The biological microcosm has an outstanding number of micro-organisms that hold untapped functions that offer opportunities for exploration and harnessing. Microbial species perform incredible tasks to self-sustain themselves and if we can exploit these self-sufficient micro-organisms, we can use their natural properties to enhance our lives. Among the prolific bacterial species of scientific interest, cyanobacteria possess a unique ability for photosynthetic energy conversion.
Cyanobacteria make their own food from sunlight using photosynthesis, the same process that all plants use to make their food. During photosynthesis the cyanobacteria split water molecules, releasing electrons with an efficiency of 100%. Once enough electrons build up in one place, they can create an electric current.
The researchers needed to group a lot of these bacteria together to create as much electricity as possible. The only problem was that bacteria doesn’t survive long on artificial surfaces. The solution was to harvest their products from the surface of a living fungus - i.e. a mushroom. The team chose mushrooms because mushrooms naturally host communities of bacteria and other microbes and they were easy to source. Water molecules required for photosynthesis can be delivered to the cyanobacteria via capillary action of the mushroom’s hyphae in its porous structure. The relationship can be described as symbiotic because the mushroom lacks the ability to perform photosynthesis due to the lack of chlorophyll, and the intertwined cyanobacterial colonies can impart photosynthesis functionality to the mushroom.
They used 3D printing to interweave the cyanobacteria onto the mushroom. However, this posed a problem because 3D printers are designed to print on flat surfaces, but mushroom caps are curved. The researchers spent three months writing a computer code to solve the problem, and finally, a program was made to print the ink onto the mushroom’s pileus.
The researchers printed two inks onto the mushrooms – a green ink made of cyanobacteria and a black ink made of graphene nanoribbons. Graphene is a thin sheet of carbon atoms that is excellent at conducting electricity. The combination of these two inks allowed the electrons to flow into the graphene and an electric current was created.
This experiment is an excellent proof of concept in bacterial nanobiotics and this is a huge step forward in science and green electronics. Green electronics refers to eco-friendly technology that limits waste. The researchers confirmed an idea is possible and that their idea worked, even though it’s not yet ready for practical use. It is not yet ready for powering our electricity just yet because the team generated a 70 nanoamp current which is a 7-millionth the current needed to power a lightbulb. However, they overcame many challenges such as getting the microbes to grow on the mushroom and figuring out how to print onto the mushrooms curved surface.
Micro-organisms that possess such photosynthetic capabilities embrace potential applications towards advancements in bacteriology, energy harvesting, genetic engineering and bacterial nanobiotics.