Energy Conservation in the Acetogenic Bacterium Clostridium aceticum.

Anja Wiechmann,Volker Müller

doi:10.3390/microorganisms9020258

Anja Wiechmann, Volker Müller

Open Access

https://doi.org/10.3390/microorganisms9020258

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Journal: Microorganisms	Publication Date: Jan 27, 2021
Citations: 7	License type: CC BY 4.0

Affiliation: Goethe University Frankfurt

Abstract

In times of global warming caused by the extensive use of fossil fuels, the need to capture gaseous carbon compounds is growing bigger. Several groups of microorganisms can fix the greenhouse gas CO2. Out of these, acetogenic bacteria are role models in their ability to reduce CO2 with hydrogen to acetate, which makes acetogens prime candidates for genetic modification towards biotechnological production of value-added compounds from CO2, such as biofuels. However, growth of acetogens on gaseous substrates is strongly energy-limited, and successful metabolic engineering requires a detailed knowledge of the bioenergetics. In 1939, Clostridium aceticum was the first acetogen to be described. A recent genomic study revealed that this organism contains cytochromes and therefore may use a proton gradient in its respiratory chain. We have followed up these studies and will present data that C. aceticum does not use a H+ but a Na+ gradient for ATP synthesis, established by a Na+-Rnf. Experimental data and in silico analyses enabled us to propose the biochemistry and bioenergetics of acetogenesis from H2 + CO2 in C. aceticum.

Highlights

University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt am Main, Germany; Abstract: In times of global warming caused by the extensive use of fossil fuels, the need to capture gaseous carbon compounds is growing bigger
The methyl group is transferred by a methyltransferase to the CODH/ACS, where it condenses with enzyme-bound CO and CoA to acetyl-CoA which is further converted via acetyl-phosphate to acetate [8]
Since the bacteria grow on H2 + CO2 while producing acetate, the entire lithotrophic metabolism must be coupled to additional ATP synthesis [6]

Summary

Introduction

University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt am Main, Germany; Abstract: In times of global warming caused by the extensive use of fossil fuels, the need to capture gaseous carbon compounds is growing bigger. Growth of acetogens on gaseous substrates is strongly energy-limited, and successful metabolic engineering requires a detailed knowledge of the bioenergetics. One CO2 is reduced to enzyme-bound carbon monoxide by CO dehydrogenase/acetyl-CoA synthase (CODH/ACS) [3,7]. The methyl group is transferred by a methyltransferase to the CODH/ACS, where it condenses with enzyme-bound CO and CoA to acetyl-CoA which is further converted via acetyl-phosphate to acetate [8]. Since the bacteria grow on H2 + CO2 while producing acetate, the entire lithotrophic metabolism must be coupled to additional ATP synthesis [6]. In recent years it has been shown that acetogens use the electron transfer pathway to the WLP as the site of energy conservation by a chemiosmotic mechanism [6,9].

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