The biofilm matrix is like a glue that holds individual bacteria together and allows them to form structured communities. The biofilm structure protects cells from external insults and may optimize access to oxygen. Using the pathogen Pseudomonas aeruginosa, the Dietrich lab tested the importance of matrix production for the competitive fitness of individual bacteria within a biofilm. The ability of non-matrix-producing bacteria to exploit matrix production by their neighbors (i.e., to “cheat”) depended on the type of biofilm formed, e.g. on agar in a Petri dish or on the surface of standing liquid in a tube. Furthermore, the capacity for matrix production evolved along distinct trajectories in different biofilm environments, highlighting the advantage of facultative regulation of central features, such as the ability to make matrix. The image shows colony biofilms in which mutants with different capacities for matrix production and evolutionary histories were mixed and distinguished by differential labeling with green fluorescent protein.
Madsen JS, Lin YC, Squyres GR, Price-Whelan A, de Santiago Torio A, Song A, Cornell WC, Sørensen SJ, Xavier JB, Dietrich LE.
Appl Environ Microbiol. 2015 Dec 15;81(24):8414-26. doi: 10.1128/AEM.02628-15. Epub 2015 Oct 2.