ISOTOPIC EVIDENCE FOR MICROBIAL SULFATE REDUCTION AND METHANOTROPHY DURING THE LATE ARCHEAN, WITWATERSRAND BASIN, SOUTH AFRICA

A. Erik Boice, Brett J. Tipple and Lisa M. Pratt,
Department of Geological Sciences, Indiana University,
1001 East 10th Street, Bloomington, IN 47405

ABSTRACT
Stable isotope ratios were determined for carbon (d13C) in organic matter and carbonate and for sulfur (d34S) in pyrite for a stratigraphic profile from a core containing 60 meters of the late Archean Booysens/Kimberly (B/K) Shale Formation and a portion of the underlying Krugersdorp Quarzite Formation. The studied core was collected at a subsurface depth of 1.8 km in Evander shaft #8 operated by Harmony Gold Inc. The Evander sub-basin is located on the northeast rim of the Witwatersrand Basin. Silty shales are the dominant lithofacies in the core but interbedded siltstones and several meters of underlying gray quartzites are present. Carbonate (Ccarb) and Organic carbon (Corg) contents in core samples range from <0.05 to 2.26 wt% and <0.05 to 0.42 wt%, respectively. Values of d13C for organic matter (d13Corg) and carbonate minerals (d13Ccarb) range from -42 to -35 and ­14.6 to -10.1, respectively. Distinct negative shifts in d13Corg values occur in laminated clay-rich intervals while positive shifts occur in carbonate­rich intervals. Values of d34S for Cr-reducible disulfide minerals (predominantly pyrite) range from -3.2 to +2.3. The most negative d34S values occur in the laminated intervals that contain the most negative d13Corg values. d13Ccarb values lower than -10 are inferred to reflect bicarbonate derived from methane. Microprobe imaging shows partial to complete chlorite replacement of original rhombohedral carbonate grains. The combined carbon and sulfur isotopic evidence suggest a thriving community of methanotrophic and sulfate-reducing bacteria in laminated, muddy sediment deposited during maximum marine flooding of the Witwatersrand Basin.

THE ROLE OF CLAY MATERIAL IN SHIELDING DNA AGAINST X-RAY RADIATION.

Ciaravella A., Barbera M., Micela G., Candia R., INAF-Osservatorio Astronomico, Palermo
Scappini F, ISMN-CNR, Bologna
Cecchi-Pestellini C., ISAC-CNR, Firenze
Franchi M., Gallori E., Universita', Firenze

ABSTRACT
X-ray experiments have been conducted on water solutions of free DNA and clay absorbed DNA. The level of damage has been analyzed using biological transformations. Results will be presented and discussed in the context ofthe origin of life.

ISOTOPIC EVIDENCE FOR MICROBIAL SULFATE REDUCTION AND METHANOTROPHY DURING THE LATE ARCHEAN, WITWATERSRAND BASIN, SOUTH AFRICA

A. Erik Boice, Brett J. Tipple and Lisa M. Pratt,
Department of Geological Sciences, Indiana University,
1001 East 10th Street, Bloomington, IN 47405

ABSTRACT
Stable isotope ratios were determined for carbon (d13C) in organic matter and carbonate and for sulfur (d34S) in pyrite for a stratigraphic profile from a core containing 60 meters of the late Archean Booysens/Kimberly (B/K) Shale Formation and a portion of the underlying Krugersdorp Quarzite Formation. The studied core was collected at a subsurface depth of 1.8 km in Evander shaft #8 operated by Harmony Gold Inc. The Evander sub-basin is located on the northeast rim of the Witwatersrand Basin. Silty shales are the dominant lithofacies in the core but interbedded siltstones and several meters of underlying gray quartzites are present. Carbonate (Ccarb) and Organic carbon (Corg) contents in core samples range from <0.05 to 2.26 wt% and <0.05 to 0.42 wt%, respectively. Values of d13C for organic matter (d13Corg) and carbonate minerals (d13Ccarb) range from -42 to -35 and ­14.6 to -10.1, respectively. Distinct negative shifts in d13Corg values occur in laminated clay-rich intervals while positive shifts occur in carbonate­rich intervals. Values of d34S for Cr-reducible disulfide minerals (predominantly pyrite) range from -3.2 to +2.3. The most negative d34S values occur in the laminated intervals that contain the most negative d13Corg values. d13Ccarb values lower than -10 are inferred to reflect bicarbonate derived from methane. Microprobe imaging shows partial to complete chlorite replacement of original rhombohedral carbonate grains. The combined carbon and sulfur isotopic evidence suggest a thriving community of methanotrophic and sulfate-reducing bacteria in laminated, muddy sediment deposited during maximum marine flooding of the Witwatersrand Basin.

PREBIOTIC CHIRALITY TRANSFER FROM EXTRATERRESTRIAL Ca-TETRASUBSTITUTED a-AMINO ACIDS TO PROTEIN AMINO ACIDS

Marco Crisma a, Alessandro Moretto a, Fernando Formaggio a, Claudio Toniolo a, Bernard Kaptein b, Quirinus B. Broxterman b
a. Institute of Biomolecular Chemistry, CNR, Department of Organic Chemistry, University of Padova, Via Marzolo 1, 35131 Padova, Italy
b. DSM Research, Life Sciences, Advanced Synthesis and Catalysis, P.O. Box 18, 6160 MD Geleen, The Netherlands

ABSTRACT
A recent analysis of the amino acid content of the Murchison meteorite, fallen over Australia in
1969, revealed the presence of four chiral Ca-tetrasubstituted a-amino acids, namely isovaline (Iva), Ca-methyl norvaline (Me)Nva], Ca-methyl isoleucine [(aMe)Ile], and Ca-methyl alloisoleucine [(aMe)aIle] with a small, but significant, L(S) enantiomeric excess (up to 9%). Related findings in the protein amino acid fraction were considered of no significance in view of a possible terrestrial contamination. On the contrary, this possibility is quite remote for these Ca-tetrasubstituted a-amino acids, the occurrence of which on terrestrial compounds was reported only for Iva. Moreover, Ca-tetrasubstitution protects amino acids against racemization. These results suggest that Ca-tetrasubstituted a-amino acids of extraterrestrial origin could have been the homochirality seeds for life in our planet. However, this hypothesis implies that the enantiomeric excesses would have been somehow transferred from Ca-tetrasubstituted a-amino acids to protein amino acids. In this connection, we have planned a detailed study aimed at determining if and how derivatives or peptides based on Ca-tetrasubstituted a-amino acids could have reacted with protein amino acids and favoured one of their enantiomers over the other.
In this Communication we report on the synthesis and conformational studies of the Iva, (aMe)Nva, and (aMe)Val, homochiral homopeptides. These Ca-tetrasubstituted residues bear either a linear [Iva and (aMe)Nva] or a b-branched [(aMe)Val] side chain. Solution (FT-IR absorption, CD, 1H NMR) and crystal-state (X-ray diffraction) conformational analyses indicate that these homo-peptides tend to fold in b-turn and 310-helical structures (depending upon main-chain length).
Homochiral homopeptide sequences from Iva, (aMe)Nva, and (aMe)Val, activated as Ac-(AA)n-OXL [Ac, acetyl; OXL, 5(4H)-oxazolone; n = 2-8] were allowed to react with a racemic mixture of a protein amino acid, H-D,L-Val-OMe. The competitive formation of the resulting diastereomers was quantified. The effects of temperature and reaction time were also examined. We have found variable amounts of diastereomeric excesses [up to 58% for the longest (aMe)Val homo-peptides]. Our results clearly show that the incorporation of the heterochiral protein amino acid is increasingly preferred with: (i) increasing difference in size between the two side chains of the Ca-tetrasubstituted a-amino acid, and (ii) increasing main chain length of the peptide oxazolone, which in turn favours the onset of stable secondary structure elements.
Thus, it is reasonable to conceive a racemic primordial soup of protein amino acids which in the long run is converted to a soup with a more and more abundant L enantiomeric excess due to the depletion of the other isomer by the Ca-tetrasubstituted oligomers. At this stage, various possible mechanisms of peptide bond formation may have further amplified this phenomenon, eventually producing the first functional proteins.

SOME STATISTICAL ASPECTS RELATED TO THE STUDY OF TREELINES
IN PICO DE ORIZABA

LUIS CRUZ-KURI
Instituto de Ciencias Básicas. Universidad Veracruzana
Carr. Xalapa-Ver., Km. 3.5, Las Trancas, Xalapa, Ver., MEXICO

CHRISTOPHER P. MCKAY
NASA-Ames Research Center
Moffett Field, CA 94035, USA

RAFAEL NAVARRO-GONZALEZ
Laboratorio de Química de Plasmas y Estudios Planetarios
Instituto de Ciencias Nucleares, UNAM, Circuito Exterior,
Ciudad Universitaria, Apartado Postal 70-543, MEXICO

ABSTRACT
Pico de Orizaba, Mexico's highest peak, is the fourth highest volcano in the Northern Hemisphere, it has a glacier on the north face and it has the highest tree line in the world (> 4200 m). Pico de Orizaba (19º N) has environmental conditions that probably could have occurred in ancient Mars. Therefore, related to the survival of ecosystems in extreme environments, with possible applications to life on Mars, we started to monitor the mountain in several sites, above, below and within the tree line of the domineering species P. hartweggi. Since March of 1999 we have been studying physical and chemical properties of soil as well as those of microbial activity. Of particular interest is to study tree lines at thermal gradients, for which, soil temperatures at various depths, as well as external temperatures, tree-trunk temperatures and other measurements such as air humidity, etc., are being recorded hourly since then, in an ongoing process to continue for several years. The present is a report of some of the continuing statistical analysis performed on the data, in an effort to detect spatial and temporary patterns.

THE HUNT FOR "BIOLOGICALLY ACTIVE" BIOPOLYMERS:
SPONTANEOUS FOLDING OF RANDOM RNA OLIGOMERS

Marco Franchi*, Davide De Lucrezia§, Cristiano Chiarabelli§, PierLuigi Luisi§, Enzo Gallori *
Department of Animal Biology and Genetics, University of Florence - Florence (Italy)
§ Institute of Polymers, Swiss Federal Institute of Technology, ETH Zurich - Zurich(Switzerland)
marco.franchi@dbag.unifi.it

ABSTRACT
The probability of occurrence of biopolymers with a well defined steric conformation is one of the central questions concerning the origin of life on Earth. In fact, whatever was the nature of primitive "biological" polymers, their chemical activity and specialized functions depended on the acquisition of durable and stable secondary and tertiary structures.
Because of the possible pivotal role of RNA in the evolution of life on Earth, we have studied the folding properties of RNA oligonucleotides with random sequences. We developed a plasmid library for in vitro transcription of random RNAs, 150 nucleotides long. The resulting RNA molecules were tested for their sensitivity to S1 nuclease at different temperatures ranging from 37 to 60°C in order to evaluate their ability to form internal double helices and to acquire secondary and tertiary structures.
Preliminary results of these studies suggest that most (~70%) random oligomers acquired a secondary structure stable up to 50°C but lost their folding at higher temperatures. Interestingly, a small percentage (~9%) of the oligomers were very stable even at relatively high temperatures (55-60°C), suggesting a possible role of these thermostable steric structures in the hot environments of the primeval Earth.

CHARACTERIZATION OF EXTRASOLAR PLANET CANDIDATES

Jose Gallardo and Dante Minniti.
Departamento de Astronomia y Astrofisica,
Facultad de Fisica,
P. Universidad Catolica de Chile.
Av. Vicuna Mackenna 4860.
Santiago Chile.

ABSTRACT
We report photometric classifications of 62 stars where OGLE found transits in order to classify the most promising candidates to have extrasolar planets. We use the difference of stellar flux dF, delivered by OGLE data, and the stellar radius R_star, derived from the spectral type found by our IR photometry, to determine the companion's radius R_planet. Besides, we present a stellar environment study to verify properties of these candidates like distance, metallicity and stellar populations. Follow up spectroscopic observations will enable us to obtain their masses and to discriminate among white and brown dwarf and giant planets.

PROPOSING A UNITED NATIONS SECRETARY GENERAL SETI INTERNATIONAL ADVISORY BOARD

Genta G.
Department of Mechanics, Politecnico di Torino,
C. Duca degli Abruzzi 24, 10129, Torino, Italy
genta@polito.it / fax: ++39 011 564 6999

Picco G.
Advisor to the United Nations Secretary General at the Level of Under-secretary ­ New York ­ USA

Galeotti P.
Department of Physics, University of Torino, Torino, Italy

Noventa D.
Non Govermental Peace Strategies Project ­ Geneve ­ Switzerland

ABSTRACT
SETI's Post-Detection Protocols have recently identified a novel means of interaction between SETI and the United Nations.

Through this proposal, the Italian SETI Study Center hopes to realize the following:
1) The preparation of an ad hoc study on SETI by an international panel of experts of various disciplines for the United Nations, addressed to the Secretary General;
2) The identification and formalization of the role of the United Nations Secretary General and his International Advisory Board in the functions of decision-making, management of/communication with the international media system vis-à-vis the possible detection of artificial signals of proven extraterrestrial origin.

SETI's work program includes the following:
1. TARGET: To create an effective, temporary board for the United Nations Secretary General, with information and situation support capabilities per SETI.

2. ACTIVITY:
To prepare a state of the art document on SETI, covering all possible aspects (including scientific, philosophical, social, media, intelligence and security aspects);
To update this document on a bi-annual basis;
To act as the United Nations Secretary General's situation support staff in instances of extraterrestrial signal detection and, in particular, to assist him in the decision-making process upon successful detection of such signals.
The board will, in effect, develop, and make official, the contents of the SETI Post-Detection Protocols, expanding its activity to managing communication of any signal detection to the international media system.

3. COMPOSITION of the International Advisory Board: experts with internationally recognized credibility and competence in the following areas:
Astrophysics and Cosmology
Bioastronomy
Radioastronomy
Astronautics and Space Exploration
Mathematics and Informatics
International Space Law

Social Sciences
International Relationships
Philosophy of Science
Religious Aspects
Mass Media
Intelligence and Military Aspects

4. AGENDA: The International Advisory Board expects to meet every two years to update and follow-up on current needs.

FUNDING: The funds required to create, maintain and support the activities of the international advisory board will not be provided by the United Nations but rather will be raised in the private sector, through various foundations, companies and associations with adequate international standing.

EFFECTS OF NON-CARBONACEOUS METEORITIC EXTRACTS ON THE GERMINATION, GROWTH AND CHLOROPHYLL CONTENT OF EDIBLE PLANTS

VICENTE MARCANO1, PAULA MATHEUS1, CESYEN CEDEÑO2, NELSON FALCON3 AND ERNESTO PALACIOS-PRÜ1,4
1 Evolutionary Biology and Chemistry Laboratory, Electron Microscopy Center, University of the Andes, P. O. Box 163, Mérida, Venezuela.
2 Crystalography Laboratory, Faculty of Sciences, University of the Andes, Mérida, Venezuela.
3 Department of Physics, Faculty of Science and Technology, University of Carabobo, Valencia, Venezuela.
4 International Institute of Advanced Studies, Simón Bolívar University, Caracas, Venezuela.

ABSTRACT
Several scenarios have been conceived in order to establish eventually human settlements in space stations or on planetary bodies or satellites, using indigenous space resources. Nutrients for plant cultures in space could be obtained mining asteroids or collecting micrometeorites. Carbonaceous and non-carbonaceous meteorites contain nutrients needed for biological activity. Experiments utilizing non-carbonaceous material are not known. Selection of edible plants by human settlements in the space should take in account their capacity to compensate the effects that the unfiltered solar radiation, galactic radiation and negligible gravity would produce on humans. We focus our investigation on the effects that non-carbonaceous meteoritic extracts could has on the germination and growth of these plants and the ability of non-carbonaceous meteoritic resource to serve as nutrient source for young plants having edible uses. Selected plants were two dicotyledons (Lycopersicon esculentum and Daucus carota) and one monocotyledon (Zea mays). Solution cultures were developed using seeds and seed-embryos. Meteoritic powder was obtained from the Vigirima mesosiderite, which was analyzed by X-ray diffraction and atomic absorption spectrometry (AAS).
Results showed that extracts having variable concentrations of meteoritic matter produced an earlier germination in some plant species but the increase of the concentrations produced a decreased germination. However, total germination rate was higher in the presence of meteoritic extracts than in the presence of blanks in the all species. A high metabolic yield in the protein synthesis was seen in dicotyledons utilizing Type-A and B extracts having concentrations of 4.16-8.33 x 103 mg l-1. Phaeophytinization index and chlorophyll a/b ratio, suggested an negative effect of the heavy metals or acidic ions over the photosynthetic activity when extracts having high meteoritic concentrations were utilized. However, a higher chlorophyll (a) production in comparison to that of chlorophyll (b) was seen in extracts (Type-A and B) having low concentrations of meteoritic matter. On the other hand, Z. mays seed-embryos growing in extracts (Type-D) having 3.53 x 104 mg l-1 of meteoritic matter showed a protein production (9.81 x 10-2 mg protein mg wet wt.-1) higher than that observed in seed-embryos coming from extracts having lower concentrations. However, in Murashige medium, the seed-embryos exhibited a enhanced growth and a relatively higher protein production (10.3 x 10-2 mg protein mg wet wt.-1). Further, chlorophyll (a+b) synthesis was higher in Murashige medium than in meteoritic extracts but chlorophyll a/b ratio was < 1 in the all extracts and blanks.
Our results suggest the usefulness of the non-carbonaceous meteoritic resource as a complementary soil component or fertilizers for culture of edible plants in space human settlements and mainly for the production of young plants due to the positive metabolic effects on the chlorophyll synthesis, mitochondrial metabolism and cellular division caused by PO43-, Fe2+, Cu2+ and Ca2+ ions. Earlier germination responses obtained in the experiments showed the possibilities to utilize in space germination chambers having wet substrates containing meteoritic-powder solutions to obtain a higher number of seedling in a minimum degree of time. Utilization of seed-embryos could be considered an efficient alternative to develop in space stations or human settlements on Mars or Moon. These results reveal also the biological potential of the non-carbonaceous meteoritic matter for the growth of organisms in the early Earth, Mars, and probably in other planetary bodies beyond our Solar system.

HOW ADVANCED IS ETI?
ARE SCIENTIFIC AND TECHNOLOGICAL PROGRESS LIKELY TO BE ENDLESS?

PAOLO MUSSO
Pontifical University of the Holy Cross of Roma
V. Montevideo 2A/-6, 16129 Genova (GE) - Italy
musso@nous.unige.it

ABSTRACT
One of the most widespread commonplace in discussing about the possible existence of other technological civilizations is that they should be very more advanced than ours.
At a cosmic scale, indeed, mankind was born just yesterday. So, it is very likely that almost any other civilization we could ever detect will be much older than ours. But does it necessarily imply that it should be also much more advanced?
Since we are just at the dawn of our technological age, but nonetheless in only four centuries have achieved such a great progress, a positive answer may seem to be obvious. But, in fact, this implies the assumption that both scientific and technological progress are endless processes, which is not obvious at all. In this paper this point will be discussed, with the help of two diagrams analyzing the only example of scientific and technological progress we know, that is the one of our own terrestrial society.

PREBIOTIC POLYMERIZATION OF AMINOACIDS. A MARKOV CHAIN APPROACH

S. Ramos-Bernal1, G Mosqueira2 and A. Negron-Mendoza1
1Instituto de Ciencias Nucleares, UNAM, A.P. 70-453, Mexico, D.F 04510
2Dirección General de Divulgación de la Ciencia, UNAM. Cd. Universitaria, A.P. 70-487, 04510
México D.F., México.

ABSTRACT
The principle of self-ordering of amino acids, as related to the origin of life research, has been extensively studied and interpreted by S. Fox and collaborators (Fox and Dose, 1977). Such principle establishes that the reactivity between different amino acids is not even.
The relevance of the self-ordering principle to the emergence to minimal self-reproducible chemical systems has been already analyzed in probabilistic terms. These considerations concluded that the polymerization phenomena associated to the origin of life had to be strongly biased. Otherwise the probability of nucleation of a "minimum life would be excluded (Mosquiera, 1988).
In the present work, we study the Markov chain approach for the oligomerization of amino acids based on the physicochemical and volume differences among reacting amino acids. The results found may be of importance as it makes more accessible the replication of minimal chemical machinery compatible with life processes.

References
Fox, S. and Dose, K. (1977), Molecular evolution and the origin of life, Marcel Dekker, Inc., New Yor.

Mosqueira, G. (1988), Origins of Life and Evol. Biosphere, 18, 143-156.

ANALYSIS OF THE WORKS OF THE GERMAN NATURALIST
ERNST HAECKEL (1834-1919)
ON THE ORIGIN OF LIFE

Florence Raulin-Cerceau
Centre Alexandre Koyré
(CNRS-EHESS-MNHN-UMR 8560)
Muséum national d'Histoire naturelle
57 rue Cuvier - F-75005 Paris
e-mail : raulin@mnhn.fr

ABSTRACT
During the second part of the nineteenth century, the problem of the emergence of living beings was much debated. The theory of natural selection (The Origin of Species, Darwin, 1859) led to wonder about the beginning of life, while the theory of spontaneous generation for microorganisms still persisted. However, Pasteur's series of experiments (Mémoire sur les corpuscules organisés qui existent dans l'atmosphère, Annales des Sciences Naturelles, 1861) proved that preexistent germs in the atmosphere were the response to the question of spontaneous generation and then, that life was always antecedent to life. Despite this demonstration, however, many scientists adopted the evolutionist point of view while accepting that a primitive life could arise from continual spontaneous generation. Therefore, because of this link between evolution and spontaneous generation (at some period or other of the Earth's history) it appears that, between 1860 and the end of the nineteenth century, the question of the origin of life was rather complex.
In Germany, the materialist philosophers and the naturalist Ernst Haeckel (1834-1919) were enthusiastic about Darwin's theory precisely because one type of spontaneous generation (abiogenesis: organic matter- in terms of belonging to living organisms- emerging from inorganic matter) and the unification of the organic and inorganic world into " one great fundamental conception "were implied (Farley, 1977). Acceptance of abiogenesis became naturally a cornerstone of materialist philosophy. In several of his numerous writings, Haeckel took an active interest in the topic of the origin of life (a primeval abiogenesis, in a distant past). Haeckel's views on the origin of life mainly came from his philosophy (monism) and his concept about the nature of the simplest organisms, made of one single substance, named protoplasm.
In this work, we propose to analyze more precisely the following Haeckel's writings:
- Generelle Morphologie der Organismen (General Morphology of Organisms) (1866)
- Natürliche Schöpfungsgeschichte (Natural History of Creation) (1868)
- Die Welträthsel (The Riddles of the Universe) (1899)
- Die Lebenswunder (The Wonders of Life) (1904)

Reference:
- Farley, J. (1977) Spontaneous Generation Controversy from Descartes to Oparin, The John Hopkins University Press, Baltimore and London.

HORIZONTAL GENE TRANSFER IN THE EVOLUTION OF NITROGEN FIXATION

Janet Siefert, PhD
Rice University
Department of Statistics MS 138
PO Box 1892
Houston, Texas 77251-1892, USA
Office 713-348-3891
Fax 713-348-5476
Web site: http://www.stat.rice.edu/%7Emathbio/siefert.html

ABSTRACT
Whole genome sequences for nearly twenty nitrogen-fixing prokaryotes are now available, and we have analyzed each of these organisms for presence of one or more nif (nitrogenase-gene encoding) operons and conserved synteny. Additionally, we have used standard tools of sequence analysis to evaluate the evolutionary history of every characterized gene found in these nif operons and observe that the core genes segregate phylogenetically into the known metal-binding classes (iron-, vanadium-, or molybdenum-containing) of nitrogenase. We have also used molecular phylogenetic techniques to analyze a fourth group of yet-uncharacterized nitrogenase homologs, found in archaea and in a limited number of phototrophic bacteria, that appear to be ancestral to nitrogenase genes and to essential genetic components of chlorophyll and bacteriochlorophyll biosynthesis found in all known phototrophs. This fourth group of nitrogenase homologs may function as an electron sink or possibly as a non-specific detoxyase or reductase, and is likely a relic of some ancient metabolic trait. Here we trace the early origins of nitrogenase genes and the subsequent horizontal gene transfer events that have resulted in the current distribution of prokaryotic nitrogen fixation.

PALAEOBIOLOGY AND BIOSEDIMENTOLOGY OF THE STROMATOLITIC BUXA DOLOMITE, RANJIT WINDOW, SIKKIM, NE LESSER HIMALAYA, INDIA

Vinod Chandra Tewari *+
*Wadia Institute of Himalayan Geology, India
+The Abdus Salam ICTP, Italy

ABSTRACT
The Mesoproterozoic (Riphean) stromatolite taxa are recorded from the Buxa Dolomite of the Ranjit Window, Sikkim Lesser Himalaya India. The Riphean characteristic taxa are Omachtenia, Colonnella columnaris, Kussiella kussiensis, Conophyton, cylindricus, C. garganicum, Rahaella elongata Tewari, Jacutophyton, Baicalia nova, Tungussia, Jurusania, Inzeria, Gymnosolen, Minjaria, Stratifera and Gongylina. The Neoproterozoic-Terminal Proterozoic (Vendian) stromatolite assemblage Paniscollenia, Aldania, Tungussia, Linella, Colleniella, Linocollenia, Boxonia linked Conophyton, Conistratifera, microstromatolites, Stratifera, Irregularia, Nucleella, digitate stromatolites and oncolites are well developed in the Buxa Dolomite, Ranjit Window, Sikkim and its equivalents (Menga Limestone/Dedza Limestone/Chillipam Limestone) in the adjoining Arunachal and Bhutan Lesser Himalaya. The Mesoproterozoic to Terminal Proterozoic stromatolite diversification has been recorded for the first time from the Buxa Dolomite of the Sikkim Lesser Himalaya, India. The Palaeobiological and biosedimentological significance of the stromatolites in the Buxa Dolomite has been discussed.

CHEMICAL ABUNDANCES OF COMETARY METEOROIDS FROM METEOR SPECTROSCOPY: IMPLICATIONS TO THE EARTH ENRICHMENT

Josep Mª Trigo-Rodríguez 1, Jordi Llorca 2,3 and Joan Oró 4
1 Departament Ciències Experimentals, Universitat Jaume I.
2 Institut d'Estudis Espacials de Catalunya.
3 Departament Química Inorgànica, Universitat de Barcelona.
4 Fundació Joan Oró

ABSTRACT
The overabundance of comets and chondritic bodies during the first stages of the primeval Solar System produced a constant rain of material over our planet, that could have direct implications to the origin of life in it (Oró 1961). Nowadays we know that cometary matter in these encounters suffers important alteration processes, the collision of comet Shoemaker-Levy 9 with Jupiter provided us interesting information about these violent processes. Probably the most important source of Earth enrichment in volatile and organic compounds has been therefore the constant entry of meteoroids from dense meteoroid streams produced during hard fragmentation processes of their parent bodies. At present, meteor storms are unusual but we believe that fragmentation of comets and chondritic bodies produced dense cometary streams during the first stages of the Solar System. Important evidences have been obtained in the last decade studying young protoplanetary disks. The observation of fast spectral changes in their respective central stars has induced the development of the so-called model of Falling Evaporating Bodies. Only a turbulent stage where minor bodies are in constant fragmentation can be able to explain some of the most important characteristics of these young planetary systems.
Actually, meteor storms are usually produced by relatively long period comets with high inclination orbits that produce violent encounters of the meteoroids with the terrestrial atmosphere. In the past, it is likely that meteor storms were produced from orbits of low inclination and eccentricity, typical of ice and chondritic minor bodies formed in the inner Solar System or perturbed from outer regions due to the high matter density of bodies in the young solar system. An important consequence is that the low geocentric velocities allowed this matter to arrive to the Earth without be completely degraded as occurs for high-velocity meteoroids. We have analysed the temperature and volatilisation processes from the study of spectra of fireballs produced by cometary meteoroids. From these spectra we have derived the relative abundance of Na, Mg, Ca, Si, Ti, Cr, Mn, Fe, Co and Ni in the parent meteoroids by averaging the composition of the radiating gas along their respective fireball paths produced during atmospheric entry. Data reduction and relative chemical abundance were obtained following Borovicka (1993) procedure. According to their orbital elements these meteoroids were principally of cometary origin. We have found important chemical differences between these cometary meteoroids and the 1P/Halley dust analysed in situ by Giotto spacecraft (Jessberger et al., 1988). Between these differences is important to note that the deduced abundances of Si-Mg-Fe are in accordance to the hierarchical dust accretion model developed by Rietmeijer (2002). Moreover, other interesting result is the larger sodium abundance compared to the expected for IDPs and chondritic meteorites. It shows that 1P/Halley can not be used as type sample of cometary dust, suggesting important differences between comets, as was already pointed out by Greenberg (2000).
Finally, we focus our attention into the direct implications that this cometary matter, reaching the atmosphere as meteoroid streams, had in the primeval enrichment of exogenous material into the Earth. Our results support the idea that there are, in fact, substantial chemical differences among comets, probably related with the origin of the different families as was proposed by Delsemme (2000).

REFERENCES

Borovicka J. (1993) "A fireball spectrum analysis", Astronomy & Astrophysics 279, 627-645.

Delsemme A.H. (2000) "1999 Kuiper Prize Lecture: Cometary Origin of the Biosphere", Icarus 146, 313-325.

Greenberg J.M. (2000) "From comets to meteors", Earth, Moon and Planets 82-83, 313-324.

Jessberger E.K., J. Kissel & J. Rahe (1988b) "The composition of comets", in Origin and Evolution of Planetary and Satellite atmospheres, 167-191, Univ. of Arizona Press, Tucson, EUA.

Kissel J. y F.R. Krueger (1987), "The organic component in dust from comet Halley as measured by the PUMA mass spectrometer on board Vega 1", Nature 326, 755-760.

Oró J. (1961) "Comets and the formation of biochemical compounds on the primitive Earth", Nature 190, 389-390.

Rietmeijer F. J. M., (2002) "The Earliest Chemical Dust Evolution in the Solar Nebula", Chemie der Erde 62-1, 1-45.

CONSERVED OLIGOPEPTIDES IN RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE LARGE CHAINS : AN EVOLUTIONARY PERSPECTIVE.

P.B.Vidyasagar 1, Pratip Shil 2 and Sarah Thomas 3
1 Professor, Biophysics Section, Department of Physics, University of Pune,
2 Research student, Biophysics Section, Department of Physics, University of Pune,
3 Lecturer, Bioinformatics Center, University of Pune.

Ribulose­1,5-bisphosphate carboxylase/Oxygenase (RuBisCO) is the largest multimeric protein on the Earth and it catalyses the first step in the CO2 assimilation in photosynthesis. Analysis of RuBisCO large chain sequences from different species spanning from lower to higher plants (viz. Archea, Bacteria, Alga and Higher plants) have been carried out using Bioinformatics techniques viz multiple sequence alignment (CLUSTALW) and secondary structure prediction tools. Secondary structure prediction from the Predict Protein package show the occurrence of conserved oligo-peptides in different secondary structures in different groups of sequences. The study also reveals the occurrence of conserved oligopeptides specially '-KDDEN-" and '-SGGIH-' in almost all the sequences. The advanced analysis and comparison of these sequences with those from tobacco and spinach (with known 3D structures) reveal the existence of close interaction of these oligopeptides and other conserved amino acids. The conservation of the oligopeptides indicates their probable decisive role in the active site configuration.
The present study reveals that in the evolutionary pathway the RuBisCO large chain sequences have stabilized in higher plants after initial variations in the lower plants.
The present study reveals some of the aspects related to the structural changes during evolution of plants.

INTERSTELLAR DUST AS A TRACER OF ENVIRONMENTS FAVOURABLE TO PLANET FORMATION: EVIDENCE FOR THE EXISTENCE OF A METALLICITY THRESHOLD.

Giovanni Vladilo
Osservatorio Astronomico di Trieste
Istituto Nazionale di Astrofisica

ABSTRACT:
Dust occupies a central position along the astrophysical route that, starting from the stellar production of chemical elements, leads to the formation of molecules and pre-biotic material in the interstellar space and to the building up of proto-planetary disks around stars. Tracing the formation and evolution of dust in galaxies is therefore an important step in the quest for environments capable of developing life. I report here the results of a study of the dust content in primordial galaxies observed by means of absorption spectroscopy of background quasars. This study provides evidence for the early build-up of dust, consequent to the stellar production of metals, in primordial galaxies seen between ~8 and ~12 billion years before the present. The analysis of the data indicates a severe deficiency of the dust-to-metal ratio in the very early stages of metal production. However, when the metallicity level increases above ~10% of the solar value, the dust content approaches the values typical of the nearby interstellar medium, where planets and life managed to emerge. This suggests that galaxies with metallicities >10% of the solar one may have a dust content sufficient to develop pre-biotic material and planets.

THE ELECTROCHEMICAL CO2 REDUCTION TO FORMATE IN HYDROTHERMAL SULFIDE ORE DEPOSIT AS A NOVEL ABIOTIC SOURCE OF ORGANIC MATTER (A HYPOTHESIS AND THE LABORATORY MODEL).

M. G. Vladimirov1 *, Yu. F. Ryzhkov 2, V. A. Alekseev 2, V. A. Bogdanovskaya 3,
V. A. Otroshchenko 1, and M. S. Kritsky 11 A.N.Bach Institute of Biochemistry, Russian Academy of Sciences (RAS), Moscow; 2 The Russian Federation State Research Center "Troitsk Institute for Innovation and Fusion Research", Troitsk, Moscow Region; 3A.N.Frumkin Institute of Electrochemistry, RAS, Moscow; Russia.
*<mgv@inbi.ras.ru>

ABSTRACT
A wide spectrum of electrode potentials of minerals that compose sulfide ores to enable the latter, when in contact with hydrothermal solutions, to form galvanic circuits with cathode potentials up to several volts sufficient for electrochemical reduction of CO2.
Before our study pyrite was not investigated as cathode material, hence the combination of semiconductor properties with the low adsorption activity and a presence of traces of transient metals pointed to this mineral as to a probably good cathode material. The experiments performed demonstrated the increase of cathode current on rotating pyrite electrode in a range of potentials more negative than ­800 mV in presence of CO2 and revealed the dependence of this current from the CO2 diffusion rate, temperature and ionic composition of aqueous phase.
The numerous studies of the CO2 reduction on cathode materials other than pyrite have formed the notion on the chemistry of this process. According to it, the reduction process involves an electron tunneling from cathode surface to a CO2 molecule with the production of an active particle, the radical-ion __2- and the further reduction of this radical to formate (and, under certain conditions, to more complex molecules).
To verify our hypothesis on the CO2 electrochemical reduction on pyrite in modeling experiment, the installation was constructed which consisted of a fluorocarbon electrochemical cell with two separated electrode chambers installed into a high-pressure autoclave permitting a continuous CO2 flow (50 atm, 10 ml_min­1) through cathode chamber. The cathode (7 cm2) was manufactured of a hydrothermal pyrite monocrystal and anode was a platinum plate. The cell's electrodes were connected with a programmed potentiostate and the recording unit. The cell was filled with 0.1 M KHCO3 electrolyte, and the CO2-saturated solution was subjected to electrolysis (24 hrs, room temperature).
Starting with a cathode potential about 800 mV (vs. saturated Ag|AgCl r.e.), the accumulation of formate in electrolyte was observed by a color reaction with chromotropic acid. No formate production was registered under normal atmospheric pressure and in the absence of imposed cathode potential. Neither in experiments, nor in control formaldehyde was found. The yield of formate demonstrated an exponential growth as a function of cathode potential value at least up to 1200 mV. The maximal faradaic efficiency of formate synthesis (0.12%) was observed at 1000 mV. The results point to geoelectrochemical systems capable to the CO2 cathode reduction as a novel source of abiogenic organics.