BY JENNA GALLEGOS
THE hot new gene editing technique CRISPR has been making headlines for its potential to treat or prevent diseases. But medicine isn’t the only science where CRISPR is opening doors. This powerful genetic engineering tool is already helping scientists develop technologies to protect or repair the environment from human harm.
CRISPR: Not just cut and paste
You’ve probably heard that CRISPR allows scientists to edit genes very specifically, cutting and pasting at targeted sites. But this fundamental ability makes CRISPR a great tool for all sorts of complex genetic engineering. Using CRISPR, scientists can:
Edit many genes simultaneously.
Deliver proteins to particular genes in order to fine tune their activity.Make “markerless” changes. Older methods of genetic engineering were so inefficient, a gene called a marker often had to be inserted in order to identify the cells that were successfully edited.
These traits make CRISPR an invaluable tool for tweaking multipart genetic processes or building whole new pathways. In the CRISPR age of genetic engineering, complex environmental challenges will become a lot more feasible.
Plants, algae and cyanobacteria naturally turn carbon dioxide and sunlight into byproducts. The sugars, fats or alcohols produced are all potential alternative fuel sources. Scientists have shown that CRISPR works in certain species of cyanobacteria,algae and several key biofuel crops.
Bacteria can also break down plant cell walls into biofuels, and certain species can generate fuel precursors from waste products, such as methane from landfills. CRISPR has been applied to key bacteria that naturally contain part of the pathways necessary for producing biofuels.
Getting these organisms to grow happily while churning out fuel precursors is not trivial. The precision and efficiency of CRISPR allows for the type of complex genetic engineering
that could help make biofuels a viable alternative.
Fuels aren’t the only petroleum-based products that could someday be replaced by biology. Certain yeast and bacteria naturally make compounds similar to plastics. CRISPR could help make these compounds more abundant and easier to extract.
Microbes could also be engineered to help degrade plastics. Certain species of bacteria and fungi have evolved naturally to degrade compounds found in plastics. CRISPR could be employed to increase the activity of the genetic pathways involved. Scientists have already begun applying CRISPR to microbes that are good candidates for producing and degrading plastics.
There are many other types of bioremediation where CRISPR might prove handy. For instance, microbes or plants could be engineered to more efficiently take up heavy metals, clean up oil spills or improve wastewater treatment.
Biosensing goes hand in hand with bioremediation. In biosensing, probes or sensors detect the presence of certain molecules.
Plants and microbes act as natural biosensors, responding to chemicals in their environment. These detection and response pathways can be reengineered.
Work to engineer plants that detect and signal the presence of bioweapons and pathogens is ongoing. In the same way, plants or other organisms could detect environmental pollutants.
Once a pollutant is identified, the biosensor could even trigger a bioremediation pathway. CRISPR has made this type of complex multi-gene network engineering in plants much more feasible.
5. GREENHOUSE GAS EMISSIONS
In addition to decreasing our dependence on fossil fuels, CRISPR could help address biological sources of greenhouse gas emissions. Burning fossil fuels releases a lot of carbon dioxide into the environment. But atmospheric methane, a far more potent greenhouse gas, is thought to come mainly from bacteria.
Some of these bacteria come from natural sources like wetlands, others live in the guts of cows and in flooded rice fields. By tweaking the genetics of cows or the grass they eat, cattle ranches in the future might produce fewer belches per beef. Rice can also be engineered to curb bacterial growth and to help keep more methane in the ground. CRISPR could facilitate these efforts by improving the speed and accuracy of the genetic engineering process.
6. PESTICIDE REDUCTION
Using CRISPR, plants can be engineered to resist threats such as insects or diseases. For instance, CRISPR has already helped generate virus-resistant cucumbers and fungus-resistant rice. In some cases pesticides are the only other way to keep these threats from destroying our food supply.
7. EFFICIENT WATER USE
Agriculture is estimated to use up to 70 percent of the world’s fresh water resources. Several studies already have found that CRISPR can help make plants more water-efficient or improve our understanding of what genes are important for drought tolerance.
8. NITROGEN FIXATION
Nitrogen runoff is another agriculturally relevant environmental problem. Plants cannot directly take up most forms of nitrogen in the soil. Certain plants such as beans and peas develop associations with bacteria that help make soil nitrogen more available to the plant. Others rely on added nitrogen in the form of manure or synthetic fertiliser.
Excess added nitrogen can run off fields and contaminate water sources, leading to aquatic dead zones. Many current projects are underway using CRISPR to engineer plants or bacteria for improved nitrogen fixation.
9. INVASIVE SPECIES
Animal or plant species that are carried from one region to another can wreak havoc on native ecosystems. There are several different genetic strategies for eradicating invasive species. These include “gene drives,” in which a gene that reduces fitness is spread through the population. Several CRISPR-based gene drive strategies have already been described by researchers. CRISPR could also be applied to “self-limiting” technologies, which act like a genetic form of birth control.
10. FOOD WASTE
It takes a lot of fresh water and fossil fuels to grow and transport food. When food spoils before reaching our plates, the inputs it took to grow them are wasted. Genetic engineering can preserve the shelf life of foods in many ways. For instance, injury from insects helps bacteria and fungus grow and spread through produce. CRISPR could indirectly help food waste by reducing crop losses due to insects and pathogens.
CRISPR has already proven handy in preventing browning in cut or bruised mushrooms. The same strategy will likely soon be expanded to many other crops.
In order for CRISPR to make waves in environmental science, we’ll have to tackle the ethical ramifications of these technologies. Scientists are working hard to model risk scenarios and minimise potential issues. As with any new technology, it will be important to discuss the risks and benefits of using CRISPR to solve environmental problems. – Cornell Alliance for Science