Germs Taken Into Space May Come Back Deadlier

westlake writes "Sounds like the plot for a B-movie, doesn't it? Germs go into space and come back stronger and deadlier than ever. Except, it really happened. In a medical experiment, salmonella carried about the space shuttle in the fall of 2006 proved far more lethal to lab mice than their earth-bound source. 90% dead vs. 60% dead in twenty-six days, with half the mice dying at 1/3 the oral dose. Apparently 167 genes in the space-evolved strain had changed. The likely cause: In microgravity the force of fluids passing over the cells is low, similar to conditions in the gastrointestinal tract, and the cells adapted quickly to the new environment."

conditions outside the body

[mrvan]

TFS states that the deadliness is bacause the germs were adapter better to the conditions inside the body, so kill lab mice faster. Outside the lab, these germs will have to pass from host to host, and presumable in between the hosts conditions will be less like microgravity. SO, they might be deadlier, but with less rate of infection. A deadlier disease with lower infection rate might actually be less of a risk: hosts die more quickly and not enough new hosts get infected.

Also: if the new germs are really more well-adapted (ic better at multiplying and spreading), wouldn't they have evolved like that on earth? Especially since the evolutionary step is apparently small enough to be attained by a limited colony in a very limited time?

Vonnegut

[stoolpigeon]

he said the whole point of life is to create germs tough enough to make it through space on a rock. i think he would have chuckled at this.

Re:conditions outside the body

[s_p_oneil]

"Also: if the new germs are really more well-adapted (ic better at multiplying and spreading), wouldn't they have evolved like that on earth? Especially since the evolutionary step is apparently small enough to be attained by a limited colony in a very limited time?"

Not necessarily. Evolution is like a simple hill-climbing algorithm in computer programming. It blindly heads in any upward direction without any way of knowing if it will get stuck at the top of a small hill when there is a much bigger hill right next to it. It is unnatural for it to go back downhill (to weaken itself) on purpose to look for bigger hills to climb. But changes to the environment distort the landscape, in some cases turning hills into valleys and forcing life to climb back up or die out.

So most likely the germs had their little hill turned upside down in micro-gravity and were forced to climb up to the top of a new one. Their landscape got turned upside down again when they came back down to Earth, and they ended up finding a bigger hill than the one they started on.

Amen to that

[DrYak]

Outside the lab, these germs will have to pass from host to host [...] less rate of infection. A deadlier disease with lower infection rate might actually be less of a risk: hosts die more quickly and not enough new hosts get infected.

This is something like Rule n1 when dealing with epidemiology.
And something that is systematically neglected when the media try to instill mass hysteria about some latest bug.

Compare :
- Plague : kills, but slowly, and very good at transmission - did decimate population.
- Spanish flu : was deadly, but did spread very easily (specially at a post-war time with limited availability of medical means) - did kill quite a few people.

With :
- Ebola : violently deadly in an almost "B movie gore"-style, but sucks at transmission (kills to fast. The virus has almost no time to leave the host before killing it) - never became a widespread disease.
- Avian flu : it was severe in the handful few people who caught it (although one may contest that those people were mostly in developing country and thus had limited access to medical means) BUT it's far from effecient when it comes to transmission (it's a birds' disease, damn it) one must almost live everyday with and almost sleep with chickens to catch it - hasn't been epidemic yet, and won't be, at least not until it mixes with human viruses (not very likely to happen quickly on a large scale).
- Mad cow disease : kills slowly (brain slowly becomes a sponge) but has one of the most improbable mecanism of transmission (one must eat brain or brain derivative) - never was a widespread disease (at least outside cannibal communities).

And same will happen with lysteria-from-outer-space : Yes, it kills mice efficiently. But basically it has changed. It has traded characteristics that where good in surviving on earth, for characteristic that are good for microgravity, and that happen to be good for the intestine too. Thus it will probably completely suck at propagating.

Re:conditions outside the body

[TubeSteak]

The researchers found 167 genes had changed in the salmonella that went to space.

Why?

"That's the 64 million dollar question," Nickerson said. "We do not know with 100 percent certainty what the mechanism is of space flight that's inducing these changes."

However, they think it's a force called fluid shear.

TFA talks about fluid shear while many other articles http://news.google.com/news?q=space+biofilm [google.com] mention that in space, the bacteria forms a biofilm.

More importantly, it seems like every other article answers the "64 million dollar question." The answer:

The researchers' experiment revealed that a genetic switch called "Hfq," which may control more than 160 genes in S. typhimurium, turns on in space and causes S. typhimurium to become three times more virulent than on the Earth's surface.

I'm not really sure why this AP article is so deficient.

Organisms Change Randomly

[Anonymous Coward]

Evolution does not climb hills to reach a preferred state. Sometimes it backtracks downhill to find an old working state. It may climb to the other side of the hill, because that's where the sunshine is. Evolution means that a specific organism is fit to live under the current conditions.

Organisms aquire their specific survival skills by DNA mutation or recombination, or absorbing other organisms (see mitochodrion). Evolution theory does not explain why favorable changes happen; they are just "happy accidents".

People have been able to force DNA recombination through selective breeding. Darwin gave dogs as an example. Today, we might do the same to weaken diseases (http://www.pbs.org/wgbh/evolution/library/10/4/l_104_01.html [pbs.org]Cholera: Domesticating Disease).

Exactly, What's More

[BlackGriffen]

Because the fitness landscape for any individual organism must include the effects of the other members of his species more interesting things can occur. The worst part is that either effect can occur - the main population can either deepen the well or make it more shallow. In the former case you have a strong tendency towards monoculture even on non-optimum points - think Windows. In the latter case the organism will tend to "fill up" the local minimum and eventually, population constraints being favorable, spill over into any nearby lower areas. Thus, either creating a new species that splits off or out-competes its parent species. The nice part about this model is that it offers another way for apparently discontinuous jumps to appear in the fossil record even when there is no evidence for similarly discontinuous changes in the environment.