Short chain fatty acids modulate flagella expression in enterohemorrhagic Escherichia coli

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.

Short chain fatty acids modulate flagella expression in enterohemorrhagic Escherichia coli

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.

The Production of Listeriolysin O and Subsequent Intracellular Infections by Listeria monocytogenes Are Regulated by Exogenous Short Chain Fatty Acid Mixtures

Listeria monocytogenes is a foodborne pathogen capable of secreting listeriolysin O (LLO), a pore-forming toxin encoded by the hly gene. While the functions of LLO have been studied extensively, how the production of LLO is modulated by the intestinal environment, devoid of oxygen and enriched in short chain fatty acids (SCFAs), is not completely understood. Using L. monocytogenes strain 10403s, we found that hly transcription was moderately decreased by aerobic SCFA exposures but significantly increased by anaerobic SCFA exposures. Moreover, aerobic, but not anaerobic, exposure to low levels of SCFAs resulted in a significantly higher LLO activity. These results demonstrated that transcriptional and post-transcriptional regulations of LLO production were separately modulated by SCFAs and were responsive to oxygen levels. Examining isogenic mutants revealed that PrfA and SigB play a role in regulating LLO production in response to SCFAs. Effects of SCFAs were also present in the cardiotropic strain 07PF0776 but distinctly different from those in strain 10403s. For both strains, prior exposures to SCFAs altered intracellular infections in Caco-2 and RAW264.7 cells and the plaque sizes in L fibroblasts, a result confirming the ability of L. monocytogenes to adapt to SCFAs in ways that impact its subsequent infection outcomes.