Horizontal gene transfer of beta-lactam biosynthesis genes from prokaryotes to eukaryotes.

The antibiotic biosynthesis genes are derived either from gram-positive (e.g. Streptomyces spp.) or gram-negative (e.g. Lysobacter spp.) bacteria. The first two steps of both penicillin and cephalosporin C biosynthesis are catalyzed by the gene products of pcbAB and pcbC. P. chrysogenum harbors one additional gene, penDE (not shown), to perform the last step of penicillin biosynthesis, whereas Ac. chrysogenum has obtained several additional genes for production of cephalosporin C. Genetic engineering approaches have been used to introduce these genes into P. chrysogenum. Chemical engineering approaches have enabled the precursors of both the Ac. chrysogenum and P. chrysogenum biosynthesis pathway to be used for the production of new cephalosporin derivatives.