title: Cloning and characterization of the asd gene of Salmonella typhimurium: use in stable maintenance of recombinant plasmids in Salmonella vaccine strains.
abstract: The asd mutants of Salmonella typhimurium have an obligate requirement for diaminopimelic acid (DAP) and will undergo lysis in environments deprived of DAP. This has allowed the development of a balanced-lethal system for the expression of heterologous antigens in vaccine strains using vectors containing the wild-type asd gene from Streptococcus mutans and asd mutant Salmonella hosts [Nakayama et al., Biotechnology 6 (1988) 693-697]. We have cloned the asd gene from S. typhimurium, characterized the gene product and used this gene to construct Asd+ expression cloning vectors. In addition we have constructed an asd cassette and a transposon derived from Tn5 that allow the rapid modification of other vectors for use with delta asd vaccine strains of S. typhimurium adding versatility to the Asd+ vector/delta asd host system of plasmid maintenance.
authors.affiliation: Department of Biology, Washington University, Saint Louis, MO 63130.
authors.forename: J E
authors.initials: JE
authors.lastname: Galán
authors.forename: K
authors.initials: K
authors.lastname: Nakayama
authors.forename: R
authors.initials: R
authors.lastname: Curtiss
mesh_terms: D000595:Amino Acid Sequence; D001428:Bacterial Vaccines; D001483:Base Sequence; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D005798:Genes, Bacterial; D005804:Genes, Lethal; D005838:Genotype; D008969:Molecular Sequence Data; D010957:Plasmids; D015183:Restriction Mapping; D012486:Salmonella typhimurium / Q000235:genetics* / Q000276:immunology
chemical_list: D001428:Bacterial Vaccines