When Viruses Help

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We’ve all heard about helpful gut bacteria that play an active role in human and animal digestion. It is the perfect example of symbiosis, or long-term coexistence of biological organisms belonging to different species. But the impact of bacteria living in the intestines extends well beyond the digestive tract. It turns out that the gut microbiome is also a “psychobiome”, capable of influencing the way we feel, think and act. Recently, a group of scientists, primarily from Harvard Medical School and Northeastern University in Boston, have discovered that Bacteroides fragilis, a type of bacteria normally inhabiting the human colon, produces large quantities of GABA, an important brain neurotransmitter that inhibits the activity of the nervous system and produces a calming effect. In short, these bacteria make us happy.

While scientists have been aware of how beneficial some bacteria are for our organismic wellbeing, the public narrative is different with viruses. The Covid-19 pandemic has put the SARS-CoV-2 trigger virus in the spotlight. The studies of its origins have also emphasized the capacities of microorganisms to “jump” from one species to another, passing from animals to humans. What is not widely known is the fact that viruses affect all living beings – humans and animals, but also plants and even bacteria. Still, up to now, the consensus has been that their influence is either entirely pernicious or, at best, neutral. The theory of viral attenuation postulates an evolutionary dynamic from the first pole to the second, from adverse (oft-times lethal) effects to milder or softer versions that do not cause significant harm to the host. For example, some proteins from Human Endogenous Retroviruses (HERVs) can be deployed for pregnancy-related purposes, playing a crucial role in placental development.

But, given that some bacteria are useful (if not indispensable) for animal and human organisms, could the same be said about viruses? In other words, can there be such a thing as a helpful virus, one that does not inflict harm nor catches a neutral free ride on the body of the host, but facilitates the optimal functioning of the host’s physiology?

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In response to these seemingly strange questions, a group of Spanish scientists has just made a groundbreaking discovery, published in the Proceedings of the National Academy of Sciences of the United States of America. With his colleagues from the University of Valencia and Jaume I University, Rubén González has isolated the surprising beneficial effects of the turnip mosaic virus, belonging to the family of Potyviridae, on its vegetal host.

According to the study, the usually pathogenic agent accounted for a greater tolerance of drought conditions experienced by thale cress (Arabidopsis thaliana). The chances of survival of the infected plants were, on average, twenty-five percent higher than those of their non-infected counterparts. Intriguingly, the specimens infected with turnip mosaic virus have displayed various other adaptive mutations, related to the regulation of circadian clock and of phytohormones responsible for the functioning of defence and growth signalling pathways. Instead of following the classical strategy of killing its hosts, the virus enhanced the survival chances of plants subjected to adverse conditions.

González and his team of scientists interpret their findings in light of an abrupt transition from the pathogenic to the mutualistic character of interaction between turnip mosaic virus and Thale cress. In fact, the mutualistic nature of the virus was preserved in the aftermath of the initial interaction when it was used to infect the sufficiently watered plants. In other words, strains of the virus that evolved in drought conditions retained their adaptive value and helpful character when they infected plants no longer subjected to these adverse conditions. What sorts of conclusions can philosophers draw from these fascinating experiments?

An isolate of Plum pox virus from Potyviradae family

an isolate of Plum pox virus from Potyviradae family

First of all, we should problematize current political discourses that declare a “war on the virus”. Generally speaking, we should avoid projecting human political categories onto the non-human world, so as not to measure this world with the same anthropocentric yardstick. More specifically, the use of words such as war and peace focuses on the parties to the interspecies interaction, rather than the environmental context in which this interaction unfolds. As the experiments with Thale cress and turnip mosaic virus show, the key actor in the drama is neither the plant nor the virus, but environmental conditions that upend the effects of the latter on the former. What happens when these conditions and abrupt changes within them come to the fore and are identified as the main culprits and catalysts of inter-species and cross-kingdoms relations? How can we tell the story of a pandemic, while taking into account the constitutive role of the environmental context in its unfolding?

Second, and as a consequence, we should relativize the extremes of harm and beneficence in the biological domain, where evolutionary and adaptive processes unsettle the rigid definitions we tend to operate with in other spheres. What was harmful (or neutral) can become useful within the long duration of natural selection or even within a relatively short duration of a shift in an organism’s circumstances. More radically, we could come to adopt a dialectical view of the negative and positive values inherent in the same thing at the same time. Such an outlook is called speculative, as it thrives on the inner contradictions that are intolerable for a mindset accustomed to the rules of formal logic, according to which X and not-X (say, alive and not-alive) cannot hold simultaneously for one and the same object. (Let me note that the above example is not incidental: viruses may be legitimately said to be both alive and not alive.)

Third, we should approach all forms of life with an open mind, keeping our biases for or against them in check. This goal is quite hard to achieve with regard to viruses, even though, outside the discipline of biology, a viral video or message may be subject to a positive valuation, insofar as it rapidly reaches a vast global audience. In biology proper, German virologist Karin Moelling has tried to counter the bad rap of these tiny creatures in her 2016 book, Viruses: More Friends Than Foes. Calling them “the superpower of life”, Moelling draws the readers’ attention to how, for instance, viruses can be “applied against threatening multi-resistant bacteria”. The sudden change in the effects of turnip mosaic virus on Thale cress confirms Moelling’s theoretical paradigm. But it might be wise to refrain as much from attributing friendly characteristics to viruses as from ascribing adversarial qualities to them, given that these features are not inherent but often environmentally conditioned and, as such, fluctuating.

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There are, no doubt, many other conclusions to be drawn from the Spanish study. But the overarching theme it points to is that, in addition to the efforts that go into “fighting”, devising protections from, and eradicating viruses, it is crucial to think them through, to think about and, perhaps, also with them. Will a moment arrive when we are ready to think through, about, and with SARS-CoV-2, the virus responsible for Covid?


Michael Marder is Ikerbasque Research Professor of Philosophy at the University of the Basque Country. His work spans the fields of environmental philosophy and ecological thought, political theory, and phenomenology. His latest book Dump Philosophy: A Phenomenology of Devstation was published last year by Bloomsbury.


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