Plant-associated Pseudomonas populations: molecular biology, DNA dynamics, and gene transfer.

Bacteria of the genus Pseudomonas are usual colonizers of plant leaves, roots, and seeds, establishing at relatively high cell densities on plant surfaces, where they aggregate and form microcolonies similar to those observed during biofilm development on abiotic surfaces. These plant-associated biofilms undergo chromosomal rearrangements and are hot spots for conjugative plasmid transfer, favored by the close proximity between cells and the constant supply of nutrients coming from the plant in the form of exudates or leachates. The molecular determinants known to be involved in bacterial colonization of the different plant surfaces, and the mechanisms of horizontal gene transfer in plant-associated Pseudomonas populations are summarized in this review.