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Starvation Response (starvation + response)
Selected AbstractsMolecular analysis of the phosphorus starvation response in Trichodesmium spp.ENVIRONMENTAL MICROBIOLOGY, Issue 9 2009Elizabeth D. Orchard Summary The marine diazotroph Trichodesmium is a major contributor to primary production and nitrogen fixation in the tropical and subtropical oceans. These regions are often characterized by low phosphorus (P) concentrations, and P starvation of Trichodesmium could limit growth, and potentially constrain nitrogen fixation. To better understand how this genus responds to P starvation we examined four genes involved in P acquisition: two copies of a high-affinity phosphate binding protein (pstS and sphX) and two putative alkaline phosphatases (phoA and phoX). Sequence analysis of these genes among cultured species of Trichodesmium (T. tenue, T. erythraeum, T. thiebautii and T. spiralis) showed that they all are present and conserved within the genus. In T. erythraeum IMS101, the expression of sphX, phoA and phoX were sensitive to P supply whereas pstS was not. The induction of alkaline phosphatase activity corresponded with phoA and phoX expression, but enzyme activity persisted after the expression of these genes returned to basal levels. Additionally, nifH (nitrogenase reductase; involved in nitrogen fixation) expression was downregulated under P starvation conditions. These data highlight molecular level responses to low P and lay a foundation for better understanding the dynamics of Trichodesmium P physiology in low-P environments. [source] Peroxisome proliferator-activated receptor alpha and the ketogenic dietEPILEPSIA, Issue 2008Tim Cullingford Summary Peroxisome proliferator-activated receptor alpha (PPAR,) is a drug/fatty acid-activated trans cription factor involved in the starvation response, and is thus relevant to the ketogenic diet (KD). This article summarizes research indicating the role of PPAR, in central and peripheral nervous system function with particular reference to downstream targets relevant to anticonvulsant action. [source] Calorimetric investigations into the starvation response of Pseudomonas putida growing on phenol and glucoseJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2009Andreas Lißner Abstract Aims:, To investigate the stress response during nutrient deprivation, particularly with regard to the application of phenol as growth substrate of Pseudomonas putida with calorimetric measurements as a new method. Methods and Results:, The online and noninvasive measurement of the thermal power P0 permits the detection of microbial activity during the starvation period. While the results of the investigations with phenol reveal a significant loss of activity as a function of the temporal nutrient dosage, only a small loss of activity was detected by using glucose. Microbiological methods (colony forming units (CFU) and activity of catechol-2,3-dioxygenase) showed a loss of the enzyme activity at a constant CFU. The introduction of a simple decay parameter kD in the kinetic description of the growth process on phenol was sufficient for the successful kinetic modelling. Conclusions:, The combination of calorimetric measurements and the determination of the enzymatic activity proved the loss of activity of Ps. putida during the deprivation of the substrate phenol. Significance and Impact of the study:, The initial heat power (P0) proves to be a suitable parameter for the characterization of the physiological state of the culture and can be used for the regulation of nutrient supply in biotechnological process development. [source] GeneChip® expression analysis of the iron starvation response in Pseudomonas aeruginosa: identification of novel pyoverdine biosynthesis genesMOLECULAR MICROBIOLOGY, Issue 5 2002Urs A. Ochsner Summary Upon iron restriction, the opportunistic pathogen Pseudomonas aeruginosa produces various virulence factors, including siderophores, exotoxin, proteases and haemolysin. The ferric uptake regulator (Fur) plays a central role in this response and also controls other regulatory genes, such as pvdS, which encodes an alternative sigma factor. This circuit leads to a hierarchical cascade of direct and indirect iron regulation. We used the GeneChip® to analyse the global gene expression profiles in response to iron. In iron-starved cells, the expression of 118 genes was increased at least fivefold compared with that in iron-replete cells, whereas the expression of 87 genes was decreased at least fivefold. The GeneChip® data correlated well with results obtained using individual lacZ gene fusions. Strong iron regulation was observed for previously identified genes involved in biosynthesis or uptake of the siderophores pyoverdine and pyochelin, utilization of heterologous siderophores and haem and ferrous iron transport. A low-iron milieu led to increased expression of the genes encoding TonB, alkaline protease, PrpL protease, exotoxin A, as well as fumarase C, Mn-dependent superoxide dismutase SodA, a ferredoxin and ferredoxin reductase and several oxidoreductases and dehydrogenases. Iron-controlled regulatory genes included seven alternative sigma factors and five other transcriptional regulators. Roughly 20% of the iron-regulated genes encoded proteins of unknown function and lacked any conclusive homologies. Under low-iron conditions, expression of 26 genes or operons was reduced in a ,pvdS mutant compared with wild type, including numerous novel pyoverdine biosynthetic genes. The GeneChip® proved to be a very useful tool for rapid gene expression analysis and identification of novel genes controlled by Fur or PvdS. [source] Crystal structure of Mycobacterium tuberculosis LrpA, a leucine-responsive global regulator associated with starvation responsePROTEIN SCIENCE, Issue 1 2008Manchi C.M. Reddy Abstract The bacterial leucine-responsive regulatory protein (Lrp) is a global transcriptional regulator that controls the expression of many genes during starvation and the transition to stationary phase. The Mycobacterium tuberculosis gene Rv3291c encodes a 150-amino acid protein (designated here as Mtb LrpA) with homology with Escherichia coli Lrp. The crystal structure of the native form of Mtb LrpA was solved at 2.1 Å. The Mtb LrpA structure shows an N-terminal DNA-binding domain with a helix-turn-helix (HTH) motif, and a C-terminal regulatory domain. In comparison to the complex of E. coli AsnC with asparagine, the effector-binding pocket (including loop 100,106) in LrpA appears to be largely preserved, with hydrophobic substitutions consistent with its specificity for leucine. The effector-binding pocket is formed at the interface between adjacent dimers, with an opening to the core of the octamer as in AsnC, and an additional substrate-access channel opening to the outer surface of the octamer. Using electrophoretic mobility shift assays, purified Mtb LrpA protein was shown to form a protein,DNA complex with the lat promoter, demonstrating that the lat operon is a direct target of LrpA. Using computational analysis, a putative motif is identified in this region that is also present upstream of other operons differentially regulated under starvation. This study provides insights into the potential role of LrpA as a global regulator in the transition of M. tuberculosis to a persistent state. [source] Physiological adaptation of Corynebacterium glutamicum to benzoate as alternative carbon source , a membrane proteome-centric viewPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 14 2009Ute Haußmann Abstract The ability of microorganisms to assimilate aromatic substances as alternative carbon sources is the basis of biodegradation of natural as well as industrial aromatic compounds. In this study, Corynebacterium glutamicum was grown on benzoate as sole carbon and energy source. To extend the scarce knowledge about physiological adaptation processes occurring in this cell compartment, the membrane proteome was investigated under quantitative and qualitative aspects by applying shotgun proteomics to reach a comprehensive survey. Membrane proteins were relatively quantified using an internal standard metabolically labeled with 15N. Altogether, 40 proteins were found to change their abundance during growth on benzoate in comparison to glucose. A global adaptation was observed in the membrane of benzoate-grown cells, characterized by increased abundance of proteins of the respiratory chain, by a starvation response, and by changes in sulfur metabolism involving the regulator McbR. Additional to the relative quantification, stable isotope-labeled synthetic peptides were used for the absolute quantification of the two benzoate transporters of C. glutamicum, BenK and BenE. It was found that both transporters were expressed during growth on benzoate, suggesting that both contribute substantially to benzoate uptake. [source] The glucose and nitrogen starvation response of Bacillus licheniformisPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 3 2007Birgit Voigt Abstract The glucose and nitrogen starvation stimulons of Bacillus licheniformis were determined by transcriptome and proteome analyses. Under both starvation conditions, the main response of B. licheniformis was a switch to the usage of alternative nutrient sources. This was indicated by an induction of genes involved in the metabolism of C-2 substrates during glucose limitation. In addition, B. licheniformis seems to be using other organic substances like amino acids and lipids as carbon sources when subjected to glucose starvation. This observation is supported by the induction of a high number of genes coding for proteins involved in amino acid and lipid degradation. During nitrogen starvation, genes for several proteases and peptidases involved in nitrate and nitrite assimilation were induced, which enables this bacterium to recruit nitrogen from alternative sources. Both starvation conditions led to a down-regulation of transcription of most vegetative genes, which was subsequently reflected by a reduced synthesis of the corresponding proteins. A selected set of genes was induced by both starvation conditions. Among them were yvyD, citA and the putative methylcitrate shunt genes mmgD, mmgE and yqiQ. However, both starvation conditions did not induce a general SigmaB-dependent stress response. [source] Phosphate sensing in higher plantsPHYSIOLOGIA PLANTARUM, Issue 1 2002Steffen Abel Phosphate (Pi) plays a central role as reactant and effector molecule in plant cell metabolism. However, Pi is the least accessible macronutrient in many ecosystems and its low availability often limits plant growth. Plants have evolved an array of molecular and morphological adaptations to cope with Pi limitation, which include dramatic changes in gene expression and root development to facilitate Pi acquisition and recycling. Although physiological responses to Pi starvation have been increasingly studied and understood, the initial molecular events that monitor and transmit information on external and internal Pi status remain to be elucidated in plants. This review summarizes molecular and developmental Pi starvation responses of higher plants and the evidence for coordinated regulation of gene expression, followed by a discussion of the potential involvement of plant hormones in Pi sensing and of molecular genetic approaches to elucidate plant signalling of low Pi availability. Complementary genetic strategies in Arabidopsis thaliana have been developed that are expected to identify components of plant signal transduction pathways involved in Pi sensing. Innovative screening methods utilize reporter gene constructs, conditional growth on organophosphates and the inhibitory properties of the Pi analogue phosphite, which hold the promise for significant advances in our understanding of the complex mechanisms by which plants regulate Pi-starvation responses. [source] From genomics via proteomics to cellular physiology of the Gram-positive model organism Bacillus subtilisCELLULAR MICROBIOLOGY, Issue 8 2005Uwe Völker Summary Complementing proteomic technologies enable an unbiased view of cellular adaptation and thus may provide a new understanding of cellular physiology, particularly for microorganisms because a major fraction of their proteome is accessible to currently available technology. In combination with transcriptional profiling expression proteomics provides access to interesting candidate genes and proteins that will then need to be validated and supplemented by traditional physiological, biochemical and genetic approaches. After a description of the current status of the technology, we display the potential of microbial proteomics using the model organism Bacillus subtilis as example. Starting from a proteome map a proteomic view of the metabolism will be provided. Furthermore, we demonstrate that proteomics complemented by transcriptomics is also useful for the study of stress and starvation responses and that integration of these data will lead to a comprehensive understanding of the adaptational network of bacterial cells. Thus, B. subtilis constitutes a highly versatile and tractable model organism for the study of generic stress responses and the expertise that has been gained can easily be transferred to the study of the cellular physiology of related Gram-positive pathogens and their pathophysiology. [source] | |||||||||||||