What do peptides, galaxies and biofilms have in common?
Chirality of course! If molecules and galaxies can exhibit chirality, then why should bacteria be any different? A team from Copenhagen shed light on to why E. coli biofilms exhibit chirality
- Chirality of E. coli biofilms is dependent on contact with substratum
- Substratum composition and expression of surface proteins both altered biofilm chirality
- Flagella and the direction of peptidoglycan synthesis did not significantly affect chirality
A research group led by Lene Oddershede from the University of Copenhagen investigated chirality in E. coli. Chirality in bacteria is nothing new but is not very well studied. Several research groups have shown that flagellar rotation in E. coli and other flagellated bacteria causes movement in one particular direction. Bacteria such as Myxococcus spp. that exhibit gliding motility have also show to form chiral colonies depending on the direction of the movement of the gliding proteins. The team from Copenhagen have potentially found a new mechanism as they showed that surface proteins and flagella did not contribute to chiral colonies in their model. They argue the surface proteins such as flagella and pilli surround the bacterial cell and prevent it from interacting with the surface. Once these obstructions are removed, the cell surface can interact with the substrate and grown chiral colonies.
The study of chirality is important. As the authors of this work state, it can be a language for the micro to communicate with the macro, in this case, for bacteria to communicate how a biofilm should form. It may also give us clues as to how unicellular organisms work together as well as compete within communities.
From microbial biofilms to human migrations, spatial competition is central to the evolutionary history of many species. The boundary between expanding populations is the focal point of competition for space and resources and is of particular interest in ecology. For all Escherichia coli strains studied here, these boundaries move in a counterclockwise direction even when the competing strains have the same fitness. We find that chiral growth of bacterial colonies is strongly suppressed by the expression of extracellular features such as adhesive structures and pili. Experiments with other microbial species show that chiral growth is found in other bacteria and exclude cell wall biosynthesis and anisotropic shape as the primary causes of chirality. Instead, intimate contact with the substratum is necessary for chirality. Our results demonstrate that through a handful of surface molecules cells can fundamentally reorganize their migration patterns, which might affect intra- and interspecific competitions through colony morphology or other mechanisms.
Chirality in microbial biofilms is mediated by close interactions between the cell surface and the substratum
Munk Vejborg, Rebecca
Korolev, Kirill S
Oddershede, Lene B