Defining chaperone-usher fimbriae repertoire in Serratia marcescens

Chaperone-usher (CU) fimbriae are surface organelles particularly prevalent among the Enterobacteriaceae. Mainly associated to their adhesive properties, CU fimbriae play key roles in biofilm formation and host cell interactions. Little is known about the fimbriome composition of the opportunistic human pathogen Serratia marcescens. Here, by using a search based on consensus fimbrial usher protein (FUP) sequences, we identified 421 FUPs across 39 S. marcescens genomes. Further analysis of the FUP-containing loci allowed us to classify them into 20 conserved CU operons, 6 of which form the S. marcescens core CU fimbriome. A new systematic nomenclature is proposed according to FUP sequence phylogeny. We also established an in vivo transcriptional assay comparing CU promoter expression between an environmental and a clinical isolate of S. marcescens, which revealed that promoters from 3 core CU operons (referred as fgov, fpo, and fps) are predominantly expressed in the two strains and might represent key core adhesion appendages contributing to S. marcescens pathogenesis.

Automated summary

Chaperone-usher (CU) fimbriae are prevalent among Enterobacteriaceae and play key roles in biofilm formation and host cell interactions. This study identified 421 FUPs in 39 S. marcescens genomes, classified them into 20 CU operons, and proposed new nomenclature based on FUP sequence phylogeny. In vivo transcriptional assays showed that promoters from 3 core CU operons are predominantly expressed in environmental and clinical S. marcescens isolates, indicating their potential role in pathogenesis.