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.jpg): Failed to open stream: No such file or directory in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 117 Front+Microbiol
2018 ; 9
(ä): 1325
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Non-pathogenic Escherichia coli Enhance Stx2a Production of E coli O157:H7
Through Both bamA-Dependent and Independent Mechanisms
#MMPMID29973923
Xiaoli L
; Figler HM
; Goswami Banerjee K
; Hayes CS
; Dudley EG
Front Microbiol
2018[]; 9
(ä): 1325
PMID29973923
show ga
Intestinal colonization by the foodborne pathogen Escherichia coli O157:H7 leads
to serious disease symptoms, including hemolytic uremic syndrome (HUS) and
hemorrhagic colitis (HC). Synthesis of one or more Shiga toxins (Stx) is
essential for HUS and HC development. The genes encoding Stx, including Stx2a,
are found within a lambdoid prophage integrated in the E. coli O157:H7
chromosome. Enhanced Stx2a expression was reported when specific non-pathogenic
E. coli strains were co-cultured with E. coli O157:H7, and it was hypothesized
that this phenotype required the non-pathogenic E. coli to be sensitive to
stx-converting phage infection. We tested this hypothesis by generating phage
resistant non-pathogenic E. coli strains where bamA (an essential gene and Stx
phage receptor) was replaced with an ortholog from other species. Such
heterologous gene replacement abolished the ability of the laboratory strain E.
coli C600 to enhance toxin production when co-cultured with E. coli O157:H7
strain PA2, which belongs to the hypervirulent clade 8. The extracellular loops
of BamA (loop 4, 6, 7) were further shown to be important for infection by
stx2a-converting phages. However, similar gene replacement in another commensal
E. coli, designated 1.1954, revealed a bamA-independent mechanism for toxin
amplification. Toxin enhancement by 1.1954 was not the result of phage infection
through an alternative receptor (LamB or FadL), lysogen formation by
stx2a-converting phages, or the production of a secreted molecule. Collectively,
these data suggest that non-pathogenic E. coli can enhance toxin production
through at least two mechanisms.