.lastname: Petit
authors.forename: Y
authors.initials: Y
authors.lastname: Dessaux