Cell surface-localized CsgF condensate is a gatekeeper in bacterial curli subunit secretion

Abstract

Curli are functional amyloids present on the outer membrane of E. coli. CsgF is required for the proper assembly of curli. Here, we found that the CsgF phase separates in vitro and that the ability of CsgF variants to phase-separate is tightly correlated with CsgF function during curli biogenesis. Substitution of phenylalanine residues in the CsgF N-terminus both reduced the propensity of CsgF to phase-separate and impaired curli assembly. Exogenous addition of purified CsgF complemented csgF − cells. This exogenous addition assay was used to assess the ability of CsgF variants to complement csgF ‒ cells. CsgF on the cell surface modulated the secretion of CsgA, the curli major subunit, to the cell surface. We also found that the CsgB nucleator protein can form SDS-insoluble aggregates within the dynamic CsgF condensate. We propose that these multicomponent CsgF-B condensates form a nucleation-competent complex that templates CsgA amyloid formation on the cell surface.

CapP mediates the structural formation of biofilm-specific pili in the opportunistic human pathogenBacillus cereus

“…63–65 B. cereus is phylogenetically related to B. subtilis ; however, we suggest that the polymerization of CapP-CalY-TasA amyloid pili is more closely related to the amyloid curli system of E. coli and Salmonella spp. than to the TasA-TapA system of B. subtilis 66–71 . Building upon the novel insights unveiled in this study and the current knowledge on pili polymerization, we propose a revised model for the assembly of biofilm-specific pili in B. cereus (see Graphical abstract), which involves the paralogous proteins TasA and CalY, as well as the biofilm-specific protein CapP.…”

Multi-omics strategy reveals potential role of antimicrobial resistance and virulence factor genes responsible for Simmental diarrheic calves caused by Escherichia coli

“…Previous studies shown that both fimB and fimE were responsible for controlling the expression of type I fimbriae in E. coli ( 95 – 97 ). Swasthi et al ( 98 ) reported that curli were functional amyloids present on the outer membrane of E. coli , while csgB and csgF were required for curli assembly ( 98 ). Four genes (sfaY, sfaE, sfaF, and sfaG) were known to play a vital role in the adhesion of S-fimbriae in the pathogenesis of E. coli meningitis ( 99 ).…”