There are good and bad bacteria, but are there any good viruses? And what would happen if all viruses disappeared? (cont.)
Mike Follows
Sutton Coldfield, West Midlands, UK
If people had been aware of the existence of bacteria and their role in causing the Black Death in the 14th century, as well as the subsequent cholera pandemics, convincing them that bacteria could be both “good” and “bad” would have been a significant challenge. Similarly, in the wake of the covid-19 pandemic, emphasising the benefits of “good” viruses might seem equally difficult. However, viruses play a positive role in medicine, ecology and biotechnology, with several important applications.
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Phage therapy, which uses bacteriophages – viruses that infect and kill bacteria – has emerged as a promising treatment for bacterial infections, particularly those resistant to antibiotics. Bacteriophages can be highly specific in targeting pathogenic bacteria, leaving beneficial bacteria unharmed, which contrasts with broad-spectrum antibiotics that kill beneficial and harmful bacteria indiscriminately.
In gene therapy, researchers exploit certain viruses to deliver healthy genes into human cells to correct gene variants associated with genetic disorders such as cystic fibrosis. Furthermore, oncolytic viruses – which are engineered to target and destroy cancer cells while sparing healthy tissue – are being explored as a novel cancer treatment.
Viruses also play a crucial role in ecological systems, particularly in regulating microbial populations. By infecting and killing certain bacteria, viruses prevent any single species from dominating, and so help maintain microbial biodiversity. This also happens in the human microbiome, where viruses help control the levels of harmful bacteria, potentially reducing the risk of infections and inflammation.
In agriculture, phage therapy has been employed as a control method for plant pathogens, providing an alternative to chemical pesticides. Additionally, bacteriophages have potential in cleaning up contaminant spills, targeting bacteria that otherwise exacerbate pollution incidents.
Viruses also drive evolutionary processes through horizontal gene transfer, a mechanism by which genetic material is exchanged between organisms, leading to increased genetic diversity. This has contributed to the evolution of many different species, including humans.
If viruses were to disappear, illnesses such as influenza and covid-19 would also vanish. The loss of viruses, however, would also mean the loss of their many beneficial roles.
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