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    Home > Medical News > Medical World News > Cell: let bacteria become autotrophs! Grow by consuming carbon dioxide

    Cell: let bacteria become autotrophs! Grow by consuming carbon dioxide

    • Last Update: 2019-12-03
    • Source: Internet
    • Author: User
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    Recently, according to a study in the journal Cell, researchers in Israel have created a new strain of E.coli that uses carbon dioxide as energy rather than organic compounds This achievement highlights the amazing plasticity of bacterial metabolism and provides a framework for future carbon and biological production https://doi.org/10.1016/j.cell.2019.11.009 Organisms are divided into autotrophs (converting organic carbon into biomass) and heterotrophies (consuming organic compounds) Autotrophs control the biomass of the earth, provide food and fuel, and better understand the principle of autotrophic growth and promote the method of autotrophic growth is very important to achieve sustainable development One of the great challenges of synthetic biology is to turn heterotrophic model organisms into synthetic autotrophs Although people have extensive interest in renewable energy storage and more sustainable food production, the past efforts to design industry-related heterotrophic model organisms to use carbon dioxide as the sole carbon source have failed Previous attempts to establish autocatalytic carbon dioxide fixed cycle in heterotrophic model organisms always require the addition of multi carbon organic compounds to achieve stable growth In this study, the main goal of the researchers is to establish a convenient scientific platform to enhance the fixation of carbon dioxide, which can help solve problems related to sustainable production of food and fuel and global warming caused by carbon dioxide emissions As the main force of biotechnology, the transformation of E coli from organic carbon to carbon dioxide is an important step towards the establishment of such a platform As a result, researchers used metabolic rewiring and laboratory evolution to turn E coli into autotrophs The engineering strain collects energy from the formate produced by the electrochemical production of renewable resources, because formate is an organic carbon compound and cannot be used as the carbon source of E.coli, so it does not support heterotrophic pathway The strain has also been engineered to produce unnatural enzymes for carbon fixation and reduction, as well as for energy collection from formic acid However, these changes alone are not enough to support autotrophy, because the metabolism of E coli adapts to heterotrophic growth In order to overcome this problem, the researchers use adaptive laboratory evolution as a metabolic optimization tool By inactivating the central enzyme involved in heterotrophic growth, the bacteria can grow more dependent on autotrophic pathway In addition, a limited amount of xylose (the source of organic carbon) is used to culture cells in a chemical thermostat containing a large amount of formate and 10% carbon dioxide to inhibit heterotrophic pathway Xylose, initially supplied for about 300 days, is enough to support cell proliferation to initiate evolution Schematic diagram of chemical autotrophic Escherichia coli In this environment, autotrophs have great selective advantages over heterotrophic organisms that rely on xylose as the carbon source of growth They use carbon dioxide as the only carbon source to produce biomass The researchers use isotope markers to confirm that the isolated bacteria are truly autotrophic bacteria 13C isotope labeling experiments show that all biomass components are produced by carbon dioxide as the only carbon source In order for the general approach to laboratory evolution to succeed, researchers must combine the required changes in cell behavior with adaptive advantages By sequencing the genomes and plasmids of the evolved autotrophic cells, we found that only 11 mutations were obtained in the evolutionary process: one is the gene that affects the enzyme encoding the carbon fixation cycle; the second is the mutation found in the gene that was usually observed in the previous adaptive laboratory evolution experiment, which shows that they are not necessarily specific to the autotrophic pathway The third is the mutation of unknown gene This study is the first to describe the successful transformation of bacterial growth patterns, allowing intestinal bacteria to survive in a plant like manner Surprisingly, the number of genetic changes needed to make this transformation is relatively small The main limitation of the study is that the consumption of formate by bacteria is more than that by carbon fixation, the authors said In addition, more research is needed before discussing the scalability of industrial methods In the future work, researchers will focus on providing energy through renewable power to solve the problem of carbon dioxide emission, determine whether the surrounding atmospheric conditions can support autotrophy, and try to reduce the mutation most related to autotrophic growth This feat opens up a new prospect for the use of engineered bacteria to transform products we see as waste into fuels, food or other compounds It can also serve as a platform to better understand and improve the molecular machinery that is the basis of human food production, thereby helping to increase agricultural production.
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