The Role and Regulation of Energy Reserve Polymers in Micro-organisms

Dawes, E. A.; Senior, Peter J.

doi:10.1016/s0065-2911(08)60088-0

Cited by 825 publications

(501 citation statements)

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“…These could be condensed and then converted to glucose-l-phosphate. Assuming glycogen synthesis occurs in the same manner as in other bacteria, an adenosine diphosphoryl glucose pyrophosphorylase (no EC number) and an a-1,4-glucan synthetase (no EC number) would be involved (10). By using two independent assay systems, we have detected an a-1,4-glucan synthetase in extracts of nitrogen-limited T-11.…”

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confidence: 79%

“…At no point in this scheme, from the time formal-ADP dehyde is fixed into a hexose phosphate until it is incorporated into glycogen, would there have to be an unphosphorylated compound. If the glycogen were degraded by a phosphorylase similar to those currently known to exist in other bacteria, glucose-l-phosphate would be the product (10). Again, there would be no unphosphorylated intermediates.…”

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confidence: 97%

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Methylobacillus: a New Genus of Obligately Methylotrophic Bacteria

Yordy

Weaver

1977

International Journal of Systematic Bacteriology

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confidence: 79%

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confidence: 97%

Methylobacillus: a New Genus of Obligately Methylotrophic Bacteria

Yordy

Weaver

1977

International Journal of Systematic Bacteriology

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“…PHAs are a class of polyesters of various hydroxycarboxylic acids, which are produced and accumulated by a large number of bacteria under unbalanced growth conditions as intracellular hydrophobic inclusions of carbon and energy storage compounds in the cytoplasm to levels as high as 90-97% of the cell dry weight (4)(5)(6)(7)(8)(9) or as an electron sink mechanism for redundant reducing power under the condition of limiting nutritional elements such as N, P, S, O or Mg in the presence of excess carbon source (10)(11)(12)(13). They are synthesized as byproducts not the major ones when there is no sufficient nutrient to promote their growth and do not play an essential role in development of the producing organisms, but convey survival in the biological community and environment, therefore, microbial PHAs are secondary metabolites (14).…”

Section: Introductionmentioning

confidence: 99%

Bacterial polyhydroxyalkanoates-eco-friendly next generation plastic: Production, biocompatibility, biodegradation, physical properties and applications

Muhammadi

Shabina

Afzal

et al. 2015

Green Chemistry Letters and Reviews

274

139

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Polyhydroxyalkanoates (PHAs) are intracellular aliphatic polyesters synthesized as energy reserves, in the form of water-insoluble, nano-sized discrete and optically dense granules in cytoplasm by a diverse bacteria and some archae under conditions of limiting nutrients in the presence of excess carbon source. Bacteria synthesize different PHAs from coenzyme A thioesters of respective hydroxyalkanoic acid, and degrade intracellularly for reuse and extracellularly in natural environments by other microorganisms. In vivo, PHAs exist as amorphous mobile liquid and water-insoluble inclusions but in vitro, exhibit material and mechanical properties, ranging from stiff and brittle crystalline to elastomeric and molding, similar to petrochemical thermoplastics. Further, they are hydrophobic, isotactic, biocompatible and exhibit piezoelectric properties. But as commodity plastics their applications are limited by high production cost, low yield, in vivo degradation, complexity of technology and difficulty of extraction. Therefore, to replace the conventional plastic with PHAs, it is prerequisite to standardize the PHA production systems.

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“…Poly-p-hydroxybutyrate (PHB) is a biopolymer found exclusively in procaryotes, in which it acts as a reserve of carbon and energy (10). This polymer has also been identified in some species of cyanobacteria (1,5,6,7,15,19,20).…”

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confidence: 99%

“…The synthesis of PHB is a reductive process regulated primarily by 3-ketothiolase (9). This enzyme is powerfully inhibited by high concentrations of free coenzyme A (CoA) (10,13), but at high (saturating) concentrations of acetyl-CoA, the inhibitory effect of CoA is overcome (9). In microorganisms such as Alcaligenes eutrophus and Azotobacter vinelandii, known to produce large amounts of PHB under certain unbalanced growth conditions (10), biosynthesis of the polymer during balanced growth is strongly restricted because the concentration of free CoA is generally high whereas that of acetyl-CoA is low (4,9).…”

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confidence: 99%

Occurrence of poly-beta-hydroxybutyrate in Spirulina species

et al. 1990

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Poly-p-hydroxybutyrate (PHB) is a biopolymer found exclusively in procaryotes, in which it acts as a reserve of carbon and energy (10). This polymer has also been identified in some species of cyanobacteria (1,5,6,7,15,19,20). Little information is available concerning the lipid reserves of these microorganisms, but only a minor role is generally attributed to PHB (21). In any case, intracellular accumulation of the polymer seems to be related to the ability of cyanobacteria to grow mixotrophically in the presence of acetate (1, 7). One exception to this picture is constituted by Spirulina platensis, in which, according to Campbell et al. (5), PHB accumulation reached a maximum (about 6% of cell dry weight) during exponential growth under photoautotrophic conditions and was unaffected by acetate supplementation. This result is of particular importance mainly for its practical implications: the presence of PHB in bacterial cells reduces the biological value of the microbial biomass that is to be used, as proposed for Spirulina spp., as a source of single-cell protein. The occurrence of PHB in Spirulina spp. was thus verified by assaying several strains grown under both photoautotrophic and mixotrophic conditions. S. platensis LB1475/4 was obtained from the Cambridge Culture Collection; all other strains used belong to our culture collection. The strains were grown on the standard mineral medium (2) at 30°C in batch cultures continuously illuminated with cool-white fluorescent lamps. Pure CO2 was bubbled into the cultures to maintain the pH in the range of 9.3 to 9.6. Sodium acetate or sodium pyruvate was added, when required, up to a final concentration of 1 g liter-'.Axenic cultures were grown in 1-liter Erlenmeyer flasks containing 400 ml of culture medium under a light intensity of 12 puE m-2 s-1 (photosynthetic active radiation) at the surface of the flasks. Axenicity was controlled as suggested by Rippka et al. (18). The cells were harvested by centrifugation after 10 days of growth, washed twice in 1.5% (wt/vol) NaCl solution, and freeze-dried. Nonaxenic cultures were grown at a light intensity of 50 ,uE m-2 s-1 in 500-ml Erlenmeyer flasks containing 200 ml of culture medium. The intracellular amount of PHB was determined by the UV method (11, 17) and by gas chromatographic (GC; 3) and high-performance liquid chromatographic (HPLC; 16) procedures.PHB determination by the UV method was not reliable because after sulfuric acid digestion, the absorption spectrum of the extracts revealed at 235 nm only a weak and scarcely detectable peak. Furthermore, the reproducibility * Corresponding author. of the method was quite unsatisfactory. PHB quantifications, tentatively made according to Law and Slepecky (17) and Fukui et al. (11), gave remarkable differences (Table 1), demonstrating the presence of UV-absorbing impurities in the extracts. However, the data agree in indicating a low level of PHB. Low concentrations of PHB in photoautotrophically grown Spirulina spp. were confirmed by both the GC and HPLC procedu...

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The Role and Regulation of Energy Reserve Polymers in Micro-organisms

Cited by 825 publications

References 274 publications

Methylobacillus: a New Genus of Obligately Methylotrophic Bacteria

Methylobacillus: a New Genus of Obligately Methylotrophic Bacteria

Bacterial polyhydroxyalkanoates-eco-friendly next generation plastic: Production, biocompatibility, biodegradation, physical properties and applications

Occurrence of poly-beta-hydroxybutyrate in Spirulina species

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