Too much of something beneficial can be harmful. Living beings thrive on sunlight, with many relying on it for their survival, but they often steer clear of excessively bright light. Animals tend to seek shelter, humans take naps, and even plants have ways to protect themselves from too much light. But what about single-celled organisms that can’t move? Researchers have uncovered an unexpected solution.
Too much of something beneficial can be harmful. Living beings thrive on sunlight, with many relying on it for their survival, but they often steer clear of excessively bright light. Animals tend to seek shelter, humans take naps, and even plants have ways to protect themselves from too much light. But what about single-celled organisms that can’t move? Researchers at the University of Amsterdam have uncovered an unexpected solution.
Avoiding Bright Light
The scientific name of this organism is Pyrocystis lunula. While you might not be familiar with this single-celled algae, sailors and fishermen recognize it well: when P. lunula blooms, it can cause the ocean to shimmer with a blue glow. This alga is a type of dinoflagellate, which means it cannot move independently. Like plants, it harnesses sunlight through a component called a chloroplast to turn solar energy into usable chemical energy.
Plants have an ingenious tactic to cope with intense light: their chloroplasts rearrange within the cells to cover each other, allowing only the necessary light to be absorbed, thus preventing damage. The P. lunula alga, however, cannot adopt this strategy because its chloroplasts form a complex network, requiring a different method to shield itself from harsh light. Additionally, unlike animals and humans, it cannot simply relocate away from bright light. The way these organisms handle excessive light has puzzled scientists, but this mystery has now been unveiled.
A Flexible Chloroplast
Biophysicists Nico Schramma, Gloria Casas Canales, and Maziyar Jalaal developed a smart method to observe the behavior of P. lunula chloroplasts when exposed to light. By using microscopy, they recorded videos of the cell and its chloroplast, applying computer algorithms to map its complex form. This allowed them to track the chloroplast’s response under varying light colors and intensities.
Their findings revealed that while the chloroplast can’t escape from bright light, it can reduce its impact by shrinking. Under bright white light—similar to a sunny afternoon—the chloroplast shrank into a ball, decreasing its size by about 40% in just five minutes. Once the light shifted to low red light, the chloroplast returned to its original size and shape after half an hour.
The ability of the chloroplast to undergo these changes is attributed to a network of thin filaments. Together, these filaments create a material that can easily contract and expand uniformly in all directions. This is a crucial point because most natural structures do not exhibit this characteristic. For instance, if you step on a lemon, it will flatten significantly in height but expand in other directions, forming a disk-like shape while still retaining a large surface area. In contrast, P. lunula effectively avoids this typical behavior.
Nature’s Hoberman Sphere
The mechanism that allows the chloroplast to shrink uniformly resembles the design of a Hoberman sphere, which was patented by Chuck Hoberman in 1988 and is found in many children’s toys. This connection intertwines the physicists’ research with biology and mathematics, particularly in the field of topology, alongside materials design. Recent studies have focused on creating lab-made materials that replicate the surprising properties seen in both the Hoberman sphere and the chloroplast of P. lunula, exploring myriad applications, including ‘smart materials’ that dramatically change properties when subjected to external stimuli. Remarkably, the innovative solutions crafted by engineers and physicists are mirrored in nature itself.
Answering a single scientific question can lead to many more discoveries. This is likely the case regarding how P. lunula and similar dinoflagellates avoid overly bright light. This insight not only enhances our understanding of this tiny, luminous one-celled organism but also provides insights into natural structures, intricate mathematics, and valuable lessons for designing new materials ourselves.
