HEp-2 cells infected with Escherichia coli express the inv gene from the invasive bacterial pathogen 
Yersinia enterocolitica. Data were recorded from a computer-controlled confocal laser microscope 
and processed on a graphics display terminal. The HEp-2 cells (green) were stained with the 
actin-speciflc stain FITC-phallicidin, while the invasin- bearing bacteria (red) were visualized by 
indirect immunofluorescence using antisera against E. coli outer-membrane proteins. Areas of 
extensive overlap appear yellow. Results indicate that actin, a major component of the cytoskele- 
ton that controls cell shape and movement, accumulates in the region of entering bacteria. 
From Young, V.B., Falkow, S., and Schoolnik, G.K. 75>i)2. J Cell Biol 116:197-207, by copyright 
permission of the Rockefeller University Press. 
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