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Natural Science Forum / Biology / Microbiology / June 2007Completely frozen dormant states
1) What is different about bacteria as compared to multicellular organisms that enable them to be frozen through and through, while remaining alive in a dormant state? 2) Are there other microorganisms, or big organisms for that matter, that can be frozen all the way to the liquid inside the cells and still remain alive? Are there protozoans that can be frozen completely? 3) Can mammalian embryos be frozen all the way, as in hard rock cytoplasm, and still remain alive in a dormant state? I have read of embryos being frozen and stored in liquid nitrogen. Although this sounds cold enough, I am wondering if some of the liquid in these embryos remain liquid in a supercooled state. 4) Are the bacteria frozen in their vegetative state really frozen through, or is their cytoplasm in a supercooled state? There are bacteria that have been found frozen in ice cores in the Antarctic that have been revived after millions of years. Most of them were frozen in their vegetative state, although some were frozen as endospores. When the cells of a multicellular organism, animal or plant are frozen, the organism generally dies. Freezing an animal or a plant through and through is generally thought to kill the organism. The killing mechanism is hypothesized to be the drawing of water molecules out of the cell membrane, resulting in a cell membrane that falls apart. It was believe once that the cell membrane was torn apart by expanding ice crystals. It is now know that this is not true, as cell membranes have more than enough elasticity to accomodate the ice crystals. I wish to restrict the discussion to organisms that are frozen completely, without a drop of free flowing liquid in their bodies including the inside of their cells. Although some animals hibernate with their blood and lymph frozen, generally the liquid inside the cells remain liquid. There are species of frogs and fish like that. I am not talking about those animals. Furthermore, I know that bacterial endospores contain no free liquid. I am not including these guys either. They probably would be unaffected by freezing, since they don't contain liquid water. If any botanists know of a plant that can be frozen right down to their cytoplasm without permanent harm, please feel free to mention them. >1) What is different about bacteria as compared to multicellular >organisms that enable them to be frozen through and through, while >remaining alive in a dormant state? They are not multicellular. There is some death rate when you do it. The more complex the organism (ie, the more cells), the more likely it is that significant damage will occur. Statistics. It is also easier to control cooling rates and osmotic conditions with isolated cells. Do you know of any unicellular organism that cannot be frozen, or any type of cell from higher organisms that cannot be frozen? bob > >1) What is different about bacteria as compared to multicellular > >organisms that enable them to be frozen through and through, while [quoted text clipped - 5 lines] > (ie, the more cells), the more likely it is that significant damage > will occur. Statistics. You seem to be claiming that all isolated cells have pretty much the same chance of being revived, once they are frozen through and through. The high fatality rate in multicellular organisms comes about because in fact most individual cells die after being frozen, and the multicellular organism can't maintain itself as a unit if it looses too many individual cells. So if what you say is true, the following three things would be true also: 1) Most, in fact an exceedingly high fraction, of the vegetative bacteria that are frozen just plain die without any chance of revival. 2) Cells taken from multicellular organisms, if cultivated outside the body, can be frozen through and through and still retain a small chance of being revived. The chances of a human cell surviving the freezing process, outside the body, would be about the same as those of a bacterium surviving. 3) Plants that can be cloned from single cells (there are many) should be able to revive after freezing. I don't know if this is the case. It may be. Thanks for the suggestion, though. >> >1) What is different about bacteria as compared to multicellular >> >organisms that enable them to be frozen through and through, while [quoted text clipped - 26 lines] > I don't know if this is the case. It may be. Thanks for the >suggestion, though. I think you are largely on the right track with all of that. We have both simplified, in the interests of brevity and highlighting the main points. There certainly are differences among cells as to how well they survive freezing. But no matter, the big picture is right. (Bacteria survive relatively well, because they are small and have a rigid wall.) I am fairly sure that plant cells are indeed routinely frozen, but dont have any real info at hand. bob Lorentz You might be interested to research substances which prevent enhance 9 to a dgree) survival during the freezing of live cells or tissue. Dimethyl sulphoxide is one such substance. N10 > 1) What is different about bacteria as compared to multicellular > organisms that enable them to be frozen through and through, while [quoted text clipped - 35 lines] > be frozen right down to their cytoplasm without permanent harm, please > feel free to mention them. > You might be interested to research substances which prevent enhance 9 to a > dgree) survival during the freezing of live cells or tissue. Dimethyl > sulphoxide is one such substance. I wonder if dimethylsulphoxide can prevent freezer burn? After meat or vegetables are frozen, the material falls apart rather quickly. The mechanism has something to do with the dehydrolysis of the cell membrane (not mechanical lysing, as was once thought). Perhaps dimethyl sulphoxide prevents dehydrolysis. Thank you. I will look into it. "Lorentz" <drosen0000@yahoo.com> schrieb: > 2) Are there other microorganisms, or big organisms for that matter, > that can be frozen all the way to the liquid inside the cells and > still remain alive? I've heard that about water bears (tardigrades). Maybe some frogs as well, or lobsters: http://www.usatoday.com/tech/news/2004-03-14-lobsters-frozen_x.htm http://news.nationalgeographic.com/news/2005/03/0301_050301_woodfrog.html Regards, Joachim http://news.nationalgeographic.com/news/2005/03/0301_050301_woodfrog.... The frogs aren't completely frozen, according to this article. In fact, the article says that: "During this process, about two-thirds of the frog's body water freezes. The remainder, including water inside cells, remains liquid." I am not sure about the other organisms. My understanding so far is that animals that live through a frozen dormancy are only partially frozen. I have to look into the tardigrades, though. However, I have done some more googling on the topic, and with the help of everybodies hints, I found out a good part of my answer. Cells of all sorts of organisms, including mammals, can be revived after being frozen through and through. However, the survival rate of the cells is small. Most cells that are frozen solid are dead with no hope of survival. Although there are environmental factors known to improve the odds, as of yet no one has found a way to reliably (or even probably) revive an individual cell. The revival of frozen bacteria isn't that unusually in the biological world. Individual cells, even eukaryotes, can survive freezing. The bacteria don't really survive much better than eukaryotes. There are just a lot of them. |
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