Those who have seen me in the past few days will have realised that my body is currently playing unwilling host to a menagerie of viral and bacterial invaders, putting their feet on the couches, leaving the toilet seat up and generally making a mess of my finely-tuned metabolism.
Anyone who has been similarly afflicted will be familiar with the uncanny correlations between the light/dark transitions in the external environment and the behaviour of the piratical microbes (and viruses) within you. For instance, an increase in your internal body temperature and rate of coughing appears to be brought on by dusk.
I was wondering whether these effects are actually due to the invaders themselves or some form of perverse response mechanism on the part of my body, which inevitably leads us to ask if viruses are living `beings' or `creatures'.
A quick Google yields a number of interesting posts made by people from all walks: specialists, laypeople and people who just seemed to be there to laugh or jeer at everyone else (especially common on the less formal pages).
The general consensus appears to be that viruses are not alive, in the sense that we all heard in first year biology (viruses are obligatory intracellular parasites that cannot reproduce or metabolise when separated from a host). The basic argument is that since viruses cannot undertake the processes we normally associate with an `unambiguously alive' cell, they cannot be alive. Articles which expand on this are from Microbial Life Teaching Resources, Scientific American and Virology Down Under (here at UQ).
The most interesting page I found was relating to a virophage: a virus which infects other viruses! If a virus can infect another and produce a noticeable effect, does that not imply that they both themselves are alive? Or is this just an exceedingly complex chemical reaction? Am I?
A second interesting page looked at the possibility of the eukaryotic nucleus arising from a virus rather than a bacterium. Does anyone know of a virus that has a lipid membrane instead of a protein coat?
Unfortunately, actually searching the scientific reason behind why you feel worse at night just turns up a lot of articles on stigma in post-treatment patients and anxiety in adolescents. I shall have to wait, unless you have ideas.
Until then, goodnight to you from Captain Red-cilia and his parrot Polly.
James
PS: I shall deliver my verdict once I have mulled things over for a while longer!
The question of what constitutes life is a slippery one! After spending a good deal of time thinking about it over the years I’ve come to the conclusion that there is a continuum from “inorganic” chemicals to multi-cellular organisms and that where one chooses to insert the “life/not-life” dividing line is somewhat arbitrary. Perhaps the most interesting aspect of this question is in the search for extraterrestrial life, in which the question becomes: What evidence is required in order to conclude that there is life? What is the unequivocal signature of life?
ReplyDelete"...a new strain of giant virus called Mamavirus." Cute.
ReplyDeleteI must say that post was pretty deep. I'm still having trouble getting my head around a virus growing abnormally large as it is infected with a smaller virus - I've always just envisaged them as particles.
As with the definition of life, I think my opinion has always been, like many other things, it is like a convention. Just because it's defined a certain way does not necessarily make it so.
As for the nightsweats and mucus, there seems to be a trend with ailments in that symptoms generally are worse after nightfall. I actually can't think of any other ailments (other than migraines) that may be worse during the day.
Martin, if you had studied BIOL1040 then you would recall that the search for extra-terrestrial life (SETL) doesn't fulfill the conditions of an hypothesis (not falsifiable)! Food for thought from a first year subject, anyway.... :)
ReplyDeleteJames,
On the (topical) definition of life-virus paradox: if we consider a virus to perform several very complex chemical reactions (albeit using an exquisitely designed free energy system) we can also consider, say, a cell as being able to perform a very complex bunch (didn't use 'series' because they also occur in parallelum) of chemical reactions within certain free energy constraints. After all, a cell does not 'decide' that it is hungry and then goes hunting; as far as molecular biology and cell physiology has shown, a cell receives certain stimuli which cause it to move in a manner very similar to hunting. When it meets its prey, it then undergoes chemical reactions on the membrane surface which cause it to engulf its prey (with lots of munching noises!). When this is extended to a collection of cells, it is quite easy to see the same sorts of chemical reactions driving a bacterial colony. Does this continue on to multi-cellular organisms (i.e. are they intrinsically different to bacterial colonies?)?
So, by extension, does this mean that our consciousness is determined by such purely physical/chemical phenomena? Or is there more? Do large collections of cells exhibit some kind of 'hive mind field' (all 'intelligent' animals seem to be large collections of cells, after all) or is our mind merely a consequence of an efficient survival mechanism? Or is it perhaps a consequence of certain chemicals/electrical potential arrangements (if so, we could probably make an intelligent computer by replicating a brain's potentials). If an amoeba had consciousness, what would it do? How would we find out? !?!?!? And finally, do amoebas deserve the same rights as 'sentient' humans?
Besides these 'metaphysical' questions (for want of a better word, perhaps), it seems to me that you can make a new criterion for life: if a thingy performs complex chemical reactions with other thingies (also performing complex reactions) with (perhaps) the goal of reproduction (? not sure if this is even necessary) it is alive. So, reproduction is here just viewed as Of course, viruses could easily be thought of as 'cassettes' that simply provide a means for transferring DNA between hosts. Their self-replication techniques could (for some reason) be an evolved mechanism to maintain the integrity of their (supposedly vital) information. It is conceivable that viruses arose as a method for cells to improve the survival chances of their neighbours (there would have been some weird stuff going on!) but nonetheless viruses do make exceedingly useful vectors for transferring information into a complex cell (or even to provide enzymes used in genetic engineering).
Also, what about prions, those naughty proteins that misfold one's brain (what a pun!)? Is the strange quantum stuff that happens with protein folding interactions (among other things) somehow linked with consciousness?
(the obligatory) Any thoughts? (anyone feeling slightly amoeba-ish? he he he...)
Tester post. Administrative only.
ReplyDeleteMore stuff!!
ReplyDeleteI greatly chastise those vectors for leaving the toilet seat up! That is a declaration of war.... This is perhaps what leads to the virus-life question. You also forgot about feet on train seats, eating on train seats, drinking on train seats, being loud in the quiet carriage, etc..
According to my (admittedly limited) knowledge of physiology, the majority of effects you feel when infested with viral infections are your body's way of dealing with them (if the virus was successful in killing all of your cells, you would feel, well, dead). A lot of these effects are very immune-system dependent and your physiology is very finely in-tune with the circadian rhythms of night-and-day (this is easy to look up). So, it is sensible that (especially for respiratory infections) that your body (in addition to dealing with all the muck and radiation you pick up during the day) has cyclical 'worsenings'. Your body probably 'realises' that you will be sleeping soon and increases the processes that will defeat the invasion (these processes, like excessive mucus production and inflammation, are often very unpleasant). Coughing is both a symptom of mucus production but can also be your body's way of removing spent immune bits (as yellowy phlegm).
I suggest a look into immunology to investigate this. Physiological immunology (in fact, there are people at Uni who study this!!!).
About interesting viral thingies: while I do not think that a virus would eat other viruses (they're ridiculously finely tuned to be able to do their job with that tiny amount of DNA and only a protein coat), a virus can, of course, influence the formation of another virus while both are inside the cell! This means we could use viruses to fight viruses (I have a SciFi game where this kind of 'anti-virus' is called a protovirus, although it is a little different). Care would need to be taken to prevent mutations creating bad problems (viruses are successful at creating useful mutations because there are ridiculous amounts of them and their small genome is VERY easily mutated—no room for checking mechanisms—allowing them to ditch useless DNA for useful bits very easily. This does mean that once a virus has 'adapted' to infect another cell type, it generally loses ability to infect the old cell types. And, of course, since most multicellular cells are basically the same on the outside, it is very easy to retain some residual infection capacity when the trigger for infection is simply as slight a difference as the change from a glycoprotein alpha linkage to a beta linkage or a changed hydroxyl group position)
As per my other post, I think it more likely that viruses evolved as a DNA vector that gradually developed a more and more advanced protein shell for effective transport (presumably the replication genes had been stabilised before a mutation caused viruses to kill their hosts when escaping). Not all viruses need be detrimental; every human that has been in contact with air already has heaps of retroviruses in their genome. Does anyone know of any (not engineered) beneficial viruses? The main thing is, most aren't passed on because most viruses don't infect germ cells. This is a potential problem with cloning using non-germ cells: you pick up the retroviruses! This could have detrimental effects on a growing organism.
ReplyDeleteI also think that a lipid membrane would be unfeasible for viruses. Firstly, a virus is not to0 much larger than the size of some of the proteins in eukaryotic membranes: it doesn't have room (either in size or in DNA) for all those proteins and stuff to make a working lipid membrane that is 'quasi-nucleic' and it has no way of obtaining sterols and other complex molecules for the membrane via its own DNA (too small); I don't know if you could get the virus workings with such a small membrane. Protein coats are also a lot more sturdy, rigid and versatile than lipid membranes, helping a virus to survive without its hosts. Additionally, glycoprotein coats are easier to use for breaking into lipid membranes because you don't have to code for proteins that allow vesicle endocytosis. Also, how would viruses get a cytoskeleton?
Despite these, it is also conceivable that a virus genome could have become ensconced within a vesicle inside a cell. The protein coat could then have developed into some kind of DNA organisation protein. The only issue is whether or not there would be enough coding for the quasi-nucleus to take on the DNA from the nucleosome. This could then be possible.... The resultant cells would, of course, not be eukaryotic yet. Another question is what is the relationship between these viro-nuclei and chloroplasts and mitochondria (etc.)?
Josh H
PS: Where are we today? :) Meet at Tea Room?