Bdellovibrio isn’t your average kind of bacteria.

“It has a psychological problem,” jokes Robert Mitchell, a microbiologist and an associate professor at the Ulsan National Institute of Science and Technology in South Korea. “It thinks it’s a virus.”

Though it may have an identity crisis, Bdellovibrio has managed to spread to a wide range of environments, including soil, bodies of water, animals, plants, and humans. And its unique set of oddities has made it rather appealing to researchers, many of whom have realized its potential utility—biomedically, industrially, even environmentally.

Scientists are exploring all sorts of ways to use these Bdellovibrio, largely inspired by its rather strange life cycle. Typically, bacteria work pretty simply. Once they get to an environment with useful nutrients, they spend some time preparing for growth and then they reproduce. Their reproduction is rapid and usually accomplished via binary fission: they split themselves, forming two identical clones.

But Bdellovibrio is parasitic; it reproduces by attacking other bacteria. “It can only finish its life cycle by preying on other bacteria,” says Daniel Kadouri, an associate professor in the Center for Oral Infectious Diseases at Rutgers University. First, the bacterium attaches to the outside of a bacterial cell and drills a hole through the outer membrane. It then enters the cell and begins dissolving and consuming the host cell’s proteins and nucleic acids. “It sits between the inner and outer membranes and starts secreting enzymes that will basically break down the prey from the inside,” Kadouri told Ars. Finally, after feeding on its prey, dividing, and producing multiple progeny, the bacteria burst out of the host cell, tearing it apart in the process.

And Bdellovibrio is very efficient in all this. According to Kadouri, “From one Bdellovibrio bacterium coming in, you can get several coming out.”

So what exactly does science want with a bacteria that eats other bacteria better than any other? Plenty.

Accidental answer

The strange Bdellovibrio and its predatory ways were discovered by accident. In 1962, researchers Heinz Stolp and Heinz Petzold made two mistakes. First, while filtering soil for viruses, the two ran out of the right sized filters. They used a different kind that had much larger pores, and this let some Bdellovibrio through.

Once Stolp and Petzold had filtered their soil samples, they tested the filtered part for viruses by culturing it in a petri dish filled with bacteria. If after 24 hours no sign of viral infection had appeared, the protocol was to trash the samples. And after they used the larger filter, the soil sample showed no viral growth after a day—yet for some reason, they didn’t throw it out. Three days later, they tested it again and found something that was acting a lot like a virus would. That something was Bdellovibrio. Stolp and Petzold only found it because the larger pore filters allowed Bdellovibrio to get through.

Since then, researchers have learned a lot about the organism’s lifestyle, recognizing that it could prove useful in a number of ways.

Gram +/- Bacteria can be divided into two types: gram-positive and gram-negative. The “gram” refers to the Gram staining method, in which a dye called crystal violet is applied to the bacteria. Following some other steps, the bacteria are then rinsed with ethanol or acetone. Gram-positive bacteria hold on to the stain and appear purple under a microscope. This is because they have really thick cell walls made up of a polymer called peptidoglycan that attracts the crystal violet dye. Bacteria can be divided into two types: gram-positive and gram-negative. The “gram” refers to the Gram staining method, in which a dye called crystal violet is applied to the bacteria. Following some other steps, the bacteria are then rinsed with ethanol or acetone. Gram-positive bacteria hold on to the stain and appear purple under a microscope. This is because they have really thick cell walls made up of a polymer called peptidoglycan that attracts the crystal violet dye. Gram-negative bacteria don’t hold on to the stain because they have comparatively thin cell walls with fewer layers of the peptidoglycan. Their cell membrane is also washed away during the ethanol/acetone rinse, exposing the thin cell wall, which has a hard time hanging on to the dye. Some examples of gram-positive bacteria are streptococcus and staphylococcus, while strains like E. coli and N. gonorrhoeae are gram-negative.

One big way Bdellovibrio could help us out is in the fight against multidrug-resistant bacteria. Increasing numbers of bacterial strains are becoming difficult to fight with traditional drugs. With few options left in our toolbox, researchers are looking at non-traditional ways to combat them. And because Bdellovibrio feeds on other bacteria, it makes an appealing alternative to antibiotics.

When discussing the development of drug-resistant bacteria, Kadouri told Ars, “They were always there, but we always had good drugs to treat them with. The bacteria didn’t learn a new trick. They mutate and evolve. That’s what they do.” The problem today is that we put the bacteria in a position that forced them to mutate very rapidly. “What we’re doing is we’re submerging the environment with so many antibiotics, we’re speeding up the process of natural selection,” says Kadouri. And our overuse of antibiotics isn’t limited to hospitals and hand sanitizer. As Kadouri points out, 80 percent of our antibiotics are used in agriculture.

Not only are we pushing these bacteria toward drug resistance, we’re not producing new antibiotics to fight them rapidly enough. “When pharmaceutical companies develop a drug for a chronic disease, people are going to be taking that drug for 40 or 50 years. Whereas with antibiotics, you’ll be taking them for five days and then within two years, the bacteria will become resistant,” says Kadouri. “So where’s the return in investment? It’s kind of the perfect storm.”

But using Bdellovibrio in conjunction with or instead of antibiotics seems to be a viable option. Scientists have tested it against two classes of bacteria (gram-negative and gram-positive) to see how well it fares against them.

Research has shown that many types of gram-negative bacteria fall as prey to Bdellovibrio, which is a gram-negative bacterium itself. But prior to 2013, it wasn’t known how well the bacteria preyed on multidrug-resistant strains of gram-negative bacteria. Kadouri and his team selected 14 different multidrug-resistant strains, using those typically found in a clinical setting. They then tested how well Bdellovibrio brought down the viability of the bacterial strains.

Two different Bdellovibrio strains turned out to be highly effective at reducing the viability of the 14 tested strains, regardless of their resistance to antibiotics. But the fact that we had to do this work at all highlighted what we don’t know—why does Bdellovibrio prey on some bacteria and not others? “To this day, not much is known about the biology of these organisms,” says Mitchell. “We don’t know how they recognize their prey.”