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In the periplasm — the space between the inner and outer membranes of a bacteria’s cell wall — defensive proteins that detect a poison assemble like barrel staves to form a tunnel between pumps in the cell’s inner and outer membranes to eject the intruders. Artist’s conception by Ace George Santiago. Credit: Ace George Santiago, Cornell University

By tagging a cell’s proteins with fluorescent beacons, Cornell researchers have found out how E. coli bacteria defend themselves against antibiotics and other poisons. When undesirable molecules show up, the bacterial cell opens a tunnel though its cell wall and “effluxes,” or pumps out, the intruders. “Dynamic assembly of these tunnels has long been hypothesized,” said Peng Chen, professor of chemistry and chemical biology. “Now we see them.”

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