Enterotoxigenic Bacteroides fragilis (ETBF) strains, which produce a 20 kDa zinc metalloprotease toxin (BFT), have been associated with diarrheal disease of animals and young children. Studying a collection of ETBF and non-toxigenic B. fragilis (NTBF) strains, we found that: 1) The bft gene and a second metalloprotease gene (mph) are contained in a ca. 6-kb pathogenicity island (termed B. fragilis pathogenicity island or BfPAI). 2) The BfPAI is integrated between genes, which encode proteins sharing significant homology to mobilization proteins encoded by Bacteroides spp. mobilizable plasmids. 3) The G+C content of the mobilization genes flanking the BfPAI (49 percent) differ substantially from those of the BfPAI (35 percent) and the rest of the B. fragilis DNA (42 percent), indicating that the BfPAI is contained in an additional foreign genetic element, 4) There are three major populations of B. fragilis strains: pattern I strains, containing the BfPAI and flanking element, all are ETBF strains; pattern H strains, lacking the BfPAI and flanking element, all are NTBF strains; and pattern III strains, containing the flanking element but lack the BfPAI, all are NTBF strains, and 5) The BfPAI and its flanking regions are necessary to bft expression. Based on these results, we hypothesize that the BfPAI and flanking regions are important to the pathogenesis of ETBF strains, and that ETBF strains evolved by acquisition of the flanking element and the BfPAI. The long-range goal of this project is to investigate the molecular evolution of ETBF strains and to further understand ETBF disease pathogenesis.
The specific aims of this proposal are: 1) To characterize the BfPAI and its flanking region; and 2) To investigate the molecular evolution of ETBF strains. Our results will advance our understanding of the molecular pathogenesis of ETBF infections and will serve to delineate how ETBF originated during evolution.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI048708-02
Application #
6511402
Study Section
Bacteriology and Mycology Subcommittee 2 (BM)
Program Officer
Schmitt, Clare K
Project Start
2001-06-01
Project End
2005-04-30
Budget Start
2002-05-01
Budget End
2003-04-30
Support Year
2
Fiscal Year
2002
Total Cost
$204,375
Indirect Cost
Name
Johns Hopkins University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
045911138
City
Baltimore
State
MD
Country
United States
Zip Code
21218
Buckwold, Simy L; Shoemaker, Nadja B; Sears, Cynthia L et al. (2007) Identification and characterization of conjugative transposons CTn86 and CTn9343 in Bacteroides fragilis strains. Appl Environ Microbiol 73:53-63
Sears, Cynthia L; Buckwold, Simy L; Shin, Jai W et al. (2006) The C-terminal region of Bacteroides fragilis toxin is essential to its biological activity. Infect Immun 74:5595-601
Franco, Augusto A; Buckwold, Simy L; Shin, Jai W et al. (2005) Mutation of the zinc-binding metalloprotease motif affects Bacteroides fragilis toxin activity but does not affect propeptide processing. Infect Immun 73:5273-7
Franco, Augusto A; Cheng, Rodney K; Goodman, Alan et al. (2002) Modulation of bft expression by the Bacteroides fragilis pathogenicity island and its flanking region. Mol Microbiol 45:1067-77