The Bacillus subtilis sigma D-dependent operon encoding the flagellar proteins FliD, FliS, and FliT

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Bacillus subtilis utilizes flagella for motility.
• Flagellar gene expression is complex and often hierarchical.
• Metalloregulation plays a role in bacterial adaptation.

Purpose of the Study:

• To identify metalloregulated genes involved in Bacillus subtilis flagellar function.
• To investigate the regulatory mechanisms controlling flagellar gene expression.
• To determine the role of iron in flagellar gene regulation.

Main Methods:

• Genetic screening using Tn917-lacZ insertion mutants.
• DNA sequencing to identify gene homologs.
• Transcriptional analysis of fliD-lacZ fusions.
• Assessing gene expression in response to iron and genetic mutations.

Main Results:

• A Tn917-lacZ insertion was identified in a Bacillus subtilis flagellar operon.
• The operon contains homologs of enteric flagellar genes fliD, fliS, and fliT.
• Transcription of the fliD-lacZ fusion is sigma D dependent and repressed by iron.
• Iron repression targets the fliD operon promoter, not sigma D.

Conclusions:

• Bacillus subtilis flagellar gene expression follows a hierarchy similar to enteric bacteria.
• The fliD operon is a sigma D-dependent, metalloregulated class III flagellar gene.
• Iron acts as a repressor of the fliD operon promoter, suggesting a role in coordinating flagellar assembly with nutrient availability.