By KATARINA ZIMMER, in The Scientist.
EDITOR’S CHOICE IN CELL & MOLECULAR BIOLOGY
B.H. Abuaita et al., “Mitochondria-derived vesicles deliver antimicrobial reactive oxygen species to control phagosome-localized Staphylococcus aureus,” Cell Host Microbe, 24:625–36, 2018.
According to biology textbooks, a macrophage engulfs a bacterium, internalizes it in a toxin-filled vesicle called a phagosome, then shuttles the cellular remains to a lysosome for degradation. But killing microbial invaders turns out to be a lot more complex, with other organelles such as mitochondria—the main sites of energy production in the cell—participating in the process.
One piece of evidence for mitochondria’s role surfaced in 2011, when researchers curtailed the production of reactive oxygen species (ROS)—highly destructive molecules that are byproducts of metabolism—in mouse macrophage mitochondria, and found that the immune cells became less effective at killing bacteria. Four years later, immunologist Mary O’Riordan of the University of Michigan Medical School uncovered another piece of the puzzle when she exposed mouse macrophages to the bacterium Staphylococcus aureus. This appeared to activate a particular stress pathway in the cells’ endoplasmic reticulum, which in turn revved up production of ROS.
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