Proteomic assessment of caffeine effects on coral symbionts.

Caffeine isthe mostwidely consumed and excreted psychoactive drug in the world. It is a ubiquitous tracer of urban wastewater, but its ecological effects are notwell understood. We hypothesized that caffeine exposure is associated with coral bleaching. Here we report the effects of caffeine on four species of coral algae endosymbionts belonging to three widely distributed clades: Clade A Symbiodinium microadriaticum (A), Clade B Symbiodinium sp. from Aiptasia pallida (B6), Clade B Symbiodinium sp. from Pseudoterogorgia bipinnata (B7), and Clade C Symbiodinium goreaui (C). To assess the effect of caffeine on algal physiology we used two-dimensional polyacrylamide gel electrophoresis and peptide mass spectrometry to identify protein sensitive to caffeine exposure. The results show several upregulated and several downregulated polypeptides in all algae species tested. The heat-shock proteins are among the commonly affected proteins, suggesting that caffeine exposure associated with sewage discharge into natural waters may exacerbate the effects of stress from other environmental factors such as changes in ocean temperature and pH.