Pathogens employ a range of tactics to outwit host defences, perhaps none more impressive than turning their own cellular machinery against them. Shigella bacteria, which can cause dysentery, a painful form of diarrhoea, have recently been revealed as masters in manipulation. As pictured using a scanning electron microscope, Shigella flexneri (false-coloured green) enter host cells by making contact with their filopodia, long finger-like projections from the cell surface. To achieve this, they get a helping hand from a short segment of nucleotides, known as a microRNA, found in the host cells. This particular microRNA, named miR-29b-2-5p, boosts the development of more filopodia, making it easier for the bacteria to gain access to cells, and promotes their replication once inside. When infection is established, the levels of miR-29b-2-5p decrease, though further research is needed to determine whether this is a result of host defences kicking in, or of another bacterial trick.
Written by Emmanuelle Briolat
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