During biofilm growth P. aeruginosa diversifies into different niche specialists. Small Colony Variant (SCV) is one of these adapted phenotypes which have been characterized as hyperadherent and highly biofilms producer cells. When SCV are grown on solid media, the wild type-like phenotype emerges from the edges of the colony indicating a switch between two phenotypic phases. However, molecular basis underlying SCV conversion and reversion remain unknown.  We have previously obtained evidences for mutator-driven short-term adaptive evolution in biofilms, associated with increased rates of phenotypic diversification. Here, we explore the P. aeruginosa adaptability in long-term evolutionary experiments, by analyzing mutators mismatch deficient and WT strains subjected to controlled, successive and repeated rounds of SCV conversion/reversion by exposing bacteria to alternating cycles of biofilm growth (conversion) and growth in solid media (reversion). Our results suggest that SCV phenotypic switching is based on mutational events and that a high mutation rate do not alter the capacity of mutators to phenotypically switch, even maintaining the high capability of phenotypic diversification throughout the successive rounds of evolution. Whole genome sequencing of ancestral and final clones is being performed in order to evaluate those mutations which are involved in this adaptive process.