Abstract: This study was undertaken to identify an unknown resolvase in an E. coli strain lacking RuvABC (N4237) by using transposon mutagenesis. One out of 10000 clones was retained for further study as it was resistant to UV light and mitomycin C. The result of transductional mapping and PCR sequencing showed that Tn10kan inserted upstream of rusA gene and expression of this gene improved survival. Thus, results did not show the presence of new resolvase in E. coli cells.