Posted on 09/26/2002 3:12:44 PM PDT by Heartlander
Tough Earth bug may be from Mars
19:00 25 September 02
Exclusive from New Scientist Print Edition
A hardy microbe that can withstand huge doses of radiation could have evolved this ability on Mars.
That is the conclusion of Russian scientists who say it would take far longer than life has existed here for the bug to evolve that ability in Earth's clement conditions. They suggest the harsher environment of Mars makes it a more likely birthplace.
The hardy bugs could have traveled to Earth on pieces of rock that were blasted into space by an impacting asteroid and fell to Earth as meteorites.
Deinococcus radiodurans is renowned for its resistance to radiation - it can survive several thousand times the lethal dose for humans. To investigate how the trait might have evolved, Anatoli Pavlov and his colleagues from the Ioffe Physico-Technical Institute in St Petersburg tried to induce it in E. coli.
99.9 per cent deadly
They blasted the bugs with enough gamma rays to kill 99.9 per cent of them, let the survivors recover, and then repeated the process. During the first cycle just a hundredth of the lethal human dose was enough to wipe out 99.9 per cent of the bacteria, but after 44 cycles it took 50 times that initial level to kill the same proportion.
However, the researchers calculate that it would take thousands of such cycles before the E. coli were as hardy as Deinococcus. And on Earth it would take between a million and a hundred million years to accumulate each dose, during which time the bugs would have to be dormant.
Since life originated on Earth about 3.8 billion years ago, Pavlov does not believe that there has been enough time for this resistance to evolve.
Dormant bugs
On Mars, however, the researchers calculate that dormant bugs could receive the necessary dose in just a few hundred thousand years, because radiation levels there are much higher.
What is more, they point out that the Red Planet wobbles on its rotation axis, producing a regular cycle of climate swings that would drive bacteria into dormancy for long enough to accumulate such doses, before higher temperatures enabled the survivors to recover and multiply. Pavlov reported the results last week at the Second European Workshop on Astrobiology in Graz, Austria.
David Morrison of NASA's Astrobiology Institute is sceptical that Deinococcus came from Mars, pointing out that its genome looks similar to those of other Earthly bacteria. But he admits that there's still no obvious explanation for the bug's resistance to radiation.
"It is certainly a mystery how this trait has developed and why it persists," he says.
-Stuart Clark
Other stuff:
Spider mite upsets evolutionary theory
I can't believe any of their numbers. They started off by killing nearly all(how can they determine that before the fact?)of the bacteria with a dose one hundredth of the lethal dose for humans. They improved it by a factor of 50 after 44 trials. That means that they achieved a kill of nearly all the bacteria while still only using 50% of the dose needed to kill a human(whatever that means, MLD is a clear standard). See my post 6 for the fact that E.Coli resistance is 1000 times greater that human resistance by the numbers of my unattributed citation.
44 cycles. 0.1% survives at each cycle. You tell me how many E. coli they would have had to start with. I imagine at each cycle they had to test a series of radiation doses as well.
Each cycle represent several generations.
By titration and estimation of original population.
Before the fact?
You mean that it was a shoot-look-shoot... tally endeavor?
There is an exception to this rule. Or there isn't.
Senator Daschle, you may call it what you like. I'm outta here.
I do not see this as proof of evolution. I see this as proof of speculation, quick conclusions, and dogma within the scientific community.
I am no ‘theory of common descent’ advocate.
Actually, I was curious to see how the ‘theory of common descent’ advocates would respond to one of their own – that is the scientist in this article – Pavlov.
I’m just ringing the bell for him :)
I'm sorry you find questions of simple protocol difficult to answer. I don't know how they supposedly accomplished this feat since their numbers don't make sense. That is why I ask the questions. 1.5KGrays to 3KGrays seem to be close to 500 to 1000 times greater that 3Grays as my citation lists. So I don't know where they got the "sissy" E. Coli.
There must be! Exept if... If there were only some place where there isn't any trouble. Somewhere....
Schön's productivity was astonishing too. In 2001 he is reported to have averaged a new paper every eight days including four in each of the leading journals Nature and Science. Most scientists would be delighted with four papers a year in any journal.
In an appendix to the report, Schön says he disagrees with several of the report's conclusions but admits to have made "mistakes", which he "deeply regrets". He adds that he remains convinced that the physical effects he reported are real, and will be reproduced in future
No problem. For this experiment, without regeneration, you'd need 1x10^88 bacteria. Not in the billions as you propose. A billion would take about one night to grow in a 1/2 liter flask.
My abacus comes up with the same number.
Are human males next by an “infection by an as yet unclassified bacterium”? LOL!
--Boot
Then I don't at all understand what they are saying in the sentences I quoted. It certainly sounds to me that they are integrating the radiation dose over a 3.8-billion-year timescale, and saying that the result is too small (a totally invalid calculation).
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.