rob@amadeus.TEK.COM (Dan Tilque) (03/09/88)
In a recent Science News (5 Mar 88) there is an article about the finding
of bacteria which live in underground aquafers. The following passage
caught my eye even though it was not the major story:
"Earlier experiments had shown that the carbon in water from this
particular aquifer was abnormally rich in carbon-13, a heavy
isotope of carbon. Chapelle's group found that the carbon
generated in the lab also contained high levels of carbon-13. he
suggested that the bacteria, which feed on organic molecules, have
a metabolism that selects this heavy isotope when producing carbon
dioxide."
I have never heard of any metabolic process which could distinguish
isotopes. Is this bacteria unique or are there other cases like it?
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Dan Tilque -- dant@mrloog.LA.TEK.COMdean@violet.berkeley.edu (Dean Pentcheff) (03/10/88)
In article <3230@zeus.TEK.COM> dant@mrloog.LA.TEK.COM (Dan Tilque) writes: > ... carbon-13. He > suggested that the bacteria, which feed on organic molecules, have > a metabolism that selects this heavy isotope when producing carbon > dioxide." >I have never heard of any metabolic process which could distinguish >isotopes. Is this bacteria unique or are there other cases like it? No, this is standard behavior. For example, when oceanographers use the isotope C-14 for measuring photosynthetic rate they apply a standard correction factor to compensate for differential uptake of C-14 and C-12 by phytoplankton. Can anyone shed some light on the chemical mechanisms that are involved? -Dean ----------------- Dean Pentcheff (dean@violet.berkeley.edu) ----------------- "A university is a place where people pay high prices for goods which they then proceed to leave on the counter when they go out of the store." Loren Eiseley
dd@beta.UUCP (Dan Davison) (03/10/88)
In article <3230@zeus.TEK.COM>, rob@amadeus.TEK.COM (Dan Tilque) writes: > In a recent Science News (5 Mar 88) there is an article about the finding > of bacteria which live in underground aquafers. The following passage > caught my eye even though it was not the major story: > > I have never heard of any metabolic process which could distinguish > isotopes. Is this bacteria unique or are there other cases like it? > Dan Tilque -- dant@mrloog.LA.TEK.COM This is quite common. For instance, drinking D20 (heavy water) can potentially be fatal because of the slowdown of enzymatic reactions. In my grad bio- chemistry courses we were told this several times, but no references were cited. The discrimination is based on the fact that isotopes of hydrogen (deuterium and tritium) carbon (13 and 14) oxygen (>16, if memory serves) and the common "substitutes" for small ions such as potassium and sodium have more protons (in the latter case) and more neutrons (in both cases). They are therefore more slowly picked up and reaction rates are slowed down. The slowdown is allegedly enough to impair essential enzymes (such as alcohol dehydrogenase) and all hydrolytic reactions in the body to the point where a person can die. I do recall reading some papers on the enzymatic rate differences between H2O and D2O; again, that was 11 years ago and I haven't kept up (read: strongly avoided) enzymology. dan -- dan davison/theoretical biology/t-10 ms k710/los alamos national laboratory los alamos, nm 875545/dd@lanl.gov (arpa)/dd@lanl.uucp(new)/..cmcl2!lanl!dd "I refuse to be intimidated by reality any more" "What is reality anyway? Nuthin' but a collective hunch!" --Jane Wagner,via Lily Tomlin