Alternative sigma factor sigmaH modulates prophage integration and excision in Staphylococcus aureus

Area of Science:

• Bacteriology
• Virology
• Molecular Biology
• Genomics

Background:

• Bacterial prophages are key components of variable genomic regions, often carrying genes that enhance host virulence and survival.
• This phenomenon is particularly significant in Staphylococcus aureus, a major human pathogen.
• Understanding prophage-bacterial interactions is crucial for controlling pathogen evolution and virulence.

Purpose of the Study:

• To investigate the regulatory mechanism of prophage integration in Staphylococcus aureus.
• To identify the specific host factors involved in controlling prophage gene expression.
• To elucidate the role of prophage integration in bacterial pathogenesis and lysogenic stability.

Main Methods:

• Bioinformatics analysis of conserved regions in staphylococcal prophages.
• Identification and characterization of promoter regions for phage integrase (int) genes.
• In vitro and in vivo experiments using genetic deletion and phage assays to assess the role of sigma factors.

Main Results:

• A conserved 40-bp untranslated region upstream of the int gene contains a promoter for phage integrase.
• The host alternative sigma factor sigma-H (σH) was identified as the key regulator recognizing and initiating transcription from this promoter.
• Deletion of sigH significantly altered int expression, prophage DNA excision, spontaneous lysis, and lysogenization efficiency in S. aureus.

Conclusions:

• A novel mechanism of prophage integration regulated by the host sigma-H factor has been discovered in Staphylococcus aureus.
• Sigma-H plays a critical role in stabilizing the lysogenic state, influencing bacterial-phage dynamics.
• This finding suggests a sophisticated co-evolutionary strategy between staphylococcal prophages and their host bacteria.