In nature, Bacillus subtilis resides in multicellular
community, also called biofilms. In a biofilm cells are embedded in an
extracellular matrix, a network of biopolymers composed of polysaccharides and
proteins. In gram positive bacteria, the cell wall is the anchor point for the
extracellular matrix (Aguilar et al., 2007). Once a biofilm matures and
conditions in the community get unfavorable, cells return to the planktonic
phase by rejecting the matrix (Kolodkin-Gal et al., 2010).
We performed a systematic analysis of cell wall components
that specifically disturb biofilm formation. Biofilm development was
dramatically disturbed by non-canonical D-amino acids, depletion of cell-wall
polysaccharides and specific interference with peptidoglycan assembly.
Strikingly, none of these cell-wall disturbances affected planktonic growth or
interfered with the expression of major biofilm regulators. A careful analysis
of the biofilm morphology revealed that these cell wall modifications altered
the composition and anchoring of the extracellular matrix. We also observed changes in the global
proteome and cell-wall proteome upon modification of the cell wall. Proteins
involved in assembly of lipid rafts were highly induced.
In conclusion, our work demonstrates that biofilm forming
cells are more sensitive to cell wall modifications. We are now interested to
fully comprehend the molecular mechanisms by which biofilm forming cells
mediate their response to cell wall interferences.
