M. Mourino et al., THE HHA PROTEIN AS A MODULATOR OF EXPRESSION OF VIRULENCE FACTORS IN ESCHERICHIA-COLI, Infection and immunity, 64(7), 1996, pp. 2881-2884
We constructed hha derivatives from both a clinical uropathogenic Esch
erichia call isolate (strain FVL4) and a wild E. coil strain causing b
ovine diarrhea (strain CCB21) and analyzed the effect of tile hha alle
le on the expression of the different virulence factors exhibited by t
hese strains. Expression of hemolysin and of the Vir antigen was alter
ed in hha mutants. Whereas production of hemolysin by strain FVL4 was
repressed both at a low temperature and at high osmolarity, the hha al
lele accounted for a significant increase of hemolysin production unde
r these conditions. Also, the low temperature-sensitive expression of
the Vir adhesin was modified in hha mutants, which were able to expres
s this adhesin at a low temperature. Expression of other virulence fac
tors, such as cytotoxic necrotizing factor type 1 and 2 toxins, remain
ed unmodified in hha derivatives of strains FVL4 and CCB21.