Search

Dietary flavanols are known for disease preventative properties but are often poorly absorbed. Gut microbiome flavanol metabolites are more bioavailable and may exert protective activities. Using metabolite mixtures extracted from the urine of rats supplemented with flavanols and treated with or without antibiotics, we investigated their effects on INS-1 832/13 β-cell glucose stimulated insulin secretion (GSIS) capacity. We measured insulin secretion under non-stimulatory (low) and stimulatory (high) glucose levels, insulin secretion fold induction, and total insulin content. We conducted treatment-level comparisons, individual-level dose responses, and a responder vs. non-responder predictive analysis of metabolite composition. While the first two analyses did not elucidate treatment effects, metabolites from 9 of the 28 animals demonstrated significant dose responses, regardless of treatment. Differentiation of responders vs. non-responder revealed that levels of native flavanols and valerolactones approached significance for predicting enhanced GSIS, regardless of treatment. Although treatment-level patterns were not discernable, we conclude that the high inter-individual variability shows that metabolite bioactivity on GSIS capacity is less related to flavanol supplementation or antibiotic treatment and may be more associated with the unique microbiome or metabolome of each animal. These findings suggest flavanol metabolite activities are individualized and point to the need for personalized nutrition practices.

Purified diets (PDs) contain refined ingredients with one main nutrient, allowing for greater control relative to grain-based diets (GBDs), which contain unrefined grains and animal byproducts. Traditional PDs like the American Institute of Nutrition (AIN)-76A (76A) and AIN-93G (93G) can negatively impact metabolic and gut health when fed long term, in part due to lower total fiber, no soluble fiber, and higher sucrose content.Two studies were conducted to determine how PDs with reduced sucrose and increased fiber (soluble and insoluble) influence metabolic and gut health in mice compared with traditional AIN PDs or GBDs.In study 1, C57Bl/6N mice (The PD with 75 g cellulose and 25 g inulin per 4084 kcals marginally influenced body weight and adiposity, but improved glucose tolerance relative to 93G (PDs formulated with lower sucrose and increased fiber content, particularly soluble fiber, blunted elevations in metabolic parameters and favorably impacted the microbiota and metagenome in C57BL/6N mice.

This study assessed the impact of caffeic and ferulic acid complexation with maize amylopectin or potato starch on glycemic parameters. In comparison to starch-phenolic mixtures, starch-phenolic complexes resulted in significant modification of phenolic bioaccessibility and cellular uptake (

Gut bacteria release trimethylamine (TMA) from dietary substrates. TMA is absorbed and is subsequently oxidized in the liver to produce trimethylamine N‐oxide (TMAO). Plasma TMAO levels are positively correlated with risk for type 2 diabetes (T2D) and cardiovascular disease (CVD). High‐fat diet (HFD) consumption has been reported to increase fasting and postprandial TMAO in sedentary individuals. However, whether the increase in TMAO with consumption of an HFD is observed in endurance‐trained males is unknown. Healthy, sedentary (n = 17), and endurance‐trained (n = 7) males consumed a 10‐day eucaloric diet comprised of 55% carbohydrate, 30% total fat, and 0.05) in the sedentary and endurance‐trained group, respectively. VO2max was significantly higher in the endurance‐trained compared with sedentary males (56.7 ± 8.2 vs. 39.9 ± 6.0 ml/kg/min). Neither the HFC nor the HFD evoked a detectable change in plasma TMAO (p > 0.05) in either group. Future studies are needed to identify the effects of endurance training on TMAO production., Plasma trimethylamine N‐oxide (TMAO) levels are positively correlated with risk for cardiovascular disease and consumption of a high‐fat diet has been reported to increase TMAO. Healthy, sedentary (n = 17), and endurance‐trained (n = 7) males consumed a 10‐day eucaloric diet and a 5‐day high‐fat diet. There were no significant differences in fasting (p > 0.05) or postprandial TMAO (p > 0.05) between sedentary and endurance‐trained individuals before or following the high‐fat diet, despite the endurance‐trained group consuming more dietary precursors.

Multiple analytical methods are used for quantification of total polyphenols and total flavanols in fruit juices and beverages. Four methods were evaluated in this study: Folin-Ciocalteu (F-C), Lowenthal permanganate (L-P), 4-dimethylaminocinnamaldehyde (DMAC), and the bovine serum albumin (BSA) precipitation method. Method validation parameters, including working range, limit of detection, limit of quantitation, precision (repeatability), accuracy, and specificity, were assessed and compared. The F-C method was not specific to polyphenols, and the L-P method had the widest working range but lacked accuracy. The DMAC method was the most specific to flavanols, and the BSA method was not suitable for quantification of smaller flavanols, such as catechin and epicatechin. Quantitative performance was evaluated using commercial fruit juice samples (n = 14), apple juice samples of different cultivars (n = 22), and commercial ciders (n = 17). In general, the L-P titration method and DMAC method resulted in higher quantitative values than the F-C method and BSA precipitation method, respectively. However, ratios of results obtained by the L-P and F-C method ranged from 1 to 28, and ratios of results obtained by the DMAC and BSA precipitation method ranged from

Weight gain and obesity are associated with increased levels of proinflammatory cytokines. Studies have demonstrated the ability of dietary flavanols to reduce the severity of metabolic derangements due to high-fat (HF) feeding. The degree of polymerization of the flavanols appears to play a role in determining the extent of these protective effects. This study evaluated the preventative effects of grape seed and pine bark flavanol supplementation, with significantly different flavanol degree of polymerization, in the context of an HF diet. For 13 weeks, mice were given 35 mg/kg body weight per day grape seed or pine bark as part of an HF diet and compared to mice fed a low-fat diet and control HF diet. All flavanol-supplemented groups and the HF control incurred significantly higher weight gain compared to the lean control, and the grape seed group gained significantly more weight than the HF control. Increased weight gain of treatment groups was likely caused by hyperphagia. Despite lack of improvements to weight gain and glycemic control, it was observed that all flavanol treatment groups were able to significantly reduce interleukin-6 compared to HF control. The grape seed group, which gained the most weight overall, also exhibited the lowest levels of interleukin-6 compared to other groups. Overall, low-dose flavanol extract supplementation, regardless of mean degrees of polymerization, blunted cytokine production despite increased weight gain. This obesity-independent effect suggests flavanols may be used as complementary interventions to ameliorate increased inflammatory tone in the contexts of obesity and diabetes. Furthermore, flavanol-induced hyperphagia may have use for attenuation of cachexia.

Dietary flavanols and their metabolites are excreted primarily via the urine, suggesting uroepithelial cells as a site of activity due to lengthy exposure to high concentrations of these compounds. Flavanols are metabolized by the gut microbiota to numerous bioavailable metabolites. The observed effects of flavanols, including cancer chemoprevention, may be due in part to the activities of microbial metabolites. Most in vitro mechanistic work in this area relies on a limited pool of commercially available or synthesized flavanol microbial metabolites, and little work has been done in the area of bladder cancer. The impact of physiologically relevant mixtures of native flavanols and their metabolites generated in vivo remains unknown. Rats were fed various flavanols after which 48 h urine samples, approximating the total bioavailable metabolome, were collected. Urine samples were profiled by UPLC-MS/MS, and their anti-proliferative activities were assayed in vitro in four bladder cancer cell models. Significant interindividual variability was observed for chemical profiles and anti-proliferative activities. Concentrations of microbial metabolites (valerolactones, phenylalkyl acids and hippuric acids) were positively associated with reduced bladder cancer cell proliferation in vitro, while native flavanols were poorly correlated with activity. These results suggest that microbial metabolites may be the primary compounds responsible for chemoprevention in uroepithelial cell following flavanol consumption. Furthermore, this highlights the potential for exploiting knowledge about individual genetics, microbiome profiles, flavonoid metabolism profiles, tumor characteristics, etc. to design personalized dietary interventions for cancer prevention and/or adjuvant therapy to reduce bladder cancer incidence and improve outcomes.

Significant evidence suggests protective effects of flavonoids against obesity in animal models, but these often do not translate to humans. One explanation for this disconnect is use of a few mouse strains (notably C57BL/6 J) in obesity studies. Obesity is a multifactorial disease. The underlying causes are not fully replicated by the high-fat C57BL/6 J model, despite phenotypic similarities. Furthermore, the impact of genetic factors on the activities of flavonoids is unknown. This study was designed to explore how diverse mouse strains respond to diet-induced obesity when fed a representative flavonoid. A subset of Collaborative Cross founder strains (males and females) were placed on dietary treatments (low-fat, high-fat, high-fat with quercetin, high-fat with quercetin and antibiotics) longitudinally. Diverse responses were observed across strains and sexes. Quercetin appeared to moderately blunt weight gain in male C57 and both sexes of 129S1/SvImJ mice, and slightly increased weight gain in female C57 mice. Surprisingly, quercetin dramatically blunted weight gain in male, but not female, PWK/PhJ mice. For female mice, quercetin blunted weight gain (relative to the high-fat phase) in CAST/PhJ, PWK/EiJ and WSB/EiJ mice compared to C57. Antibiotics did not generally result in loss of protective effects of quercetin. This highlights complex interactions between genetic factors, sex, obesity stimuli, and flavonoid intake, and the need to move away from single inbred mouse models to enhance translatability to diverse humans. These data justify use of genetically diverse Collaborative Cross and Diversity Outbred models which are emerging as invaluable tools in the field of personalized nutrition.

Raw cocoa beans were processed to produce cocoa powders with different combinations of fermentation (unfermented, cool, or hot) and roasting (not roasted, cool, or hot). Cocoa powder extracts were characterized and assessed for &alpha, glucosidase inhibitory activity in vitro. Cocoa processing (fermentation/roasting) contributed to significant losses of native flavanols. All of the treatments dose-dependently inhibited &alpha, glucosidase activity, with cool fermented/cool roasted powder exhibiting the greatest potency (IC50: 68.09 &micro, g/mL), when compared to acarbose (IC50: 133.22 &micro, g/mL). A strong negative correlation was observed between flavanol mDP and IC50, suggesting flavanol polymerization as a marker of enhanced &alpha, glucosidase inhibition in cocoa. Our data demonstrate that cocoa powders are potent inhibitors of &alpha, glucosidase. Significant reductions in the total polyphenol and flavanol concentrations induced by processing do not necessarily dictate a reduced capacity for &alpha, glucosidase inhibition, but rather these steps can enhance cocoa bioactivity. Non-traditional compositional markers may be better predictors of enzyme inhibitory activity than cocoa native flavanols.

Epidemiological and clinical studies suggest that grapes and grape-derived products may reduce the risk for chronic disease. Grape seed extract specifically has been gaining interest due to its reported ability to prevent weight gain, moderate hyperglycemia, and reduce inflammation. The purpose of this study was to examine the long-term effects of two doses of grape seed extract (10 and 100 mg kg−1 body wt per d in mice) on markers of metabolic syndrome in the context of a moderately high-fat diet. After 12 weeks, the lower dose of grape seed extract was more effective at inhibiting fat gain and improving glucose tolerance and insulin sensitivity. Neither the high fat diet nor grape seed extract altered skeletal muscle substrate metabolism. Most interestingly, when examining the profile of metabolically active microbiota in the mucosa of the small intestine, cecum, and colonic tissue, grape seed extract seemed to have the most dramatic effect on small intestinal tissue, where the population of Firmicutes was lower compared to control groups. This effect was not observed in the cecal or colonic tissues, suggesting that the main alterations to gut microbiota due to flavan-3-ol supplementation occur in the small intestine, which has not been reported previously. These findings suggest that grape seed extract can prevent early changes in glucose tolerance and alter small intestinal gut microbiota, prior to the onset of skeletal muscle metabolic derangements, when grape seed extract is consumed at a low dose in the context of a moderately high fat diet.

OBJECTIVES: Cocoa beans (Theobroma cacao) are a highly concentrated source of dietary flavanols that undergo processing steps, to enhance sensory characteristics. Although it is widely accepted that preservation of native cocoa flavanols is critical for retaining bioactivity, it is possible that reactions occurring throughout cocoa processing may generate compounds with novel activities, potentially preserving or enhancing bioactivity. Our objective was to evaluate the impact of fermentation and roasting on levels of flavanols and bioactivity of cocoa. METHODS: Combinations of fermentation and roasting parameters were employed via a controlled laboratory fermentation model system and roasting operation. Cocoa powders were produced from unfermented cocoa beans using different treatments representing extremes of fermentation and roasting. Cocoa beans were fermented in a simulated pulp media for 168 h. Fermentation and roasting temperatures varied depending on treatment group. Further processing (winnowing, grinding, pressing) produced cocoa powders for each treatment. Extracts were made from the final beans and powders. Total polyphenols were quantified by the Folin-Ciocalteu assay. HILIC UPLC-MS/MS was employed to analyze flavanols based on their degree of polymerization (DP). RESULTS: Fermentation and roasting contributed to losses of native flavanols. Total polyphenol levels and individual flavanols (DP 1–10) were approximately 27–90% lower in hot fermented/hot roasted cocoa powder and approximately 11–54% lower in cool fermented/cool roasted cocoa powder when compared to the unfermented/unroasted (control) treatment. Hot roasting had the most significant impact on flavanol degradation. There was also a direct relationship between increasing flavanol concentration in cocoa powder and DP. CONCLUSIONS: Compared to fermentation, roasting demonstrated a more significant impact on flavanol degradation and composition among cocoa bean treatments. Further research in vitro and in vivo is being performed currently to determine whether these process-induced flavanol losses correlate with reduced anti-obesity and anti-inflammatory activities. FUNDING SOURCES: This work was supported by the Agriculture and Food Research Initiative (AFRI) of the US Department of Agriculture.

An elevated circulating level of trimethylamine N-oxide (TMAO) has been identified as a risk factor for numerous diseases, including cardiovascular disease (CVD) and colon cancer. TMAO is formed from trimethylamine (TMA)-precursors such as choline via the combined action of the gut microbiota and liver. We conducted a Mediterranean diet intervention that increased intakes of fiber and changed intakes of many other foods containing fat to increase the relative amount of mono-unsaturated fats in the diet. The Mediterranean diet is associated with reduced risks of chronic diseases and might counteract the pro-inflammatory effects of increased TMAO formation. Therefore, the purpose of this study was to determine if the Mediterranean diet would reduce TMAO concentrations. Fasting TMAO concentrations were measured before and after six-months of dietary intervention in 115 healthy people at increased risk for colon cancer. No significant changes in plasma TMAO or in the ratios of TMAO to precursor compounds were found in either the Mediterranean group or the comparison group that followed a Healthy Eating diet. TMAO concentrations exhibited positive correlations with age and markers of metabolic health. TMAO concentrations were not associated with circulating cytokines, but the relative abundance of Akkermansia mucinophilia in colon biopsies was modestly and inversely correlated with baseline TMAO, choline, and betaine serum concentrations. These results suggest that broad dietary pattern intervention over six months may not be sufficient for reducing TMAO concentrations in an otherwise healthy population. Disruption of the conversion of dietary TMA to TMAO should be the focus of future studies.

Bitterness and astringency (dryness) are characteristic sensory attributes of flavanol-rich foods. The degree of polymerization (DP) of flavanols influences their bitter and astringent sensations. Smaller DP compounds can enter the papillae on the tongue, eliciting a bitter response. Larger DP compounds are sterically inhibited from entering papillae and instead interact with oral proteins, cause precipitation, and elicit astringent sensations. Previous research has indicated that bitterness preference is related to health status, density of fungiform papillae on the tongue, and sensitivity to bitter compounds such as 6-n-propyl-thiouracil (PROP). The purpose of this study was to examine trends in liking, bitterness intensity, and astringency intensity of wine-like products with flavanols of different DP using a consumer sensory panel. Participants (n = 102) were segmented by phenotypes: body fat percentage (BF%), body mass index (BMI), PROP sensitivity, and stated bitter food preference. Differences in wine liking, perceived bitterness intensity, and astringency intensity were observed between three model wine samples of varying flavanol mean degrees of polymerization (mDP, i.e. the average size (polymer length) of flavanol compounds in a mixture). Specifically, with increased mDP, overall liking and bitterness liking decreased, with concurrent increased perception of bitterness and astringency intensity. Greater differences between phenotypes were observed when participants were segmented by BF% and BMI classification, than when segmented by PROP sensitivity classification. Reduced ability to detect differences in bitterness and astringency were noted in participants of higher weight status. Overall, these data suggest that weight status in adults is a greater predictor of liking of flavanol-rich foods than bitterness sensitivity (as determined by PROP classification), and that reduced perception of bitterness and astringency associated with weight gain may impact selection and preference for these foods.

The gut microbiome metabolizes choline and carnitine to release trimethylamine (TMA), which subsequently undergoes hepatic conversion to trimethylamine N-oxide (TMAO). Elevated TMAO levels are associated with cardiovascular disease and all-cause mortality risk. Dietary flavanols modulate the composition and function of the gut microbiome. Therefore, the possibility exists that these compounds could reduce intestinal TMA production and lower circulating TMAO. However, this hypothesis has never been tested in humans. A secondary analysis was performed on blood samples from a clinical study in which obese subjects at risk for insulin resistance consumed tea or cocoa flavanols in a randomized crossover design while consuming a controlled diet. These subjects generally had elevated TMAO levels (approximate to 5 M) compared to levels previously measured in healthy subjects (approximate to 1 M). None of the interventions significantly altered TMAO levels. Individual variability for choline and carnitine was relatively low. However, TMAO exhibited somewhat greater inter-individual variability. No differences in mean TMAO concentrations observed across interventions were seen based on separating subjects by glycemic status, body mass index (BMI), race, age, or gender. However, subject minimum and maximum values observed across the interventions appeared to be more strongly associated with glycemic status and age than mean values across interventions, suggesting that average TMAO values over time may be less useful than maximum or minimum values as markers of disease risk. Traditional physiological characteristics do not appear to predict TMAO responsiveness to flavanol interventions. However, African-American subjects appeared less responsive compared to non-Hispanic white subjects for both green tea and high cocoa treatments, and female subjects appeared less responsive than males for the high cocoa treatment. The present results suggest that a short-term flavanol intervention does not generally reduce fasting TMAO levels in subjects with elevated circulating TMAO. Virginia Agricultural Experiment Station; Hatch Program of the National Institute of Food and Agriculture, U.S. Department of Agriculture; U.S. Department of AgricultureUnited States Department of Agriculture (USDA); Virginia Tech Translational Obesity Research Interdisciplinary Graduate Education program (TOR IGEP) Funding for the present work was provided, in part, by the Virginia Agricultural Experiment Station and the Hatch Program of the National Institute of Food and Agriculture, U.S. Department of Agriculture (APN, KPD). Funding for the original study was provided by the U.S. Department of Agriculture (DJB, JAN). Funding for LEG was provided by the Virginia Tech Translational Obesity Research Interdisciplinary Graduate Education program (TOR IGEP). Public domain – authored by a U.S. government employee

There is interest in the potential of cocoa flavanols, including monomers and procyanidins, to prevent obesity and type-2 diabetes. Fermentation and processing of cocoa beans influence the qualitative and quantitative profiles of individual cocoa constituents. Little is known regarding how different cocoa flavanols contribute to inhibition of obesity and type-2 diabetes. The objective of this study was to compare the impacts of long-term dietary exposure to cocoa flavanol monomers, oligomers, and polymers on the effects of high-fat feeding. Mice were fed a high-fat diet supplemented with either a cocoa flavanol extract or a flavanol fraction enriched with monomeric, oligomeric, or polymeric procyanidins for 12 weeks. The oligomer-rich fraction proved to be most effective in preventing weight gain, fat mass, impaired glucose tolerance, and insulin resistance in this model. This is the first long-term feeding study to examine the relative activities of cocoa constituents on diet-induced obesity and insulin resistance.

Directed transport of the mRNA binding protein, zipcode binding protein1 (ZBP1), into developing axons is believed to play an important role in mRNA localization and local protein synthesis. The role of molecular motors in this process is unclear. We elucidated a role for myosin Va (MyoVa) to modulate the axonal localization and transport of ZBP1 in axons. Using cultured rat hippocampal neurons, ZBP1 colocalized with MyoVa in axons and growth cones. Interaction of MyoVa with ZBP1 was evident by coimmunoprecipitation of endogenous and overexpressed proteins. Inhibition of MyoVa function with the globular tail domain (GTD) of MyoVa protein or short hairpin RNA led to an accumulation of ZBP1 in axons. Live cell imaging of mCherryZBP1 in neurons expressing GTD showed an increase in the number of motile particles, run length, and stimulated anterograde moving ZBP1 particles, suggesting that MyoVa controls availability of ZBP1 for microtubule-dependent transport. These findings suggest a novel regulatory role for MyoVa in the transport of ZBP1 within axons.

Cashew nuts are the second most popular tree nut in the US with sales growing at a rate of 7% per annum. The highest quality cashew nuts are traditionally whole, oil-roasted, and devoid of skins. The development of a technique to remove the caustic cashew nut shell liquid from cashews and leave the skins intact allows for the production of novel cashew products including skin-on or “wrapped” in addition to raw and dry roasted products. This study investigated the nutritional characteristics of these newer cashew products. These products were found to contain bioactive compounds including mono- and poly-unsaturated fatty acids, phytosterols, arginine, magnesium, tocopherols, and phenolic compounds. All the types of cashews exhibited higher levels of phytosterols than the amounts reported for other tree nuts. The skin-on cashews had higher levels of phenolic compounds compared to the other cashew varieties tested, indicating additional health benefits of consuming cashew nuts with skins.

A lexicon of flavor and texture terms was developed to describe the sensory characteristics of cashew nuts. A highly trained and experienced descriptive analysis panel (n = 10, ages 22–58 each with at least 60 hr of descriptive work in nuts) was used to create the lexicon for cashews. After initial identification and discussion of terms, 22 flavor terms, 4 texture terms, and 3 feeling factors to describe the sensory attributes of cashews were identified. The lexicon was validated by demonstrating that the panel could detect differences among 18 different cashew samples, including raw, oil-roasted, dry-roasted, skin-on, store-brand, national-brand, and rancid types when using the identified lexicon. The differences in products were analyzed using analysis of variance and principal component analysis. Differences in flavor and texture were observed across all product categories and the lexicon was validated. Practical applications The lexicon is intended for use in cashew research and by the cashew industry as a way for communicating differences in cashew flavor and texture in a common language.

Animal studies have demonstrated the potential of grape seed extract (GSE) to prevent metabolic syndrome, obesity, and type 2 diabetes. Recently, metabolic endotoxemia induced by bacterial endotoxins produced in the colon has emerged as a possible factor in the etiology of metabolic syndrome. Improving colonic barrier function may control endotoxemia by reducing endotoxin uptake. However, the impact of GSE on colonic barrier integrity and endotoxin uptake has not been evaluated. We performed a secondary analysis of samples collected from a chronic GSE feeding study with pharmacokinetic end points to examine potential modulation of biomarkers of colonic integrity and endotoxin uptake. We hypothesized that a secondary analysis would indicate that chronic GSE administration increases colonic expression of intestinal tight junction proteins and reduces circulating endotoxin levels, even in the absence of an obesity-promoting stimulus. Wistar Furth rats were administered drinking water containing 0.1% GSE for 21 days. Grape seed extract significantly increased the expression of gut junction protein occludin in the proximal colon and reduced fecal levels of the neutrophil protein calprotectin, compared with control. Grape seed extract did not significantly reduce serum or fecal endotoxin levels compared with control, although the variability in serum levels was widely increased by GSE. These data suggest that the improvement of gut barrier integrity and potential modulation of endotoxemia warrant investigation as a possible mechanism by which GSE prevents metabolic syndrome and associated diseases. Further investigation of this mechanism in high-fat feeding metabolic syndrome and obesity models is therefore justified.

15 páginas, 6 figuras, 1 tabla., Members of the marine Roseobacter lineage have been characterized as ecological generalists, suggesting that there will be challenges in assigning well-delineated ecological roles and biogeochemical functions to the taxon. To address this issue, genome sequences of 32 Roseobacter isolates were analyzed for patterns in genome characteristics, gene inventory, and individual gene/ pathway distribution using three predictive frameworks: phylogenetic relatedness, lifestyle strategy and environmental origin of the isolate. For the first framework, a phylogeny containing five deeply branching clades was obtained from a concatenation of 70 conserved single-copy genes. Somewhat surprisingly, phylogenetic tree topology was not the best model for organizing genome characteristics or distribution patterns of individual genes/pathways, although it provided some predictive power. The lifestyle framework, established by grouping isolates according to evidence for heterotrophy, photoheterotrophy or autotrophy, explained more of the gene repertoire in this lineage. The environment framework had a weak predictive power for the overall genome content of each strain, but explained the distribution of several individual genes/pathways, including those related to phosphorus acquisition, chemotaxis and aromatic compound degradation. Unassembled sequences in the Global Ocean Sampling metagenomic data independently verified this global-scale geographical signal in some Roseobacter genes. The primary findings emerging from this comparative genome analysis are that members of the lineage cannot be easily collapsed into just a few ecologically differentiated clusters (that is, there are almost as many clusters as isolates); the strongest framework for predicting genome content is trophic strategy, but no single framework gives robust predictions; and previously unknown homologs to genes for H2 oxidation, proteorhodopsin-based phototrophy, xanthorhodpsin-based phototrophy, and CO2 fixation by Form IC ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) expand the possible mechanisms for energy and carbon acquisition in this remarkably versatile bacterial lineage., This project was supported by grants from the Gordon and Betty Moore Foundation and the National Science Foundation (OCE0724017 and MCB0702125)