Stuff of Science Fiction
Phages first caught Ebner's attention in a microbiology lecture where he was struck by the virus' appearance: With its 16-sided geometric head, coiled tail and
spidery tail fibers, a phage looks like something from the Space Age, not nature.
"In a field where a lot of things look like blobs, a phage resembles the Apollo Lunar Module," Ebner says. "They are really bizarre. Ever since I saw one,
I've wanted to work with them."
Adding to their otherworldly oddity are their sophisticated search-and-destroy methods. When a phage detects a host bacterium, it "docks" onto the cell's
surface and deploys a syringe-like device that injects its own genetic material into the cell. The bacterium's inner workings come to a halt, and it
transforms into a phage-making factory, churning out so many new viruses that it eventually explodes, releasing a swarm of phages to hunt other hosts.
Possibly the most common life form on the planet, phages thrive in soil systems; on rivers and oceans, where they float in dense microbial mats; and on
animals and humans. You can ingest thousands of phages just by licking your lips.
But phages remained a well-kept microbial secret until 1917, when Félix d'Hérelle, a French-Canadian microbiologist, investigated the mysterious
disappearance of a bacterial strain he was studying. He deduced that the invisible culprits must be viruses and christened them "bacteriophages," Greek for
D'Hérelle immediately realized the antibacterial potential of phages and was able to prove their effectiveness as a cure for dysentery. For a few decades,
phages were used to treat many kinds of illnesses, including staphylococcal infections, typhoid, cholera and skin diseases.
But phages soon faded from the medical arena, replaced by the discovery of penicillin in 1928 and the subsequent development of antibiotics. Phage
treatment has remained a common form of therapy only in Eastern Europe, particularly Georgia, where an institute founded by D'Hérelle houses an extensive
library of the viruses and still administers phage therapy.
However, phages are making a steady comeback, aided in part by the high cost of developing antibiotics and the rise of antibiotic-resistant pathogens.
Even though bacteria can also evolve ways of fending off phages, the viruses respond by altering their attack strategies—an arms race among microbes.
Still, Ebner is probing how bacteria become resistant to phages and whether resistance might pose problems for the long-term use of phage therapy.
"Phages are not a substitute for antibiotics," he says. "But when used in the right contexts, they're extremely effective. We're going to see more phage
therapy in the future."
Laser Beams Leave Pathogens No Place to Hide
Food microbiologist Arun Bhunia trains a bright light on pathogens in food products.
With the help of then-Purdue engineer Daniel Hirleman, Bhunia created a laser sensor that can identify many kinds of disease-causing bacteria isolated from
food samples in less than 24 hours—about three times faster than conventional detection methods.
Known as BARDOT, the microwave-sized machine uses a laser to scan bacterial colonies on an agar plate. When a colony is illuminated, it produces a
black-and-white image called a scatter pattern, a unique arrangement of rings and spokes. Each type of bacterium generates a distinct scatter pattern,
serving as a fingerprint by which the researchers can distinguish the bacterium.
Recent studies by the Bhunia lab have shown that BARDOT can identify Salmonella grown from samples of contaminated foods with an accuracy of more
than 95 percent. It pinpoints virulent strains of E. coli with an accuracy of more than 90 percent and can also pick out Listeria, Vibrio and Bacillus.
BARDOT is robust enough to classify multiple bacteria with a single scan, offering an intricate portrait of an entire microbial community.
"BARDOT could be used as a screening tool to detect these key pathogens much earlier and more easily than conventional methods, which is crucial to
preventing foodborne illnesses," Bhunia says. "We are just now getting a sense of what it can do."