Distribution, Functional Expression, and Genetic Organization of Cif, a Phage-Encoded Type III-Secreted Effector from Enteropathogenic and EnterohemorrhagicEscherichia coli

Abstract

Enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli (EHEC) inject effector proteins into host cells via a type III secretion system encoded by the locus of enterocyte effacement (LEE). One of these effectors is Cif, encoded outside the LEE by a lambdoid prophage. In this study, we demonstrated that the Cif-encoding prophage of EPEC strain E22 is inducible and produces infectious phage particles. We investigated the distribution and functional expression of Cif in 5,049 E. coli strains of human, animal, and environmental origins. A total of 115 E. coli isolates from diverse origins and geographic locations carried cif. The presence of cif was tightly associated with the LEE, since all the cif-positive isolates were positive for the LEE. These results suggested that the Cif-encoding prophages have been widely disseminated within the natural population of E. coli but positively selected within the population of LEE-positive strains. Nonetheless, 66% of cif-positive E. coli strains did not induce a typical Cif-related phenotype in eukaryotic cells due to frameshift mutations or insertion of an IS element in the cif gene. The passenger region of the prophages carrying cif was highly variable and showed various combinations of IS elements and genes coding for other effectors such as nleB, nleC, nleH, nleG, espJ, and nleA/espI (some of which were also truncated). This diversity and the presence of nonfunctional effectors should be taken into account to assess EPEC and EHEC pathogenicity and tropism.

Cyclomodulins in Urosepsis Strains of Escherichia coli

“…They belonged to phylogroup B1 and harbored no other CM-encoding gene. Cif is an effector protein of the type 3 secretion system (T3SS) encoded by the locus of enterocyte effacement pathogenicity island, and previous observations of the cif gene were restricted to enteropathogenic E. coli (EPEC) and enterohemorrhagic E. coli (EHEC) strains (36,38). The two cif-positive strains of this study were confirmed as EPEC strains by detection of the eae gene but not of stx genes.…”

“…Only one of the two cif genes produced a cytopathic effect. Loukiadis et al reported that 66% of cif-positive E. coli strains did not induce a Cif-related phenotype in eukaryotic cells due to frameshift mutations or an insertion sequence in the cif gene (36). However, a nonfunctional T3SS may also explain the absence of a cytopathic effect.…”

Enterohaemorrhagic Escherichia coli serogroup O111 inhibits NF-κB-dependent innate responses in a manner independent of a type III secreted OspG orthologue

“…The C-terminal part of NleH is 46 % identical to that of the Shigella OspG, which contains the three catalytic motifs involved in the OspG function. EHEC O111 also contains a nleH1-1 homologue (Loukiadis et al, 2008). However, Ruchaud-Sparagano et al (2007) observed that IL-8 secretion by Caco-2 cells was still suppressed when the cells were infected with a CesT-defective mutant that is unable to produce the CesT protein, a chaperone required for NleH translocation.…”

“…These OspGs are distantly related (about 30 % identity) to another T3SS effector family (Fig. 1b), which comprises NleH of Citrobacter rodentium (Garcia-Angulo et al, 2008) and NleH1-1 and/or NleH1-2 of EHEC O157 strain Sakai, EHEC O111, rabbit EPEC Thomson et al (2006) strain E22, and human EPEC strain B171-8 (Loukiadis et al, 2008;Tobe et al, 2006).…”

“…In addition, a repertoire of effector proteins secreted via a type III secretion system (T3SS) is recognized as essential for EHEC virulence as for enteropathogenic E. coli (EPEC) (Garmendia et al, 2005). These effector proteins are coded not only by a pathogenicity island that codes for the T3SS and is called the locus of enterocyte effacement (LEE), but also by other chromosomal loci, mainly exchangeable effector loci (EEL) within lambdoid prophages (Loukiadis et al, 2008;Ogura et al, 2007;Tobe et al, 2006).…”