Structure and function of the D-galactose network in enterobacteria.

Area of Science:

• Microbiology
• Bacterial Metabolism
• Evolutionary Biology

Background:

• Galactose is crucial for bacterial survival and virulence.
• The Leloir pathway metabolizes galactose in Escherichia coli, regulated by a complex genetic network.
• Comparative genomics can reveal functional adaptations of metabolic pathways in bacteria.

Purpose of the Study:

• To investigate the functional diversity and evolutionary optimization of the galactose utilization network within the Enterobacteriaceae family.
• To understand the specific inactivation of the galactose mutarotase (galM) gene in Yersinia pestis and its implications.

Main Methods:

• Bioinformatic analysis of reference genome sequences from the Enterobacteriaceae family.
• Comparative analysis of galactose utilization gene components across different species.
• Functional assessment of the galM gene in Yersinia pestis, including restoration of activity.

Main Results:

• Several Enterobacteriaceae genomes exhibit reduced components in their galactose utilization network compared to E. coli, indicating environmental optimization.
• In Yersinia pestis, the galM gene is inactivated by a single-base-pair deletion, suggesting differential utilization of galactose anomers (α-D-galactose as a carbon source, β-D-galactose for glycosylation).
• Restoration of galM activity is possible through single-base-pair insertions, and the pseudogene's persistence may offer adaptive advantages.

Conclusions:

• Bacterial galactose utilization networks are adaptable and can be streamlined through gene loss or inactivation.
• The inactivation of galM in Yersinia pestis suggests a specialized metabolic strategy linked to its pathogenic lifestyle.
• The galM pseudogene in Y. pestis might be maintained for potential benefits in specific ecological niches, rather than being a remnant of gene elimination.