Are viruses living? How old are they and how did they evolve over the time since their origin? These and more questions about viruses make them some of the most mysterious subjects of scientific inquiry.
Last year, scientists claimed the revival of the largest virus – Pithovirus sibericum – in lab after discovering it in Siberian ice. While its ability to replicate itself in the cytoplasm of the host cell (in the lab experiment, an amoeba cell) instead of the nucleus added to the curiosity of scientists, the revival of the old viral entity itself revived the question: are viruses living?
The question of whether a virus is a living organism like others is mainly based on one unique property of viruses – they can be stored or preserved (by nature or human agents) almost indefinitely. Unlike other microbes, which can’t exist for long without a living host, viruses can exist for incredibly long periods of time. They just act like crystals that can get back to life after an amazingly long period of time. That is why they are considered on the borderline of living and nonliving entities.
In 2013 Discovery News published a story about research that vouched for viruses as living organisms. The study, for the first time, found that viruses can possess genes for a functional immune system, leading to the conclusion that viruses are complex enough to qualify to be ranked among living organisms.
Now, scientists claim that they have discovered more proteins among viruses that are unique to them and indicate that viruses evolved as the earliest lifeforms on this planet. Further, they believe that viruses are not as independent of existing outside other living cells as usually believed.
Does the new study counter the earlier observation of independent existence of viruses as shown in experiments on Pithovirus? Not so easily! In fact it only furthers the debate. If viruses can exist independently for thousands of years but cannot reproduce themselves on their own without a host, can they still be living? The jury is still out.
