Plant growth promoting rhizobacteria (PGPR) exhibit an intricate and interdependent relationship with plants, which involves biotic and abiotic factors of the rhizosphere region other than the two partners. Success of PGPR is dependent on their survival and establishment on the root/rhizosphere. In this article, we have highlighted root colonization and celldensity dependant quorum sensing as the two important factors that play a key role in determining the outcome of the interaction.