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PubMed Central (PMC3 - NLM DTD) (2.616.353 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 94.551

1. Functional Consequences of Substitution Mutations in MepR, a Repressor of the Staphylococcus aureus mepA Multidrug Efflux Pump Gene - Schindler, Bryan D.; Seo, Susan M.; Jacinto, Pauline L.; Kumaraswami, Muthiah; Birukou, Ivan; Brennan, Richard G.; Kaatz, Glenn W.
The expression of mepA, encoding the Staphylococcus aureus MepA multidrug efflux protein, is repressed by the MarR homologue MepR. MepR dimers bind differently to operators upstream of mepR and mepA, with affinity being greatest at the mepA operator. MepR substitution mutations may result in mepA overexpression, with A103V most common in clinical strains. Evaluation of the functional consequences of this and other MepR substitutions using a lacZ reporter gene assay revealed markedly reduced repressor activity in the presence of Q18P, F27L, G97E, and A103V substitutions. Reporter data were generally supported by susceptibility and efflux assays, and electrophoretic mobility shift assays...

2. Length Control of the Flagellar Hook in a Temperature-Sensitive flgE Mutant of Salmonella enterica Serovar Typhimurium - Uchida, Kaoru; Dono, Kohei; Aizawa, Shin-Ichi
The flagellar hook is a short, curved, extracellular structure located between the basal body and the filament. The hook is composed of the FlgE protein. In this study, we analyzed flagellum assembly in a temperature-sensitive flgE mutant of Salmonella enterica serovar Typhimurium. When the mutant cells were grown at 30°C, they produced flagella of a normal length (71% of the population) and short hooks without filaments (26%). At 37°C, 70% of the basal bodies lacked hooks, and intact flagella made up only 6% of the population. Mutant cells secreted monomeric FlgE in abundance at 37°C, suggesting that the mutant FlgE...

3. Effect of an Oxygen-Tolerant Bifurcating Butyryl Coenzyme A Dehydrogenase/Electron-Transferring Flavoprotein Complex from Clostridium difficile on Butyrate Production in Escherichia coli - Aboulnaga, El-Hussiny; Pinkenburg, Olaf; Schiffels, Johannes; El-Refai, Ahmed; Buckel, Wolfgang; Selmer, Thorsten
The butyrogenic genes from Clostridium difficile DSM 1296T have been cloned and expressed in Escherichia coli. The enzymes acetyl-coenzyme A (CoA) C-acetyltransferase, 3-hydroxybutyryl-CoA dehydrogenase, crotonase, phosphate butyryltransferase, and butyrate kinase and the butyryl-CoA dehydrogenase complex composed of the dehydrogenase and two electron-transferring flavoprotein subunits were individually produced in E. coli and kinetically characterized in vitro. While most of these enzymes were measured using well-established test systems, novel methods to determine butyrate kinase and butyryl-CoA dehydrogenase activities with respect to physiological function were developed. Subsequently, the individual genes were combined to form a single plasmid-encoded operon in a plasmid vector, which...

4. Succinyl-CoA:3-Sulfinopropionate CoA-Transferase from Variovorax paradoxus Strain TBEA6, a Novel Member of the Class III Coenzyme A (CoA)-Transferase Family - Schürmann, Marc; Hirsch, Beatrice; Wübbeler, Jan Hendrik; Stöveken, Nadine; Steinbüchel, Alexander
The act gene of Variovorax paradoxus TBEA6 encodes a succinyl-CoA:3-sulfinopropionate coenzyme A (CoA)-transferase, ActTBEA6 (2.8.3.x), which catalyzes the activation of 3-sulfinopropionate (3SP), an intermediate during 3,3′-thiodipropionate (TDP) degradation. In a previous study, accumulation of 3SP was observed in a Tn5::mob-induced mutant defective in growth on TDP. In contrast to the wild type and all other obtained mutants, this mutant showed no growth when 3SP was applied as the sole source of carbon and energy. The transposon Tn5::mob was inserted in a gene showing high homology to class III CoA-transferases. In the present study, analyses of the translation product clearly allocated...

5. Chemoreceptor Gene Loss and Acquisition via Horizontal Gene Transfer in Escherichia coli - Borziak, Kirill; Fleetwood, Aaron D.; Zhulin, Igor B.
Chemotaxis allows bacteria to more efficiently colonize optimal microhabitats within their larger environment. Chemotaxis in Escherichia coli is the best-studied model system, and a large number of E. coli strains have been sequenced. The Escherichia/Shigella genus encompasses a great variety of commensal and pathogenic strains, but the role of chemotaxis in their association with the host remains poorly understood. Here we show that the core chemotaxis genes are lost in many, but not all, nonmotile strains but are well preserved in all motile strains. The genes encoding the Tar, Tsr, and Aer chemoreceptors, which mediate chemotaxis to a broad spectrum...

6. Role for Skp in LptD Assembly in Escherichia coli - Schwalm, Jaclyn; Mahoney, Tara F.; Soltes, Garner R.; Silhavy, Thomas J.
The periplasmic chaperone Skp has long been implicated in the assembly of outer membrane proteins (OMPs) in Escherichia coli. It has been shown to interact with unfolded OMPs, and the simultaneous loss of Skp and the main periplasmic chaperone in E. coli, SurA, results in synthetic lethality. However, a Δskp mutant displays only minor OMP assembly defects, and no OMPs have been shown to require Skp for their assembly. Here, we report a role for Skp in the assembly of the essential OMP LptD. This role may be compensated for by other OMP assembly proteins; in the absence of both...

7. Pilus Gene Pool Variation and the Virulence of Corynebacterium diphtheriae Clinical Isolates during Infection of a Nematode - Broadway, Melissa M.; Rogers, Elizabeth A.; Chang, Chungyu; Huang, I-Hsiu; Dwivedi, Prabhat; Yildirim, Suleyman; Schmitt, Michael P.; Das, Asis; Ton-That, Hung
Toxigenic Corynebacterium diphtheriae strains cause diphtheria in humans. The toxigenic C. diphtheriae isolate NCTC13129 produces three distinct heterotrimeric pili that contain SpaA, SpaD, and SpaH, making up the shaft structure. The SpaA pili are known to mediate bacterial adherence to pharyngeal epithelial cells. However, to date little is known about the expression of different pili in various clinical isolates and their importance in bacterial pathogenesis. Here, we characterized a large collection of C. diphtheriae clinical isolates for their pilin gene pool by PCR and for the expression of the respective pilins by immunoblotting with antibodies against Spa pilins. Consistent with...

8. MtvR Is a Global Small Noncoding Regulatory RNA in Burkholderia cenocepacia - Ramos, Christian G.; Grilo, André M.; da Costa, Paulo J. P.; Feliciano, Joana R.; Leitão, Jorge H.
Burkholderia cenocepacia J2315 is a highly epidemic and transmissible clinical isolate of the Burkholderia cepacia complex (Bcc), a group of bacteria causing life-threatening respiratory infections among cystic fibrosis patients. This work describes the functional analysis of the 136-nucleotide (nt)-long MtvR small noncoding RNA (sRNA) from the Bcc member B. cenocepacia J2315, with homologues restricted to the genus Burkholderia. Bioinformatic target predictions revealed a total of 309 mRNAs to be putative MtvR targets. The mRNA levels corresponding to 17 of 19 selected genes were found to be affected when MtvR was either overexpressed or silenced. Analysis of the interaction between MtvR...

9. In the Absence of RidA, Endogenous 2-Aminoacrylate Inactivates Alanine Racemases by Modifying the Pyridoxal 5′-Phosphate Cofactor - Flynn, Jeffrey M.; Downs, Diana M.
Members of the RidA (YjgF/YER057c/UK114) protein family are broadly conserved across the domains of life. In vitro, these proteins deaminate 3- or 4-carbon enamines that are generated as mechanistic intermediates of pyridoxal 5′-phosphate (PLP)-dependent serine/threonine dehydratases. The three-carbon enamine 2-aminoacrylate can inactivate some enzymes by forming a covalent adduct via a mechanism that has been well characterized in vitro. The biochemical activity of RidA suggested that the phenotypes of ridA mutant strains were caused by the accumulation of reactive enamine metabolites. The data herein show that in ridA mutant strains of Salmonella enterica, a stable 2-aminoacrylate (2-AA)/PLP adduct forms on...

10. The Sinorhizobium meliloti Essential Porin RopA1 Is a Target for Numerous Bacteriophages - Crook, Matthew B.; Draper, Alicia L.; Guillory, R. Jordan; Griffitts, Joel S.
The symbiotic nitrogen-fixing bacterium Sinorhizobium meliloti harbors a gene, SMc02396, which encodes a predicted outer membrane porin that is conserved in many symbiotic and pathogenic bacteria in the order Rhizobiales. Here, this gene (renamed ropA1) is shown to be required for infection by two commonly utilized transducing bacteriophages (ΦM12 and N3). Mapping of S. meliloti mutations conferring resistance to ΦM12, N3, or both phages simultaneously revealed diverse mutations mapping within the ropA1 open reading frame. Subsequent tests determined that RopA1, lipopolysaccharide, or both are required for infection by all of a larger collection of Sinorhizobium-specific phages. Failed attempts to disrupt...

11. Isolation and Characterization of Mutant Sinorhizobium meliloti NodD1 Proteins with Altered Responses to Luteolin - Peck, Melicent C.; Fisher, Robert F.; Bliss, Robert; Long, Sharon R.
NodD1, a member of the NodD family of LysR-type transcriptional regulators (LTTRs), mediates nodulation (nod) gene expression in the soil bacterium Sinorhizobium meliloti in response to the plant-secreted flavonoid luteolin. We used genetic screens and targeted approaches to identify NodD1 residues that show altered responses to luteolin during the activation of nod gene transcription. Here we report four types of NodD1 mutants. Type I (NodD1 L69F, S104L, D134N, and M193I mutants) displays reduced or no activation of nod gene expression. Type II (NodD1 K205N) is constitutively active but repressed by luteolin. Type III (NodD1 L280F) demonstrates enhanced activity with luteolin...

12. Genetic and Physiological Responses of Bifidobacterium animalis subsp. lactis to Hydrogen Peroxide Stress - Oberg, Taylor S.; Ward, Robert E.; Steele, James L.; Broadbent, Jeff R.
Consumer interest in probiotic bifidobacteria is increasing, but industry efforts to secure high cell viability in foods is undermined by these anaerobes' sensitivity to oxidative stress. To address this limitation, we investigated genetic and physiological responses of two fully sequenced Bifidobacterium animalis subsp. lactis strains, BL-04 and DSM 10140, to hydrogen peroxide (H2O2) stress. Although the genome sequences for these strains are highly clonal, prior work showed that they differ in both intrinsic and inducible H2O2 resistance. Transcriptome analysis of early-stationary-phase cells exposed to a sublethal H2O2 concentration detected significant (P < 0.05) changes in expression of 138 genes in...

13. The Streptococcus mutans Aminotransferase Encoded by ilvE Is Regulated by CodY and CcpA - Santiago, Brendaliz; Marek, Maksym; Faustoferri, Roberta C.; Quivey, Robert G.
The aminotransferase IlvE was implicated in the acid tolerance response of Streptococcus mutans when a mutation in its gene resulted in an acid-sensitive phenotype (B. Santiago, M. MacGilvray, R. C. Faustoferri, and R. G. Quivey, Jr., J. Bacteriol. 194:2010–2019, 2012). The phenotype suggested that amino acid metabolism is important for acid adaptation, as turnover of branched-chain amino acids (bcAAs) could provide important signals to modulate expression of genes involved in the adaptive process. Previous studies have demonstrated that ilvE is regulated in response to the external pH, though the mechanism is not yet established. CodY and CcpA have been shown...

14. Key Amino Acid Residues Involved in the Transitions of L- to R-Type Protofilaments of the Salmonella Flagellar Filament - Hayashi, Fumio; Tomaru, Hidetoshi; Furukawa, Eiji; Ikeda, Kanae; Fukano, Hiroko; Oosawa, Kenji
The flagellar filament enables bacteria to swim by functioning as a helical propeller. The filament is a supercoiled assembly of a single protein, flagellin, and is formed by 11 protofilaments arranged in a circle. Bacterial swimming and tumbling correlate with changes of the various helical structures, called polymorphic transformation, that are determined by the ratios of two distinct forms of protofilaments, the L and R types. The polymorphic transformation is caused by transition of the protofilament between L and R types. Elucidation of this transition mechanism has been addressed by comparing the atomic structures of L- and R-type straight filaments...

15. Regulation of the ald Gene Encoding Alanine Dehydrogenase by AldR in Mycobacterium smegmatis - Jeong, Ji-A; Baek, Eun-Young; Kim, Si Wouk; Choi, Jong-Soon; Oh, Jeong-Il
The regulatory gene aldR was identified 95 bp upstream of the ald gene encoding l-alanine dehydrogenase in Mycobacterium smegmatis. The AldR protein shows sequence similarity to the regulatory proteins of the Lrp/AsnC family. Using an aldR deletion mutant, we demonstrated that AldR serves as both activator and repressor for the regulation of ald gene expression, depending on the presence or absence of l-alanine. The purified AldR protein exists as a homodimer in the absence of l-alanine, while it adopts the quaternary structure of a homohexamer in the presence of l-alanine. The binding affinity of AldR for the ald control region...

16. Crippling the Essential GTPase Der Causes Dependence on Ribosomal Protein L9 - Naganathan, Anusha; Moore, Sean D.
Ribosomal protein L9 is a component of all eubacterial ribosomes, yet deletion strains display only subtle growth defects. Although L9 has been implicated in helping ribosomes maintain translation reading frame and in regulating translation bypass, no portion of the ribosome-bound protein seems capable of contacting either the peptidyltransferase center or the decoding center, so it is a mystery how L9 can influence these important processes. To reveal the physiological roles of L9 that have maintained it in evolution, we identified mutants of Escherichia coli that depend on L9 for fitness. In this report, we describe a class of L9-dependent mutants...

17. Quorum Sensing Regulatory Cascades Control Vibrio fluvialis Pathogenesis - Wang, Yunduan; Wang, Hui; Liang, Weili; Hay, Amanda J.; Zhong, Zengtao; Kan, Biao; Zhu, Jun
Quorum sensing (QS) is a process by which individual bacteria are able to communicate with one another, thereby enabling the population as a whole to coordinate gene regulation and subsequent phenotypic outcomes. Communication is accomplished through production and detection of small molecules in the extracellular milieu. In many bacteria, particularly Vibrio species, multiple QS systems result in multiple signals, as well as cross talk between systems. In this study, we identify two QS systems in the halophilic enteric pathogen Vibrio fluvialis: one acyl-homoserine lactone (AHL) based and one CAI-1/AI-2 based. We show that a LuxI homolog, VfqI, primarily produces 3-oxo-C10-HSL,...

18. Large Linear Plasmids of Borrelia Species That Cause Relapsing Fever - Miller, Shelley Campeau; Porcella, Stephen F.; Raffel, Sandra J.; Schwan, Tom G.; Barbour, Alan G.
Borrelia species of relapsing fever (RF) and Lyme disease (LD) lineages have linear chromosomes and both linear and circular plasmids. Unique to RF species, and little characterized to date, are large linear plasmids of ∼160 kb, or ∼10% of the genome. By a combination of Sanger and next-generation methods, we determined the sequences of large linear plasmids of two New World species: Borrelia hermsii, to completion of its 174-kb length, and B. turicatae, partially to 114 kb of its 150 kb. These sequences were then compared to corresponding sequences of the Old World species B. duttonii and B. recurrentis and...

19. Numbers of Individual Nutrient Germinant Receptors and Other Germination Proteins in Spores of Bacillus subtilis - Stewart, Kerry-Ann V.; Setlow, Peter
Germination of dormant Bacillus subtilis spores with specific nutrient germinants is dependent on a number of inner membrane (IM) proteins, including (i) the GerA, GerB, and GerK germinant receptors (GRs) that respond to nutrient germinants; (ii) the GerD protein, essential for optimal GR function; and (iii) SpoVA proteins, essential for the release of the spore-specific molecule dipicolinic acid (DPA) during spore germination. Levels of GR A and C subunit proteins, GerD, and SpoVAD in wild-type spores were determined by Western blot analysis of spore fractions or total disrupted spores by comparison with known amounts of purified proteins. Surprisingly, after disruption...

20. Phage-Encoded Inhibitor of Staphylococcus aureus Transcription Exerts Context-Dependent Effects on Promoter Function in a Modified Escherichia coli-Based Transcription System - Montero-Diez, Cristina; Deighan, Padraig; Osmundson, Joseph; Darst, Seth A.; Hochschild, Ann
Promoter recognition in bacteria is mediated primarily by the σ subunit of RNA polymerase (RNAP), which makes sequence-specific contacts with the promoter −10 and −35 elements in the context of the RNAP holoenzyme. However, the RNAP α subunit can also contribute to promoter recognition by making sequence-specific contacts with upstream (UP) elements that are associated with a subset of promoters, including the rRNA promoters. In Escherichia coli, these interactions between the RNAP α subunit (its C-terminal domain [CTD], in particular) and UP element DNA result in significant stimulation of rRNA transcription. Among the many cellular and bacteriophage-encoded regulators of transcription...

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