Pan-genome analysis of the genus Finegoldia identifies two distinct clades, strain-specific heterogeneity, and putative virulence factors.

Finegoldia magna, a Gram-positive anaerobic coccus, is an opportunistic pathogen, associated with medical device-related infections. F. magna is the only described species of the genus Finegoldia. We report the analysis of 17 genomes of Finegoldia isolates. Phylogenomic analyses showed that the Finegoldia population can be divided into two distinct clades, with an average nucleotide identity of 90.7%. One clade contains strains of F. magna, whereas the other clade includes more heterogeneous strains, hereafter tentatively named "Finegoldia nericia". The latter species appears to be more abundant in the human microbiome. Surface structure differences between strains of F. magna and "F. nericia" were detected by microscopy. Strain-specific heterogeneity is high and previously identified host-interacting factors are present only in subsets of "F. nericia" and F. magna strains. However, all genomes encode multiple host factor-binding proteins such as albumin-, collagen-, and immunoglobulin-binding proteins, and two to four copies of CAMP (Christie-Atkins-Munch-Petersen) factors; in accordance, most strains show a positive CAMP reaction for co-hemolysis. Our work sheds new light of the genus Finegoldia and its ability to bind host components. Future research should explore if the genomic differences identified here affect the potential of different Finegoldia species and strains to cause opportunistic infections.