Purple bacteria are tiny organisms that live in aquatic environments like the bottom of lakes and the colourful corals under the sea, using sunlight as their source of energy.

Their natural design seems the best structural solution for harvesting solar energy. Neil Johnson, a physicist at the University of Miami, thinks their cellular arrangement could be adapted for use in solar panels and other energy conversion devices to offer a more efficient way to garner energy from the sun.

“Purple bacteria were recently found to adopt different cell designs depending on light intensity,” says Johnson. “Our study develops a mathematical model to describe the designs it adopts and why, which could help direct design of future photoelectric devices.”

Solar energy arrives at the cell in “drops” of light called photons, which are captured by the light-gathering mechanism of bacteria present within a special structure called the photosynthetic membrane. Inside this membrane, light energy is converted into chemical energy to power all the functions of the cell.

The photosynthetic apparatus has two light harvesting complexes. The first captures the photons and funnels them to the second, called the reaction center (RC), where the solar energy is converted to chemical energy.

When the light reaches the RCs, they close for the time it takes the energy to be converted.

Johnson and his collaborators share their findings in a study entitled ‘Light-harvesting in bacteria exploits a critical interplay between transport and trapping dynamics,' published in the current edition of Physical Review Letters.

According to the study, purple bacteria adapt to different light intensities by changing the arrangement of the light harvesting mechanism, but not in the way one would think by intuition.

“One might assume that the more light the cell receives, the more open reaction centers it has,” says Johnson.

“However, that is not always the case, because with each new generation, purple bacteria create a design that balances the need to maximize the number of photons trapped and converted to chemical energy, and the need to protect the cell from an oversupply of energy that could damage it.”

Because these bacteria grow and repair themselves, the researchers hope this discovery can contribute to the work of scientists attempting to coat electronic devices with especially adapted photosynthetic bacteria, whose energy output could become part of the conventional electrical circuit, and guide the development of solar panels that can adapt to different light intensities, according to a University of Miami press release. — Our Bureau