Cells are constantly jibber jabbering, sending messages to each other to coordinate behavior, both within a population of single-celled organisms or between cells of an individual multicellular organism. Most of these signals are chemicals that float around in the liquid that surrounds the cells but there recently has been an increased appreciation for cells’ sense of “smell”–how cells respond to chemicals that are present as gasses.
A brand new paper outlines the discovery of “olfaction” in a species of bacteria, Bacillus licheniformis. Trying to save space on a 96 well dish by putting different experiments side by side, the researchers accidentally discovered that even though each experimental strain was separated in its own plastic well, bacteria growing closer to wells that were producing gaseous ammonia were forming more pigment and more vigorous biofilms. As olfaction can be defined at its simplest as responding in some way to volatile chemicals, these bacteria seem to display olfaction, although the details of how the ammonia to biofilm response occurs have not yet been explored.
In higher organisms such as fungi, response to gasses has been better studied, allowing for the creation of genetic parts for synthetic biology that turn on in the presence of volatile acetaldehyde. When the DNA sequence responsible for sensing acetaldehyde from the fungus Aspergillus nidulans is engineered into cultured hamster cells, gene activation can be measured as a function of distance away from the source of acetaldehyde on a plate:
The acetaldehyde-smelling part can be used to activate any gene that the researcher wants, including genes that are required for the cell’s survival. Such a strain would require an acetaldehyde producing strain nearby in order to survive, creating a synthetic ecosystem that communicates through the air!
Being able to listen in to cellular conversations and understanding all the ways that organisms can sense and interact with their environment is amazing and incredibly powerful for the synthetic biology toolbox. Like natural ecosystems, synthetic biological systems made up of multiple engineered strains or even species can create ecosystems that together can do much more than any one species alone.