Generous bacteria

Bacteria share membrane proteins to help out their neighbors, according to findings from Eric Nudleman, Daniel Wall, and Dale Kaiser (Stanford University, Stanford, CA). Thus begins the search for contact-mediated protein sharing in higher organisms.The charitable bugs are myxobacteria, which are rod-shaped cells that use pili to pull themselves forward. Mutants that lack Tgl—an outer membrane lipoprotein needed for pili assembly—cannot move this way. But Kaiser's lab had noticed that their motility was restored upon contacting Tgl-containing cells.

This rapid motility recovery, the group now shows, is due to the direct transfer of Tgl from one cell to another. Exchange is not limited to Tgl; an unrelated lipoprotein called CglB is also transferred, although cytoplasmic proteins do not exchange.

For wild myxobacteria, the exchange might help their pack-like feeding strategy. The hunting bacteria often change direction, which requires the assembly of pili on the opposite end of the cells. “Rather than making more Tgl,” says Nudleman, “they can get it from their neighbors. This might allow for an efficient mechanism for switching polarity.”

The sharing mechanism is still a mystery, as is its applicability in other systems. Nudleman thinks other cooperative bacteria, such as those that form biofilms, potentially share membrane proteins. Exchange between cells in eukaryotic tissues is also possible, but remains to be seen.

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