D-galactonate metabolism in enteric bacteria: a molecular and physiological perspective

D-galactonate, a widely prevalent sugar acid, was first reported as a nutrient source for enteric bacteria in the 1970s. Since then, decades of research enabled a description of the modified Entner-Doudoroff pathway involved in its degradation and reported the structural and biochemical features of its metabolic enzymes, primarily in Escherichia coli K-12. However, only in the last few years, the D-galactonate transporter has been characterized, and the regulation of the dgo operon, encoding the structural genes for the transporter and enzymes of D-galactonate metabolism, has been detailed. Notably, in recent years, multiple evolutionary studies have identified the dgo operon as a dominant target for adaptation of E. coli in the mammalian gut. Despite considerable research on dgo operon, numerous fundamental questions remain to be addressed. The emerging relevance of the dgo operon in host–bacterial interactions further necessitates the study of D-galactonate metabolism in other enterobacterial strains.