Ethanolamine Utilization and Bacterial Microcompartment Formation Are Subject to Carbon Catabolite Repression

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Ethanolamine (EA) is a nutrient in the GI tract utilized by bacteria like Enterococcus faecalis.
• Enterococcus faecalis possesses ~20 ethanolamine utilization (eut) genes for EA metabolism.
• Regulation of EA utilization is crucial for understanding pathogen behavior.

Purpose of the Study:

• Investigate the role of the small RNA EutX in EA utilization efficacy.
• Determine the function of CcpA in repressing EA utilization in the presence of glucose.
• Analyze the global prevalence of CcpA-mediated regulation on bacterial microcompartment (BMC) operons.

Main Methods:

• Chemically defined medium experiments to assess EA utilization.
• Genetic manipulation (deletion mutants, complementation) to study gene function.
• Bioinformatics analysis of bacterial genomes for regulatory site prediction.

Main Results:

• Loss of EutX increased eut gene expression and BMC formation but repressed growth, indicating reduced EA utilization efficiency.
• CcpA represses EA utilization with glucose, targeting the PeutS promoter via a cre site.
• CcpA influences EA utilization indirectly through the EutV/EutW two-component system.
• Bioinformatics analysis suggests widespread CcpA/cre-mediated carbon catabolite repression of BMC-containing operons.

Conclusions:

• EutX acts as a negative regulator, fine-tuning EA utilization for optimal growth.
• CcpA mediates carbon catabolite repression of EA utilization, ensuring preferred nutrient sources are used first.
• Carbon catabolite repression is a common regulatory mechanism for BMC-associated pathways in bacteria.