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Pink-pigmented facultative methylotrophs have long been studied for their ability to grow on reduced single-carbon (C 1 ) compounds. The C 1 groups that support methylotrophic growth may come from a variety of sources. Here, we describe a group of Methylobacterium strains that can engage in methoxydotrophy: they can metabolize the methoxy groups from several aromatic compounds that are commonly the product of lignin depolymerization. Furthermore, these organisms can utilize the full aromatic ring as a growth substrate, a phenotype that has rarely been described in Methylobacterium . We demonstrated growth on p -hydroxybenzoate, protocatechuate, vanillate, and ferulate in laboratory culture conditions. We also used comparative genomics to explore the evolutionary history of this trait, finding that the capacity for aromatic catabolism is likely ancestral to two clades of Methylobacterium , but has also been acquired horizontally by closely related organisms. In addition, we surveyed the published metagenome data to find that the most abundant group of aromatic-degrading Methylobacterium in the environment is likely the group related to Methylobacterium nodulans , and they are especially common in soil and root environments. The demethoxylation of lignin-derived aromatic monomers in aerobic environments releases formaldehyde, a metabolite that is a potent cellular toxin but that is also a growth substrate for methylotrophs. We found that, whereas some known lignin-degrading organisms excrete formaldehyde as a byproduct during growth on vanillate, Methylobacterium do not. This observation is especially relevant to our understanding of the ecology and the bioengineering of lignin degradation.
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This content will become publicly available on September 3, 2026
Aromatic acid metabolism in Methylobacterium extorquens reveals interplay between methylotrophic and heterotrophic pathways
ABSTRACT Efforts toward microbial conversion of lignin to value-added products face many challenges because lignin’s methoxylated aromatic monomers release toxic C1byproducts such as formaldehyde. The ability to grow on methoxylated aromatic acids (e.g., vanillic acid) has been identified in certain clades of methylotrophs, bacteria characterized by their unique ability to tolerate and metabolize high concentrations of formaldehyde. Here, we use a phyllosphere methylotroph isolate,Methylobacterium extorquensSLI 505, as a model to identify the fate of formaldehyde during methylotrophic growth on vanillic acid.M. extorquensSLI 505 displays concentration-dependent growth phenotypes on vanillic acid without concomitant formaldehyde accumulation. We conclude thatM. extorquensSLI 505 overcomes metabolic bottlenecks from simultaneous assimilation of multicarbon and C1intermediates by allocating formaldehyde toward dissimilation and assimilating the ring carbons of vanillic acid heterotrophically. We correlate this strategy with maximization of bioenergetic yields and demonstrate that formaldehyde dissimilation for energy generation rather than formaldehyde detoxification is advantageous for growth on aromatic acids.M. extorquensSLI 505 also exhibits catabolite repression during growth on methanol and low concentrations of vanillic acid, but no diauxic patterns during growth on methanol and high concentrations of vanillic acid. Results from this study outline metabolic strategies employed byM. extorquensSLI 505 for growth on a complex single substrate that generates both C1and multicarbon intermediates and emphasizes the robustness ofM. extorquensfor biotechnological applications for lignin valorization.IMPORTANCELignin, one of the most abundant and renewable carbon sources on Earth, is a promising alternative to non-renewable fossil fuels used to produce petrochemicals. Degradation of lignin releases toxic C1byproducts such as formaldehyde, and thus most microorganisms are not suitable for biorefining lignin. By contrast,Methylobacterium extorquensSLI 505 is capable of growth on high concentrations of aromatic acids without concomitant formaldehyde accumulation. In addition, we show that the growth ofM. extorquensSLI 505 on aromatic acids is coupled to the production of the bioplastic, polyhydroxybutyrate. Aromatic acids serve as a model by which to understand howM. extorquensSLI 505 balances methylotrophic and heterotrophic pathways during growth to provide strategies for growth optimization when using complex substrates in both ecological and industrial fermentation applications.
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- Award ID(s):
- 2127732
- PAR ID:
- 10639116
- Editor(s):
- Bose, Arpita
- Publisher / Repository:
- American Society for Microbiology
- Date Published:
- Journal Name:
- Applied and Environmental Microbiology
- ISSN:
- 0099-2240
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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