University professors find glass shells aid tiny organisms with photosynthesis

People may not want to live in glass houses, but single-celled organisms have found a use for their own glass shell.

In their study recently published in the journal Science, University geosciences professors Allen Milligan and Francois Morel showed that the diatoms' natural but ornate glass coverings contain enzymes that accelerate the photosynthesis reaction, which is essential to the organisms' survival.

More significantly, however, the study suggests these glass dwellings contribute enormously to the level of oxygen in Earth's atmosphere.

"We never knew if the glass could do anything [before]," Milligan said. "This is the first time anyone's found a useful reason [for the diatoms] to have the glass."

A form of algae, diatoms abound in the oceans, representing one quarter of all photosynthesis on Earth. Photosynthesis converts sunlight and carbon dioxide into glucose and oxygen. In the diatom's shell, silicon and sodium bicarbonate — baking soda — allow carbon dioxide to be consumed at a faster rate.

Forty to 60 million years ago, plant life faced a challenge because of low carbon dioxide levels. Photosynthesis was extremely difficult with scant amounts of carbon dioxide, one of its key ingredients.

According to Milligan and Morel's findings, diatoms enveloped themselves in glass, which helped to concentrate the carbon dioxide. Due to of the success of this development, diatoms multiplied and now to reduce carbon dioxide levels in the atmosphere.

"They are among the most successful organisms on Earth," said Morel, director of the Princeton Environmental Institute, in a statement.

The implications of the study pertain to a number of scientific disciplines. For example, understanding the relationship between diatom population and carbon dioxide concentration could greatly influence the ongoing analysis of the greenhouse effect.

Milligan also speculates that the role of silicon in diatom shells might relate to the function of silicon in the human body.

Silicon, a non-metallic element found in glass and bones, functions as a buffer inside the diatom's shell, keeping the pH level within a particular range. The diatom's glass case is the first example in biology of a solid substance that changes acid-base chemistry in this way.

While Morel's group has been investigating properties of diatoms for the past three years, scientists have wondered about the elaborate glass cases of diatoms since the introduction of microscopes in the 1600s.

Get the best of the ‘Prince’ delivered straight to your inbox. Subscribe now »

Now, Milligan and Morel have shown that the ornate designs in the shells also contribute to the facilitation of photosynthesis. The numerous pores and indentations allow for more of the glass to be exposed to water.

Thus, Morel said, "their beauty might in fact be related to their function."