title: Environmental signals implicated in Dr fimbriae release by pathogenic Escherichia coli.
abstract: Afa/Dr diffusely adhering Escherichia coli have been shown to cause urinary tract infections and enteric infections. Virulence of Dr-positive IH11128 bacteria is associated with the presence of Dr fimbriae. In this report, we show for the first time that the Dr fimbriae are released in the extracellular medium in response to multiple environmental signals. Production and secretion of Dr fimbriae are clearly thermoregulated. A comparison of the amounts of secreted fimbriae showed that the secretion is drastically increased during anaerobic growth in minimal medium. The effect of anaerobiosis on secretion seemed to depend on both the growth phase and the culture medium. The secretion was maximal during the logarithmic-phase growth and corresponded to 27 and 57% of total Dr fimbriae produced by bacteria grown in mineral medium+glucose and LB broth, respectively. Thus, the anaerobic environment of the colon would favour the secretion of Dr fimbriae during bacterial multiplication. The controlled release of the Dr fimbriae, which is carried out in the absence of cellular lysis, appears independent of the action of proteases or a process of maturation. The mechanism employed in the liberation of Dr fimbriae thus seems different from that described for the adhesins FHA and Hap of Bordetella pertussis and Haemophilus influenzae.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale (INSERM) Unité 510, Faculté de Pharmacie, Université Paris XI, F-92296 Châtenay-Malabry, France.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Diard
authors.forename: Ana Luisa
authors.initials: AL
authors.lastname: Toribio
authors.forename: Yap
authors.initials: Y
authors.lastname: Boum
authors.forename: Florence
authors.initials: F
authors.lastname: Vigier
authors.forename: Imad
authors.initials: I
authors.lastname: Kansau
authors.forename: Odile
authors.initials: O
authors.lastname: Bouvet
authors.forename: Alain
authors.initials: A
authors.lastname: Servin
mesh_terms: D018830:Adhesins, Escherichia coli / Q000378:metabolism; D000693:Anaerobiosis; D001422:Bacterial Adhesion; D018938:Caco-2 Cells; D003470:Culture Media / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism*; D010861:Fimbriae, Bacterial / Q000378:metabolism*; D006801:Humans; D021381:Protein Transport; D013696:Temperature; D037521:Virulence Factors / Q000378:metabolism*
chemical_list: D018830:Adhesins, Escherichia coli; D003470:Culture Media; C465564:Dr adhesin, E coli; D037521:Virulence Factors