Lapg Mediates Biofilm Dispersal Invibrio Fischeriby Controlling Maintenance Of The Vcbs-Containing Adhesin Lapv

Efficient symbiotic colonization of the squidEuprymna scolopesby the bacteriumVibrio fischeridepends on bacterial biofilm formation on the surface of the squid's light organ. Subsequently, the bacteria disperse from the biofilm via an unknown mechanism and enter through pores to reach the interior colonization sites. Here, we identify a homolog ofPseudomonas fluorescensLapG as a dispersal factor that promotes cleavage of a biofilm-promoting adhesin, LapV. Overproduction of LapG inhibited biofilm formation and, unlike the wild-type parent, a Delta lapGmutant formed biofilms in vitro. AlthoughV. fischeriencodes two putative large adhesins, LapI (nearlapGon chromosome II) and LapV (on chromosome I), only the latter contributed to biofilm formation. Consistent with thePseudomonasLap system model, our data support a role for the predicted c-di-GMP-binding protein LapD in inhibiting LapG-dependent dispersal. Furthermore, we identified a phosphodiesterase, PdeV, whose loss promotes biofilm formation similar to that of the Delta lapGmutant and dependent on both LapD and LapV. Finally, we found a minor defect for a Delta lapDmutant in initiating squid colonization, indicating a role for the Lap system in a relevant environmental niche. Together, these data reveal new factors and provide important insights into biofilm dispersal byV. fischeri.