Some viruses only infect bacterial cells; they are known as bacteriophages (or phages), and they have real potential to defeat antibiotic-resistant superbugs. There are even cases in which very serious bacterial infections have been treated successfully with bacteriophages, and some countries are establishing phage banks. But if scientists and clinicians are going to apply bacteriophages more routinely, we have to fully understand how they work. Researchers are learning more about them. It was once thought that bacteriophages were generally specific to one type of bacterial cell. A new study has shown, however, that one bacterial cell is able to host a variety of bacteriophages. The findings have been reported in Science.
In this work, researchers determined that several phage species were able to stably coexist in a single, uniform strain of Escherichia coli. Although the bacteriophages were living in a competitive state, some phages preferred bacterial cells that grew more quickly, or more slowly, within a population of cells. Each bacteriophage, or phage, was able to localize to a niche within these genetically identical hosts to find a place to live among the rest.
When nutrients become scarce, some bacterial cells will slow their growth, preserving the few resources they have access to. In this study, two phage species called N or S were able to coexist, but N preferred faster growing bacterial cells while S infected cells that grew more slowly.
Phage therapies aim to overcome a problem with antibiotics, in which most bacterial cells are killed, but there are a few pathogenic bacterial cells that remain. These cells can often become resistant to drugs, and persist to cause another infection.
"Knowing how more than one kind of phage can survive over time on a single bacterium could help in designing next-generation phage cocktails," said first study author Nora Pyenson, PhD, a postdoctoral researcher in the lab of study co-author Jonas Schluter, PhD at NYU Langone Health. "For example, each phage species might attack the bacterium in a different part of its lifecycle, enabling the whole population to be killed before resistance to the treatment evolves."
There are not any phages that are typically used to treat bacterial infections, which may be because one phage was not sufficient to destroy the targeted bacteria or because a bacterium evolved resistance, just like bacterial cells can do with antibiotics, noted Pyenson.
Although we think of viruses in terms of human infection, these microbes have a range of habitats, and can also coexist with other viruses. This work has highlighted the diversity that can be found even among the most basic parts of biology, added Pyenson.
Sources: NYU Langone Health, Science
