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At least 1,531 records · Page 85Linked to original sources
PubMed1998

The Escherichia coli starvation gene cstC is involved in amino acid catabolism.

Escherichia coli strains mutant in the starvation gene cstC grow normally in a mineral salts medium but are impaired in utilizing amino acids as nitrogen sources. They are also compromised in starvation survival, where amino acid catabolism is important. The cstC gene encodes a 406-amino-acid protein that closely resembles the E. coli ArgD protein, which is involved in arginine biosynthesis. We postulate that CstC is a counterpart of ArgD in an amino acid catabolic pathway. The cstC upstream region contains several regulatory consensus sequences. Both sigmaS and sigma54 promoters are probably involved in cstC transcription and appear to compete with each other, presumably to match cstC expression to the cellular amino acid catabolic needs.

Amino Acid Sequence↗
PubMed1999

CtaA of Staphylococcus aureus is required for starvation survival, recovery, and cytochrome biosynthesis.

A Staphylococcus aureus mutant (SPW3) apparently unable to survive long-term starvation was shown to have a transposon insertion within a gene homologous to ctaA of Bacillus subtilis which encodes a heme A synthase. Analysis of the cytochrome profiles of SPW3 revealed the absence of heme A-containing cytochromes compared to the parental 8325-4 strain. SPW3 demonstrated a 100-fold reduction in the ability to survive starvation induced by glucose limitation, under aerated conditions, compared to 8325-4. Analysis of starved cultures revealed that greater than 90% of the cells which demonstrated metabolism (as shown by rhodamine 123 accumulation) were unable to recover and form colonies on agar. Analysis of the lag phase and initial growth kinetics of those cells which could recover also showed a defect. This recovery defect could be partially alleviated by the inclusion of catalase in the recovery medium, indicating the probable involvement of oxidative stress. SPW3 also exhibited reduced colony size similar to that of a small-colony variant, increased resistance to aminoglycoside antibiotics, and reduced hemolysin and toxic shock syndrome toxin 1 production, but no alteration in the ability to form lesions in a subcutaneous mouse infection model.

Aerobiosis↗
PubMed1999

Cell density-dependent starvation survival of Rhizobium leguminosarum bv. phaseoli: identification of the role of an N-acyl homoserine lactone in adaptation to stationary-phase survival.

The cell density dependence of stationary-phase survival of Rhizobium leguminosarum has been investigated. Following starvation by exhaustion of carbon or nitrogen, but not of phosphorus, the survival of cultures was dependent on the cell density at entry into stationary phase. High-density cultures survived with little or no loss of viability over a 20-day period in stationary phase. In contrast, low-density cultures lost viability rapidly but consisted of a heterogeneous population, a small fraction of which successfully adapted and eventually formed a stable, surviving population. The threshold density above which the cultures survived successfully in stationary phase was dependent on the growth conditions and the strain used. We took advantage of the fact that R. leguminosarum survives poorly following starvation by resuspension in carbon-free medium to demonstrate that cell density-dependent survival was mediated by a component accumulating in the growth medium. The effects of this medium component on survival in resuspension assays could be mimicked by an N-acyl homoserine lactone, N-(3R-hydroxy-7-cis-tetradecanoyl)-L-homoserine lactone, previously demonstrated to have a role in controlling cell density-dependent phenomena in R. leguminosarum. The Sym plasmids pRP2JI and pRL1JI were found to be essential for the production of the extracellular factor, which could also be made in Escherichia coli carrying the cosmid clone pIJ1086 containing a specific region of pRL1JI.

Colony Count, Microbial↗
PubMed2000

A common step for changing cell shape in fruiting body and starvation-independent sporulation of Myxococcus xanthus.

Myxococcus xanthus can sporulate in either of two ways: at the end of the program of fruiting body development or after exposure of growing cells to certain reagents such as concentrated glycerol. Fruiting body sporulation requires starvation, while glycerol sporulation requires rapid growth, and since the two types of spores are structurally somewhat different, it has generally been assumed that the two processes are different. However, a Tn5 Lac insertion mutation, Omega7536, has been isolated which simultaneously blocks the development of fruiting body spores as well as glycerol-induced spores. Both sporulation pathways are blocked in the mutant within the process that converts a rod-shaped cell into a spherical spore. The Omega7536 locus is expressed at the time of cell shape change appropriate to each process, early after glycerol induction and late after starvation induction. On the C-signal response pathway, it is possible to identify positions for the normal function of the Omega7536 locus and for the inducing stimulus from glycerol that are unique and consistent with the observations. Although the two sporulation pathways differ in certain respects, it is shown that they share at least one step for changing a rod-shaped cell into a spherical spore.

Bacterial Proteins↗
PubMed2000

Functional analysis of PvdS, an iron starvation sigma factor of Pseudomonas aeruginosa.

In Pseudomonas aeruginosa, iron modulates gene expression through a cascade of negative and positive regulatory proteins. The master regulator Fur is involved in iron-dependent repression of several genes. One of these genes, pvdS, was predicted to encode a putative sigma factor responsible for the transcription of a subset of genes of the Fur regulon. PvdS appears to belong to a structurally and functionally distinct subgroup of the extracytoplasmic function family of alternative sigma factors. Members of this subgroup, also including PbrA from Pseudomonas fluorescens, PfrI and PupI from Pseudomonas putida, and FecI from Escherichia coli, are controlled by the Fur repressor, and they activate transcription of genes for the biosynthesis or the uptake of siderophores. Evidence is provided that the PvdS protein of P. aeruginosa is endowed with biochemical properties of eubacterial sigma factors, as it spontaneously forms 1:1 complexes with the core fraction of RNA polymerase (RNAP, alpha(2)betabeta' subunits), thereby promoting in vitro binding of the PvdS-RNAP holoenzyme to the promoter region of the pvdA gene. These functional features of PvdS are consistent with the presence of structural domains predicted to be involved in core RNAP binding, promoter recognition, and open complex formation. The activity of pyoverdin biosynthetic (pvd) promoters was significantly lower in E. coli overexpressing the multicopy pvdS gene than in wild-type P. aeruginosa PAO1 carrying the single gene copy, and pvd::lacZ transcriptional fusions were silent in both pfrI (the pvdS homologue) and pfrA (a positive regulator of pseudobactin biosynthetic genes) mutants of P. putida WCS358, while they are expressed at PAO1 levels in wild-type WCS358. Moreover, the PvdS-RNAP holoenzyme purified from E. coli lacked the ability to generate in vitro transcripts from the pvdA promoter. These observations suggest that at least one additional positive regulator could be required for full activity of the PvdS-dependent transcription complex both in vivo and in vitro. This is consistent with the presence of a putative activator binding site (the iron starvation box) at variable distance from the transcription initiation sites of promoters controlled by the iron starvation sigma factors PvdS, PfrI, and PbrA of fluorescent pseudomonads.

Amino Acid Sequence↗
PubMed2004

Diversion of the metabolic flux from pyruvate dehydrogenase to pyruvate oxidase decreases oxidative stress during glucose metabolism in nongrowing Escherichia coli cells incubated under aerobic, phosphate starvation conditions.

Ongoing aerobic metabolism in nongrowing cells may generate oxidative stress. It is shown here that the levels of thiobarbituric acid-reactive substances (TBARSs), which measure fragmentation products of oxidized molecules, increased strongly at the onset of starvation for phosphate (P(i)). This increase in TBARS levels required the activity of the histone-like nucleoid-structuring (H-NS) protein. TBARS levels weakly increased further in DeltaahpCF mutants deficient in alkyl hydroperoxide reductase (AHP) activity during prolonged metabolism of glucose to acetate. Inactivation of pyruvate oxidase (PoxB) activity decreased the production of acetate by half and significantly increased the production of TBARS. Overall, these data suggest that during incubation under aerobic, P(i) starvation conditions, metabolic flux is diverted from the pyruvate dehydrogenase (PDH) complex (NAD dependent) to PoxB (NAD independent). This shift may decrease the production of NADH and in turn the adventitious production of H(2)O(2) by NADH dehydrogenase in the respiratory chain. The residual low levels of H(2)O(2) produced during prolonged incubation can be scavenged efficiently by AHP. However, high levels of H(2)O(2) may be reached transiently at the onset of stationary phase, primarily because H-NS may delay the metabolic shift from PDH to PoxB.

Aerobiosis↗
PubMed2005

Transcriptome analysis of the progressive adaptation of Lactococcus lactis to carbon starvation.

Adaptation of Lactococcus lactis towards progressive carbon starvation is mediated by three different types of transcriptomic responses: (i) global responses, i.e., general decreases of functions linked to bacterial growth and lack of induction of the general stress response; (ii) specific responses functionally related to glucose exhaustion, i.e., underexpression of central metabolism genes, induction of alternative sugar transport and metabolism, and induction of the arginine deiminase pathway; and (iii) other responses never described previously during carbon starvation.

Adaptation, Physiological↗
PubMed2005

Iron starvation leads to oxidative stress in Anabaena sp. strain PCC 7120.

We establish here that iron deficiency causes oxidative stress in the cyanobacterium Anabaena sp. strain PCC 7120. Iron starvation leads to a significant increase in reactive oxygen species, whose effect can be abolished by treatment with the antioxidant tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl). Oxidative stress induced by iron starvation could be a common feature of photosynthetic bacteria.

Anabaena↗
PubMed2005

Investigation of the first events leading to loss of culturability during Escherichia coli starvation: future nonculturable bacteria form a subpopulation.

In previous experiments we were able to separate, using a nondestructive separation technique, culturable and nonculturable bacteria, from a Luria-Bertani (LB) medium culture of Escherichia coli incubated for 48 h. We observed in the nonculturable bacterial population an increase in oxidative damage and up-induction of most defenses against reactive oxygen species (ROS), along with a decrease in cytoplasmic superoxide dismutases. In this study, using the same separation technique, we separated into two subpopulations a 10-h LB medium culture containing only culturable bacteria. For the first time, we succeeded in associating physical separation with physiological differences. Although the levels of defense against ROS (RpoS, RpoH, OxyR, and SoxRS regulons) and oxidative damage (carbonyl contents) were apparently the same, we found that bacteria in one subpopulation were more sensitive to LB medium starvation and to various stresses, such as phosphate buffer starvation, heat shock, and hydrogen peroxide exposure. Based on these results, we suggest that these physiological differences reflect uncharacterized bacterial modifications which do not directly involve defenses against ROS.

Culture Media↗
PubMed1969

Regulation of chromosome replication in Bacillus subtilis: effects of amino acid starvation in strain 168.

Regulation of chromosome replication in Bacillus subtilis strain 168, in response to starvation for an essential amino acid, was found to differ from that reported for Escherichia coli. Not all replication points stop at the terminus during amino acid starvation. There is some evidence, however, to indicate that preferred stopping sites might exist. Initiation at the origin can occur in the absence of total protein synthesis as well as when the deoxyribonucleic acid (DNA)- mass ratio is unbalanced. DNA synthesis appears to be controlled independently of the initiation event by a second regulatory circuit, that may utilize the DNA-mass ratio. Once initiated, chromosome replication does not always go to completion in an uninterrupted sequence.

Amino Acids↗
PubMed2005

Severe adenine starvation activates Ty1 transcription and retrotransposition in Saccharomyces cerevisiae.

Ty1 retrotransposons of the yeast Saccharomyces cerevisiae are activated by different kinds of stress. Here we show that Ty1 transcription is stimulated under severe adenine starvation conditions. The Bas1 transcriptional activator, responsible for the induction of genes of the de novo AMP biosynthesis pathway (ADE) in the absence of adenine, is not involved in this response. Activation occurs mainly on Ty1 elements, whose expression is normally repressed by chromatin and is suppressed in a hta1-htb1Delta mutant that alters chromatin structure. Activation is also abolished in a snf2Delta mutant. Several regions of the Ty1 promoter are necessary to achieve full activation, suggesting that full integrity of the promoter sequences might be important for activation. Together, these observations are consistent with a model in which the activation mechanism involves chromatin remodeling at Ty1 promoters. The consequence of Ty1 transcriptional activation in response to adenine starvation is an increase in Ty1 cDNA levels and a relief of Ty1 dormancy. The retrotransposition of four native Ty1 elements increases in proportion to their increase in transcription. Implications for the regulation of Ty1 mobility by changes in Ty1 mRNA levels are discussed.

Adenine↗
PubMed1984

Polyamine starvation prolongs the S and G2 phases of polyamine-dependent (arginase-deficient) CHO cells.

This study analyzes the effects of polyamine starvation on cell cycle traverse of an arginase-deficient CHO cell variant (CHO-A7). These cells grow well in serum-free medium, provided that it contains ornithine or polyamines or both. In the absence of ornithine or polyamines or both, the CHO-A7 cells develop severe polyamine deficiency and, as a consequence, grow more slowly. When grown to a stationary phase in the presence of ornithine or putrescine or both, the CHO-A7 cells became arrested in G0/early G1. However, when starved for ornithine and polyamines, they accumulated in the S and G2 phases. Ornithine and polyamine starvation of CHO-A7 cells causes an increase in ornithine decarboxylase activity. When this increase was prevented by treatment with DL-alpha-difluoromethylornithine, an enzyme-activated irreversible inhibitor of ornithine decarboxylase, growth was further suppressed, and a greater fraction of cells were found in the S and G2 phases of the cell cycle.

Animals↗
PubMed1980

Viability and depletion of cell constituents of Methanospirillum hungatii GP1 during starvation.

The viability of Methanospirillum hungatii GP1 cells dropped rapidly when starved in a pH 7.0 phosphate buffer under 100% N2 or 90% N2 - 10% H2 gas phase. The presence of H2 during starvation tests resulted in a more rapid and an ultimately greater reduction of the number of initially viable cells than in the presence of N2 only. The decrease in viability was observed concurrently with the decline of the ATP pool and the RNA content of the cells. The cell protein, carbohydrate, and amino acid pool also decreased. The cellular DNA content which increased initially under both gas phases subsequently decreased under N2-H2 gas phase. However, there was no net decline in the DNA content of the cells. The results indicate that M. hungatii would not survive prolonged periods of starvation.

Adenosine Triphosphate↗
PubMed1981

Starvation suppresses sympathoadrenal medullary response to cold exposure in rats.

The effect of 2 days (55 h) of starvation on the functional state of the sympathetic nervous system (SNS) and adrenal medulla in male rats was evaluated in both normal (24 degrees C) and cold (4 degrees C) environments. Fasting (24 degrees C) significantly decreased NE turnover in heart and spleen, and the concentration of plasma epinephrine (E) and norepinephrine (NE). Cold exposure in the fed animals significantly increased NE turnover in the heart and plasma E, but had no effect on plasma NE or spleen NE turnover compared to normal (no stress) conditions. Cardiac NE turnover was 50% less in fasted cold-stressed animals than in fed cold-stressed animals. Plasma E remained at low levels. Plasma concentration of free fatty acids was significantly elevated in the fasted state in both warm and cold environments. These results suggest that 2 days of starvation in adult male rats suppresses the activity of the SNS and adrenal medulla and interferes with the normal adrenergic response to cold stress. Moreover, E appears not to be essential for mobilization of fat stores for energy metabolism in the fasted state in either warm or moderately cold environments.

Adrenal Medulla↗
PubMed2004

Starvation response in mouse liver shows strong correlation with life-span-prolonging processes.

We have monitored global changes in gene expression in mouse liver in response to fasting and sugar-fed conditions using high-density microarrays. From approximately 20,000 different genes, the significantly regulated ones were grouped into specific signaling and metabolic pathways. Striking changes in lipid signaling cascade, insulin and dehydroepiandrosterone (DHEA) hormonal pathways, urea cycle and S-adenosylmethionine-based methyl transfer systems, and cell apoptosis regulators were observed. Since these pathways have been implicated to play a role in the aging process, and since we observe significant overlap of genes regulated upon starvation with those regulated upon caloric restriction, our analysis suggests that starvation may elicit a stress response that is also elicited during caloric restriction. Therefore, many of the signaling and metabolic components regulated during fasting may be the same as those which mediate caloric restriction-dependent life-span extension.

ATP-Binding Cassette Transporters↗
PubMed2006

Identification of arctigenin as an antitumor agent having the ability to eliminate the tolerance of cancer cells to nutrient starvation.

Tumor cells generally proliferate rapidly and the demand for essential nutrients as well as oxygen always exceeds the supply due to the unregulated growth and the insufficient and inappropriate vascular supply. However, cancer cells show an inherent ability to tolerate extreme conditions, such as that characterized by low nutrient and oxygen supply, by modulating their energy metabolism. Thus, targeting nutrient-deprived cancer cells may be a novel strategy in anticancer drug development. Based on that, we established a novel screening method to discover anticancer agents that preferentially inhibit cancer cell viability under the nutrient-deprived condition. After screening 500 medicinal plant extracts used in Japanese Kampo medicine, we found that a CH(2)Cl(2)-soluble extract of Arctium lappa exhibited 100% preferential cytotoxicity under the nutrient-deprived condition at a concentration of 50 microg/mL with virtually no cytotoxicity under nutrient-rich condition. Further bioassay-guided fractionation and isolation led to the isolation of arctigenin as the primary compound responsible for such preferential cytotoxicity; the compound exhibited 100% preferential cytotoxicity against nutrient-deprived cells at a concentration of 0.01 microg/mL. Furthermore, arctigenin was also found to strongly suppress the PANC-1 tumor growth in nude mice, as well as the growth of several of the tested pancreatic cancer cell lines, suggesting the feasibility of this novel antiausterity approach in cancer therapy. Further investigation of the mechanism of action of arctigenin revealed that the compound blocked the activation of Akt induced by glucose starvation, which is a key process in the tolerance exhibited by cancer cells to glucose starvation.

Animals↗
PubMed1987

Accelerated starvation in pregnancy: implications for dietary treatment of obesity and gestational diabetes mellitus.

The biological significance of ketonemia of brief duration and moderate proportions during pregnancy remains uncertain. Thus, controversy persists about whether caloric restriction for obese women during pregnancy, particularly when the obesity is complicated by gestational diabetes mellitus (GDM), constitutes appropriate therapy. We have demonstrated, in a rigorously controlled setting using a Clinical Research Center, that all of the features of 'accelerated starvation' become manifest after 14 h and before 18 h of dietary deprivation. Women with GDM exhibit the same capacity for early 'accelerated starvation' as in normal pregnancy; thus, their insulin deficiency and insulin resistance do not appear to be sufficient to render them increasedly at risk for uncontrolled catabolism. Some cautious exploration of the use of hypocaloric diets as a therapeutic approach to the metabolic disturbances of GDM may be justified.

3-Hydroxybutyric Acid↗
PubMed1987

Induction of HL-60 differentiation by starvation for a single essential amino acid but not by protein synthesis inhibitors.

Starvation for a single essential amino acid induced differentiation of the human promyelocytic leukemia line HL-60 into morphologically and functionally mature granulocytes. Differentiation occurred when protein synthesis was inhibited up to 90% but was not simply secondary to growth arrest or protein synthesis inhibition, because neither glucose starvation nor treatment with protein synthesis inhibitors induced differentiation. Induction of differentiation by an aminoacyl tRNA synthetase inhibitor and the effect of cycloheximide and puromycin on amino acid-starved cells suggested an important regulatory role of tRNA molecules during differentiation.

Amino Acids, Essential↗