Pyrimidine Nucleoside Salvage Confers an Advantage to Xenorhabdus nematophila in Its Host Interactions

Xenorhabdus nematophila is a mutualist of entomopathogenic nematodes and a pathogen of insects. To begin to examine the role of pyrimidine salvage in nutrient exchange betweenX. nematophila and its hosts, we identified and mutated anX. nematophila tdk homologue.X. nematophila tdk mutant strains had reduced virulence towardManduca sexta insects and a competitive defect for nematode colonization in plate-based assays. Provision of a wild-typetdk allele intrans corrected the defects of the mutant strain. As inEscherichia coli ,X. nematophila tdk encodes a deoxythymidine kinase, which converts salvaged deoxythymidine and deoxyuridine nucleosides to their respective nucleotide forms. Thus, nucleoside salvage may confer a competitive advantage toX. nematophila in the nematode intestine and be important for normal entomopathogenicity.