Abstract
BackgroundAcetogenic bacteria constitute promising biocatalysts for the conversion of CO2/H2 or synthesis gas (H2/CO/CO2) into biofuels and value-added biochemicals. These microorganisms are naturally capable of autotrophic growth via unique acetogenesis metabolism. Despite their biosynthetic potential for commercial applications, a systemic understanding of the transcriptional and translational regulation of the acetogenesis metabolism remains unclear.ResultsBy integrating genome-scale transcriptomic and translatomic data, we explored the regulatory logic of the acetogenesis to convert CO2 into biomass and metabolites in Eubacterium limosum. The results indicate that majority of genes associated with autotrophic growth including the Wood-Ljungdahl pathway, the reduction of electron carriers, the energy conservation system, and gluconeogenesis were transcriptionally upregulated. The translation efficiency of genes in cellular respiration and electron bifurcation was also highly enhanced. In contrast, the transcriptionally abundant genes involved in the carbonyl branch of the Wood-Ljungdahl pathway, as well as the ion-translocating complex and ATP synthase complex in the energy conservation system, showed decreased translation efficiency. The translation efficiencies of genes were regulated by 5′UTR secondary structure under the autotrophic growth condition.ConclusionsThe results illustrated that the acetogenic bacteria reallocate protein synthesis, focusing more on the translation of genes for the generation of reduced electron carriers via electron bifurcation, rather than on those for carbon metabolism under autotrophic growth.
Highlights
Acetogenic bacteria constitute promising biocatalysts for the conversion of CO2/H2 or synthesis gas (H2/carbon monoxide (CO)/CO2) into biofuels and value-added biochemicals
Acetogenic bacteria are naturally capable of metabolizing industrial waste gas, such as carbon monoxide (CO) and carbon dioxide (CO2), which are known as components of syngas, for autotrophic growth to form biomass and to produce various metabolites, mainly acetyl-CoA, via the Wood-Ljungdahl pathway (WLP) [1, 2]
Determination of differential gene expression levels using RNA sequencing (RNA-Seq) The autotrophic condition triggers the expression of a wide array of genes related to acetogenesis at the levels of transcription and translation, which are subject to extensive regulation to ensure cell survival under autotrophy
Summary
Acetogenic bacteria constitute promising biocatalysts for the conversion of CO2/H2 or synthesis gas (H2/CO/CO2) into biofuels and value-added biochemicals. The electron-bifurcating hydrogenase in acetogenic bacteria oxidizes molecular hydrogen and catalyzes the exergonic reduction of NAD, which drives the endergonic reduction of Fd [12] This reduced form of Fd is used as an electron donor for an FDH and an ion-translocating membrane protein complex in all acetogenic bacteria. This understanding of the molecular details associated with acetogenesis provides the basis for engineering acetogenic bacteria to expand their capability to produce value-added biofuels and biochemicals
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