First near-atomic map of babesiosis parasite's ribosome unveiled

A disease on the rise

Babesia divergens is a tick-borne pathogen prevalent in Europe. It causes significant livestock loss and sometimes severe disease, even death, in humans — especially people with compromised immune systems. The disease can spread through donated blood and from pregnant mothers to their babies, and many different Babesia species infect humans.

In the United States, cases rose by 9% per year from 2015 to 2022. Blacklegged ticks carrying the related Babesia microti have expanded their geographic range and lengthened their biting season as temperatures warm.

Léger-Abraham initially wanted to image ribosomes from Plasmodium, the malaria parasite, because of its global health toll. She chose Babesia divergens instead for a practical reason: it is easy to cultivate and yields the larger quantities of material that high-resolution structural studies demand.

How the team did it

The researchers used cryo-electron microscopy, or cryo-EM. In this technique, many copies of ribosome particles are rapidly frozen in a thin layer of vitreous ice and imaged from different angles; computers then align and combine the 2D views into a 3D model. Data were collected at the Harvard Cryo-EM Center for Structural Biology at HMS.

The resulting map shows the intricate interactions between residues of ribosomal proteins and ribonucleotides of the rRNA — the most detailed map of its kind for any apicomplexan parasite. It is sharp enough to reveal chemical modifications of the ribosome that may tune its function. Think of RNA as a language: these marks work like punctuation and accents, subtly shifting the meaning of the code.

The 120 marks, known as rRNA epitranscriptomic modifications, can tweak how the ribosome assembles and how proteins get made. Most sit in regions known to carry out important work, suggesting they are biologically meaningful and, in some cases, potential drug targets, the authors said.

The team also detected variation between individual ribosomes. Babesia passes through very different environments during its life cycle, and differences in rRNA modifications from one ribosome to another could offer clues to how the parasite adapts to diverse hosts.

What comes next?

The caveats are real. The researchers have not yet run follow-up experiments to determine what the chemical marks actually do, or whether they directly affect the parasite's life cycle. "Now that we have a complete list, we can figure out which ones are crucial for infection and/or survival. After that, we can figure out if any of those rRNA modifications are good targets for drug development," Léger-Abraham said.

Another next step is imaging the ribosome of the apicoplast, an organelle that performs essential metabolic tasks for Babesia and its relatives. It arose when an ancestor of these protozoa engulfed a blue-green alga and, instead of digesting it, learned to live with it. The apicoplast keeps its own DNA and its own ribosomes. While Babesia's main cytoplasmic ribosome resembles human ones, apicoplast ribosomes are closer to bacterial ribosomes — making them a potentially rich target for antibiotic-like drugs with minimal side effects.

Léger-Abraham also stressed the value of curiosity-driven research. "There's so much data, so much biology, so much information waiting to be revealed that we can use to improve human health," she said.

The paper is Cristina Gutierrez-Vargas et al., "Ribosomal architecture and rRNA modification landscape in the tick-borne parasite Babesia divergens," Nature Communications (2026).

The takeaway: a sharper picture of the parasite's protein factory gives drug hunters a parts list — and half of the newly found marks are unexplored territory.