Send to

Choose Destination
Gene. 1998 Jan 30;207(2):149-57.

Improved allelic exchange vectors and their use to analyze 987P fimbria gene expression.

Author information

University of Pennsylvania School of Veterinary Medicine, Philadelphia 19104, USA.


A series of vectors has been developed to provide improved positive and negative selection for allelic exchange. Based on homologous regions of DNA ranging in size from less than 200 bp to over 1 kb, we have successfully used these new plasmids to introduce or remove markers in chromosomal or plasmid DNA. Wild type fimbria genes were replaced both in Salmonella enteritidis (sefA, agfA and fimC) and Escherichia coli (fasA and fasH). Regulation of 987P fimbriation could be identified after replacement of fasA and fasH with allelic reporter fusions. The expression of fasA but not fasH is dependent upon the osmolarity of the growth medium in an HNS-dependent manner, but unlike some other fimbrial systems expression is not dependent on the exogenous iron concentration.

[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Elsevier Science
Loading ...
Support Center