Biofilms are bacterial communities with high antibiotic resistance. Within biofilms, bacteria exchange information chemically - a mechanism called quorum-sensing. Researchers at the Institute de Biologie Structurale in Grenoble, the University of the Mediterranean in Marseille and the Jacobs University in Bremen have shown that the gram-negative pathogen Providencia stuartii forms floating communities within which adjacent cells are in apparent contact,before depositing as canonical surface-attached biofilms. Because porins are the most abundant proteins in the outer membrane of gram-negative bacteria, they hypothesized that they could be involved in cell-to-cell contact and undertook a structure-function relationship study on the two porins of P. stuartii, Omp-Pst1 and Omp-Pst2. The crystal structures reveal that these porins can selfassociate through their extracellular loops, forming dimers of trimers (DOTs) that could enable cell-to-cell contact within floating communities. Support for this hypothesis was obtained by studying the porin-dependent aggregation of liposomes and model cells. The observation that facing channels are open in the two porin structures suggests that DOTs could not only promote cell-to-cell contact but also contribute to intercellular communication. Proteins involved in this interaction could be new targets in the fight against biofilms.
Porin self-association enables cell-to-cell contact in Providencia stuartii floating communities. El-Khatib M, Nasrallah C, Lopes J, Tran QT, Tetreau G, Basbous H, Fenel D, Gallet B, Lethier M, Bolla JM, Pagès JM, Vivaudou M, Weik M, Winterhalter M, Colletier JP. Proceedings of the National Academy of Sciences of the United States of America. 2018 Feb 23. pii : 201714582. doi : 10.1073/pnas.1714582115.