Genetic Analysis of the aggA Locus Involved in Agglutination and Adherence of Pseudomonas putida, a Beneficial Fluorescent Pseudomonad. C. R. Buell. Department of Biology and Molecular Biology Program, Utah State University, Logan, UT 84322-5305. A. J. Anderson. Department of Biology and Molecular Biology Program, Utah State University, Logan, UT 84322-5305.. MPMI 5:154-162. Accepted 12 November 1991. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1992.

An isolate of Pseudomonas putida, which rapidly adheres to plant roots, is agglutinated by a glycoprotein from root surfaces. Agglutination is prevented and adherence to the root surface is diminished by Tn5 insertion in mutant 5123. Two cosmid clones from wild type P. putida and a 2.7-kbp EcoRI-HindIII subclone present in both cosmid clones restored agglutinability to wild type levels in transconjugants of the nonagglutinable (Agg‾) Tn5 mutant 5123. These three clones increased agglutinability in transconjugants of the parental Agg⁺ isolate. The 2.7-kbp EcoRI-HindIII subclone restored adherence to bean root surfaces of 5123 to wild type levels in a short-term binding assay. Deletion analysis of the 2.7-kbp fragment indicated only 1.45 kbp was necessary for complementation of agglutinability in 5123. This sequence, termed the aggA locus, contains an open reading frame of 1,356 nucleotides encoding a predicted 50,509-Da protein. The distribution of the aggA locus in plant-associated bacteria, as detected through Southern hybridization, is limited to bacteria that express the agglutination phenotype.