Bacterial biofilms as model tissues

Ability of bacteria to generate and utilise mechanical forces is pronounced through their whole life cycle. Individual cells deploy forces to attach and move on surfaces. Moving and interacting, bacteria find each other and form microcolonies that consist of several thousands of cells and are held together by a network of active, retractile cell appendages. Such microcolonies are often the functional units of the bacterial existence in natural settings and in the context of disease. We introduce theoretical framework describing the bacterial microcolonies as active viscoelastic materials. We can show that the forces experienced by the cells during colony formation may determine their differentiation and the resistance of the microcolony to the effect of antibiotics. We will discuss how this theory might be also useful in eukaryotic systems such as organoids, tumour spheroids or clustering immune cells. Microcolonies may further develop into even more complex differentiated bacterial communities known as biofilms. There, bacteria embed themselves in the self-secreted extracellular matrix creating an analogue of multicellular tissues. We will outline some future research avenues deepening this analogy and illustrate it with an intriguing example of wound healing in bacterial biofilms.