STAFFORDSHIRE, U.K.—Increasingly, scientists are using bacteria to produce a variety of products as therapeutics as well as for other applications. Unfortunately, endogenous proteins and metabolic products within the microbes can contaminate and seriously compromise the desired product. With an eye to eliminating the genes that produce these contaminants, scientists at Cobra Biomanufacturing developed a method that offers higher efficiencies than random recombination and does not rely on exogenous recombinases or transposases. They presented their work in Applied and Environmental Microbiology (2006, 72, 2520-2525).
The researchers relied on Xer recombinases, enzymes that naturally occur in most bacterial strains, to remove ("Xer"-cise) target genes in E. coli and B. subtilis strains, and used PCR to confirm their results. With E. coli, they deleted a gene responsible for adding an immunogenic myristoyl group to lipid A and thereby reduced the endotoxicity of the microbe for plasmid DNA production. Similarly, in B. subtilis, they were able to delete the genes responsible for proteases that degrade secreted recombinant proteins.