Random transposon mutagenesis of the Saccharopolyspora erythraea genome reveals additional genes influencing erythromycin biosynthesis

Increasing Extracellular Free Fatty Acid Production in Escherichia coli by Disrupting Membrane Transport Systems

Transposon mutagenesis was used to identify three mutants of E. coli that exhibited increased free fatty acid (FFA) production, which resulted from the disruption of genes related to membrane transport. Deletion of envR, gusC, and mdlA individually in a recombinant E. coli strain resulted in 1.4-, 1.8-, and 1.2-fold increases in total FFA production, respectively. In particular, deletion of envR increased the percentage of extracellular FFA to 46%, compared with 29% for the control strain. Multiple deletion of envR, gusC, mdlA, ompF, and fadL had a synergistic effect on FFA production, resulting in high extracellular FFA production, comprising up to 50% of total FFA production. This study has identified new membrane proteins involved in FFA production and showed that genetic engineering targeting these membrane transporters is important to increase both total FFA and extracellular FFA production.

Application of In Vitro Transposon Mutagenesis to Erythromycin Strain Improvement in Saccharopolyspora erythraea

Transposon mutagenesis is an invaluable technique in molecular biology for the creation of random mutations that can be easily identified and mapped. However, in the field of microbial strain improvement, transposon mutagenesis has scarcely been used; instead, chemical and physical mutagenic methods have been traditionally favored. Transposons have the advantage of creating single mutations in the genome, making phenotype to genotype assignments less challenging than with traditional mutagens which commonly create multiple mutations in the genome. The site of a transposon mutation can also be readily mapped using DNA sequencing primer sites engineered into the transposon termini. In this chapter an in vitro method for transposon mutagenesis of Saccharopolyspora erythraea is presented. Since in vivo transposon tools are not available for most actinomycetes including S. erythraea, an in vitro method was developed. The in vitro method involves a significant investment in time and effort to create the mutants, but once the mutants are made and screened, a large number of highly relevant mutations of direct interest to erythromycin production can be found.