title: Isolation and characterization of BTF-37: chromosomal DNA captured from Bacteroides fragilis that confers self-transferability and expresses a pilus-like structure in Bacteroides spp. and Escherichia coli.
abstract: We report the isolation and preliminary characterization of BTF-37, a new 52-kb transfer factor isolated from Bacteroides fragilis clinical isolate LV23. BTF-37 was obtained by the capture of new DNA in the nonmobilizable Bacteroides-Escherichia coli shuttle vector pGAT400DeltaBglII using a functional assay. BTF-37 is self-transferable within and from Bacteroides and also self-transfers in E. coli. Partial DNA sequencing, colony hybridization, and PCR revealed the presence of Tet element-specific sequences in BTF-37. In addition, Tn5520, a small mobilizable transposon that we described previously (G. Vedantam, T. J. Novicki, and D. W. Hecht, J. Bacteriol. 181:2564-2571, 1999), was also coisolated within BTF-37. Scanning and transmission electron microscopy of Tet element-containing Bacteroides spp. and BTF-37-harboring Bacteroides and E. coli strains revealed the presence of pilus-like cell surface structures. These structures were visualized in Bacteroides spp. only when BTF-37 and Tet element strains were induced with subinhibitory concentrations of tetracycline and resembled those encoded by E. coli broad-host-range plasmids. We conclude that we have captured a new, self-transferable transfer factor from B. fragilis LV23 and that this new factor encodes a tetracycline-inducible Bacteroides sp. conjugation apparatus.
authors.affiliation: Departments of Medicine and Microbiology/Immunology and Program in Molecular Biology, Loyola University Medical Center, 2160 S. First Ave., Maywood, IL 60153, USA.
authors.forename: Gayatri
authors.initials: G
authors.lastname: Vedantam
authors.forename: David W
authors.initials: DW
authors.lastname: Hecht
mesh_terms: D001439:Bacteroides / Q000235:genetics; D001441:Bacteroides fragilis / Q000187:drug effects / Q000235:genetics* / Q000648:ultrastructure; D002876:Chromosomes, Bacterial / Q000235:genetics*; D003227:Conjugation, Genetic / Q000235:genetics*; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics; D005822:Genetic Vectors / Q000235:genetics*; D018933:Pili, Sex / Q000235:genetics* / Q000648:ultrastructure; D011995:Recombination, Genetic; D015183:Restriction Mapping; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D013752:Tetracycline / Q000494:pharmacology
chemical_list: D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D013752:Tetracycline