Surface topology affects wetting behavior of Bacillus subtilis biofilms

The colonization of surfaces by bacterial biofilms constitutes a huge problem in healthcare and industry. When attempting biofilm inactivation or removal, it is crucial to sufficiently wet the biofilm surface with antibacterial agents; however, certain biofilms efficiently resist wetting, and the origin of this behavior remains to date unclear. Here, we demonstrate that, depending on the growth medium used, the model bacterium Bacillus subtilis can form biofilm colonies with distinct surface properties: we find either hydrophilic or two variants of hydrophobic behavior. We show that those differences in biofilm wetting correlate with distinct surface topologies which, in turn, give rise to different physical wetting regimes known from lotus leaves or rose petals. Forming biofilms with different wetting properties may help bacteria to survive in both arid and humid conditions. Furthermore, converting the surface polarity of a biofilm could facilitate their removal from surfaces by increasing their wettability. Biofilm structure: Surface control of wetting A biofilm’s surface structure affects its susceptibility to wetting, influencing persistence and suggesting strategies for biofilm removal. Effective wetting of biofilm surfaces is essential for combatting them with antibacterial agents. Resistance to the procedures currently available for removing biofilms is a huge problem in healthcare. Researchers in Germany led by Oliver Lieleg at the Technical University of Munich found that Bacillus subtilis bacteria can form colonies with different surface structures that either resist or assist wetting. This structural variability in their biofilms may allow the bacteria to adapt to survive in either arid or humid conditions. The insight that environmental conditions can influence biofilm wettability should spur research to control this natural variation. Learning how to convert biofilms into more readily wetted forms may greatly assist their removal in healthcare situations.