Extant Life Research Articles

Phase‐separated Droplets Can Direct the Kinetics of Chemical Reactions Including Polymerization, Self‐replication and Oscillating Networks

AbstractPhase‐separated compartments can localize (bio)chemical reactions and influence their kinetics. They are believed to play an important role both in extant life in the form of biomolecular condensates and at the origins of life as coacervate protocells. However, experimentally testing the influence of coacervates on different reactions is challenging and time‐consuming. We therefore use a numerical model to explore the effect of phase‐separated droplets on the kinetics and outcome of different chemical reaction systems, where we vary the coacervate volume and partitioning of reactants. We find that the rate of bimolecular reactions has an optimal dilute/coacervate phase volume ratio for a given reactant partitioning. Furthermore, coacervates can accelerate polymerization and self‐replication reactions and lead to formation of longer polymers. Lastly, we find that coacervates can ‘rescue’ oscillating reaction networks in concentration regimes where sustained oscillations do not occur in a single‐phase system. Our results indicate that coacervates can direct the outcome of a wide range of reactions and impact fundamental aspects such as yield, reaction pathway selection, product length and emergent functions. This may have far‐reaching implications for origins of life, synthetic cells and the fate and function of biological condensates.

Potential for photosynthesis on Mars within snow and ice

On Earth, solar radiation can transmit down to multiple metres within ice, depending on its optical properties. Organisms within ice can harness energy from photosynthetically active radiation while being protected from damaging ultraviolet radiation. On Mars, the lack of an effective ozone shield allows ~30% more damaging ultraviolet radiation to reach the surface in comparison with Earth. However, our radiative transfer modelling shows that despite the intense surface ultraviolet radiation, there are radiatively habitable zones within exposed mid-latitude ice on Mars, at depths ranging from a few centimetres for ice with 0.01–0.1% dust, and up to a few metres within cleaner ice. Numerical models predict that dense dusty snow in the martian mid-latitudes can melt below the surface at present. Thus, if small amounts of liquid water are available at these depths, mid-latitude ice exposures could represent the most easily accessible locations to search for extant life on Mars.

Acidophilic sulphate-reducing bacteria: Diversity, ecophysiology, and applications.

Acidophilic sulphate-reducing bacteria (aSRB) are widespread anaerobic microorganisms that perform dissimilatory sulphate reduction and have key adaptations to tolerate acidic environments (pH <5.0), such as proton impermeability and Donnan potential. This diverse prokaryotic group is of interest from physiological, ecological, and applicational viewpoints. In this review, we summarize the interactions between aSRB and other microbial guilds, such as syntrophy, and their roles in the biogeochemical cycling of sulphur, iron, carbon, and other elements. We discuss the biotechnological applications of aSRB in treating acid mine drainage (AMD, pH <3), focusing on their ability to produce biogenic sulphide and precipitate metals, particularly in the context of utilizing microbial consortia instead of pure isolates. Metal sulphide nanoparticles recovered after AMD treatment have multiple potential technological uses, including in electronics and biomedicine, contributing to a cost-effective circular economy. The products of aSRB metabolisms, such as biominerals and isotopes, could also serve as biosignatures to understand ancient and extant microbial life in the universe. Overall, aSRB are active components of the sulphur and carbon cycles under acidic conditions, with potential natural and technological implications for the world around us.

Abiotic Production of Dimethyl Sulfide, Carbonyl Sulfide, and Other Organosulfur Gases via Photochemistry: Implications for Biosignatures and Metabolic Potential

Among the atmospheric gases that have been proposed as possible biosignatures in exoplanetary atmospheres, organosulfur gases are currently considered one of the more robust indicators of extant life. These gases include dimethyl sulfide (DMS; CH3SCH3), carbonyl sulfide (OCS), and carbon disulfide (CS2), which are predominantly secondary metabolic products of living organisms on Earth. Here we present results that challenge this interpretation and provide constraints on the robustness of organosulfur gases as biosignatures. Through laboratory photochemical experiments, we show the abiotic production of organosulfur gases, including DMS, OCS, methane thiol (CH3SH), ethane thiol (C2H5SH), CS2, and ethyl methyl sulfide (CH3CH2SCH3) via photochemistry in analog atmospheres. Gas-phase products of H2S/CH4/N2 haze photochemistry, with or without CO2, were collected and analyzed using gas chromatography equipped with sulfur chemiluminescence detection. Depending on the starting conditions, we estimate that DMS, OCS, CH3SH, CH3CH2SH, CS2, and CH3CH2SCH3 are produced in mixing ratios >10−1 ppmv. We further demonstrate that as the mixing ratio of CO2 increases, so does the relative importance of OCS compared to DMS. Although our results constrain the robustness of common organosulfur gases as biosignatures, the presence of these compounds may serve as an indicator of metabolic potential on exoplanets.

Coenzymes in a pre-enzymatic metabolism.

Experiments now support theoretical suggestions that coenzymes mediated key metabolic reactions before the emergence of enzymes. Three coenzymes believed essential to the core metabolism of the last universal common ancestor to extant life (pyridoxal phosphate, adenosine diphosphate, and nicotinamide adenine dinucleotide) were recently found to be active in their corresponding metabolic reactions in the absence of enzymes. These findings suggest an earlier contribution of coenzymes to abiogenesis, ultimately yielding insights into the prebiotic origins of metabolism.

Stem Life: A Framework for Understanding the Prebiotic-Biotic Transition

Abiogenesis is frequently envisioned as a linear, ladder-like progression of increasingly complex chemical systems, eventually leading to the ancestors of extant cellular life. This “pre-cladistics” view is in stark contrast to the well-accepted principles of organismal evolutionary biology, as informed by paleontology and phylogenetics. Applying this perspective to origins, I explore the paradigm of “Stem Life,” which embeds abiogenesis within a broader continuity of diversification and extinction of both hereditary lineages and chemical systems. In this new paradigm, extant life’s ancestral lineage emerged alongside and was dependent upon many other complex prebiotic chemical systems, as part of a diverse and fecund prebiosphere. Drawing from several natural history analogies, I show how this shift in perspective enriches our understanding of Origins and directly informs debates on defining Life, the emergence of the Last Universal Common Ancestor (LUCA), and the implications of prebiotic chemical experiments.

Discriminating between extinct and extant life detection: implications for future Mars missions

Discriminating between extinct and extant life detection: implications for future Mars missions

Detecting life by behavior, the overlooked sensitivity of behavioral assays

Detecting life has driven research and exploration for centuries, but recent attempts to compile and generate a framework that summarizes life features, aimed to develop strategies for life detection missions beyond planet Earth, have disregarded a key life feature: behavior. Yet, some behaviors such as biomineralization or motility have occasionally been proposed as biosignatures to detect life. Here, we capitalize on a specific taxis’ motility behavior, magnetotaxis, to experimentally provide insights in support of behavior as an unambiguous, sensitive biosignature, and magnetic forces as a prescreening option. Using a magnetotactic bacterial species, Magnetospirillum magneticum, we conducted a lab sensitivity experiment comparing PCR with the hanging drop behavioral assay, using a dilution series. The hanging drop behavioral assay visually shows the motility of MTB toward magnetic poles. Our findings reveal that the behavioral assay exhibits higher sensitivity in the detection of M. magneticum when compared to the established PCR protocol. While both methods present similar detection sensitivities at high concentrations, at ≥ 10–7 fold dilutions, the behavioral method proved more sensitive. The behavioral method can detect bacteria even when samples are diluted at 10–9. Comparable results were obtained with environmental samples from the Hula Valley. We propose behavioral cues as valuable biosignatures in the ongoing efforts of life detection in unexplored aquatic habitats on Earth and to stimulate and support discussions about how to detect extant life beyond Earth. Generic and robust behavioral assays can represent a methodological revolution.

Supercritical CO2 and Subcritical H2O Analysis Instrument: Automated Lipid Analysis for In Situ Planetary Life Detection.

The search for extraterrestrial extant or extinct life in our Solar System will require highly capable instrumentation and methods for detecting low concentrations of biosignatures. This paper introduces the Supercritical CO2 and Subcritical H2O Analysis (SCHAN) instrument, a portable and automated system that integrates supercritical fluid extraction (SFE), supercritical fluid chromatography (SFC), and subcritical water extraction coupled with liquid chromatography. The instrument is compact and weighs 6.3 kg, making it suitable for spaceflight missions to planetary bodies. Traditional techniques, such as gas chromatography-mass spectrometry (MS), face challenges with involatile and thermally labile analytes, necessitating derivatization. The SCHAN instrument, however, eliminates the need for derivatization and cosolvents by utilizing neat supercritical CO2 with water as an additive. This SFE-SFC-MS method gives efficient lipid biosignature separations with median detection limits of 10 pg/g (ppt) for fatty acids and 50 pg/g (ppt) for sterols. Several free fatty acids and cholesterol were among the detected peaks in biologically lean samples from the Atacama Desert, demonstrating the instrument's potential for in situ life detection missions. The SCHAN instrument addresses the challenges of conventional systems, offering a compact, portable, and spaceflight-compatible tool for the analysis of organics for future astrobiology-focused missions.

Robotic exploration of Martian caves: Evaluating operational concepts through analog experiments in lava tubes

Caves on Mars are a tantalizing target for exploration, as they could harbor evidence of extinct or extant life, clues to the planet’s geological history, and even potential future human habitation. However, the inherent challenges of navigating unknown and challenging terrain, coupled with limited communication capabilities, pose significant obstacles for robotic exploration in these caves. This paper presents the results of an effort to evaluate different operational concepts for a mission dedicated to exploration of caves on Mars. We conducted a series of analog exploration experiments in lava tubes on Earth, testing two hypotheses: (1) that two robots are more effective than one, and (2) that high levels of autonomy are more effective than low levels of autonomy. Our findings suggest that two robots are indeed more effective, except in low autonomy cases, where more operational resources are required. We also found that full autonomy is more efficient than low autonomy, as it enables quicker exploration and detection of targets of interest. However, the low autonomy cases benefited from the operator input to acquire higher quality data, an area of autonomy requiring further development. This paper provides insight into the design of our experiments, as well as detailing the results and implications for the design of future missions to explore caves on Mars. By shedding light on the operational concepts tested and their corresponding outcomes, we contribute to the knowledge base required to formulate optimal strategies for the realization of successful cave exploration missions on the Red Planet.

Rethinking life and predicting its origin.

The definition, origin and recreation of life remain elusive. As others have suggested, only once we put life into reductionist physical terms will we be able to solve those questions. To that end, this work proposes the phenomenon of life to be the product of two dissipative mechanisms. From them, one characterises extant biological life and deduces a testable scenario for its origin. The proposed theory of life allows its replication, reinterprets ecological evolution and creates new constraints on the search for life.

Enhancing graduate employability – exploring the influence of experiential simulation learning on life skill development

ABSTRACT Skills and knowledge which increase the likelihood of university graduates finding employment is an increasingly important factor for higher education institutions. Even though subject matter expertise remains a primary objective, supporting students to build life skills that are desired by employers is essential to enhance graduate employability. Firstly, we draw on consultive interviews with 11 graduate recruiters to build a life skill ability scale. Through these interviews, we identify two constructs worth measuring (resilience and adaptability) not yet represented in extant life skill ability scales. Thereby contributing to life skills measures and their link to graduate employability. Secondly, this paper explores the influence of a team-based business simulation on the development of life skills at two higher education institutions in the UK for first- and fourth-year undergraduate students. Through a pre-survey and post-survey, this paper empirically finds that experiential learning by means of a team-based business simulation has an overwhelmingly positive influence on first-year students’ self-assessed life skill development as well as their course-specific subject matter expertise. Yet, the findings show less significant results for fourth-year students. This contributes to our understanding of business simulations as a pedagogical practice and its benefits for students beyond their education.

EELS: Autonomous snake-like robot with task and motion planning capabilities for ice world exploration.

Ice worlds are at the forefront of astrobiological interest because of the evidence of subsurface oceans. Enceladus in particular is unique among the icy moons because there are known vent systems that are likely connected to a subsurface ocean, through which the ocean water is ejected to space. An existing study has shown that sending small robots into the vents and directly sampling the ocean water is likely possible. To enable such a mission, NASA's Jet Propulsion Laboratory is developing a snake-like robot called Exobiology Extant Life Surveyor (EELS) that can navigate Enceladus' extreme surface and descend an erupting vent to capture unaltered liquid samples and potentially reach the ocean. However, navigating to and through Enceladus' environment is challenging: Because of the limitations of existing orbital reconnaissance, there is substantial uncertainty with respect to its geometry and the physical properties of the surface/vents; communication is limited, which requires highly autonomous robots to execute the mission with limited human supervision. Here, we provide an overview of the EELS project and its development effort to create a risk-aware autonomous robot to navigate these extreme ice terrains/environments. We describe the robot's architecture and the technical challenges to navigate and sense the icy environment safely and effectively. We focus on the challenges related to surface mobility, task and motion planning under uncertainty, and risk quantification. We provide initial results on mobility and risk-aware task and motion planning from field tests and simulated scenarios.

Chiroptical properties of membrane glycerophospholipids and their chiral backbones.

Glycerophospholipid membranes are one of the key cellular components. Still, their species-dependent composition and homochirality remain an elusive subject. In the context of the astrophysical circularly polarized light scenario likely involved in the generation of a chiral bias in meteoritic amino and sugar acids in space, and consequently in the origin of life's homochirality on Earth, this study reports the first measurements of circular dichroism and anisotropy spectra of a selection of glycerophospholipids, their chiral backbones and their analogs. The rather low asymmetry in the interaction of UV/VUV circularly polarized light with sn-glycerol-1/3-phosphate indicates that chiral photons would have been unlikely to directly induce symmetry breaking to membrane lipids. In contrast, the anisotropy spectra of d-3-phosphoglyceric acid and d-glyceraldehyde-3-phosphate unveil up to 20 and 100 times higher maximum anisotropy factor values, respectively. This first experimental report, targeted on investigating the origins of phospholipid symmetry breaking, opens up new avenues of research to explore alternative mechanisms leading to membrane lipid homochirality, while providing important clues for the search for chiral biosignatures of extant and/or extinct life in space, in particular for the ExoMars 2028 mission.

Biosignature Detection and MinION Sequencing of Antarctic Cryptoendoliths After Exposure to Mars Simulation Conditions.

In the search for life in our Solar System, Mars remains a promising target based on its proximity and similarity to Earth. When Mars transitioned from a warmer, wetter climate to its current dry and freezing conditions, any putative extant life probably retreated into habitable refugia such as the subsurface or the interior of rocks. Terrestrial cryptoendolithic microorganisms (i.e., those inhabiting rock interiors) thus represent possible modern-day Mars analogs, particularly those from the hyperarid McMurdo Dry Valleys in Antarctica. As DNA is a strong definitive biosignature, given that there is no known abiotic chemistry that can polymerize nucleobases, we investigated DNA detection with MinION sequencing in Antarctic cryptoendoliths after an ∼58-sol exposure in MARTE, a Mars environmental chamber capable of simulating martian temperature, pressure, humidity, ultraviolet (UV) radiation, and atmospheric composition, in conjunction with protein and lipid detection. The MARTE conditions resulted in changes in community composition and DNA, proteins, and cell membrane-derived lipids remained detectable postexposure. Of the multitude of extreme environmental conditions on Mars, UV radiation (specifically UVC) is the most destructive to both cells and DNA. As such, we further investigated if a UVC exposure corresponding to ∼278 martian years would impede DNA detection via MinION sequencing. The MinION was able to successfully detect and sequence DNA after this UVC radiation exposure, suggesting its utility for life detection in future astrobiology missions focused on finding relatively recently exposed biomarkers inside possible martian refugia.

Solid-State Single-Molecule Sensing with the Electronic Life-Detection Instrument for Enceladus/Europa (ELIE).

Growing evidence of the potential habitability of Ocean Worlds across our solar system is motivating the advancement of technologies capable of detecting life as we know it-sharing a common ancestry or physicochemical origin with life on Earth-or don't know it, representing a distinct emergence of life different than our one known example. Here, we propose the Electronic Life-detection Instrument for Enceladus/Europa (ELIE), a solid-state single-molecule instrument payload that aims to search for life based on the detection of amino acids and informational polymers (IPs) at the parts per billion to trillion level. As a first proof-of-principle in a laboratory environment, we demonstrate the single-molecule detection of the amino acid L-proline at a 10 μM concentration in a compact system. Based on ELIE's solid-state quantum electronic tunneling sensing mechanism, we further propose the quantum property of the HOMO-LUMO gap (energy difference between a molecule's highest energy-occupied molecular orbital and lowest energy-unoccupied molecular orbital) as a novel metric to assess amino acid complexity. Finally, we assess the potential of ELIE to discriminate between abiotically and biotically derived α-amino acid abundance distributions to reduce the false positive risk for life detection. Nanogap technology can also be applied to the detection of nucleobases and short sequences of IPs such as, but not limited to, RNA and DNA. Future missions may utilize ELIE to target preserved biosignatures on the surface of Mars, extant life in its deep subsurface, or life or its biosignatures in a plume, surface, or subsurface of ice moons such as Enceladus or Europa. One-Sentence Summary: A solid-state nanogap can determine the abundance distribution of amino acids, detect nucleic acids, and shows potential for detecting life as we know it and life as we don't know it.

Immunisations and imagining imperilled fertility: Women's trials of COVID-19 vaccines and reproductive/citizenship transgressions in pandemic times

Drawing from a narrative interview study with people who had, and recovered from COVID-19, this paper examines participants' concerns regarding imperilled fertility, which featured in many narratives about immunity to COVID-19 and decisions over COVID-19 vaccines, especially women participants. Approaching these vaccine anxieties from an intersectional perspective, we explore narratives of imagined fertility being disrupted by COVID-19 vaccines – narratives that are socially contoured by race/ethnicity, gender and life course stage, and position within families. Such participants faced the risk of transgressing gendered reproductive expectations which cast life-making as a hallowed and unquestioned – yet at the same time transgressing expectations that model citizens will accept the vaccine and not go against the herd. Taking forward work on the tensions between vaccines being between protective of extant life, and threatening to future life, we explore deferral of vaccine decisions as a way of accommodating multiple expectations of good reproductive citizenship, and consider how institutions could become more trustworthy in light of fertility anxieties.

On the potential roles of phosphorus in the early evolution of energy metabolism.

Energy metabolism in extant life is centered around phosphate and the energy-dense phosphoanhydride bonds of adenosine triphosphate (ATP), a deeply conserved and ancient bioenergetic system. Yet, ATP synthesis relies on numerous complex enzymes and has an autocatalytic requirement for ATP itself. This implies the existence of evolutionarily simpler bioenergetic pathways and potentially primordial alternatives to ATP. The centrality of phosphate in modern bioenergetics, coupled with the energetic properties of phosphorylated compounds, may suggest that primordial precursors to ATP also utilized phosphate in compounds such as pyrophosphate, acetyl phosphate and polyphosphate. However, bioavailable phosphate may have been notably scarce on the early Earth, raising doubts about the roles that phosphorylated molecules might have played in the early evolution of life. A largely overlooked phosphorus redox cycle on the ancient Earth might have provided phosphorus and energy, with reduced phosphorus compounds potentially playing a key role in the early evolution of energy metabolism. Here, we speculate on the biological phosphorus compounds that may have acted as primordial energy currencies, sources of environmental energy, or sources of phosphorus for the synthesis of phosphorylated energy currencies. This review encompasses discussions on the evolutionary history of modern bioenergetics, and specifically those pathways with primordial relevance, and the geochemistry of bioavailable phosphorus on the ancient Earth. We highlight the importance of phosphorus, not only in the form of phosphate, to early biology and suggest future directions of study that may improve our understanding of the early evolution of bioenergetics.

Real-Time Quantification of Size-Resolved Bioaerosols and Inert Particles in Spacecraft Assembly Facilities at the NASA Jet Propulsion Laboratory.

Abstract Responsible space exploration is a cornerstone of planetary protection, particularly at sites in the Solar System with a high potential for the existence of extant life. To limit bioburden, spacecraft assembly occurs in cleanroom facilities. Cleanroom levels are established through air particulate counters that can assess particle size distribution and concentration but cannot detect bioaerosols. Additionally, these devices do not detect in real-time, which poses a risk to critical flight hardware assemblies or even mission timelines. A first-of-its-kind study was conducted to simultaneously detect bioaerosols, inert particles, and their size distribution in real-time in operational spacecraft assembly cleanrooms at NASA's Jet Propulsion Laboratory in Pasadena, CA, USA, using the BioVigilant IMD-A® 350 (Azbil Corporation, Tucson, AZ, USA). The IMD-350A continuously sampled during operations and no-operation 6 h intervals in two facilities per cleanroom class: ISO 6, ISO 7, and ISO 8. A positive correlation was established between human presence in the cleanroom and elevated bioaerosol counts. Smaller particles of sizes 0.5 and 1 μm constituted an average ∼91% of the total bioaerosols detected in At Work intervals across all ISO classes observed. The results of this study were used to establish bioburden particulate thresholds for the most stringent JPL cleanrooms used in the assembly of the Sample Caching System for the Mars 2020 Perseverance rover.

Spectroscopic investigations of fungal biomarkers after exposure to heavy ion irradiation

The main objective of the ongoing and future space exploration missions is the search for traces of extant or extinct life (biomarkers) on Mars. One of the main limiting factors on the survival of Earth-like life is the presence of harmful space radiation, that could damage or modify also biomolecules, therefore understanding the effects of radiation on terrestrial biomolecules stability and detectability is of utmost importance. Which terrestrial molecules could be preserved in a Martian radiation scenario? Here, we investigated the potential endurance of fungal biomolecules, by exposing de-hydrated colonies of the Antarctic cryptoendolithic black fungus Cryomyces antarcticus mixed with Antarctic sandstone and with two Martian regolith analogues to increasing doses (0, 250 and 1000 Gy) of accelerated ions, namely iron (Fe), argon (Ar) and helium (He) ions. We analyzed the feasibility to detect fungal compounds with Raman and Infrared spectroscopies after exposure to these space-relevant radiations.