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  • Alex Cloherty

Viruses, viruses everywhere! Part III

,The latest Microbial Monday has turned into a Microbial Midweek, because there is so much interesting research out there about this week's highlighted virus that it was tough to stop reading and start writing. This week, we're checking out the bacteriophage!

A bacteriophage is a virus that specifically infects bacteria. In other Microbial Monday editions, we have discussed some differences between the cells of prokaryotes like bacteria and the cells of humans and other eukaryotes. As cells go, the differences are enormous. Ultimately, this means that viruses that infect bacteria absolutely cannot infect eukaryotes. They run into the same problem that you would if you tried to enter the house of somebody across the world using your own keys: the 'keys' that bacteriophages use to enter bacterial cells simply do not match the 'locks' of eukaryotes.

One of the coolest things about bacteriophages is, in fact, the 'keys' that they use. Bacteriophages look totally out of this world:

The funny feet on the bacteriophage hold its 'keys': they attach to receptors on the surface of bacterial cells, grabbing hold of the prokaryotic victim. The bacteriophage's DNA, which is normally housed in the head of the virus, is then shot out through the stem beneath it and into the bacterial cell. Once the viral DNA is in the bacterium, a hostile takeover occurs within the bacterial cell. The viral DNA encodes everything needed to hijack the bacterium's intracellular (inside the cell) machinery, and make more baby viruses. Eventually, the produced baby viruses will escape and go on to target more bacteria in the same way.

Bacteriophages were first discovered in the age before penicillin, the first antibiotic ever discovered. In the time before antibiotics, it was relatively normal for people to die from now-treatable bacterial infections. Because of this, bacteriophages looked like a miracle: scientists wondered, could bacteriophages be used to target the bugs which infect and kill humans? Experiments using bacteriophages to treat bacterial infections did indeed start, but it wasn't long afterwards that British scientist Alexander Fleming discovered a fungus that was able to effectively kill a range of bacteria: Penicillium mould, which you probably know as penicillin. This fungus effectively beat out bacteriophages in medical history books… Until now.

In past editions of Microbial Mondays, we've also discussed the problem of antibiotic resistance. The United Nations General Assembly has called antibiotic resistance "the greatest and most urgent global risk", and it is already impacting people today. About 700,000 people each year die from bacterial infections that we used to be able to treat. If nothing changes, it's predicted that 10 million people will die each year from infections with resistant bacteria. But don't despair quite yet: scientists in not-so-shining armour are coming to the rescue.

Today, scientists are working on treating pathogenic (disease-causing) bacteria with specific bacteriophages! Besides the fact that antibiotics are failing, bacteriophages also have some potential benefits over antibiotics. Because of the very precise keys on the feet of bacteriophages, the viruses target only certain types of bacteria. This means that unlike with antibiotics, which often destroy a variety of bacteria in your system, it could be possible to knock out only the 'bad' bacteria with bacteriophages, leaving the 'good' bacteria happily growing.

Excitingly, trials are already ongoing to research the ability of "phage cocktails", which are mixtures of several different bacteriophages, to cure a variety of pathogenic bacteria. The results look promising not only in animals, which is important for the agricultural industry for example, but in humans too. For instance, scientific institutes based in Wroclaw, Poland, a historical hub for medical bacteriophage research, have shown that humans can also be successfully treated for bacterial infections using phage cocktails.

However, all this is just the start of a new era in medical microbiology. A lot of research still needs to be done before bacteriophages could be used as routinely as antibiotics are. In the meantime, it's still very important to use antibiotics carefully and sparingly, so that our existing antibacterial defences last long enough for us to build up our next, potentially viral, fortifications.

Until next week, enjoy some phage-less cocktails!

- Alex

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