Are Viruses Alive?

It has long been a mystery whether viruses could be classified as living organisms. Unlike bacteria and eukaryotic organism, they are unable to sustain an independent life and they always require resources of a host in order to reproduce. On the other hand, viruses and other living organisms have many mutual properties, including multiplication based on genetic material, mutations, and evolution. Scientists’ opinions are still controversial, but here are some evidences that support both hypotheses.

Are Viruses Alive

 

What Defines a Living Organism?

Seventy years ago, Schrödinger asked this question and it has not yet been fully answered. After the discovery of DNA by Watson and Crick, it was shortly considered an essential component of life. Then philosophers interfered with this presumption and introduced the possibility of existence of extraterrestrial life forms which might not require DNA but are also alive. During the past decades, viruses were considered side products of living organisms. Namely, the predominant opinion was that some escaped or lost genes from living organisms gathered together and formed viral units.

With the development of modern techniques of genetics and molecular biology, these opinions are starting to change. Recent studies have shown that viruses have played an important role in the early development of life on earth.

Worldwide Distribution of Numerous Viral Particles

Recent studies have shown that viruses are the most common biological structures on earth. Examinations of water using methods of molecular biology, it was shown that in oceans, there are ten times more viruses than bacteria. This high abundance of viruses is logical, as one viral particle infects one cell and use it to produce a large number of new viral particles which are then released and ready to attack new cells. Not to mention for how long the viruses how long the viruses have been present on earth, which gave them enough time to evolve so they can infect almost all the living cells, from bacteria to highly evolved human cells.

The Cause of Confusion

Clearly, viruses live, reproduce, evolve, and die like any other living organisms. The classification problem emerged from the fact that outside of the host cell, viruses are nothing more than DNA wrapped in a protein coat and completely inactive, so they seem more like a complex chemical than as a living organism. However, upon entering the host cell, viruses become very active. The problem is that they dissemble into parts which all conduct their own business in order to form new viral particles that can be released from the infected cell. Unlike other parasites, they do not perform activities as units, but as a set of separate compounds precisely programmed to assemble new viral particles.

With all those pros and cons stated during the decades of research, we can conclude that the question of viral nature remains more of a philosophical than practical question. Future studies in the field of molecular biology and even astrobiology will teach us how to approach this question.

References

Patrick Forterre . (2010). Defining Life: The Virus Viewpoint. Orig Life Evol Biosph. 40(2): 151–160.

Pennazio S. (2011). Viruses: are they living entities? Theor Biol Forum. 104(1):45-56.

Viruses, virophages, and their living nature. (2010). Viruses, virophages, and their living nature. Acta Virol. 54(2):85-90.

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