Cloning and characterization of the asd gene of Salmonella typhimurium: use in stable maintenance of recombinant plasmids in Salmonella vaccine strains

Gene. 1990 Sep 28;94(1):29-35. doi: 10.1016/0378-1119(90)90464-3.


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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Bacterial Vaccines
  • Base Sequence
  • Cloning, Molecular
  • Escherichia coli / genetics
  • Genes, Bacterial*
  • Genes, Lethal
  • Genotype
  • Molecular Sequence Data
  • Plasmids*
  • Restriction Mapping
  • Salmonella typhimurium / genetics*
  • Salmonella typhimurium / immunology


  • Bacterial Vaccines