Project Design

What can we do?

There is research going on all over the world that is working on lowering methane production in cattle. Common approaches involve diet changes, such as feed additives, that indirectly change the microbiome. The efficiency of these approaches can be vastly improved by directly changing the microbiome of the cow with genetically engineered bacteria.

One way to do this is by using the powers of seaweed. Surprisingly, humans have been feeding seaweed to cows in coastal regions since the time of the ancient greeks.[1] Seaweed is now being studied as a food additive because it has been shown to reduce the amount of methane produced by cattle. The compound within seaweed that is responsible for reducing methane is bromoform and other related molecules such as bromochloromethane. Bromoform works by inhibiting the efficiency of the methyltransferase enzyme by reacting with the reduced vitamin B12 cofactor required for the second to last step of methanogenesis.

(I guess we still need a pic here???)

A study done by Australian scientists tested 20 different species of seaweed on methanogens found in the stomachs of cows. They discovered seaweed reduced methane production by up to 50 percent, depending on the amount administered. But methane reduction at notable levels required high doses of seaweed, almost 20 percent by weight of the sample. This worked fine in the lab, but outside of the lab this large percentage of seaweed would be difficult to implement and would likely have a negative effect on cow’s digestion.[2] On top of this the bromoform produced by the seaweed farms is known to act as a catalyst for recombination of ozone. In fact the ability to deplete ozone can be 10-20 times higher than the more well known molecule Freon-22. This is due to the high resistance of bromine to the termination reaction of ozone.[3]

(Yet another picture I don't have)

These observations led our team to directly change the microbiome of the cow with E.coli that produces bromoform instead of using seaweed to deliver the bromoform. To do this our team took the gene from the algae Corallina pilulifera that codes for the enzyme bromoperoxidase and cloned it into E.coli.

(Plasmid Map Yay)

The bacteria would be fed to the cow along with the necessary substrates as a food additive. Having the E.coli produce the bromoform inside the rumen of the cow gives us the power to control when the bromoform will be produced. We have designed a genetic circuit that will only express the gene for bromoperoxidase when the bacteria is inside the cow, and if it exits the cow a kill switch will be activated that will cause the bacteria to die. (link to killswitch description that will be placed somewhere else) This approach makes it so that the bromoform is only produced and used up within the rumen itself; allowing our ozone to remain intact.

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A proven dietary intervention strategy for reducing methane production in cattle is a nitrate supplement. The nitrate works by competing for hydrogen ions within the rumen that are usually used by methanogens. (Rumen pathway showing H+) Using these ions, the nitrate is quickly reduced to nitrite. Unfortunately, the conversion from nitrite to ammonia is a very slow process. This combination leads to a nitrite accumulation in the rumen and can cause serious health issues for the cattle or even death.

To avoid this issue, we are introducing bacteria that produce an enzyme called nitrite-reductase. This enzyme facilitates the conversion from nitrite to ammonia and is found naturally inside the rumen at low levels.