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

In Anabaena sp. strain PCC 7120, vegetative cell ferredoxin synthesis under iron starvation was repressed 25-fold, whereas heterocyst ferredoxin synthesis decreased only 2.8-fold. Induction of flavodoxin under iron depletion was independent of the availability of combined nitrogen. Under iron stress but in the presence of combined nitrogen, fdxH and nifH genes were transcriptionally active; although excision of the 11-kb element seemed to be completed, nitrogenase activity and the fdxH gene product were not detectable.
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PMID:Transcriptional and translational analysis of ferredoxin and flavodoxin under iron and nitrogen stress in Anabaena sp. strain PCC 7120. 796 17

Iron is an essential element for bacterial growth. Its intracellular concentration is mainly controlled at the uptake level, which is mediated by iron-dicitrate transport in various prokaryotes. We report here that the cyanobacterium Synechocystis PCC6803 takes up iron from ferric citrate. This process is dependent of the iron:citrate ratio, with a better efficiency for the highest concentration of citrate. The iron-citrate complex is the substrate of this active uptake, inhibited in part by the uncoupler FCCP. Iron starvation activates this uptake. These data suggest the existence of a specific ferric citrate receptor on the cyanobacterial membrane.
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PMID:Uptake of iron from ferric-citrate in the cyanobacteria Synechocystis PCC6803. 801 87

Iron starvation interferes drastically with the multiplication and virulence of Salmonella typhi mutants defective in enterochelin synthesis or enterochelin transport. Growth of these mutants is inhibited in the presence of human sera and unsaturated transferrin and is restored by fully saturated transferrin. The mutants exhibit decreased ability to grow in HeLa cell monolayers and are attenuated in mice. These findings are consistent with the S. typhi enterochelin system playing a role in the pathogenesis of typhoid fever.
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PMID:Salmonella typhi iron uptake mutants are attenuated in mice. 806 32

Although the relationship between starvation and reduced resistance to infection has been suggested by historical accounts of famines and pestilence and by recent epidemiologic studies, the concept of nutritional deficiency causing impairment of immunocompetence is relatively recent. In PEM (protein-energy malnutrition), most of the host defence mechanisms are breached, especially manifested in reduced cell-mediated immunity. One plausible reason is the reduction in mature fully differentiated T lymphocytes. Recent immunological methods made it possible to analyze its precise mechanism and process in detail. Naturally occurring states of malnutrition are difficult to interpret largely because deficiencies usually involve multiple dietary factors. It is obvious that single nutrients can only be analyzed in defined and controlled animal experiments. Role of micronutrients such as zinc, iron, and vitamins, specific amino acids such as arginine, glutamine, and fat on immunological responses have been paid attention on their specific actions and some of them have been investigated in humans as well.
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PMID:[Role of malnutrition on immunity]. 812 95

Introduction of a Pseudomonas iron-regulated promoter lacZ fusion (SP1) and a Pseudomonas transcriptional factor into Escherichia coli allowed expression of the promoter in this heterologous host. Evaluation of this promoter in wild-type and fur mutants of E. coli, by measuring beta-galactosidase activity, indicated that E. coli Fur can regulate the Pseudomonas promoter in response to iron starvation. Gel retardation assays suggested that purified Fur protein could interact with the SP1 promoter upstream of the transcriptional start. DNase I footprinting analysis established that Fur protected a primary 58-bp region (-50 to -106 bp). These protein/DNA interactions correlate with the observed in vivo regulation of the SP1 promoter in E. coli and indicate that Fur can functionally regulate a Pseudomonas iron-regulated promoter.
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PMID:Escherichia coli ferric uptake regulator (Fur) can mediate regulation of a pseudomonad iron-regulated promoter. 820 May 8

A 26-kDa outer membrane protein (Omp26) has been proposed to play a role in hemin acquisition by Porphyromonas gingivalis (T. E. Bramanti and S. C. Holt, J. Bacteriol. 174:5827-5839, 1992). We studied [55Fe]hemin uptake in P. gingivalis grown under conditions of hemin starvation (Omp26 expressed on the outer membrane surface) and hemin excess (Omp26 not expressed on surface). [55Fe]hemin uptake occurred rapidly in hemin-starved cells which incorporated up to 70% of total [55Fe]hemin within 3 min. P. gingivalis grown under hemin-starved conditions or treated with the iron chelator 2,2'-bipyridyl to induce an iron stress took up six times more [55Fe]hemin than hemin-excess-grown cells. Polyclonal monospecific anti-Omp26 antibody added to hemin-starved cells inhibited [55Fe]hemin uptake by more than 50%, whereas preimmune serum had no effect. [55Fe]hemin uptake in hemin-starved P. gingivalis was inhibited (36 to 67%) in the presence of equimolar amounts of unlabeled hemin, protoporphyrin IX, zinz protoporphyrin, and Congo red dye but was not inhibited in the presence of non-hemin-containing iron sources. Heat shock treatment (45 degrees C) of hemin-excess-grown P. gingivalis (which cases translocation of Omp26 to the surface) increased [55Fe]hemin uptake by threefold after 3 min in comparison with cells grown at 37 degrees C. However, no [55Fe] hemin uptake beyond 3 min was observed in either hemin-excess-grown or hemin-starved cells exposed to heat shock. In experiments using heterobifunctional cross-linker analysis, hemin and selected porphyrins were cross-linked to Omp26 in hemin-starved P. gingivalis, but no cross-linking was seen with hemin-excess-grown cells. However, cross-linking of hemin to Omp26 was observed after heat shock treatment of hemin-excess-grown cells. Finally, anti-Omp26 antibody inhibited cross-linked of hemin to Omp26. These findings indicate that hemin binding and transport into P.gingivalis cell mediated by Omp26.
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PMID:Hemin uptake in Porphyromonas gingivalis: Omp26 is a hemin-binding surface protein. 822 88

A new member of the yeast yAP family, designated YAP2, has been isolated and characterized. The protein displays a high homology with the DNA-binding domain of yAP-1, which contains a basic DNA-binding domain and leucine zipper motif and binds in vitro to the same cis-element. Growth arrest of yeast caused by low concentrations of 1,10-phenanthroline, resulting in zinc and/or iron deprivation, is overcome by over-expression of YAP1 or YAP2. In fact, yeast cells over-expressing YAP1 or YAP2 display pleiotropic drug resistance. On the other hand, a yap2 null mutant has an increased thermotolerance under starvation conditions caused by 1,10-phenanthroline. The latter mutant might become an excellent tool in the study of pathways leading toward thermotolerance acquisition.
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PMID:Overexpression of YAP2, coding for a new yAP protein, and YAP1 in Saccharomyces cerevisiae alleviates growth inhibition caused by 1,10-phenanthroline. 822 90

Attempts were made to maximize the expression of ice nuclei in Pseudomonas syringae T1 isolated from a tomato leaf. Nutritional starvation for nitrogen, phosphorous, sulfur, or iron but not carbon at 32 degrees C, coupled to a shift to 14 to 18 degrees C, led to the rapid induction of type 1 ice nuclei (i.e., ice nuclei active at temperatures warmer than -5 degrees C). Induction was most pronounced in stationary-phase cells that were grown with sorbitol as the carbon source and cooled rapidly, and under optimal conditions, the expression of type 1 ice nuclei increased from < 1 per 10(7) cells (i.e., not detectable) to 1 in every cell in 2 to 3 h. The induction was blocked by protein and RNA synthesis inhibitors, indicative of new gene expression. Pulse-labeling of nongrowing cultures with [35S]methionine after a shift to a low temperature demonstrated that the synthesis of a new set of "low-temperature" proteins was induced. Induced ice nuclei were stable at a low temperature, with no loss in activity at 4 degrees C after 8 days, but after a shift back to 32 degrees C, type 1 ice nuclei completely disappeared, with a half-life of approximately 1 h. Repeated cycles of low-temperature induction and high-temperature turnover of these ice nuclei could be demonstrated with the same nongrowing cells. Not all P. syringae strains from tomato or other plants were fully induced under the same culture conditions as strain T1, but all showed increased expression of type 1 ice nuclei after the shift to the low temperature. In support of this view, analysis of the published DNA sequence preceding the translational start site of the inaZ gene (R. L. Green and G. Warren, Nature [London] 317:645-648, 1985) suggests the presence of a gearbox-type promoter (M. Vincente, S. R. Kushner, T. Garrido, and M. Aldea, Mol. Microbiol. 5:2085-2091, 1991).
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PMID:High-level expression of ice nuclei in a Pseudomonas syringae strain is induced by nutrient limitation and low temperature. 832 Feb 22

Iron starvation induces the synthesis of two high molecular weight proteins (HMWP1 and 2) in Yersinia. The presence of the irp2 gene coding for the HMWP2 was investigated in 170 Yersinia strains. This gene was absent from all avirulent or weakly pathogenic species and was restricted to highly pathogenic strains. One hundred percent of the potentially highly pathogenic Yersinia enterocolitica biotype 1B harbored irp2 but surprisingly, 70.4% of the Yersinia pseudotuberculosis tested lacked the gene. Only serotypes I and III of Y. pseudotuberculosis harbored the locus, however, synthesis of HMWPs was detected uniquely in the former. In Yersinia pestis, overall 55.3% of the strains tested had the gene, with an uneven distribution among Orientalis (65.2%), Antiqua (66.6%) and Medievalis (0%) geographic variants. Except for one Y. pestis strain, the irp2 restriction profiles were identical for all strains of Y. pestis and Y. pseudotuberculosis tested. All Y. enterocolitica 1B displayed the same irp2 pattern, different from that of the other two species. In vitro spontaneous deletion of irp2 was not obtained in Y. enterocolitica 1B but was observed in both Y. pseudotuberculosis and Y. pestis. Repeated subcultures of Y. pestis increased progressively the proportion of irp2-deleted colonies, yielding an almost pure irp2-deleted strain after 16 subcultures. A clear correlation was established between the presence of irp2 and the level of virulence of Y. pseudotuberculosis and Y. pestis.
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PMID:Chromosomal irp2 gene in Yersinia: distribution, expression, deletion and impact on virulence. 832 Nov 19

The virulence region of the wild-type plasmid pSDL2 contained in Salmonella dublin is highly conserved among plasmids from several nontyphoid Salmonella serotypes and is essential for the development of systemic infection in BALB/c mice. Polyclonal antibodies against three proteins (SpvA, -B, and -C) expressed from a 4.1-kb EcoRI subclone of the plasmid virulence region were generated. These antibodies were used to detect expression of the Spv proteins when S. dublin was grown in vitro under stress-inducing conditions, such as nutrient deprivation and increased temperature, that the bacteria may encounter during the course of infection within the host. Glucose starvation resulted in expression of all three proteins shortly after the lag phase. When the bacteria were grown to the late-log phase without glucose, heat shock strongly induced expression of SpvA but not SpvB or SpvC. The addition of 0.2% glucose to the medium resulted in loss of expression of the proteins until the late-log to stationary phase. Iron limitation or lowered pH induced expression of the proteins during exponential growth even in the presence of glucose. Insertion mutations into the positive regulator gene spvR upstream from spvABC and insertions into spvA and spvC resulted in loss of expression of SpvA, -B, and -C, suggesting a complex regulation of expression. These studies define a variety of environmental conditions that induce expression of the Spv virulence proteins from the wild-type plasmid pSDL2 in S. dublin in vitro.
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PMID:Stress induction of the virulence proteins (SpvA, -B, and -C) from native plasmid pSDL2 of Salmonella dublin. 838 Jul 98


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