What is a bacteriophage and how do they work?

Bacteriophages are bacterial viruses, which only infect and replicate within bacteria. Their name, translated from Greek, means “Bacteria-eater”, due to their ability to infect and kill bacteria.

It is estimated that there are more bacteriophages on earth than all other organisms combined. Bacteriophages work by selectively binding to the surface of their chosen prey, hijacking their host to produce more viruses, and finally bursting the cell open to release newly assembled viruses into the environment. Crucially, Bacteriophages, or “phages” for short, do not infect human cells. This means that their ability to selectively target and kill bacteria can be used to our advantage.

What do bacteriophages look like?

All Bacteriophages are tiny. They are even smaller than bacteria. This means its only possible to see bacteriophages using an electron microscope.

The most isolated and studied bacteriophages are referred to as “tailed phages”. The structure of a tailed phage consists of an icosahedral (20 sided) head which packages and protects the genetic material (DNA or RNA) of the phage. The head, also known as a capsid, is attached to a tail with tail fibres which are used to bind to their prey to start the infection process. The interaction between a phage tail fibre and bacteria is very specific, so certain phages can only infect specific bacteria and their close relatives.

How can we use bacteriophages?

Many researchers and doctors use the bacteria-killing ability of phages in plant health, animal health and food production. Bacteriophages can help fight bacterial infections which are resistant to antibiotic treatments and have applications in the food production industry to target bacteria which cause food-borne infection or food spoilage.

Bacteriophages in plant health

Many bacterial diseases affect crop plants which cause significant crop losses and reduction in yield. Key crop plants such as wheat, barley, maize and potato can all be infected by common bacterial pathogens which can cause partial or complete crop losses. Large scale crop loss can cause severe economic losses and disrupt global food supplies.

Bacteriophages can help to reduce crop losses and keep up with the increasing global food demands. For example, bacteriophages have been effective in preventing the plant disease soft rot in potatoes, caused by the bacteria Dickeya solani. This use in potatoes reduced crop losses to disease and therefore increased yield. Similar studies have applied phages to tomato, grape and lettuce and had success in reducing disease.

Bacteriophages in animal health

Inappropriate use of antibiotics in farming has contributed to the rise of infections that are difficult to treat, caused by multi drug resistant (MDR) bacteria. Bacteriophages are a promising alternative to antibiotics and have potential to be key players in improving health of livestock.

The ability of phages to kill harmful bacteria can be used by vets to treat infections or prevent animals becoming infected. For example, bacteriophages can be used against pathogens such as Salmonella and E.coli in animals to prevent transmission into food meat products and improve safety for consumers.

In addition to livestock, antibiotics are common place in the clinic for pets.  The most common antimicrobials used to treat pets are also used to treat human infections. Although not linked to the human food chain, some bacteria are able to transmit between pets, such as dogs and cats, into humans. Using bacteriophages to treat infections pets, could help mitigate the overuse of antibiotics and reduce the emergence of antibiotic resistance whilst still protecting pets and their owners from infection.

Bacteriophages in food production

We need to find new natural biocontrol methods that prevent disease causing microbes growing on food, so that our foods are safe for human consumption.

It is important that methods to prevent harmful microbial contamination do not affect the taste, texture or appearance of foods. Phages show promise for killing certain disease-causing microbes in food whilst not affecting sensory characteristics of food products or the beneficial microbes that are present. The promising potential of bacteriophages the development of many commercially available bacteriophage combinations, often called bacteriophage cocktails, which can selectively kill key bacteria such as Listeria, Salmonella and E.coli in food production settings.

How do we study bacteriophages at the Quadram Institute?

At the Quadram Institute we are investigating many aspects of bacteriophage biology.

We aim to better understand how bacteriophages interact with their hosts and how bacteria can defend themselves against phage infection. We study bacteriophages both in the lab and using computational based methods.

We’re working to better understand how communities of different bacteriophages in the gut microbiome interact with key bacterial species and how this can contribute to health and disease.

Through collaborations with food producers, we can formulate better combinations of bacteriophages which have improved efficacy to improve plant and animal health and keep our food safe to eat.