In studying the Antarctic psychrophile Chlamydomonas sp. UWO 241, one topic of particular interest has been the novel mechanisms it uses to deal with stress and maintain photosynthetic capability in its environment. Previous work established that UWO 241 uses constitutively upregulated photosystem-I driven cyclic electron flow to deal with high salinity stress. The goal of this project was to determine whether cyclic electron flow also plays a role in dealing with other long-term environmental stresses such as low temperature and high light. UWO 24 was grown under control conditions (growth temperature: 8℃, growth light: 50 µmol photons m-2s-1), and two different stressors: 1) low temperature (2℃, 50 µmol photons m-2s-1), and 2) high light (8℃, 250 µmol photons m-2s-1 ). Culture growth was monitored by optical density . Photosystem II activity was monitored using a Walz Dual-PAM instrument using chlorophyll a fluorescence. Photosystem I activity and cyclic electron flow were measured on the Dual-PAM using absorbance changes at 820 nm . It was found that cyclic electron flow was faster relative to control conditions in both cultures grown under temperature and light stress, which suggests thatUWO 241 uses cyclic electron flow as a general strategy to survive stress. This opens up future research questions, including whether a Photosystem I protein supercomplex is formed in UWO 241 under these conditions. Another avenue of investigation is determining whether becoming adapted to long-term light or temperature stress can make cultures more resistant to other short-term stressors. Conducting this research allows the opportunity to learn critical skills needed for scientific inquiry, including problem solving and data analysis. It also involves becoming familiar with a toolbox of specific procedures for studying microbial physiology and photosynthesis, which can be built on in future research projects.
Author: Susanna D’Silva
Faculty Advisor: Rachael Morgan-Kiss, Department of Microbiology
Graduate Student Advisors: Isha Kalra, Abby Mills
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