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Abstract

Vibrio cholerae is the causative agent of the diarrheal disease cholera,
for which biofilm communities are considered to be environmental
reservoirs. In endemic regions, and after algal blooms, which may result
from phosphate enrichment following agricultural runoff, the bacterium
is released from biofilms resulting in seasonal disease outbreaks.
However, the molecular mechanism by which V. cholerae senses its
environment and switches lifestyles from the biofilm-bound state to the
planktonic state is largely unknown. Here, we report that the major
biofilm scaffolding protein RbmA undergoes autocatalytic proteolysis via
a phosphate-dependent induced proximity activation mechanism.
Furthermore, we show that RbmA mutants that are defective in
autoproteolysis cause V. cholerae biofilms to grow larger and
mechanically stronger, correlating well with the observation that RbmA
stability directly affects microbial community homeostasis and
rheological properties. In conclusion, our biophysical study
characterizes a novel phosphate-dependent breakdown pathway of RbmA,
while microbiological data suggest a new, sensory role of this biofilm
scaffolding element.