LolB is conserved in Bacteroidetes and is crucial for gliding motility and Type IX secretion.Part2

ABSTRACT: In Gram-negative bacteria, lipoproteins are major components of the outer membrane (OM) where they play a variety of roles, from the involvement in β-barrel assembly to virulence. Bacteroidetes, a widespread phylum of Gram-negative bacteria, including free-living organisms, commensals and pathogens, encode an exceptionally high number of outer membrane lipoproteins. These proteins are crucial in this phylum mainly because they are key components of SUS-like nutrient acquisition systems as well as of the Type IX secretion and gliding motility machineries. The transport of lipoproteins to the OM has mainly been studied in E. coli and relies on the Lol system, composed of the inner membrane extraction machinery LolCDE, the periplasmic carrier LolA and the OM lipoprotein LolB. While most Lol proteins are essential and conserved across Gram-negative bacteria, to date, no LolB homologs have been identified outside of γ- and β-proteobacteria. How lipoproteins reach and are inserted in the OM of Bacteroidetes is not known. Here we identified LolB homologs in Bacteroidetes and disclosed the co-existence of several LolA and LolB homologs in several species. We provide evidence that LolA1 and LolB1 of F. johnsoniae are devoted to targeting gliding and T9SS lipoproteins to the OM. A proteomic analysis of the OM composition of the lolA1 and lolB1 deletion strain supports this evidence. Furthermore, we show that, while LolB1 and LolA1 have conserved functions in Bacteroidetes, they are partially functionally different from their E. coli counterparts. We also show that surface lipoprotein transport is LolA and LolB independent. Finally, the finding that, in the absence of LolA and LolB homologs, lipoproteins still localize to the OM, strongly suggests the presence in Bacteroidetes of a yet unidentified Lol-alternative transport pathway. In conclusion, Bacteroidetes seem to have evolved different and probably more complex lipoprotein transport pathways than other Gram-negative bacteria and further research is required to uncover their complexity.

INSTRUMENT(S): timsTOF Pro

ORGANISM(S): Flavobacterium Johnsoniae

SUBMITTER: Marc Dieu  

LAB HEAD: Dr Francesco RENZI

PROVIDER: PXD059642 | Pride | 2025-02-22

REPOSITORIES: pride