In the past decades, researchers have been working hard on solving the problem of how individual cells in a multicellular organism organise themselves in structures such as hearts, brains, lungs etc during ontogeny. Although far from fully understood, a picture is slowly emerging of a complex set of control interactions between the genetic commands of the DNA within the cell and protein and RNA information within and among the cells. However, intriguingly it has been known for some time that simple prokaryotic bacteria are capable of self-organising and cooperating into superstructures to form biofilm and those involved in infectious diseases. Scientists from America and Sweden have now investigated this process in detail.

Biofilm consists of layers of bacteria found closely together in large colonies. They often form in response to adverse environmental conditions. The colonies, however, are formed in such a way as to ensure that nutrients are dispersed efficiently among the individual and bacteria and that waste including dead cells can quickly escape the colony. The scientists placed Escherischia coli in a newly developed microfluidic device, which consisted of flow-through channels with chambers between them. Bacterial colonies could then form in the chambers but with free exchange of cells and nutrients between the different chambers.

The researchers found that the growth and motion of cells in the colony were correlated and aligned with the direction of the major waste exit-ways in the colony. Computer simulations showed that such organisation increases the efficiency of waste removal from the colony as well as increasing supply of nutrients to the colony interior. Individual E. coli cells in colonies, furthermore, change their aspect ratios compared to free-living E. coli, which presumably is done to minimise forces acting on cells near the chamber exit and near chamber walls. 

Although not explicitly studied in their experiments, the scientists speculate that the self-organisation observed in their study, can be explained simply by mechanical interactions between the cells and the structure of the chamber. It remains possible that direct mechanical interaction between cells in multicellular organisms can play a role during ontogeny.