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228 Publications visible to you, out of a total of 228
Recombination between ccrC genes in a type V (5C2&5) staphylococcal cassette chromosome mec (SCCmec) of Staphylococcus aureus ST398 leads to conversion from methicillin resistance to methicillin susceptibility in vivo

Abstract (Expand)

Various types of the staphylococcal cassette chromosome mec (SCCmec) are known to confer methicillin resistance on the human pathogen Staphylococcus aureus. Such cassettes are not always stably maintained. … The present studies were aimed at identifying the mechanism underlying the in vivo conversion of methicillin-resistant S. aureus (MRSA) to methicillin-susceptible S. aureus (MSSA) derivatives as encountered in two patients suffering from pneumonia and an umbilicus infection, respectively. All MRSA and MSSA isolates identified belong to multilocus sequence type (MLST) 398, have spa type t034, and are Panton-Valentine leukocidin positive. Sequencing of 27,616 nucleotides from the chromosomal SCCmec insertion site in orfX to the hsdR gene for a restriction enzyme revealed a type V (5C2&5) SCCmec. Sequence comparisons show that parts of the cassette are highly similar to sequences within SCCmec elements from coagulase-negative staphylococci, indicating a possible common origin. The cassette investigated contains ccrC-carrying units on either side of its class C2b mec gene complex. In vivo loss of the mec gene complex was caused by recombination between the recombinase genes ccrC1 allele 8 and ccrC1 allele 10. In vitro, the SCCmec was very stable, and low-frequency MRSA-to-MSSA conversion was only observed when MRSA isolates were cultivated at 41 degrees C for prolonged periods of time. In this case also, loss of the mec complex was due to ccrC gene recombination. Interestingly, the MRSA and MSSA isolates studied displayed no detectable differences in competitive growth and virulence, suggesting that the presence of the intact type V (5C2&5) SCCmec has no negative bearing on staphylococcal fitness under the conditions used.

Authors: Monika A Chlebowicz, Kristelle Nganou, Svitlana Kozytska, Jan P Arends, Susanne Engelmann, Hajo Grundmann, Knut Ohlsen, , Girbe Buist

Date Published: 7th Dec 2009

Publication Type: Not specified

Ref2, a regulatory subunit of the yeast protein phosphatase 1, is a novel component of cation homoeostasis

Abstract (Expand)

Maintenance of cation homoeostasis is a key process for any living organism. Specific mutations in Glc7, the essential catalytic subunit of yeast protein phosphatase 1, result in salt and alkaline pH … sensitivity, suggesting a role for this protein in cation homoeostasis. We screened a collection of Glc7 regulatory subunit mutants for altered tolerance to diverse cations (sodium, lithium and calcium) and alkaline pH. Among 18 candidates, only deletion of REF2 (RNA end formation 2) yielded increased sensitivity to these conditions, as well as to diverse organic toxic cations. The Ref2F374A mutation, which renders it unable to bind Glc7, did not rescue the salt-related phenotypes of the ref2 strain, suggesting that Ref2 function in cation homoeostasis is mediated by Glc7. The ref2 deletion mutant displays a marked decrease in lithium efflux, which can be explained by the inability of these cells to fully induce the Na+-ATPase ENA1 gene. The effect of lack of Ref2 is additive to that of blockage of the calcineurin pathway and might disrupt multiple mechanisms controlling ENA1 expression. ref2 cells display a striking defect in vacuolar morphogenesis, which probably accounts for the increased calcium levels observed under standard growth conditions and the strong calcium sensitivity of this mutant. Remarkably, the evidence collected indicates that the role of Ref2 in cation homoeostasis may be unrelated to its previously identified function in the formation of mRNA via the APT (for associated with Pta1) complex.

Authors: Jofre Ferrer-Dalmau, Asier González, Maria Platara, , José L Martínez, , , ,

Date Published: 24th Dec 2009

Publication Type: Not specified

Regulation of the Activity of Lactate Dehydrogenases from Four Lactic Acid Bacteria

Abstract

Not specified

Authors: , , H. Messiha, , , , , , ,

Date Published: 17th May 2013

Publication Type: Not specified

Regulation of Trk-dependent potassium transport by the calcineurin pathway involves the Hal5 kinase

Abstract (Expand)

The phosphatase calcineurin and the kinases Hal4/Hal5 regulate high-affinity potassium uptake in Saccharomyces cerevisiae through the Trk1 transporter. We demonstrate that calcineurin is necessary for … high-affinity potassium uptake even in the absence of Na(+) stress. HAL5 expression is induced in response to stress in a calcineurin-dependent manner through a newly identified functional CDRE (nt -195/-189). Lack of calcineurin decreases Hal5 protein levels, although with little effect on Trk1 amounts. However, the growth defect of cnb1 cells at K(+)-limiting conditions can be rescued in part by overexpression of HAL5, and this mutation further aggravates the potassium requirements of a hal4 strain. This suggests that the control exerted by calcineurin on Hal5 expression may be biologically relevant for Trk1 regulation.

Authors: Carlos Casado, Lynne Yenush, Carmen Melero, María del Carmen Ruiz, Raquel Serrano, Jorge Pérez-Valle, ,

Date Published: 3rd Jul 2009

Publication Type: Not specified

Reproducible computational biology experiments with SED-ML--the Simulation Experiment Description Markup Language

Abstract (Expand)

The increasing use of computational simulation experiments to inform modern biological research creates new challenges to annotate, archive, share and reproduce such experiments. The recently published … Minimum Information About a Simulation Experiment (MIASE) proposes a minimal set of information that should be provided to allow the reproduction of simulation experiments among users and software tools.

Authors: Dagmar Waltemath, Richard Adams, Frank T Bergmann, Michael Hucka, Fedor Kolpakov, Andrew K Miller, Ion I Moraru, David Nickerson, Sven Sahle, , Nicolas Le Novère

Date Published: 15th Dec 2011

Publication Type: Not specified

Reprogramming of Escherichia coli K-12 metabolism during the initial phase of transition from an anaerobic to a micro-aerobic environment

Abstract (Expand)

Many bacteria undergo transitions between environments with differing O₂ availabilities as part of their natural lifestyles and during biotechnological processes. However, the dynamics of adaptation … when bacteria experience changes in O₂ availability are understudied. The model bacterium and facultative anaerobe Escherichia coli K-12 provides an ideal system for exploring this process.

Authors: Eleanor W Trotter, , Andrea M Hounslow, C Jeremy Craven, Michael P Williamson, , ,

Date Published: 27th Sep 2011

Publication Type: Not specified

Requirement of the agr locus for colony spreading of Staphylococcus aureus

Abstract (Expand)

The important human pathogen Staphylococcus aureus is known to spread on soft agar plates. Here, we show that colony spreading of S. aureus involves the agr quorum-sensing system. This finding can be … related to the agr-dependent expression of biosurfactants, such as phenol-soluble modulins, suggesting a connection between spreading motility and virulence.

Authors: Eleni Tsompanidou, Mark J J B Sibbald, Monika A Chlebowicz, Annette Dreisbach, Jaap Willem Back, , Girbe Buist, Emma L Denham

Date Published: 17th Dec 2010

Publication Type: Not specified

RightField: embedding ontology annotation in spreadsheets.

Abstract (Expand)

MOTIVATION: In the Life Sciences, guidelines, checklists and ontologies describing what metadata is required for the interpretation and reuse of experimental data are emerging. Data producers, however, … may have little experience in the use of such standards and require tools to support this form of data annotation. RESULTS: RightField is an open source application that provides a mechanism for embedding ontology annotation support for Life Science data in Excel spreadsheets. Individual cells, columns or rows can be restricted to particular ranges of allowed classes or instances from chosen ontologies. The RightField-enabled spreadsheet presents selected ontology terms to the users as a simple drop-down list, enabling scientists to consistently annotate their data. The result is 'semantic annotation by stealth', with an annotation process that is less error-prone, more efficient, and more consistent with community standards. AVAILABILITY AND IMPLEMENTATION: RightField is open source under a BSD license and freely available from http://www.rightfield.org.uk

Authors: , , Matthew Horridge, , , , ,

Date Published: 15th Jul 2011

Publication Type: Journal

RNA degradation in Bacillus subtilis: an interplay of essential endo- and exoribonucleases

Abstract (Expand)

RNA processing and degradation are key processes in the control of transcript accumulation and thus in the control of gene expression. In Escherichia coli, the underlying mechanisms and components of … RNA decay are well characterized. By contrast, Gram-positive bacteria do not possess several important players of E. coli RNA degradation, most notably the essential enzyme RNase E. Recent research on the model Gram-positive organism, Bacillus subtilis, has identified the essential RNases J1 and Y as crucial enzymes in RNA degradation. While RNase J1 is the first bacterial exoribonuclease with 5'-to-3' processivity, RNase Y is the founding member of a novel class of endoribonucleases. Both RNase J1 and RNase Y have a broad impact on the stability of B. subtilis mRNAs; a depletion of either enzyme affects more than 25% of all mRNAs. RNases J1 and Y as well as RNase J2, the polynucleotide phosphorylase PNPase, the RNA helicase CshA and the glycolytic enzymes enolase and phosphofructokinase have been proposed to form a complex, the RNA degradosome of B. subtilis. This review presents a model, based on recent published data, of RNA degradation in B. subtilis. Degradation is initiated by RNase Y-dependent endonucleolytic cleavage, followed by processive exoribonucleolysis of the generated fragments both in 3'-to-5' and in 5'-to-3' directions. The implications of these findings for pathogenic Gram-positive bacteria are also discussed.

Authors: Martin Lehnik-Habrink, , ,

Date Published: 8th May 2012

Publication Type: Not specified

RNA processing in Bacillus subtilis: identification of targets of the essential RNase Y

Abstract (Expand)

RNA processing and degradation is initiated by endonucleolytic cleavage of the target RNAs. In many bacteria, this activity is performed by RNase E which is not present in Bacillus subtilis and other … Gram-positive bacteria. Recently, the essential endoribonuclease RNase Y has been discovered in B. subtilis. This RNase is involved in the degradation of bulk mRNA suggesting a major role in RNA metabolism. However, only a few targets of RNase Y have been identified so far. In order to assess the global impact of RNase Y, we compared the transcriptomes in response to the expression level of RNase Y. Our results demonstrate that processing by RNase Y results in accumulation of about 550 mRNAs. Some of these targets were substantially stabilized by RNase Y depletion, resulting in half-lives in the range of an hour. Moreover, about 350 mRNAs were less abundant when RNase Y was depleted among them the mRNAs of the operons required for biofilm formation. Interestingly, overexpression of RNase Y was sufficient to induce biofilm formation. The results presented in this work emphasize the importance of RNase Y as the global acting endoribonuclease for B. subtilis.

Authors: Martin Lehnik-Habrink, Marc Schaffer, , Christine Diethmaier, Christina Herzberg,

Date Published: 4th Aug 2011

Publication Type: Not specified

RNase Y in Bacillus subtilis: a Natively disordered protein that is the functional equivalent of RNase E from Escherichia coli

Abstract (Expand)

The control of mRNA stability is an important component of regulation in bacteria. Processing and degradation of mRNAs are initiated by an endonucleolytic attack, and the cleavage products are processively … degraded by exoribonucleases. In many bacteria, these RNases, as well as RNA helicases and other proteins, are organized in a protein complex called the RNA degradosome. In Escherichia coli, the RNA degradosome is assembled around the essential endoribonuclease E. In Bacillus subtilis, the recently discovered essential endoribonuclease RNase Y is involved in the initiation of RNA degradation. Moreover, RNase Y interacts with other RNases, the RNA helicase CshA, and the glycolytic enzymes enolase and phosphofructokinase in a degradosome-like complex. In this work, we have studied the domain organization of RNase Y and the contribution of the domains to protein-protein interactions. We provide evidence for the physical interaction between RNase Y and the degradosome partners in vivo. We present experimental and bioinformatic data which indicate that the RNase Y contains significant regions of intrinsic disorder and discuss the possible functional implications of this finding. The localization of RNase Y in the membrane is essential both for the viability of B. subtilis and for all interactions that involve RNase Y. The results presented in this study provide novel evidence for the idea that RNase Y is the functional equivalent of RNase E, even though the two enzymes do not share any sequence similarity.

Authors: Martin Lehnik-Habrink, , Fabian M Rothe, Alexandra S Solovyova, Cecilia Rodrigues, Christina Herzberg, Fabian M Commichau, ,

Date Published: 29th Jul 2011

Publication Type: Not specified

Role of phosphate in the central metabolism of two lactic acid bacteria - a comparative systems biology approach

Abstract (Expand)

Lactic acid-producing bacteria survive in distinct environments, but show common metabolic characteristics. Here we studied the dynamic interactions of the central metabolism in Lactococcus lactis, … extensively used as starter in dairy industry, and Streptococcus pyogenes, a human pathogen. Glucose-pulse experiments and enzymatic measurements were performed to parameterize kinetic models of glycolysis. Significant improvements were made to existing kinetic models for L. lactis, which subsequently accelerated the development of the first kinetic model of S. pyogenes glycolysis. The models revealed an important role for extracellular phosphate in regulation of central metabolism and the efficient use of glucose. Thus, phosphate which is rarely taken into account as an independent species in models of central metabolism has to be considered more thoroughly in the analysis of metabolic systems in the future. Insufficient phosphate supply can lead to a strong inhibition of glycolysis at high glucose concentration in both species, but more severely in S. pyogenes. S. pyogenes is more efficient in converting glucose to ATP, showing a higher tendency towards heterofermentative energy metabolism than L. lactis. Our comparative systems biology approach revealed that the glycolysis of L. lactis and S. pyogenes have similar characteristics, but are adapted to their individual natural habitats with respect to phosphate regulation. The mathematical models described here have been submitted to the Online Cellular Systems Modelling Database and can be accessed at http://jjj.biochem.sun.ac.za/database/levering/index.html free of charge.

Editor:

Date Published: 14th Feb 2012

Publication Type: Not specified

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