B. Brett Finlay, Ph.D.

Confocal microscopy figure of E. coli adhering to epithelial cells

Color key: (color enhanced microscopy image)

Purple: Pathogen
(E. coli, a disease-causing microorganism)

Yellow: Phosphotyrosine
(receptor that E. coli uses to attach to cells)

Green: Actin
(a contractile protein found in muscle tissue)

This picture represents many of the significant advances we have made in our studies of E. coli interactions with host cells. For example, we realized that the actin structure was actually polarized, in that it had two defined components, an actin stalk and a tip.

The picture also represents the concept of bacteria triggering signals in host cells — including the tyrosine phosphorylation reactions that occur in the host cell in response to the bacteria. The yellow phosphotyrosine protein is the receptor for the bacterium. We originally thought it was the host and were later startled to realize that it was really of bacterial origin. The bacteria actually insert this protein into host cells!

Finally, this picture also represents a significant turning point in the application of fluorescence and confocal microscopy to the study of host/pathogen interactions. We can now look at individual molecules and how they are arranged in the interface between host and pathogen.