Abstract
Pathogen virulence is largely driven by the evolution and adaptation of the genome. LasR is a master regulator of quorum-sensing (QS) system. The QS-inactive LasR-null mutant regains QS activation in a laboratory evolution experiment through obtaining mutations in mexT, a gene encoding transcriptional regulator. How the QS-active LasR-MexT mutant continuously evolves is still unknown. Here we passaged the LasR-MexT mutant in casein broth and monitored its evolutionary trajectory. By examining the proteolytic phenotype of isolated single colonies, we found a protease-negative subpopulation arising from the parental population. The whole genome sequencing analysis revealed that these protease-negativ colonies bear mutations in pilD gene. In accordance with its role as a prepilin peptidase of type IV system, PilD mutants are defective in twitching motility. In conclusion, we identified a new PilD mutant cheater that evolved from the parental LasR-MexT mutant population. Our work demonstrates that population evolution is highly dynamics, with arising of distinct subpopulations containing different social behaviors.
Competing Interest Statement
The authors have declared no competing interest.
