A series of stages from protein (Prion) , Virus (one nucleic acid), Rickettsia, Chlamydia, Mycoplasma, bacteria (two nucleic acid)......different animals and plants are found in nature.

We made boundaries and gave some names to each category for our better and easy understanding of the whole subject.

So, there are always some 'in between' and some 'common characters' found in all such classification.

It is a problem in scientific study.

It is not a problem in nature.

Thanks.

Interesting classification. But prions are even worst. They manage to convince host's prions to behave their way, reproducing exponentially in the host's brain until dead. Hoping we don't have to quickly change our sense of consensus. Because Coleridge told it, v-creutzfeldt-jakob may take 40 years of incubation. The cases that happened in year 2000 were contaminated in the sixties. The mad cow disease begun in the eighties in England, with massive alimentation of the bovines with meat-and-bones flours poorly cooked. 40 years later, it's now. I hope to be wrong.

A series of stages from protein (Prion) , Virus (one nucleic acid), Rickettsia, Chlamydia, Mycoplasma, bacteria (two nucleic acid)......different animals and plants are found in nature.

We made boundaries and gave some names to each category for our better and easy understanding of the whole subject.

So, there are always some 'in between' and some 'common characters' found in all such classification.

It is a problem in scientific study.

It is not a problem in nature.

Thanks.

There are not yet firm definitions of 'living' and 'non-living.' Even words like 'species' and 'family' are used pretty loosely in taxonomy when it comes to viruses, bacteria, mammals, etc. These labels are constantly in flux, so someone saying "virology is a branch of biology" is a pretty lame argument (they're just words we made up ourselves!). We use these terms as descriptive ways to categorize things (makes it easier to study), but as you're well aware it becomes difficult when some things seem to have properties befitting multiple labels. In that regard, the idea of things like viruses being 'life' or 'non-life' is more of a fun philosophical discussion rather than a hard scientific consensus. Both sides are debatable and there is no 'right' answer yet, so declaring oneself correct wouldn't be proper.

Personally, I would lean towards them being non-life myself as none of the things you listed can independently synthesize their own proteins or their own metabolism (pretty 'non'living' if you ask me). But again, it's semantics and whether viruses are categorized as life or not doesn't physically change anything about them or make them less interesting.

Hello,

it is very interesting subject for academic discussion.

I believe that many scientists would like to share here their opinion about the characteristic features as well as the systematic position of viruses, viroids and prions.

However, there is even more interesting issue associated with your question - what is life?

Nevertheless, I share and agree with the opinions of Fred Romano and Shibabrata Pattanayak.

Additionally, I can recommend an interesting paper on that issue, the paper from (a little bit) phylosophical point of view entitled 'The not so universal tree of life or the place of viruses in the living world' by Harald Brüssow (DOI: 10.1098/rstb.2009.0036).

Best wishes

Piotr

Since the paper was rejected, partly based on living and non-living, I had to ask the question. To work around this, I assume most virologists use the term "infectious agent" for viruses and viroids (not to mention prions as that is another ballgame) instead of "organism" or "microorganism"? Is this accurate? The same reviewer also had a problem with the term "agent" or "infectious agent". Thank you everyone for your comments.

@ Johannes Petrus Louw

I'm in the field of virology myself and can say that the terms such as 'microorganism,' 'pathogen,' 'viral life cycle,' 'replication cycle,' etc. are used very loosely and inconsistently from peer-to-peer. Again, this stems from no firm definitions for some of these concepts. The words are typically used in a nebulous or catch-all manner and really come from the author/speaker's personal preference. For a reviewer to categorically reject something (rather than ask or suggest a correction) based on specific terminology that they prefer seems overly picky.

During a conference performed last month at the Phages in Bordeaux symposium, Patrick Forterre (https://www.researchgate.net/profile/Patrick_Forterre2) made us aware of his theory that viruses are living things. Living beings would be separated between ribosomes producing organisms and capsid producing organisms. And he used consequently capsids to draw a phylogenetic tree of viruses.

One of his arguments that viruses were living things was that the virion phase should not be considered as the only viral entity but that the prophage and the infected cell (the virocell to be opposed to the ribocell) were phases of the viral organism.

Then came a questioning about what made an entity a living creature that in my opinion is more about philosophy than about biology.

In any case, thank you for launching this kind of question: Researchgate is not only made for technical questions.

EDIT :

I would like to add that the fact that "Mother Nature" does not bother with such boundaries does not justify the need to avoid this question. These kind of issues that are a priori purely philosophical or at least academic are also socially necessary: knowing whether an entity can be described as living or not (or a product qualified as organic or not) has an impact in terms of standards, applications and ultimately an impact on people's lives.

Viruses must be considered as living things since they can replicate, although inside cell. Non living things have no power to replicate.

Dear Dr.Singh,

Prions are just deformed structure of a normal protein of cell.

These proteins can also replicate by using host system and are infective (Mad cow disease of man).

So, why they should be considered as 'non living?'

Because outside an host, they can't reproduce

Viruses, viroids and prions cannot be truly regarded as non-living because of their ability to reproduce.

Viruses depend on other living organisms to survive. They have genetic material such as DNA or RNA and can replicate thanks to enzymes encoded by the virus, as such they can be considered as living being. The situation by prions is very different they are abnormal forms of a normal harmless protein found in the brain and as such they cannot be considered as living beings (these proteins interact with other normal proteins in a form of chain reactions)

Viruses, prions and viroids are non-living organisms that require a living cellular host in order to reproduce. They cannot do it on their own. These parasites may be just a string of RNA, as in a viroid, or a length of DNA enclosed in a protein shell, as in a virus.

https://www.chegg.com/.../viruses-prions-viroids-non-living-organisms-require-living-ce.

I didn't see your discussion on this topic until after I put my own discussion on the website. I will gladly add my new discussion to you current one here, Thank you.

Virus: Definition of Life? (and Prions)?New discussion

• Started 59 minutes ago

I know that by the current definition viruses are not considered to be alive. But as far as intelligence, the COVID-19 virus (SARS-Cov-2) is currently outsmarting 8 billion humans. It has long passed bats, pangolins, chickens and pigs. This virus is stated to be an intracellular parasite, but allegedly not alive, because it is only able to reproduce within a host cell. Does the virus not meet the definition of life, when it takes over the host cell and all of its mechanisms, to do the viruses' own bidding; to reproduce, becoming a parasitic-host organism? Admittedly, the host cell often dies, but this is not always so, as some virus cell organisms survive with the virus as a true parasite (cf Epstein-Barr Virus in dorsal neurons of humans)(vaccinia virus in injection granulomas)(varicella virus in dorsal root ganglia), etc.Perhaps, it is time to consider viruses as potentially an aberrant parasitic, but a true lifeform.(Then, we need to talk about prions, these and their diseases are somewhat similar, and I would have a similar argument for them) Thank you for your support, and stay safe. Gary Ordog, MD June13, 2020.