Different Cellular Origins and Functions of Extracellular Proteins from Escherichia coli O157:H7 and O104:H4 as Determined by Comparative Proteomic Analysis

Abstract

Extracellular proteins play important roles in bacterial interactions with the environmental matrices. In this study, we examined the extracellular proteins from Escherichia coli O157:H7 and O104:H4 by tandem mass spectrometry. We identified 500 and 859 proteins from the growth media of E. coli O157:H7 and O104:H4, respectively, including 371 proteins common to both strains. Among proteins that were considered specific to E. coli O157:H7 or present at higher relative abundances in O157:H7 medium, most (57 of 65) had secretion signal sequences in their encoding genes. Noticeably, the proteins included locus of enterocyte effacement (LEE) virulence factors, proteins required for peptidyl-lipoprotein accumulation, and proteins involved in iron scavenging. In contrast, a much smaller proportion of proteins (37 of 150) that were considered specific to O104:H4 or presented at higher relative abundances in O104:H4 medium had signals targeting them for secretion. These proteins included Shiga toxin 2 subunit B and O104:H4 signature proteins, including AAF/1 major fimbrial subunit and serine protease autotransporters. Most of the abundant proteins from the growth medium of E. coli O104:H4 were annotated as having functions in the cytoplasm. We provide evidence that the extensive presence of cytoplasmic proteins in E. coli O104:H4 growth medium was due to biological processes independent of cell lysis, indicating alternative mechanisms for this potent pathogen releasing cytoplasmic contents into the growth milieu, which could play a role in interaction with the environmental matrices, such as pathogenesis and biofilm formation. IMPORTANCEIn this study, we compared the extracellular proteins from two of the most prominent foodborne pathogenic E. coli organisms that have caused severe outbreaks in the United States and in Europe. E. coli O157:H7 is a well-studied Shiga toxigenic foodborne pathogen of the enterohemorrhagic pathotype that has caused numerous outbreaks associated with various contaminated foods worldwide. E. coli O104:H4 is a newly emerged Shiga toxigenic foodborne pathogen of the enteroaggregative pathotype that gained notoriety for causing one of the most deadly foodborne outbreaks in Europe in 2011. Comparison of proteins in the growth medium revealed significant differences in the compositions of the extracellular proteins for these two pathogens. These differences may provide valuable information regarding the cellular responses of these pathogens to their environment, including cell survival and pathogenesis. E scherichia coli is a diverse species of bacteria including several pathotypes that cause a variety of diseases in humans. Enterohemorrhagic E. coli (EHEC) is responsible for numerous outbreaks of human enterohemorrhagic disease caused by consumption of contaminated food, including meat and fresh vegetables. The primary reservoirs of the most extensively studied EHEC serotype O157:H7 are cattle and other ruminants (1, 2), but E. coli O157:H7 also is capable of long-term survival in various ...

Quantification of enterohemorrhagic Escherichia coli O157:H7 protein abundance by high-throughput proteome

“…However, the true role of these genes in the EHEC pathogenesis remains unclear. Although tellurium is absent from the EHEC niche, interestingly, proteomic studies have detected tellurium resistance proteins in EHEC O157 proteome in different media and growth conditions such as D-MEM [49], minimal medium [50], CHROMagar STEC [51], bovine fluid rumen [39] and under conditions that stimulate the quorum sensing pathway [52]. Despite the several studies in this area, more efforts are necessary to unveil the true role of the tellurium resistance proteins in EHEC pathogenesis.…”

Quantification of EnterohemorrhagicEscherichia coliO157:H7 proteome using TMT-Based Analysis

“…However, the true role of these genes in the EHEC pathogenesis remains unclear. Although tellurium is absent from the EHEC niche, interestingly, proteomic studies have detected tellurium resistance proteins in EHEC O157 proteome in different media and growth conditions such as D-MEM (46), minimal medium (47), CHROMagar™STEC (48), bovine fluid rumen (36) and under conditions that stimulate the quorum sense pathway (49). Despite the several studies in this area, more efforts are necessary to unveil the true role of the tellurium resistance proteins in EHEC pathogenesis.…”

Comparison of Enzyme Secretion and Ferulic Acid Production by Escherichia coli Expressing Different Lactobacillus Feruloyl Esterases

“…In addition, the third type feruloyl esterases were highly secreted in the early stage, and then rapidly degraded in the later stage. This might be due to the extracellular protease produced by E. coli ( Islam et al, 2016 ). Construction of protease-resistant mutants via predicting the action site of protease provides a method to prevent the feruloyl esterase degradation.…”