Effects of global regulatory proteins and environmental conditions on fimbrial gene expression of F165(1) and F165(2) produced by Escherichia coli causing septicaemia in pigs

Escherichia coli O115:F165 strains are associated with septicaemia in young pigs and possess at least two types of fimbriae. F165(1) fimbriae belong t o the P fimbrial family and F165(2) fimbriae belong to the S fimbrial famil y. Regulatory regions of foo (F165(1)) and fot (F165(2)) fimbrial gene clus ters from wild-type strain 4787 were sequenced and characterised. Expressio n of F165(1) and F165(2) fimbrial genes was analysed by using lacZ and/or l uxAB as reporter genes under the control of the native fimbrial promoters. Differential expression of fimbrial genes was observed. Global regulatory m echanisms such as catabolite repression, responsive regulatory protein (Lrp ), methylation and DNA supercoiling were demonstrated to influence foo and fot expression. foo and fot expression was optimal at 37 degrees C and unde r aerobic conditions. Expression of foo was higher on minimal medium, where as fot expression was higher on complex Luria-Bertani medium. This could re flect an in vivo differential expression. (C) 2000 Editions scientifiques e t medicales Elsevier SAS.