Presentation Title

Trading Manganese for Water in Photosynthesis

Faculty Mentor

Hope Johnson

Start Date

23-11-2019 10:00 AM

End Date

23-11-2019 10:45 AM

Location

105

Session

poster 3

Type of Presentation

Poster

Subject Area

biological_agricultural_sciences

Abstract

The development of oxygen producing photosynthesis is arguably one of the most important events in Earth’s life history. Not much is known about how photosynthesis evolved to produce oxygen; however, manganese (Mn) oxidation is proposed to be an evolutionary step that transitioned anoxygenic photosynthesis to produce oxygen. The research here focuses on detecting Mn oxidation in the modern cyanobacterial strain Synechocystis sp. PCC 6803. We hypothesize that Mn(II) is oxidized by photosystem II (PSII) and electrons are transferred into the electron transport chain, the same way a water molecule’s electrons are used in oxygenic photosynthesis. Therefore, we expected oxygen production would decrease if cells are also oxidizing Mn by PSII. Concentrated cells were incubated in the light and oxygen production was continuously measured using an oxygen electrode. Mn treated samples with oxidized Mn(II) (as Mn(III)) was measured at discrete time points by a spectrophotometric assay with leucoberbelin blue (LBB). Oxygen production was inconsistent between the control and Mn treated samples. Additionally, the electron transfer from Mn did not seem to compensate for the difference in the total electron transfer for oxygen production between sample types. Although cells oxidized Mn, oxygen production did not decrease. Future experiments include utilizing non-oxygen producing PSII mutants to detect electron flow through PSII during Mn oxidation.

This document is currently not available here.

Share

COinS
 
Nov 23rd, 10:00 AM Nov 23rd, 10:45 AM

Trading Manganese for Water in Photosynthesis

105

The development of oxygen producing photosynthesis is arguably one of the most important events in Earth’s life history. Not much is known about how photosynthesis evolved to produce oxygen; however, manganese (Mn) oxidation is proposed to be an evolutionary step that transitioned anoxygenic photosynthesis to produce oxygen. The research here focuses on detecting Mn oxidation in the modern cyanobacterial strain Synechocystis sp. PCC 6803. We hypothesize that Mn(II) is oxidized by photosystem II (PSII) and electrons are transferred into the electron transport chain, the same way a water molecule’s electrons are used in oxygenic photosynthesis. Therefore, we expected oxygen production would decrease if cells are also oxidizing Mn by PSII. Concentrated cells were incubated in the light and oxygen production was continuously measured using an oxygen electrode. Mn treated samples with oxidized Mn(II) (as Mn(III)) was measured at discrete time points by a spectrophotometric assay with leucoberbelin blue (LBB). Oxygen production was inconsistent between the control and Mn treated samples. Additionally, the electron transfer from Mn did not seem to compensate for the difference in the total electron transfer for oxygen production between sample types. Although cells oxidized Mn, oxygen production did not decrease. Future experiments include utilizing non-oxygen producing PSII mutants to detect electron flow through PSII during Mn oxidation.