Acyl-AcpB, a FabT corepressor in Streptococcus pyogenes

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Bacterial membranes are vital for cell function and composed of phospholipids synthesized via the Type II fatty acid synthesis (FASII) pathway.
• In Streptococci, FASII gene expression is regulated by the repressor FabT, which is activated by acyl-acyl carrier proteins (ACPs).
• Streptococcus pyogenes possesses two ACPs, AcpA and AcpB, with AcpA's role established but AcpB's function as a corepressor debated.

Purpose of the Study:

• To investigate the role of AcpB as a corepressor for FabT in Streptococcus pyogenes.
• To determine the impact of AcpB deletion on FASII gene expression, membrane fatty acid composition, and bacterial adhesion.

Main Methods:

• Comparative gene expression analysis of wild-type, ΔacpB, and ΔfabT Streptococcus pyogenes strains.
• Growth in the presence or absence of exogenous fatty acids.
• Analysis of membrane fatty acid composition.
• Assessment of bacterial adhesion to eukaryotic cells.

Main Results:

• AcpB was confirmed as the primary corepressor for FabT in S. pyogenes.
• Deletion of AcpB significantly altered membrane fatty acid composition.
• AcpB deletion negatively impacted bacterial adhesion to host cells.
• FASII gene repression involves a corepressor whose gene expression is not repressed by exogenous FAs.

Conclusions:

• Acyl-AcpB plays a crucial role in regulating the FASII pathway in S. pyogenes.
• The control of membrane composition by FASII is essential for bacterial-host interactions.
• This study clarifies the function of AcpB in FASII regulation and its impact on bacterial virulence traits.