A relationship between RP4 plasmid acquisition and phenotypic changes in Pseudomonas fluorescens R2fN

The physiological behaviour of Pseudomonas fluorescens strain R2fN was comp ared to that of transconjugants [R2fN(RP4)], and two aggregation phenotypes were identified (Agr(-) and Agr(+)). Agr(+) phenotype is characterized by the appearance of macroscopic aggregates when cells are growing in liquid m edia. Transconjugants exhibited Agr(+) phenotype whereas wild type strain r epresented Agr(-). Evidence is presented to support correlation between Agr (+) phenotype acquisition and the presence of the broad-host range plasmid RP4 in strain R2fN. In addition, according to bacterial adherence to hydroc arbon test the transconjugant cells appeared to be very hydrophilic whereas wild type R2fN cells were hydrophobic.