Surface proteins of Finegoldia magna interacting with the human host

University dissertation from Department of Clinical Sciences, Lund University

Abstract: Finegoldia magna is a Gram-positive anaerobe and a member of the normal human microflora. This bacterium is also an opportunistic pathogen and isolated from ~10% of all anaerobic infections. Reoccurring taxonomical changes and the anaerobic growth have contributed to the neglect of F. magna. The present thesis describes the identification and characterization of two novel surface proteins of F. magna.

One of the identified proteins, SufA, is a protease belonging to the subtilase family. This protease cleaves and inactivates the antimicrobial peptide LL-37 and the antibacterial chemokine MIG/CXCL9. Furthermore, the protease cleaves fibrinogen and thereby inhibits fibrin network formation. To our knowledge, the first example of directed mutagenesis of F. magna is presented with the disruption of the sufA gene.

The other identified protein is FAF. This is a cell wall attached α-helical protein that forms hair-like projections on the bacterial surface. FAF is self-associating and contributes to bacterial clumping. FAF also mediates adhesion of the bacterium to basement membranes of human skin by interacting with BM-40. A further function of FAF is blocking of the activity of antimicrobial peptides. The genes encoding faf and sufA are present in a majority of investigated isolates indicating that the proteins have important functions.

In conclusion, the findings presented in this thesis may help explain how F. magna colonizes the human host and causes opportunistic infections.