76: Bacteriophage, the virus we like

What would you say the most numerous creatures on the planet are? Perhaps flies, or ants, or probably more likely bacteria? Actually, it’s the sworn enemy of bacteria- the bacteriophage. There are an estimated 1031 bacteriophages on the planet, which is more than the number of every other living organism combined. On top of that, this creature seems truly deadly, destroying half of the world’s bacteria every 48hrs. However, this isn’t a doom and gloom piece because oddly enough, the bacteriophage is actually our friend. Here we will be looking at what it is, how it can help keep our meals tasty, and how it might be a vital safety net to our health systems in the future.

Diagram of a bacteriophage, which looks much the same as other viruses (Picture: Wikimedia Commons/CC BY-SA 4.0)

What is a bacteriophage?

As we have learned this year, viruses can have a big impact on people. However, we’re not the only ones dealing with their potentially deadly attack. A bacteriophage is a virus that infects bacteria. They tend to be very specific, with each one targeting very few or even just one type of bacteria. When the bacteriophage finds a suitable host, it attaches onto its surface and injects genetic material into the bacteria. This then forces the bacteria to rapidly make thousands of copies of the bacteriophage. Eventually these copies explode out, destroying the host and spreading onwards, an event known as lysis. After this, the whole process begins again.

It is thought that up to 70% of the bacteria in the world’s oceans, like bacterioplankton or certain types of algae, are infected with bacteriophages. This means they die in huge numbers, but it also means that when lysis happens, the carbon that was previously stored in them is released, now available to be used by other creatures in the ocean. This process is an essential part of the carbon cycle, which in turn is pretty much essential for life, as plants and animals need access to carbon to be able to grow and develop.

Lots of bacteriophages on the right hand side at work attacking the large bacteria on the left (Picture: Wikimedia Commons/CC BY-SA 3.0)

Food and agriculture

Despite their terrifying sounding life cycle, bacteriophages really can actually do a lot of good, even beyond the carbon cycle. As mentioned, bacteriophages are really specific to the type of bacteria they infect, and this can include bacteria that are problematic to humans, such as Listeria, Salmonella and various harmful forms of E.Coli, which when consumed from food can cause illness and even death. It has been suggested that these pathogens are becoming increasingly common in our environment and food systems, as industrial forms of animal agriculture lead to huge cesspits of animal faeces being collected, creating the perfect breeding ground for harmful bacteria. They can then spread to animals, contaminate soil and water, and eventually contaminate plants we eat too, making them a growing danger to humans.

This is where the bacteriophages come in handy. As they often target one specific kind of bacteria, e.g. listeria, but don’t target other good bacteria found in foods and our bodies, they can be used to remove the bad bacteria, making food safe. This is quite a new technology, but it is already gaining a lot of traction with new bacteriophage companies such as Listex getting full United States Food and Drug Administration (FDA) approval in the last decade. It is seen by many to be a better alternative to cleaning methods like irradiation and chlorine washing, which not only kill good bacteria but also taste. Bacteriophage treatments are also a favoured alternative to those concerned about the genetic modification of crops to deal with bad bacteria. These bacteriophage sprays, which are used to apply the bacteriophages to potentially infected foods, have also been seen to slow down the bacteria which spoil food, meaning these foods can last longer without preservatives.

We often think of food poisoning coming from things like uncooked meat. However, bacteria like listeria, if it makes it’s way into the soil or water used to irrigate crops, can infect fresh vegetables like this romaine lettuce too (Picture: Wikimedia Commons/CC BY-SA 3.0)

Health and antibiotics

Bacteriophages then can play an important role in preventing people, and animals, getting sick, but as it turns out, they can also be useful as a treatment once bacteria has already entered the body. Using bacteriophages in medicine has been common in former Soviet countries for decades, especially in Georgia, starting out in the 1920s and 30s. If you are from much of the rest of the world however, you might wonder why you’ve never heard of these bacteriophage therapies. That’s because especially in the west, antibiotics have been more readily available and favoured, and much of the research on bacteriophages was published in Russian language forums, meaning the knowledge didn’t end up travelling that far. Interest is growing in using bacteriophage therapies however, with the approval of this technique for treating things like lung infections, burn infections and ear infections.

Even more exciting, bacteriophages could be a part of the solution to antibiotic resistance. Bacteria can become resistant to antibiotics if antibiotic treatments are not caried out to completion (e.g. stopping taking antibiotics when you feel better rather than when the course is finished), or through overuse of antibiotics when they are not required, among other reasons. This is incredibly dangerous, as if some bacteria become resistant to antibiotics, their infections may become incurable. This means that simple standard procedures like getting your tonsils removed, or having a caesarean section, could be deadly. Bacteriophages are now being studied and trialled as a way to overcome this antibiotic resistance, by targeting and destroying the resistant strains before they have time to multiply. There have already been multiple cases of people on the verge of death, resistant to the effects of antibiotics, who with a treatment of bacteriophages have made a full recovery. Medical hope comes in the form of the bacteriophage!

Overuse of antibiotics, both in humans and livestock, poses a big risk for antibiotic resistant bacteria to develop. Use of bacteriophages may help to reduce the likelihood of antibiotic resistant bacteria developing however.

Whilst bacteriophage research is still quite young as a field, knowledge of these viruses has been around longer than you may expect. Certain rivers such as the Ganges have long been believed to have healing powers. Interestingly, studies into these rivers found than, whilst on the one hand they contain effluent and waste runoff from surrounding towns and cities, this also means that bacteriophage populations thrive there, and when ingested by people may help them to overcome some infections. From historical sacred river cure, to affordable Soviet medicine, to keeping our foods safe and our carbon cycling, bacteriophages are some of the unsung heros of our health and our planet.

For more info:

An excellent podcast by gastropod on the bacteriophage, focusing mostly on agricultural applications, can be found here

New Yorker article on the more medical side of bacteriophages available here

Music: kongano.com

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