What if the bacteria in your gut could produce a cleaner fuel for cars and trucks? It turns out, with a little fiddling, they can!

Researchers in the United Kingdom took the common gut bacteria, Escherichia coli, and added genes from the camphor tree, blue-green algae and two other bacteria (Photorhabdus luminescens and Bacillus subtilis). The addition of genes from blue-green algae and the two bacteria allow E.coli to make hydrocarbons from fatty acids; the camphor tree genes makes the hydrocarbons a similar length to those found in fossil fuels.

So when the scientists fed the glucose from plants to the souped-up E. coli, the gut bacteria turned the food into a fuel very similar to the diesel fuel derived from crude oil. Voilà! Gut Fuel!

The remarkable thing about this biofuel—a fuel derived directly from living matter— is that it can be pumped into current gas tanks with absolutely no modifications. Most other biofuels require vehicle owners to adjust their engines to operate with the more sustainable liquids, or involve mixing the biofuel with traditional fossil fuels.

John Love, of the University of Exeter, says this was a priority. “Producing a commercial biofuel that can be used without needing to modify vehicles has been the goal of this project from the outset. Replacing conventional diesel with a carbon neutral biofuel in commercial volumes would be a tremendous step towards meeting our target of an 80% reduction in greenhouse gas emissions by 2050.”

Well, not so fast… Producing this new biofuel en masse will take a lot more work. The scientists are hoping to wean the E. coli off plants and use animal or agriculture waste instead. Otherwise, they foresee a similar problem for their new biofuel as that faced by current biofuels—it’s tough to argue that we should be devoting our farmlands to growing fuels over growing food.

In addition, E. coli hydrocarbons cost more to produce than fossil fuel hydrocarbons. At least on paper. But in the long run, probably not.

The research is published in this week’s Proceedings of the National Academy of Sciences.

Image: Marian Littlejohn

The experiment demonstrates natural selection at work. And because samples are frozen and available for later study, when something new emerges, scientists can go back to earlier generations to look for the steps that happened along the way.

Last month, Zachary Blount, Lenski and colleagues published a paper in Nature detailing a new evolution in E. coli—the ability to eat citrate.

Shannon Bennett, associate curator of the Academy’s Microbiology department, explains why this is so unusual.

E. coli doesn’t normally eat citrate unless it is desperate (there’s no glucose, no oxygen). But these E. coli did evolve the ability to eat citrate, in fact thrive on it, in the presence of both oxygen and glucose.

They were able to evolve to do this when certain individuals made mistakes and copied their citrate gene (which usually is turned on only under oxygen-poor conditions) to a different spot in the genome near a switch point that turns on in the presence of oxygen.

Blount was able to trace this new trait through generations and uncover a three-step process in which the bacteria developed this new ability.

The first stage was potentiation, when the E. coli accumulated at least two mutations that set the stage for later events (see Shannon’s explanation above). The second step, actualization, is when the bacteria first began eating citrate, but only just barely nibbling at it. The final stage, refinement, involved mutations that greatly improved the initially weak function. This allowed the citrate eaters to wolf down their new food source and to become dominant in the population.

“We were particularly excited about the actualization stage,” Blount says. “The actual mutation involved is quite complex. It re-arranged part of the bacteria’s DNA, making a new regulatory module that had not existed before. This new module causes the production of a protein that allows the bacteria to bring citrate into the cell when oxygen is present. That is a new trick for E. coli.

“It wasn’t a typical mutation at all, where just one base-pair, one letter, in the genome is changed,” he continues. “Instead, part of the genome was copied so that two chunks of DNA were stitched together in a new way. One chunk encoded a protein to get citrate into the cell, and the other chunk caused that protein to be expressed.”

Shannon explains why this study is so exciting:

This study is cool because it shows many of the important mechanisms in evolution, namely gene duplication and gene regulation (turning genes on and off at different times). It all went on in a series of test tubes, so it’s “artificial” evolution, but what’s nice about that is, they were able to freeze samples down at early time points through to the present, to trace the path of evolution, and that they used a model organism, Escherichia coli, that evolves very quickly (not as quick as viruses, but much faster that vertebrates). My work takes advantage of the same historical sampling and evolutionary speed, only I’ve focused on “natural” experiments in the viruses I work on.

We often think of tires being made of rubber, but in fact, large tire manufacturers use isoprene to produce synthetic rubber for use in tires. And isoprene is generally made of crude oil—about seven gallons of it goes into each tire manufactured and approximately one billion tires are produced each year worldwide.  You do the math!  That’s a lot of crude…

A biotech company called Genencor, with offices in Palo Alto, has developed a more sustainable way to manufacture isoprene, using bacteria to convert biomass sugars into isoprene.

The process can use sugars derived from plant products such as sugar cane, corn, corn cobs, and switchgrass. According to an article in today’s New Scientist, the researchers “took gene sequences for an enzyme that allows vines and trees like kudzu and poplar to synthesise isoprene, and inserted them into strains of the bacterium Escherichia coli and a fungus. The genetically engineered micro-organisms were able to feed on (the) plant products…  to produce isoprene gas, which was then collected, condensed and purified.”

They’re currently trying to determine which combination of micro-organism and plant product works most effectively. Goodyear, the tire giant, is partnering on the project and hopes to have a tire from the BioIsoprene available to consumers within the next five years.

Unfortunately the BioIsoprene is not biodegradable. And, as we’ve seen before with products like biofuels, land to grow the feedstock does not come cheaply—think about the food vs fuel argument and deforestation.

A roll in the right direction, but not all the way there yet…

Creative Commons image by otherthings