Fig 1.
Native species of the gut microbiome interact with EHEC by outcompeting the pathogen for crucial nutrients.
However, these microbes also release chemical cues that trigger EHEC’s virulence program, promoting its attachment to the colonic epithelium. The inflammation caused by EHEC alters the metabolic landscape within the colon lumen, disrupting the conditions needed for strictly anaerobic commensals to thrive and alleviating some of the competitive pressure on the pathogen. Figure created with biorender.com.
Fig 2.
EHEC degrades the mucus layer forming a physical barrier between the colon’s lumen and the epithelium through the action of the StcE mucinase and the EspP protease, allowing direct contact between bacteria and epithelial cells.
This contact leads to injections of effectors through the bacterial type three secretion system and strong attachment to the epithelium chiefly involving the Tir/Eae adhesin/receptor protein pair. This adhesion mechanism is supplemented by a wide range of other adhesins reviewed in McWilliams and Torres [27]. Figure created with biorender.com.