Scientists discover tiny rocket engines inside malaria parasites

Key Points

• The malaria parasite is packed with tiny crystals that spin nonstop, a strange behavior that puzzled scientists for decades.
• Researchers have now discovered that these crystals are powered by the breakdown of hydrogen peroxide, a reaction similar to the one used in rocket engines.
• This constant spinning may help the parasite survive by safely clearing toxic peroxide and managing harmful iron compounds.

Impact: This discovery could open the door to new malaria treatments and inspire advances in microscopic robot technology.

Spinning Crystals Inside Malaria Parasites

Every cell of the deadly malaria-causing parasite Plasmodium falciparum contains a tiny compartment packed with microscopic iron crystals. While the parasite is alive, these crystals are in constant motion. They whirl, bounce, and collide within their confined space like loose change shaking violently in a machine, moving so quickly and unpredictably that standard scientific tools have struggled to track them. When the parasite dies, however, the motion immediately stops.

These iron crystals have long been a key focus for antimalarial drugs, yet their unusual movement has puzzled scientists since it was first observed. "People don't talk about what they don't understand, and because the motion of these crystals is so mysterious and bizarre, it's been a blind spot for parasitology for decades," says Paul Sigala, PhD, associate professor of biochemistry in the Spencer Fox Eccles School of Medicine (SFESOM) at the University of Utah.

Now, Sigala's team has uncovered the mechanism behind this strange behavior. The crystals are driven by a chemical reaction similar to the one used to power rockets.

The discovery could point to new strategies for treating malaria and also offer insights for designing nanoscale robotic systems. The findings were published in PNAS.

Rocket-Like Chemistry Powers Crystal Motion

The researchers found that the crystals, made from an iron-containing compound called heme, are set in motion by the breakdown of hydrogen peroxide into water and oxygen. This reaction releases energy, providing the force needed to keep the crystals moving.

This type of propulsion is well known in aerospace engineering, where hydrogen peroxide is used as a fuel to launch spacecraft, but it had not previously been identified in a biological system. "This hydrogen peroxide decomposition has been used to power large-scale rockets," says Erica Hastings, PhD, postdoctoral fellow in biochemistry in the SFESOM. "But I don't think it has ever been observed in biological systems."

Hydrogen peroxide is abundant within the small compartment that houses the crystals, and the parasite naturally produces it as a byproduct. This made it a strong candidate as a potential energy source. Experiments confirmed that hydrogen peroxide alone could cause isolated crystals to spin, even outside the parasite.

When parasites were grown under low-oxygen conditions, which reduces hydrogen peroxide production, the crystals slowed to about half their usual speed, despite the parasites otherwise remaining healthy.

Why Crystal Motion May Help Parasites Survive

The researchers believe this constant motion may play a critical role in helping the parasite stay alive. One possible explanation involves hydrogen peroxide itself, which is highly toxic. The spinning crystals may help the parasite safely break down excess peroxide, reducing the risk of damage from harmful chemical reactions.

Sigala suggests another benefit. The movement may prevent the crystals from sticking together, which would limit their ability to store additional heme. If the crystals clump, they lose surface area needed to process more heme efficiently. By staying in motion, the parasite may be able to manage this process more effectively.

Implications for New Drugs and Nanotechnology

According to the researchers, these spinning crystals represent the first known example of a self-propelled metallic nanoparticle in biology. They suspect similar processes may exist elsewhere in nature.

The findings could help guide the development of advanced microscopic robots. "Nano-engineered self-propelling particles can be used for a variety of industrial and drug delivery applications, and we think there are potential insights that will come from these results," Sigala says.

There are also potential medical applications. "We think that the breakdown of hydrogen peroxide likely makes an important contribution to reducing cellular stress," Sigala says. "If there are ways to block the chemistry at the crystal surface, that alone might be sufficient to kill parasites."

Because this mechanism is very different from anything found in human cells, it presents an attractive target for new treatments. Drugs designed to interfere with this process are less likely to cause harmful side effects. "If we target a drug to an area that's very different from human cells, then it's probably not going to have extreme side effects," Hastings explains. "If we can define how this parasite is different from our bodies, it gives us access to new directions for medications."

The results are published in PNAS as "Chemical propulsion of hemozoin crystal motion in malaria parasites."

The work was supported by the National Institutes of Health (grant numbers R35GM133764, R21AI185746, R35GM14749, and T32AI055434), the Utah Center for Iron & Heme Disorders (grant number U54DK110858), the Price College of Engineering at the University of Utah, and the 3i Initiative at University of Utah Health. Content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.