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The only known source of vitamin B 12 (adenosylcobalamin) is from bacteria and archaea. Here, using genetic and metabolic engineering, we generate an Escherichia coli strain that produces vitamin B 12 via an engineered de novo aerobic biosynthetic pathway. In vitro and/or in vivo analysis of genes involved in adenosylcobinamide phosphate biosynthesis from Rhodobacter capsulatus suggest that the biosynthetic steps from co(II)byrinic acid a,c-diamide to adocobalamin are the same in both the aerobic and anaerobic pathways. Finally, we increase the vitamin B 12 yield of a recombinant E. coli strain by more than ∼250-fold to 307.00 µg g −1 DCW via metabolic engineering and optimization of fermentation conditions. Beyond our demonstration of E. coli as a microbial biosynthetic platform for vitamin B 12 production, our study offers an encouraging example of how the several dozen proteins of a complex biosynthetic pathway can be transferred between organisms to facilitate industrial production. Vitamin B 12 is an essential nutrient with limited natural sources. Here the authors transfer 28 pathway synthesis genes from several bacteria including R. capsulatus to E. coli and, using metabolic engineering and optimised fermentation conditions, achieve high yields.

Vitamin B12, also known as the anti-pernicious anemia factor, is an essential micronutrient totally dependent on dietary sources that is commonly integrated with food supplements. Four vitamin B12 forms—cyanocobalamin, hydroxocobalamin, 5′-deoxyadenosylcobalamin, and methylcobalamin—are currently used for supplementation and, here, we provide an overview of their biochemical role, bioavailability, and efficacy in different dosage forms. Since the effective quantity of vitamin B12 depends on the stability of the different forms, we further provide a review of their main reactivity and stability under exposure to various environmental factors (e.g., temperature, pH, light) and the presence of some typical interacting compounds (oxidants, reductants, and other water-soluble vitamins). Further, we explore how the manufacturing process and storage affect B12 stability in foods, food supplements, and medicines and provide a summary of the data published to date on the content-related quality of vitamin B12 products on the market. We also provide an overview of the approaches toward their stabilization, including minimization of the destabilizing factors, addition of proper stabilizers, or application of some (innovative) technological processes that could be implemented and contribute to the production of high-quality vitamin B12 products.

The vitamin B 12 family of cofactors known as cobamides are essential for a variety of microbial metabolisms. We used comparative genomics of 11,000 bacterial species to analyze the extent and distribution of cobamide production and use across bacteria. We find that 86% of bacteria in this data set have at least one of 15 cobamide-dependent enzyme families, but only 37% are predicted to synthesize cobamides de novo. The distribution of cobamide biosynthesis and use vary at the phylum level. While 57% of Actinobacteria are predicted to biosynthesize cobamides, only 0.6% of Bacteroidetes have the complete pathway, yet 96% of species in this phylum have cobamide-dependent enzymes. The form of cobamide produced by the bacteria could be predicted for 58% of cobamide-producing species, based on the presence of signature lower ligand biosynthesis and attachment genes. Our predictions also revealed that 17% of bacteria have partial biosynthetic pathways, yet have the potential to salvage cobamide precursors. Bacteria with a partial cobamide biosynthesis pathway include those in a newly defined, experimentally verified category of bacteria lacking the first step in the biosynthesis pathway. These predictions highlight the importance of cobamide and cobamide precursor salvaging as examples of nutritional dependencies in bacteria.

Endogenous remyelination of the CNS can be robust and restore function, yet in multiple sclerosis it becomes less complete with time. Promoting remyelination is a major therapeutic goal, both to restore function and to protect axons from degeneration. Remyelination is thought to depend on oligodendrocyte progenitor cells, giving rise to nascent remyelinating oligodendrocytes. Surviving, mature oligodendrocytes are largely regarded as being uninvolved. We have examined this question using two large animal models. In the first model, there is extensive demyelination and remyelination of the CNS, yet oligodendrocytes survive, and in recovered animals there is a mix of remyelinated axons interspersed between mature, thick myelin sheaths. Using 2D and 3D light and electron microscopy, we show that many oligodendrocytes are connected to mature and remyelinated myelin sheaths, which we conclude are cells that have reextended processes to contact demyelinated axons while maintaining mature myelin internodes. In the second model in vitamin B12-deficient nonhuman primates, we demonstrate that surviving mature oligodendrocytes extend processes and ensheath demyelinated axons. These data indicate that mature oligodendrocytes can participate in remyelination.

Vitamin B12 is a widely used compound in the feed and food, healthcare and medical industries that can only be produced by fermentation because of the complexity of its chemical synthesis. For this reason, finding better producer strains and optimizing their bioprocesses have been the main focus of industrial producers over the last few decades. In this review, we initially provide a historical overview of vitamin B12 research and the main biosynthetic characteristics of the two microorganism families typically used for its industrial production: several strains of Propionibacterium freudenreichii and strains related to Pseudomonas denitrificans. Later, a complete summary of the current state of vitamin B12 industrial production as well as the main advances and challenges for improving it is detailed, with a special focus on bioprocess optimization, which aims not only to increase production but also sustainability. In addition, a comprehensive list of the most important and relevant patents for the present industrial strains is provided. Finally, the potential applications of vitamin B12 in different markets are discussed.

Anaemia and iron deficiency are frequent in patients scheduled for cardiac surgery. This study assessed whether immediate preoperative treatment could result in reduced perioperative red blood cell (RBC) transfusions and improved outcome. In this single-centre, randomised, double-blind, parallel-group controlled study, patients undergoing elective cardiac surgery with anaemia (n=253; haemoglobin concentration (Hb) <120 g/L in women and Hb <130 g/L in men) or isolated iron deficiency (n=252; ferritin <100 mcg/L, no anaemia) were enrolled. Participants were randomly assigned (1:1) with the use of a computer-generated range minimisation (allocation probability 0·8) to receive either placebo or combination treatment consisting of a slow infusion of 20 mg/kg ferric carboxymaltose, 40 000 U subcutaneous erythropoietin alpha, 1 mg subcutaneous vitamin B12, and 5 mg oral folic acid or placebo on the day before surgery. Primary outcome was the number of RBC transfusions during the first 7 days. This trial is registered with ClinicalTrials.gov, number NCT02031289. Between Jan 9, 2014, and July 19, 2017, 1006 patients were enrolled; 505 with anaemia or isolated iron deficiency and 501 in the registry. The combination treatment significantly reduced RBC transfusions from a median of one unit in the placebo group (IQR 0–3) to zero units in the treatment group (0–2, during the first 7 days (odds ratio 0·70 [95% CI 0·50–0·98] for each threshold of number of RBC transfusions, p=0·036) and until postoperative day 90 (p=0·018). Despite fewer RBC units transfused, patients in the treatment group had a higher haemoglobin concentration, higher reticulocyte count, and a higher reticulocyte haemoglobin content during the first 7 days (p≤0·001). Combined allogeneic transfusions were less in the treatment group (0 [IQR 0–2]) versus the placebo group (1 [0–3]) during the first 7 days (p=0·038) and until postoperative day 90 (p=0·019). 73 (30%) serious adverse events were reported in the treatment group group versus 79 (33%) in the placebo group. An ultra-short-term combination treatment with intravenous iron, subcutaneous erythropoietin alpha, vitamin B12, and oral folic acid reduced RBC and total allogeneic blood product transfusions in patients with preoperative anaemia or isolated iron deficiency undergoing elective cardiac surgery. Vifor Pharma and Swiss Foundation for Anaesthesia Research.

Nutrient amendment experiments at the boundary of the South Atlantic gyre reveal extensive regions in which nitrogen and iron are co-limiting, with other micronutrients also approaching co-deficiency; such limitations potentially increase phytoplankton community diversity. Moderating marine micronutrients Whether micronutrient co-limitation is pervasive in the ocean and whether it affects phytoplankton growth and productivity is poorly understood. Through a series of large-scale nutrient amendment experiments at the eastern boundary of the South Atlantic gyre, Thomas Browning and colleagues report extensive regions in which nitrogen and iron are co-limiting, with near co-deficiency of the trace metal cobalt and vitamin B 12 . These findings suggest that nitrogen–iron co-limitation is pervasive in the ocean and potentially increases phytoplankton community diversity. Nutrient limitation of oceanic primary production exerts a fundamental control on marine food webs and the flux of carbon into the deep ocean 1 . The extensive boundaries of the oligotrophic sub-tropical gyres collectively define the most extreme transition in ocean productivity, but little is known about nutrient limitation in these zones 1 , 2 , 3 , 4 . Here we present the results of full-factorial nutrient amendment experiments conducted at the eastern boundary of the South Atlantic gyre. We find extensive regions in which the addition of nitrogen or iron individually resulted in no significant phytoplankton growth over 48 hours. However, the addition of both nitrogen and iron increased concentrations of chlorophyll a by up to approximately 40-fold, led to diatom proliferation, and reduced community diversity. Once nitrogen–iron co-limitation had been alleviated, the addition of cobalt or cobalt-containing vitamin B 12 could further enhance chlorophyll a yields by up to threefold. Our results suggest that nitrogen–iron co-limitation is pervasive in the ocean, with other micronutrients also approaching co-deficiency. Such multi-nutrient limitations potentially increase phytoplankton community diversity.

Rumen microbiome biology gets a boost with the release of 410 high-quality reference genomes from the Hungate1000 project. Productivity of ruminant livestock depends on the rumen microbiota, which ferment indigestible plant polysaccharides into nutrients used for growth. Understanding the functions carried out by the rumen microbiota is important for reducing greenhouse gas production by ruminants and for developing biofuels from lignocellulose. We present 410 cultured bacteria and archaea, together with their reference genomes, representing every cultivated rumen-associated archaeal and bacterial family. We evaluate polysaccharide degradation, short-chain fatty acid production and methanogenesis pathways, and assign specific taxa to functions. A total of 336 organisms were present in available rumen metagenomic data sets, and 134 were present in human gut microbiome data sets. Comparison with the human microbiome revealed rumen-specific enrichment for genes encoding de novo synthesis of vitamin B 12 , ongoing evolution by gene loss and potential vertical inheritance of the rumen microbiome based on underrepresentation of markers of environmental stress. We estimate that our Hungate genome resource represents ∼75% of the genus-level bacterial and archaeal taxa present in the rumen.

Over 30 years, the Gram-positive bacterium Priestia megaterium (previously known as Bacillus megaterium) was systematically developed for biotechnological applications ranging from the production of small molecules like vitamin B12, over polymers like polyhydroxybutyrate (PHB) up to the in vivo and in vitro synthesis of multiple proteins and finally whole-cell applications. Here we describe the use of the natural vitamin B12 (cobalamin) producer P. megaterium for the elucidation of the biosynthetic pathway and the subsequent systematic knowledge-based development for production purposes. The formation of PHB, a natural product of P. megaterium and potential petro-plastic substitute, is covered and discussed. Further important biotechnological characteristics of P. megaterium for recombinant protein production including high protein secretion capacity and simple cultivation on value-added carbon sources are outlined. This includes the advanced system with almost 30 commercially available expression vectors for the intracellular and extracellular production of recombinant proteins at the g/L scale. We also revealed a novel P. megaterium transcription-translation system as a complementary and versatile biotechnological tool kit. As an impressive biotechnology application, the formation of various cytochrome P450 is also critically highlighted. Finally, whole cellular applications in plant protection are completing the overall picture of P. megaterium as a versatile giant cell factory.Key points• The use of Priestia megaterium for the biosynthesis of small molecules and recombinant proteins through to whole-cell applications is reviewed.• P. megaterium can act as a promising alternative host in biotechnological production processes.

A growing body of evidence indicates that gut microbiota influence brain function and behaviour. However, the molecular basis of how gut bacteria modulate host nervous system function is largely unknown. Here we show that vitamin B 12 -producing bacteria that colonize the intestine can modulate excitatory cholinergic signalling and behaviour in the host Caenorhabditis elegans . Here we demonstrate that vitamin B 12 reduces cholinergic signalling in the nervous system through rewiring of the methionine (Met)/ S -adenosylmethionine cycle in the intestine. We identify a conserved metabolic crosstalk between the methionine/ S -adenosylmethionine cycle and the choline-oxidation pathway. In addition, we show that metabolic rewiring of these pathways by vitamin B 12 reduces cholinergic signalling by limiting the availability of free choline required by neurons to synthesize acetylcholine. Our study reveals a gut–brain communication pathway by which enteric bacteria modulate host behaviour and may affect neurological health. Kang et al. find that vitamin B 12 from gut bacteria modulates host neural function and behaviour in Caenorhabditis elegans : vitamin B 12 rewires the methionine/ S -adenosylmethionine cycle and choline metabolism, impacting free choline levels for neuronal acetylcholine synthesis.