As microbiologists and public health officials scramble for weapons to combat antibiotic resistance, they may end up including an unlikely ally in their arsenal: other bacteria. The prime candidate right now is a predatory bacterium known as Bdellovibrio bacteriovorus . Researchers have started to evaluate predatory bacteria such as Bdellovibrio —shown here in a false-color transmission electron microscopy image at 50,000× magnification—as a means of treating intractable, antibiotic-resistant infections. Image credit: Science Source/ALFRED PASIEKA. Found in soils and water globally, B. bacteriovorus are free-living, harmless bacteria—harmless to humans, at least. In the microbial world, they’re voracious predators of gram-negative bacteria, a group that includes Salmonella , Escherichia coli , and several other pathogens. Bdellovibrio punch a hole in the membranes of their prey, enter and consume their contents, then burst out again to find their next meal. “They’re a very efficient killing machine,” says Daniel Kadouri, an associate professor at the Rutgers School of Dental Medicine in Newark, NJ. “They act kind of like the creature in the movie Alien .” Researchers are now beginning to evaluate Bdellovibrio and other similar predatory bacteria as a route to treating intractable, antibiotic-resistant infections. They’re starting to learn how these predators work in different organs and against different pathogens. As they examine various infection scenarios, they are also discovering how these microbes work in concert with the native microbiome and immune cells. Pills full of predatory bacteria won’t replace antibiotics at pharmacies anytime soon. But studying these microbes could help prepare for a future when many antibiotics fail to treat multi-drug-resistant infections. “Right now, the idea that a single injection of live bacteria could be used as therapy seems quite extreme to people,” says microbiologist Elizabeth Sockett of the University of Nottingham in the United Kingdom. “But as we run out of other …