scholarly journals Differential Regulation of High-Affinity Phosphate Transport Systems of Mycobacterium smegmatis: Identification of PhnF, a Repressor of the phnDCE Operon

2007 ◽  
Vol 190 (4) ◽  
pp. 1335-1343 ◽  
Author(s):  
Susanne Gebhard ◽  
Gregory M. Cook
Keyword(s):  
Mycobacterium Smegmatis ◽  
Constitutive Expression ◽  
Phosphate Transport ◽  
Phosphate Limitation ◽  
Transport Systems ◽  
New Members ◽  
High Affinity ◽  
Expression Of Genes ◽  
Two Component ◽  
Genes Encoding

ABSTRACT The uptake of phosphate into the cell via high-affinity, phosphate-specific transport systems has been studied with several species of mycobacteria. All of these species have been shown to contain several copies of such transport systems, which are synthesized in response to phosphate limitation. However, the mechanisms leading to the expression of the genes encoding these transporters have not been studied. This study reports on the investigation of the regulation of the pstSCAB and the phnDCE operons of Mycobacterium smegmatis. The phn locus contains an additional gene, phnF, encoding a GntR-like transcriptional regulator. Expression analyses of a phnF deletion mutant demonstrated that PhnF acts as a repressor of the phnDCE operon but does not affect the expression of pstSCAB. The deletion of pstS, which is thought to cause the constitutive expression of genes regulated by the two-component system SenX3-RegX3, led to the constitutive expression of the transcriptional fusions pstS-lacZ, phnD-lacZ, and phnF-lacZ, suggesting that phnDCE and phnF are conceivably new members of the SenX3-RegX3 regulon of M. smegmatis. Two presumptive binding sites for PhnF in the intergenic region between phnD and phnF were identified and shown to be required for the repression of phnD and phnF, respectively. We propose a model in which the transcription of pstSCAB is controlled by the two-component SenX3-RegX3 system, while phnDCE and phnF are subject to dual control by SenX3-RegX3 and PhnF.

scholarly journals The Phn system of Mycobacterium smegmatis: a second high-affinity ABC-transporter for phosphate

Microbiology ◽  
2006 ◽  
Vol 152 (11) ◽  
pp. 3453-3465 ◽  
Author(s):  
Susanne Gebhard ◽  
Sieu L. Tran ◽  
Gregory M. Cook
Keyword(s):  
Transport System ◽  
Mycobacterium Smegmatis ◽  
Single Copy ◽  
Phosphate Transport ◽  
Phosphate Limitation ◽  
Wild Type ◽  
High Affinity ◽  
Genes Encoding ◽  
Limiting Nutrient ◽  
In The Wild

Uptake of inorganic phosphate, an essential but often limiting nutrient, in bacteria is usually accomplished by the high-affinity ABC-transport system Pst. Pathogenic species of mycobacteria contain several copies of the genes encoding the Pst system (pstSCAB), and two of the encoded proteins, PstS1 and PstS2, have been shown to be virulence factors in Mycobacterium tuberculosis. The fast-growing Mycobacterium smegmatis contains only a single copy of the pst operon. This study reports the biochemical and molecular characterization of a second high-affinity phosphate transport system, designated Phn. The Phn system is encoded by a three-gene operon that constitutes the components of a putative ABC-type phosphonate/phosphate transport system. Expression studies using phnD– and pstS–lacZ transcriptional fusions showed that both operons were induced when the culture entered phosphate limitation, indicating a role for both systems in phosphate uptake at low extracellular concentrations. Deletion mutants in either phnD or pstS failed to grow in minimal medium with a 10 mM phosphate concentration, while the isogenic wild-type strain mc2155 grew at micromolar phosphate concentrations. Analysis of the kinetics of phosphate transport in the wild-type and mutant strains led to the proposal that the Phn and Pst systems are both high-affinity phosphate transporters with similar affinities for phosphate (i.e. apparent K m values between 40 and 90 μM Pi). The Phn system of M. smegmatis appears to be unique in that, unlike previously identified Phn systems, it does not recognize phosphonates or phosphite as substrates.

Regulation of cyanobacterial CO2-concentrating mechanisms through transcriptional induction of high-affinity Ci-transport systems

2005 ◽  
Vol 83 (7) ◽  
pp. 698-710 ◽  
Author(s):  
Fiona J Woodger ◽  
Murray R Badger ◽  
G Dean Price
Keyword(s):  
Carbon Fixation ◽  
Transport Systems ◽  
Transcriptional Level ◽  
Transcriptional Responses ◽  
High Affinity ◽  
Genetic Components ◽  
Expression Of Genes ◽  
Genes Encoding ◽  
Synechococcus Pcc7942 ◽  
Sense And Respond

Approximately 50% of global CO2-based productivity is now attributed to the activity of phytoplankton, including ocean-dwelling cyanobacteria. In response to inherent restrictions on the rate of CO2 supply in the aquatic environment, cyanobacteria have evolved a very efficient means of capturing inorganic carbon (Ci), as either CO2 or HCO3–. for photosynthetic carbon fixation. This capturing mechanism, known as a CO2-concentrating mechanism (CCM), involves the operation of active CO2 and HCO3– transporters and results in the concentration of CO2 around RuBisCO, in a unique microcompartment called the carboxysome. The CCM exhibits two basic physiological states: a constitutive, low-affinity state; and a high-affinity state, which is induced in response to Ci limitation. Many of the genetic components of the CCM, including genes encoding Ci transporters, have been identified. It is apparent that the expression of genes encoding the inducible, high-affinity Ci transporters is particularly sensitive to Ci availability, and we are now interested in defining how cyanobacterial cells sense and respond to Ci limitation at the transcriptional level. Current theories include direct sensing of external Ci; sensing of internal Ci-pool fluctuations; and detection of changes in photorespiratory intermediates, carbon metabolites, or redox potential. At present, there is no consensual view. We have investigated the physiological and transcriptional responses of CCM mutants and wildtype strains to pharmacological treatments and various light, O2, and Ci regimes. Our data suggest that perception of Ci limitation by a cyanobacterial cell is either directly or indirectly related to the size of the internal Ci pool within the cell, in an oxygen-dependent manner.Key words: CO2-concentrating mechanisms, CO2 sensing, Ci transporters, Synechococcus PCC7942.

Effect of pH on Na(+)-dependent phosphate transport in renal outer cortical and outer medullary BBMV

1990 ◽  
Vol 258 (2) ◽  
pp. F356-F363 ◽  
Author(s):  
G. A. Quamme
Keyword(s):  
Brush Border ◽  
Sodium Phosphate ◽  
Membrane Vesicles ◽  
Phosphate Transport ◽  
Transport Systems ◽  
Outer Cortex ◽  
Ph Change ◽  
High Affinity ◽  
Medullary Tissue ◽  
Maximum Uptake Rate

The influence of pH on sodium-phosphate cotransport was determined in brush-border membrane vesicles (BBMV) isolated from outer cortical and outer medullary tissue of porcine kidneys. Two transport systems are apparent in outer cortical brush-border vesicles, and one process is apparent in outer medullary vesicles at all pH values. The apparent maximum uptake rate (Vmax) of the low-affinity system in outer cortex vesicles decreased from 8.3 +/- 1.7 to 3.2 +/- 0.05 nmol.mg protein-1.min-1 with pH change of 8.0 to 6.0, and the high-affinity process changed from 1.3 +/- 0.2 to 0.1 +/- 0.01 nmol.mg protein-1.min-1. The respective affinity values (Km) also decreased 5.5 +/- 0.9 to 0.6 +/- 0.01 mM and 0.08 +/- 0.005 to 0.01 +/- 0.005 mM, respectively, with acidification. In outer medullary vesicles a decrease in pH diminished the apparent Km, 0.28 +/- 0.03 to 0.02 +/- 0.003 mM, and mean Vmax from 3.0 +/- 0.07 to 0.5 +/- 0.1 nmol.mg protein-1.min-1. The mean KNaD values were 22.1 +/- 4.2 mM in outer cortical vesicles (low-affinity system) and 58.7 +/- 7.2 mM in outer medullary vesicles (high-affinity system) and were not altered by pH, suggesting that H+ does not affect the sodium interactive site. The data suggest that the vesicles prepared from outer cortical and outer medullary tissue possess distinctive sodium-phosphate transporters that are sensitive to external H+ concentrations.

scholarly journals Constitutive expression of genes encoding notch receptors and ligands in developing lymphocytes, nTreg cells and dendritic cells in the human thymus

2016 ◽  
Vol 6 ◽  
pp. 15-20 ◽  
Author(s):  
Luciana Bento-de-Souza ◽  
Jefferson R. Victor ◽  
Luiz C. Bento-de-Souza ◽  
Magaly Arrais-Santos ◽  
Andréia C. Rangel-Santos ◽  
...  
Keyword(s):  
Dendritic Cells ◽  
Constitutive Expression ◽  
Human Thymus ◽  
Notch Receptors ◽  
Expression Of Genes ◽  
Genes Encoding

scholarly journals Hexokinase Regulates Kinetics of Glucose Transport and Expression of Genes Encoding Hexose Transporters inSaccharomyces cerevisiae

2000 ◽  
Vol 182 (23) ◽  
pp. 6815-6818 ◽  
Author(s):  
Thomas Petit ◽  
Jasper A. Diderich ◽  
Arthur L. Kruckeberg ◽  
Carlos Gancedo ◽  
Karel Van Dam
Keyword(s):  
Glucose Transport ◽  
Mrna Levels ◽  
High Affinity ◽  
Expression Of Genes ◽  
Hexose Transporters ◽  
Genes Encoding ◽  
High Concentrations ◽  
Kinetics Of ◽  
Very High ◽  
Null Strain

ABSTRACT Glucose transport kinetics and mRNA levels of different glucose transporters were determined in Saccharomyces cerevisiaestrains expressing different sugar kinases. During exponential growth on glucose, a hxk2 null strain exhibited high-affinity hexose transport associated with an elevated transcription of the genesHXT2 and HXT7, encoding high-affinity transporters, and a diminished expression of the HXT1 andHXT3 genes, encoding low-affinity transporters. Deletion ofHXT7 revealed that the high-affinity component is mostly due to HXT7; however, a previously unidentified very-high-affinity component (Km = 0.19 mM) appeared to be due to other factors. Expression of genes encoding hexokinases from Schizosaccharomyces pombe orYarrowia lipolytica in a hxk1 hxk2 glk1 strain prevented derepression of the high-affinity transport system at high concentrations of glucose.

scholarly journals Vibrio Iron Transport: Evolutionary Adaptation to Life in Multiple Environments

2015 ◽  
Vol 80 (1) ◽  
pp. 69-90 ◽  
Author(s):  
Shelley M. Payne ◽  
Alexandra R. Mey ◽  
Elizabeth E. Wyckoff
Keyword(s):  
Regulatory Networks ◽  
Iron Transport ◽  
Horizontal Transmission ◽  
Essential Element ◽  
Transport Systems ◽  
Iron Binding ◽  
Content Type ◽  
High Affinity ◽  
Wide Range ◽  
Genes Encoding

SUMMARYIron is an essential element forVibriospp., but the acquisition of iron is complicated by its tendency to form insoluble ferric complexes in nature and its association with high-affinity iron-binding proteins in the host. Vibrios occupy a variety of different niches, and each of these niches presents particular challenges for acquiring sufficient iron.Vibriospecies have evolved a wide array of iron transport systems that allow the bacteria to compete for this essential element in each of its habitats. These systems include the secretion and uptake of high-affinity iron-binding compounds (siderophores) as well as transport systems for iron bound to host complexes. Transporters for ferric and ferrous iron not complexed to siderophores are also common toVibriospecies. Some of the genes encoding these systems show evidence of horizontal transmission, and the ability to acquire and incorporate additional iron transport systems may have allowedVibriospecies to more rapidly adapt to new environmental niches. While too little iron prevents growth of the bacteria, too much can be lethal. The appropriate balance is maintained in vibrios through complex regulatory networks involving transcriptional repressors and activators and small RNAs (sRNAs) that act posttranscriptionally. Examination of the number and variety of iron transport systems found inVibriospp. offers insights into how this group of bacteria has adapted to such a wide range of habitats.

scholarly journals Characterization of Two Inducible Phosphate Transport Systems in Rhizobium tropici

2000 ◽  
Vol 66 (1) ◽  
pp. 15-22 ◽  
Author(s):  
Lina M. Botero ◽  
Thamir S. Al-Niemi ◽  
Timothy R. McDermott
Keyword(s):  
Transport System ◽  
Response Regulator ◽  
Insertion Site ◽  
Dry Weight ◽  
Type Systems ◽  
Phosphate Transport ◽  
Transport Systems ◽  
Atpase Inhibitor ◽  
Rhizobium Tropici ◽  
High Affinity

ABSTRACT Rhizobium tropici forms nitrogen-fixing nodules on the roots of the common bean (Phaseolus vulgaris). Like other legume-Rhizobium symbioses, the bean-R. tropiciassociation is sensitive to the availability of phosphate (Pi). To better understand phosphorus movement between the bacteroid and the host plant, Pi transport was characterized in R. tropici. We observed two Pitransport systems, a high-affinity system and a low-affinity system. To facilitate the study of these transport systems, a Tn5B22 transposon mutant lacking expression of the high-affinity transport system was isolated and used to characterize the low-affinity transport system in the absence of the high-affinity system. TheKm and V max values for the low-affinity system were estimated to be 34 ± 3 μM Pi and 118 ± 8 nmol of Pi · min−1 · mg (dry weight) of cells−1, respectively, and the Km andV max values for the high-affinity system were 0.45 ± 0.01 μM Pi and 86 ± 5 nmol of Pi · min−1 · mg (dry weight) of cells−1, respectively. Both systems were inducible by Pi starvation and were also shock sensitive, which indicated that there was a periplasmic binding-protein component. Neither transport system appeared to be sensitive to the proton motive force dissipator carbonyl cyanide m-chlorophenylhydrazone, but Pi transport through both systems was eliminated by the ATPase inhibitor N,N′-dicyclohexylcarbodiimide; the Pi transport rate was correlated with the intracellular ATP concentration. Also, Pi movement through both systems appeared to be unidirectional, as no efflux or exchange was observed with either the wild-type strain or the mutant. These properties suggest that both Pi transport systems are ABC type systems. Analysis of the transposon insertion site revealed that the interrupted gene exhibited a high level of homology withkdpE, which in several bacteria encodes a cytoplasmic response regulator that governs responses to low potassium contents and/or changes in medium osmolarity.

scholarly journals A genome-wide analysis of Escherichia coli responses to fosfomycin using TraDIS-Xpress reveals novel roles for phosphonate degradation and phosphate transport systems

2020 ◽  
Vol 75 (11) ◽  
pp. 3144-3151 ◽  
Author(s):  
A Keith Turner ◽  
Muhammad Yasir ◽  
Sarah Bastkowski ◽  
Andrea Telatin ◽  
Andrew J Page ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Sugar Metabolism ◽  
Phosphate Transport ◽  
Transport Systems ◽  
Loss Of Function ◽  
Genome Wide Analysis ◽  
Genome Wide ◽  
A Genome ◽  
Genes Encoding ◽  
The Impact

Abstract Background Fosfomycin is an antibiotic that has seen a revival in use due to its unique mechanism of action and efficacy against isolates resistant to many other antibiotics. In Escherichia coli, fosfomycin often selects for loss-of-function mutations within the genes encoding the sugar importers, GlpT and UhpT. There has, however, not been a genome-wide analysis of the basis for fosfomycin susceptibility reported to date. Methods Here we used TraDIS-Xpress, a high-density transposon mutagenesis approach, to assay the role of all genes in E. coli involved in fosfomycin susceptibility. Results The data confirmed known fosfomycin susceptibility mechanisms and identified new ones. The assay was able to identify domains within proteins of importance and revealed essential genes with roles in fosfomycin susceptibility based on expression changes. Novel mechanisms of fosfomycin susceptibility that were identified included those involved in glucose metabolism and phosphonate catabolism (phnC-M), and the phosphate importer, PstSACB. The impact of these genes on fosfomycin susceptibility was validated by measuring the susceptibility of defined inactivation mutants. Conclusions This work reveals a wider set of genes that contribute to fosfomycin susceptibility, including core sugar metabolism genes and two systems involved in phosphate uptake and metabolism previously unrecognized as having a role in fosfomycin susceptibility.

scholarly journals Pseudomonas aeruginosa Uses Multiple Pathways To Acquire Iron during Chronic Infection in Cystic Fibrosis Lungs

2013 ◽  
Vol 81 (8) ◽  
pp. 2697-2704 ◽  
Author(s):  
Anna F. Konings ◽  
Lois W. Martin ◽  
Katrina J. Sharples ◽  
Louise F. Roddam ◽  
Roger Latham ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Iron Uptake ◽  
Transport Systems ◽  
Ferrous Ions ◽  
Content Type ◽  
Bacterial Physiology ◽  
Expression Of Genes ◽  
Genes Encoding ◽  
Uptake Mechanisms

ABSTRACTPseudomonas aeruginosachronically infects the lungs of more than 80% of adult patients with cystic fibrosis (CF) and is a major contributor to the progression of disease pathology.P. aeruginosarequires iron for growth and has multiple iron uptake systems that have been studied in bacteria grown in laboratory culture. The purpose of this research was to determine which of these are active during infection in CF. RNA was extracted from 149 sputum samples obtained from 23 CF patients. Reverse transcription–quantitative real-time PCR (RT-qPCR) was used to measure the expression ofP. aeruginosagenes encoding transport systems for the siderophores pyoverdine and pyochelin, for heme, and for ferrous ions. Expression ofP. aeruginosagenes could be quantified in 89% of the sputum samples. Expression of genes associated with siderophore-mediated iron uptake was detected in most samples but was at low levels in some samples, indicating that other iron uptake mechanisms are active. Expression of genes encoding heme transport systems was also detected in most samples, indicating that heme uptake occurs during infection in CF.feoBexpression was detected in all sputum samples, implying an important role for ferrous ion uptake byP. aeruginosain CF. Our data show that multipleP. aeruginosairon uptake mechanisms are active in chronic CF infection and that RT-qPCR of RNA extracted from sputum provides a powerful tool for investigating bacterial physiology during infection in CF.

Sign in / Sign up

Export Citation Format

Share Document