A research team from the Institute of Agricultural Resources and Regional Planning (IARRP), Chinese Academy of Agricultural Sciences, has made new progress in understanding the evolution of cobamide (vitamin B12) biosynthesis. The team has, for the first time, developed a timeline linking microbial cobamide biosynthesis genes with the evolution of the organisms that carry them. The findings were published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS).

Cobalamide is an essential cofactor for most animals and many microorganisms, but only certain bacteria and archaea can produce it from scratch. As an important shared metabolic resource across different levels of the food web, cobalamide plays an important role in ecosystems and the evolution of life. However, the evolutionary history of its biosynthesis has remained poorly understood.

Using molecular clock analysis and phylogenetic approaches, the researchers estimated when key cobalamide biosynthesis genes and their microbial hosts emerged. The results suggest that the pathway evolved gradually. Some pathways involved in producing early precursors appeared before the emergence of organisms capable of producing complete cobamides, suggesting that cobamide-like compounds may have existed before the full biosynthetic pathway evolved.

The study estimated that the earliest anaerobic cobamide producers appeared about 2.46 billion years ago, represented by the genus Pelobacter. Aerobic producers emerged later, about 1.78 billion years ago, represented by the genus Kribbella. The emergence of aerobic producers occurred well after the Great Oxidation Event, highlighting the close relationship between microbial evolution and changes in Earth's atmosphere and oceans.

The findings provide a new timeline for understanding the role of cobamides in the evolution of global ecosystems. They also offer new insights into the interactions between microbial metabolism, Earth's environmental changes, and nutrient exchange between species.

Research Professor Wang Jichen of IARRP is the first author of the paper. Research Professor Ai Chao, Professor James M. Tiedje of Michigan State University, and Research Professor Ge Yuan of the Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, are co-corresponding authors.

The study was supported by the National Natural Science Foundation of China, the Fundamental Research Funds for Chinese Academy of Agricultural Sciences, the National Key Research and Development Program of China, and the US National Science Foundation.