New astrobiology papers highlighted

Two new astrobiology papers are getting attention for the same reason. They both ask a very old question in a very technical way: what kinds of chemistry could have kept the first living systems alive before Earth had much edible organic matter to offer? One paper looks at modern microbes that live on volcanic terrain and can pull energy from carbon monoxide. The other steps back and reviews the redox chemistry of the early Earth itself, tracing how electrons moved through air, water, rock, and minerals before biology took over. Neither paper is flashy. Both are about constraints. That is why they matter. (academic.oup.com) The volcanic-microbe paper, published in *FEMS Microbiology Ecology* on February 25, is a review of carbon monoxide dehydrogenase, or CODH, in microbes from volcanic “astrobiological analogues” on Earth. These are places that resemble parts of early Earth and, in some respects, Mars, Venus, or icy moons: geochemically active, poor in organic carbon, and rich in reactive gases. The review pulls together genomic evidence from eight volcanic sites around the world and finds that genes for CODH are a recurring feature of these systems. In other words, when life is pushed into a raw, newly formed, nutrient-poor landscape, one of the tools it keeps reaching for is the ability to oxidize carbon monoxide. (academic.oup.com) That matters because carbon monoxide is not just a poison in human stories. In microbial stories, it can be fuel. CODH catalyzes the conversion of CO to carbon dioxide, extracting electrons in the process. The review reports that genes for aerobic CO oxidation, especially coxL, were consistently abundant and conserved across the volcanic datasets, while genes tied to anaerobic CO oxidation were more patchy and site-specific. At Poás Volcano in Costa Rica, the authors highlight especially versatile taxa, including members of Desulfobacterota, spread across nine gene clusters. The pattern is not random. It suggests that CO metabolism is not an exotic side trick in these habitats. It is part of the survival kit. (academic.oup.com) That survival-first view fits with a broader shift in microbiology. A 2019 study in *The ISME Journal* showed that aerobic bacteria can use atmospheric carbon monoxide not mainly to grow fast, but to endure starvation. In *Mycobacterium smegmatis*, expression of a form I CODH jumped roughly 50-fold when organic carbon ran out, and the enzyme improved long-term survival rather than acting as a detox system. The same paper argued that atmospheric CO oxidation is widespread and likely ancestral among these enzymes. So the new volcanic review is not claiming that carbon monoxide powered the first ecosystems all by itself. It is pointing to a more modest and more convincing idea: in harsh settings, trace gases can keep metabolism barely running until richer ecologies appear. (nature.com) That leads straight into the second paper, published April 2 in *Communications Chemistry*. It is a review of early-Earth redox chemistry, and its central claim is that the old origin-of-life camps may be arguing over different pieces of the same machine. The authors revisit the familiar settings — deep-sea hydrothermal vents, volcanic lakes, hot springs, geysers, shallow waters — and argue that each supplied different redox conditions, minerals, metals, and physical cycles. They also argue that the Hadean atmosphere was not simply reducing or oxidizing, but weakly oxidizing overall with transient reducing episodes. That is a more dynamic picture of the young planet, and it changes the logic of the debate. (nature.com) In that picture, heterotrophic and chemoautotrophic origin scenarios stop looking mutually exclusive. The review says hydrothermal systems could have driven organic synthesis while also supporting primitive metabolism based on inorganic compounds. Organic molecules could then have been transported between environments instead of being made and used in one perfect cradle. Life, on this account, did not need a single magic birthplace. It could have emerged through linked local settings that traded chemicals back and forth. The paper does not solve the origin of life. It does something better. It narrows the problem to electron flow, mineral context, and transport. (nature.com) Read together, the two papers push astrobiology in the same direction. Stop looking for lush beginnings. Start with poor worlds. Start with rock, gas, and redox gradients. Start with metabolisms that survive on leftovers and trace compounds. The volcanic review ends there, with microbes in barren deposits still finding energy in carbon monoxide, and with Poás Volcano standing out as one of the harshest modern places where that ancient logic is still visible. (academic.oup.com)