PubMed Central (PMC3 - NLM DTD)
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 95,164
The TetR-Type MfsR Protein of the Integrative and Conjugative Element (ICE) ICEclc Controls both a Putative Efflux System and Initiation of ICE Transfer - Pradervand, Nicolas; Delavat, François; Sulser, Sandra; Miyazaki, Ryo; van der Meer, Jan Roelof
Integrative and conjugating elements (ICE) are self-transferable DNAs widely present in bacterial genomes, which often carry a variety of auxiliary genes of potential adaptive benefit. One of the model ICE is ICEclc, an element originally found in Pseudomonas knackmussii B13 and known for its propensity to provide its host with the capacity to metabolize chlorocatechols and 2-aminophenol. In this work, we studied the mechanism and target of regulation of MfsR, a TetR-type repressor previously found to exert global control on ICEclc horizontal transfer. By using a combination of ICEclc mutant and transcriptome analysis, gene reporter fusions, and DNA binding assays,...
cbb3-Type Cytochrome c Oxidases, Aerobic Respiratory Enzymes, Impact the Anaerobic Life of Pseudomonas aeruginosa PAO1 - Hamada, Masakaze; Toyofuku, Masanori; Miyano, Tomoki; Nomura, Nobuhiko
For bacteria, many studies have focused on the role of respiratory enzymes in energy conservation; however, their effect on cell behavior is poorly understood. Pseudomonas aeruginosa can perform both aerobic respiration and denitrification. Previous studies demonstrated that cbb3-type cytochrome c oxidases that support aerobic respiration are more highly expressed in P. aeruginosa under anoxic conditions than are other aerobic respiratory enzymes. However, little is known about their role under such conditions. In this study, it was shown that cbb3 oxidases of P. aeruginosa PAO1 alter anaerobic growth, the denitrification process, and cell morphology under anoxic conditions. Furthermore, biofilm formation was...
Defect in the Formation of 70S Ribosomes Caused by Lack of Ribosomal Protein L34 Can Be Suppressed by Magnesium - Akanuma, Genki; Kobayashi, Ako; Suzuki, Shota; Kawamura, Fujio; Shiwa, Yuh; Watanabe, Satoru; Yoshikawa, Hirofumi; Hanai, Ryo; Ishizuka, Morio
To elucidate the biological functions of the ribosomal protein L34, which is encoded by the rpmH gene, the rpmH deletion mutant of Bacillus subtilis and two suppressor mutants were characterized. Although the ΔrpmH mutant exhibited a severe slow-growth phenotype, additional mutations in the yhdP or mgtE gene restored the growth rate of the ΔrpmH strain. Either the disruption of yhdP, which is thought to be involved in the efflux of Mg2+, or overexpression of mgtE, which plays a major role in the import of Mg2+, could suppress defects in both the formation of the 70S ribosome and growth caused by...
Bicarbonate Increases Binding Affinity of Vibrio cholerae ToxT to Virulence Gene Promoters - Thomson, Joshua J.; Withey, Jeffrey H.
The major Vibrio cholerae virulence gene transcription activator, ToxT, is responsible for the production of the diarrhea-inducing cholera toxin (CT) and the major colonization factor, toxin coregulated pilus (TCP). In addition to the two primary virulence factors mentioned, ToxT is responsible for the activation of accessory virulence genes, such as aldA, tagA, acfA, acfD, tcpI, and tarAB. ToxT activity is negatively modulated by bile and unsaturated fatty acids found in the upper small intestine. Conversely, previous work identified another intestinal signal, bicarbonate, which enhances the ability of ToxT to activate production of CT and TCP. The work presented here further...
Cell Separation in Vibrio cholerae Is Mediated by a Single Amidase Whose Action Is Modulated by Two Nonredundant Activators - Möll, Andrea; Dörr, Tobias; Alvarez, Laura; Chao, Michael C.; Davis, Brigid M.; Cava, Felipe; Waldor, Matthew K.
Synthesis and hydrolysis of septal peptidoglycan (PG) are critical processes at the conclusion of cell division that enable separation of daughter cells. Cleavage of septal PG is mediated by PG amidases, hydrolytic enzymes that release peptide side chains from the glycan strand. Most gammaproteobacteria, including Escherichia coli, encode several functionally redundant periplasmic amidases. However, members of the Vibrio genus, including the enteric pathogen Vibrio cholerae, encode only a single PG amidase, AmiB. Here, we show that V. cholerae AmiB is crucial for cell division and growth. Genetic and biochemical analyses indicated that AmiB is regulated by two activators, EnvC and...
Cell Division Resets Polarity and Motility for the Bacterium Myxococcus xanthus - Harvey, Cameron W.; Madukoma, Chinedu S.; Mahserejian, Shant; Alber, Mark S.; Shrout, Joshua D.
Links between cell division and other cellular processes are poorly understood. It is difficult to simultaneously examine division and function in most cell types. Most of the research probing aspects of cell division has experimented with stationary or immobilized cells or distinctly asymmetrical cells. Here we took an alternative approach by examining cell division events within motile groups of cells growing on solid medium by time-lapse microscopy. A total of 558 cell divisions were identified among approximately 12,000 cells. We found an interconnection of division, motility, and polarity in the bacterium Myxococcus xanthus. For every division event, motile cells stop...
Mg2+, K+, and the Ribosome - Nierhaus, Knud H.
Mg2+ and K+ are the prevalent di- and monovalent cations inside the cells in all three domains, playing a dominant role in structure and function of biological macromolecules. Ribosomes bind a substantial fraction of total Mg2+ and K+ cations. In this issue of the Journal of Bacteriology, Akanuma and coworkers (G. Akanuma et al., J. Bacteriol. 196:3820–3830, 2014, doi:10.1128/JB.01896-14) report a surprising genetic link between ribosome amounts per cell and the intracellular Mg2+ concentrations.
Cross-Species Comparison of the Burkholderia pseudomallei, Burkholderia thailandensis, and Burkholderia mallei Quorum-Sensing Regulons - Majerczyk, Charlotte D.; Brittnacher, Mitchell J.; Jacobs, Michael A.; Armour, Christopher D.; Radey, Matthew C.; Bunt, Richard; Hayden, Hillary S.; Bydalek, Ryland; Greenberg, E. Peter
Burkholderia pseudomallei, Burkholderia thailandensis, and Burkholderia mallei (the Bptm group) are close relatives with very different lifestyles: B. pseudomallei is an opportunistic pathogen, B. thailandensis is a nonpathogenic saprophyte, and B. mallei is a host-restricted pathogen. The acyl-homoserine lactone quorum-sensing (QS) systems of these three species show a high level of conservation. We used transcriptome sequencing (RNA-seq) to define the quorum-sensing regulon in each species, and we performed a cross-species analysis of the QS-controlled orthologs. Our analysis revealed a core set of QS-regulated genes in all three species, as well as QS-controlled factors shared by only two species or unique...
Patterns of Expression and Translocation of the Ubiquitin Ligase SlrP in Salmonella enterica Serovar Typhimurium - Cordero-Alba, Mar; Ramos-Morales, Francisco
SlrP is an E3 ubiquitin ligase that can be translocated into eukaryotic host cells by the two type III secretion systems that are expressed by Salmonella enterica serovar Typhimurium and are encoded in Salmonella pathogenicity islands 1 (SPI1) and 2 (SPI2). Expression of slrP and translocation of its product were examined using lac, 3×FLAG, and cyaA′ translational fusions. Although slrP was expressed in different media, optimal expression was found under conditions that imitate the intravacuolar environment and promote synthesis of the SPI2-encoded type III secretion system. Translocation into mammalian cells took place through the SPI1- or the SPI2-encoded type III...
The Cysteine Desulfhydrase CdsH Is Conditionally Required for Sulfur Mobilization to the Thiamine Thiazole in Salmonella enterica - Palmer, Lauren D.; Leung, Man Him; Downs, Diana M.
Thiamine pyrophosphate is a required coenzyme that contains a mechanistically important sulfur atom. In Salmonella enterica, sulfur is trafficked to both thiamine biosynthesis and 4-thiouridine biosynthesis by the enzyme ThiI using persulfide (R-S-S-H) chemistry. It was previously reported that a thiI mutant strain could grow independent of exogenous thiamine in the presence of cysteine, suggesting there was a second mechanism for sulfur mobilization. Data reported here show that oxidation products of cysteine rescue the growth of a thiI mutant strain by a mechanism that requires the transporter YdjN and the cysteine desulfhydrase CdsH. The data are consistent with a model...
Genetic Examination and Mass Balance Analysis of Pyruvate/Amino Acid Oxidation Pathways in the Hyperthermophilic Archaeon Thermococcus kodakarensis - Nohara, Kenta; Orita, Izumi; Nakamura, Satoshi; Imanaka, Tadayuki; Fukui, Toshiaki
The present study investigated the simultaneous oxidation of pyruvate and amino acids during H2-evolving growth of the hyperthermophilic archaeon Thermococcus kodakarensis. The comparison of mass balance between a cytosolic hydrogenase (HYH)-deficient strain (the ΔhyhBGSL strain) and the parent strain indicated that NADPH generated via H2 uptake by HYH was consumed by reductive amination of 2-oxoglutarate catalyzed by glutamate dehydrogenase. Further examinations were done to elucidate functions of three enzymes potentially involved in pyruvate oxidation: pyruvate formate-lyase (PFL), pyruvate:ferredoxin oxidoreductase (POR), and 2-oxoisovalerate:ferredoxin oxidoreductase (VOR) under the HYH-deficient background in T. kodakarensis. No significant change was observed by deletion of pflDA,...
Redox-Responsive Repressor Rex Modulates Alcohol Production and Oxidative Stress Tolerance in Clostridium acetobutylicum - Zhang, Lei; Nie, Xiaoqun; Ravcheev, Dmitry A.; Rodionov, Dmitry A.; Sheng, Jia; Gu, Yang; Yang, Sheng; Jiang, Weihong; Yang, Chen
Rex, a transcriptional repressor that modulates its DNA-binding activity in response to NADH/NAD+ ratio, has recently been found to play a role in the solventogenic shift of Clostridium acetobutylicum. Here, we combined a comparative genomic reconstruction of Rex regulons in 11 diverse clostridial species with detailed experimental characterization of Rex-mediated regulation in C. acetobutylicum. The reconstructed Rex regulons in clostridia included the genes involved in fermentation, hydrogen production, the tricarboxylic acid cycle, NAD biosynthesis, nitrate and sulfite reduction, and CO2/CO fixation. The predicted Rex-binding sites in the genomes of Clostridium spp. were verified by in vitro binding assays with purified...
Structural and Functional Characterization of Pseudomonas aeruginosa Global Regulator AmpR - Caille, Olivier; Zincke, Diansy; Merighi, Massimo; Balasubramanian, Deepak; Kumari, Hansi; Kong, Kok-Fai; Silva-Herzog, Eugenia; Narasimhan, Giri; Schneper, Lisa; Lory, Stephen; Mathee, Kalai
Pseudomonas aeruginosa is a dreaded pathogen in many clinical settings. Its inherent and acquired antibiotic resistance thwarts therapy. In particular, derepression of the AmpC β-lactamase is a common mechanism of β-lactam resistance among clinical isolates. The inducible expression of ampC is controlled by the global LysR-type transcriptional regulator (LTTR) AmpR. In the present study, we investigated the genetic and structural elements that are important for ampC induction. Specifically, the ampC (PampC) and ampR (PampR) promoters and the AmpR protein were characterized. The transcription start sites (TSSs) of the divergent transcripts were mapped using 5′ rapid amplification of cDNA ends-PCR (RACE-PCR),...
Molecular Characterization of Protease Activity in Serratia sp. Strain SCBI and Its Importance in Cytotoxicity and Virulence - Petersen, Lauren M.; Tisa, Louis S.
A newly recognized Serratia species, termed South African Caenorhabditis briggsae isolate (SCBI), is both a mutualist of the nematode Caenorhabditis briggsae KT0001 and a pathogen of lepidopteran insects. Serratia sp. strain SCBI displays high proteolytic activity, and because secreted proteases are known virulence factors for many pathogens, the purpose of this study was to identify genes essential for extracellular protease activity in Serratia sp. strain SCBI and to determine what role proteases play in insect pathogenesis and cytotoxicity. A bank of 2,100 transposon mutants was generated, and six SCBI mutants with defective proteolytic activity were identified. These mutants were also...
Staphylococcus aureus Alters Growth Activity, Autolysis, and Antibiotic Tolerance in a Human Host-Adapted Pseudomonas aeruginosa Lineage - Michelsen, Charlotte Frydenlund; Christensen, Anne-Mette Juel; Bojer, Martin Saxtorph; Høiby, Niels; Ingmer, Hanne; Jelsbak, Lars
Interactions among members of polymicrobial infections or between pathogens and the commensal flora may determine disease outcomes. Pseudomonas aeruginosa and Staphylococcus aureus are important opportunistic human pathogens and are both part of the polymicrobial infection communities in human hosts. In this study, we analyzed the in vitro interaction between S. aureus and a collection of P. aeruginosa isolates representing different evolutionary steps of a dominant lineage, DK2, that have evolved through decades of growth in chronically infected patients. While the early adapted P. aeruginosa DK2 strains outcompeted S. aureus during coculture on agar plates, we found that later P. aeruginosa...
Phenotypic Interactions among Mutations in a Thermus thermophilus 16S rRNA Gene Detected with Genetic Selections and Experimental Evolution - Gregory, Steven T.; Connetti, Jacqueline L.; Carr, Jennifer F.; Jogl, Gerwald; Dahlberg, Albert E.
During protein synthesis, the ribosome undergoes conformational transitions between functional states, requiring communication between distant structural elements of the ribosome. Despite advances in ribosome structural biology, identifying the protein and rRNA residues governing these transitions remains a significant challenge. Such residues can potentially be identified genetically, given the predicted deleterious effects of mutations stabilizing the ribosome in discrete conformations and the expected ameliorating effects of second-site compensatory mutations. In this study, we employed genetic selections and experimental evolution to identify interacting mutations in the ribosome of the thermophilic bacterium Thermus thermophilus. By direct genetic selections, we identified mutations in 16S...
Probing the Structure of the S105 Hole - To, Kam H.; Young, Ry
For most phages, holins control the timing of host lysis. During the morphogenesis period of the infection cycle, canonical holins accumulate harmlessly in the cytoplasmic membrane until they suddenly trigger to form lethal lesions called holes. The holes can be visualized by cryo-electron microscopy and tomography as micrometer-scale interruptions in the membrane. To explore the fine structure of the holes formed by the lambda holin, S105, a cysteine-scanning accessibility study was performed. A collection of S105 alleles encoding holins with a single Cys residue in different positions was developed and characterized for lytic function. Based on the ability of 4-acetamido-4′-((iodoacetyl)...
Evidence against Translational Repression by the Carboxyltransferase Component of Escherichia coli Acetyl Coenzyme A Carboxylase - Smith, Alexander C.; Cronan, John E.
In Escherichia coli, synthesis of the malonyl coenzyme A (malonyl-CoA) required for membrane lipid synthesis is catalyzed by acetyl-CoA carboxylase, a large complex composed of four subunits. The subunit proteins are needed in a defined stoichiometry, and it remains unclear how such production is achieved since the proteins are encoded at three different loci. Meades and coworkers (G. Meades, Jr., B. K. Benson, A. Grove, and G. L. Waldrop, Nucleic Acids Res. 38:1217–1227, 2010, doi:http://dx.doi.org/10.1093/nar/gkp1079) reported that coordinated production of the AccA and AccD subunits is due to a translational repression mechanism exerted by the proteins themselves. The AccA and...