In vitro formation of a catabolic plasmid carrying Klebsiella pneumoniae DNA that allows growth of Escherichia coli K-12 on 3-hydroxybenzoate.

The four enzymes needed to convert 3-hydroxybenzoate to pyruvate and fumarate via the gentisate pathway, as well as a putative positive regulator protein, were encoded on an 8 kb Sphl fragment of Klebsiella pneumoniae DNA. The five genes were clustered in the order regulator-gentisate dioxygenase-fumarylpyruvate hydrolase-3-hydroxybenzoate monooxygenase-maleylpyruvate isomerase (mhbRDHMI), with the catabolic genes transcribed in the dioxygenase to isomerase direction. 2-Hydroxybenzoate was found to be a non-metabolizable inducer analogue for the mhb genes, supporting the view that gentisate rather than maleylpyruvate was the physiological inducer. The plasmid pNDR20 encoding the full gentisate catabolic pathway endowed Escherichia coli with the ability to grow on 3-hydroxybenzoate but the host cell appeared to be responsible for substrate uptake.