Bacterial interactions across a porous membrane

Deepening our knowledge about bacterial infections is of high priority in the work against antimicrobial resistance. Many infections are as well polymicrobial, and the different bacterial species are able to affect each other by cell-cell communication. This is a phenomenon that in several cases is known to enhance the virulence and the severity of the infection. Therefore, new approaches to study bacterial interactions are needed. In this project we have designed a bacterial growth chamber with a porous membrane as a separating wall between two bacterial species. This gave us the ability to discriminate what molecules that can be exchanged between the bacterial cultures by choosing the membrane properties. The setup allows the two bacterial cultures to be spatially separated, yet chemically connected via diffusion through the growth medium and the porous membrane. Two different kinds of hydrophilic membranes were chosen for investigation of their performance as filters in this membrane setup for bacterial growth: a block copolymer based membrane with a pore size of 10 nm and commercially available Millipore membranes with two pore sizes of 220 and 450 nm respectively. The studied bacterial interaction is between Pseudomonasaeruginosa and Staphylococcus aureus, two commonly found bacterial species in the lungs of patients with Cystic Fibrosis and in chronic wounds. We could conclude that bacterial interspecies cell-cell communication through a membrane was possible in our setup. Further, a double membrane setup with a water phase in between the membranes, showed the same bacterial interaction. This last setup enabled molecular analysis of the water phase and thereby the signal molecules.