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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The amounts of glycogen and trehalose have been measured in cells of a prototrophic diploid yeast strain subjected to a variety of nutrient limitations. Both glycogen and trehalose were accumulated in cells deprived specifically of nirogen, sulfur, or phosphorus, suggesting that reserve carbohydrate accumulation is a general response to nutrient limitation. The patterns of accumulation and utilization of glycogen and trehalose were not identical under these conditions, suggesting that the two carbohydrates may play distinct physiological roles. Glycogen and trehalose were also accumulated by cells undergoing carbon and energy limitation, both during diauxic growth in a relatively poor medium and during the approach to stationary phase in a rich medium. Growth in the rich medium was shown to be carbon or energy limited or both, although the interaction between carbon source limitation and oxygen limitation was complex. In both media, the pattern of glycogen accumulation and utilization was compatible with its serving as a source of energy both during respiratory adaptation and during a subsequent starvation. In contrast, the pattern of trehalose accumulation and utilization seemed compatible only with the latter role. In cultures that were depleting their supplies of exogenous glucose, the accumulation of glycogen began at glucose concentrations well above those sufficient to suppress glycogen accumulation in cultures growing with a constant concentration of exogenous glucose. The mechanism of this effect is not clear, but may involve a response to the rapid rate of change in the glucose concentration.
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PMID:Reserve carbohydrate metabolism in Saccharomyces cerevisiae: responses to nutrient limitation. 699 70

The steady state concentration of carbohydrate and adenosine phosphate metabolites in rat and rabbit liver and in rabbit skeletal muscle and oxidative phosphorylation parameters of rat and rabbit liver mitochondria were compared. The effects of 24 hr starvation on the energy metabolism of liver and skeletal muscle of the animals were investigated. The steady state concentrations of glycogen and phosphoenolpyruvate in normal rabbit liver were found to be much lower than in the rat and other mammalian livers (45.7 mumoles of glucose equivalents and 38 nmoles of PEP per 1 g of liver wet mass, respectively). On the contrast, the concentrations of glucose 6-phosphate, pyruvate and Pi in rabbit skeletal muscle were unusually high (up to 3, 1 and 15 mumoles per 1 g, respectively). In terms of glucose, pyruvate, lactate, Pi, adenine nucleotide contents and cytosolic NAD+/NADH ratio in the liver, and glycogen, glucose, lactate, creatine and adenosine phosphates in skeletal muscle and oxidative and phosphorylated properties of isolated liver mitochondria, no significant differences between rat and rabbit were found. During 24 hr starvation gluconeogenesis in rabbit liver occurred earlier and was more intensive than in rat liver. This is indicative of the existence of interspecies differences in the control mechanisms of carbohydrate and phosphorus metabolism.
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PMID:[Comparative study of energy metabolism in the liver and skeletal muscles of rat and rabbit. Effect of starvation]. 727 60

The culturability of Vibrio cholerae O1 serotype Inaba strain 569B was decreased by the addition of glucose to cell suspensions in starvation media. A similar effect was observed with sucrose, maltose, and fructose. We term this inhibitory effect glucose shock. It was not observed with arabinose or xylose or with carboxylates, such as acetate and pyruvate. No acidification of the medium occurred in the presence of these carbohydrates. Glucose shock was prevented by the addition of nitrogen or phosphorus sources. In the presence of phosphate, the bacterium produced formic acid from glucose. The phenomenon of glucose shock was also observed in V. cholerae O1 serotype Inaba strain RIMD 2203082 but not in strain RIMD 2203088 (O1 Inaba), IID 936 (O1 Ogawa), or RIMD 2214034 (non-O1). The culturability of Escherichia coli, Enterobacter aerogenes, and Listonella anguillarum did not decrease in starvation media with added glucose. Hence, the phenomenon should have ecological significance in determining the distribution of bacteria in marine ecosystems in situations where carbohydrates are abundant, but nitrogen and phosphorus are limiting.
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PMID:Decrease in culturability of Vibrio cholerae caused by glucose. 761 70

A stable DNA/protein complex having an apparent molecular mass of approximately 150 kDa was purified from nitrate-limited cultures of the cyanobacterium Synechococcus sp. strain PCC 7942. Amino-terminal peptide sequencing indicated that the polypeptide was structurally similar to the Dps protein of Escherichia coli; Dps is also known as the product of the starvation- and stationary-phase-inducible gene, pexB. The 150-kDa complex dissociated into a 22-kDa protein monomer after boiling in 2% SDS. The 150-kDa complex preparation had approximately a 10% nucleic acid content and upon dissociation released DNA fragments that were sensitive to S1 nuclease digestion. Immunoblot data indicated that the complex accumulates during stationary phase and during nitrogen, sulfur, and phosphorus limitation. DNA-binding assays indicated that the protein nonspecifically binds both linear and supercoiled DNA. Circular dichroism spectroscopy revealed that the Synechococcus sp. Dps-like protein contains extensive regions of alpha-helical secondary structure. We propose that the 150-kDa complex represents a hexameric aggregate of the Dps-like protein complexed with single-stranded DNA and serves to bind a portion of the chromosomal DNA under nutrient-limited conditions.
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PMID:Purification and characterization of a Synechococcus sp. strain PCC 7942 polypeptide structurally similar to the stress-induced Dps/PexB protein of Escherichia coli. 779 1

The enzymes involved in the microbial metabolism of many important phosphorus- or sulfur-containing xenobiotics, including organophosphate insecticides and precursors to organosulfate and organosulfonate detergents and dyestuffs have been characterized. In several instances their genes have been cloned and analysed. For phosphonate xenobiotics, the enzyme system responsible for the cleavage of the carbon-phosphorus bond has not yet been observed in vitro, though much is understood on a genetic level about phosphonate degradation. Phosphonate metabolism is regulated as part of the Pho regulon, under phosphate starvation control. For organophosphorothionate pesticides the situation is not so clear, and the mode of regulation appears to depend on whether the compounds are utilized to provide phosphorus, carbon or sulfur for cell growth. The same is true for organosulfonate metabolism, where different (and differently regulated) enzymatic pathways are involved in the utilization of sulfonates as carbon and as sulfur sources, respectively. Observations at the protein level in a number of bacteria suggest that a regulatory system is present which responds to sulfate limitation and controls the synthesis of proteins involved in providing sulfur to the cell and which may reveal analogies between the regulation of phosphorus and sulfur metabolism.
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PMID:Microbial metabolism of sulfur- and phosphorus-containing xenobiotics. 794 67

Phycobilisomes are the multiprotein complexes predominantly responsible for harvesting light energy in cyanobacteria and some eukaryotic algae. When the cyanobacterium Synechococcus sp. strain PCC 7942 is deprived of an essential nutrient, the phycobilisomes are specifically and rapidly degraded. Degradation may be either partial (after phosphorus deprivation) or complete (after sulfur or nitrogen deprivation). We have developed a visual screen to obtain mutants unable to degrade their phycobilisomes upon nutrient starvation. Complementation of one of these mutants led to the identification of a gene, designated nblA, that encodes a 59 amino acid polypeptide essential for phycobilisome degradation. Transcription of nblA increases dramatically in sulfur- or nitrogen-deprived cells and moderately in phosphorus-deprived cells. Using the phosphorus-regulated alkaline phosphatase (phoA) promoter as a tool, we engineered constructs from which we could control the expression of either sense or antisense nblA. Increased expression of sense nbLA caused complete phycobilisome degradation during phosphorus deprivation, while expression of antisense nblA prevented phycobilisome degradation. Hence, nblA is necessary, and may be sufficient, for the degradation of phycobilisomes under adverse environmental conditions. Further investigation of the mechanism by which nblA causes phycobilisome destruction may reveal general principles that govern the specificity of macromolecular complex degradation.
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PMID:A small polypeptide triggers complete degradation of light-harvesting phycobiliproteins in nutrient-deprived cyanobacteria. 813 38

The purpose of this study was to investigate the energetic metabolism in obese Zucker rats, using phosphorus nuclear magnetic resonance spectroscopy at rest and during a 2-Hz muscle stimulation and subsequent recovery. Animals were anesthetized with ketamine (150 mg/kg ip). Fed obese rats and 2-day-fasted obese rats were compared with their normally fed and 2-day-fasted lean litter mates. No differences were found between the two groups for ATP, total creatine, phosphocreatine (PCr), and intracellular pH. Starvation in lean rats resulted in a significant fall in inorganic phosphate (Pi), increased resting ADP level, and decreased PCr and ADP recovery after stimulation. The obese rats exhibited a decreased PCr/Pi and increased ADP at rest and a decreased PCr resynthesis and ADP metabolization rate after stimulation. Muscle stimulation in fasted obese rats induced higher PCr depletion and more pronounced acidosis. These results suggest an in vivo mitochondrial metabolism dysfunction in fasted lean as well as in fed and fasted obese rats.
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PMID:Muscle bioenergetics in obese Zucker rats. 816 61

Non-differentiating bacteria adapt to starvation induced growth arrest by a complex turn-on/turn-off pattern of protein synthesis. This response shows distinct similarities with those of spore formation in differentiating organisms. A substantial amount of information on the non-growth biology of non-differentiating bacteria can be derived from studies on Vibrio strains. One important result is that carbon rather than nitrogen or phosphorus starvation leads to the development of a starvation and stress resistant cell in these organisms. Hence, we have attempted to characterize the carbon starvation stimulon. By the use of two-dimensional gel electrophoresis of pulse-labelled cells and transposon mutagenesis, using reporter gene constructs, the identity and function of some members of the carbon starvation stimulon have been elucidated. Moreover, regulatory genes of the starvation response have been identified with these techniques. Current studies primarily address the identity and function of these genes. The role of transcript modification and stability for both long term persistence during starvation as well as the efficient recovery of cells which occurs upon nutrient addition is also addressed. It is suggested that an understanding of the functionality of the translational machinery is essential for the understanding of these adaptive pathways. This contribution also discusses the diversity of the differentiation-like response to starvation in different bacteria and whether a general starvation induced programme exists.
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PMID:How do non-differentiating bacteria adapt to starvation? 827 28

A novel, metal-dependent, carbon-phosphorus bond cleavage activity, provisionally named phosphonoacetate hydrolase, was detected in crude extracts of Pseudomonas fluorescens 23F, an environmental isolate able to utilize phosphonoacetate as the sole carbon and phosphorus source. The activity showed unique specificity toward this substrate; its organic product, acetate, was apparently metabolized by the glyoxylate cycle enzymes of the host cell. Unlike phosphonatase, which was also detected in crude extracts of P. fluorescens 23F, phosphonoacetate hydrolase was inducible only in the presence of its sole substrate and did not require phosphate starvation.
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PMID:In vitro characterization of a phosphate starvation-independent carbon-phosphorus bond cleavage activity in Pseudomonas fluorescens 23F. 828 24

All genes for phosphonate (Pn) utilization in Escherichia coli are in a large cluster of 14 genes named, in alphabetical order, phnC to phnP. Plasmids carrying these genes were mutagenized by using TnphoA'-1, and 43 mutants containing simple insertions were studied in detail. Their insertion sites were defined by restriction mapping and by DNA sequencing. One or more mutations in each phn gene was identified. In 23 mutants, expression of the TnphoA'-1 lacZ gene was phosphate starvation inducible. These mutants had TnphoA'-1 oriented in line behind the phnC promoter, i.e., in the + orientation. In 20 mutants, the TnphoA'-1 lacZ gene was expressed at a low basal level. These mutants had insertions in the opposite orientation. All 43 phn::TnphoA'-1 insertions were recombined onto the chromosome to test for mutational effects, and their structures on the chromosome were verified by DNA hybridization. Those in the + orientation were switched to TnphoA'-9, which has an outward promoter for expression of downstream genes. These insertions were tested for polar effects by measuring beta-glucuronidase synthesis from a uidA gene transcriptionally fused to the 3' end of the phnP gene. The results indicate the following: (i) the phnC-to-phnP gene cluster is an operon of 14 genes, and the phnC promoter is the sole psi promoter; (ii) three gene products (PhnC, PhnD, and PhnE) probably constitute a binding protein-dependent Pn transporter; (iii) seven gene products (PhnG, PhnH, PhnI, PhnJ, PhnK, PhnL, and PhnM) are required for catalysis and are likely to constitute a membrane-associated carbon-phosphorus (C-P) lyase; (iv) two gene products (PhnN and PhnP) are not absolutely required and may therefore be accessory proteins for the C-P lyase; and (v) two gene products (PhnF and PhnO) are not required for Pn use and may have a regulatory role because they have sequence similarities to regulatory proteins. The mechanism for breaking the C-P bond by a lyase is discussed in light of these results.
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PMID:Mutational analysis of an Escherichia coli fourteen-gene operon for phosphonate degradation, using TnphoA' elements. 838 73


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