Monomer abundance distribution patterns as a universal biosignature: examples from terrestrial and digital life.
Organisms leave a distinctive chemical signature in their environment because they synthesize those molecules that maximize their fitness. As a result, the relative concentrations of related chemical monomers in life-bearing environmental samples reflect, in part, those compounds' adaptive utility. In contrast, rates of molecular synthesis in a lifeless environment are dictated by reaction kinetics and thermodynamics, so concentrations of related monomers in abiotic samples tend to exhibit specific patterns dominated by small, easily formed, low-formation-energy molecules. We contend that this distinction can serve as a universal biosignature: the measurement of chemical concentration ratios that belie formation kinetics or equilibrium thermodynamics indicates the likely presence of life. We explore the features of this biosignature as observed in amino acids and carboxylic acids, using published data from numerous studies of terrestrial sediments, abiotic (spark, UV, and high-energy proton) synthesis experiments, and meteorite bodies. We then compare these data to the results of experimental studies of an evolving digital life system. We observe the robust and repeatable evolution of an analogous biosignature in a digital lifeform, suggesting that evolutionary selection necessarily constrains organism composition and that the monomer abundance biosignature phenomenon is universal to evolved biosystems.
Digital Life Laboratory 136-93, California Institute of Technology, Pasadena, CA, USA.
Evan D
ED
Dorn
Kenneth H
KH
Nealson
Christoph
C
Adami
D000596:Amino Acids; D005075:Biological Evolution; D002264:Carboxylic Acids; D018559:Exobiology; D005118:Extraterrestrial Environment; D019369:Life
D000596:Amino Acids; D002264:Carboxylic Acids
Science. 2004 Jul 2;305(5680):84-6
15232105
Geochim Cosmochim Acta. 1994 Jun;58(11):2527-42
11541663
Orig Life Evol Biosph. 2002 Apr;32(2):143-63
12185673
Biochemistry. 1978 Sep 5;17(18):3759-68
698196
Orig Life Evol Biosph. 1999 Mar;29(2):153-66
10227201
Science. 1998 Sep 11;281(5383):1659-62
9733509
Nat Rev Genet. 2006 Feb;7(2):109-18
16418746
J Mol Evol. 1999 Jul;49(1):76-83
10368436
Appl Environ Microbiol. 1992 Dec;58(12):4026-31
16348828
Nature. 2002 Mar 28;416(6879):403-6
11919624
Nature. 1990 Nov 1;348(6296):47-9
11536470
Science. 1973 Nov 23;182(4114):781-90
17772148
J Mol Evol. 1981;17(5):265-72
7277509
PLoS Biol. 2004 Sep;2(9):E302
15367939
RNA. 1997 Jul;3(7):792-806
9214661
Nature. 2003 May 8;423(6936):139-44
12736677
Orig Life Evol Biosph. 1999 Mar;29(2):187-201
10391772
Proc Natl Acad Sci U S A. 2000 Apr 25;97(9):4463-8
10781045
Icarus. 1994;108:137-45
11539478
Appl Environ Microbiol. 1997 Apr;63(4):1476-82
16535574
In Silico Biol. 2003;3(4):471-82
14965346
Nature. 1965 Aug 7;207(997):568-70
5883628
Nature. 1997 Sep 18;389(6648):265-8
9305838
Nature. 1999 Aug 12;400(6745):661-4
10458160
Proc Natl Acad Sci U S A. 1965 Dec;54(6):1490-4
16591317
Astrobiology. 2009 May;9(4):335-43
19355818
Am Nat. 2001 May;157(5):465-87
18707256
Science. 2001 Sep 28;293(5539):2413-8
11577228
J Theor Biol. 2003 Jun 21;222(4):477-83
12781746
Icarus. 1991;94:354-67
11538091
Mol Biol Evol. 2002 Oct;19(10):1645-55
12270892
Nature. 1992 Feb 27;355(6363):772-3
1538757
Orig Life Evol Biosph. 2001 Feb-Apr;31(1-2):103-18
11296515
Adv Space Res. 1995 Mar;15(3):91-7
11539265
Science. 1953 May 15;117(3046):528-9
13056598
Proc Natl Acad Sci U S A. 2001 Jan 30;98(3):805-8
11158550
Science. 1959 Jul 31;130(3370):245-51
13668555
Artif Life. 2004 Spring;10(2):191-229
15107231
Geochim Cosmochim Acta. 1993 Oct;57(19):4713-23
11539581
Science. 1979 Oct 19;206(4416):335-7
17733683
Nature. 1970 Dec 5;228(5275):923-6
5482102
Astrobiology. 2009 Mar;9(2):241-9
19292603
Chem Phys Lipids. 1976 Mar;16(2):142-60
1269068
Icarus. 1986 Oct;68(1):176-84
11542046
Proc Natl Acad Sci U S A. 1972 Mar;69(3):765-8
4501592
Nature. 2001 Jul 19;412(6844):331-3
11460163