TnAraOut is a mariner-based transposon containing an arabinose-inducible promoter P-BAD facing outward. TnAraOut mutagenesis previously used to identify essential genes in Vibrio cholerae can also be used to identify in vitro essential genes in Salmonella enteritidis. A mutant screen was conducted based on the assumption that a mutant-harboring TnAraOut insertion in the promoter region of an essential gene should exhibit arabinose-dependent growth phenotype. Among five isolated mutants with such growth phenotype, DNA sequencing revealed that two of them have insertions in the upstream region of atpI and the coding region of yigP gene such that P-BAD promoter drives the expression of the downstream gene(s). Growth assay showed that the growth defects of these two mutants were fully restored by arabinose induction.