Formate Utilization by the Crenarchaeon Desulfurococcus amylolyticus

Systems metabolic engineering of Corynebacterium glutamicum to assimilate formic acid for biomass accumulation and succinic acid production

Formate as an ideal mediator between the physicochemical and biological realms can be obtained from electrochemical reduction of CO2 and used to produce bio-chemicals. Yet, limitations arise when employing natural formate-utilizing microorganisms due to restricted product range and low biomass yield. This study presents a breakthrough: engineered Corynebacterium glutamicum strains (L2-L4) through modular engineering. L2 incorporates the formate-tetrahydrofolate cycle and reverse glycine cleavage pathway, L3 enhances NAD(P)H regeneration, and L4 reinforces metabolic flux. Metabolic modeling elucidates C1 assimilation, guiding strain optimization for co-fermentation of formate and glucose. Strain L4 achieves an OD600 of 0.5 and produces 0.6 g/L succinic acid. 13C-labeled formate confirms C1 assimilation, and further laboratory evolution yields 1.3 g/L succinic acid. This study showcases a successful model for biologically assimilating formate in C. glutamicum that could be applied in C1-based biotechnological production, ultimately forming a formate-based bioeconomy.

Cycling back to folate metabolism in cancer

Metabolic changes contribute to cancer initiation and progression through effects on cancer cells, the tumor microenvironment and whole-body metabolism. Alterations in serine metabolism and the control of one-carbon cycles have emerged as critical for the development of many tumor types. In this Review, we focus on the mitochondrial folate cycle. We discuss recent evidence that, in addition to supporting nucleotide synthesis, mitochondrial folate metabolism also contributes to metastasis through support of antioxidant defense, mitochondrial protein synthesis and the overflow of excess formate. These observations offer potential therapeutic opportunities, including the modulation of formate metabolism through dietary interventions and the use of circulating folate cycle metabolites as biomarkers for cancer detection.

Unraveling the multiplicity of geranylgeranyl reductases in Archaea: potential roles in saturation of terpenoids

The enzymology of the key steps in the archaeal phospholipid biosynthetic pathway has been elucidated in recent years. In contrast, the complete biosynthetic pathways for proposed membrane regulators consisting of polyterpenes, such as carotenoids, respiratory quinones, and polyprenols remain unknown. Notably, the multiplicity of geranylgeranyl reductases (GGRs) in archaeal genomes has been correlated with the saturation of polyterpenes. Although GGRs, which are responsible for saturation of the isoprene chains of phospholipids, have been identified and studied in detail, there is little information regarding the structure and function of the paralogs. Here, we discuss the diversity of archaeal membrane-associated polyterpenes which is correlated with the genomic loci, structural and sequence-based analyses of GGR paralogs.

Discovery and remodeling of Vibrio natriegens as a microbial platform for efficient formic acid biorefinery

Formic acid (FA) has emerged as a promising one-carbon feedstock for biorefinery. However, developing efficient microbial hosts for economically competitive FA utilization remains a grand challenge. Here, we discover that the bacterium Vibrio natriegens has exceptional FA tolerance and metabolic capacity natively. This bacterium is remodeled by rewiring the serine cycle and the TCA cycle, resulting in a non-native closed loop (S-TCA) which as a powerful metabolic sink, in combination with laboratory evolution, enables rapid emergence of synthetic strains with significantly improved FA-utilizing ability. Further introduction of a foreign indigoidine-forming pathway into the synthetic V. natriegens strain leads to the production of 29.0 g · L-1 indigoidine and consumption of 165.3 g · L-1 formate within 72 h, achieving a formate consumption rate of 2.3 g · L-1 · h-1. This work provides an important microbial chassis as well as design rules to develop industrially viable microorganisms for FA biorefinery.

Biohydrogen production beyond the Thauer limit by precision design of artificial microbial consortia

Dark fermentative biohydrogen (H₂) production could become a key technology for providing renewable energy. Until now, the H₂ yield is restricted to 4 moles of H₂ per mole of glucose, referred to as the "Thauer limit". Here we show, that precision design of artificial microbial consortia increased the H₂ yield to 5.6 mol mol^-1 glucose, 40% higher than the Thauer limit. In addition, the volumetric H₂ production rates of our defined artificial consortia are superior compared to any mono-, co- or multi-culture system reported to date. We hope this study to be a major leap forward in the engineering of artificial microbial consortia through precision design and provide a breakthrough in energy science, biotechnology and ecology. Constructing artificial consortia with this drawing-board approach could in future increase volumetric production rates and yields of other bioprocesses. Our artificial consortia engineering blueprint might pave the way for the development of a H₂ production bioindustry.