Researchers from University of Michigan developed a microscope capable of mapping light energy migration patterns in photosynthetic bacteria
In photosynthesis, light hits the leaf or bacteria and a system of small light-harvesting antennae transfer it along through proteins to a reaction center. At the reaction center, light is trapped and turned into metabolic energy for the organisms. Now, a team of researchers led by Jennifer Ogilvie, U-M professor of physics and biophysics, captured the movement of this light energy through proteins in a cell. To achieve the breakthrough, the team developed a new microscope that uses a method called two-dimensional electronic spectroscopy. The microscope generates images of energy migration within proteins during photosynthesis and images an area the size of one-fifth of a human blood cell. Moreover, the microscope can capture events that take a period of one-quadrillionth of a second.
Two-dimensional spectroscopy reads the energy levels within a system in two ways. In the first step, it reads the wavelength of light, which is absorbed in a photosynthetic system. The second step includes measuring the wavelength of light that is detected within the system. This allows to track the energy as it flows through the organism. The instrument combines this method with a microscope and measures a signal from around a million times smaller volumes than before. Previous measurements imaged samples that were averaged over sections, which were a million times larger. When systems are averaged over large sections it enables to obscure the different ways in which energy might be moving within the same system.
The microscope enabled observation of colonies of photosynthetic purple bacterial cells. In previous experiments, researchers observed the purified parts of these types of cells. The team currently observed an intact cell system and analyzed the interaction between a complete system’s different components. Moreover, the team also studied bacteria, which were grown in high light conditions, low light conditions, and a mixture of both. The microscope tracked light emitted from the bacteria to show the change in the energy level structure and flow of energy through the system that depended on the bacteria’s light conditions. The research was published in Nature Communication on October 11, 2018.