Novel Metabolic Pathways and Regulons for Hexuronate Utilization in Proteobacteria.

Area of Science:

• Microbiology
• Genomics
• Biochemistry

Background:

• Bacterial carbohydrate catabolism, particularly hexuronates and aldarates, exhibits significant variability in pathways and regulatory mechanisms across species.
• Understanding these pathways is crucial for comprehending microbial metabolism and adaptation.

Purpose of the Study:

• To reconstruct d-galacturonic and d-glucuronic acid catabolic pathways and their transcriptional regulons in proteobacteria.
• To identify novel enzymes, transcription factors, and transporters involved in hexuronate and aldarate utilization.

Main Methods:

• Comparative genomics for pathway and regulon reconstruction.
• Bioinformatic analysis of gene context and regulatory elements.
• In vitro validation of DNA-binding motifs and enzyme activities.
• Gene expression studies under different growth conditions.

Main Results:

• Reconstruction of novel catabolic networks for hexuronates and aldarates, including new transcription factors (e.g., GguR) and enzymes.
• Identification and characterization of two novel lactonase enzyme families (UxuL, UxuF) in the oxidative pathway.
• Validation of GguR and GudR DNA-binding specificities and their role in regulating utilization genes.
• Confirmation of a novel aldarate transporter (TctC) from the tripartite tricarboxylate transporter family.

Conclusions:

• This study significantly expands the knowledge of bacterial carbohydrate catabolism by uncovering novel components and regulatory strategies.
• The findings highlight the interconnectedness of hexuronate and aldarate catabolic pathways and their coregulation by GguR in proteobacteria.