Not all bacteria are harmful, and some have proven to be quite useful. It turns out that they can do all kinds of things! To name a few, scientists have been using bacteria to generate electricity, produce graphene, turn sunlight into chemicals, detect arsenic, mop up oil spills, eat plastic waste, and even find tumors.
Biohybrid Batteries
Some living organisms generate electricity. The phenomenon is known as bioelectrogenesis. Bacteria are among these organisms, and in the quest for smarter alternatives to energy, scientists have turned to a species of electrical bacteria known as exoelectrogens. This family of microbes produces electrons and shuffles them across their outer membrane. The ability makes them a candidate for living fuel cells and living batteries.
Researchers at Karlsruhe Institute of Technology (KIT) figured out how to capture and collect the electrons shed by the microbes. They managed to pull this off by creating a “biohybrid” system which consists primarily of a hydrogel – made of carbon nanotubes and silica nanoparticles – that can support the bacteria with a nutrient-loaded culture medium while effectively collecting their energy.
Such a battery would be non-toxic to the environment if it ended up in a landfill or elsewhere once it reached the end of its life-cycle.
Graphene Production
A team of scientists from the University of Rochester used a bacterium called Shewanella to produce large quantities of thinner, more stable graphene. They filled a beaker with graphene oxide (made from shredded graphite) and Shewanella and let it sit overnight. By morning the bacteria had reduced the graphene oxide to a graphene material.
Prof Anne S Meyer, who led the study, said:
Graphene oxide is easy to produce, but it is not very conducive due to all of the oxygen groups in it. The bacteria remove most of the oxygen groups, which turns it into a conductive material.
The bacterially produced graphene material could be used to make faster and more efficient circuit boards, computer keyboards, or small wires like the ones used to defrost car windshields. It could also be used as conductive ink that can be applied to nontraditional materials such as fabrics.
Chemicals From Sunlight
When nonphotosynthetic bacterium (Moorella thermoacetica) “breathe,” they convert carbon dioxide into acetic acid – a useful compound involved in the making of several valuable things such as polymers, fuels, pharmaceuticals, and commodity chemicals. A pair of chemists, Kelsey Sakimoto and Peidong Yang, developed a method that turns the microbes into efficient solar collectors to convert CO2 into acetic acid, which is then consumed by other bacteria that produce useful chemicals and fuels.
The process is self-regenerating and self-replicating, meaning it’s a zero-waste technology.
Arsenic Detection
Millions of people worldwide get cancer or die due to drinking arsenic-contaminated water, according to Unicef. To provide a solution, a team of scientists from the University of Edinburgh developed a low-cost biosensor that uses bacteria to detect unsafe levels of arsenic in drinking water instantly. They genetically engineered the bacteria to fluoresce in the presence of arsenic. The device can then be attached to a smartphone, which displays the level of contamination shown as easy-to-interpret patterns, similar to volume bars.
Dr. Baojun Wang, one of the scientists involved in the research, said:
We tested out sensors with samples from wells in a village in Bangladesh. The arsenic level reported by the sensors was consistent with lab-based standard tests, demonstrating the device’s potential as a simple low-cost-use monitoring tool.
The researchers are now working on applying the approach to detect other environmental toxins, locate landmines, and diagnose disease.
Cleaning Up Oil Spills
Many species of bacteria consume oil compounds as their fuel source. Scientists realized this during a catastrophic BP oil spill in the Gulf of Mexico in 2010. If it weren’t for the microbes, that spill would have been much worse.
Chris Reddy, a biogeochemist of the Woods Hole Oceanographic Institution said:
The microbes did a spectacular job of eating a lot of natural gas. The relatively small hydrocarbon molecules in natural gas are the easiest for microorganisms to eat. The rate and capacity is a mind-boggling testament to microbes.
Fighting Plastic Pollution
There is a species of bacterium that eats PET plastic. Furthermore, the way it breaks down the plastic can be harnessed as a recycling process. The bacterium uses two enzymes to break the plastic down into two components that can then be used to synthesize new PET plastic. The Japanese scientists who discovered this in 2016 are now working on optimizing the enzymes to improve the PET recycling method and make it more efficient.
Tumor Detection
MIT scientists genetically modified bacteria in 2015 to detect tumors in mice by producing a luminescent signal when it encountered cancer. They tested the harmless strain of bacteria in animal models, and it worked. The luminescence could even be detected in urine and was able to detect tumors as small as one square millimeter.
