The biosynthetic implications of acetate and glutamate incorporation into (3R,5R)-carbapenam-3-carboxylic acid and (5R)-carbapen-2-em-3-carboxylic acid by Serratia sp.

Two new beta-lactams have been isolated from strains of Serratia and Erwinia sp. and identified as (3R,5R)- and (3S,5R)-carbapenam-3-carboxylic acid. These novel carbapenams lack antibacterial activity, are resistant to both beta-lactamases I and II from Bacillus cereus and are not detected by the lactamase induction assay. Radiolabelled and stable isotope experiments have established that both metabolites together with the antibiotic 5R-carbapenem-3-carboxylic acid are glutamate and acetate derived. A number of possible pathways for the biosynthesis of these compounds as well as their relationship to the more complex members of the carbapenem family of beta-lactam antibiotics are discussed.