Scientists have recently reconstructed the evolutionary timeline of cobamide biosynthesis. They reveal that partial biosynthetic pathways predate complete cobamide producers, and that anaerobic producers emerged before aerobic ones, which is consistent with Earth's shifting redox conditions.

The study, published in PNAS on July 1, provides a new temporal framework for understanding cobamide ecology.

Cobamides are essential cofactors for animals and most microorganisms, but only a small number of prokaryotes are able to produce them. Acting as a kind of metabolites widely shared across different ecosystems, cobamides closely link microbial metabolism together and have played a key role in shaping life on Earth.

Earlier work has shown that cobamide producers serve as a key minority in microbial communities: their abundance follows a latitudinal gradient globally and correlates with microbial diversity, network complexity, and the expression of nitrogen, phosphorus, and sulfur cycling genes.

Yet the evolutionary history behind cobamide biosynthesis over Earth's deep time has remained unclear: when did these key cofactors that drive modern ecosystems first originate, and how did they respond to dramatic environmental shifts? A clear timeframe has so far been lacking.

A research team led by GE Yuan of the Research Center for Eco-Environmental Sciences of the Chinese Academy of Sciences, working with the Institute of Agricultural Resources and Regional Planning of the Chinese Academy of Agricultural Sciences, and Michigan State University in the US, combined molecular clock analysis with phylogenetic reconciliation analysis to address this question.

This approach accounted for the confounding effects of horizontal gene transfer—widespread among microbes—and allowed the team to reconstruct the evolutionary timeline of cobamide biosynthesis genes and producers.

The results show that the partial biosynthetic pathways for the tetrapyrrole precursor and the corrin ring originated earlier than cobamide producers with full biosynthetic capability. Consistent with Earth's redox history, the anaerobic de novo producers and corrin ring producers emerged first (Pelobacter, ~2,458 Mya), and the Great Oxidation Event postdated the emergence of aerobic producers (Kribbella, ~1,784 Mya).

According to the researchers, the study reveals the chronological evolution of cobamide biosynthesis—a process that has greatly reshaped the global ecological framework and molded the current biosphere. The findings offer a time‑scale framework for understanding the ecological and evolutionary roles of cobamides in modern ecosystems, and provide guidance for exploring cross‑species feeding interactions and the origins of Earth's diverse life forms.