Energy Storage Compounds Research Articles

Symbiont‐driven sulfur crystal formation in a thiotrophic symbiosis from deep‐sea hydrocarbon seeps

The siboglinid tubeworm Sclerolinum contortum symbiosis inhabits sulfidic sediments at deep-sea hydrocarbon seeps in the Gulf of Mexico. A single symbiont phylotype in the symbiont-housing organ is inferred from phylogenetic analyses of the 16S ribosomal ribonucleic acid (16S rRNA) gene and fluorescent in situ hybridization. The phylotype we studied here, and a previous study from an arctic hydrocarbon seep population, reveal identical 16S rRNA symbiont gene sequences. While sulfide is apparently the energy source for the symbionts (and ultimately the gutless host), both partners also have to cope with its toxicity. This study demonstrates abundant large sulfur crystals restricted to the trophosome area. Based on Raman microspectroscopy and energy dispersive X-ray analysis, these crystals have the same S8 sulfur configuration as the recently described small sulfur vesicles formed in the symbionts. The crystals reside adjacent to the symbionts in the trophosome. This suggests that their formation is either extra- or intracellular in symbionts. We propose that formation of these crystals provides both energy-storage compounds for the symbionts and serves the symbiosis by removing excess toxic sulfide from host tissues. This symbiont-mediated sulfide detoxification may have been crucial for the establishment of thiotrophic symbiosis and continues to remain an important function of the symbionts.

Metagenomic characterization of ‘Candidatus Defluviicoccus tetraformis strain TFO71’, a tetrad‐forming organism, predominant in an anaerobic–aerobic membrane bioreactor with deteriorated biological phosphorus removal

In an acetate-fed anaerobic-aerobic membrane bioreactor with deteriorated enhanced biological phosphorus removal (EBPR), Defluviicoccus-related tetrad-forming organisms (DTFO) were observed to predominate in the microbial community. Using metagenomics, a partial genome of the predominant DTFO, 'Candidatus Defluviicoccus tetraformis strain TFO71', was successfully constructed and characterized. Examining the genome confirmed the presence of genes related to the synthesis and degradation of glycogen and polyhydroxyalkanoate (PHA), which function as energy and carbon storage compounds. TFO71 and 'Candidatus Accumulibacter phosphatis' (CAP) UW-1 and CAP UW-2, representative polyphosphate-accumulating organisms (PAO), have PHA metabolism-related genes with high homology, but TFO71 has unique genes for PHA synthesis, gene regulation and granule management. We further discovered genes encoding DTFO polyphosphate (polyP) synthesis, suggesting that TFO71 may synthesize polyP under untested conditions. However, TFO71 may not activate these genes under EBPR conditions because the retrieved genome does not contain all inorganic phosphate transporters that are characteristic of PAOs (CAP UW-1, CAP UW-2, Microlunatus phosphovorus NM-1 and Tetrasphaera species). As a first step in characterizing EBPR-associated DTFO metabolism, this study identifies important differences between DTFO and PAO that may contribute to EBPR community competition and deterioration.

Diaryl-substituted norbornadienes with red-shifted absorption for molecular solar thermal energy storage

Red-shifting the absorption of norbornadienes (NBDs), into the visible region, enables the photo-isomerization of NBDs to quadricyclanes (QCs) to be driven by sunlight. This is necessary in order to utilize the NBD-QC system for molecular solar thermal (MOST) energy storage. Reported here is a study on five diaryl-substituted norbornadienes. The introduced aryl-groups induce a significant red-shift of the UV/vis absorption spectrum of the norbornadienes, and device experiments using a solar-simulator set-up demonstrate the potential use of these compounds for MOST energy storage.

Intracellular Glycogen Assays

Glycogen, a soluble multi-branched glucose homopolysaccharide, is composed of chains of α-1,4-linked glucose residues interconnected by α-1,6-linked branches. The classical biosynthetic pathway involves phosphoglucomutase (Pgm), glucose-1-phosphate adenylyltransferase (GlgC or GlgCD), glycogen synthase (GlgA) and branching enzyme (GlgB). Phosphoglucomutase converts glucose-6-phosphate into glucose-1-phosphate, which serves as a substrate for ADP-glucose synthesis catalyzed by GlgC or GlgCD. Then, GlgA catalyzes the transfer of glucosyl units from ADP-glucose to the elongating chain of linear α-1,4-glucan. GlgB subsequently cleaves off portions of the glucan and links it to internal glucose molecules in existing chains via α-1,6 glycosidic bonds to form the glycogen structure. Glycogen breakdown is mediated by glycogen phosphorylase (GlgP) and debranching enzyme (GlgX), which catalyze the sequential phosphorolysis of α-1,4-glucosyl linkages in the glucan chain from the non-reducing ends and debranching of the limit dextrins generated by GlgP, respectively. An increasing number of studies have revealed the involvement of glycogen metabolism in a multitude of physiological functions in some prokaryotes beyond the function of synthesizing energy storage compounds. Lactobacillus acidophilus NCFM was the first probiotic lactic acid bacterium demonstrated to possess a functional glycogen biosynthesis pathway that is involved in its growth, bile tolerance and complex carbohydrate metabolism (Goh and Klaenhammer, 2013). The following qualitative (for detection of intracellular glycogen) and quantitative (for measurement of intracellular glycogen content) intracellular glycogen assay protocols for Lactobacillus acidophilus (L. acidophilus) were modified from previous works (Govons et al., 1969; Law et al., 1995; Parrou and Francois, 1997) and should be applicable to other lactic acid bacteria as well as most microorganisms.

PHA Recovery from Biomass

The recovery of polyhydroxyalkanoates (PHAs) from biomass, that is, from bacterial cells, is one of the major obstacles in the industrial production of these polyesters. Since PHAs are naturally synthesized as intracellular storage compounds for carbon and energy and are for this deposited in the cytoplasm of the bacterial cell, PHAs are more or less tightly linked with the entire biomass, and the polyesters must be released from the cells before their isolation and purification can be conducted. This additional step, that is, the release from the cells, is a major difference from most other biotechnological processes where the product occurs outside of the cells because it is secreted into the medium in a bioreactor or because it is synthesized in vitro in an enzyme reactor in a cell free system. This additional step contributes significantly to the overall costs of production. In this review we provide an overview about the different processes that result in the release of PHA from the cells, and we evaluate these processes with regard to the suitability at large scale in the industry.

Relationship between starch and lipid accumulation induced by nutrient depletion and replenishment in the microalga Parachlorella kessleri

Photosynthetic carbon partitioning into starch and neutral lipids, as well as the influence of nutrient depletion and replenishment on growth, pigments and storage compounds, were studied in the microalga, Parachlorella kessleri. Starch was utilized as a primary carbon and energy storage compound, but nutrient depletion drove the microalgae to channel fixed carbon into lipids as secondary storage compounds. Nutrient depletion inhibited both cellular division and growth and caused degradation of chlorophyll. Starch content decreased from an initial value of 25, to around 10% of dry weight (DW), while storage lipids increased from almost 0 to about 29% of DW. After transfer of cells into replenished mineral medium, growth, reproductive processes and chlorophyll content recovered within 2 days, while the content of both starch and lipids decreased markedly to 3 or less % of DW; this suggested that they were being used as a source of energy and carbon.

Saccharification of Cellulose by Recombinant Rhodococcus opacus PD630 Strains

The noncellulolytic actinomycete Rhodococcus opacus strain PD630 is the model oleaginous prokaryote with regard to the accumulation and biosynthesis of lipids, which serve as carbon and energy storage compounds and can account for as much as 87% of the dry mass of the cell in this strain. In order to establish cellulose degradation in R. opacus PD630, we engineered strains that episomally expressed six different cellulase genes from Cellulomonas fimi ATCC 484 (cenABC, cex, cbhA) and Thermobifida fusca DSM43792 (cel6A), thereby enabling R. opacus PD630 to degrade cellulosic substrates to cellobiose. Of all the enzymes tested, five exhibited a cellulase activity toward carboxymethyl cellulose (CMC) and/or microcrystalline cellulose (MCC) as high as 0.313 ± 0.01 U · ml(-1), but recombinant strains also hydrolyzed cotton, birch cellulose, copy paper, and wheat straw. Cocultivations of recombinant strains expressing different cellulase genes with MCC as the substrate were carried out to identify an appropriate set of cellulases for efficient hydrolysis of cellulose by R. opacus. Based on these experiments, the multicellulase gene expression plasmid pCellulose was constructed, which enabled R. opacus PD630 to hydrolyze as much as 9.3% ± 0.6% (wt/vol) of the cellulose provided. For the direct production of lipids from birch cellulose, a two-step cocultivation experiment was carried out. In the first step, 20% (wt/vol) of the substrate was hydrolyzed by recombinant strains expressing the whole set of cellulase genes. The second step was performed by a recombinant cellobiose-utilizing strain of R. opacus PD630, which accumulated 15.1% (wt/wt) fatty acids from the cellobiose formed in the first step.

Cover Picture: Redox Cofactor from Biological Energy Transduction as Molecularly Tunable Energy-Storage Compound (Angew. Chem. Int. Ed. 32/2013)

Cover Picture: Redox Cofactor from Biological Energy Transduction as Molecularly Tunable Energy-Storage Compound (Angew. Chem. Int. Ed. 32/2013)

Redox Cofactor from Biological Energy Transduction as Molecularly Tunable Energy-Storage Compound

Flavin-Batterie: Flavine wurden als molekular abstimmbares Kathodenmaterial verwendet, das reversibel mit zwei Lithiumionen und zwei Elektronen pro Formeleinheit reagiert. Ex-situ-Untersuchungen und DFT-Rechnungen zeigen, dass an der Redoxreaktion zwei aufeinanderfolgende Einelektronen-Transferreaktionen an den Stickstoffatomen der Diazabutadien-Einheit beteiligt sind (siehe Bild). As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Evidence for lytic transglycosylase and β-N-acetylglucosaminidase activities located at the polyhydroxyalkanoates (PHAs) granules of Thermus thermophilus HB8

The thermophilic bacterium Thermus thermophilus HB8 accumulates polyhydroxyalkanoates (PHAs) as intracellular granules used by cells as carbon and energy storage compounds. PHAs granules were isolated from cells grown in sodium gluconate (1.5 % w/v) as carbon source. Lytic activities are strongly associated and act to the PHAs granules proved with various methods. Specialized lytic trasglycosylases (LTGs) are muramidases capable of locally degrading the peptidoglycan (PG) meshwork of Gram negative bacteria. These enzymes cleave the β-1,4-glycosidic linkages between the N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc) residues of PG. Lysozyme-like activity/-ies were detected using lysoplate assay. Chitinolytic activity/-ies, were detected as N-acetyl glucosaminidases (NAG) (E.C.3.2.1.5.52) hydrolyzing the synthetic substrate p-nitrophenyl-N-acetyl-β-D-glucosaminide (pNP-GlcNAc) releasing pNP and GlcNAc. Using zymogram analysis two abundant LTGs were revealed hydrolyzing cell wall of Micrococcus lysodeikticus or purified PG incorporated as natural substrates, in SDS-PAGE and then renaturation. These proteins corresponded in a SDS-PAGE and Coomassie-stained gel in molecular mass of 110 and 32 kDa respectively, were analyzed by MALDI-MS (Matrix-assisted laser desorption/ionization-Mass Spectrometry). The 110 kDa protein was identified as an S-layer domain-containing protein [gi|336233805], while the 32 kDa similar to the hypothetical protein VDG1235_2196 (gi/254443957). Overall, the localization of PG hydrolases in PHAs granules appears to be involved to their biogenesis from membranes, and probably promoting septal PG splitting and daughter cell separation.

Cupriavidus necator를 이용한 Poly(3-hydroxybutyrate) 생산에 이산화탄소의 농도가 미치는 영향

Abstract : Polyhydroxyalkanoates (PHAs) are synthesized by numerous bacteria as carbon and energy storage compounds and are raw materials for biocompatible plastics. In this paper, the effect of CO 2 concentrations on the growth of C. necator and the accumulation of Poly(3-hydroxybutyrate) (P(3HB)) are investigated by increasing the CO 2 concentration in the substrate gas mixture. During 6 d cultivation in a nitrogen-present mineral medium, the CO 2 concentration did not affect the growth of the cells, while the Poly(3- hydroxybutyrate) (P(3HB)) content decreased with increasing CO 2 concentrations from 1% to 20%. During 4 d cultivation in the nitrogen-limited medium, the P(3HB) accumulation was the greatest at 3% CO 2 ; however, the total amount of accumulated P(3HB) was the greatest at 1% CO 2 , which decreased with increasing CO 2 concentrations. The results indicate that the gas mixture with 1% CO 2 is the most effective in both growing the cells and accumulating P(3HB) under our experimental conditions.

L05.03 - The Molecular Consequences of Inhibiting Fatty Acid Synthase in Cancer Cells

Fatty acids are the major constituent of membrane lipids and are used for energy storage and signaling compounds. Fatty acids can be obtained from the diet or synthesized de novo in a series of reactions catalyszed by the multifunctional enzyme fatty acid synthase. Fatty acid synthase overexpression has been observed in a variety of human cancer types (breast, prostate, colon, and ovarian tumors) and has been associated with tumor progression, aggressiveness and metastasis. In addition, higher levels of palmitate, the product of the fatty acid synthase (FAS) enzyme, have been detected in more advanced cancers of the prostate.

Mate guarding in relation to seasonal changes in the energy reserves of two freshwater amphipods (Gammarus fossarum and G. pulex)

Summary1. We assessed sex‐specific seasonal changes in major energy storage compounds (triglycerides, glycogen) in Gammarus fossarum and Gammarus pulex collected from the field, with respect to their reproductive activity.2. The dynamics of stored energy followed a seasonal pattern in both species and sexes. Moreover, over a 4‐year period, these changes were independent of the year in which they were investigated. Stored energy reached a peak in late winter, but was depleted in late summer and early autumn, coinciding with the reproductive periods.3. Triglyceride (annual mean ± SD) accounted for 79.7 ± 11.9% of the total stored energy and was responsible for the seasonal pattern. In contrast, glycogen contributed a lesser percentage (20.3 ± 11.9%). Over the study period, the amount of stored energy ranged between 0.39 and 4.08 kJ g−1 dry mass (triglyceride: 0.19–3.69 kJ g−1 dry mass; glycogen: 0.14–0.80 kJ g−1 dry mass).4. In both species, the energy reserves of males were drastically depleted shortly before the cessation of precopulatory mate guarding in the field, thus offering a bioenergetic explanation for the reproductive period in these two widespread species.

Neutral lipid accumulation at elevated temperature in conditional mutants of two microalgae species

Triacylglycerols, an energy storage compound in microalgae, are known to be accumulated after nitrogen starvation of microalgae cells. Microalgae could be of importance for future biodiesel production due to their fast growth rate and high oil content. In collections of temperature sensitive mutants of Chlamydomonas reinhardtii and Chlorella vulgaris, nine out of fourty-one mutants in C.reinhardtii and eleven out of fifty-three mutants in C. vulgaris contained increased amounts of neutral lipids, predominantly as triacylglycerols. Upon temperature induced cell-cycle arrest, these mutants showed enlarged cellular volume compared with the wild type. The C.reinhardtii mutants were analyzed further and one type of mutants displayed a shift in lipid composition from polar membrane lipids to neutral lipids after a temperature up-shift, while the second type of mutants accumulated more total lipid per cell, predominantly as neutral lipids as compared with the wild type. Three C.reinhardtii mutants were analyzed further and found to be arrested after DNA synthesis but prior to cell division in the cell cycle. These mutants will be useful in order to further understand neutral lipid accumulation in microalgae and suggest possibilities for biodiesel production by specific induction of lipid accumulation in miroalgal cultures by cell-cycle inhibition.

Proteomic analysis of Clostridium thermocellum core metabolism: relative protein expression profiles and growth phase-dependent changes in protein expression

BackgroundClostridium thermocellum produces H2 and ethanol, as well as CO2, acetate, formate, and lactate, directly from cellulosic biomass. It is therefore an attractive model for biofuel production via consolidated bioprocessing. Optimization of end-product yields and titres is crucial for making biofuel production economically feasible. Relative protein expression profiles may provide targets for metabolic engineering, while understanding changes in protein expression and metabolism in response to carbon limitation, pH, and growth phase may aid in reactor optimization. We performed shotgun 2D-HPLC-MS/MS on closed-batch cellobiose-grown exponential phase C. thermocellum cell-free extracts to determine relative protein expression profiles of core metabolic proteins involved carbohydrate utilization, energy conservation, and end-product synthesis. iTRAQ (isobaric tag for relative and absolute quantitation) based protein quantitation was used to determine changes in core metabolic proteins in response to growth phase.ResultsRelative abundance profiles revealed differential levels of putative enzymes capable of catalyzing parallel pathways. The majority of proteins involved in pyruvate catabolism and end-product synthesis were detected with high abundance, with the exception of aldehyde dehydrogenase, ferredoxin-dependent Ech-type [NiFe]-hydrogenase, and RNF-type NADH:ferredoxin oxidoreductase. Using 4-plex 2D-HPLC-MS/MS, 24% of the 144 core metabolism proteins detected demonstrated moderate changes in expression during transition from exponential to stationary phase. Notably, proteins involved in pyruvate synthesis decreased in stationary phase, whereas proteins involved in glycogen metabolism, pyruvate catabolism, and end-product synthesis increased in stationary phase. Several proteins that may directly dictate end-product synthesis patterns, including pyruvate:ferredoxin oxidoreductases, alcohol dehydrogenases, and a putative bifurcating hydrogenase, demonstrated differential expression during transition from exponential to stationary phase.ConclusionsRelative expression profiles demonstrate which proteins are likely utilized in carbohydrate utilization and end-product synthesis and suggest that H2 synthesis occurs via bifurcating hydrogenases while ethanol synthesis is predominantly catalyzed by a bifunctional aldehyde/alcohol dehydrogenase. Differences in expression profiles of core metabolic proteins in response to growth phase may dictate carbon and electron flux towards energy storage compounds and end-products. Combined knowledge of relative protein expression levels and their changes in response to physiological conditions may aid in targeted metabolic engineering strategies and optimization of fermentation conditions for improvement of biofuels production.

Polyhydroxyalkanoates (PHAs) Production Through Conversion of Glycerol by Selected Strains of Pseudomonas Mediterranea and Pseudomonas Corrugata

Polyhydroxyalkanoates (PHAs) are polyesters synthesized by numerous bacteria as an intracellular carbon and energy storage compounds in the cytoplasm of cells. To cut down the cost of production and optimize the PHA/dried cell weight different concentrations (1, 2 and 5 %) of refined glycerol and a crude glycerol from biodiesel process, were used as carbon source in a batch fermentation process. Pseudomonas mediterranea 9.1 as well as Pseudomonas corrugata 388 and A1 reference strains, grew and synthesized a medium-chain-length poly(3-hy-droxyalkanoates) elastomer both on crude and refined glycerol carbon sources. The mcl-PHA produced by P. mediterranea 9.1 grown on refined glycerol was apparently different as a result of a different metabolic pathway. Gas chromatography PHA’s Different monomeric units of side chains, which ranged from C12 to C19 in length in mcl-PHA(CG) and from C5 to C16 in mcl-PHA(RG) were obtained.

Differences in Substrate Specificities of Five Bacterial Wax Ester Synthases

Wax esters are produced in certain bacteria as a potential carbon and energy storage compound. The final enzyme in the biosynthetic pathway responsible for wax ester production is the bifunctional wax ester synthase/acyl-coenzyme A (acyl-CoA):diacylglycerol acyltransferase (WS/DGAT), which utilizes a range of fatty alcohols and fatty acyl-CoAs to synthesize the corresponding wax ester. We report here the isolation and substrate range characterization for five WS/DGAT enzymes from four different bacteria: Marinobacter aquaeolei VT8, Acinetobacter baylyi, Rhodococcus jostii RHA1, and Psychrobacter cryohalolentis K5. The results from kinetic studies of isolated enzymes reveal a differential activity based on the order of substrate addition and reveal subtle differences between the substrate selectivity of the different enzymes. These in vitro results are compared to the wax ester and triacylglyceride product profiles obtained from each organism grown under neutral lipid accumulating conditions, providing potential insights into the role that the WS/DGAT enzyme plays in determining the final wax ester products that are produced under conditions of nutrient stress in each of these bacteria. Further, the analysis revealed that one enzyme in particular from M. aquaeolei VT8 showed the greatest potential for future study based on rapid purification and significantly higher activity than was found for the other isolated WS/DGAT enzymes. The results provide a framework to test prospective differences between these enzymes for potential biotechnological applications such as high-value petrochemicals and biofuel production.

Hydroxybutyrate prevents protein aggregation in the halotolerant bacterium Pseudomonas sp. CT13 under abiotic stress

Polyhydroxybutyrate (PHB), a typical carbon and energy storage compound, is widely found in Bacteria and Archae domains. This polymer is produced in response to conditions of physiological stress. PHB is composed of repeating units of β-hydroxybutyrate (R-3HB). It has been previously shown that R-3HB functions as an osmolyte in extremophile strains. In this study, Pseudomonas sp. CT13, a halotolerant bacterium, and its PHB synthase-minus mutant (phaC) were used to analyze the chaperone role of R-3HB. The production of this compound was found to be essential to salt stress resistance and positively correlated with salt concentration, suggesting that PHB monomer acts as a compatible solute in Pseudomonas sp. CT13. R-3HB accumulation was also associated with the prevention of protein aggregation under combined salt and thermal stresses in Pseudomonas sp. CT13. Physiological concentrations of R-3HB efficiently reduced citrate synthase (CS) aggregation and stabilized the enzymatic activities of CS during thermal stress. Docking analysis of the CS/R-3HB interaction predicted the stability of this complex under physiological concentrations of R-3HB. Thus, in vivo, in vitro and in silico analyses suggest that R-3HB can act as a chemical chaperone.

Formation of New High Density Glycogen-Microtubule Structures Is Induced by Cardiac Steroids

Cardiac steroids (CS), an important class of naturally occurring compounds, are synthesized in plants and animals. The only established receptor for CS is the ubiquitous Na(+),K(+)-ATPase, a major plasma membrane transporter. The binding of CS to Na(+),K(+)-ATPase causes the inhibition of Na(+) and K(+) transport and elicits cell-specific activation of several intracellular signaling mechanisms. It is well documented that the interaction of CS with Na(+),K(+)-ATPase is responsible for numerous changes in basic cellular physiological properties, such as electrical plasma membrane potential, cell volume, intracellular [Ca(2+)] and pH, endocytosed membrane traffic, and the transport of other solutes. In the present study we show that CS induces the formation of dark structures adjacent to the nucleus in human NT2 and ACHN cells. These structures, which are not surrounded by membranes, are clusters of glycogen and a distorted microtubule network. Formation of these clusters results from a relocation of glycogen and microtubules in the cells, two processes that are independent of one another. The molecular mechanisms underlying the formation of the clusters are mediated by the Na(+),K(+)-ATPase, ERK1/2 signaling pathway, and an additional unknown factor. Similar glycogen clusters are induced by hypoxia, suggesting that the CS-induced structural change, described in this study, may be part of a new type of cellular stress response.

Mass spectrometry based lipidomics: an overview of technological platforms.

One decade after the genomic and the proteomic life science revolution, new ‘omics’ fields are emerging. The metabolome encompasses the entity of small molecules—Most often end products of a catalytic process regulated by genes and proteins—with the lipidome being its fat soluble subdivision. Within recent years, lipids are more and more regarded not only as energy storage compounds but also as interactive players in various cellular regulation cycles and thus attain rising interest in the bio-medical community. The field of lipidomics is, on one hand, fuelled by analytical technology advances, particularly mass spectrometry and chromatography, but on the other hand new biological questions also drive analytical technology developments. Compared to fairly standardized genomic or proteomic high-throughput protocols, the high degree of molecular heterogeneity adds a special analytical challenge to lipidomic analysis. In this review, we will take a closer look at various mass spectrometric platforms for lipidomic analysis. We will focus on the advantages and limitations of various experimental setups like ‘shotgun lipidomics’, liquid chromatography—Mass spectrometry (LC-MS) and matrix assisted laser desorption ionization-time of flight (MALDI-TOF) based approaches. We will also examine available software packages for data analysis, which nowadays is in fact the rate limiting step for most ‘omics’ workflows.