<div><p>We are developing a new recombineering system to assist experimental manipulation of the <em>Pseudomonas syringae</em> genome. <em>P. syringae</em> is a globally dispersed plant pathogen and an important model species used to study the molecular biology of bacteria-plant interactions. We previously identified orthologs of the lambda Red <em>bet/exo</em> and Rac <em>recET</em> genes in <em>P. syringae</em> and confirmed that they function in recombineering using ssDNA and dsDNA substrates. Here we investigate the properties of dsDNA substrates more closely to determine how they influence recombineering efficiency. We find that the length of flanking homologies and length of the sequences being inserted or deleted have a large effect on RecTE<sub>Psy</sub> mediated recombination efficiency. These results provide information about the design elements that should be considered when using recombineering.</p> </div
