American researchers have identified two new species of the single-celled genus Paulinella. These shelled amoebae represent a rare phenomenon: a cell engulfed a photosynthetic bacterium and turned it into a chromatophore, the structure where photosynthesis takes place. The New York Times reported that this is only the second known case of such a transition in the history of life on Earth.
Before studying Paulinella, researchers thought nearly all complex photosynthetic life descended from a common ancestor that appeared about 1.6 billion years ago. A similar process in Paulinella took place roughly 100 million years ago — recent on an evolutionary timescale. The organisms therefore offer biologists a chance to examine the emergence of cellular complexity across a comparatively accessible span of time.
The team worked with limited resources. In the first half of 2025, Van Etten lost a National Science Foundation fellowship worth $60,000 a year amid research funding cuts. In the spring, she invited Willoughby to a makeshift laboratory in Nags Head, North Carolina. It was set up in a motel room costing $80 a night. The researchers improvised tools, including a pencil with a toothbrush bristle attached to its tip that Willoughby used as a bacteriological needle.
Van Etten had collected Paulinella samples from a local pond over four years. Willoughby noticed that the cells’ scales overlapped in different directions: clockwise in some samples and counterclockwise in others. The pattern suggested that the cells could belong to different species. The researchers then examined the samples with an electron microscope at a laboratory in Maine.
They extracted DNA from the cells’ chromatophores and sent the samples to Hwang Su Yoon, an evolutionary biologist at Sungkyunkwan University in South Korea. Yoon, who had previously identified another Paulinella species, confirmed that the samples represented two distinct new species. The finding adds to understanding of how symbiosis can reshape a cell and open new evolutionary possibilities.