Isolation and characterization of chromosomal mTn 10 insertion mutations affecting K88 fimbriae production in Escherichia coli.

mTn 10 transposon mutagenesis of Escherichia coli producing K88 fimbria was carried out in order to identify host factors involved in the regulation of the fae (K88) operon and the production of K88 fimbriae. Five independent chromosomal insertion mutants were obtained which showed an increased expression of K88 fimbriae. Inverse PCR and nucleotide sequencing were carried out to characterize the mutations. One insertion affected the Ipp gene, encoding the major outer membrane lipoprotein. Another mutation was found to be located in the Irp gene, encoding the 'global' regulatory protein Lrp (leucine responsive regulatory protein). A third mutant was found to affect the expression of rfaF, encoding heptosyltransferase II, which resulted in a partially wild-type and partially Re-Rd1 type of LPS. A fourth mutation affected sseB, a gene involved in serine-sensitivity of E. coli cells. Another mutant contained an insertion in an unknown region of the E. coli genome. The mutants were further characterized with respect to K88 as well as K99 fimbriae production.

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