A big role for a microbial parasite

Cell biologist William Sullivan first turned his attention to a microbial parasite called Wolbachia as an excuse to take his students on a field trip. After reading a paper that suggested Wolbachia was making its way up the California coast via infected Drosophila, Sullivan, who is at the University of California, Santa Cruz, thought the class could explore whether the parasite had reached Santa Cruz County. “We would go to local wineries, collect flies, and bring them back to characterize them,” he recalls. The petal-like structures are heartworm oocytes (red), each with a large nucleus (green). Wolbachia parasites (green flecks) have started to invade. In the center is actin (blue), a protein that forms cell filaments. Image courtesy of Frédéric Landmann and William Sullivan. Sullivan learned a lot about the area’s vineyards and even more about Wolbachia, an intracellular parasite that relies on host cells for survival. His work led to a 2002 paper in Science (1) detailing how the parasite manipulates male chromosomes to gain a selective advantage, and gave rise to Sullivan’s abiding fascination with the biology of this highly successful endosymbiotic interloper. An estimated two-thirds of all insects harbor Wolbachia inside their cells. For some hosts, the microbial pest is a plus: mosquitos that carry it are rendered resistant to RNA viruses, such as dengue and Zika. For other hosts, Wolbachia is a necessity: the threadlike “filarial” worms that cause African River blindness and elephantiasis can’t survive without it. In the last decade, Sullivan and his colleagues have used their expertise in advanced molecular imaging to shed light on how Wolbachia engineers this interdependence by subverting its …