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cran
2005-Aug-10, 05:26 AM
Researchers Probe How An Ancient Microbe Thrives And Evolves Without Sex (http://www.sciencedaily.com/releases/2005/08/050805065807.htm)
'A January 2004 finding by biologists at the Josephine Bay Paul Center for Comparative Molecular Biology and Evolution added important evidence to the radical conclusion that a group of diminutive aquatic animals called bdelloid rotifers have evolved for tens of millions of years without sexual reproduction, in apparent violation of the rule that abandonment of sexual reproduction is a biological dead end. Now, MBL scientists are beginning to understand just what's different about these creatures' DNA that has enabled them to succeed where other asexual species have failed.' from ScienceDaily.com

"no sex please, we're bdelloid...?" :wub:

piersdad
2005-Aug-10, 07:33 AM
well the human race is well behing the 8 ball these critters have been cloning around for ever

cran
2005-Aug-10, 09:28 AM
It does kind of put a different twist to "meet my other half"... :)

piersdad
2005-Aug-10, 09:42 AM
many bacteria divide to multiply so the discovery of non sexual multiplication is not new.
their work on it is good as it can lead to better understanding of cloning and eventually making of new body parts cloned from the recipient.

Some thing that interests me is that billions of years ago the radioactive materials we have present today in the earth have various half life times
so i would surmise that 3 billion years ago there would be a heck of a lot more of radiation present

this would then cause more frequent mutations would have speeded up evolution with very frequent mutations and die offs of bad and survival of the better.
Just as exposure to radiation today causes mutations so this must have occured a lot more frequently in the past creating the first multicelled animals that then started to prey on each other and evolve a different way

cran
2005-Aug-10, 10:47 AM
many bacteria divide to multiply so the discovery of non sexual multiplication is not new. yeah, I got the impression from the article (reading too much between the lines perhaps?) that this was an evolutionary 'backflip' - an organism that evolved sexual reproduction...then at some point 'devolved' back to asexual reproduction... :unsure: otherwise, it wouldn't be news... :unsure:

so i would surmise that 3 billion years ago there would be a heck of a lot more of radiation present ... this would then cause more frequent mutations would have speeded up evolution with very frequent mutations and die offs of bad and survival of the better. ...that's my understanding...I think there have been some fairly good estimates of the long-lived isotopes...less confident is the amount of the very short-lived ones...or even when to begin counting from (given accretion process; differentiation and degassing; crustal formation and early evolution... :blink: )

piersdad
2005-Aug-10, 10:19 PM
only have to look at birth defects today from radiation and in very primitive life forms a microbe with 4 appendages instead of two could be the surviver that multiplies

cran
2005-Aug-11, 04:05 AM
yep :) ...and one of those mutations might have been microbial 'siamese twins' - the first multicell! :D

suitti
2005-Aug-11, 02:32 PM
3 billion years ago there would be a heck of a lot more of radiation present

Possibly. Many species can control their intrinsic mutation rate. My understanding is that E. Coli can do this in repsonse to the current environment. The colony ramps up and down the mutation rate all day long. Apparently, they have a number of genetic resources that can be turned on and off. So unlike normal mutations, this is a mechanism for choosing the next mode to cope with the changing environment. Just try everything and see what works. This is how DNA thinks.

How many asexual microbes does it take to screw in a lightbulb?

One. And there's plenty of room - especially compared to what the mice have to put up with. :P

[note to editors: And don't start a sentence with a conjunction. (Remember, too, a preposition is a terrible word to end a sentence with.)]

jkmccrann
2005-Dec-18, 12:51 PM
Possibly. Many species can control their intrinsic mutation rate. My understanding is that E. Coli can do this in repsonse to the current environment. The colony ramps up and down the mutation rate all day long. Apparently, they have a number of genetic resources that can be turned on and off. So unlike normal mutations, this is a mechanism for choosing the next mode to cope with the changing environment. Just try everything and see what works. This is how DNA thinks.


No wonder E. Coli is such a hardy and annoying microbe. It would sure be interesting if one day we managed to evolve our own intrinsic mutation rate, though I think we'd probably go down the cyborg route before we ever had that capability, although I guess if you think about the potential implications of nanobots and the effects and capabilities they may one day have in regulating our health, is that akin to controlling our own internal mutation rate, in a way? Or is that going down the cyborg route?

It almost comes back to a philosophical argument if you start going down that path, the mind boggles..............

beskeptical
2005-Dec-18, 06:31 PM
OK, I could go look this up but it's easier to just have you folks share what you already know.

Before ozone how much and which wavelengths of radiation got through? Because the magnetosphere blocks a lot of radiation. So wouldn't the biggest change be UV radiation? And that might have much less impact on ocean creatures. And then didn't land creatures evolve after O2 increased in the atmosphere? Did ozone take much longer to form?

So, just give me the quick version here of when more radiation was causing more mutations, if someone could be so kind, thanks.

beskeptical
2005-Dec-18, 06:43 PM
Possibly. Many species can control their intrinsic mutation rate. My understanding is that E. Coli can do this in repsonse to the current environment. The colony ramps up and down the mutation rate all day long. Apparently, they have a number of genetic resources that can be turned on and off. So unlike normal mutations, this is a mechanism for choosing the next mode to cope with the changing environment. Just try everything and see what works. This is how DNA thinks....Well, perhaps I'd call it a reflex rather than a thought. Reflexes occur before the nerve impulse reaches the cortex. That's why they are quicker, they require no thought.

But the E coli mutation thing was interesting. I hadn't heard that before. Here's an article on the research of the phenomena. (http://www.bcm.edu/fromthelab/vol02/is7/03july_n1.htm) I had to look into it and yep, sure enough, there is evidence. The changed environment has to be stressful and can even be completely incompatible for the little fellas, apparently.

SirBlack
2005-Dec-18, 11:40 PM
No wonder E. Coli is such a hardy and annoying microbe. It would sure be interesting if one day we managed to evolve our own intrinsic mutation rate, though I think we'd probably go down the cyborg route before we ever had that capability, although I guess if you think about the potential implications of nanobots and the effects and capabilities they may one day have in regulating our health, is that akin to controlling our own internal mutation rate, in a way? Or is that going down the cyborg route?

It almost comes back to a philosophical argument if you start going down that path, the mind boggles..............

If by internal mutation rate, you mean what's happening to any average cell in the human body, then in this case we want as few mutations as possible. The only mutations analogous to what's happening with those single-celled organisms is either when sperm/egg cells are produced or when those cell combine to produce an embryo.

Actually I suspect, any genetic or chemical reflexes which might increase mutation rate have already been evolved out of us or into a reduced role (and probably for most animals and vertebrates in general). I would expect for a species to really get much benefit from a higher mutation rate, it needs to produce lots of new individuals in a short amount of time. Compared to something like E. Coli, humans are incredibly slow at reproducing.

TheBlackCat
2005-Dec-19, 05:13 AM
Well, perhaps I'd call it a reflex rather than a thought. Reflexes occur before the nerve impulse reaches the cortex. That's why they are quicker, they require no thought.

But the E coli mutation thing was interesting. I hadn't heard that before. Here's an article on the research of the phenomena. (http://www.bcm.edu/fromthelab/vol02/is7/03july_n1.htm) I had to look into it and yep, sure enough, there is evidence. The changed environment has to be stressful and can even be completely incompatible for the little fellas, apparently.
Yep, we covered that briefly in or molecular bioengineering course, because it relates to something else we are studying. I know it is a bit OT, but it is really cool (in my opinion). I apologize beforehand for the anthropomorphization that will follow, but it is kind of hard to describe this in any other way.

Bacteriophages are a type of virus that infects bacteria. One in particular that is well-known is called Lambda Phage. It infects E. coli. What makes it special is that it has two modes of reproduction. One is the normal virus mode where it copies itself into the E. coli genome and causes the cell to mass-produce the virus until the cell dies and the virus is released to infect other cells. This is the lysis pathway. However, it has another mechanism as well called the lysogeny pathway. Often, when the virus infects a cell it copies itself into the genome...and does nothing. One of the viral genes starts to produce a protein that prevents the other genes from being read, preventing the virus from killing the host. The viral genes just sit there. When the bacteria cell divides, the viral genes are duplicated along with the rest of the bacteria genome and both daughter bacteria now carry the virus's genes. The cell can continue living and dividing like this indefinitely, making hundres, maybe even thousands of cells with the virus lying dormant in the genome.

However, eventually the bacteria cell gets some stimulus that causes stress to the system. It might be ultraviolet light, a lack of nutrients, antibiotics, or any number of other harmful stimuli. This triggers the Rec A protein to become active. This protein is the one we are discussing that is involved in increasing the mutation rate of the cell, hopefully giving one of the daughter cells the mutation needed to defend against the whatever is troubling the cell. The presence of Rec A means the cell is in serious danger of dying. The virus is very clever in this regard. Rec A does not normally have the ability to break down proteins, but the repressor that is keeping the viral DNA from activating has a special structure that is broken down by Rec A. This activates the viral genes, causing the virus to take control of the cell and use it to mass-produce more viruses, ideally before it is killed by whatever is troubling it. The virus uses the cell's own defense system to tell it when the host is in trouble and cues the virus to get out before the host dies and destroys the viral DNA. This leaves all the copies of the virus free to infect whatever cells survived the danger. All in all a very clever but very insidious strategy.

beskeptical
2005-Dec-28, 10:16 PM
Yep, we covered that briefly in or molecular bioengineering course, because it relates to something else we are studying. I know it is a bit OT, but it is really cool (in my opinion). I apologize beforehand for the anthropomorphization that will follow, but it is kind of hard to describe this in any other way.

Bacteriophages are a type of virus that infects bacteria. One in particular that is well-known is called Lambda Phage. It infects E. coli. What makes it special is that it has two modes of reproduction. One is the normal virus mode where it copies itself into the E. coli genome and causes the cell to mass-produce the virus until the cell dies and the virus is released to infect other cells. This is the lysis pathway. However, it has another mechanism as well called the lysogeny pathway. Often, when the virus infects a cell it copies itself into the genome...and does nothing. One of the viral genes starts to produce a protein that prevents the other genes from being read, preventing the virus from killing the host. The viral genes just sit there. When the bacteria cell divides, the viral genes are duplicated along with the rest of the bacteria genome and both daughter bacteria now carry the virus's genes. The cell can continue living and dividing like this indefinitely, making hundres, maybe even thousands of cells with the virus lying dormant in the genome.

However, eventually the bacteria cell gets some stimulus that causes stress to the system. It might be ultraviolet light, a lack of nutrients, antibiotics, or any number of other harmful stimuli. This triggers the Rec A protein to become active. This protein is the one we are discussing that is involved in increasing the mutation rate of the cell, hopefully giving one of the daughter cells the mutation needed to defend against the whatever is troubling the cell. The presence of Rec A means the cell is in serious danger of dying. The virus is very clever in this regard. Rec A does not normally have the ability to break down proteins, but the repressor that is keeping the viral DNA from activating has a special structure that is broken down by Rec A. This activates the viral genes, causing the virus to take control of the cell and use it to mass-produce more viruses, ideally before it is killed by whatever is troubling it. The virus uses the cell's own defense system to tell it when the host is in trouble and cues the virus to get out before the host dies and destroys the viral DNA. This leaves all the copies of the virus free to infect whatever cells survived the danger. All in all a very clever but very insidious strategy.
Wow! And there are those that doubt such processes lead to organisms' change.

publiusr
2005-Dec-30, 07:51 PM
I love how some of those tiny phages look like moon landers.

HenrikOlsen
2005-Dec-31, 03:48 AM
Well, first thing to dismiss is the idea that they are ancient organisms.
They are current organisms, quite as vibrantly adapted to the current world as we are. Otherwise they'd be dead aeons ago.
Second part of the problem is that sexual mixing of genes isn't needed if you either have low fidelity in reproduction and short geeration time, or mechanisms for exchanging genetic information between individuals(as bacteria has).