Scientists at the Weizmann Institute have developed bacteria nourished only from carbon dioxide. The bacteria build their entire biomass from carbon in the air. In the future, such bacteria could help reduce the concentration of greenhouse gases in the atmosphere, thereby relieving global warming. The ambition of the researchers is to develop a closed circle of generating biological fuel using the bacteria without harming the environment. This potential development, however, is far from being realized at present. The bacteria cannot be deliberately released into the atmosphere, because they are incapable of surviving outside the laboratory.
The bacteria in the laboratory of Prof. Ron Milo were weaned completely from sugar, and now subsist entirely on a diet of CO2, which they obtain from their surroundings, so that they live off the air and build their entire mass from carbon in the atmosphere.
A decade of design, genetic engineering, and an accelerated laboratory version of evolution were needed in order to achieve these results, which were published in "Cell," a scientific periodical. This achievement has many future possibilities for development of new environmentally friendly technologies that will help reduce the concentration of greenhouse gases in the atmosphere and combat global warming.
All life on earth is based in one way or another on fixation of carbon through photosynthesis: the ability of certain plants, algae, and bacteria to absorb carbon dioxide from their surroundings and convert it, using solar energy, into the sugar used as an essential material for life processes. These living entities, which are at the bottom of the food chain, are called autotrophs or producers. At the top of the food chain are beings that work in the other direction - they consume sugar generated by the producers and release carbon dioxide into their surroundings. These beings are called heterotrophs or consumers. They include many bacteria, fungi, and animals, including human beings. Can a being at the top of the food chain that consumes sugar and releases carbon dioxide be reprogrammed to use carbon dioxide from the environment and to produce the sugar it needs to build its body? That is precisely the challenge that Milo's research group in the Weizmann Institute Plant and Environmental Sciences Department sought to take up.
The researchers, led by Dr. Shmuel Gleizer, decided to try applying the no-sugar challenge to E. coli bacteria. First, they mapped the genes essential to the process of fixating carbon and attached several of them to the genome of the bacteria in their laboratory. In addition, in order to replace the role of solar energy in photosynthesis, they inserted a gene into the bacteria that enabled them to derive energy from an available material called formate. The scientists sequenced the genome of the bacteria weaned from sugar in order to identify the mutations that changed their nutritional habits. Unexpectedly, they found relatively few genetic changes - a few changes involving synchronization of the carbon fixation process, a few changes involving transcription - regulating how existing genes are turned on and off, and several more changes whose role was unclear. "Further research will hopefully uncover exactly how these genes have adjusted their activities," said Roee Ben-Nissan, one of the researchers.
The researchers believe that the "healthy" habits of these bacteria are likely to prove particularly healthy for planet earth. For example, biotech companies that currently use cell cultures of yeast or bacteria to create industrial chemicals will be able to create these materials in cells using carbon dioxide, instead of a large quantity of corn syrup from which the cultures are currently nourished. At the same time, it is important to note that, at this stage, the bacteria are receiving their energy from formate, a non-renewable energy source.
The researchers plan to complete the evolutionary process later by "teaching" bacteria to obtain the energy they need for carbon fixation from renewable energy sources. In that scenario, the bacteria will generate renewable carbon fuel that will be carbon neutral as far as emissions into the earth's atmosphere are concerned, because their source of carbon will be the carbon dioxide in the atmosphere itself.
Published by Globes, Israel business news - en.globes.co.il - on November 28, 2019
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