Bile salts are prevalent in the mammalian intestine, a natural habitat of E
scherichia coli. The bile salts deoxycholate, chenodeoxycholate, ursodeoxyc
holate, and glycocholate were tested for their effect on induction of 13 sp
ecific stress response genes. The most consistently activated E. call promo
ters were those for genes micF, osmY, and dinD. MicF and osmY gene products
are associated with membrane functions and are responsive to oxidative str
ess. DinD is induced by DNA damage as part of the SOS response. These resul
ts indicate that bile acids, to which E. call are naturally exposed, induce
expression of specific stress response genes, possibly in response to memb
rane perturbation, oxidative stress, and DNA damage. Altered expression of
stress-response genes may also promote interaction of E. coli with cells of
the colonic epithelium.