Guanine crystal formation by the unicellular organism Phacotus lenticularis is part of a cellular stress response.

ABSTRACT: Organic crystals, and in particular guanine crystals, are widely used by multicellular organisms for manipulating light and producing structural colors. Many single celled eukaryotic organisms also produce organic crystals, and guanine is the most abundant type produced. Their functions are thought to be related to the fact that guanine is nitrogen rich. Here we studied a freshwater unicellular eukaryotic alga, Phacotus lenticularis, and found that when the growth medium is depleted in phosphorus, the alga stops reproducing and produces intracellular birefringent particles inside vesicles. Cryo-SEM showed that these particles are faceted and are located within membranes inside the cell. Using Raman spectroscopy, we showed that these particles are β-guanine crystals. 3D tomograms produced u

SUBMITTER: Shaked N 

PROVIDER: S-EPMC11819609 | biostudies-literature | 2025

REPOSITORIES: biostudies-literature