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If viruses could think, they would surely regard humans as upstarts — late entrants to a crowded biosphere; blowhards, who believe they’re far more important than they are and certainly far more important than any other organism.
If they had feelings, viruses would have many reasons to look down on humans, not least because these tiny strands of DNA or RNA wrapped in a protein are by far the most numerous biological entities on Earth.
They are numbered in millions, although “numbered” is probably the wrong word since nobody knows the number. Scientists have identified and described in detail only about 5,000 and have no real idea what most of the others might be up to.
Viruses get bad press, which is understandable since many cause a wide variety of illnesses. They’re parasitic and replicate by invading the cells of a host by using intriguing means. Once inside, they introduce their DNA or RNA strands so that when the cell replicates it also reproduces the virus. This is usually detrimental to the host organism, but not always.
Many viruses are beneficial to animals and plants. Professor Marilyn Roossinck of Pennsylvania State University, an expert in plant pathology and environmental microbiology is a big fan of viruses. She says “viruses are beyond a doubt the coolest things I have ever encountered.”
What makes her such a fan is their efficiency, she says, more specifically the fact that viruses “do truly amazing things with very little genetic information.” You might say that they are microscopic judo black belt champions: they defeat their host by harnessing the host’s own resources.
Not all viruses are detrimental to their host. Indeed some could be described as minuscule Florence Nightingales — healers, without which hosts would not survive. This is exemplified by a type of tropical panicgrass that grows around the geysers of Yellowstone National Park where the soil temperatures reach 122 degrees Fahrenheit.
Thanks to a virus and a fungus, the plant thrives in this soil because of a strange symbiotic relationship: The fungus colonizes the plant without harming it, and the virus infects the fungus without harming either the plant or the fungus. This strange co-operation creates a biological balance that enables the grass to thrive in this extremely hot soil.
Scientists have experimented with the same virus-infected fungus and other plants. All the plants tested were able to survive very high soil temperatures, sometimes as high as 149 degrees, because of the three-way symbiosis.
Viruses don’t just help some plants thrive in high-temperature soil. They enable others to thrive in drought conditions and yet more in very cold temperatures. Scientists are currently developing a wide variety of plants that have viral-acquired tolerances enabling them to grow in otherwise inhospitable locations. They hope this will make it possible to grow food crops where nothing previously grew, thus turning barren areas into arable land.
Viruses are beneficial not just to plants. Scientists are also harnessing viruses to fight human diseases, including some types of cancer. The idea that it might be possible to use viruses to treat human disease arose by chance a few decades ago.
Doctors treating cancer patients noticed that the disease sometimes regressed in patients who were also infected by a particular virus. Many years of investigations followed leading to the discovery that some viruses can kill cancer cells, yet not harm healthy ones. This led to multiple trials in different countries, some of which are ongoing.
The broad aim is to test the efficacy of the most promising viruses in the treatment of a variety of cancers, including those of the breast, lung, prostate, bladder, and pancreas. Such viruses are called oncolytic. In 2015, the U.S. Food and Drug Administration and its EU equivalent, the European Medicines Agency, approved an oncolytic virus therapy to treat melanoma, the most serious type of skin cancer.
Viruses are a bit like people: some are good and some are bad. They’ve been around much longer than humans and may well be here after we’ve gone. It seems that every so often they like to remind us of this fact. If the coronavirus teaches us anything, it’s that we are not, after all, masters of the universe, much less of planet Earth, although we often think we are.