Abstract

During passage through the human gastrointestinal tract, enterohemorrhagic Escherichia coli (EHEC) encounters numerous stresses. EHEC utilizes various strategies to combat and survive these host assaults and possibly employs them as cues about the local microenvironment to enhance infection. This investigation looks at how exposure to changing concentrations of short chain fatty acid mixtures (SCFA) associated with passage through the human small (SI) and large intestines (LI) affects EHEC flagella expression and motility. In addition, the study also examines several two component systems for their involvement with SCFA-induced flagella regulation. The results indicate that SCFA mixture typical of SI may cue increased EHEC flagellar expression and function while SCFA mixture typical of LI, the site of EHEC colonization, may promote diminished flagella expression and function. Overall, this study contributes to our knowledge on how EHEC sense and respond to host environmental signals in a way that may promote to infection.

Highlights

  • 1.1 Microenvironments in human gastrointestinal tractThe human gastrointestinal tract (GIT) includes all the structures between the mouth and the anus, and is composed of variety of complex microenvironments to which commensal and pathogenic bacteria are exposed to during transit and colonization

  • This investigation demonstrates the significance of varying mixtures of short chain fatty acid mixtures (SCFA) as an important motility signal for both pathogenic Escherichia coli (EHEC) and nonpathogenic E. coli

  • This study evaluates the role of selected two-component regulatory system (TCS) in SCFAmodulated motility and flagella expression

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Summary

Introduction

The human gastrointestinal tract (GIT) includes all the structures between the mouth and the anus, and is composed of variety of complex microenvironments to which commensal and pathogenic bacteria are exposed to during transit and colonization. These microenvironments include a number of antimicrobial stresses and bacteria need to find ways to adapt to or overcome these hostile stresses in order to optimize survival and colonization/infection. The stressors in the GIT include but are not limited to gastric acid in the stomach, bile salts in the small intestine and short-chain fatty acids in the small and large intestines Both the native and non-native bacterial species of GIT have adapted and evolved to utilize these stressors to enhance their fitness advantage. These are recognized as different serotypes of E. coli and most commonly defined by specific combination of O (lipopolysaccharide) and H (flagella) surface antigens (Lior 1994)

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