HighlandReefer
Team RC
Annual Review of Marine Science
Vol. 3: 261-289 (Volume publication date January 2011)
http://www.annualreviews.org/eprint/766sw43eqBm4qqwvD6fu/full/10.1146/annurev-marine-120709-142712
The entire article is available to read.
"ABSTRACT
Organisms capable of autotrophic metabolism assimilate inorganic carbon into organic carbon. They form an integral part of ecosystems by making an otherwise unavailable form of carbon available to other organisms, a central component of the global carbon cycle. For many years, the doctrine prevailed that the Calvin-Benson-Bassham (CBB) cycle is the only biochemical autotrophic CO2 fixation pathway of significance in the ocean. However, ecological, biochemical, and genomic studies carried out over the last decade have not only elucidated new pathways but also shown that autotrophic carbon fixation via pathways other than the CBB cycle can be significant. This has ramifications for our understanding of the carbon cycle and energy flow in the ocean. Here, we review the recent discoveries in the field of autotrophic carbon fixation, including the biochemistry and evolution of the different pathways, as well as their ecological relevance in various oceanic ecosystems."
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I found this section interesting:
"Reductive Acetyl-CoA Pathway
The reductive acetyl-CoA pathway, or Wood-Ljungdahl (WL) pathway, was discovered and elucidated in acetogenic bacteria—anaerobic bacteria, which form acetate from H2 and CO2—mainly in the laboratories of Harland G. Wood and Lars G. Ljungdahl (Ljungdahl & Wood 1969, Ljungdahl 1986, Drake et al. 2008, Ljungdahl 2009). It is a relatively simple pathway in which two molecules of CO2 are combined directly in a noncyclic way to acetyl-CoA. The pathway (Figure 2c) can be divided into two branches: the methyl branch, where CO2 is consecutively reduced to a cofactor-bound methyl residue, and the carbonyl branch, where another molecule of CO2 is reduced to an enzyme-bound carbonyl residue. The key enzyme of the pathway is CO dehydrogenase/acetyl-CoA synthase, which catalyzes the reduction of CO2 to CO as well as the following step, the synthesis of acetyl-CoA from the methyl and the carbonyl residues (Pezacka & Wood 1984, Ragsdale & Wood 1985). The reduction of CO2 to the methyl group is accomplished by a series of enzymes, most of which are also unique for this pathway (Ljungdahl 1986, Ragsdale & Pierce 2008).
Most acetogens belong to the Gram-positive Clostridiales (see Drake et al. 2008 for a list of species); however, some Spirochaeta also exhibit an acetogenic lifestyle using the WL-pathway (Leadbetter et al. 1999, Pierce et al. 2008). Apart from acetogenic bacteria, which actually have a versatile metabolism and can also grow heterotrophically (Drake et al. 2008), the pathway is used in autotrophic sulfate-reducing bacteria and archaea as well as in methanogenic archaea, and potentially in planctomycetes carrying out the anaerobic oxidation of ammonium (anammox) (Jansen et al. 1984, Zeikus et al. 1985, Schauder et al. 1989, Fuchs 1994, Vorholt et al. 1995, Strous et al. 2006). Thus, the WL-pathway is so far the only carbon fixation pathway present in both bacteria and archaea, in line with the hypothesis that it is the most ancient autotrophic carbon fixation pathway (Fuchs 1989, Martin et al. 2008, Berg et al. 2010a). Yet, distinct variants of the pathway exist in the two domains. Whereas formate is a free intermediate in bacteria, formyl-methanofuran is formed in methanogenic archaea. In addition, the C1 carriers involved—tetrahydrofolate in bacteria, tetrahydropterins in archaea—are different, and thus so are the enzymes involved in the formation of the cofactor-bound methyl group. Only the key enzyme CO dehydrogenase/acetyl-CoA synthase appears to have the same origin in bacteria and archaea (Berg et al. 2010a)."
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Vol. 3: 261-289 (Volume publication date January 2011)
http://www.annualreviews.org/eprint/766sw43eqBm4qqwvD6fu/full/10.1146/annurev-marine-120709-142712
The entire article is available to read.
"ABSTRACT
Organisms capable of autotrophic metabolism assimilate inorganic carbon into organic carbon. They form an integral part of ecosystems by making an otherwise unavailable form of carbon available to other organisms, a central component of the global carbon cycle. For many years, the doctrine prevailed that the Calvin-Benson-Bassham (CBB) cycle is the only biochemical autotrophic CO2 fixation pathway of significance in the ocean. However, ecological, biochemical, and genomic studies carried out over the last decade have not only elucidated new pathways but also shown that autotrophic carbon fixation via pathways other than the CBB cycle can be significant. This has ramifications for our understanding of the carbon cycle and energy flow in the ocean. Here, we review the recent discoveries in the field of autotrophic carbon fixation, including the biochemistry and evolution of the different pathways, as well as their ecological relevance in various oceanic ecosystems."
---------------------------------------------------------------------------------
I found this section interesting:
"Reductive Acetyl-CoA Pathway
The reductive acetyl-CoA pathway, or Wood-Ljungdahl (WL) pathway, was discovered and elucidated in acetogenic bacteria—anaerobic bacteria, which form acetate from H2 and CO2—mainly in the laboratories of Harland G. Wood and Lars G. Ljungdahl (Ljungdahl & Wood 1969, Ljungdahl 1986, Drake et al. 2008, Ljungdahl 2009). It is a relatively simple pathway in which two molecules of CO2 are combined directly in a noncyclic way to acetyl-CoA. The pathway (Figure 2c) can be divided into two branches: the methyl branch, where CO2 is consecutively reduced to a cofactor-bound methyl residue, and the carbonyl branch, where another molecule of CO2 is reduced to an enzyme-bound carbonyl residue. The key enzyme of the pathway is CO dehydrogenase/acetyl-CoA synthase, which catalyzes the reduction of CO2 to CO as well as the following step, the synthesis of acetyl-CoA from the methyl and the carbonyl residues (Pezacka & Wood 1984, Ragsdale & Wood 1985). The reduction of CO2 to the methyl group is accomplished by a series of enzymes, most of which are also unique for this pathway (Ljungdahl 1986, Ragsdale & Pierce 2008).
Most acetogens belong to the Gram-positive Clostridiales (see Drake et al. 2008 for a list of species); however, some Spirochaeta also exhibit an acetogenic lifestyle using the WL-pathway (Leadbetter et al. 1999, Pierce et al. 2008). Apart from acetogenic bacteria, which actually have a versatile metabolism and can also grow heterotrophically (Drake et al. 2008), the pathway is used in autotrophic sulfate-reducing bacteria and archaea as well as in methanogenic archaea, and potentially in planctomycetes carrying out the anaerobic oxidation of ammonium (anammox) (Jansen et al. 1984, Zeikus et al. 1985, Schauder et al. 1989, Fuchs 1994, Vorholt et al. 1995, Strous et al. 2006). Thus, the WL-pathway is so far the only carbon fixation pathway present in both bacteria and archaea, in line with the hypothesis that it is the most ancient autotrophic carbon fixation pathway (Fuchs 1989, Martin et al. 2008, Berg et al. 2010a). Yet, distinct variants of the pathway exist in the two domains. Whereas formate is a free intermediate in bacteria, formyl-methanofuran is formed in methanogenic archaea. In addition, the C1 carriers involved—tetrahydrofolate in bacteria, tetrahydropterins in archaea—are different, and thus so are the enzymes involved in the formation of the cofactor-bound methyl group. Only the key enzyme CO dehydrogenase/acetyl-CoA synthase appears to have the same origin in bacteria and archaea (Berg et al. 2010a)."
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