Binding of Mucin by E. coli from Human Gut

Area of Science:

• Microbiology
• Gastroenterology
• Biochemistry

Background:

• Mucin, a major component of the gut mucus layer, plays a crucial role in host-microbe interactions.
• Alterations in the gut microbiota are associated with inflammatory bowel diseases like Crohn's disease.

Purpose of the Study:

• To investigate the in vitro binding of Escherichia coli (E. coli) isolates from healthy volunteers and Crohn's disease patients to mucin.
• To characterize the specificity and kinetics of mucin-bacterial binding.

Main Methods:

• In vitro incubation of E. coli isolates and laboratory strain DH5α with purified mucin.
• Quantification of mucin binding by measuring the decrease in optical absorption of mucin solution.
• Analysis of mucin binding kinetics and inhibition by α-methyl mannoside.
• Visualization of mucin-bacterial interaction using confocal microscopy.
• Assessment of bacterial zeta potential and ATP content.

Main Results:

• E. coli isolates from healthy (N=5) and Crohn's disease (N=5) patients, as well as laboratory strain DH5α, exhibited similar mucin binding capacities (0.02-0.12 mg/mg bacterial dry weight).
• Maximum mucin binding was achieved within 30 minutes, and binding was significantly reduced by 46% in the presence of α-methyl mannoside, indicating specificity.
• Confocal microscopy confirmed intensive mucin binding to a subset of bacterial cells.
• Mucin binding did not significantly alter bacterial zeta potential or intracellular ATP levels, but led to a slight increase in extracellular ATP.

Conclusions:

• E. coli exhibits specific mucin-binding capabilities, potentially mediated by mannose-specific interactions.
• The binding characteristics of E. coli to mucin are comparable between isolates from healthy individuals and Crohn's disease patients.
• These findings contribute to understanding the interaction of E. coli with the gut mucus layer, relevant to gut health and disease.