If the magic of life is dazzling here, it is out there too. Among the stars, the search may be difficult, but what about within the catacombs of our mind? If, ‘seeing is believing’, then thinking and understanding is certainly philosophy. Let’s take a fresher look in all that we know of, polish a little, and start a fresh chain of thought. Why not shed the boundaries of scientific disciplines, start at the very beginning, and think, as we walk the walk of life.

Who says the answers are impossible?

Wednesday, 9 November 2011

The importance of being a virus


Last week, when we were discussing panspermia, viruses came by as a passing entity in my blog. You can call it my nostalgia for my graduate research or, with a pinch of salt, consider it to be an inevitable parameter whenever panspermia is the topic of debate!
Which way ever it may be, today, I will keep to the viruses and try to clear their name of all wrong doing a bit. The other day, I saw a wonderful article on Astro-virology (Does the name sound uncanny?) in Astrobiology Magazine (In Search of Virus Fossils). To be frank, I was really taken away by the article and the kind of research undertaken by Dr. Ken Stedman of Portland State University and his colleagues. To give a brief about their research, they well be searching for viral fossils, yes, you got me correct, in high-silica hydrothermal ecosystems and evaporative brines, two distinct ecosystems, which have earlier produced quite a few microbial mysteries and shocks. It should also be noted, in the author’s own words, ‘these will be probable ecosystems, where we will be searching for life in other planets’.
Truly, the role of hydrothermal vents, underwater volcanoes and extreme saline environments in the origin of life in earth and other astral bodies like Europa and Titan cannot be ruled out. So, discovery of viral fossils in such an environment will definitely be the icing on the cake, obviously you have to get hold of the cake first anyway.
Now coming back to the topic of my discussion today, that where do viruses stand with respect to panspermia? We sure can stumble upon some interesting facts. Though, in every sense, a virus is an inanimate entity outside its preferred host, but their strange attributes and importance in shaping the Earth’s biosphere can hardly be overlooked from a biochemical perspective.
If you happen to imagine a living subject as a CD player, you can safely attribute the viruses to be the CDs playing your favourite songs. The CDs have the songs and information written on to them in a strange language of leaser cut dots on silicon surfaces. Nobody can read them, or play, until you through them into your CD or DVD player, and then they literally become your favourite singer, directing your Boss sound blasters to buzz in your favourite lyric!
 Strange analogy, isn’t it?
 If you happen to probe deeper, you can see more similarities! Your favourite CD player, with all its complex electronics is never invincible, whereas, a CD is! It can survive the test of time in a more durable fashion, owing to its simplistic design, compared to your favourite musical electronics.
Now, when we humans can think of such an innovative way of storing and immortalizing information, why not life itself can come up with something like that? After all information shuttling and processing is an integral characteristic of biosphere itself. Believe me, life did such a thing, and viruses are the most possible answer that comes to the mind!
Ok, now wait a minute, what am I saying? Viruses are only known kill, right? So how can they be a medium of information transport? And why the hell, biosphere, or life itself, will use such a vicious entity for any good, you may as well ask.
In that situation, we need to go down a little on understanding what life actually stands for. In my previous blog, in passing, I have remarked that for life, as a concept, an individual centric benefit is never considered important, when the matter concerns the welfare of the whole species or the biome. True to every sense, viruses are nothing more than killing machines, but they do provide evolutionary challenges to their host. More so, viruses, like the one which gets integrated into the host genome, may shuttle new traits in or within species, which the host may not be able to acquire through sexual reproduction or round the mill evolution. Recent reports even show that 8% of human genome is made up of retroviruses having quite dubious and unmapped functions. This process of viral genome integration into the host is called endogenization, and has been in action for millions of years.
 If you are in a mood of exponential speculation like me today, you can as well think that the traits, which we humans are so proud of called intelligence, could be fallout of such processes of viral endogenization over our close primate ancestors! An interesting report in the Journal Nature (Bornavirus enters the genome) talks about the remarkable story of Bornavirus which cause neurological disorders in human. Its clinical manifestations range from psychiatric conditions such as bipolar disorder and depression in patients. This virus causes infection by integrating into human genome. Now, in a sublime sense, if you consider the evolution of human intelligence as a stable and desirable physiological outcome over our nearest siblings in the primate world, it won’t be a matter of wonderment, at least for me, if it is discovered some day, that it all happened through some retroviral endogenization into the human genome, few million years back, which the other primates fought back!
Anyway, it does seem from all this discussion that I may have been able to convince you all that probably, viruses are not so bad an entity to start with, but what about panspermia? Well, it might also have a role in that too!
It will be an insensible gesture to jump to conclusions, like; all new viruses which emerge suddenly and create havoc in our lives are coming from the stars and because of panspermia. No, that’s not a possible to sell easily. To sustain a stable infection in any species, a virus has to use molecular mimicry and full-on deception to enslave the host system. The virus can only do so, if it knows its host or some related species inside out, over many generations through prolong coexistence and competitions. The viruses, which would be important to panspermia would be minimalist and would be far flung from the complex SARCs or HIVs. It’s not so difficult to understand why.
Consider the possibility of origin and evolution of life in any other plant in our solar system excluding Earth. We can as well consider Mars in this example. In such a scenario of life evolving in both the sister planets of  Earth and Mars, in parallel, a few billion years ago from a similar starting biochemistry, it’s will be hard to believe that both the biospheres will have the same attributes over time. There will be radical divergences, owing not only to their cosmic separation, but also depending on the path evolution will proceed, taking into account geological, atmospheric and other allied factors in these two planets. The game of predator and prey would be common to sustain a food or energy chain in both the biospheres, and you could also imagine Martian viruses with their unique parasitic life cycle. Depending on the host these viruses will be thriving on, there will be an array of their repertoire and thanks to the advantage of reductionism in viral survival concept, these predators will far outnumber their pray by a factor of 10 (a mere conservative estimate).
In a situation such, let’s consider this scenario. One fine day, a colossal meteorite strikes the surface of Mars. Its impact creates a massive creator on the surface of the planet. Rocks are sputtered like sharp nails all over and some of them gaining escape velocity leave the planet for good. Now, these rocks become meteorites and space debris themselves and start orbiting the void of space getting tugged, one way or the other, by the gravitational pull of other planets. Some of them in a distant future are destined for the nearest planet earth, because of the orbit they will take eventually.
Now, these rocks may, or may not be completely barren pieces of debris. Before the impact, they may have been the niche of a thriving Martian microbial biome. Therefore, all the life associated with the rock will also take this astral ride. In due course of time, the heat generated by the meteorite impact, cosmic radiations, absence of any life sustaining atmosphere in deep space and other factors will mostly sterilize the rock of any life. Few specimens may survive, if they go into hibernation of spores or are in concealed protective pockets inside the core of rock. Who knows, but the odds are far against them. Anyway, by the time these rocks land up in Earth in a few million years, (here again you have to consider the extreme temperature produced by the entry event of the rock into earth atmosphere) they will be completely void of life, and one can only hope to see traces of microfossils, and organic residues, if probed deeper with sophisticated instruments. Reading all this, you may as well conclude that this is a lost case of failed panspermia, but is it?
What if, if we consider that those rocks, along with microbial ecosystem, before the impact, also had Martian viruses? In our earth, consider any environment; viruses outnumber microbes 10 to 1. So will it be true for our imaginary Mars biosphere to?
 With a conservative estimate on an alien biosphere, if we reverse the odd to 1 to 10, then also a large population of these hypothetical viruses will be taking this cosmic ride to earth. Being inanimate outside their host, their chances of safely reaching earth intact is exponential compared to Martian microbes.
Now, here comes the important question, will they be able to sustain a panspermia?
This answer, I have tried to justify in my last blog. To say in a few words, ‘It’s complicated!’ The advance Martian viruses won’t. For them, the native earth population with its divergent biochemistry will prove to be a bigger and impossible challenge (Think of playing a CD on a cassette player). However, you cannot rule out the minimalist ones. The simpler a virus will be in biochemistry, the easier it will be for it to adopt to a new host in an alien world, though there will be a billion failed attempts anyway. Here, for the first time, the odds are high in favour of a successful panspermia, because, you are not talking about a biochemical invasion of a different world by a protein, nucleic acid or a lipid molecule but by a successful, proven and tested replicator.
Is it possible?
 Well, maybe, who knows! It may well be happening, now also, in some isolated environment here on earth.
Can we find such Astor-viruses ever?
Well, it will be a crime to say no, but the experimental design to discover them will be tricky. Here, we are not talking about any ordinary virus, but a class of extreme predators, who would be not only quite simple in biochemical architecture, but will also have a less prominent phenotypic expression. They will hardly compromise their host to extinction, for if they do so, their own existence is gone for good and all the cosmic travel of a few million years is of no use.  However, they will still have their distinct signatures. Remember one thing, since they are of other worldly origin, there will be definitely some level of divergence. It could be in their use of unnatural amino acids for their protein, use of out of ordinary purines and pyrimidines in their genetic code or strange replication models. Only time can tell where will be the differences.
Until then, let’s hope for the best and stop fearing that viruses are coming from the space to kill us all! Such thought can be too good for science fictions but disaster for pure biochemistry. What do you say?


No comments:

Post a Comment