Microbial and cellular interactions of flagellate pathogen Salmonella enterica serovar enteritidis and flagellate intestinal resident Roseburia sp with intestinal epithelial cells

• Main Author: Fraser-Pitt, Douglas
• Published: University of Aberdeen 2008
• Subjects: 612.33
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.446222

Flagellin was demonstrated to initiate signalling responses in intestinal epithelial cells resulting in the induction of interleukin-8 (IL-8) and human beta defensin-2 (hBD-2) genes.  Intestinal epithelial cell responses to flagellin isolated from both these organisms and signalling responses to whole bacteria and their mutants was examined. Studies with <i>S. enteritidis </i>mutants confirmed the importance of flagellin in signalling responses in Caco-2 intestinal epithelial cells.  Flagellin was a requirement for the nuclear locations of the transcription factor NF-κB.  IL-8 and hBD-2 gene transcription in response to <i>S. enteritidis </i>was found to be dependent on bacterial cell density.  At high densities there was a down-regulation in the induction of these genes.  This down-regulatory signal was isolated in bacterial cell-free conditioned media.  Experiments with <i>R. intestinalis </i>in a novel anaerobic/aerobic co-culture system also suggested that this organism may regulate aspects of the intestinal epithelial cell response to flagellin.  Proteomic methods were employed to characterise proteins in bacterial cell-free conditioned media produced by <i>S. enteritidis,</i> and also to examine density-dependent changes in the <i>S. enteritidis </i>proteome.  These techniques were also employed to investigate epithelial cell-induced changes in the proteome of flagellate commensal <i>Roseburia hominis.</i> In summary this study confirmed previous published evidence that flagellin is important in signalling responses in Caco-2 cells challenged with <i>S. enteritidis. </i>Novel experiments with commensal <i>R. intestinalis </i>derived flagellin (<i>fliC</i> gene sequenced in this project) showed that it also induced the transcription of IL-8 and hBD-2 genes.