Molecular Origins of Life, Munich 2021

25.08.2021, 10:45 → 27.08.2021, 18:45 Europe/Berlin

Online

! The conference  details are emailed on August 23rd if you have not received the details please contact us (please make sure you checked spam/junk folders)!

Note: The recording of the talks (if the speaker allowed us) will be shared with the registered attendees after the conference.

The Molecular Origins of Life, Munich conference addresses one of the most fundamental questions of science: How could life originate? With 24 talks by renown scientists accompanied by Q&A, meet the speaker and poster sessions, this international conference brings together scientists from a wide range of disciplines, namely: astrophysics, biochemistry, biophysics, chemistry, geosciences and theoretical physics. Only the combined effort from various disciplines can be successful in retracing the origins of life under experimental conditions and pave the way towards answering some of the most pertinent questions: What were the conditions on early Earth? Which chemicals could serve as precursors for the synthesis of living systems on Earth and/or on other planets? How did the very first genetic material in life forms develop? How could Darwinian evolution emerge? What were the first metabolic pathways? The conference's aim is to represent and to discuss the state of the art in the Origin of Life field. 

The Molecular Origins of Life, Munich 2021 is sponsored by DFG funded Collaborative Research Center 235 Emergence of Life and the attendance to the event is free of charge.

---

MOM2021 Poster

Mittwoch, 25. August

10:45 Welcome Note & Info

Session I

1 On the origins of chemical evolution

The evolution of life from the prebiotic environment required a gradual process of chemical evolution towards greater molecular complexity. Elaborate prebiotically-relevant synthetic routes to the building blocks of life have been established. However, it is still unclear how functional chemical systems evolved with direction using only the interaction between inherent molecular chemical reactivity and the abiotic environment. In this talk, I will discuss how complex systems of chemical reactions exhibit well-defined self-organisation in response to varying environmental conditions. This self-organisation allows the compositional complexity of the reaction products to be controlled as a function of factors such as feedstock and catalyst availability. We observed how Breslow’s cycle contributes to the reaction composition by feeding C2 building blocks into the network, alongside reaction pathways dominated by formaldehyde-driven chain growth. The emergence of organised systems of chemical reactions in response to changes in the environment offers a potential mechanism for a chemical evolution process that bridges the gap between prebiotic chemical building blocks and the origin of life.

Sprecher: Wilhelm Huck (Radboud University)

Session I

2 Synthetic Molecular Networks that Integrate Key Features of Life

How the immense complexity of living organisms has arisen is one of the most intriguing questions in contemporary science. We have started to explore experimentally how organization and function can emerge from complex molecular networks in aqueous solution (1). We focus on networks of molecules that can interconvert, to give mixtures that can change their composition in response to external or internal stimuli. Noncovalent interactions within molecules in such mixtures can lead to the formation of foldamers (2,3). Molecular recognition between molecules in such mixtures leads to their mutual stabilization, which drives the synthesis of more of the privileged structures. As the assembly process drives the synthesis of the very molecules that assemble, the resulting materials can be considered to be self-synthesizing. Intriguingly, in this process the assembling molecules are replicating themselves, where replication is driven by self-recognition of these molecules in the dynamic network (4). The selection rules that dictate which (if any) replicator will emerge from such networks are starting to become clear (5). We have also witnessed spontaneous differentiation (a process akin to speciation as it occurs in biology) in a system made from a mixture of two building blocks (6). When such systems are operated under far-from-equilibrium flow conditions, adaptation of the replicators to a changing environment can occur.
Replicators that are able to catalyse reactions other than their own formation have also been obtained, representing a first step towards metabolism (7,8). Thus, the prospect of Darwinian evolution of purely synthetic molecules is tantalizingly close and the prospect of synthesizing life de-novo is becoming increasingly realistic (9).

References:
1. Li, J.; Nowak, P.; Otto, S. J. Am. Chem. Soc. 2013, 135, 25, 9222-9239.
2. Liu, B.; Pappas, C. G.; Zangrando, E.; Demitri, N.; Chmielewski, P. J.; Otto, S. J. Am. Chem. Soc. 2019, 141, 1685-1689.
3. Pappas, C. G.; Mandal, P. K. Liu, B.; Kauffmann, B.; Miao,X.; Komáromy, D.; Hoffmann, W.; Manz, C.; Chang, R.; Liu, K.; Pagel, K.; Huc, I.; Otto, S. Nature Chem. 2020, 12, 1180–1186.
4. Carnall, J. M. A.; Waudby, C. A.; Belenguer, A. M.; Stuart, M. C. A.; Peyralans, J. J.-P.; Otto, S. Science 2010, 327, 1502-1506.
5. Malakoutikhah, M.; Peyralans, J.J-P.; Colomb-Delsuc, M.; Fanlo-Virgos, H.; Stuart, M. C. A.; Otto, S.
J. Am. Chem. Soc. 2013, 135, 49, 18406-18417.
6. Sadownik, J. W.; Mattia, E.; Nowak, P.; Otto, S. Nature Chem. 2016, 8, 264–269.
7. Monreal Santiago, G.; Liu, K.; Browne, W. R.; Otto, S. Nat. Chem. 2020, 12, 603-607.
8. Ottelé, J.; Hussain, A. S.; Mayer, C.; Otto, S. Nat. Catal. 2020, 3, 547-553.
9. Adamski, P.; Eleveld, M.; Sood, A,; Kun, A.; Szilágyi, A.; Czárán, T.; Szathmáry, E.; Otto, S. Nat. Rev. Chem. 2020, 4, 386–403.

Sprecher: Sijbren Otto (University of Groningen)

Session I: Q&A

Session II

3 Coacervate droplets as viable protocell models

In the 1920’s Oparin hypothesized that membrane free compartments formed by coacervation would have provided a viable route to compartmentalize prebiotic reactions as a precursor to the modern cell. Studies which support this hypothesis are limited in that the precise chemical composition and conditions on prebiotic earth remain a mystery. Despite this, using bottom-up approaches allows us to generate physically relevant protocell models in the lab. This provides a means to unravel the effect of compartmentalization by coacervation can have provided a selection pressure for facilitating the transition from a chemical world to a biological world.

Here, I will present strategies for the design and synthesis of protocell models based on liquid-liquid phase separation of oppositely charged components (coacervates) and describe how these compartments could be viable protocells models by that undergo growth and division and provide alternative environments compared to buffer solution to tune reaction kinetics.

Sprecher: Dora Tang (MPI of Molecular Cell Biology and Genetics)

Session II

4 On the prebiotic synthesis of non-canonical nucleosides

The structure of life’s first genetic polymer is a question of ongoing debate. The “RNA world theory” suggests RNA was life’s first nucleic acid, however ribonucleotides are complex chemical structures and simpler nucleic acids, such as threose nucleic acid (TNA), can carry genetic information. In principle, nucleic acids like TNA could have played a vital role in the origins of life, but the advent of any genetic polymer requires synthesis of its monomers. Almost 20 years ago, as part of a seminal study evaluating the potential of non-canonical nucleotides to have contributed to the origin of life, Eschenmoser and co-workers evaluated RNA, TNA, and amino-TNAs (1,2,3). In this talk, the prebiotic synthesis of TNA (4) and amino-TNA nucleosides will be re-examined in light of recent developments in prebiotic nucleotide and peptide synthesis (5,6,7,8,9,10).

References:
1. Schöning et al. Helv. Chim. Acta 2002, 85, 4111.
2. Wu et al. Org. Lett. 2002, 4, 1279.
3. Eschenmoser Orig. Life Evol. Biosph. 2004, 34, 277–306.
4. Colville & Powner Angew. Chem. Int. Ed. 2021, 60, 10526.
5. Islam & Powner Chem. 2017, 2, 470.
6. Islam et al. Nat. Chem. 2017, 9, 584.
7. Xu et al. Nat. Chem. 2017, 9, 303.
8. Powner et al. Nature 2009, 459, 239.
9. Canavelli et al. Nature 2019, 571, 546.
10. Foden et al. Science 2020, 370, 865.

Sprecher: Matthew Powner (UCL)

Session II: Q&A

13:00 Meet the Speakers of Sessions I & II

Poster Session I

14:50 Info Session

Session III

5 Mechanistic Insight into Metal Ion-Catalyzed Transamination Under Biological Conditions and its Evolutionary Implications

Several classes of biological reactions that are mediated by an enzyme and a co-factor can occur, to a slower extent, not only without the enzyme but even without the co-factor, under catalysis by metal ions. This observation has led to the proposal that metabolic pathways progressively evolved from using inorganic catalysts to using organocatalysts of increasing complexity. However, there is no clear example for which all three levels of catalytic complexity are demonstrated and mechanistically understood under biological conditions. Transamination, the biological process by which ammonia is transferred between amino acids and ketoacids, has a mechanism that has been well studied under enzyme/co-factor catalysis and under co-factor catalysis, but the metal ion-catalyzed variant was generally studied mostly at high temperatures (70-100 ºC) and the details of its mechanism remain unclear. Here, we investigate which metal ions catalyze transamination under conditions relevant to biology (pH 7, 20-50 ºC) and study the mechanism in detail. Cu2+, Ni2+, Co2+ and V5+ were identified as the most active metal ions under these constraints. Kinetic, stereochemical and computational studies illuminate the mechanism of the reaction. Cu2+ and Co2+ are found to predominantly speed up the reaction by stabilizing a key imine intermediate. V5+ is found to predominantly accelerate the reaction by increasing the acidity of the bound imine. Ni2+ is found to do both to a limited extent. A mechanistic continuity across levels of catalytic complexity is revealed which could have facilitated a smooth transition during the evolution of biochemistry from transamination catalyzed by metals, to one catalyzed by a co-factor, pyridoxal phosphate (PLP), and eventually to one catalyzed by both PLP and enzymes. Examining other biological reactions in this way may provide a systematic approach to understanding the co-evolution of co-factors and metabolism.

Sprecher: Joseph Moran (University of Strasbourg)

Session III

6 Photons, electrons, and chemistry in muddy lakes

It is plausible that the Hadean Earth had less sub-aerial land, yet it still had an enormous number of shallow water lakes, often in closed basins, and often in association with hydrothermal fields. The N2-CO2-H2O atmosphere was likely neutral or weakly reduced (with minor CO and H2), except for short periods after major impacts capable to briefly reduce the atmosphere. Episodic drying of the shallow water basins would lead to accumulation (and burial) of a variety of salts. These include metallo-cyanides like cyanocuprate and ferrocyanide, thanks to trace amounts of HCN from lightning and meteoritic reprocessing of the atmosphere. It appears that very significant deposits of ferrocyanide would accumulate in a 1000 years or less.
This presentation describes a number of experiments aimed at understanding the redox stratification and photochemistry in the shallow water column exposed to solar UV light. The irradiations were limited to the UVC and UVB range, as atmospheric CO2 would have cut off all solar UV flux below 205 nm. In addition to broadband UV lamps, we used a tunable laser pump-probe system to perform ultrafast transient spectroscopy, taking care to use astrophysically and geochemically plausible fluxes and concentrations. Our aim is to elucidate the photodynamic mechanisms of hydrated electron production and chemistry, as well as the selectivity and stability of the products, e.g. nucleotides and their oligos.

Sprecher: Dimitar Sasselov (Harvard University)

Session III: Q&A

Session IV

7 Bottom-up synthetic cells using cell-free gene expression

Cell-free gene expression (CFE) is a highly versatile experimental environment ideal to construct biochemical systems in vitro by executing either natural or synthetic gene circuits. CFE enables interrogating biochemical systems quantitatively and in isolation far from the complexity of real living cells. I will present several experiments that my lab has done recently using an E. coli CFE system. First, I will present this CFE system, what it is, what it does. In the second part of my talk, I will show how we construct synthetic cells using CFE. These minimal cells are convenient to uncover and quantify fundamental aspects of supramolecular assembly.

Sprecher: Vincent Noireaux (University of Minnesota)

Session IV

8 Did surfaces enable the origin of life?

Primitive protocells at the origin of life are commonly viewed as spherical lipidic surfactant shells, freely suspended in aqueous media. This well-established model explains initial, but not subsequent events in the development process towards structured protocells, and eventually, life-enabling functional compartments. Taking into consideration the possible involvement of naturally occurring surfaces, which were abundant as minerals and rocks on the early Earth, as energy source, my research group investigates autonomous transformation processes of phospholipid agglomerates on solid interfaces. In my talk I will report on new evidence, based on a minimal set of assumptions, for the possible involvement of surfaces in protocell nucleation and early development, and show feasible, feature-rich transformation pathways to organized structures. I will highlight possible implications of the new findings for our understanding of origin of life processes, and argue that materials properties-driven autonomous processes on solid interfaces might have played a greater role in the development towards life than is currently considered.

Sprecher: Irep Gözen (University of Oslo)

16:50 Meet the Speakers of Sessions III & IV

Poster Session II

Donnerstag, 26. August

10:45 Info Session

Session V

9 Colossal events in late accretion: A kick-start to the origins of life on Earth?

After its primary accretion had mostly finished, the proto-Earth underwent a catastrophic collision with a stray planetary embryo variably estimated to be at least equivalent to Mars’ mass (Theia). This event effectively reset Earth’s radiometric chronometers such as Pb-isotopes, and gave rise to the Moon. Since then, the Earth-Moon system has been subjected to collisions with smaller solar system objects in a declining flux termed late accretion. Evidence for late accretion mostly comes from the abundance of highly-siderphile elements in the crusts of the Earth and Moon, yet the proportional abundance of these metals between both bodies suggests that the Earth underwent a second large impact with roughly a lunar-sized objected (Moneta) approximately 4.48 billion years ago. Since Earth’s water was most likely acquired during primary accretion and geochemical analyses of Hadean zircons (≤4.4 Ga) suggest clement surface conditions, it is plausible that liquid water could have existed on the early Earth prior to the Moneta impact. Likely impact geometries show that unlike the Theia case, Moneta’s metal core should become shattered with Fe0 becoming oxidized with the water or oxidized mantle to form a dense (<90 bar) hydrogen gas atmosphere with a computed lifetime of ~200 Myr. This startling result means that a highly reducing atmosphere could have provided the conditions for gas-phase synthesis in the atmosphere of the molecular building blocks for life as we know it. Could the RNA world ultimately be a (by)product of a colossal impact?
Here I will discuss: i) the state of the solar system during and after the Moneta event, ii) the rate of decline of the bombardment flux, iii) its effects on the Hadean crust, and iv) propose a temporal window of opportunity for a chemical milieu where life originated. If the Moneta impact indeed provided the atmospheric conditions required to kick-start life on Earth, one could argue that such events on rocky exoplanets are necessary. If so, what can we say about the likelihood of such events, and on what timescales?

Sprecher: Ramon Brasser (Origins Research Institute, Research Centre for Astronomy and Earth Sciences)

Session V

10 Astrophysical origins of biomolecular homochirality

‘How did life choose its handedness?’ Just like our hands mirror each other, but cannot be superimposed on each other, amino acids and sugars exist in left- and right-handed forms. Even if there appears to be no biochemical reason to favor one enantiomer over the other, life on Earth uses almost exclusively left-handed amino acids and right-handed sugars. This is called biological homochirality and it is inevitable for building functional proteins and RNA/DNA. Numerous experiments have confirmed that simple prebiotic molecules could have been synthesized both in space as well as on the early Earth. However, the preferential selection of one enantiomer over the other remains to date most likely explained by asymmetric interactions of stellar ultraviolet circularly polarized light (UV CPL) with chiral organics. The astrophysical origin of homochirality is strengthened by i) the detection of L-enriched amino and D-enriched sugar acids in meteoritic samples, ii) the detection of CPL in several star-forming regions as well as iii) experiments studying the interaction of UV CPL with prebiotically relevant chiral species. In this talk, I will highlight significant results on electronic circular dichroism/anisotropy spectroscopy as a key tool to decipher the response of chiral molecules to UV CPL. Moreover, I will present our major findings on recent asymmetric photo-synthesis/photolysis experiments to discuss whether UV CPL could have induced a common chiral bias across molecular families?

Sprecher: Cornelia Meinert (University of Côte d'Azur)

Session V: Q&A

Session VI

11 Harnessing energy for the formation, activation and joining of prebiotic building blocks

Life is an out of equilibrium system sustained by a continuous supply of energy. In extant biology, the generation of adenosine 5'-triphosphate (ATP) and its use in the synthesis of biomolecules requires sophisticated enzymes. Before the emergence of such enzymes, alternative energy sources, perhaps assisted by simple catalysts, must have mediated the formation, activation and joining prebiotic building blocks.

Sprecher: Ziwei Liu (MRC Laboratory of Molecular Biology)

Session VI

12 RNA replication: approaches to the strand separation problem

A critical event in the origin of life is thought to have been the emergence of an RNA molecule capable of self-replication as well as mutation, and hence evolution towards ever more efficient replication. Although this ancestral replicase appears to have been lost, key aspects of RNA-catalyzed RNA replication can be studied “by proxy” with the use of modern RNA enzymes (ribozymes) generated by in vitro selection [1].

We have discovered RNA polymerase ribozymes (RPRs) that are capable of the templated synthesis of another simple ribozyme [2] or long (> 200 nt) RNA oligomers [3] and this activity is potentiated by simple Lys-rich peptides derived from the ribosomal cores [4]. I’ll also be discussing how structured media such as the eutectic phase of water ice [5] - as well as freeze-thaw cycles [6] - may aided early RNA evolution and catalysis and the emergence of functional RNAs from the pools of short RNA oligomers accessible through prebiotic chemistry [7]. More recently we have been engineering triplet polymerase ribozymes that are able to copy and replicate even highly structured RNA templates and enable non-canonical reverse and primer-free replication modes [8].

I’ll be presenting recent progress with the triplet polymerase ribozyme, specifically with respect to the strand separation problem of RNA replication arising from the remarkable stability of RNA duplex intermediates of RNA replication.

References
[1] Wachowius F, Attwater J, Holliger P.(2017) Nucleic acids: function and potential for abiogenesis.
Quarterly Reviews in Biophysics. 50:e4. doi: 10.1017/S0033583517000038. (Review)
[2] Wochner A, Attwater J, Coulson A & Holliger P (2011) Ribozyme-catalyzed transcription of an active ribozyme. Science 332, 209-212
[3] Attwater J, Wochner A & Holliger P (2013) In-ice evolution of RNA polymerase ribozyme activity. Nature Chemistry 5, 1011-1018.
[4] Tagami S, Attwater J, Holliger P. (2017) Simple peptides derived from the ribosomal core potentiate RNA polymerase ribozyme function. Nature Chemistry 9 :325-332
[5] Attwater J, Wochner A, Pinheiro VB, Coulson A & Holliger P (2010) Ice as a protocellular medium for RNA replication. Nature Communications 1, 76.
[6] Mutschler H, Wochner A & Holliger P (2015) Freeze-thaw cycles as drivers of complex ribozyme assembly. Nature Chemistry 7, 502-508.
[7] Mutschler H, Taylor AI, Porebski BT, Lightowlers A, Houlihan G, Abramov M, Herdewijn P, Holliger P. (2018) Random-sequence genetic oligomer pools display an innate potential for ligation and recombination. eLife, 7: e43022
[8] Attwater J, Raguram A, Morgunov AS, Gianni E & Holliger P (2018) Ribozyme-catalysed RNA synthesis using triplet building blocks. eLife, 7: e35255

Sprecher: Philipp Holliger (MRC Laboratory of Molecular Biology)

Session VI: Q&A

13:00 Meet the Speakers of Sessions V & VI

Poster Session III

14:50 Info Session

Session VII

13 Availability and transformation of bio-essential elements on rocky differentiated planets

The physical chemical steps leading to life on Earth took place at a time when endogenous water/rock interactions were strongly influenced by exogenous processes such as impact bombardments. At present, there is no direct measure of the influx of extraterrestrial matter in the epoch of late accretion approximately 4.48-4.0 Ga. Nevertheless, it is within that time span that life emerged on Hadean Earth, and some specific constraints on the physical and chemical regimes that modulated its emergence are now coming to light. Geochemical evidence shows that the last time the terrestrial silicate reservoirs were separated (4.48 Ga) coincides with the onset of giant planet migration (GPM) and re-set ages of asteroidal meteorites. The appearance of relatively evolved (felsic) crust and a hydrosphere on Earth before about 4.38 Ga also shows that the necessary pre-requisites for life: (i) liquid water, (ii) chemical disequilibria, (iii) organic chemical building blocks, and (iv) adequate time for biogenesis to occur were already in place a mere 100 Myr after the formation of the solar system. That does not mean that life appeared at that time, only that there were no obvious obstacles to militate the chemistry. On that basis, it is interesting to explore the degree to which extraterrestrial infall of sulphur, carbon and phosphorus fed the prebiotic planetary organic-chemistry reactor. Calculations based on monotonic decline of impactors pinned to the cratering record, dynamical simulations and geochronology for the time following GPM and benchmarked with the age of Orientale basin on the Moon at ca. 3.8 Ga, show that the total mass delivered was 21023 g. Using bulk S, C and P contents of carbonaceous (CC), ordinary (OC) and enstatite chondrites (EC) as a guide for the range of possible compositions of late accretion material, conservative ranges for the cumulative exogenous sources of these bio-essential elements to the surface zone of the Hadean Earth yield: Sulfur (5.4-11.21021g), C (7.8-691020g) and P (1.9-4.31020g). At face value, these sources are significant when compared to the contemporary surface inventories of these elements, but obviously sensitive to the chosen source (CC vs. OC vs. EC).
Bio-essential element augmentations from GPMs are likely a shared feature of some rocky differentiated exoplanets around F-, G and K-stars (M-stars are a special case that deserve separate consideration). Intriguingly, spectral data of moderately volatile vs. moderately refractory elements collected from polluted white dwarfs (WDs) suggest that rocky differentiated planets are not restricted to Sun-like stars, but are instead probably commonplace in the galaxy. The progenitors of the WDs are of stellar spectral classes (e.g. B) not under consideration for hosting worlds with biological potential.

Sprecher: Stephen Mojzsis (University of Colorado Boulder)

Session VII

14 UV-induced photochemistry of short DNA oligonucleotides: Ultrafast dynamics and prebiotic self-repair

On the surface of the Earth, DNA oligonucleotides have been exposed to UV-irradiation since very early stages of evolution [1]. The role of UV-light is ambivalent: As it can cause damage, it imposes a selection pressure on oligonucleotides but it can also repair photolesions in a photolyase-like mechanism via charge transfer from adjacent bases [2]. Both processes strongly depend on the oligonucleotide sequence and are likely to have influenced the early selection. Among the canonical nucleotides, Guanine (dG) is the strongest electron donor and therefore plays a major role in the photoinduced self-repair via charge transfer [3]. In this work, we studied the ultrafast photodynamics of short dG-containing oligonucleotides of different sequences and strand lengths with transient UV (266 nm) pump, IR (~5-7 µm) probe spectroscopy [4]. We determined the quantum efficiencies and lifetimes of the short-lived intermediate states and found marker bands which unambiguously identify the intermediates as charge transfer states. Oligonucleotides, which consisted of purines only, showed lifetimes of the charge transfer states on the order of several hundred picoseconds, regardless of the strand length. On the contrary, dinucleotides with mixed purine-pyrimidine sequences, such as d(GT) and d(GC), showed much shorter intermediate lifetimes in the range of 10 ps to 30 ps. However, for all studied oligonucleotides the efficiency of the charge transfer state formation was on the order of ~50%. These findings explain the highly reduced self-repair activity of cyclobutane-pyrimidine dimers in the vicinity of d(GT) and d(GC) in contrast to d(GA) and have implications for the photostability and sequence selectivity of short oligonucleotides under UV exposure in very early stages of evolution.

[1] S. Ranjan, R. Wordsworth, D. D. Sasselov, The Astrophysical Journal 2017, 843, 110.
[2] a) D. B. Bucher, C. L. Kufner, A. Schlueter, T. Carell, W. Zinth, J. Am. Chem. Soc. 2016, 138, 186-190; b) R. Szabla, H. Kruse, P. Stadlbauer, J. Šponer, A. L. Sobolewski, Chemical science 2018, 9, 3131-3140; c) D. J.-F. Chinnapen, D. Sen, Proceedings of the National Academy of Sciences 2004, 101, 65-69.
[3] a) Y. Paukku, G. Hill, The Journal of Physical Chemistry A 2011, 115, 4804-4810; b) Z. Pan, J. Chen, W. J. Schreier, B. Kohler, F. D. Lewis, The Journal of Physical Chemistry B 2011, 116, 698-704; c) Z. Pan, M. Hariharan, J. D. Arkin, A. S. Jalilov, M. McCullagh, G. C. Schatz, F. D. Lewis, J. Am. Chem. Soc. 2011, 133, 20793-20798.
[4] C. L. Kufner, W. Zinth, D. B. Bucher, ChemBioChem 2020, 21, 1-6.

Sprecher: Corinna Kufner (Harvard University)

Session VII: Q&A

Session VIII

15 Using a pH gradient to drive CO2 reduction

Carbon-based “organic” molecules are the foundational blocks of all living beings on Earth. Elucidating the primordial sources of reduced carbon at the emergence of life is therefore key to understanding the processes that gave rise to biochemistry from geochemistry. There were multiple plausible sources of reduced carbon on the early Earth, and a rich array of corresponding theories for the emergence of the first (bio)organics have been built on this knowledge. A variant of the alkaline-hydrothermal-vent theory suggests that organics could have been produced by indirect reduction of CO2 via H2 oxidation, facilitated by geologically sustained pH gradients. The process would be an abiotic analogue—and proposed evolutionary predecessor—of the Wood-Ljungdahl acetyl-Co-A pathway present in modern archaea and bacteria. I will discuss our results recreating in the lab an abiotic analogue of the first energetic bottleneck of the pathway, which involves the endergonic reduction of CO2 with H2 to formate. Using CO2 with H2 at room temperature under moderate pressures (1.5 bar), and in the presence of microfluidic pH gradients across inorganic Fe(Ni)S precipitates, we have produced small amounts of formate that open a way to explore further reactions in a possible abiotic analogue of the Wood-Ljungdahl pathway. Isotopic labelling with 13C confirms formate production, while deuterium (2H) labelling indicates that electron transfer to CO2 does not occur via direct hydrogenation with H2. Instead, freshly deposited Fe(Ni)S precipitates appear to facilitate electron transfer in an electrochemical-cell mechanism with two distinct half-reactions. Decreasing the pH gradient significantly leads to no detectable product, as does removing the H2 supply, or eliminating the precipitate. We believe our work demonstrates the feasibility of spatially separated, yet electrically coupled geochemical reactions as drivers of otherwise endergonic processes, as well as the potential for microscopic pH gradients to be one such driver of the early transition from geochemistry to biochemistry. The results may also be of significance for industrial and environmental applications, where other redox reactions could be driven using similarly mild approaches.

Sprecher: Victor Sojo (New York Natural History Museum)

Session VIII

16 Rethinking the “reverse-TCA world” approach to understanding the origins of protometabolism

Understanding how protometabolic pathways arose on the early Earth is primarily focussed on trying to replicate, abiotically, the reverse-TCA (rTCA) reaction pathway. However this approach runs into the same difficulties as the “RNA World” or “Protein World” hypothesis – in that it focusses only on the abiotic synthesis and transformations of the biotic components in the rTCA cycle, while ignoring plausible prebiotic alternatives. A different approach is to focus on the nature and chemistry of the reactions and the sort of transformations that can naturally emerge with alternative prebiotic building blocks – rather than placing the emphasis narrowly and only on the molecular composition dictated by the TCA pathway. Using this modus operandi we can construct model protometabolic system of reactions that is much simpler than the rTCA pathway, one that harbors the potential to act as precursors for emergence of modern metabolic pathways.

Sprecher: Ram Krishnamurthy (Scripps Research)

Session VIII: Q&A

17:00 Meet the Speakers of Sessions VII & VIII

Poster Session IV

Freitag, 27. August

10:45 Info Session

Session IX

17 Beating the serendipity of evolution: Building alternative pathways to generate life’s building blocks from inorganic carbon

Sprecher: Tobias Erb (MPI for Terrestrial Microbiology)

Session IX

18 Coupling ribozyme catalyzed ligation and recombination with heterogeneous reaction environments

Enzymatic ligation and recombination of nucleic acids are key reactions required for both self-replication and the emergence of complex sequence information. It is therefore very likely that these reactions played a fundamental role in early stages of biology. We use different ribozyme systems as models to mimic how these reactions might have proceeded under heterogeneous reaction conditions on the early Earth. While direct ligation of oligonucleotides such as RNA requires activated substrate pools, typical chemical methods for robust and continuous substrate activation are incompatible with ribozyme catalysis. We explore scenarios for the in-situ activation of RNA substrates under reaction conditions amenable to catalysis by ligase ribozymes. We find that diamidophosphate (DAP) and imidazole drive the formation of 2′,3′-cyclic phosphate RNA mono- and oligonucleotides from monophosphorylated precursors in frozen water-ice. This long-lived activation enables iterative enzymatic assembly of increasingly larger RNAs. We also demonstrate how RNA cleavage/ligation-based recombination reactions benefit dramatically from the presence of charged co-polymers, which enable the assembly of complex RNA structures from short oligonucleotides under isothermal, low-salt conditions. In summary, chemically diverse environments can help primitive nucleic acid catalysts bridge the gap between pools of short oligomers and functional RNAs.

Sprecher: Hannes Mutschler (MPI of Biochemistry)

Session IX: Q&A

Session X

19 New developments in the abiotic generation of oligonucleotide sequences from 3’,5’ cyclic guanosine monophosphate

Previous studies on the polymerization of 3’,5’ cyclic guanosine monophosphate (cGMP) demonstrated the potential of the compound in the abiotic generation of the first oligonucleotide sequences on the early Earth. These experiments were conducted under idealized laboratory conditions that logically raises the question whether the same chemistry could take place in the harsh environment present on our planet in its earliest days. In my talk I will focus on the mineralogical context of this chemistry.

Our recent results (1) show that numerous, but not all, common minerals assumed to be present on the early Earth could host the polymerization of H-form 3’,5’ cGMP. In particular, we have found that quartz varieties are especially suitable for the purpose, similar to andalusite, amphibole or micas. On the contrary, olivine, calcite, and serpentine-group minerals interfere with the studied polymerization chemistry. Our results show that crystallization on mineral surfaces, that is mainly a diffusion controlled process, determines the ability of 3’,5’ cGMP to polymerize. The observation that numerous amorphous and crystalline SiO2 forms are compatible with the oligomerization chemistry suggests that the process could commonly occur in a wide range of primordial environments allowing for crystallization of the cyclic monomers from a dropping solution.

References:
1. Šponer, J. E.; Šponer, J.; Výravský, J.; Šedo, O.; Zdráhal, Z.; Costanzo, G.; Di Mauro, E.; Wunnava, S.; Braun, D.; Matyášek, R.; Kovařík, A., Non-enzymatic, template-free polymerization of 3’,5’ cyclic guanosine monophosphate on mineral surfaces. ChemSystemsChem, in press, DOI:10.1002/syst.202100017.

Sprecher: Judit Sponer (Masaryk University)

Session X

20 The effect of broadband ultraviolet light on prebiotic and abiotic chemistry

Ultraviolet light is ubiquitous throughout the geological history of Earth. It drives photochemistry and can affect surface environments and organisms. It is an important source of chemical energy that can, in the right circumstances, be harnessed for prebiotic synthesis. When aqueous photochemistry has been explored in the lab, the source of ultraviolet light is often discrete, providing light at a single wavelength. The young Sun, on the other hand, is a broadband ultraviolet source, providing light to surface environments over a wide range of wavelengths. I review how a broadband laboratory source that approximates the ultraviolet spectrum of the young sun affects the rates and yields of various chemical reactions relevant for prebiotic synthesis of life’s building blocks. I then discuss how this broadband source can be used to explore prebiotic and abiotic environments on early Earth and Mars, and in the clouds of Venus today.

Sprecher: Paul Rimmer (University of Cambridge)

Session X: Q&A

13:00 Meet the Speakers of Sessions IX & X

Poster Session V

14:50 Info Session

Session XI

21 Emergent by-products of evolution

The earliest living systems may have used RNA to both carry genetic information and catalyze chemical reactions. The sequence-activity relationship of RNA can be captured by a ‘fitness landscape’, or the mapping of activity over all possible sequence space. Fitness landscapes describe the emergence of functional RNA by delineating possible evolutionary pathways as well as capturing the absolute frequency of functional sequences. We have developed a method to map fitness landscapes for catalytic RNA, revealing the fundamental structure of the evolutionary landscape. We also study how RNA fitness is affected by encapsulation inside an experimental model of simple cells (membrane vesicle ‘protocells’). Biophysical effects of encapsulation on the RNA can lead to emergent properties influencing RNA evolution in this system.

Sprecher: Irene Chen (UCLA)

Session XI

22 Chemistry mimicking life: From hydrothermal vent precipitates to self-propulsion

We are often surprised, if not puzzled, by inorganic reactions forming life-like, smoothly curved structures. Moreover, these abiotic structures can grow under conditions that likely existed on the early Earth four billion years ago. If we could go back in time to this period, would we be able to draw a clear line between abiotic complexity and the earliest living systems? Did life perhaps utilize inorganic self-organization to secure spatial confinement, catalytic abilities, and free energy, thus, blurring the line between life and everything else? In the context of these questions, I will introduce two experimental systems—chemical gardens and biomorphs—and discuss some of their features relating to life-like shapes derived from nonlinear reaction-transport processes, prebiotic reactions studied in microfluidic devices, and catalysis-driven self-motion.

References:
Q. Wang, L. M. Barge, and O. Steinbock, "Microfluidic Production of Pyrophosphate Catalyzed by Mineral Membranes with Steep pH Gradients", Chem. Eur. J. 25, 4732-4739, 2019.
P. Knoll and O. Steinbock, "Nanodot-to-Rod Transition and Particle Attachment in Self-Organized Polycrystalline Aggregates", Cryst. Growth Des. 19, 4218-4223, 2019.

Sprecher: Oliver Steinbock (Florida State University)

Session XI: Q&A

Session XII

23 Towards fuel-driven protocells

Deciphering the origins of the chemistry that supports life has frequently centered on determining prebiotically plausible paths that produce the molecules found in biology. What
has been less investigated is how the energy released from the breakdown of fuel sources is coupled to the persistence of the protocell. To gain better insight into how such coupled chemistry could have emerged prebiotically, we have investigated the prebiotic synthesis of the metallocofactors found in biology, namely iron-sulfur clusters, identified potential chemical fuel sources, and explored the growth and division of robust protocells. We find that the electrons released from the oxidation of the α-ketoacids found in extant metabolism can be nonenzymatically deposited in the ribodinucleotide NAD+, thereby initiating a prebiotic analogue of an electron transfer chain. Further studies on potential compositions of protocellular membranes and prebiotic growth-division processes indicate potential avenues towards a fuel-driven growth cycle.

Sprecher: Sheref Mansy (University of Alberta)

Session XII

24 Geochemical conditions determine organic product distributions in proto-metabolic reaction networks

To understand the potential for life elsewhere, it is important to try to detect organic molecules on other planets, but also to understand the “pattern distributions” of organics – that is, the relative amounts of different organic molecules in a system. It is possible that organic distribution patterns could be a biosignature, but only if they can be deconvoluted from non-biological organic chemistry. We investigated the reactions of pyruvate and glyoxylate (two prebiotically relevant organic precursors) in systems containing reactive iron minerals, driving reduction and reductive amination reactions to produce hydroxy acids and amino acids, respectively. These reactions were studied in the context of varying several environmental variables relevant to conditions that might exist in a variety of planetary environments as well as on the early Earth when life emerged: pH, the redox state of iron in the mineral, and ammonia concentration. Our results show that the positioning of the pyruvate / glyoxylate reaction network in the geochemical parameter space determines the organic product distribution pattern that results. This is significant for origin of life chemistry in which the composition and function of oligomers could be affected by the environment-driven distribution of monomers available. Also, for astrobiology and planetary science where organic distribution patterns are sometimes considered as a possible biosignature, it is important to consider geochemically-driven abiotic reactions that might produce similar effects.

Sprecher: Laurie Barge (NASA JPL)

Session XII: Q&A

17:00 Meet the Speakers of Sessions XI & XII

Poster Session VI