Definition of a pathogen
Biology discussion, revision, exam and homework help.
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Definition of a pathogenOk, the definition of a pathogen goes:
A micro-organism with a potential of causing disease, including; viruses, bacteria and fungi.
This is the definition in my text book, online and in the oxford dictionary of science. However a virus is not defined as living is it? Therefore it is not an organism, thus can't be called a micro-organism, hence this definition is wrong?????
Please can someone shed some light on this issue and help make my understandings clear in my mind!
any help will be appreciated
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Re: Definition of a pathogenViruses are living things...(Original post by tdx)
Ok, the definition of a pathogen goes:
A micro-organism with a potential of causing disease, including; viruses, bacteria and fungi.
This is the definition in my text book, online and in the oxford dictionary of science. However a virus is not defined as living is it? Therefore it is not an organism, thus can't be called a micro-organism, hence this definition is wrong?????
Please can someone shed some light on this issue and help make my understandings clear in my mind!
any help will be appreciated
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Re: Definition of a pathogenviruses have living characteristics but they are not wholly living themselves? ... they do not reproduce themselves or carry out there own metabolic reactions? ... correct me if I'm wrong(Original post by ummm)
Viruses are living things...
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Re: Definition of a pathogenIt's a controversial issue, they haven't really decided I don't think.. but I would side with OP as viruses are just proteins/carbohydrates/lipids etc. that don't do anything until they enter a living cell. They don't even look like living cells.
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Re: Definition of a pathogenHmmm, sorry, I think I was wrong! I don't think they're considered to be living organisms after doing some quick research...(Original post by tdx)
viruses have living characteristics but they are not wholly living themselves? ... they do not reproduce themselves or carry out there own metabolic reactions? ... correct me if I'm wrong
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Re: Definition of a pathogencheers(Original post by Nathan2995)
It's a controversial issue, they haven't really decided I don't think.. but I would side with OP as viruses are just proteins/carbohydrates/lipids etc. that don't do anything until they enter a living cell. They don't even look like living cells. but then that makes the 'official' definition either wrong or open to much controversial debate :/
haha, don't worry, as the above guy said, whether or not viruses are defined as living is yet to be decided :')(Original post by ummm)
Hmmm, sorry, I think I was wrong! I don't think they're considered to be living organisms after doing some quick research... -
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Re: Definition of a pathogenNo, they are not.(Original post by ummm)
Viruses are living things... -
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Re: Definition of a pathogenViruses are non-living so you're right. Since they do not posses a 'true nucleus' and do not posses any organelles they can't really function without a host cell.(Original post by tdx)
cheers but then that makes the 'official' definition either wrong or open to much controversial debate :/
haha, don't worry, as the above guy said, whether or not viruses are defined as living is yet to be decided :') -
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Re: Definition of a pathogenYes, It's a hotly debated topic... It sounds juvenile, but M.R.S G.R.E.N are the components that traditionally define life. However, viruses are simply nucleic acid structures or code (whether s.s., d.s, RNA, or DNA) for functions but require a host cell to be transcribed (whether incorporated into the host genome or not). The main issue with this debate, in my opinion, is that it highlights problems with our definitions of life. Viruses are equal to the 'building blocks of life', but are effectively just coding.
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Their coding just happens to code for the production of more viruses and things like a protein coat, incorporation into the host genome, budding, lysing etc.Last edited by rockshow7; 11-05-2012 at 00:12. -
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Re: Definition of a pathogenThere is no single definition of pathogen, my textbooks use a range of terms from "causative agents of disease" to "disease-producing microbes such as bacteria and viruses".(Original post by tdx)
Ok, the definition of a pathogen goes:
A micro-organism with a potential of causing disease, including; viruses, bacteria and fungi.
This is the definition in my text book, online and in the oxford dictionary of science. However a virus is not defined as living is it? Therefore it is not an organism, thus can't be called a micro-organism, hence this definition is wrong?????
Please can someone shed some light on this issue and help make my understandings clear in my mind!
any help will be appreciated
I can understand how you might think that virus is not defined as living. If you have been taught that the cell is the smallest unit capable of carrying out life functions, the idea of non-cellular life may seem like a non-starter. In fact it's not quite as simple as that.
The debate as to whether viruses are living entities has been raging almost since the first virus was identified, with good arguments on both sides. Indeed, as more viruses are discovered they appear to have more and more life-like characteristics. Virologist Vincent Racaniello concluded, "it’s somewhat of a futile argument because everyone has their own view; perhaps our time is better spent studying viruses than discussing whether or not they are alive." Quibbling over definitions makes for a great philosophy debate but contributes little to scientific understanding of the universe.
Whilst any good textbook should include a discussion about the phylogenetic scientific classification of viruses, I think it is understandable that outside of that discussion viruses are assumed to be micro-organisms, if only for convenience' sake. -
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Re: Definition of a pathogenthey are considered pathogens.
Pathogens are basically anything that cause disease. *Foreign body stuff only btw.. autoimmune are not pathogens. (though cause of the autoimmune could be pathogenic,.. we still don't really understand causes of autoimmune diiseases.Last edited by Ihategcse; 11-05-2012 at 19:37. -
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Re: Definition of a pathogenYep. Viruses are pathogens regardless. The degree of pathogenicity is termed 'virulence'. Again a pathogen is an infectious agent, so from outside the body.(Original post by Ihategcse)
they are considered pathogens.
Pathogens are basically anything that cause disease. *Foreign body stuff only btw.. autoimmune are not pathogens. (though cause of the autoimmune could be pathogenic,.. we still don't really understand causes of autoimmune diiseases.
Also we do have fairly good theories as to the origin of autoimmune diseases. A failure to select B-cells that are self-reactive in the bone marrow for example. -
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Re: Definition of a pathogenThis is simply a case where the world defies our best attempts to classify it. Biology refuses to be sorted into neat packages.
Viruses are not alive - you refer to them as virus particles rather than cells, and cells are the basic unit of life. However, they are a pathogen as they cause diseases (pretty obvious). -
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Re: Definition of a pathogen[QUOTE=tdx;37451804]"Ok, the definition of a pathogen goes: A micro-organism with a potential of causing disease, including; viruses, bacteria and fungi."
Should you address multiple dictionaries you will find various definitions of a "pathogen". At one extreme will be something like "a disease causing micro-organism" and at the other "any agent that causes disease" with shades in between.
If a pathogen is - without question - an organism, then the term "pathogenic organism" becomes problematic. It translates into a "pathogenic pathogen" which is akin to a "cardiac heart", a "renal kidney" or a "pulmonary lung". Whoops! Something is wrong.
I suggest the problem has come from the sloppy tendency to abbreviate "pathogenic organism" to "pathogen" and slowly escalate this into a correct and legitimate synonym for the former. Without question, a pathogenic organism is a pathogen (provided it HAS damaged its host) but the corollary, a pathogen is, without question, a pathogenic organism is clearly corrupt. There are a multitude of abiotic pathogens. My favourite example is asbestos. This generic nature of a "pathogen" is in keeping and logically consistent with the way we talk of the pathogenesis of disease, pathology in general and the pathogenic mechanisms of disease.
The moment we restrict, by the mass action of common usage, the meaning of a pathogen to just living biotic organisms we drive ourselves into incongruity.
I have a published paper on this theme in the Scandinavian Journal of Immunology (Aug 2008); but this seems to have been largely ignored. -
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Re: Definition of a pathogenBecause it could be a bacteria or a fungus. Or even a prion.(Original post by JamalAhmed)
Why can't we say a pathogen is a "disease-causing virus"? -
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Re: Definition of a pathogenWe can infer that a disease causing virus is a pathogen (ie, it has behaved in a pathogenic manner) but we can't infer that a pathogen is a disease causing virus; a pathogen could be all sorts of other agents. It would be like saying an animal is a dog. Animal is generic, dog is specific. Pathogen is generic, virus is specific. "A dog IS an animal" makes sense; "an animal IS a dog" is nonsense. And the same applies to pathogen. When we talk of a pathogen we should only be talking about the agent's (generic) disease causing behaviour, not its specific classification (ie, a specific reproducing agent or a specific inanimate agent).(Original post by JamalAhmed)
Why can't we say a pathogen is a "disease-causing virus"?
