Single-celled organisms may communicate via radiation. Daniel Fels of the Swiss Tropical Institute in Basel grew the microbe Paramecium caudatum in complete darkness in clear tubes, which prevented the cells from passing chemical messages to one another. Fels discovered the microorganisms could influence the feeding behavior and growth rates of neighbors in other tubes, suggesting that electromagnetic signals were involved. The microbes seemed to use at least two frequencies to communicate, one of which was in the ultraviolet (UV) range. For instance, small populations of paramecia grew significantly better when separated from larger ones by glass that blocks UV light than by quartz glass, which permits UV rays. The cellular structures behind these messages have not yet been identified, but in the April 1 PLoS ONE, Fels suggests that these signals could lead to novel noninvasive medical techniques.