In This Issue

Bacterial cells of the same species can communicate with each other to coordinate population control and other activities, a phenomenon known as quorum sensing. Such signaling also occurs between bacterial species, controls collective behavior in eukaryotes such as slime molds, and enables cellular differentiation in multicellular organisms. Wilfried Weber et al. show that cells from one species can communicate across species and kingdoms to establish higherorder ecosystems in which many organisms can coexist. The authors demonstrate these communication systems by engineering ‘‘sender’’ cells that produce volatile compounds, such as aldehydes, that trigger gene expression in the ‘‘receiver’’ cells of another species. The system is nicknamed ‘‘AT&T,’’ for ‘‘airborne transmission of transcription.’’ In one example, Saccharomyces cerevisiae metabolizes glucose to produce ethanol and actealdehyde, which diffuses to a nearby well containing mammalian HEK cells that have been engineered to express -lactamase under control of an acetaldehyde-inducible promoter. The -lactamase degrades ampicillin in the growth medium, which allows Escherichia coli to proliferate, consume nutrients, and suppress HEK growth. The authors propose that this type of communication forms the foundation of such fundamental relations in nature as symbiosis, parasitism, and predator–prey interaction. — K.M.