Comments on: When competition is intense, viruses spill over into new hosts Mon, 26 Nov 2012 12:00:51 +0000 hourly 1 By: A. Peon Thu, 25 Oct 2012 14:10:10 +0000 This writeup seems awfully anthropomorphic (evolution ‘wants’ to happen! competition makes things ‘better’!). Viruses, including bacteriophages, are basically chemicals (and so are people, but the complexity on the viral scale is much reduced). If the probability of a ‘favorable’ mutation is fixed per unit of viruses, should it really be ‘surprising’ that adding more viruses increases the speed with which that mutation appears and is replicated enough to detect?

This is useful science, and it’d be particularly interesting to see this uncovering latent mechanisms that actually exist in a ‘stock’ genome (such as the human pathogen examples given), but from the description I’m not seeing how this particular scenario demonstrates anything other than that ‘statistics happens’ – you have some available hosts the standard virus didn’t come ‘built for’, and the chance of a mutation that permits infection increases as you have more viruses so more possibilities for mutation.

By: Field Fri, 19 Oct 2012 22:05:25 +0000 This is confusing because it implies viruses are naturally happy with a certain level of food, but the reality of what we know about them (or that I know) is closer to bacteria. They are opportunistic in nature, always seeking to eat and multiply. That is what they do… just in different ways.

Could it be these more robust versions of viruses don’t naturally reproduce as fast, so we don’t typically see them as much? But if you stress the immune system you allow them to propagate consistently for a longer period of time?

When I read this, my thought was ‘cure for HIV?’ I was being optimistic thinking about the possibility of displacement. But actually the possibility for something more like super-HIV could occur. I guess testing on how HIV responds to competition, in evolution, could be interesting. Is it possible for a virus to evolve so well that by creating such a strong outer-layer it could actually slow down how fast it replicates, and perhaps squelch the ability to interact with a lot of the regular food buffet it is use too? See if you introduced competition that had to be fed with introduced food, but it forced/allowed changes in the HIV, you could selectively stop the quick changes by not feeding the introduced virus as the most opportune time.

What if the person who was cured with the bone marrow transplant wasn’t cured because of the re-energized immune system with fresh not-so-taxed marrow, but rather because of the gap in immunity that allowed evolution of the HIV to turn into something that was giving heritable qualities associated not with speed and evasion but something else?

I suppose the idea might just be a way to kill the host quicker, but I’ll stick with optimism.

By: David E Fri, 19 Oct 2012 01:25:16 +0000 This is totally unconvincing. It is not clear that competition had anything to do with the result. Some individuals of ph16 may have the ability to infect P.glycinea. In a 100-fold sample they should certainly be more likely to occur. Given only P.glycinea as a substrate, they will flourish while the typical individuals die out. In the meagre sample, perhaps none or extremely few of these types occur.

By: Totto Wed, 17 Oct 2012 09:31:26 +0000 “The broader point – that competition between infections can make things worse for hosts – applies beyond viruses. It also has direct relevance to our own health.”

This is important. And to think about how to experimentally provide evidence of the nature. Maybe it will lead to understanding of the virulence of the agent itself. Interesting read :)

By: W. Benson Wed, 17 Oct 2012 01:39:41 +0000 Other studies showing intraspecific competition favors the evolution of reduced specialization (wider niches):

Daniel I. Bolnick. 2001. Intraspecific competition favours niche width expansion in Drosophila melanogaster. Nature, 410: 463-466. ´[paywall]

Richard Svanbäck + Daniel I. Bolnick. 2007. Intraspecific competition drives increased resource use diversity within a natural [stickleback] population. Proceedings of the Royal Society, B, 274: 839-844. [free pdf where I live]