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An unusual primary sigma factor in the Bacteroidetes phylum
Didier Vingadassalom1, Annie Kolb, Claudine Mayer
1INSERM E0004, Laboratoire de Recherche Moléculaire sur les Antibiotiques, Université Paris VI, 75270 Paris, France.
Molecular Microbiology
|April 28, 2005
Summary
Bacteroides fragilis possesses a unique primary sigma factor, sigma(ABfr), essential for housekeeping gene transcription. This unusual sigma factor, lacking a specific region, functions uniquely within its homologous system.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Bacteroides fragilis housekeeping gene promoters exhibit a unique consensus sequence.
- This suggested the presence of a specific primary sigma factor in B. fragilis.
Purpose of the Study:
- To identify and characterize the primary sigma factor in Bacteroides fragilis.
- To investigate the functional properties of the identified sigma factor.
Main Methods:
- Bioinformatic analysis of the B. fragilis genome to identify rpoD-like genes.
- Gene knockout studies to determine essentiality.
- Protein characterization and functional assays using reconstituted holoenzymes.
Main Results:
- A single essential rpoD-like gene in B. fragilis encodes sigma(ABfr), a 32.7 kDa protein.
- sigma(ABfr) is unusual, lacking region 1.1 and possessing a unique 29-amino acid signature.
- sigma(ABfr) directs transcription initiation only from B. fragilis promoters in homologous systems, not from E. coli promoters.
Conclusions:
- sigma(ABfr) is the primary sigma factor in Bacteroides fragilis and related Bacteroidetes.
- Its unique structural features and promoter specificity highlight its specialized role in bacterial transcription.