Effects of increasing amounts of extruded linseed in the diet on apparent ruminal synthesis of some B vitamins in dairy cows

Many studies have shown that metabolic efficiency of ruminants can be significantly decreased when B-vitamin supply is insufficient. Under the present state of knowledge, the amounts of B vitamins available for intestinal absorption cannot be predicted based on diet composition. Therefore, in an attempt to increase our understanding of the effects of dietary factors, on B-vitamin supply for dairy cows, the effects of increasing amounts of extruded linseed in diets based on hay (permanent grassland hay, H; Experiment 1) or corn silage (CS; Experiment 2) on apparent ruminal synthesis (ARS) of thiamin, riboflavin, niacin, vitamin B₆, folates and vitamin B₁₂ were evaluated. In each experiment, four lactating Holstein cows fitted with cannulas in the rumen and the proximal duodenum were used in a 4 × 4 Latin square design. In both experiments, the dietary treatments consisted of an increasing supply of extruded linseed representing 0%, 5%, 10% or 15% of diet DM. The forage : concentrate ratios were 50 : 50 and 60 : 40 for Experiments 1 and 2, respectively. Duodenal flow was determined using YbCl₃ as a marker. The ARS of each B vitamin was calculated as duodenal flow – daily intake. In both experiments, treatments did not affect thiamin, riboflavin, niacin and vitamin B₁₂ duodenal flow or ARS. Increasing the dietary concentration of extruded linseed decreased folate intake in Experiment 1 and vitamin B₆ intake in Experiment 2 but resulted in a greater duodenal flow of vitamin B₆ and folates regardless of the forage used in basal diet. Greater dietary linseed concentrations decreased vitamin B₆ apparent degradation in the rumen in CS-based diet only and increased folate ARS in both H- and CS-based diets. Increasing linseed concentration of isonitrogenous and isoenergetic diets increased vitamin B₆ and folate supply to dairy cows, both with H- and CS-based diets.     

Analyses of constituents of feces and the effect of a vitamin B12 fortified diet on coprophagy in the mouse

In order to investigate coprophagy from the viewpoint of nutrition, fecal constituents were analyzed in freeze-dried samples. Feces were collected from 7:00 to 11:00 and from 19:00 to 23:00. Inorganic elements and crude fibers per unit weight were 3-4 times more concentrated in feces than in basal diet, whereas, crude proteins, crude fats and nitrogen-free extract showed various degrees of reduction. There were no differences in these tendencies with sampling time. As for some B vitamins, feces collected from 7:00 to 11:00 contained 22-92% more vitamins than feces collected from 19:00 to 23:00. In comparison with the dietary concentration, vitamin B12 was increased by 124-197 times (520-730 micrograms/100 g) in feces collected between 7:00 and 11:00. Folic acid in feces collected between 7:00 and 11:00 was 10 times greater than that in the diet. On the basis of the findings on vitamins, the effect of a vitamin B12 fortified diet (1,350 micrograms/100 g) on coprophagy was examined. Mean frequency of coprophagy per animal per day was 9.6 when animals were fed on the basal diet, whereas the frequency was immediately and significantly (p less than 0.05 approximately p less than 0.01) reduced to 4.7 after the diet had been replaced by the fortified one. However, coprophagy was not completely inhibited by vitamin B12 fortification. This indicates that some nutrient(s) in feces other than vitamin B12 might be of use to the host, and that otherwise, coprophagy might be a basically habitual form of behavior. Furthermore, under the fortified diet, the frequency of coprophagy increased gradually.(ABSTRACT TRUNCATED AT 250 WORDS)     

NUTRITION OF PLATYDORINA CAUDATA KOFOID

The vitamins p-aminobenzoic acid, thiamine, biotin, nicotinamide, and B₁₂ were tested for their ability to stimulate growth. Only vitamin B₁₂ was required. Urea and NaNO₂ supported excellent growth, although sodium nitrite, ammonium nitrate, and the Casamino acids supported only fair growth. Platydorina grew aerobically in the absence of an exogenous source of carbon; however a carbon source was required for anaerobic growth. Of 25 carbon compounds examined, isocitrate supported anaerobic growth in the light equalling the aerobic controls. Growth did not occur aerobically or anaerobically in the dark with any carbon source examined. Growth was excellent at pH values in excess of 7.0. Growth at pH 10.0 was 4 times that at 7.0 in strain I.U. 850 and twice that at 7.0 in strain Kan-3E. Growth was accelerated with the increase in temperatures but this increase may well be due to the increased intensity of light to which the cultures were exposed at the higher terperatures.     

Impact of diet management and composition on vitamin B12 concentration in milk of Holstein cows

As vitamin B₁₂ is only synthesized by bacteria, ruminant products, especially dairy products, are excellent sources of this vitamin. This study aims to identify if diet and cow characteristics could affect vitamin B₁₂ concentration in milk of dairy cows. Information on 1484 first, 1093 second and 1763 third and greater parity Holstein cows in 100 herds was collected during three consecutive milkings. During the first morning milking, all dietary ingredients given to cows were sampled and quantities offered were recorded throughout the day. Nutrient composition of ingredients was obtained by wet chemistry to reconstitute nutrient composition of the ration. Milk samples were taken with in-line milk meters during the evening milking of the 1^st day and the morning milking of the 2nd day and were analyzed for vitamin B₁₂ concentration. Milk yields were recorded and milk components were separately analyzed for each milking. Daily vitamin B₁₂ concentration in milk was obtained using morning and evening vitamin B₁₂ concentrations weighted with respective milk yield, then divided by daily yield. To decrease the number of interdependent variables to include in the multivariable model, a principal component analysis was carried out. Daily milk concentration of vitamin B₁₂ averaged 3809±80 pg/ml, 4178±79 pg/ml and 4399±77 pg/ml for first, second and third, and greater lactation cows. Out of 11 principal components, six were significantly related to daily milk concentration of vitamin B₁₂ when entered in the multivariable model. Results suggested that vitamin B₁₂ concentration in milk was positively related to percentage of fiber and negatively related to starch as well as energy of the diet. Negative relationships were noted between vitamin B₁₂ concentration in milk and milk yield as well as milk lactose concentration and positive relationships were observed between vitamin B₁₂ concentration in milk and milk fat as well as protein concentrations. The percentages of chopped mixed silage and commercial energy supplement in the diet as well as cow BW were positively related to vitamin B₁₂ in milk and percentages of baled mixed silage, corn and commercial protein supplement in the ration were negatively related to vitamin B₁₂ concentration in milk. The pseudo-R² of the model was low (52%) suggesting that diet and cow characteristics have moderate impact on vitamin B₁₂ concentration in milk. Moreover, when entering solely the principal component related to milk production in the model, the pseudo-R² was 46%. In conclusion, it suggests that studied diet characteristics have a marginal impact on vitamin B₁₂ concentration in milk variation.     

Oxidation of compounds metabolized through folate coenzyme pathways in vitamin B12-deficient rats

The effects of vitamin B₁₂ deficiency in rats and dietary supplementation with vitamin B₁₂ and/or l-methionine plus folate on the oxidation of compounds metabolized through folate coenzyme pathways were investigated. Rats fed a vitamin B₁₂-deficient diet oxidized significantly lower amounts in 60 min of l-histidine, glycine, sarcosine, formate, and l-serine to CO₂ than vitamin B₁₂-supplemented controls. Supplementation of the deficient diet with l-methionine plus folate restored the ability to oxidize the ring-2-carbon of l-histidine, the methyl group of sarcosine, and formate to the same level as that observed in animals receiving vitamin B₁₂. In contrast, oxidation of the 1-carbon of glycine and the 3-carbon of l-serine was not restored to control levels by addition of methionine plus folate to the vitamin B₁₂-deficient diet. Inhibition of the metabolism of the 2-carbon of glycine to CO₂ was partially overcome by additional dietary methionine and folate. Glycine synthase activity in homogenates paralleled the in vivo pattern of oxidation of the 1-carbon of glycine to CO₂, whereas sarcosine dehydrogenase activity appeared to increase 2-fold in vitamin B₁₂ deficiency.     

The Physiology of Astrephomene gubernaculifera1

SYNOPSIS. A comparative physiologic study of 4- and 7-chromosome strains of Astrephomene gubernaculifera was done. The vitamins p-aminobenzoic acid, nicotinamide, biotin, thiamin HCl and vitamin B₁₂ were tested for their ability to support growth. Only vitamin B₁₂ was required for active growth altho the presence of thiamin HCl was necessary to produce structurally typical colonies. Astrephomene will not grow in the absence of an exogenous source of carbon. Of the 36 carbon sources tested, only pyruvate, butyrate, succinate and acetate permitted active growth. Sodium acetate was the best. Strains grew within the initial pH range of 5.0–7.5. At pH values above 8.0 growth declined rapidly. When media were buffered with TES (N-tris [hydroxymethyl]methyl-2-aminoethane-sulfonic acid) at an initial pH of 6.8 growth was enhanced. The organism grew at 15–40 C. Growth in the dark was slightly less than that in the light.     

PRODUCTION OF VITAMIN B12, THIAMINE,AND BIOTIN BY PHYTOPLANKTON1

Some ecologically important phytoplankters released vitamins into culture medium during growth. Skeletonema costatum and Stephanopyxis turris (vitamin B₁₂-requirers) produced both thiamine (vitamin B₁) and biotin when growing with either 12 or 2 ng vitamin B₁₂/liter. Gonyaulax polyedra (vitamin B₁₂-requirer) produced thiamine with 12 ng vitamin B₁₂/liter, and Coccolithus huxleyi (thiamine-requirer) produced vitamin B₁₂ and biotin with 120 ng thiamine/liter, but only biotin with 10 ng thiamine/liter. The amount of vitamin produced by an alga and rate at which it was produced varied with the phytoplankter, the concentration of the required vitamin, and incubation time. Vitamins produced during early and exponential growth were due to excretions, and those produced at stationary growth resulted from excretion and release due to cell lysis. Uptake of the required vitamin by all phytoplankters was greatest during the first few days of incubation. On continued incubation the rate of uptake/cell decreased. In the sea phytoplankters may contribute a major portion of the amount of dissolved vitamins.     

ASSESSMENT OF INTAKE AND NUTRITIONAL STATUS OF VITAMIN B1, B2, AND B6 IN MEN AND WOMEN WITH DIFFERENT PHYSICAL ACTIVITY LEVELS

The purpose of the present study was to examine the nutritional status of vitamin B₁, B₂, and B₆ in respect to dietary intake of these vitamins and activity coefficients of the erythrocyte enzymes transketolase, glutathione reductase, and aspartic aminotransferase in young men and women with different physical activity levels. The participants of this study were 20 women and 20 men with high physical activity (groups HAW and HAM, respectively), and 20 women and 20 men with low physical activity (groups LAW and LAM, respectively). The intake of vitamins B₁, B₂, B₆, proteins, and calorie content of the diet was based on the average of the 4-day dietary recalls. To assess nutritional status of vitamin B₁, B₂, and B₆, the activity coefficients (α) of erythrocyte transketolase (ETK), erythrocyte glutathione reductase (EGR), and erythrocyte aspartic aminotransferase (EAST) were estimated in blood hemolysates. The intake of the studied vitamins in the diet was statistically significantly lower in the female groups compared with the respective male groups. Deficiency of vitamin B₆ in the diet was present more often in women than in men (in terms of the recommended dietary allowances [RDA]). Values of the activity coefficient α_ETK indicated that none of the groups in this study suffered the risk of vitamin B₁ deficiency. The value of the activity coefficient α_EGR indicated that the groups of women and men with low physical activity were more prone to vitamin B₂ deficiency compared with the high physical activity groups. The risk of vitamin B₆ deficiency (α_EAST) in both male groups was higher than in both female groups. The obtained results do not allow for unequivocal determination of the impact of sex and the level of physical activity on intake and nutritional status of vitamin B₁, B₂, and B₆. Independently of sex and the level of physical activity, the women and men consumed insufficient quantities of vitamins B₁ and B₆, although this was not always related to increased values of corresponding activity coefficients.     

Enrichment of some B-vitamins in plants with application of organic fertilizers

A review of the literature showed that plants grown with organic fertilizers often contain higher concentrations of vitamins B₁ (thiamin) and B₁₂ (cyanocobalamin) as compared with plants grown with inorganic fertilizers. Since plant roots were recently shown to be able to absorb B₁ and B₁₂, it was thus suspected that organic fertilizers (such as manure of diverse sources or sewage sludges which often contain relatively high concentrations of several vitamins) introduce additional vitamins into the soil which in turn leads to increased vitamins in the plants. This possibility was studied by measuring the B₁₂ content in the seeds of soybean and barley and in the leaves of spinach plants grown in soils amended with pure B₁₂ or cow dung (which is naturally rich in B₁₂). The addition of pure B₁₂ or cow dung did not alter the B₁₂ content in the soybean seeds but significantly increased that in the barley kernels and in the spinach leaves. For example, the addition of cow dung at the rate of 10 g kg^–1 increased the B₁₂ content in barley kernels by more than threefold (from 2.6 to 9.1 ng g^–1 DW) and in spinach leaves by close to twofold (from 6.9 to 17.8 ng g^–1 DW). Long-term addition of organic fertilizers to the soil also significantly increased the soil content of this vitamin. Since plants cannot synthesize B₁₂ and thus plant foods are normally fully devoid of (or have very low concentrations of) this vitamin, the finding that plants grown with organic fertilizers may contain relatively higher concentrations of this vitamin may have nutritional consequences in that the consumption of these plants by humans would inadvertently increase their intake of this vitamin. This may be of special benefit to people living by choice or by necessity on strict vegetarian diets who are known to be in danger of B₁₂ deficiency.     

EFFECTS OF CERTAIN LIMITING CONDITIONS ON THE SYNTHESIS OF B VITAMINS BY YEAST

In yeast crops which were grown in the presence of various inhibitors, there was considerable variation in content of the various B vitamins. A higher degree of parallelism in variation in content was found to exist between thiamine and niacin than between any other pair of vitamins; this has been interpreted as indicating that the predominant functions of these two vitamins are their established rôles in fermentation. Values for inositol indicate that it may be involved in fermentation processes, but this is not the case for other members of the B complex. Biotin appears to be unique since in no case did the biotin content of yeast grown in the presence of an inhibitor fall below that of the control yeast. There was some evidence of synthesis of biotin, or a material with biotin activity, in the presence of certain inhibitors, the most striking instance being with sulfaguanidine. An exogenous supply of biotin was essential for extensive proliferation of F. B. yeast, and yeast grown in a medium to which biotin was the only added vitamin contained the B vitamins in amounts very similar to those found in the control yeast, the most marked differences being in increased vitamin B₆ and p-aminobenzoic acid contents. In the absence of biotin, significant amounts of all of the B vitamins except biotin were synthesized, both in the presence and absence of certain other members of the B complex. The addition of thiamine, pyridoxine, inositol, and β-alanine to the culture medium caused a reduction in the amounts of vitamin B₆ and p-aminobenzoic acid synthesized. F. B. yeast was able to grow in a xylose medium only when certain of the B vitamins were present, and even then growth was limited. Evidence was obtained for some synthesis of all of the vitamins investigated except biotin and vitamin B₆. The most significant differences in vitamin content between galac yeast and the parent F. B. strain were in folic acid and vitamin B₆, the former being considerably reduced in amount, the latter being increased.     

Effects of maternal vitamin B12 deficiency from end of gestation to weaning on the growth and haematological and immunological parameters in mouse dams and offspring

Vitamin B₁₂-deficiency may induce specific symptoms as neurological alterations and unspecific symptoms such as anaemia and growth retardation. In this study, maternal vitamin B₁₂ deficiency from end of gestation to weaning was evaluated in mouse dams, which was provoked by feeding a vitamin B₁₂-deficient diet. The animals were divided into two groups (control and deficient). The control group received the vitamin B₁₂-deficient diet supplemented with commercial vitamin B₁₂. Compared to the control, the vitamin B₁₂-deficient dams and their offspring showed a significant decrease of body weight (by 20 and 39%, respectively), serum vitamin B₁₂ concentration (by 61 and 67%, respectively), haematological values as haematocrit (25 and 26%, respectively), and IgA producer cells (by 36 and 54%, respectively). In both, vitamin B₁₂-deficient mouse dams and their offspring, histological alterations of small intestine were observed, whereas growth retardation occurred in the offspring only. This experimental murine model allows assessing the incidence of maternal cobalamin deficiency in offspring and would be useful for evaluating novel adjuncts such as functional foods to prevent vitamin B₁₂ deficiency.     

Relationships between biotin and vitamin B12. Effects of biotin and vitamin B12 on folic acid metabolism

1. The effects of dietary biotin compared with vitamin B₁₂ on the total content and on the distribution of the various folate derivatives in the liver of rats given a biotin-free diet have been studied. The effect of both vitamins on the conversion in vitro of folic acid into citrovorum factor in the same experimental conditions was also examined. 2. In biotin-treated rats as well as in vitamin B₁₂-treated rats the total content of folic acid-active substances measured microbiologically by Pediococcus cerevisiae, Streptococcus faecalis and Lactobacillus casei is significantly higher than that in biotin-deficient rats. The liver distribution of various folate derivatives in the three groups of animals is also markedly modified. 3. The amount of citrovorum factor formed in systems with liver homogenate of rats receiving biotin or vitamin B₁₂ is higher than that with liver homogenates of deficient rats. 4. The results obtained demonstrate the influence of biotin in the metabolism of folic acid, and the similar actions at this level of both biotin and vitamin B₁₂. These results are discussed in relation to the participation of the two vitamins in the metabolism of C₁ units, as a biochemical interpretation of the relationships between vitamin B₁₂ and biotin.     

Life's utilization of B vitamins on early Earth

Coenzymes are essential across all domains of life. B vitamins (B₁‐thiamin, B₂‐riboflavin, B₃‐niacin, B₅‐pantothenate, B₆‐pyridoxine, B₇‐biotin, and B₁₂‐cobalamin) represent the largest class of coenzymes, which participate in a diverse set of reactions including C₁‐rearrangements, DNA repair, electron transfer, and fatty acid synthesis. B vitamin structures range from simple to complex heterocycles, yet, despite this complexity, multiple lines of evidence exist for their ancient origins including abiotic synthesis under putative early Earth conditions and/or meteorite transport. Thus, some of these critical coenzymes likely preceded life on Earth. Some modern organisms can synthesize their own B vitamins de novo while others must either scavenge them from the environment or establish a symbiotic relationship with a B vitamin producer. B vitamin requirements are widespread in some of the most ancient metabolisms including all six carbon fixation pathways, sulfate reduction, sulfur disproportionation, methanogenesis, acetogenesis, and photosynthesis. Understanding modern metabolic B vitamin requirements is critical for understanding the evolutionary conditions of ancient metabolisms as well as the biogeochemical cycling of critical elements such as S, C, and O.     

Vitamin‐regulated cytokines and growth factors in the CNS and elsewhere

There is a growing awareness that natural vitamins (with the only exception of pantothenic acid) positively or negatively modulate the synthesis of some cytokines and growth factors in the CNS, and various mammalian cells and organs. As natural vitamins are micronutrients in the human diet, studying their effects can be considered a part of nutritional genomics or nutrigenomics. A given vitamin selectively modifies the synthesis of only a few cytokines and/or growth factors, although the same cytokine and/or growth factor may be regulated by more than one vitamin. These effects seem to be independent of the effects of vitamins as coenzymes and/or reducing agents, and seem to occur mainly at genomic and/or epigenetic level, and/or by modulating NF‐κB activity. Although most of the studies reviewed here have been based on cultured cell lines, but their findings have been confirmed by some key in vivo studies. The CNS seems to be particularly involved and is severely affected by most avitaminoses, especially in the case of vitamin B₁₂. However, the vitamin‐induced changes in cytokine and growth factor synthesis may initiate a cascade of events that can affect the function, differentiation, and morphology of the cells and/or structures not only in the CNS, but also elsewhere because most natural vitamins, cytokines, and growth factors cross the blood–brain barrier. As cytokines are essential to CNS‐immune and CNS‐hormone system communications, natural vitamins also interact with these circuits. Further studies of such vitamin‐mediated effects could lead to vitamins being used for the treatment of diseases which, although not true avitaminoses, involve an imbalance in cytokine and/or growth factor synthesis.     

Common variant in FUT2 gene is associated with levels of vitamin B12 in Indian population

Vitamin B₁₂ is an essential micronutrient synthesized by microorganisms. Mammals including humans have evolved ways for transport and absorption of this vitamin. Deficiency of vitamin B₁₂ (either due to low intake or polymorphism in genes involved in absorption and intracellular transport of this vitamin) has been associated with various complex diseases. Genome-wide association studies have recently identified several common single nucleotide polymorphisms (SNPs) in fucosyl transferase 2 gene (FUT2) to be associated with levels of vitamin B₁₂—the strongest association was with a non-synonymous SNP rs602662 in this gene. In the present study, we attempted to replicate the association of this SNP (rs602662) in an Indian population since a significant proportion has been reported to have low levels of vitamin B₁₂ in this population. A total of 1146 individuals were genotyped for this SNP using a single base extension method and association with levels of vitamin B₁₂ was assessed in these individuals. Regression analysis was performed to analyze the association considering various confounding factors like for age, sex, diet, hypertension, diabetes mellitus and coronary artery disease status. We found that the SNP rs602662 was significantly associated with the levels of vitamin B₁₂ (p value < 0.0001). We also found that individuals adhering to a vegetarian diet with GG (homozygous major genotype) have significantly lower levels of vitamin B₁₂ in these individuals. Thus, our study reveals that vegetarian diet along with polymorphism in the FUT2 gene may contribute significantly to the high prevalence of vitamin B₁₂ deficiency in India.     

SECRETION OF VITAMINS AND AMINO ACIDS INTO THE ENVIRONMENT BY OCHROMONAS DANICA1,2

Ochromonas danica grown on a chemically defined medium under controlled conditions in the light synthesized the following vitamins: ascorbate, B₆, N⁵-methyltetrahydrofolate, tetrahydrofolate polyglutamates, oxidized folate monoglutamates, nicotinate, pantothenate, riboflavin, vitamin A, β-carotene, and vitamin E but no vitamin. B₁₂. The cells also secreted molecules into their growth medium including the vitamins ascorbate, B₆, the above folates, nicotinate, pantothenate, riboflavin, vitamin E, and the amino acids alanine, aspartic acid, leucine, and valine. The role of such secretions in nature is discussed.     

Combined Vitamins B12b and C Induce the Glutathione Depletion and the Death of Epidermoid Human Larynx Carcinoma Cells HEp-2

The combination of hydroxocobalamin (vitamin B_12b) and ascorbicacid (vitamin C) can cause the death of tumor cells at the concentrationsof the components at which they are nontoxic when administeredseparately. This cytotoxic action on epidermoid human larynx carcinomacells HEp-2 in vitro is shown to be due to the hydrogen peroxidegenerated by the combination of vitamins B_12b and C. The drop inthe glutathione level preceding cell death was found to be the result ofcombined action of the vitamins. It is supposed that the induction of celldeath by combined action of vitamins B_12b and C is connected to the damageof the cell redox system.     

A comparison between different concentrations and sources of cobalt in goat kid nutrition

There have been extensive studies in sheep and cattle considering cobalt (Co) supplementation and its effects on vitamin B₁₂ concentrations in the body. However, there are limited studies on goats. The aim of this study was to compare two different sources of Co (sulfate v. glucoheptonate) at two different concentrations (0.25 and 0.5 mg/kg dry matter) in goat kid nutrition, and to evaluate the effects of these supplements on performance, serum vitamin B₁₂, blood biochemistry and rumen volatile fatty acids. For this purpose, 30 weaned male goat kids were randomly allotted to five treatments. Serum vitamin B₁₂ increased during the trial in the Co-supplemented groups. Co supplementation increased serum glucose concentrations. On day 35, Co-supplemented groups had greater glucose concentrations compared with control. Propionic+iso-butyric acid concentrations increased only in the 0.5 mg Co glucoheptonate treatment (P<0.05). Our results suggest that, despite the two sources of Co proving mostly similar, the main advantage of Co glucoheptonate compared with Co sulfate was in the ruminal synthesis of vitamin B₁₂. However, although providing Co at National Research Council recommendation levels maintained vitamin B₁₂ above or at normal concentrations, Co supplementation of the Co sufficient basal diet increased vitamin B₁₂ and glucose concentrations.     

Influence of Vitamin B12 and Cocultures on the Growth of Dehalococcoides Isolates in Defined Medium

Bacteria belonging to the genus Dehalococcoides play a key role in the complete detoxification of chloroethenes as these organisms are the only microbes known to be capable of dechlorination beyond dichloroethenes to vinyl chloride (VC) and ethene. However, Dehalococcoides strains usually grow slowly with a doubling time of 1 to 2 days and have complex nutritional requirements. Here we describe the growth of Dehalococcoides ethenogenes 195 in a defined mineral salts medium, improved growth of strain 195 when the medium was amended with high concentrations of vitamin B₁₂, and a strategy for maintaining Dehalococcoides strains on lactate by growing them in consortia. Although strain 195 could grow in defined medium spiked with ~0.5 mM trichloroethene (TCE) and 0.001 mg/liter vitamin B₁₂, the TCE dechlorination and cellular growth rates doubled when the vitamin B₁₂ concentration was increased 25-fold to 0.025 mg/liter. In addition, the final ratios of ethene to VC increased when the higher vitamin concentration was used, which reflected the key role that cobalamin plays in dechlorination reactions. No further improvement in dechlorination or growth was observed when the vitamin B₁₂ concentration was increased to more than 0.025 mg/liter. In defined consortia containing strain 195 along with Desulfovibrio desulfuricans and/or Acetobacterium woodii and containing lactate as the electron donor, tetrachloroethene (~0.4 mM) was completely dechlorinated to VC and ethene and there was concomitant growth of Dehalococcoides cells. In the cultures that also contained D. desulfuricans and/or A. woodii, strain 195 cells grew to densities that were 1.5 times greater than the densities obtained when the isolate was grown alone. The ratio of ethene to VC was highest in the presence of A. woodii, an organism that generates cobalamin de novo during metabolism. These findings demonstrate that the growth of D. ethenogenes strain 195 in defined medium can be optimized by providing high concentrations of vitamin B₁₂ and that this strain can be grown to higher densities in cocultures with fermenters that convert lactate to generate the required hydrogen and acetate and that may enhance the availability of vitamin B₁₂.