Does evolution help bad germs to survive?

Question

I'm told evolutions purpose is to make the strong survive. Will the strong germs just get stronger and who will eventually win the battle? Sounds like the good guys versus the bad guys...james the hollow earth man

Answer 1

ANY germ is more likely to survive if it has characteristics that give it an advantage over other bacteria - good or bad!  The genetic information inside bacteria is constantly changing (mutating) which allows them to evolve so quickly. BUT these changes only occur if there is a selective pressure.  So the "bad" bacteria you are referring too, like MRSA or VRE in a hospital, are actually pressured to become as dangerous as they are because we try to kill them all the time.  Say, we take antibiotics, wipe a bench, or sanitise equipment in a hospital, and 99.9% of the bacteria are killed. The 0.1% that are left obviously had some advantage to help them survive.  By killing off the competing bacteria, the more hardy (and dangerous) bacteria can now flourish in greater numbers.    

So we will continue to find ways to kill bacteria while they continue to evolve because of it.  So to answer you question "who will win the battle?"  Well bacteria were around long before us...and I reckon they will be around long after us.    However, us humans are a resourceful bunch - always finding new ways to solve problems - so I think we are safe for now.

Answer 2

You have it reversed a little.  It's the fact that the strong (or best suited to their environment) survive that drives evolution.  Your question is a good one, though.

Germs do evolve, but so do their hosts.  Viruses, in particular, rely on their host's cellular machinery to reproduce.  If the machinery changes even a little bit, then the virus will be unable to take advantage of it.  In any population, there will always be a few individuals who are immune to any particular virus.  If the virus spreads through the population, they will be more likely to survive, and some of the next generation will inherit the immunity.  Given time, the virus will mutate such that it can bypass the newfound immunity, and the cycle will start again.

Usually, it takes place in small increments, making it unlikely that a virus will make a huge leap and mutate into a doomsday virus.  Since the steps are small, it's easier for the host to adapt.  The trouble comes when a virus comes from a different population, one where the virus and host haven't been adapting side-by-side.  This happened with smallpox during the colonization of America.  The smallpox virus had been common in Europe, and while it was still a serious matter, they had developed a baseline resistance to it.  The native Americans, though, had never been exposed to smallpox, so had never developed a resistance to it.  The virus spread like wildfire and caused enormous numbers of deaths.

It's basically an arms race between germ and host.  For every mechanism that a virus or bacteria evolves, animals will eventually develop an immunity... which the virus will eventually evolve to bypass.  An so it goes, on and on.