FIG 2.

Allelic exchange using pSIE1. (A) pSIE1 plasmid, including the dual-effector negative selection cassette (dark blue), machinery for pir-dependent replication, conjugation, and antibiotic resistance in E. coli (dark gray), and a selectable marker for recipient Bacteroides species (light gray). Relevant restriction sites are indicated. (B) Allelic exchange methodology. Regions of homology included in the pSIE1 plasmid are marked with white letters, while the genomic sequence is marked with black letters. Gent, gentamicin; Erm, erythromycin.