Bacteria normally live in so-called biofilms - dense multi-species communities of microorganisms embedded in a self made matrix of extracellular polymeric substances. Biofilms are therefore found wherever bacteria are, which is pretty much everywhere. Studying bacterial biofilm formation is important not only to improve our understanding of basic bacterial biology but also due to clinical issues because bacteria residing in biofilms become more tolerant to disinfectants, antimicrobial agents and phagocytosis than their planktonic counterparts. Most research on biofilm biology has so far focused on mono-species biofilms although this hardly reflects what we find in nature. We are therefore, at Section of Microbiology, especially interested in how multi-species biofilms are established and function. In this research topic you will get the opportunity to study how and why different species of bacteria cooperate to form biofilms, if the presence of some species provides a protective effect on other species and hereby shield them from inactivating compounds? Why species incapable of biofilm formation by themselves may be present in multispecies biofilms – which is particular concern with respect to pathogenic bacteria. How the biofilm phenotype affects horizontal gene transfer? And many other pressing questions related to bacterial interactions in multispecies biofilms.