Bacteria hijack host cells for infection.

• Position: Tick Bites

Bacteria that cause the tick-borne disease anaplasmosis in humans create their own food supply by hijacking a process in host cells that normally should help kill the pathogenic bugs, scientists have found. This bacterium, Anaplasma phagocytophilum (Ap), secretes a protein that binds with another protein produced by white blood cells, and that connection creates compartments that siphon host-cell nutrients to feed the bacteria, enabling their growth inside the white blood cells.

The finding, detailed in Proceedings of the National Academy of Sciences, defies conventional wisdom about most bacteria, which try to avoid this cellular process. Called autophagy, the process allows a cell to digest parts of itself to produce energy when it is experiencing starvation, but that digestive feature also is enacted by the immune system to help clear away certain intracellular pathogens, including those that cause salmonellosis or shigellosis.

The Ap bacterium, however, launches and then manipulates the autophagy process to its own advantage. 'q-his study shows how bacteria subvert natural processes," indicates Yasuko Rikihisa, lead author of the research and an investigator for Ohio's Center for Microbial Interface Biology.

This activity allows the bacteria to remain hidden from the immune system because the induction of autophagy is considered a normal cell function and it does not produce any...