Sunday, February 22, 2015

 

 



Soy un nuevo usuario

Olvidé mi contraseña

Entrada usuarios

Lógica Matemáticas Astronomía y Astrofísica Física Química Ciencias de la Vida
Ciencias de la Tierra y Espacio Ciencias Agrarias Ciencias Médicas Ciencias Tecnológicas Antropología Demografía
Ciencias Económicas Geografía Historia Ciencias Jurídicas y Derecho Lingüística Pedagogía
Ciencia Política Psicología Artes y Letras Sociología Ética Filosofía
 

rss_1.0 Recursos de colección

PubMed Central (PMC3 - NLM DTD) (2,750,487 recursos)
Archive of life sciences journal literature at the U.S. National Institutes of Health (NIH), developed and managed by NIH's National Center for Biotechnology Information (NCBI) in the National Library of Medicine (NLM).

Journal of Bacteriology

Mostrando recursos 1 - 20 de 95,065

1. RecO and RecR Are Necessary for RecA Loading in Response to DNA Damage and Replication Fork Stress - Lenhart, Justin S.; Brandes, Eileen R.; Schroeder, Jeremy W.; Sorenson, Roderick J.; Showalter, Hollis D.; Simmons, Lyle A.
RecA is central to maintaining genome integrity in bacterial cells. Despite the near-ubiquitous conservation of RecA in eubacteria, the pathways that facilitate RecA loading and repair center assembly have remained poorly understood in Bacillus subtilis. Here, we show that RecA rapidly colocalizes with the DNA polymerase complex (replisome) immediately following DNA damage or damage-independent replication fork arrest. In Escherichia coli, the RecFOR and RecBCD pathways serve to load RecA and the choice between these two pathways depends on the type of damage under repair. We found in B. subtilis that the rapid localization of RecA to repair centers is strictly...

2. Physiological and Proteomic Analysis of Escherichia coli Iron-Limited Chemostat Growth - Folsom, James Patrick; Parker, Albert E.; Carlson, Ross P.
Iron bioavailability is a major limiter of bacterial growth in mammalian host tissue and thus represents an important area of study. Escherichia coli K-12 metabolism was studied at four levels of iron limitation in chemostats using physiological and proteomic analyses. The data documented an E. coli acclimation gradient where progressively more severe iron scarcity resulted in a larger percentage of substrate carbon being directed into an overflow metabolism accompanied by a decrease in biomass yield on glucose. Acetate was the primary secreted organic by-product for moderate levels of iron limitation, but as stress increased, the metabolism shifted to secrete primarily...

3. Genetic Requirements for Sensitivity of Bacteriophage T7 to Dideoxythymidine - Tran, Ngoc Q.; Tabor, Stanley; Richardson, Charles C.
We previously reported that the presence of dideoxythymidine (ddT) in the growth medium selectively inhibits the ability of bacteriophage T7 to infect Escherichia coli by inhibiting phage DNA synthese (N. Q. Tran, L. F. Rezende, U. Qimron, C. C. Richardson, and S. Tabor, Proc. Natl. Acad. Sci. U. S. A. 105:9373–9378, 2008, doi:10.1073/pnas.0804164105). In the presence of T7 gene 1.7 protein, ddT is taken up into the E. coli cell and converted to ddTTP. ddTTP is incorporated into DNA as ddTMP by the T7 DNA polymerase, resulting in chain termination. We have identified the pathway by which exogenous ddT is...

4. Dynamics of Expression and Maturation of the Type III Secretion System of Enteropathogenic Escherichia coli - Yerushalmi, Gal; Litvak, Yael; Gur-Arie, Lihi; Rosenshine, Ilan
Enteropathogenic Escherichia coli (EPEC) is a major cause of food poisoning, leading to significant morbidity and mortality. EPEC virulence is dependent on a type III secretion system (T3SS), a molecular syringe employed by EPEC to inject effector proteins into host cells. The injected effector proteins subvert host cellular functions to the benefit of the infecting bacteria. The T3SS and related genes reside in several operons clustered in the locus of enterocyte effacement (LEE). We carried out simultaneous analysis of the expression dynamics of all the LEE promoters and the rate of maturation of the T3SS. The results showed that expression...

5. Identification of Regulatory Elements That Control Expression of the tbpBA Operon in Neisseria gonorrhoeae - Vélez Acevedo, Rosuany N.; Ronpirin, Chalinee; Kandler, Justin L.; Shafer, William M.; Cornelissen, Cynthia Nau
Iron is an essential nutrient for survival and establishment of infection by Neisseria gonorrhoeae. The neisserial transferrin binding proteins (Tbps) comprise a bipartite system for iron acquisition from human transferrin. TbpA is the TonB-dependent transporter that accomplishes iron internalization. TbpB is a surface-exposed lipoprotein that makes the iron uptake process more efficient. Previous studies have shown that the genes encoding these proteins are arranged in a bicistronic operon, with the tbpB gene located upstream of tbpA and separated from it by an inverted repeat. The operon is under the control of the ferric uptake regulator (Fur); however, promoter elements necessary...

6. Influence of the AgrC-AgrA Complex on the Response Time of Staphylococcus aureus Quorum Sensing - Srivastava, Sandeep K.; Rajasree, Kalagiri; Fasim, Aneesa; Arakere, Gayathri; Gopal, Balasubramanian
The Staphylococcus aureus agr quorum-sensing system plays a major role in the transition from the persistent to the virulent phenotype. S. aureus agr type I to IV strains are characterized by mutations in the sensor domain of the histidine kinase AgrC and differences in the sequences of the secreted autoinducing peptides (AIP). Here we demonstrate that interactions between the cytosolic domain of AgrC (AgrCCyto) and the response regulator domain of AgrA (AgrARR) dictate the spontaneity of the cellular response to AIP stimuli. The crystal structure of AgrCCyto provided a basis for a mechanistic model of AgrC-AgrA interactions. This model enabled an analysis...

7. Structural Features of the Pseudomonas fluorescens Biofilm Adhesin LapA Required for LapG-Dependent Cleavage, Biofilm Formation, and Cell Surface Localization - Boyd, Chelsea D.; Smith, T. Jarrod; El-Kirat-Chatel, Sofiane; Newell, Peter D.; Dufrêne, Yves F.; O'Toole, George A.
The localization of the LapA protein to the cell surface is a key step required by Pseudomonas fluorescens Pf0-1 to irreversibly attach to a surface and form a biofilm. LapA is a member of a diverse family of predicted bacterial adhesins, and although lacking a high degree of sequence similarity, family members do share common predicted domains. Here, using mutational analysis, we determine the significance of each domain feature of LapA in relation to its export and localization to the cell surface and function in biofilm formation. Our previous work showed that the N terminus of LapA is required for...

8. Localization of the Outer Membrane Protein OmpA2 in Caulobacter crescentus Depends on the Position of the Gene in the Chromosome - Ginez, Luis David; Osorio, Aurora; Poggio, Sebastian
The outer membrane of Gram-negative bacteria is an essential structure involved in nutrient uptake, protection against harmful substances, and cell growth. Different proteins keep the outer membrane from blebbing out by simultaneously interacting with it and with the cell wall. These proteins have been mainly studied in enterobacteria, where OmpA and the Braun and Pal lipoproteins stabilize the outer membrane. Some degree of functional redundancy exists between these proteins, since none of them is essential but the absence of two of them results in a severe phenotype. Caulobacter crescentus has a different strategy to maintain its outer membrane, since it...

9. Control of Natural Transformation in Salivarius Streptococci through Specific Degradation of σX by the MecA-ClpCP Protease Complex - Wahl, Astrid; Servais, Florence; Drucbert, Anne-Sophie; Foulon, Catherine; Fontaine, Laetitia; Hols, Pascal
Competence for natural DNA transformation is a tightly controlled developmental process in streptococci. In mutans and salivarius species, the abundance of the central competence regulator σX is regulated at two levels: transcriptional, by the ComRS signaling system via the σX/ComX/SigX-inducing peptide (XIP), and posttranscriptional, by the adaptor protein MecA and its associated Clp ATPase, ClpC. In this study, we further investigated the mechanism and function of the MecA-ClpC control system in the salivarius species Streptococcus thermophilus. Using in vitro approaches, we showed that MecA specifically interacts with both σX and ClpC, suggesting the formation of a ternary σX-MecA-ClpC complex. Moreover,...

10. β-Alanine Biosynthesis in Methanocaldococcus jannaschii - Wang, Yu; Xu, Huimin; White, Robert H.
One efficient approach to assigning function to unannotated genes is to establish the enzymes that are missing in known biosynthetic pathways. One group of such pathways is those involved in coenzyme biosynthesis. In the case of the methanogenic archaeon Methanocaldococcus jannaschii as well as most methanogens, none of the expected enzymes for the biosynthesis of the β-alanine and pantoic acid moieties required for coenzyme A are annotated. To identify the gene(s) for β-alanine biosynthesis, we have established the pathway for the formation of β-alanine in this organism after experimentally eliminating other known and proposed pathways to β-alanine from malonate semialdehyde,...

11. Nutrient-Regulated Proteolysis of MrpC Halts Expression of Genes Important for Commitment to Sporulation during Myxococcus xanthus Development - Rajagopalan, Ramya; Kroos, Lee
Starved Myxococcus xanthus cells glide to aggregation centers and form fruiting bodies in which rod-shaped cells differentiate into ovoid spores. Commitment to development was investigated by adding nutrients at specific times after starvation and determining whether development halted or proceeded. At 24 h poststarvation, some rod-shaped cells were committed to subsequent shape change and to becoming sonication-resistant spores, but nutrients caused partial disaggregation of fruiting bodies. By 30 h poststarvation, 10-fold more cells were committed to becoming sonication-resistant spores, and compact fruiting bodies persisted after nutrient addition. During the critical period of commitment around 24 to 30 h poststarvation, the...

12. Control of Gene Expression at a Bacterial Leader RNA, the agn43 Gene Encoding Outer Membrane Protein Ag43 of Escherichia coli - Wallecha, Anu; Oreh, Heather; van der Woude, Marjan W.; deHaseth, Pieter L.
The family of agn alleles in Escherichia coli pathovars encodes autotransporters that have been implicated in biofilm formation, autoaggregation, and attachment to cells. The alleles all have long leader RNAs preceding the Ag43 translation initiation codon. Here we present an analysis of the agn43 leader RNA from E. coli K-12. We demonstrate the presence of a rho-independent transcription terminator just 28 bp upstream of the main translation start codon and show that it is functional in vitro. Our data indicate that an as-yet-unknown mechanism of antitermination of transcription must be operative in earlier phases of growth. However, as bacterial cell...

13. Intracellular Concentrations of 65 Species of Transcription Factors with Known Regulatory Functions in Escherichia coli - Ishihama, Akira; Kori, Ayako; Koshio, Etsuko; Yamada, Kayoko; Maeda, Hiroto; Shimada, Tomohiro; Makinoshima, Hideki; Iwata, Akira; Fujita, Nobuyuki
The expression pattern of the Escherichia coli genome is controlled in part by regulating the utilization of a limited number of RNA polymerases among a total of its approximately 4,600 genes. The distribution pattern of RNA polymerase changes from modulation of two types of protein-protein interactions: the interaction of core RNA polymerase with seven species of the sigma subunit for differential promoter recognition and the interaction of RNA polymerase holoenzyme with about 300 different species of transcription factors (TFs) with regulatory functions. We have been involved in the systematic search for the target promoters recognized by each sigma factor and...

14. The Pseudomonas aeruginosa Diguanylate Cyclase GcbA, a Homolog of P. fluorescens GcbA, Promotes Initial Attachment to Surfaces, but Not Biofilm Formation, via Regulation of Motility - Petrova, Olga E.; Cherny, Kathryn E.; Sauer, Karin
Cyclic di-GMP is a conserved signaling molecule regulating the transitions between motile and sessile modes of growth in a variety of bacterial species. Recent evidence suggests that Pseudomonas species harbor separate intracellular pools of c-di-GMP to control different phenotypic outputs associated with motility, attachment, and biofilm formation, with multiple diguanylate cyclases (DGCs) playing distinct roles in these processes, yet little is known about the potential conservation of functional DGCs across Pseudomonas species. In the present study, we demonstrate that the P. aeruginosa homolog of the P. fluorescens DGC GcbA involved in promoting biofilm formation via regulation of swimming motility likewise...

15. Identification and Characterization of a Novel Secreted Glycosidase with Multiple Glycosidase Activities in Streptococcus intermedius - Imaki, Hidenori; Tomoyasu, Toshifumi; Yamamoto, Naoki; Taue, Chiharu; Masuda, Sachiko; Takao, Ayuko; Maeda, Nobuko; Tabata, Atsushi; Whiley, Robert A.; Nagamune, Hideaki
Streptococcus intermedius is a known human pathogen and belongs to the anginosus group (S. anginosus, S. intermedius, and S. constellatus) of streptococci (AGS). We found a large open reading frame (6,708 bp) in the lac operon, and bioinformatic analysis suggested that this gene encodes a novel glycosidase that can exhibit β-d-galactosidase and N-acetyl-β-d-hexosaminidase activities. We, therefore, named this protein “multisubstrate glycosidase A” (MsgA). To test whether MsgA has these glycosidase activities, the msgA gene was disrupted in S. intermedius. The msgA-deficient mutant no longer showed cell- and supernatant-associated β-d-galactosidase, β-d-fucosidase, N-acetyl-β-d-glucosaminidase, and N-acetyl-β-d-galactosaminidase activities, and all phenotypes were complemented in...

16. Analysis of the Arabinose-5-Phosphate Isomerase of Bacteroides fragilis Provides Insight into Regulation of Single-Domain Arabinose Phosphate Isomerases - Cech, David; Wang, Pan Fen; Holler, Tod P.; Woodard, Ronald W.
Arabinose-5-phosphate isomerases (APIs) catalyze the interconversion of d-ribulose-5-phosphate and d-arabinose-5-phosphate, the first step in the biosynthesis of 3-deoxy-d-manno-octulosonic acid (Kdo), an essential component of the lipopolysaccharide in Gram-negative bacteria. Classical APIs, such as Escherichia coli KdsD, contain a sugar isomerase domain and a tandem cystathionine beta-synthase domain. Despite substantial effort, little is known about structure-function relationships in these APIs. We recently reported an API containing only a sugar isomerase domain. This protein, c3406 from E. coli CFT073, has no known physiological function. In this study, we investigated a putative single-domain API from the anaerobic Gram-negative bacterium Bacteroides fragilis. This putative...

17. Modification of Streptococcus mutans Cnm by PgfS Contributes to Adhesion, Endothelial Cell Invasion, and Virulence - Avilés-Reyes, Alejandro; Miller, James H.; Simpson-Haidaris, Patricia J.; Hagen, Fred K.; Abranches, Jacqueline; Lemos, José A.
Expression of the surface protein Cnm has been directly implicated in the ability of certain strains of Streptococcus mutans to bind to collagen and to invade human coronary artery endothelial cells (HCAEC) and in the killing of Galleria mellonella. Sequencing analysis of Cnm+ strains revealed that cnm is located between the core genes SMU.2067 and SMU.2069. Reverse transcription-PCR (RT-PCR) analysis showed that cnm is cotranscribed with SMU.2067, encoding a putative glycosyltransferase referred to here as PgfS (protein glycosyltransferase of streptococci). Notably, Cnm contains a threonine-rich domain predicted to undergo O-linked glycosylation. The previously shown abnormal migration pattern of Cnm, the...

18. Editorial Board

19. Requirement of the Flagellar Protein Export Apparatus Component FliO for Optimal Expression of Flagellar Genes in Helicobacter pylori - Tsang, Jennifer; Hoover, Timothy R.
Flagellar biogenesis in Helicobacter pylori involves the coordinated expression of flagellar genes with assembly of the flagellum. The H. pylori flagellar genes are organized into three regulons based on the sigma factor needed for their transcription (RpoD [σ80], RpoN [σ54], or FliA [σ28]). Transcription of RpoN-dependent genes is activated by a two-component system consisting of the sensor kinase FlgS and the response regulator FlgR. While the cellular cues sensed by the FlgS/FlgR two-component system remain to be elucidated, previous studies revealed that disrupting certain components of the flagellar export apparatus inhibited transcription of the RpoN regulon. FliO is the least...

20. Transcription Start Site Sequence and Spacing between the −10 Region and the Start Site Affect Reiterative Transcription-Mediated Regulation of Gene Expression in Escherichia coli - Han, Xiaosi; Turnbough, Charles L.
Reiterative transcription is a reaction catalyzed by RNA polymerase, in which nucleotides are repetitively added to the 3′ end of a nascent transcript due to upstream slippage of the transcript without movement of the DNA template. In Escherichia coli, the expression of several operons is regulated through mechanisms in which high intracellular levels of UTP promote reiterative transcription that adds extra U residues to the 3′ end of a nascent transcript during transcription initiation. Immediately following the addition of one or more extra U residues, the nascent transcripts are released from the transcription initiation complex, thereby reducing the level of...

Página de resultados:
 

Busque un recurso