About

The Anbarlab at Arizona State University is a diverse group of graduate and undergraduate students, postdocs, and research scientists, committed to exploring our world and developing applied solutions to the challenges we face. We hail from the fields of geology, chemistry, forensic science, and education.

Research topics

• Geology
• Astrobiology
• Earth science
• Paleontology
• Computer Science
• Biology
• Physics
• Computer Security
• Geography
• Astronomy
• Political Science
• Geochemistry
• Chemistry
• Social Science
• Artificial Intelligence
• Environmental chemistry
• Sociology
• Aerospace engineering
• Aeronautics
• Engineering ethics
• Engineering
• Cartography
• Psychology
• Philosophy

Selected publications

• Iron speciation and partitioning of micronutrient transition metals in laboratory synthesized hydrothermal plume particles

  Geochimica et Cosmochimica Acta · 2026-02-11

  article
  PublisherDOI

• Lowering the Mo limit for nitrogen fixation by Mo-nitrogenase

  Communications Earth & Environment · 2026-01-14

  articleOpen access

  Archean ocean marine primary productivity may have been limited by biologically available nitrogen. Due to low molybdenum abundances, early biological nitrogen fixation is thought to have relied on alternative nitrogenases that incorporate vanadium or iron instead of molybdenum. Here, we examine nitrogen fixation in a Cyanobacteria-dominated, ferruginous, low-sulfate, low-molybdenum lake, which replicates biological and chemical conditions relevant to early marine primary productivity. Nitrogen fixation occurs even when molybdenum is <1 nM, 100x less than the abundance in modern oceans. Molybdenum additions did not increase nitrogen fixation rates, indicating that diazotrophs were not molybdenum limited. Only the molybdenum-iron nitrogenase was detected in metagenomes and metatranscriptomes, indicating that the alternative nitrogenases were not required. We suggest that low sulfate (<1 μM) and/or efficient uptake mitigated molybdenum limitation. These results indicate that molybdenum bioavailability may be strongly controlled by sulfate and that alternative nitrogenases are not essential for nitrogen fixation at low molybdenum. Substantial nitrogen fixation at sub-nanomolar molybdenum concentrations without alternative nitrogenases, with important implications for early Earth primary productivity, according to results from a ferruginous, low-sulfate, low-Mo, cyanobacteria-dominated lake.

  PublisherOA PDFDOI

• Revisiting the Bio-Inorganic Bridge 25 Years Later

  Annual Review of Earth and Planetary Sciences · 2026-02-05 · 1 citations

  article

  The concept of the bio-inorganic bridge links the evolution of Earth's biosphere to the broad-scale changes in trace metal availability driven by shifts in ocean redox conditions. This framework connects the acquisition of metal enzyme cofactors to evolving environmental conditions over geological time. Various approaches have been taken to building this bridge, integrating insights from microbiology, phylogenomics, ecophysiology, and geochemistry. Much of this work has been framed around a model of Earth's oceans evolving from an Archean anoxic state, through an intermediate sulfidic phase, to the well-oxygenated conditions of the modern world. This perspective predicts corresponding changes in the abundance of key trace elements and highlights their roles in governing primary productivity and the emergence of eukaryotes. That said, geological proxy studies in the intervening years revealed much more complexity to ocean redox evolution, while novel phylogenomic analyses reveal a deeper evolutionary antiquity for several redox-sensitive metalloenzymes. These discoveries require that geobiologists pay close attention to environmental variations in space as well as time. Moreover, increasing awareness that Precambrian trace metal abundances reflect large changes in sources and sinks, as well as in redox conditions, urges closer attention to tectonically influenced fluxes of major nutrients, especially phosphorus, as well as changing weathering fluxes through time. A new understanding of the relationships between Earth's physical history and metalloenzymes awaits. ▪ The bio-inorganic bridge connects biological and geological evolution through changes in trace metal availability over Earth's history. ▪ Combining sedimentary geochemistry and phylogenetics has revealed novel insights into metal utilization by the biosphere. ▪ Interdisciplinary approaches are increasingly used to link biosphere evolution with Earth's surface environments.

  PublisherDOI

• Reassessing the photochemical contribution to Archean Banded Iron Formations

  Chemical Geology · 2025-03-30 · 1 citations

  articleSenior author
  PublisherDOI

• Microbial N ₂ O reduction in sulfidic waters:Implications for Proterozoic oceans

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-07-03

  preprintOpen access

  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 (N 2 O), 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 N 2 O. 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 N 2 O reduction under sulfidic conditions. Leveraging publicly available environmental metatranscriptomes, we infer active N 2 O 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 N 2 O 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 0 complex. Using phylogenetics, we infer that early N 2 O reducers were probably anoxygenic phototrophs and performed N 2 O reduction as dark metabolism. Collectively, these observations suggest microbial N 2 O reduction occurs under euxinic conditions, implying that Proterozoic marine N 2 O 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.

  PublisherOA PDFDOI

• The Mysterious Ring: Diagnostic Challenges of an Unresolved Ring-enhancing Lesion

  American Journal of Respiratory and Critical Care Medicine · 2025-05-01

  article1st authorCorresponding

  Abstract Ring-enhancing lesions on head CT scans present a wide differential diagnosis, from infectious causes such as abscesses, toxoplasmosis, neurocysticercosis, tuberculosis, and fungal infections to neoplastic causes, including metastasis, glioblastoma, or primary CNS lymphoma. Infarcts, trauma, and demyelinating disease should also be considered. A thorough patient history can be invaluable in narrowing down these possibilities. Here, we present a challenging case of a patient whose complex history suggested multiple potential diagnoses. A 51-year-old Spanish-speaking female with hyperlipidemia and a recent 2-month history of left-sided Bell's palsy presented to the Emergency Department following a witnessed seizure-like event. The event was characterized by loss of consciousness, foaming at the mouth, ocular deviation, full-body tremors, and a postictal period lasting approximately 30 minutes. It was reported that the patient had been notably agitated for a week. Additional history revealed that she had moved from Mexico two years ago, owned two cats, had no known sick contacts, and had recently undergone a tooth extraction for which she was taking amoxicillin. On physical exam, a cystic lesion in the right groin was noted. Contrast-enhanced head CT showed a 2 x 1.3 cm ring-enhancing lesion in the left frontal cortex with extensive surrounding edema. Given her risk for recurrent seizures and potential respiratory compromise, she was admitted to the ICU. Her differential diagnosis included an abscess from dental infection, neurocysticercosis, Tuberculosis (given her geographic background), malignancy, or infarct. The patient underwent left frontoparietal craniotomy with resection of the lesion. Pathology confirmed metastatic adenocarcinoma with CK7 and TTF-1 positivity, raising suspicion for primary lung cancer. However, extensive imaging including a PET scan was unremarkable, leading to a diagnosis of metastatic adenocarcinoma of unknown primary origin. The risk of mortality in patients with an unknown primary cancer site is very high with a mean survival of 12.3±31.6 months. In this patient, the treatment plan was geared towards metastatic non-small cell carcinoma of the lung with carboplatin, Pemetrexed, and pembrolizumab. Patients with cancer of unknown primary (CUP) can frequently present to the ICU for different reasons including seizures where appropriate workup during their admission can help guide therapy. The FDA has approved some therapies when a molecular target is identified in a cancer, regardless of the primary site based on the type of genes that are expressed or if the mutational risk is elevated with more studies being conducted on molecular targeted therapy in CUP.

  PublisherDOI

• Revisiting ancient seawater molybdenum concentrations with mass balance models

  2025-01-01

  articleSenior author
  PublisherDOI

• Transient glacio-eustatic fall and its climato-environmental effects during the Frasnian-Famennian transition

  Global and Planetary Change · 2025-10-31 · 6 citations

  article
  PublisherDOI

• Take a Deep Breath: The Influence of Earth’s Deep Interior on the Emergence of an Aerobic Biosphere

  2025-01-01

  article1st authorCorresponding
  PublisherDOI

• Subaerial volcanism linked to contemporaneous ocean oxygenation 2.65 billion years ago

  2025-01-01

  article
  PublisherDOI

Recent grants

• Mercury Stable Isotopes as a Proxy of Photic Zone Euxinia

  NSF · $420k · 2020–2025

• Collaborative Research: Transition Metal Isotope Fractionation during Adsorption to Authigenic Oxides

  NSF · $300k · 2005–2009

• FESD Type I: The Dynamics of Earth System Oxygenation

  NSF · $4.8M · 2013–2020

• Collaborative Research: Ocean Redox Evolution at the Dawn of Animal Life: An Integrated Geological and Geochemical Study of the Ediacaran Yangtze Platform in South China

  NSF · $97k · 2008–2013

• Collaborative Research (UCR, OSU and ASU): Combined Fe-S Stable Isotopes in Modern Anoxic Environments and the Effect of Fe versus S Limitation

  NSF · $38k · 2006–2008

Frequent coauthors

• Timothy W. Lyons

  114 shared

• Stephen J. Romaniello

  101 shared

• Gwyneth W. Gordon

  Arizona State University

  96 shared

• Gail Lee Arnold

  The University of Texas at El Paso

  87 shared

• Roger Buick

  University of Washington

  81 shared

• Alan J. Kaufman

  79 shared

• Brian Kendall

  University of Waterloo

  77 shared

• Tais W. Dahl

  University of Copenhagen

  68 shared

Labs

• AnbarlabPI

Awards & honors

• Fellow of the American Geophysical Union (AGU)
• Fellow of the Geological Society of America (GSA)
• Fellow of the Geochemical Society
• Fellow of the European Association of Geochemistry
• Howard Hughes Medical Institute Professor