The regulation of propionate oxidation in Prototheca zopfii.
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ABSTRACT:
SUBMITTER: Lloyd D
PROVIDER: S-EPMC1270631 | biostudies-other | 1967 Aug
REPOSITORIES: biostudies-other
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Project description:1. The tricarboxylic acid and glyoxylate cycles are of major importance in the assimilation of acetate and propionate by Prototheca zopfii. The pattern of assimilation of [2-(14)C]acetate and [2-(14)C]propionate by whole cells growing with their respective substrates is similar except that, with propionate, beta-hydroxypropionate is the first labelled intermediate detected. 2. Carbon dioxide fixation is of little quantitative importance for the growth of this organism with propionate. 3. The yield of cells obtained/mole of acetate is similar to that obtained/mole of propionate and about half that obtained/mole of n-butyrate, these substrates acting as sole sources of carbon and energy.
| S-EPMC1264558 | biostudies-other
Project description:1. The rate and stability to aging of the metabolism of propionate by sheep-liver slices and sucrose homogenates were examined. Aging for up to 20min. at 37 degrees in the absence of added substrate had little effect with slices, whole homogenates or homogenates without the nuclear fraction. 2. Metabolism of propionate by sucrose homogenates was confined to the mitochondrial fraction, but the mitochondrial supernatant (microsomes plus cell sap) stimulated propionate removal. 3. The rate of propionate metabolism by liver slices was higher in a high potassium phosphate-bicarbonate medium [0.88(+/-s.e.m. 0.16)mumole/mg. of N/hr.] than in Krebs-Ringer bicarbonate medium [0.44(+/-s.e.m. 0.13)mumole/mg. of N/hr.]. 4. Metabolism of propionate by sucrose homogenates freed from nuclei was dependent on the presence of oxygen, carbon dioxide and ATP. Propionate removal was stimulated 250% by Mg(2+) ions and 670% by cytochrome c. 5. In the complete medium 2.39(+/-s.e.m. 0.15)mumoles of propionate were consumed/mg. of N/hr. 6. The ratio of oxygen consumption to propionate utilization was sufficient to account for the complete oxidation of half the propionate consumed. 7. The only products detected under these conditions were succinate, fumarate and malate. Propionate had no effect on the production of lactate from endogenous sources and did not itself give rise to lactate. 8. Methylmalonate did not accumulate when propionate was metabolized and was not oxidized. It was detected as an intermediate in the conversion of propionyl-CoA into succinate. The rate of this reaction sequence was adequate to account for the rate of propionate metabolism by sucrose homogenates or slices, provided that the rate of formation of propionyl-CoA was not limiting. 9. The methylmalonate pathway was predominantly a mitochondrial function. 10. The metabolism of propionate appeared to be dependent on active oxidative phosphorylation.
| S-EPMC1214338 | biostudies-other
Project description:Anaerobic propionic acid degradation relies on interspecies electron transfer (IET) between propionate oxidisers and electron acceptor microorganisms, via either molecular hydrogen, formate or direct transfers. We evaluated the possibility of stimulating direct IET, hence enhancing propionate oxidation, by increasing availability of proton carriers to decrease solution resistance and reduce pH gradients. Phosphate was used as a proton carrying anion, and chloride as control ion together with potassium as counter ion. Propionic acid consumption in anaerobic granules was assessed in a square factorial design with ratios (1:0, 2:1, 1:1, 1:2 and 0:1) of total phosphate (TP) to Cl(-), at 1X, 10X, and 30X native conductivity (1.5 mS.cm(-1)). Maximum specific uptake rate, half saturation, and time delay were estimated using model-based analysis. Community profiles were analysed by fluorescent in situ hybridisation and 16S rRNA gene pyrosequencing. The strongest performance was at balanced (1:1) ratios at 10X conductivity where presumptive propionate oxidisers namely Syntrophobacter and Candidatus Cloacamonas were more abundant. There was a shift from Methanobacteriales at high phosphate, to Methanosaeta at low TP:Cl ratios and low conductivity. A lack of response to TP, and low percentage of presumptive electroactive organisms suggested that DIET was not favoured under the current experimental conditions.
| S-EPMC4680937 | biostudies-literature
Project description:Propionate is a key intermediate in anaerobic digestion processes and often accumulates in association with perturbations, such as elevated levels of ammonia. Under such conditions, syntrophic ammonia-tolerant microorganisms play a key role in propionate degradation. Despite their importance, little is known about these syntrophic microorganisms and their cross-species interactions. Here, we present metagenomes and metatranscriptomic data for novel thermophilic and ammonia-tolerant syntrophic bacteria and the partner methanogens enriched in propionate-fed reactors. A metagenome for a novel bacterium for which we propose the provisional name 'Candidatus Thermosyntrophopropionicum ammoniitolerans' was recovered, together with mapping of its highly expressed methylmalonyl-CoA pathway for syntrophic propionate degradation. Acetate was degraded by a novel thermophilic syntrophic acetate-oxidising candidate bacterium. Electron removal associated with syntrophic propionate and acetate oxidation was mediated by the hydrogen/formate-utilising methanogens Methanoculleus sp. and Methanothermobacter sp., with the latter observed to be critical for efficient propionate degradation. Similar dependence on Methanothermobacter was not seen for acetate degradation. Expression-based analyses indicated use of both H2 and formate for electron transfer, including cross-species reciprocation with sulphuric compounds and microbial nanotube-mediated interspecies interactions. Batch cultivation demonstrated degradation rates of up to 0.16 g propionate L-1 day-1 at hydrogen partial pressure 4-30 Pa and available energy was around -20 mol-1 propionate. These observations outline the multiple syntrophic interactions required for propionate oxidation and represent a first step in increasing knowledge of acid accumulation in high-ammonia biogas production systems.
| S-EPMC10579422 | biostudies-literature
Project description:Propionate is an important intermediate of the degradation of organic matter in many anoxic environments. In methanogenic environments, due to thermodynamic constraints, the oxidation of propionate requires syntrophic cooperation of propionate-fermenting proton-reducing bacteria and H(2)-consuming methanogens. We have identified here microorganisms that were active in syntrophic propionate oxidation in anoxic paddy soil by rRNA-based stable-isotope probing (SIP). After 7 weeks of incubation with [(13)C]propionate (<10 mM) and the oxidation of approximately 30 micromol of (13)C-labeled substrate per g dry weight of soil, we found that archaeal nucleic acids were (13)C labeled to a larger extent than those of the bacterial partners. Nevertheless, both terminal restriction fragment length polymorphism and cloning analyses revealed Syntrophobacter spp., Smithella spp., and the novel Pelotomaculum spp. to predominate in "heavy" (13)C-labeled bacterial rRNA, clearly showing that these were active in situ in syntrophic propionate oxidation. Among the Archaea, mostly Methanobacterium and Methanosarcina spp. and also members of the yet-uncultured "rice cluster I" lineage had incorporated substantial amounts of (13)C label, suggesting that these methanogens were directly involved in syntrophic associations and/or thriving on the [(13)C]acetate released by the syntrophs. With this first application of SIP in an anoxic soil environment, we were able to clearly demonstrate that even guilds of microorganisms growing under thermodynamic constraints, as well as phylogenetically diverse syntrophic associations, can be identified by using SIP. This approach holds great promise for determining the structure and function relationships of further syntrophic or other nutritional associations in natural environments and for defining metabolic functions of yet-uncultivated microorganisms.
| S-EPMC522077 | biostudies-literature
Project description:Short-chain fatty acids (SCFAs), produced from fermentation of dietary fibre by the gut microbiota, have been suggested to modulate energy metabolism. Previous work using rodent models has demonstrated that oral supplementation of the SCFA propionate raises resting energy expenditure (REE) by promoting lipid oxidation. The objective of the present study was to investigate the effects of oral sodium propionate on REE and substrate metabolism in humans. Eighteen healthy volunteers (9 women and 9 men; age 25?±?1 years; body mass index 24.1?±?1.2 kg/m2 ) completed 2 study visits following an overnight fast. Tablets containing a total of 6845?mg sodium propionate or 4164?mg sodium chloride were provided over the 180-minute study period in random order. REE and substrate oxidation were assessed by indirect calorimetry. Oral sodium propionate administration increased REE (0.045?±?0.020?kcal/min; P?=?.036); this was accompanied by elevated rates of whole-body lipid oxidation (0.012?±?0.006?g/min; P?=?.048) and was independent of changes in glucose and insulin concentrations. Future studies are warranted to determine whether the acute effects of oral sodium propionate on REE translate into positive improvements in long-term energy balance in humans.
| S-EPMC5873405 | biostudies-literature
Project description:AimsAtherosclerotic cardiovascular disease (ACVD) is a major cause of mortality and morbidity worldwide, and increased low-density lipoproteins (LDLs) play a critical role in development and progression of atherosclerosis. Here, we examined for the first time gut immunomodulatory effects of the microbiota-derived metabolite propionic acid (PA) on intestinal cholesterol metabolism.Methods and resultsUsing both human and animal model studies, we demonstrate that treatment with PA reduces blood total and LDL cholesterol levels. In apolipoprotein E-/- (Apoe-/-) mice fed a high-fat diet (HFD), PA reduced intestinal cholesterol absorption and aortic atherosclerotic lesion area. Further, PA increased regulatory T-cell numbers and interleukin (IL)-10 levels in the intestinal microenvironment, which in turn suppressed the expression of Niemann-Pick C1-like 1 (Npc1l1), a major intestinal cholesterol transporter. Blockade of IL-10 receptor signalling attenuated the PA-related reduction in total and LDL cholesterol and augmented atherosclerotic lesion severity in the HFD-fed Apoe-/- mice. To translate these preclinical findings to humans, we conducted a randomized, double-blinded, placebo-controlled human study (clinical trial no. NCT03590496). Oral supplementation with 500 mg of PA twice daily over the course of 8 weeks significantly reduced LDL [-15.9 mg/dL (-8.1%) vs. -1.6 mg/dL (-0.5%), P = 0.016], total [-19.6 mg/dL (-7.3%) vs. -5.3 mg/dL (-1.7%), P = 0.014] and non-high-density lipoprotein cholesterol levels [PA vs. placebo: -18.9 mg/dL (-9.1%) vs. -0.6 mg/dL (-0.5%), P = 0.002] in subjects with elevated baseline LDL cholesterol levels.ConclusionOur findings reveal a novel immune-mediated pathway linking the gut microbiota-derived metabolite PA with intestinal Npc1l1 expression and cholesterol homeostasis. The results highlight the gut immune system as a potential therapeutic target to control dyslipidaemia that may introduce a new avenue for prevention of ACVDs.
| S-EPMC9097250 | biostudies-literature
Project description:The metabolism of propionate was examined in wild-type Escherichia coli and cells lacking citrate synthase by high-resolution 13C n.m.r. Spectra of cell extracts from wild-type E. coli show that glutamate becomes highly enriched in 13C when 13C-enriched propionate is the sole carbon source. No glutamate labelling was detected when the tricarboxylic acid cycle was blocked either by deletion of citrate synthase or by inhibition of succinate dehydrogenase by malonate. The 13C fractional enrichment in glutamate C-2, C-3 and C-4 in wild-type cells was quantitatively and qualitatively different when [2-13C]propionate as opposed to [3-13C]propionate was supplied. Approximately equal labelling occurred in the C-2, C-3 and C-4 positions of glutamate when [3-13C]propionate was available, and multiplets due to carbon-carbon spin-spin coupling were observed. However, in cells supplied with [2-13C]propionate, very little 13C appeared in the glutamate C-4 position, and the remaining glutamate resonances all appeared as singlets. The unequal and non-identical labelling of glutamate in cells supplied with [2-13C]- as opposed to [3-13C]propionate is consistent with the utilization of propionate by E. coli via two pathways, oxidation of propionate to pyruvate and carboxylation of propionate to succinate. These intermediates are further metabolized to glutamate by the action of the tricarboxylic acid cycle. The existence of an organized tricarboxylic acid cycle is discussed as a consequence of the ability to block utilization of propionate in tricarboxylic acid-cycle-defective E. coli.
| S-EPMC1132458 | biostudies-other
Project description:Propionate is one of the major intermediary products in the anaerobic decomposition of organic matter in wetlands and paddy fields. Under methanogenic conditions, propionate is decomposed through syntrophic interaction between proton-reducing and propionate-oxidizing bacteria and H(2)-consuming methanogens. Temperature is an important environmental regulator; yet its effect on syntrophic propionate oxidation has been poorly understood. In the present study, we investigated the syntrophic oxidation of propionate in a rice field soil at 15°C and 30°C. [U-(13)C]propionate (99 atom%) was applied to anoxic soil slurries, and the bacteria and archaea assimilating (13)C were traced by DNA-based stable isotope probing. Syntrophobacter spp., Pelotomaculum spp., and Smithella spp. were found significantly incorporating (13)C into their nucleic acids after [(13)C]propionate incubation at 30°C. The activity of Smithella spp. increased in the later stage, and concurrently that of Syntrophomonas spp. increased. Aceticlastic Methanosaetaceae and hydrogenotrophic Methanomicrobiales and Methanocellales acted as methanogenic partners at 30°C. Syntrophic oxidation of propionate also occurred actively at 15°C. Syntrophobacter spp. were significantly labeled with (13)C, whereas Pelotomaculum spp. were less active at this temperature. In addition, Methanomicrobiales, Methanocellales, and Methanosarcinaceae dominated the methanogenic community, while Methanosaetaceae decreased. Collectively, temperature markedly influenced the activity and community structure of syntrophic guilds degrading propionate in the rice field soil. Interestingly, Geobacter spp. and some other anaerobic organisms like Rhodocyclaceae, Acidobacteria, Actinobacteria, and Thermomicrobia probably also assimilated propionate-derived (13)C. The mechanisms for the involvement of these organisms remain unclear.
| S-EPMC3416378 | biostudies-literature
Project description:Carboxylated multiwalled carbon nanotubes (MWCNTs-COOH) have become a growing concern in terms of their fate and toxicity in aqueous environments. Methane (CH4) is a major product of organic matter degradation in waterlogged environments. In this study, we determined the effect of MWCNTs-COOH on the production of CH4 from propionate oxidation in paddy soil enrichments. The results showed that the methanogenesis from propionate degradation was accelerated in the presence of MWCNTs-COOH. In addition, the rates of CH4 production and propionate degradation increased with increasing concentrations of MWCNTs-COOH. Scanning electron microscopy (SEM) observations showed that the cells were intact and maintained their structure in the presence of MWCNTs-COOH. In addition, SEM and fluorescence in situ hybridization (FISH) images revealed that the cells were in direct contact with the MWCNTs and formed cell-MWCNTs aggregates that contained both bacteria and archaea. On the other hand, nontoxic magnetite nanoparticles (Fe3O4) had similar effects on the CH4 production and cell integrity as the MWCNTs-COOH. Compared with no nanomaterial addition, the relative abundances of Geobacter and Methanosarcina species increased in the presence of MWCNTs-COOH. This study suggests that MWCNTs-COOH exerted positive rather than cytotoxic effects on the syntrophic oxidation of propionate in paddy soil enrichments and affected the bacterial and archaeal community structure at the test concentrations. These findings provide novel insight into the consequences of nanomaterial release into anoxic natural environments.
| S-EPMC5768162 | biostudies-literature