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Regulatory mechanisms for aromatic carbon metabolism in Comamonas testosteroni

ABSTRACT: Widely reported discrepancies between metabolic flux and transcripts or enzyme levels in bacterial metabolism imply complex regulation mechanisms need to be considered, especially in new bacterial platforms for bioremediation and bioproduction. Comamonas testosteroni strains, which metabolize various natural and xenobiotic aromatic compounds, represent such platforms whose metabolic regulations are still unknown. Here, we identify analogous multi-level regulation mechanisms in the metabolism of two lignin-related (4-hydroxybenzoate and vanillate) and one plastic-related (terephthalate) aromatic compounds in C. testosteroni KF-1, a wastewater isolate. Transcription-level regulation controlled initial catabolism and cleavage of the compounds, but subsequent carbon fluxes in central carbon metabolism are governed by metabolite-level thermodynamic regulation. Quantitative 13C-fingerprinting of tricarboxylic acid cycle and cataplerotic reactions elucidate key carbon routing that is not evident from enzyme abundance changes. Therefore, as-needed transcriptional activation of aromatic catabolism is coupled with metabolic fine-tuning of central metabolism, thus delineating pathway candidates for different metabolic manipulations.

INSTRUMENT(S): Liquid Chromatography MS - negative - reverse phase

SUBMITTER: Rebecca Wilkes

PROVIDER: MTBLS3947 | MetaboLights | 2022-11-21

REPOSITORIES: MetaboLights

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Project description:Millard2016 - E. coli central carbon and energy metabolism This model is described in the article: Metabolic regulation is sufficient for global and robust coordination of glucose uptake, catabolism, energy production and growth in Escherichia coli Pierre Millard , Kieran Smallbone, Pedro Mendes PLoS ONE Abstract: The metabolism of microorganisms is regulated through two main mechanisms: changes of enzyme capacities as a consequence of gene expression modulation (“hierarchical control”) and changes of enzyme activities through metabolite-enzyme interactions. An increasing body of evidence indicates that hierarchical control is insufficient to explain metabolic behaviors, but the system-wide impact of metabolic regulation remains largely uncharacterized. To clarify its role, we developed and validated a detailed kinetic model of Escherichia coli central metabolism that links growth to environment. Metabolic control analyses confirm that the control is widely distributed across the network and highlight strong interconnections between all the pathways. Exploration of the model solution space reveals that several robust properties emerge from metabolic regulation, from the molecular level (e.g. homeostasis of total metabolite pool) to the overall cellular physiology (e.g. coordination of carbon uptake, catabolism, energy and redox production, and growth), while allowing a large degree of flexibility at most individual metabolic steps. These properties have important physiological implications for E. coli and significantly expand the self-regulating capacities of its metabolism. This model is hosted on BioModels Database and identified by: MODEL1505110000. To cite BioModels Database, please use: BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information.

Project description:Lignin is an abundant aromatic polymer formed in plants by coupling reactions of p-coumaryl, coniferyl, and sinapyl alcohols. Pseudomonas putida KT2440 (P. putida KT2440), a robust soil bacterium, naturally catabolizes many aromatic compounds derived from lignin as carbon and energy sources and has been extensively engineered to valorize guaiacyl (G) and p-hydroxyphenyl (H) lignin-derived aromatic species to valuable chemicals. However, only a few studies report the capacity of Pseudomonads to grow on syringyl (S) lignin-derived compounds. In this work, we demonstrate that P. putida KT2440 catabolizes syringate in the presence of an auxiliary energy source. Overexpression of vanAB, encoding a native Rieske non-heme iron monooxygenase, enabled catabolism of syringate and syringaldehyde without an additional carbon and energy source. In vitro biochemical characterization of VanAB confirmed that this enzyme O-demethylates syringate to 3-O-methylgallate and, subsequently, 3-O-methylgallate to gallate, albeit 4- and 55-fold less efficiently than vanillate, respectively. Transcriptomics and proteomics experiments demonstrate that the galADBC transcripts and enzymes required for gallate catabolism are induced when vanAB is overexpressed during cultivation in syringate. Further, we show that that the endogenous protocatechuate-3,4-dioxygenase PcaHG ring-opens gallate to produce 2-pyrone-4,6-dicarboxylic acid (PDC), a promising bio-based chemical. Constitutive overexpression of vanAB and pcaHG along with galA deletion enabled PDC production from SA at a 70% (mol/mol) yield. Furthermore, leveraging the LigAB dioxygenase from Sphingobium sp. SYK-6 and VanAB O-demethylase from Pseudomonas sp. HR199 enabled simultaneous conversion of monomers with S-, G-, and H-type functionality to PDC at 82% (mol/mol) yield. Overall, this study elucidates a native pathway for catabolism of syringyl lignin-derived compounds in P. putida KT2440 and demonstrates the potential of this robust host for biological funneling of substrates derived from all three canonical monolignols.

			Action	DRS
	MTBLS3947	Other
	FILES	Other
	a_MTBLS3947_LC-MS_negative_reverse-phase_metabolite_profiling.txt	Txt
	files-all.json	Other
	i_Investigation.txt	Txt

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Regulatory mechanisms for aromatic carbon metabolism in Comamonas testosteroni

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