REGULATION OF TYPE-1 FIMBRIAL EXPRESSION IN UROPATHOGENIC ESCHERICHIA-COLI - HETEROGENEITY OF EXPRESSION THROUGH SEQUENCE CHANGES IN THE FIM SWITCH REGION
Jbs. Leathart et Dl. Gally, REGULATION OF TYPE-1 FIMBRIAL EXPRESSION IN UROPATHOGENIC ESCHERICHIA-COLI - HETEROGENEITY OF EXPRESSION THROUGH SEQUENCE CHANGES IN THE FIM SWITCH REGION, Molecular microbiology, 28(2), 1998, pp. 371-381
Over 80% of uropathogenic Escherichia coli express type 1 fimbriae. Ex
pression is phase variable, and regulation of phase switching can diff
er between isolates. Previously, this was explained by differences in
the expression of the fim recombinases, FimB and FimE. Our study of 50
uropathogenic E. coli isolates confirms variation in the regulation o
f type 1 fimbriae but, in many cases, the variation could be accounted
for by sequence changes within and adjacent to the fim switch, rather
than by differences in recombinase expression. This was demonstrated
by moving the switch from the isolates into an isogenic background and
comparing the switching behaviour with that of the original isolate.
Isolates could be arranged into groups based on firn switch regulation
and sequence similarity. In certain cases, the altered regulation was
located to specific basepair changes within the fim switch. Sequence
changes were found that had a marked effect on the activity of either
FimB or FimE switching, while others affected FimB switching in only o
ne direction. These results emphasize the value of using naturally sel
ected sequence variation to further the understanding of gene regulati
on.