this week, synthetic biologists from Israel made a big deal: they published a paper in Cell, announcing that they had successfully transformed E. coli into autotrophs-that is, they no longer need to ingest sugars. Instead, they fix carbon dioxide as their only carbon source, making their own organic molecules like plants do.

this thing sounds very powerful, but it is actually quite powerful, but the transformation process is not easy, and it can only be realized under the special conditions of the laboratory. I read the research papers and felt that scientists were really trying very hard to force these experimental organisms to change their metabolic pathways, and the bacteria really refused to do so.

in order to transform Escherichia coli into autotrophs, we must first choose a source of energy for them and transfer to them the genes needed to fix carbon dioxide and obtain energy. Instead of letting the bacteria use light energy (photosynthesis seems too complex), the researchers chose a chemical energy pathway for them to get energy from the chemical reaction that turns formic acid into carbon dioxide, and then use this energy to fix carbon dioxide.

(a diagram showing that the process of fixing carbon dioxide on the right uses energy from the chemical reaction on the left)

however, it is not enough to cram the metabolic enzyme gene into the bacteria. After the key gene editing work has been done, the metabolism of these bacteria has not been completely changed. As a result, the researchers used the power of evolution. They continuously cultured the bacteria in an environment with little sugar and high carbon dioxide content, hoping that the bacteria could accumulate mutations "suitable for eating carbon dioxide" in this environment. Finally, after more than 200 days, Escherichia coli, which can rely entirely on carbon dioxide as its carbon source, was born.

but even if autotrophic Escherichia coli is born in this way, they can only use carbon dioxide for a living in a laboratory environment with a concentration of up to 10% carbon dioxide, and if they are put in a normal atmospheric environment, they still need to eat sugar to survive. So far, this is only a preliminary result (but it's really amazing).

researchers hope that such E. coli will make better use of carbon dioxide in the future and eventually become a low-carbon version of the "biological factory" to produce all kinds of useful substances for human beings. However, it is still a long way from this goal.

as for why not directly use plants or cyanobacteria that are autotrophs, the reason given by the researchers is that these organisms are far less convenient for gene editing than E. coli, although they are good at fixing carbon dioxide, but can not meet the needs of human beings to produce a variety of chemicals.

generally speaking, Escherichia coli is probably easier to bully (

Source: https://www.cell.com/cell/fulltext/S0092-8674(19)31230-9

https://www.nature.com/articles/d41586-019-03679-x

an irrelevant complaint: today, I suddenly feel that when you can't find a picture of E. coli, you can probably shoot some rice strips p-p (

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