A 3-Hydroxypropionate/4-Hydroxybutyrate Autotrophic Carbon Dioxide Assimilation Pathway in Archaea

Mikrobiologie, Fakultät Biologie, Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany.
Science (Impact Factor: 33.61). 07/2008; 318(5857):1782-6. DOI: 10.1126/science.1149976
Source: PubMed


The assimilation of carbon dioxide (CO2) into organic material is quantitatively the most important biosynthetic process. We discovered that an autotrophic member
of the archaeal order Sulfolobales, Metallosphaera sedula, fixed CO2 with acetyl–coenzyme A (acetyl-CoA)/propionyl-CoA carboxylase as the key carboxylating enzyme. In this system, one acetyl-CoA
and two bicarbonate molecules were reductively converted via 3-hydroxypropionate to succinyl-CoA. This intermediate was reduced
to 4-hydroxybutyrate and converted into two acetyl-CoA molecules via 4-hydroxybutyryl-CoA dehydratase. The key genes of this
pathway were found not only in Metallosphaera but also in Sulfolobus, Archaeoglobus, and Cenarchaeum species. Moreover, the Global Ocean Sampling database contains half as many 4-hydroxybutyryl-CoA dehydratase sequences as
compared with those found for another key photosynthetic CO2-fixing enzyme, ribulose-1,5-bisphosphate carboxylase-oxygenase. This indicates the importance of this enzyme in global carbon

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    • "Recently discovered in the domain Archaea are the 3-hydroxypropio- nate / 4-hydroxybutyrate cycle (Berg et al., 2007) and the dicarboxylate / 4-hydroxybutyrate cycle (Huber et al., 2008), which are formed, as suggested (Marakushev and Belonogova, 2011) in the later divergent evolution of the original CAF bicycle. Logically, it becomes reasonable to assume that the reduced, non-closed reductive citrate pathway described in heliobacteria (Pickett et al., 1994; Sattley et al., 2008), as well as the reductive acetyl-CoA pathway in methanogenic archaea and acetate-producing clostridia (Ljungdahl and Wood, 1965; Wood, 1991; Ljungdahl, 2009) are also the result of the development of the CAF bicycle. "
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    ABSTRACT: We dedicated our review to the memory of the legendary co-discoverer of the photosynthetic reductive pentose phosphate cycle, Professor Emeritus Andrew Alm Benson, on the occasion of his death at the age of 97, on January 16, 2015. Th is review examines the complexity and diversity of photoreductive carbon metabolism pathways in prokaryotic and eukaryotic phototrophs from the point of view of evolutionary adaptation. In response to global environmental change, the functional signifi cance of adaptive rearrangements in the biochemistry and structure of the photosynthetic apparatus is evaluated. We discuss the possibility of a functional interrelationship between phototrophic and heterotrophic tissues / cells in order to optimize the anabolism in symbiotic organisms, macrophyte algae, and photosynthesizing organs of aquatic and terrestrial higher plants. We also discuss the protective strategy of photosynthetic machinery from the negative infl uence of solar radiation, the positive role of some metal ions in this protective process, and the concept of photohalosynthesis.
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    • "M. sedula and the Sulfolobus species grow well at low pH, a significant advantage for production of acidic products such as lactic and 3-hydroxypropionic acids, which are easier to purify in their protonated forms (Maris et al., 2004). M. sedula's ability to solubilize metals by oxidizing them has applications in bioleaching, while its novel carbon-fixation pathway (Berg et al., 2007) offers a potential alternative to the RuBisCo-dependent Calvin Cycle for carbon-capture applications. Fuels are typically highly reduced organic molecules, so various efforts to maximize biofuel titers have focused on tuning the redox pathways within mesophilic hosts to favor the production of reduced end products (Liu et al., 2015). "
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    ABSTRACT: Enzymes from extremely thermophilic microorganisms have been of technological interest for some time because of their ability to catalyze reactions of industrial significance at elevated temperatures. Thermophilic enzymes are now routinely produced in recombinant mesophilic hosts for use as discrete biocatalysts. Genome and metagenome sequence data for extreme thermophiles provide useful information for putative biocatalysts for a wide range of biotransformations, albeit involving at most a few enzymatic steps. However, in the past several years, unprecedented progress has been made in establishing molecular genetics tools for extreme thermophiles to the point that the use of these microorganisms as metabolic engineering platforms has become possible. While in its early days, complex metabolic pathways have been altered or engineered into recombinant extreme thermophiles, such that the production of fuels and chemicals at elevated temperatures has become possible. Not only does this expand the thermal range for industrial biotechnology, it also potentially provides biodiverse options for specific biotransformations unique to these microorganisms. The list of extreme thermophiles growing optimally between 70 and 100°C with genetic toolkits currently available includes archaea and bacteria, aerobes and anaerobes, coming from genera such as Caldicellulosiruptor, Sulfolobus, Thermotoga, Thermococcus, and Pyrococcus. These organisms exhibit unusual and potentially useful native metabolic capabilities, including cellulose degradation, metal solubilization, and RuBisCO-free carbon fixation. Those looking to design a thermal bioprocess now have a host of potential candidates to choose from, each with its own advantages and challenges that will influence its appropriateness for specific applications. Here, the issues and opportunities for extremely thermophilic metabolic engineering platforms are considered with an eye toward potential technological advantages for high temperature industrial biotechnology.
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    • "A novel pathway of CO 2 fixation found by Berg et al. (2007) in Archaea. Four other pathways are known by which autotrophic representatives of bacteria, archaea, and eukarya fix carbon "

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