| Summary: | 碩士 === 國立陽明大學 === 微生物及免疫學研究所 === 100 === E. coli O157:H7 is the frequently found pathogenic enterohemorrhagic E. coli and is abbreviated as EHEC hereafter. EHEC is transmitted to human through undercooked beef or contaminated food. When EHEC gets into the intestinal tract, these bacteria attach themselves to the epithelial cell and then use type three secretion system (TTSS) to inject effector proteins into the host cells. The effector proteins can induce cytoskeleton rearrangement and physiological changes of the infected cells, which consequently result in destruction of intestinal microvilli. These pathological features are called attaching and effacing lesion (A/E lesion). Based on the images of immunofluorescence and electron microscopy, TTSS injectisomes appear to be distributed over the bacterial surface. To address whether all injectisomes are functioning during the bacterium-host contact, we used fluorescence protein to fuse with an effector protein and two component proteins of the type three secretion machinery. We followed the protein segregations within the bacterial bodies during the infection. Our results indicate that the translocation of Tir has polarity when bacteria make contact with cells. According to our previous studies by time-lapse fluorescence microscopy, the signal of Tir polarization is clustering to one pole of bacterial cell. And the signal seems to be the contact site with the host cell. By colocalization of the signals of EscC, labeled with m-Cherry, and Tir, fused with GFP, we suggest that EHEC, when at the early stage of adhering to a host cell, is actively clustering its Tir to a site near or at the bacterial pole to prepare for a favorable injection where TTS machinery is available.
|
|---|
