Aren't bugs a source of continuous amazement? Consider, for example, how cunningly bacteria conspire to shanghai the molecular machines of their mammalian hosts for their own goals. Besides serving the bugs, this evil intelligence is exploitable for studying cellular physiology, and the bewildering affinity of bacterial toxins for crucial host cell proteins has taught us many a thing on how cells work.
Perhaps Brucella may help teach us the function of the normal prion protein (1). Brucella species are Gram-negative facultative intracellular pathogens. They invade, resist intracellular killing, and replicate in phagocytic and nonphagocytic cells (2). But how does Brucella initiate replication in macrophages? The contact with the bug instructs the macrophage to internalize it; the mode of internalization (Fcγ and complement receptors vs. uptake of nonopsonized bugs) determines the fate of the bug (2).
Brucella actively modulates its...
