Related Experiment Video
Updated: Aug 22, 2026

Generation of Enterobacter sp. YSU Auxotrophs Using Transposon Mutagenesis
Published on: October 31, 2014
Tyrosine site-specific recombinases mediate DNA inversions affecting the expression of outer surface proteins of
Katja G Weinacht1, Hazeline Roche, Corinna M Krinos
1Channing Laboratory, Brigham and Women's Hospital, Harvard Medical School, 181 Longwood Avenue, Boston, MA 02115, USA.
Abstract:
The chromosome of Bacteroides fragilis has been shown to undergo 13 distinct DNA inversions affecting the expression of capsular polysaccharides and mediated by a serine site-specific recombinase designated Mpi. In this study, we demonstrate that members of the tyrosine site-specific recombinase family, conserved in B. fragilis, mediate additional DNA inversions of the B. fragilis genome. These DNA invertases flip promoter regions in their immediate downstream region. The genetic organization of the genes regulated by these invertible promoter regions suggests that they are operons and many of the products are predicted to be outer membrane proteins. Phenotypic analysis of a deletion mutant of one of these DNA invertases, tsr15 (aapI), which resulted in the promoter region for the downstream genes being locked ON, confirmed the synthesis of multiple surface proteins by this operon. In addition, this deletion mutant demonstrated an autoaggregative phenotype and showed significantly greater adherence than wild-type organisms in a biofilm assay, suggesting a possible functional role for these phase-variable outer surface proteins. This study demonstrates that DNA inversion is a universal mechanism used by this commensal microorganism to phase vary expression of its surface molecules and involves at least three conserved DNA invertases from two evolutionarily distinct families.
More Related Videos
Related Concept Videos
Conservative Site-specific Recombination and Phase Variation
The recognition sites for Cre recombinase called LoxP...
Translesion DNA Polymerases
TLS polymerases are found in all three domains of life - archaea, bacteria, and eukaryotes. Of the different classes of TLS polymerases, members of the Y family are fitted with specialized structures that...
Coordination of Gene Expression Processes in Bacteria
Exon Recombination
Exon shuffling follows “splice frame rules.” Each exon has three reading...
Nucleotide Excision Repair
Nucleotide Excision Repair
Cells are regularly exposed to mutagens—factors in the environment that can damage DNA and generate mutations. UV radiation is one of the most common mutagens and is estimated to introduce a significant number of changes in DNA. These include bends or kinks in the structure, which can block DNA replication or transcription. If these errors are not fixed, the damage can cause mutations, which in turn can result in cancer or disease depending on which sequences are...

