Enterococci are intestinal facultative anaerobic strains which recognized as opportunistic pathogens. The ability to form biofilms is an important virulence trait that has been reported for Enterococci. Biofilm formation showed differences between E. faecalis strains. However, several factors were involved in this process e.g. the presence of virulence factors, hydrophobicity and heterogeneity. Interestingly, we demonstrated for the first time a biochemical test for a cell surface protein in biofilm formation: addition of the purified N domain of Esp (EspN) to E. faecium E1162Δesp resulted in the restoration of biofilm formation. Streptococcus bovis also, is an intestinal facultative anaerobic bacterium. This organism also has been reported as an opportunistic pathogen causing multiple diseases such as septicemia and endocarditis associated with colorectal cancer (CRC). Although the association of S. gallolyticus infection with CRC is a major issue, the mechanisms behind this link are still unclear. This link between CRC and the virulence of S. bovis strains was studied in more detail in a collaborative project with Dr Harold Tjalsma. The Tjalsma group mainly focussed on host-pathogen interactions, whereas we analysed biofilm formation of S. bovis strains as well as their pathogenicity using the in vivo C. elegans infection model. Our biofilm showed that S. bovis strains form biofilms particularly well on collagen-rich surfaces at least indicate why there is this association. C. elegans experiments also showed that pathogenicity of S. bovis strains is more similar to E. faecalis than to E. faecium in which both S. bovis and E. faecalis have a slow mode of killing that is absent in E. faecium. Full genome sequences of S. gallolyticus UCN34 strain have revealed the presence of a number of potential collagen-binding proteins (e.g., gallo_2179) that are related to the MSCRAMMs family. However, we successfully cloned the gallo_2179 gene in an enterococcal expression vector, and demonstrated transcribed in E. faecalis. Unfortunately, this strain did not form better biofilms on a collagen surface, suggesting either that not sufficient amount of the protein was made, or that the protein is not functional in E. faecalis. In addition, a bioinformatics analysis was performed to identify putatively secreted proteins in S. gallolyticus. Proteins that were expected to be found include for instance three collagen-binding proteins, amylase, tannase and beta lactamase.