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

Salmonella enterica serovar Typhimurium (S. Typhimurium) elicits the starvation-stress response (SSR) due to starvation for an essential nutrient, e.g. a carbon/energy source (C-source). As part of the SSR, the alternative sigma factor sigma(E) is activated and induced. The authors suspect that this activation is, in part, triggered by changes in the S. Typhimurium cell envelope occurring during the adaptation from growth to carbon/energy starvation (C-starvation), and resulting in an increased need for sigma(E)-regulated factors involved in the proper folding and assembly of newly synthesized proteins destined for this extracytoplasmic compartment. This led to the hypothesis that a sigma(E) activation signal might arise during C-source shifts that cause the induction of proteins localized to the extracytoplasmic compartment, i.e. the outer membrane or periplasm, of the cell. To test this hypothesis, cultures were grown in minimal medium containing enough glucose to reach mid-exponential-phase, plus a non-limiting amount of a secondary 'less-preferred' but utilizable carbon/energy source. The sigma(E) activity was then monitored using plasmids carrying rpoEP1- and rpoEP2-lacZ transcriptional fusions, which exhibit sigma(E)-independent and -dependent lacZ expression, respectively. The secondary C-sources maltose, succinate and citrate, which have extracytoplasmic components involved in their utilization (e.g. LamB), resulted in a discernible diauxic lag period and a sustained increase in sigma(E) activity. Growth transition from glucose to other utilizable phosphotransferase (PTS) and non-PTS C-sources, such as trehalose, mannose, mannitol, fructose, glycerol, d-galactose or l-arabinose, did not cause a discernible diauxic lag period or a sustained increase in sigma(E) activity. Interestingly, a shift from glucose to melibiose, which does not use an extracytoplasmic-localized protein for uptake, did cause an observable diauxic lag period but did not result in a sustained increase in sigma(E) activity. In addition, overexpression of LamB from an arabinose-inducible promoter leads to a significant increase in sigma(E) activity in the absence of a glucose to maltose shift or C-starvation. Furthermore, a DeltalamB : : Omega-Km(r) mutant, lacking the LamB maltoporin, exhibited an approximately twofold reduction in the sustained sigma(E) activity observed during a glucose to maltose shift, again supporting the hypothesis. Interestingly, the LamB protein lacks the typical Y-X-F terminal tripeptide of the OmpC-like peptides that activate DegS protease activity leading to sigma(E) activation. It does, however, possess a terminal pentapeptide (Q-M-E-I-W-W) that may function as a ligand for a putative class II PDZ-binding site. The authors therefore propose that the sigma(E) regulon of S. Typhimurium not only is induced in response to deleterious environmental conditions, but also plays a role in the adaptation of cells to new growth conditions that necessitate changes in the extracytoplasmic compartment of the cell, which may involve alternative signal recognition and activation pathways that are independent of DegS.
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PMID:Shifts from glucose to certain secondary carbon-sources result in activation of the extracytoplasmic function sigma factor sigmaE in Salmonella enterica serovar Typhimurium. 1600 Jul 27

Enterobacter asburiae PSI3 is a rhizospheric isolate that solubilizes mineral phosphates by the action of a phosphate starvation-inducible GDH (EC 1.1.5.2). We report here that GDH activity of this isolate shows broad substrate range, being able to act on mono and disaccharides. Enterobacter asburiae PSI3 was proficient at bringing about a drop in pH and solubilization of RP with the use of 75 mmol/L of each of the GDH substrate sugars tested as the sole C source. It liberated amounts of P ranging from 450 micromol/L (on arabinose) to 890 micromol/L (on glucose). When grown on a mixture of 7 GDH substrates at concentrations of 15 mmol/L each, the bacterium solubilized RP equivalent to 46% of the value when 75 mmol glucose/L was the C source. HPLC analysis of the culture supernatant under these conditions showed that the acidification of the media is primarily due to the production of organic acids. The significance of these results on the efficacy of E. asburiae PSI3 at solubilizing phosphates under rhizospheric conditions is discussed.
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PMID:Substrate specificity of glucose dehydrogenase (GDH) of Enterobacter asburiae PSI3 and rock phosphate solubilization with GDH substrates as C sources. 1612 Dec 25

Growth conditions for heterotrophic bacteria in the environment are characterized by low concentrations of carbon and energy sources and complex substrate mixtures. While mechanisms of starvation-survival in the absence of carbon substrates have been studied in considerable detail, information on the physiology of slow growth under oligotrophic conditions is limited. We intended to elucidate general strategies by which Escherichia coli adapts to low concentrations of a mixed carbon and energy source pool. A new screening method based on BIOLOG AN MicroPlates, which allowed us to distinguish repressed and induced catabolic functions in E. coli, was combined with the analysis of periplasmic high-affinity binding proteins. Extending previous findings for E. coli and other microbial species, we found that numerous alternative catabolic functions and high-affinity binding proteins are derepressed under either glucose- or arabinose-limited growth conditions, in spite of the absence of the respective inducers. Escherichia coli cells growing in carbon-limited complex medium chemostat cultures exhibited an even higher degree of catabolic flexibility and were able to oxidize 43 substrates. The BIOLOG respiration pattern indicated simultaneous dissimilation of diverse sugars, amino acids and dipeptides (mixed substrate growth). The observed physiological adaptations of E. coli to low concentrations of carbon and energy substrates presumably are advantageous in many natural growth situations and also offer an explanation why many heterotrophic bacteria have and maintain such a broad carbon substrate range.
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PMID:Global physiological analysis of carbon- and energy-limited growing Escherichia coli confirms a high degree of catabolic flexibility and preparedness for mixed substrate utilization. 1615 30

Botrytis cinerea is the causal agent of grey mould disease and a non-host necrotrophic pathogen of maritime pine (Pinus pinaster). Recent evidence suggests that pathogen challenge can alter carbon uptake in plant cells; however, little is known on how elicitor-derived signalling pathways control sugar transport activity. P. pinaster suspended cells are able to absorb D-[14C]glucose with high affinity, have an H+-dependent transport system (Km, 0.07 mM; Vmax, 1.5 nmol min(-1) mg(-1) DW), are specific for D-glucose, D-fructose, D-galactose and D-xylose, and are subject to glucose repression. When elicited by B. cinera spores, suspended cells exhibit calcium-dependent biphasic reactive oxygen species (ROS) production, the second burst also being dependent on NADPH oxidase, mitogen-activated protein kinase (MAPK), and de novo transcription and protein synthesis. Challenging suspended cells incubated in sugar-free medium resulted in an up to 3-fold increase in glucose transport capacity over non-elicited cultures 24 h after elicitation, and a 14-fold increase over elicited cells incubated with 2% glucose. Enhanced glucose uptake depended on NADPH oxidase and calcium influx, but not MAPK. In contrast, the increase of glucose transport activity induced by sugar starvation was dependent on the activation of MAPK but not NADPH oxidase. Both responses appeared to be dependent on de novo transcription and protein synthesis.
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PMID:The non-host pathogen Botrytis cinerea enhances glucose transport in Pinus pinaster suspension-cultured cells. 1640 93

Chemotaxis may be important when forming cyanobacterial symbioses. However, knowledge of cyanobacterial attraction towards plants and factors affecting chemotaxis is limited. Chemo-attraction was observed in Nostoc strains 8964:3 and PCC 73102 towards exudate or crushed extract of the natural hosts Gunnera manicata, Cycas revoluta and Blasia pusilla, and the nonhost plants Trifolium repens, Arabidopsis thaliana and Oryza sativa. As all tested plant extracts generated chemotaxis, the possibility to attract cyanobacteria may be widespread in plants. Chemotaxis was reduced by increased temperature and darkness and was stimulated by phosphorous and iron starvation and elevated salt concentration. Sugars (arabinose, galactose, and glucose) had a positive effect on chemotaxis, whereas flavonoids (chrysin and naringenin) and amino acids (methionine, glycine, serine, phenylalanine, glutamine, and lysine) had no effect.
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PMID:Cyanobacterial chemotaxis to extracts of host and nonhost plants. 1646 77

Lignocellulosic biomass, rich in hexose and pentose sugars, is an attractive resource for commercially viable bioethanol production. Saccharomyces cerevisiae efficiently ferments hexoses but is naturally unable to utilize pentoses. Metabolic engineering of this yeast has resulted in strains capable of xylose utilization. However, even the best recombinant S. cerevisiae strains of today metabolize xylose with a low rate compared to glucose. This study compares the transcript profiles of an S. cerevisiae strain engineered to utilize xylose via the xylose reductase-xylitol dehydrogenase pathway in aerobic chemostat cultures with glucose or xylose as the main carbon source. Compared to the glucose culture, 125 genes were upregulated, whereas 100 genes were downregulated in the xylose culture. A number of genes encoding enzymes capable of nicotinamide adenine dinucleotide phosphate regeneration were upregulated in the xylose culture. Furthermore, xylose provoked increased activities of the pathways of acetyl-CoA synthesis and sterol biosynthesis. Notably, our results suggest that cells metabolizing xylose are not in a completely repressed or in a derepressed state either, indicating that xylose was recognized neither as a fermentable nor as a respirative carbon source. In addition, a considerable number of the changes observed in the gene expression between glucose and xylose samples were closely related to the starvation response.
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PMID:Transcription analysis of recombinant saccharomyces cerevisiae reveals novel responses to xylose. 1663 84

Treatment of pea stem segments with indoleacetic acid (IAA) causes within 1 hour a 2- to 4-fold increase in activity of particulate uridine diphosphoglucose-dependent beta-glucan synthetase obtainable from the tissue. The IAA effect is observable in tissue from all parts of the elongation zone of the pea stem, and also in older tissue that is not capable of a cell enlargement response to IAA. A large increase in activity is caused by IAA only if synthetase activity in the isolated tissue has first been allowed to fall substantially below the intact plant level, and only if sucrose is supplied along with IAA. Treatment of tissue with sucrose alone after a period of sugar starvation causes a transient rise of synthetase activity. The decline in synthetase activity in absence of IAA, the rise caused by IAA, and the transient rise caused by sucrose are all strongly temperature-dependent. IAA and sucrose do not affect the activity of isolated synthetase particles. Synthetase activity in vivo is sensitive to as low as 0.1 mum IAA and is increased by IAA analogues that are active as auxins on elongation but not by nonauxin analogues. Activity begins to rise 10 to 15 minutes after exposure to IAA, which places this among the most rapid enzyme effects of a plant growth regulator heretofore demonstrated, and among the most rapid known metabolic effects of auxins. The effect is seen also with polysaccharide synthetase activity using uridine diphosphate-galactose or uridine diphosphate-xylose as substrates, and to a lesser extent with guanosine diphosphoglucose-dependent glucan synthetase activity. Glucan synthetase from IAA-treated tissue appears to have a higher affinity for uridine diphosphate-glucose than the control.
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PMID:Regulation of beta-Glucan Synthetase Activity by Auxin in Pea Stem Tissue: I. Kinetic Aspects. 1665 79

We used a proteomic approach to identify constitutively formed extracellular proteins of Hypocrea atroviridis (Trichoderma atroviride), a known biocontrol agent. The fungus was cultivated on glucose and the secretome was examined by two-dimensional gel electrophoresis. The two predominant spots were identified by MALDI MS utilizing peptide mass fingerprints and amino acid sequence tags obtained by postsource decay and/or high-energy collision-induced dissociation (MS/MS) experiments, and turned out to be the same protein (12 629 Da as determined with MS, pI 5.5-5.7), probably representing the monomer and the dimer. The corresponding gene was subsequently cloned from H. atroviridis and named epl1 (eliciting plant response-like), because it encodes a protein that exhibits high similarity to the cerato-platanin family, which comprises proteins such as cerato-platanin from Ceratocystis fimbriata f. sp. platani and Snodprot1 of Phaeosphaeria nodorum, which have been reported to be involved in plant pathogenesis and elicitation of plant defense responses. Additionally, based on the similarity of the N-terminus to that of H. atroviridis Epl1, we conclude that a previously identified 18 kDa plant response elicitor isolated from T. virens is an ortholog of epl1. Our results showed that epl1 transcript was present under all growth conditions tested, which included the carbon sources glucose, glycerol, l-arabinose, d-xylose, colloidal chitin and cell walls of the plant pathogen Rhizoctonia solani, and also plate confrontation assays with R. solani. Epl1 transcript could even be detected under osmotic stress, and carbon and nitrogen starvation.
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PMID:Epl1, the major secreted protein of Hypocrea atroviridis on glucose, is a member of a strongly conserved protein family comprising plant defense response elicitors. 1693 25

Myxococcus xanthus, a gram-negative soil bacterium, responds to amino acid starvation by entering a process of multicellular development which culminates in the assembly of spore-filled fruiting bodies. Previous studies utilizing developmental inhibitors (such as methionine, lysine, or threonine) have revealed important clues about the mechanisms involved in fruiting body formation. We used Biolog phenotype microarrays to screen 384 chemicals for complete inhibition of fruiting body development in M. xanthus. Here, we report the identification of a novel inhibitor of fruiting body formation and sporulation, beta-d-allose. beta-d-Allose, a rare sugar, is a member of the aldohexose family and a C3 epimer of glucose. Our studies show that beta-d-allose does not affect cell growth, viability, agglutination, or motility. However, beta-galactosidase reporters demonstrate that genes activated between 4 and 14 h of development show significantly lower expression levels in the presence of beta-d-allose. Furthermore, inhibition of fruiting body formation occurs only when beta-d-allose is added to submerged cultures before 12 h of development. In competition studies, high concentrations of galactose and xylose antagonize the nonfruiting response to beta-d-allose, while glucose is capable of partial antagonism. Finally, a magellan-4 transposon mutagenesis screen identified glcK, a putative glucokinase gene, required for beta-d-allose-mediated inhibition of fruiting body formation. Subsequent glucokinase activity assays of the glcK mutant further supported the role of this protein in glucose phosphorylation.
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PMID:Beta-D-Allose inhibits fruiting body formation and sporulation in Myxococcus xanthus. 1705 49

Three Arabidopsis genes encoding a putative beta-galactosidase (At5g56870), beta-xylosidase (At5g49360) and beta-glucosidase (At3g60140) are induced by sugar starvation. The deduced proteins belong to the glycosyl hydrolase families 35, 3 and 1, respectively. They are predicted to be secretory proteins that play roles in modification of cell wall polysaccharides based on amino acid similarity. The beta-galactosidase encoded by At5g56870 was identified as a secretory protein in culture medium of suspension cells by mass spectrometry analysis. This protein was specifically detected under sugar-starved conditions with a specific antibody. Induction of these genes was repressed in suspension cells grown with galactose, xylose and glucose, as well as with sucrose. In planta, expression of the genes and protein accumulation were detected when photosynthesis was inhibited. Glycosyl hydrolase activity against galactan also increased during sugar starvation. The amount of monosaccharide in pectin and hemicellulose in detached leaves decreased in response to sugar starvation. These findings suggest that the cell wall may function as a storage reserve of carbon in addition to providing physical support for the plant body.
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PMID:Glycosyl hydrolases of cell wall are induced by sugar starvation in Arabidopsis. 1723 72


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