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… scientists engineer bacteria to create sugar from the greenhouse gas carbon dioxide
http://wis-wander.weizmann.ac.il/chemistry/eating-air-making-fuel[font face=Serif][font size=5]Eating Air, Making Fuel[/font]
[font size=4]Weizmann Institute scientists engineer bacteria to create sugar from the greenhouse gas carbon dioxide[/font]
Embargoed until June 23, 2016, 12:00 pm EST, 19:00 Jerusalem time
[font size=3]All life on the planet relies, in one way or another, on a process called carbon fixation: the ability of plants, algae and certain bacteria to “pump” carbon dioxide (CO₂ ) from the environment, add solar or other energy and turn it into the sugars that are the required starting point needed for life processes. At the top of the food chain are different organisms (some of which think, mistakenly, that they are “more advanced”) that use the opposite means of survival: they eat sugars (made by photosynthetic plants and microorganisms) and then release carbon dioxide into the atmosphere. This means of growth is called “heterotrophism.” Humans are, of course, heterotrophs in the biological sense because the food they consume originates from the carbon fixation processes of nonhuman producers.
…
The metabolic pathway for carbon fixation is well known, and Milo and his group reckoned that, with proper planning, they would be able to attach the genes containing the information for building it into the bacterium’s genome. Yet the main enzyme used in plants to fix carbon, RuBisCO, utilizes as a substrate for the CO₂ fixation reaction a metabolite which is toxic for the bacterial cells. Thus the design had to include precisely regulating the expression levels of the various genes across this multistep pathway.
In one way the team’s well-thought-out plan was a resounding success: The bacteria did indeed produce the carbon fixation enzymes, and these were functional. But the machinery, as a whole, did not “deliver the goods.” Even though the carbon fixation machinery was expressed, the bacteria failed to use CO₂ for sugar synthesis, relying instead on an external supply of sugar. “Of course, we were dealing with an organism that has evolved over millions of years to eat sugar, not CO₂,” says Antonovsky. “So we turned to evolution to help us create the system we intended.”
Antonovsky, Milo and the team, including Shmuel Gleizer, Arren Bar-Even, Yehudit Zohar, Elad Herz and others, next designed tanks called “chemostats,” in which they grew the bacteria, gradually nudging them into developing an appetite for CO₂. Initially, along with ample bubbles of CO₂, the bacteria in the tanks were offered a large amount of pyruvate, which is an energy source, as well as barely enough sugar to survive. Thus, by changing the conditions of their environment and stressing them, the scientists forced the bacteria to learn, by adaptation and development, to use the more abundant material in their environment. A month went by, and things remained fairly static. The bacteria seemed to not “get the hint.” But at around a month and a half, some bacteria showed signs of doing more than “just surviving.” By the third month the scientists were able to wean the evolved bacteria from the sugar and raise them on CO₂ and pyruvate alone. Isotope labeling of the carbon dioxide molecules revealed that the bacteria were indeed using CO₂ to create a significant portion of their body mass, including all the sugars needed to make the cell.
…[/font][/font]
[font size=4]Weizmann Institute scientists engineer bacteria to create sugar from the greenhouse gas carbon dioxide[/font]
Embargoed until June 23, 2016, 12:00 pm EST, 19:00 Jerusalem time
[font size=3]All life on the planet relies, in one way or another, on a process called carbon fixation: the ability of plants, algae and certain bacteria to “pump” carbon dioxide (CO₂ ) from the environment, add solar or other energy and turn it into the sugars that are the required starting point needed for life processes. At the top of the food chain are different organisms (some of which think, mistakenly, that they are “more advanced”) that use the opposite means of survival: they eat sugars (made by photosynthetic plants and microorganisms) and then release carbon dioxide into the atmosphere. This means of growth is called “heterotrophism.” Humans are, of course, heterotrophs in the biological sense because the food they consume originates from the carbon fixation processes of nonhuman producers.
…
The metabolic pathway for carbon fixation is well known, and Milo and his group reckoned that, with proper planning, they would be able to attach the genes containing the information for building it into the bacterium’s genome. Yet the main enzyme used in plants to fix carbon, RuBisCO, utilizes as a substrate for the CO₂ fixation reaction a metabolite which is toxic for the bacterial cells. Thus the design had to include precisely regulating the expression levels of the various genes across this multistep pathway.
In one way the team’s well-thought-out plan was a resounding success: The bacteria did indeed produce the carbon fixation enzymes, and these were functional. But the machinery, as a whole, did not “deliver the goods.” Even though the carbon fixation machinery was expressed, the bacteria failed to use CO₂ for sugar synthesis, relying instead on an external supply of sugar. “Of course, we were dealing with an organism that has evolved over millions of years to eat sugar, not CO₂,” says Antonovsky. “So we turned to evolution to help us create the system we intended.”
Antonovsky, Milo and the team, including Shmuel Gleizer, Arren Bar-Even, Yehudit Zohar, Elad Herz and others, next designed tanks called “chemostats,” in which they grew the bacteria, gradually nudging them into developing an appetite for CO₂. Initially, along with ample bubbles of CO₂, the bacteria in the tanks were offered a large amount of pyruvate, which is an energy source, as well as barely enough sugar to survive. Thus, by changing the conditions of their environment and stressing them, the scientists forced the bacteria to learn, by adaptation and development, to use the more abundant material in their environment. A month went by, and things remained fairly static. The bacteria seemed to not “get the hint.” But at around a month and a half, some bacteria showed signs of doing more than “just surviving.” By the third month the scientists were able to wean the evolved bacteria from the sugar and raise them on CO₂ and pyruvate alone. Isotope labeling of the carbon dioxide molecules revealed that the bacteria were indeed using CO₂ to create a significant portion of their body mass, including all the sugars needed to make the cell.
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