Although we tend to think of them as solitary sojourners of the world, bacteria are actually very social organisms. In fact, the vast majority of bacteria live on surfaces by forming “biofilms”: three-dimensional communities hosting thousands to millions of bacteria of such bustling activity that scientists describe them as “bacterial cities.”
Bacteria form biofilms by attaching to each other on a wide variety of surfaces: the bottom of oceans, lakes or rivers, medical equipment and even internal organs, like the intestine, lungs, and teeth — the latter is the familiar dental plaque, a large source of income for dentists.
In short, biofilms are the preferred lifestyle of bacteria. They grow wide and thick, forming a new, social dynamic among their member microorganisms, while also defending them: biofilms can be notoriously inaccessible to antibiotics, which is why they have drawn a lot of medical research.
But looking at biofilms can also give us clues about broader social dynamics that have shaped the evolution of species across the entire planet, like cooperation, competition etc. And it is such questions that drive the work of Alexandre Persat, director of EPFL’s Microbial Mechanics Lab.