Members of the genus Bacteroides are by far the most abundant Gram-negative bacteria in the human gut microbiome. We used mass spectrometry to examine the outer membrane (OM) proteome and secretome of one of the most commonly studied members of the Bacteroides genus, B. fragilis, grown under laboratory conditions. Although we did not identify any novel secretion pathways, we found that this organism uses a very different range of secretion strategies than Proteobacteria such as E. coli. B. fragilis lacks many of the pathways that are widespread among the Protebacteria (e.g., the type II, III and IV pathways) but produces multiple type I secretion systems simultaneously. The substrates of the type I pathways are unknown and cannot be easily predicted based on homology to proteins that are type I substrates in Proteobacteria. B. fragilis also differs dramatically from Proteobacteria in that it produces a large number of lipoproteins that are exposed on the cell surface. We are currently using a variety of methods to investigate the mechanism(s) by which lipoproteins are transported across the OM and identifying targeting signals that earmark specific lipoproteins for export. Interestingly, many of the proteins found in the secretome lack significant homology to proteins that are in the Genbank database and presumably have novel functions.

Project Start
Project End
Budget Start
Budget End
Support Year
7
Fiscal Year
2019
Total Cost
Indirect Cost
City
State
Country
Zip Code
Wilson, Marlena M; Bernstein, Harris D (2016) Surface-Exposed Lipoproteins: An Emerging Secretion Phenomenon in Gram-Negative Bacteria. Trends Microbiol 24:198-208
Pierce, Jessica V; Bernstein, Harris D (2016) Genomic Diversity of Enterotoxigenic Strains of Bacteroides fragilis. PLoS One 11:e0158171
Wilson, Marlena M; Anderson, D Eric; Bernstein, Harris D (2015) Analysis of the outer membrane proteome and secretome of Bacteroides fragilis reveals a multiplicity of secretion mechanisms. PLoS One 10:e0117732