Bacteria were once thought of as solitary individual organisms. We are finding out more and more that they behave quite contrary to this long-time perception. Bacteria form complex three-dimensional communities called biofilms. In biofilms, cells stick to each other and are encased in a sticky, slimy matrix proteins and sugars. It has been known for some time that cells within a biofilm communicate with one another. Now, researchers from the University of California San Diego and Universitat Pompeu Fabra determined for the first time, that neighboring biofilm communities communicate with one another to share resources.
The researcher monitored growth of Bacillus subtilis biofilms alone and in proximity to one another.
When one biofilm is grown alone, it oscillates between periods of growth and periods of stress where growth ceases. Growth of a biofilm results in nutrient stress in the interior of the biofilm as they become further away from the edge of the biofilm (where the nutrients are). This stress causes the cells in the interior of the biofilm to release an electrical signal that causes the whole biofilm to stop growing. These electrical signals have been shown to reach beyond the biofilm. Thus, could they influence the behavior of neighboring biofilms?
When given more than enough nutrients, the two biofilm communities feed at the same time. The oscillations between growth and growth arrest are in sync between the two biofilms (resource-splitting). However, under nutrient starved conditions, the communities take turns feeding. While one community is feeding and growing, the other biofilm takes a break (time-sharing).
Surprisingly, the two communities grew faster when nutrients were limited (time-sharing) than when nutrients were plentiful (resource-splitting). By taking turns to feed, each biofilm gets access to all nutrients instead of only half of the nutrients when they feed at the same time.
This research has opened the doors to many questions into the way of life in bacterial communities. What happens when a third bacterial community is added to the mix? Does time-sharing only occur between communities of the same species? Would two biofilms of different species take turns feeding or would they compete? Bacteria have been surprising us in many ways. Now, we’ve learned that they may have been time-sharing longer than humans have.
