Non-pathogenic Escherichia coli Enhance Stx2a Production of E. coli O157:H7 Through Both bamA-Dependent and Independent Mechanisms
Open Access
- 15 June 2018
- journal article
- research article
- Published by Frontiers Media SA in Frontiers in Microbiology
- Vol. 9, 1325
- https://doi.org/10.3389/fmicb.2018.01325
Abstract
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.This publication has 70 references indexed in Scilit:
- SPAdes: A New Genome Assembly Algorithm and Its Applications to Single-Cell SequencingJournal of Computational Biology, 2012
- Identification of a target cell permissive factor required for contact-dependent growth inhibition (CDI)Journal of Bone and Joint Surgery, 2012
- A widespread family of polymorphic contact-dependent toxin delivery systems in bacteriaNature, 2010
- The Vibrio cholerae type VI secretion system displays antimicrobial propertiesProceedings of the National Academy of Sciences of the United States of America, 2010
- A Type VI Secretion System of Pseudomonas aeruginosa Targets a Toxin to BacteriaCell Host & Microbe, 2010
- Shiga Toxin 2 Is Specifically Released from Bacterial Cells by Two Different MechanismsInfection and Immunity, 2009
- Human Microbiota-Secreted Factors Inhibit Shiga Toxin Synthesis by Enterohemorrhagic Escherichia coli O157:H7Infection and Immunity, 2009
- Variation in virulence among clades of Escherichia coli O157:H7 associated with disease outbreaksProceedings of the National Academy of Sciences of the United States of America, 2008
- Enhancement of Shiga Toxin Production in Enterohemorrhagic Escherichia coli Serotype O157:H7 by DNase ColicinsApplied and Environmental Microbiology, 2007
- Improved M13 phage cloning vectors and host strains: nucleotide sequences of the M13mpl8 and pUC19 vectorsGene, 1985