Scientists discover bacteria that can use light to 'breathe' electricity
Did you know that bacteria in the natural world breathe by exhaling excess electrons, causing an intrinsic electrical grid? In a new study, Yale University researchers discovered that light could supercharge this electronic activity within biofilm bacteria, yielding an up to a 100-fold increase in electrical conductivity, according to a press release published by the institution earlier this month.
A photocurrent that lasts for hours
"The dramatic current increases in nanowires exposed to light show a stable and robust photocurrent that persists for hours," said senior author Nikhil Malvankar, associate professor of Molecular Biophysics and Biochemistry (MBB) at Yale's Microbial Sciences Institute on Yale's West Campus.
Scientists are now looking to make the most of this new discovery and find applications for it, such as eliminating biohazard waste and creating new renewable fuel sources.
It is common for living beings to breathe oxygen to get rid of excess electrons when converting nutrients into energy. However, soil bacteria living deep under oceans or buried underground over billions of years do not have access to this valuable oxygen.
They have therefore developed a way to respire by "breathing minerals” through tiny protein filaments called nanowires. The scientists found that when these types of bacteria were exposed to light, they produced a substantial and surprising increase in electrical current.
"Nobody knew how this happens," Malvankar said.
In the new study, the research team led by postdoctoral researcher Jens Neu and graduate student Catharine Shipps found that this process was powered by a metal-containing protein known as cytochrome OmcS (which makes up bacterial nanowires, the tools that bacteria use to breathe).
OmcS essentially acts as a natural photoconductor facilitating efficient electron transfer when biofilms are exposed to light.
A completely different form of photosynthesis
"It is a completely different form of photosynthesis," Malvankar said. "Here, light is accelerating breathing by bacteria due to rapid electron transfer between nanowires."
Now, Malvankar's lab is exploring how the discovery of this development could be used to spur growth in optoelectronics and even capture methane, helping in the fight against global warming.
These aren’t the only bacteria found to have useful properties. In August of 2018, a team of microbiologists from Washington State University found bacteria in Yellowstone National Park’s Heart Lake Geyser Basin that could “breathe” electricity by passing electrons to outside metals or minerals, using protruding wire-like hairs.
As the bacteria exchange electrons, they produce a stream of electricity that could possibly be harnessed for low-power applications. In theory, as long as the bacteria have fuel, they can continuously produce energy.
Then, in June of 2022, a team of researchers at Binghamton University found a way to power biobatteries for weeks by using three types of bacteria placed in separate chambers.
These discoveries indicate that nature can provide many solutions to some of today’s most insurmountable issues. All that is required is a little research and development in the right direction.
The findings were first published in the journal Nature Communications.
Light-induced microbial electron transfer has potential for efficient production of value-added chemicals, biofuels and biodegradable materials owing to diversified metabolic pathways. However, most microbes lack photoactive proteins and require synthetic photosensitizers that suffer from photocorrosion, photodegradation, cytotoxicity, and generation of photoexcited radicals that are harmful to cells, thus severely limiting the catalytic performance. Therefore, there is a pressing need for biocompatible photoconductive materials for efficient electronic interface between microbes and electrodes. Here we show that living biofilms of Geobacter sulfurreducens use nanowires of cytochrome OmcS as intrinsic photoconductors. Photoconductive atomic force microscopy shows up to 100-fold increase in photocurrent in purified individual nanowires. Photocurrents respond rapidly (<100 ms) to the excitation and persist reversibly for hours. Femtosecond transient absorption spectroscopy and quantum dynamics simulations reveal ultrafast (~200 fs) electron transfer between nanowire hemes upon photoexcitation, enhancing carrier density and mobility. Our work reveals a new class of natural photoconductors for whole-cell catalysis.
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