DISTURBANCE OF THE BACTERIAL CELL WALL SPECIFICALLY INTERFERES WITH BIOFILM FORMATION

In nature, Bacillus subtilis resides in multicellular communities, also called biofilms. In a biofilm cells are embedded in a self-produced 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. Much research is focusing on small molecules that manipulate and prevent biofilm assembly by modifying cellular signaling pathways. However, the bacterial cell wall, presenting the interface between bacterial cells and their surroundings is largely overlooked. We performed a systematic analysis of cell wall components that specifically disturb biofilm formation with minimal effect on planktonic growth [1]. 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 interfered with the transcription of major biofilm regulators and extracellular matrix genes. However, a careful analysis of the biofilm morphology revealed that these specific cell wall modifications altered the localization and anchoring of the extracellular matrix. In addition, we provide convincing evidences that biofilm hampering by peptidoglycan transglycosylation inhibitors and D-Leucine triggers a highly specific response in the protein profile within the biofilm cells, without changing the overall protein levels or the overall abundance of the extracellular matrix components. The diminished organization of the extracellular matrix through specific interferences with the cell wall highly sensitized biofilms to sterilizing agents. In conclusion, our results emphasize the central role of the Gram-positive cell wall in biofilm development, resistance and sustainment.

[1] Bucher T, Oppenheimer-Shaanan Y, Savidor A, Bloom-Ackermann Z & Kolodkin-Gal I Disturbance of the bacterial cell wall specifically interferes with biofilm formation. Environ Microbiol Rep, 2015