There truly is no feeling better than that spark of curiosity and excitement going into a new project. It’s my favorite part about being a scientist!
Holly Rucker
@hollyrucker.bsky.social
PhD candidate at UW-Madison // interested in astrobiology, geobiology, isotopes, and Precambrian Earth
New preprint! How do you engineer one of biology’s most complex enzymes without breaking it? We used evolution as a guide to map a protein interface in nitrogenase, screening >9,000 variants to reveal sequence-function rules for future nitrogen fixation engineering. www.biorxiv.org/content/10.6...
Evolution-guided engineering of an ancient nitrogenase interface enhances enzyme activity and stability
Nitrogenase is the only enzyme capable of biological nitrogen fixation and a major target for sustainable agricultural engineering, yet its functional and structural complexity has made it difficult t...
biorxiv.org
Just finished this book and absolutely loved it! A very insightful look into the complicated history of taxonomy. I wasn’t familiar with Georges-Louis Leclerc, Comte de Buffon before this book and I’m so glad I am now!
Latest paper out in Nature Communications! We find molecular dating evidence that life was using molybdenum and tungsten as far back as ~3.4 billion years ago, reshaping how we think about trace metals and early microbial evolution. Read here: www.nature.com/articles/s41...
Biological use of molybdenum and tungsten stems back to 3.4 billion years ago - Nature Communications
The study shows that life began using molybdenum and tungsten enzymes as early as 3.7–3.1 billion years ago. Study reveals that key metabolic processes arose despite scarce metals and highlighting the...
nature.com
Abstract submissions for the Astrobiology Graduate Conference 2026 are open! Deadline is May 29th; see our website for more details! 🌵🪐🦠 #abgradcon #abgradcon2026 #astrobiology
🚨New pub is live! It was really fun to write this with my friend @carolinamicro.bsky.social. If you're curious about how phylogenomics has shaped our understanding of early life and want guidance on how to do this kind of work yourself, then this review is for you. Enjoy! 🚀 doi.org/10.1093/jamb...
Tracing ancient life through the genomic record
Abstract. Since its origins, life has been profoundly interconnected with Earth’s history. The genomes that underpin the diversity of modern life forms hav
doi.org
Latest work! 🧬 We uncover how evolution of translation initiation factor 2 (IF2) extensions links translation to bacterial stress response. We map 7 structural architectures & show how terminal extensions are enriched in intrinsic disorder & phase-separation features. Link: doi.org/10.64898/202...
New paper! Why are some Nitrogen fixing microbes more complex? @msobol.bsky.social et al. find that microbes with more N2-fixation genes have larger, more versatile genomes, showing how changing environments shaped this key metabolism! > academic.oup.com/ismecommun/a... @isme-microbes.bsky.social
Ecological constraints and evolutionary trade-offs shape nitrogen fixation across habitats
Abstract. From its earliest beginnings, life’s expansion into new habitats has been profoundly shaped by its reciprocal interactions with Earth’s changing
academic.oup.com
Our latest paper on ancient microbes and nitrogen is featured on the NASA website today! 🚀🔬Way to go, @hollyrucker.bsky.social! Resurrecting Ancient Enzymes in NASA’s Search for Life Beyond Earth www.nasa.gov Paper link: www.nature.com/articles/s41... #astrobiology @uwmadscience.bsky.social
NASA
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nasa.gov
Our new paper, out today! We resurrected ancient nitrogenases first used by life on Earth 3 billion years ago. We combined synthetic biology and geology & validated their chemical #biosignature in rocks that helps reveal ancient life on Earth!(and beyond!) Link: www.nature.com/articles/s41...
Resurrected nitrogenases recapitulate canonical N-isotope biosignatures over two billion years - Nature Communications
The study shows that nitrogenase enzymes have maintained stable isotope signatures over billions of years, revealing how ancient microbes shaped Earth’s nitrogen cycle and offering a new experimental ...
nature.com
Happy to share that a fantastic article about my latest research was just published on NASA’s website! Very grateful to have such a spotlight on my PhD research and recent Nature Communications paper.
Resurrecting Ancient Enzymes in NASA's Search for Life Beyond Earth - NASA Science
NASA-supported scientists have resurrected an enzyme first used by organisms on Earth 3.2-billion years ago and, in the process, have validated a chemical
science.nasa.gov
A very cool little announcement I saw on my Google Scholar page today!
Having a wonderful time at the Geobiology GRC (and GRS) this week! 🦠🪨🧬
Consider submitting a #AbSciCon2026 abstract to our session on transition metals! #abscicon26 #geobiology
Morgan Sobol@msobol.bsky.social · 7mo ago🚀 Planning to attend #AbSciCon2026 and study the role of metals in life evolution and life elsewhere? Then consider submitting an abstract to our session #20- Transition Metals in Habitability and Biological Evolution. Details below and at this link: agu.confex.com/agu/abscicon...
IsoCamp was one of the most rewarding experiences of my PhD thus far-I highly recommend it for anyone interested in stable isotopes!
IsoCamp at UNM@isocampunm.bsky.social · 7mo agoWe are now accepting applications for #IsoCamp2026! Join us in beautiful New Mexico June 15th-26th to learn about stable isotopes from expert instructors and get hands-on instrument training. The application deadline is February 28th. For more information, or to apply, go to isocamp.org. Pls share!
🚀 Planning to attend #AbSciCon2026 and study the role of metals in life evolution and life elsewhere? Then consider submitting an abstract to our session #20- Transition Metals in Habitability and Biological Evolution. Details below and at this link: agu.confex.com/agu/abscicon...
We are now accepting abstracts for our session: Transition Metals in Habitability and Biological Evolution for AbSciCon 26! 🪨🧪🦠 Abstract submissions are open until Jan 14: agu.confex.com/agu/abscicon... #AbSciCon
We are now accepting abstracts for our session: Transition Metals in Habitability and Biological Evolution for AbSciCon 26! 🪨🧪🦠 Abstract submissions are open until Jan 14: agu.confex.com/agu/abscicon... #AbSciCon
Wisconsin Evolution is accepting applications for our Seminar Series' Early Career Scientist Award. Come share your evolution research and visit UW-Madison's evolution community. Open to grad students and postdocs (<5 yrs post PhD) from outside UW-Madison. Apply by Dec 15th here: shorturl.at/4a4O6
Early Career Scientist Awards 2026
Application to the UW-Madison Evolution Seminar Series - Early Career Scientist Awards.
urldefense.com
Has anyone here used stoggles and liked them? I would love to not have to switch between my safety glasses and regular glasses constantly in lab but they are a bit pricey 🥽
🎉 Huge congrats to Holly Rucker for winning First Place in the Midwest Geobiology Conference Best Oral Presentation! 🏆 Amazing work, Holly! @uwmadscience.bsky.social @uwbact.bsky.social @hollyrucker.bsky.social #UWMad
WiCOR seeks a #postdoctoral fellow to participate in Center #research in any discipline related to our two main research questions: 1. How do habitable planets form? 🪐 2. How does life emerge on habitable planets? 🧬 Full information at: wicor.wisc.edu/postdoc/ Apply by Nov 15 🔭 🧪 #postdoc #hiring
currently reading: The Sea Around Us I somehow have never read any of Rachel Carson’s books so I am making up for that now!
I had a great time being interviewed for this!
Kaçar Lab at UW-Madison@kacarlab.bsky.social · 10mo agoNASA may have just brought us closer to answering one of humanity’s biggest questions: What is life? Our amazing student Holly Rucker @hollyrucker.bsky.social breaks down what Mars’ potential biomarkers mean for the search for life 🌌🚀 @uwmadscience.bsky.social 👇 www.youtube.com/watch?v=z6mQ...
currently reading Strata by Laura Poppick-looking forward to her talk for the WI Book Festival!
Finished some updates to the gas manifold I’ve been building and turned it on for the first time today- it works great 🥹🙌🏻
Kaçar Lab at UW-Madison@kacarlab.bsky.social · last yr.Accomplishment of the week! Let's go!!! @hollyrucker.bsky.social
New preprint on ancient oceans! We challenge the idea of early Earth as major N2O source; reshaping views on climate & biosignatures. Led by S. Buessecker @annedekas.bsky.social lab! ➡️ Microbial N2O reduction in sulfidic waters: Implications for Proterozoic oceans www.biorxiv.org/content/10.1...
Microbial N2O reduction in sulfidic waters: Implications for Proterozoic oceans
Throughout Earth’s history, shifts in ocean redox influenced the bioavailability of trace metals, shaping the activity of microorganisms. In Proterozoic oceans, the precipitation of copper (Cu) with sulfide was hypothesized to limit the bioavailability of Cu. This limitation may have suppressed microbial reduction of nitrous oxide (N2O), due to the Cu dependency of nitrous oxide reductase (Nos). It is thought that without this critical microbial sink, Proterozoic oceans were a significant net source of N2O. Here, we revisit this paradigm in light of recently derived ∼20-fold lower estimates for sulfide in Proterozoic seawater and an empirical evaluation of the potential for microbial N2O reduction under sulfidic conditions. Leveraging publicly available environmental metatranscriptomes, we infer active N2O reduction from the detection of nosZ transcripts in multiple marine and lacustrine systems in which sulfide and Cu concentrations are analogous to those of the Proterozoic. In controlled culture experiments, we demonstrate that the purple non-sulfur bacterium Rhodopseudomonas palustris can reduce N2O at sulfide concentrations up to 100 µM, well above levels predicted for Proterozoic oceans. Based on trace metal speciation modeling, we suggest that Cu remains bioavailable under Proterozoic-like conditions as a dissolved CuHS complex. Using phylogenetics, we infer that early N2O reducers were probably anoxygenic phototrophs and performed N2O reduction as dark metabolism. Collectively, these observations suggest microbial N2O reduction occurs under euxinic conditions, implying that Proterozoic marine N2O emissions were substantially lower than previously proposed. Our conclusions inform our understanding of the microbial ecology in sulfidic waters, the early climate, and the search for extraterrestrial life. ### Competing Interest Statement The authors have declared no competing interest. National Aeronautics and Space Administration, https://ror.org/027ka1x80, 80NSSC17K0296
biorxiv.org
I feel like Zotero’s upload feature only successfully copies over the citation info about 50% of the time 😓
Been analyzing vacuña bone, tooth (left) and collagen (right) for C/N/O isotopes this week at IsoCamp! @isocampunm.bsky.social
