bluuebunny/crossref_metadata_2025 huggingface dataset:
Environmental Regulation of
Pseudomonas aeruginosa
PAO1 Las and Rhl Quorum-Sensing Systems
Authors: Duan Kangmin , Surette Michael G.
Published: April 2007

The
lasI
-
lasR
and the
rhlI
-
rhlR
quorum-sensing systems in
Pseudomonas aeruginosa
regulate the expression of numerous cellular and secreted virulence factor genes and play important roles in the development of biofilms. The
las
and
rhl
systems themselves are known to be directly or indirectly regulated by a number of transcriptional regulators, and consequently, their expression is sensitive to environmental conditions. In this report, the activities of these two quorum-sensing systems have been examined systematically under 46 growth conditions, and the regulation by environmental conditions has been investigated. The relative timing and strength of expression of these two systems varied significantly under different conditions, which contrasts with the notion of a preset hierarchy with these two systems in
P. aeruginosa
. Depending on the growth conditions, the correlation between each synthase and its cognate transcriptional regulator also varied, suggesting that the transcription of these genes independently allows for further fine tuning of each system. Finally, we observe that the activities of both the
lasI
-
lasR
and the
rhlI
-
rhlR
quorum-sensing systems were dramatically enhanced in the presence of extracts of sputum samples from cystic fibrosis patients.
A Copper-Activated Two-Component System Interacts with Zinc and Imipenem Resistance in
Pseudomonas aeruginosa
Authors: Caille Olivier , Rossier Claude , Perron Karl
Published: April 2007

The effects of copper (Cu) on trace metal and antibiotic resistance of
Pseudomonas aeruginosa
have been investigated. Cu treatments induced resistance not only to this metal but also, surprisingly, to zinc (Zn). Quantitative reverse transcription-PCR (qRT-PCR) revealed that after Cu treatment the transcription of the
czcRS
two-component system (TCS) operon was enhanced as well as that of the
czcCBA
operon encoding an efflux pump specific for zinc, cadmium, and cobalt. Cu treatments at the same time caused a decrease in the production of OprD porin, resulting in resistance to the carbapenem antibiotic imipenem. The CzcR regulator was known to repress
oprD
. However, Cu was still able to decrease the production of OprD and induce imipenem resistance in a
czcRS
knockout mutant. This strongly suggested that another Cu-dependent regulatory system was acting negatively on
oprD
expression. TCS regulator genes
copR-copS
have been shown to be involved in Cu tolerance in
P. aeruginosa
. qRT-PCR showed that overproduction of the CopR or of the CzcR regulator resulted in increased transcription of the
czcC
gene as well as in a decrease in
oprD
gene transcription, either in the wild-type strain or in the
czcRS
knockout mutant. Overproduction experiments suggest that a metal-dependent mechanism operates at the posttranscriptional level to control the production of the CzcCBA efflux pump. This study shows that CopR is a new negative regulator of OprD porin and that it links Zn, Cu, and imipenem resistances by interacting with the CzcRS TCS.
Structure-Based Functional Analysis of the Replication Protein of Plasmid R6K: Key Amino Acids at the π/DNA Interface
Authors: Kunnimalaiyaan Selvi , Rakowski Sheryl A. , Filutowicz Marcin
Published: April 2007

In previous work, we characterized the bases in an iteron of plasmid R6K that are important for the binding of π protein monomers and dimers. Here we investigate the following six amino acids of π, encoded by
pir
, hypothesized to be important for DNA contact: Ser71, Try74, Gly131, Gly211, Arg225, and Arg254.
A Polyomic Approach To Elucidate the Fluoranthene-Degradative Pathway inMycobacterium vanbaaleniiPYR-1
Authors: Kweon Ohgew , Kim Seong-Jae , Jones Richard C. , Freeman James P. , Adjei Michael D. , Edmondson Ricky D. , Cerniglia Carl E.
Published: April 2007

Mycobacterium vanbaaleniiPYR-1 is capable of degrading a wide range of high-molecular-weight polycyclic aromatic hydrocarbons (PAHs), including fluoranthene. We used a combination of metabolomic, genomic, and proteomic technologies to investigate fluoranthene degradation in this strain. Thirty-seven fluoranthene metabolites including potential isomers were isolated from the culture medium and analyzed by high-performance liquid chromatography, gas chromatography-mass spectrometry, and UV-visible absorption. Total proteins were separated by one-dimensional gel and analyzed by liquid chromatography-tandem mass spectrometry in conjunction with theM. vanbaaleniiPYR-1 genome sequence (http://jgi.doe.gov), which resulted in the identification of 1,122 proteins. Among them, 53 enzymes were determined to be likely involved in fluoranthene degradation. We integrated the metabolic information with the genomic and proteomic results and proposed pathways for the degradation of fluoranthene. According to our hypothesis, the oxidation of fluoranthene is initiated by dioxygenation at the C-1,2, C-2,3, and C-7,8 positions. The C-1,2 and C-2,3 dioxygenation routes degrade fluoranthene via fluorene-type metabolites, whereas the C-7,8 routes oxidize fluoranthene via acenaphthylene-type metabolites. The major site of dioxygenation is the C-2,3 dioxygenation route, which consists of 18 enzymatic steps via 9-fluorenone-1-carboxylic acid and phthalate with the initial ring-hydroxylating oxygenase, NidA3B3, oxidizing fluoranthene to fluoranthenecis-2,3-dihydrodiol. Nonspecific monooxygenation of fluoranthene with subsequent O methylation of dihydroxyfluoranthene also occurs as a detoxification reaction.
Variability and Expression of Ankyrin Domain Genes in
Wolbachia
Variants Infecting the Mosquito
Culex pipiens
Authors: Duron Olivier , Boureux Anthony , Echaubard Pierre , Berthomieu Arnaud , Berticat Claire , Fort Philippe , Weill Mylène
Published: April 2007

Wolbachia
strains are maternally inherited endosymbiotic bacteria that infect many arthropod species and have evolved several different ways of manipulating their hosts, the most frequent way being cytoplasmic incompatibility (CI). CI leads to embryo death in crosses between infected males and uninfected females as well as in crosses between individuals infected by incompatible
Wolbachia
strains. The mosquito
Culex pipiens
exhibits the highest crossing type variability reported so far. Our crossing data support the notion that CI might be driven by at least two distinct genetic units that control the CI functions independently in males and females. Although the molecular basis of CI remains unknown, proteins with ankyrin (ANK) domains represent promising candidates since they might interact with a wide range of host proteins. Here we searched for sequence variability in the 58 ANK genes carried in the genomes of
Wolbachia
variants infecting
Culex pipiens
. Only five ANK genes were polymorphic in the genomes of incompatible
Wolbachia
variants, and none correlated with the CI pattern obtained with 15 mosquito strains (representing 14
Wolbachia
variants). Further analysis of ANK gene expression evidenced host- and sex-dependent variations, which did not improve the correlation. Taken together, these data do not support the direct implication of ANK genes in CI determinism.
Augmented Expression of Polysaccharide Intercellular Adhesin in a DefinedStaphylococcus epidermidisMutant with the Small-Colony-Variant Phenotype
Authors: Al Laham Nahed , Rohde Holger , Sander Gunnar , Fischer Andreas , Hussain Muzaffar , Heilmann Christine , Mack Dietrich , Proctor Richard , Peters Georg , Becker Karsten , von Eiff Christof
Published: April 2007

While coagulase-negative staphylococci (CoNS), with their ability to form a thick, multilayered biofilm on foreign bodies, have been identified as the major cause of implant-associated infections, no data are available about biofilm formation by staphylococcal small-colony variants (SCVs). In the past years, a number of device-associated infections due to staphylococcal SCVs were described, among them, several pacemaker infections due to SCVs of CoNS auxotrophic to hemin. To test the characteristics of SCVs of CoNS, in particular, to study the ability of SCVs to form a biofilm on foreign bodies, we generated a stable mutant in electron transport by interrupting one of the hemin biosynthetic genes,hemB, inStaphylococcus epidermidis. In fact, this mutant displayed a stable SCV phenotype with tiny colonies showing strong adhesion to the agar surface. When the incubation time was extended to 48 h or a higher inoculum concentration was used, the mutant produced biofilm amounts on polystyrene similar to those produced by the parent strain. When grown under planktonic conditions, the mutant formed markedly larger cell clusters than the parental strain which were completely disintegrated by the specific β-1,6-hexosaminidase dispersin B but were resistant to trypsin treatment. In a dot blot assay, the mutant expressed larger amounts of polysaccharide intercellular adhesin (PIA) than the parent strain. In conclusion, interrupting a hemin biosynthetic gene inS. epidermidisresulted in an SCV phenotype. Markedly larger cell clusters and the ability of thehemBmutant to form a biofilm are related to the augmented expression of PIA.
Enzymology and Evolution of the Pyruvate Pathway to 2-Oxobutyrate in
Methanocaldococcus jannaschii
Authors: Drevland Randy M. , Waheed Abdul , Graham David E.
Published: April 2007

The archaeon
Methanocaldococcus jannaschii
uses three different 2-oxoacid elongation pathways, which extend the chain length of precursors in leucine, isoleucine, and coenzyme B biosyntheses. In each of these pathways an aconitase-type hydrolyase catalyzes an hydroxyacid isomerization reaction. The genome sequence of
M. jannaschii
encodes two homologs of each large and small subunit that forms the hydrolyase, but the genes are not cotranscribed. The genes are more similar to each other than to previously characterized isopropylmalate isomerase or homoaconitase enzyme genes. To identify the functions of these homologs, the four combinations of subunits were heterologously expressed in
Escherichia coli
, purified, and reconstituted to generate the iron-sulfur center of the holoenzyme. Only the combination of MJ0499 and MJ1277 proteins catalyzed isopropylmalate and citramalate isomerization reactions. This pair also catalyzed hydration half-reactions using citraconate and maleate. Another broad-specificity enzyme, isopropylmalate dehydrogenase (MJ0720), catalyzed the oxidative decarboxylation of β-isopropylmalate, β-methylmalate, and
d
-malate. Combined with these results, phylogenetic analysis suggests that the pyruvate pathway to 2-oxobutyrate (an alternative to threonine dehydratase in isoleucine biosynthesis) evolved several times in bacteria and archaea. The enzymes in the isopropylmalate pathway of leucine biosynthesis facilitated the evolution of 2-oxobutyrate biosynthesis through the introduction of a citramalate synthase, either by gene recruitment or gene duplication and functional divergence.
The Oxidoreductase DsbA Plays a Key Role in the Ability of the Crohn's Disease-Associated Adherent-Invasive
Escherichia coli
Strain LF82 To Resist Macrophage Killing
Authors: Bringer Marie-Agnès , Rolhion Nathalie , Glasser Anne-Lise , Darfeuille-Michaud Arlette
Published: April 2007

Adherent-invasive
Escherichia coli
(AIEC) isolated from Crohn's disease patients is able to adhere to and invade intestinal epithelial cells and to replicate in mature phagolysosomes within macrophages. Here, we show that the
dsbA
gene, encoding a periplasmic oxidoreductase, was required for AIEC strain LF82 to adhere to intestinal epithelial cells and to survive within macrophages. The LF82-Δ
dsbA
mutant did not express flagella and, probably as a consequence of this, did not express type 1 pili. The role of DsbA in adhesion is restricted to the loss of flagella and type 1 pili, as forced contact between bacteria and cells and induced expression of type 1 pili restored the wild-type phenotype. In contrast, the
dsbA
gene is essential for AIEC LF82 bacteria to survive within macrophages, irrespective of the loss of flagella and type 1 pilus expression, and the survival ability of LF82-Δ
dsbA
was as low as that of the nonpathogenic
E. coli
K-12, which was efficiently killed by macrophages. We also provide evidence that the
dsbA
gene is needed for LF82 bacteria to grow and survive in an acidic and nutrient-poor medium that partly mimics the harsh environment of the phagocytic vacuole. In addition, under such stress conditions
dsbA
transcription is highly up-regulated. Finally, the CpxRA signaling pathway does not play a role in regulation of
dsbA
expression in AIEC LF82 bacteria under conditions similar to those of mature phagolysosomes.
Genetic Dissection of Specificity Determinants in the Interaction of HPr with Enzymes II of the Bacterial Phosphoenolpyruvate:Sugar Phosphotransferase System inEscherichia coli
Authors: Reichenbach Birte , Breustedt Daniel A. , Stülke Jörg , Rak Bodo , Görke Boris
Published: April 2007

The histidine protein (HPr) is the energy-coupling protein of the phosphoenolpyruvate (PEP)-dependent carbohydrate:phosphotransferase system (PTS), which catalyzes sugar transport in many bacteria. In its functions, HPr interacts with a number of evolutionarily unrelated proteins. Mainly, it delivers phosphoryl groups from enzyme I (EI) to the sugar-specific transporters (EIIs). HPr proteins of different bacteria exhibit almost identical structures, and, where known, they use similar surfaces to interact with their target proteins. Here we studied the in vivo effects of the replacement of HPr and EI ofEscherichia coliwith the homologous proteins fromBacillus subtilis, a gram-positive bacterium. This replacement resulted in severe growth defects on PTS sugars, suggesting that HPr ofB. subtilis cannot efficiently phosphorylate the EIIs ofE. coli. In contrast, activation of theE. coliBglG regulatory protein by HPr-catalyzed phosphorylation works well with theB. subtilisHPr protein. Random mutations were introduced intoB. subtilisHPr, and a screen for improved growth on PTS sugars yielded amino acid changes in positions 12, 16, 17, 20, 24, 27, 47, and 51, located in the interaction surface of HPr. Most of the changes restore intermolecular hydrophobic interactions and salt bridges normally formed by the corresponding residues inE. coliHPr. The residues present at the targeted positions differ between HPrs of gram-positive and -negative bacteria, but within each group they are highly conserved. Therefore, they may constitute a signature motif that determines the specificity of HPr for either gram-negative or -positive EIIs.
Conversion of Flavodoxin from Holoenzyme to Apoprotein during Growth Phase Changes inHelicobacter pylori
Authors: Shimomura Hirofumi , Hayashi Shunji , Yokota Kenji , Oguma Keiji , Hirai Yoshikazu
Published: April 2007

The catabolic pathway for flavodoxin has yet to be clarified for any bacterial species. In this study, we found that the flavin mononucleotide in the flavodoxin ofHelicobacter pyloriis degraded to riboflavin via the phosphomonoesterase activity of class C acid phosphatase. The result is a conversion of holoflavodoxin to apoflavodoxin.
Quorum Sensing Regulates Denitrification in
Pseudomonas aeruginosa
PAO1
Authors: Toyofuku Masanori , Nomura Nobuhiko , Fujii Tatsuya , Takaya Naoki , Maseda Hideaki , Sawada Isao , Nakajima Toshiaki , Uchiyama Hiroo
Published: April 2007

Anaerobic growth of
Pseudomonas aeruginosa
PAO1 was affected by quorum sensing. Deletion of genes that produce
N
-acyl-
l
-homoserine lactone signals resulted in an increase in denitrification activity, which was repressed by exogenous signal molecules. The effect of the
las
quorum-sensing system was dependent on the
rhl
quorum-sensing system in regulating denitrification.
Characterization of a Novel Bile-Inducible Operon Encoding a Two-Component Regulatory System inLactobacillus acidophilus
Authors: Pfeiler Erika A. , Azcarate-Peril M. Andrea , Klaenhammer Todd R.
Published: April 2007

Lactobacillus acidophilusNCFM is an industrially important strain used extensively as a probiotic culture. Tolerance of the presence of bile is an attribute important to microbial survival in the intestinal tract. A whole-genome microarray was employed to examine the effects of bile on the global transcriptional profile of this strain, with the intention of elucidating genes contributing to bile tolerance. Genes involved in carbohydrate metabolism were generally induced, while genes involved in other aspects of cellular growth were mostly repressed. A 7-kb eight-gene operon encoding a two-component regulatory system (2CRS), a transporter, an oxidoreductase, and four hypothetical proteins was significantly upregulated in the presence of bile. Deletion mutations were constructed in six genes of the operon. Transcriptional analysis of the 2CRS mutants showed that mutation of the histidine protein kinase (HPK) had no effect on the induction of the operon, whereas the mutated response regulator (RR) showed enhanced induction when the cells were exposed to bile. These results indicate that the 2CRS plays a role in bile tolerance and that the operon it resides in is negatively controlled by the RR. Mutations in the transporter, the HPK, the RR, and a hypothetical protein each resulted in loss of tolerance of bile. Mutations in genes encoding another hypothetical protein and a putative oxidoreductase resulted in significant increases in bile tolerance. This functional analysis showed that the operon encoded proteins involved in both bile tolerance and bile sensitivity.
DNA Helicase Activity of PcrA Is Not Required for the Displacement of RecA Protein from DNA or Inhibition of RecA-Mediated Strand Exchange
Authors: Anand Syam P. , Zheng Haocheng , Bianco Piero R. , Leuba Sanford H. , Khan Saleem A.
Published: April 2007

PcrA is a conserved DNA helicase present in all gram-positive bacteria. Bacteria lacking PcrA show high levels of recombination. Lethality induced by PcrA depletion can be overcome by suppressor mutations in the recombination genes
recFOR
. RecFOR proteins load RecA onto single-stranded DNA during recombination. Here we test whether an essential function of PcrA is to interfere with RecA-mediated DNA recombination in vitro. We demonstrate that PcrA can inhibit the RecA-mediated DNA strand exchange reaction in vitro. Furthermore, PcrA displaced RecA from RecA nucleoprotein filaments. Interestingly, helicase mutants of PcrA also displaced RecA from DNA and inhibited RecA-mediated DNA strand exchange. Employing a novel single-pair fluorescence resonance energy transfer-based assay, we demonstrate a lengthening of double-stranded DNA upon polymerization of RecA and show that PcrA and its helicase mutants can reverse this process. Our results show that the displacement of RecA from DNA by PcrA is not dependent on its translocase activity. Further, our results show that the helicase activity of PcrA, although not essential, might play a facilitatory role in the RecA displacement reaction.
pH-Dependent Association of Enolase and Glyceraldehyde-3-Phosphate Dehydrogenase ofLactobacillus crispatuswith the Cell Wall and Lipoteichoic Acids
Authors: Antikainen Jenni , Kupannen Veera , Lähteenmäki Kaarina , Korhonen Timo K.
Published: April 2007

The plasminogen-binding proteins enolase and glyceraldehyde-3-phosphate dehydrogenase ofLactobacillus crispatuswere localized on the cell surface at pH 5 but released into the medium at an alkaline pH. These proteins bound to lipoteichoic acids at a pH below their isoelectric point. The results indicate that lactobacilli rapidly modify their surface properties in response to changes in pH.
Localization of PcsB of
Streptococcus pneumoniae
and Its Differential Expression in Response to Stress
Authors: Mills Megumi F. , Marquart Mary E. , McDaniel Larry S.
Published: April 2007

PcsB of
Streptococcus pneumoniae
is an essential hydrolase involved in the separation of dividing cells. In this study, it was found that PcsB localizes to the plasma membrane and is released into the growth environment, yet it is detectable on the pneumococcal surface by flow cytometry analysis. High temperature and osmolarity led to upregulation of
pcsB
expression.
Translational Regulation of the
Escherichia coli
Stress Factor RpoS: a Role for SsrA and Lon
Authors: Ranquet Caroline , Gottesman Susan
Published: April 2007

Escherichia coli
cell viability during starvation is strongly dependent on the expression of the
rpoS
gene, encoding the RpoS sigma subunit of RNA polymerase. RpoS abundance has been reported to be regulated at many levels, including transcription initiation, translation, and protein stability. The regulatory RNA SsrA (or tmRNA) has both tRNA and mRNA activities, relieving ribosome stalling and cotranslationally tagging proteins. We report here that SsrA is needed for the correct high-level translation of RpoS. The ATP-dependent protease Lon was also found to negatively affect RpoS translation, but only at low temperature. We suggest that SsrA may indirectly improve RpoS translation by limiting ribosome stalling and depletion of some component of the translation machinery.
Molecular Characterization and Subcellular Localization of Macrophage Infectivity Potentiator, aChlamydia trachomatisLipoprotein
Authors: Neff Laurence , Daher Sawsan , Muzzin Patrick , Spenato Ursula , Gülaçar Fazil , Gabay Cem , Bas Sylvette
Published: April 2007

Macrophage infectivity potentiator (MIP) was originally reported to be a chlamydial lipoprotein from experiments showing incorporation of radiolabeled palmitic acid into native and recombinant MIP; inhibition of posttranslational processing of recombinant MIP by globomycin, known to inhibit signal peptidase II; and solubility of native MIP in Triton X-114. However, the detailed structural characterization of the lipid moiety on MIP has never been fully elucidated. In this study, bioinformatics and mass spectrometry analysis, as well as radiolabeling and immunochemical experiments, were conducted to further characterize MIP structure and subcellular localization. In silico analysis showed that the amino acid sequence of MIP is conserved across chlamydial species. A potential signal sequence with a contained lipobox was identified, and a recombinant C20A variant was prepared by replacing the probable lipobox cysteine with an alanine. Both incorporation of U-14C-esterified glycerol and [U-14C]palmitic acid and posttranslational processing that was inhibitable by globomycin were observed for recombinant wild-type MIP but not for the recombinant C20A MIP variant. The fatty acid contents of native and recombinant MIP were analyzed by gas chromatography-mass spectrometry, and the presence of amide-linked fatty acids in recombinant MIP was investigated by alkaline methanolysis. These results demonstrated a lipid modification in MIP similar to that of other prokaryotic lipoproteins. In addition, MIP was detected in an outer membrane preparation ofChlamydia trachomatiselementary bodies and was shown to be present at the surfaces of elementary bodies by surface biotinylation and surface immunoprecipitation experiments.
Analysis of the First Genome of a Hyperthermophilic Marine Virus-Like Particle, PAV1, Isolated fromPyrococcus abyssi
Authors: Geslin C. , Gaillard M. , Flament D. , Rouault K. , Le Romancer M. , Prieur D. , Erauso G.
Published: April 2007

Only one virus-like particle (VLP) has been reported from hyperthermophilicEuryarchaeotes. This VLP, named PAV1, is shaped like a lemon and was isolated from a strain of “Pyrococcus abyssi,” a deep-sea isolate. Its genome consists of a double-stranded circular DNA of 18 kb which is also present at a high copy number (60 per chromosome) free within the host cytoplasm but is not integrated into the host chromosome. Here, we report the results of complete analysis of the PAV1 genome. All the 25 predicted genes, except 3, are located on one DNA strand. A transcription map has been made by using a reverse transcription-PCR assay. All the identified open reading frames (ORFs) are transcribed. The most significant similarities relate to four ORFs. ORF 180a shows 31% identity with ORF 181 of the pRT1 plasmid isolated fromPyrococcussp. strain JT1. ORFs 676 and 678 present similarities with a concanavalin A-like lectin/glucanase domain, which could be involved in the process of host-virus recognition, and ORF 59 presents similarities with the transcriptional regulator CopG. The genome of PAV1 displays unique features at the nucleic and proteinic level, indicating that PAV1 should be attached at least to a novel genus or virus family.
Cryo-Electron Tomography Reveals the Comparative Three-Dimensional Architecture ofProchlorococcus, a Globally Important Marine Cyanobacterium
Authors: Ting Claire S. , Hsieh Chyongere , Sundararaman Sesh , Mannella Carmen , Marko Michael
Published: April 2007

In an age of comparative microbial genomics, knowledge of the near-native architecture of microorganisms is essential for achieving an integrative understanding of physiology and function. We characterized and compared the three-dimensional architecture of the ecologically important cyanobacteriumProchlorococcusin a near-native state using cryo-electron tomography and found that closely related strains have diverged substantially in cellular organization and structure. By visualizing native, hydrated structures within cells, we discovered that the MED4 strain, which possesses one of the smallest genomes (1.66 Mbp) of any known photosynthetic organism, has evolved a comparatively streamlined cellular architecture. This strain possesses a smaller cell volume, an attenuated cell wall, and less extensive intracytoplasmic (photosynthetic) membrane system compared to the more deeply branched MIT9313 strain. Comparative genomic analyses indicate that differences have evolved in key structural genes, including those encoding enzymes involved in cell wall peptidoglycan biosynthesis. Although both strains possess carboxysomes that are polygonal and cluster in the central cytoplasm, the carboxysomes of MED4 are smaller. A streamlined cellular structure could be advantageous to microorganisms thriving in the low-nutrient conditions characteristic of large regions of the open ocean and thus have consequences for ecological niche differentiation. Through cryo-electron tomography we visualized, for the first time, the three-dimensional structure of the extensive network of photosynthetic lamellae withinProchlorococcusand the potential pathways for intracellular and intermembrane movement of molecules. Comparative information on the near-native structure of microorganisms is an important and necessary component of exploring microbial diversity and understanding its consequences for function and ecology.
PmrA(Con) Confers
pmrHFIJKL
-Dependent EGTA and Polymyxin Resistance on
msbB Salmonella
by Decorating Lipid A with Phosphoethanolamine
Authors: Murray Sean R. , Ernst Robert K. , Bermudes David , Miller Samuel I. , Low K. Brooks
Published: April 2007

Mutations in
pmrA
were recombined into
Salmonella
strain ATCC 14028
msbB
to determine if
pmrA
-regulated modifications of lipopolysaccharide could suppress
msbB
growth defects. A mutation that functions to constitutively activate
pmrA
[
pmrA
(Con)] suppresses
msbB
growth defects on EGTA-containing media. Lipid A structural analysis showed that
Salmonella msbB pmrA
(Con) strains, compared to
Salmonella msbB
strains, have increased amounts of palmitate and phosphoethanolamine but no aminoarabinose addition, suggesting that aminoarabinose is not incorporated into
msbB
lipid A. Surprisingly, loss-of-function mutations in the aminoarabinose biosynthetic genes restored EGTA and polymyxin sensitivity to
Salmonella msbB pmrA
(Con) strains. These blocks in aminoarabinose biosynthesis also prevented lipid A phosphoethanolamine incorporation and reduced the levels of palmitate addition, indicating previously unknown roles for the aminoarabinose biosynthetic enzymes. Lipid A structural analysis of the EGTA- and polymyxin-resistant triple mutant
msbB pmrA
(Con)
pagP
::Tn
10
, which contains phosphoethanolamine but no palmitoylated lipid A, suggests that phosphoethanolamine addition is sufficient to confer EGTA and polymyxin resistance on
Salmonella msbB
strains. Additionally, palmitoylated lipid A was observed only in wild-type
Salmonella
grown in the presence of salt in rich media. Thus, we correlate EGTA resistance and polymyxin resistance with phosphoethanolamine-decorated lipid A and demonstrate that the aminoarabinose biosynthetic proteins play an essential role in lipid A phosphoethanolamine addition and affect lipid A palmitate addition in
Salmonella msbB
strains.
Reactions of Titanocene- and Zirconocene-Bis(trimethylsilyl)acetylene Complexes with Selected Heterocyclic and Aromatic NH and OH Acid Compounds
Authors: Arndt Perdita , Burlakov Vladimir V. , Jäger-Fiedler Ulrike , Klahn Marcus , Spannenberg Anke , Baumann Wolfgang , Rosenthal Uwe
Published: April 2007

The titanocene complexes Cp'2Ti(η2-Me3SiC2SiMe3) (Cp' = Cp (1), Cp* (2)) react with pyrrole under the formation of the titanium(III) mono-N-pyrrolides Cp'2Ti(NC4H4) (Cp' = Cp (6), Cp* (7)); whereas the corresponding zirconocene system Cp2Zr(η2-Me3SiC2SiMe3)(thf) (3) forms in a different reaction pathway first the Cp2Zr(NC4H4)[C(SiMe3)=CH(SiMe3)] (8) and then the zirconium(IV) bis-N-pyrrolide Cp2Zr(NC4H4)2 (11). With Cp*2Zr(η2-Me3SiC2SiMe3) (4) and pyrrole, the zirconium(IV) mono-N-pyrrolide with an agostic alkenyl group Cp*2Zr(NC4H4)[C(SiMe3)=CH(SiMe3)] (9) was obtained. In the reaction of the ethylenebistetrahydroindenyl (ebthi) complex rac-(ebthi)Zr(η2-Me3SiC2SiMe3) (5) with 2,3,5,6-tetrafluoroaniline under N-H bond activation, a complex with an agostic alkenyl group rac-(ebthi)Zr(NH-C6HF4)[C(SiMe3)=CH(SiMe3)] (10) was formed. Compound 10 reacts with additional 2,3,5,6-tetrafluoroaniline to give the bisanilide rac-(ebthi)Zr(NH-C6HF4)2 (12) which was obtained directly from 5 with two equivalents of 2,3,5,6-tetrafluoroaniline. In reactions of complex 5 with unsubstituted aniline to rac-(ebthi)Zr(NH-C6H5)2 (13) and with pentafluorophenol to bisphenolate rac-(ebthi)Zr(O-C6F5)2 (14), no intermediates could be isolated. The new reaction products 6, 9, 10, 12, 13 and 14 were investigated by X-ray crystallography.
Zinc and Cobalt(II) Complexes of Tripodal Nitrogen Ligands of the Tris[2-substituted Imidazol-4(5)-yl]phosphane Type. Biomimetic Hydrolysis of an Activated Ester
Authors: Kunz Peter C. , Kläui Wolfgang
Published: April 2007

Novel tris[2-substituted imidazol-4(5)-yl]phosphane (4-TIPR) ligands 2b (R = Ph) and 2c (R = tBu) were prepared as model ligands for the tris(histidine) motif found in many zinc enzymes. They readily form cobalt and zinc nitrato and chloro complexes in protic solvents. The steric requirements of the substituents R in 4(5)-position of the 4-TIPR ligands (R = iPr (2a), Ph (2b), tBu (2c)) is discussed on the basis of their UV/VIS spectra. Zinc complexes of 2a and 2c were studied due to their ability to promote the hydrolysis of the activated ester 4-nitrophenyl pyridine-2-carboxylate (pNpic).
Association between plasma BPDE-Alb adduct concentrations and DNA damage of peripheral blood lymphocytes among coke oven workers
Authors: Wang Hong , Chen Weihong , Zheng Hongyan , Guo Liang , Liang Huashan , Yang Xiaobo , Bai Yun , Sun Jianya , Su Yougong , Chen Yongwen , Yuan Jing , Bi Yongyi , Wei Qingyi , Wu Tangchun
Published: April 2007

Objectives:

Coke oven emissions COE containing polycyclic aromatic hydrocarbons PAHs can induce both benzoapyrene-r-7, t-8, t-9,c-10-tetrahydotetrol-albumin BPDE-Alb adducts and DNA damage. However, the relation between these biomarkers for early biological effects is not well documented in coke oven workers.

Methods:

In this study, the authors recruited 207 male workers exposed to COE and 102 controls not exposed to COE in the same steel plant in northern China. They measured BPDE-Alb adduct concentrations in plasma with reverse-phase high performance liquid chromatography and DNA damage in peripheral blood lymphocytes with alkaline comet assay.

Results:

The results showed that the median concentration of BPDE-Alb adducts in the exposed group 34.36 fmol/mg albumin was significantly higher than that in the control group 21.90 fmol/mg albumin, p0.012. The mean Olive tail moment Olive TM of DNA damage in the exposed and control groups were 1.20 and 0.63, respectively p0.000. Multivariate logistic regression analysis revealed that the odds ratio OR for BPDE-Alb adduct and Olive TM associated with the exposure were 1.72 95 CI 1.06 to 2.81 and 1.96 95 CI 1.20 to 3.19, respectively. These results show significant correlations between the concentrations of BPDE-Alb adduct and Olive TM levels in exposed group r0.235, p0.001 but not in control group r0.093, p0.353.

Conclusion:

The results suggest that occupational exposure to COE may induce both BPDEAlb adducts and DNA damage in the lymphocytes of coke oven workers and that these two markers are useful for monitoring exposure to COE in the workplace.
3-Hydroxybenzo[a]pyrene in the urine of workers with occupational exposure to polycyclic aromatic hydrocarbons in different industries
Authors: Förster K , Preuss R , Roßbach B , Brüning T , Angerer J , Simon P
Published: April 2007

Objectives:

This study was conducted to assess external and internal exposure of workers to polycyclic aromatic hydrocarbons (PAHs). In this context, the analytical and diagnostical reliability of 3-hydroxybenzo[a]pyrene (3OH-BaP) as a biomarker of internal exposure to PAHs was established.

Methods:

Ambient and biological monitoring was carried out of 225 PAH-exposed employees of different industries. External exposure was determined by personal air sampling and analysis of 16 EPA-PAH. Internal exposure was examined by the urinary metabolites 3OH-BaP, 1-hydroxypyrene (OH-Pyr) and monohydroxylated phenanthrenes (OH-Phens).

Results:

Benzo[a]pyrene (BaP) was detected at all workplaces. Concentrations in the breathing zone of the workers ranged from below the limit of detection up to 44.3 μg/m3. In biological monitoring, urinary 3OH-BaP was found in median concentrations of 0.8 ng/g creatinine (crea) and the 95th percentile of 6.7 ng/g crea. The results ranged from the limit of detection up to 19.5 ng/g crea. Only 1% of the analysed samples showed concentrations below the limit of detection (0.05 ng/l). Regarding median concentrations, workers in coking plants showed lower 3OH-BaP concentrations (0.5 ng/g crea) than those employed in the production of fireproof material in refractories (1.1 ng/g crea), converter infeed (1.2 ng/g crea) and graphite electrode production (1.3 ng/g crea). Strong correlations of 3OH-BaP with OH-Pyr and the sum of OH-Phens were found for the workplaces converter infeed, coking plants and graphite electrode production (rPearsonranging from 0.618 to 0.867, p<0.001). The poor correlation of BaP in the air and 3OH-BaP in urine is most probably caused by routes of uptake other than via air—for example, dermal uptake.

Conclusion:

3OH-BaP as a metabolite of the carcinogenic BaP could be shown to be a diagnostically specific and sensitive biomarker for determining the internal exposure of workers in different industries. Using this method, the estimation of health risks for workers can be fundamentally improved, because the 3OH-BaP represents the group of carcinogenic PAHs. The procedure for analysing 3OH-BaP is complex, but it is robust and produces reliable results.
Association of blood lead and homocysteine levels among lead exposed subjects in Vietnam and Singapore
Authors: Chia Sin Eng , Ali Safiyya Mohamed , Lee Bee Lan , Lim Gek Hsiang , Jin Su , Dong Nguyen-Viet , Tu Nguyen Thi Hong , Ong Choon Nam , Chia Kee Seng
Published: April 2007

Objectives:

Lead and homocysteine are both linked to cardiovascular disease. With this in mind, the authors evaluated the relation between blood lead and homocysteine in people aged 19–66 years in two Asian populations.

Methods:

This cross-sectional study comprised 183 workers from a lead stabiliser factory in Singapore and 323 workers from a battery factory in Vietnam. Workers were occupationally exposed to lead. Blood lead was analysed using atomic absorption spectrophotometry while plasma homocysteine was measured using high performance liquid chromatography.

Results:

Chinese subjects had the lowest blood lead levels while the Indians had the highest. Controlling for age, sex and race, an increase of 1 μg/dl in blood lead was associated with an increase of 0.04 μmol/l of homocysteine on the log scale. Gender and ethnicity seemed to be strongly associated with the relation between lead and homocysteine. The positive relation between lead and homocysteine among the Vietnamese subjects was significant (Pearson’s r = 0.254, p<0.01). When blood lead levels were divided by quartiles, the correlation coefficient between blood lead levels in the 4th quartile and homocysteine among the Vietnamese was higher (r = 0.405, p<0.01). Overall, an increase of 1 μg/dl in blood lead in all the Vietnamese subjects was associated with an increase of 0.05 μmol/l increase in homocysteine on the log scale. However, in the 4th quartile, the same increase was associated with an increase of 0.41 μmol/l of homocysteine on the log scale.

Conclusions:

Blood lead was found to be associated with homocysteine levels in this Asian sample. Although we cannot determine causality from cross-sectional data, it is sensible to consider the probability that this relation could explain one of the mechanisms of the impact of lead on the cardiovascular system. More studies would be needed to confirm this inference.
Follow-up study of chrysotile textile workers: cohort mortality and exposure-response
Authors: Hein Misty J , Stayner Leslie T , Lehman Everett , Dement John M
Published: April 2007

Objectives:This report provides an update of the mortality experience of a cohort of South Carolina asbestos textile workers.

Methods:A cohort of 3072 workers exposed to chrysotile in a South Carolina asbestos textile plant (1916–77) was followed up for mortality through 2001. Standardised mortality ratios (SMRs) were computed using US and South Carolina mortality rates. A job exposure matrix provided calendar time dependent estimates of chrysotile exposure concentrations. Poisson regression models were fitted for lung cancer and asbestosis. Covariates considered included sex, race, age, calendar time, birth cohort and time since first exposure. Cumulative exposure lags of 5 and 10 years were considered by disregarding exposure in the most recent 5 and 10 years, respectively.

Results:A majority of the cohort was deceased (64%) and 702 of the 1961 deaths occurred since the previous update. Mortality was elevated based on US referent rates for a priori causes of interest including all causes combined (SMR 1.33, 95% CI 1.28 to 1.39); all cancers (SMR 1.27, 95% CI 1.16 to 1.39); oesophageal cancer (SMR 1.87, 95% CI 1.09 to 2.99); lung cancer (SMR 1.95, 95% CI 1.68 to 2.24); ischaemic heart disease (SMR 1.20, 95% CI 1.10 to 1.32); and pneumoconiosis and other respiratory diseases (SMR 4.81, 95% CI 3.84 to 5.94). Mortality remained elevated for these causes when South Carolina referent rates were used. Three cases of mesothelioma were observed among cohort members. Exposure-response modelling for lung cancer, using a linear relative risk model, produced a slope coefficient of 0.0198 (fibre-years/ml) (standard error 0.00496), when cumulative exposure was lagged 10 years. Poisson regression modelling confirmed significant positive relations between estimated chrysotile exposure and lung cancer and asbestosis mortality observed in previous updates of this cohort.

Conclusions:This study confirms the findings from previous investigations of excess mortality from lung cancer and asbestosis and a strong exposure-response relation between estimated exposure to chrysotile and mortality from lung cancer and asbestosis.
Reducing healthy worker survivor bias by restricting date of hire in a cohort study of Vermont granite workers
Authors: Applebaum Katie M , Malloy Elizabeth J , Eisen Ellen A
Published: April 2007

Objective:

To explore the healthy worker survivor effect (HWSE) in a study of Vermont granite workers by distinguishing “prevalent” from “incident” hires based on date of hire before or after the start of follow-up.

Methods:

Records of workers between 1950 and 1982 were obtained from a medical surveillance programme. Proportional hazards models were used to model the association between silica exposure and lung cancer mortality, with penalised splines used to smooth the exposure-response relationship. A sensitivity analysis compared results between the original cohort and subcohorts defined by restricting date of hire to include varying proportions of prevalent hires.

Results:

Restricting to incident hires reduced the 213 cases by 74% and decreased the exposure range. The maximum mortality rate ratio (MRR) was close to twofold in all subcohorts. However, the exposure at which the maximum MRR was achieved decreased from 4.0 to 0.6 mg-year/m3as the proportion of prevalent hires decreased from 50% in the original cohort to 0% in the subcohort of incident hires.

Conclusion:

Despite loss in power and restricted exposure range, decreasing the relative proportion of prevalent to incident hires reduced HWSE bias, resulting in stronger evidence for a dose-response between silica exposure and lung cancer mortality.
Projected mesothelioma incidence in men in New South Wales
Authors: Clements Mark , Berry Geoffrey , Shi Jill , Ware Sandra , Yates Deborah , Johnson Anthony
Published: April 2007

Objectives:

Based on observed numbers of incident mesotheliomas since 1972, to predict future numbers in men in New South Wales.

Methods:

The incidence of mesothelioma was modelled in two ways. First by using an age/birth cohort model, and second by using a model based on potential exposure to asbestos in terms of age and calendar year. The latter model included a term for clearance of asbestos fibres from the lungs, and a term for diagnostic fraction. The age and calendar year model was based on the model introduced by Hodgson and colleagues but replaced piecewise effects by smooth functions represented by cubic splines.

Results:

The number of mesotheliomas between 2004 and 2060 was predicted as 6690 with the age-cohort model and as 6779 by the age and calendar year model, with peak annual numbers of 187 in the year 2021 and 196 in the year 2014 with the two models respectively.

Conclusions:

The pattern of parameter estimates in the two models was in accord with the known use of amphibole asbestos in Australia. The predicted peak year of 201421 is 3035 years after the phasing out of amphibole use, and this period is in accord with predictions for the UK and the US; in the latter country the peak was 1015 years earlier corresponding to a marked decline of amphibole use in and following the 1960s.
Gene-environment interactions in parkinsonism and Parkinson’s disease: the Geoparkinson study
Authors: Dick F D , De Palma G , Ahmadi A , Osborne A , Scott N W , Prescott G J , Bennett J , Semple S , Dick S , Mozzoni P , Haites N , Wettinger S Bezzina , Mutti A , Otelea M , Seaton A , Soderkvist P , Felice A
Published: April 2007

Objectives:

To investigate associations of Parkinson’s disease (PD) and parkinsonian syndromes with polymorphic genes that influence metabolism of either foreign chemical substances or dopamine and to seek evidence of gene-environment interaction effects that modify risk.

Methods:

A case-control study of 959 prevalent cases of parkinsonism (767 with PD) and 1989 controls across five European centres. Occupational hygienists estimated the average annual intensity of exposure to solvents, pesticides and metals, (iron, copper, manganese), blind to disease status.CYP2D6,PON1,GSTM1, GSTT1, GSTM3, GSTP1, NQO1, CYP1B1, MAO-A, MAO-B, SOD 2, EPHX,DAT1, DRD2andNAT2were genotyped. Results were analysed using multiple logistic regression adjusting for key confounders.

Results:

There was a modest but significant association betweenMAO-Apolymorphism in males and disease risk (G vs T, OR 1.30, 95% CI 1.02 to 1.66, adjusted). The majority of gene-environment analyses did not show significant interaction effects. There were possible interaction effects betweenGSTM1 nullgenotype and solvent exposure (which were stronger when limited to PD cases only).

Conclusions:

Many small studies have reported associations between genetic polymorphisms and PD. Fewer have examined gene-environment interactions. This large study was sufficiently powered to examine these aspects.GSTM1 nullsubjects heavily exposed to solvents appear to be at increased risk of PD. There was insufficient evidence that the other gene-environment combinations investigated modified disease risk, suggesting they contribute little to the burden of PD.
DYNAMICS OF A2 FINGER PULLEY RUPTURE
Authors: TAN MING A. , FUSS FRANZ K. , NIEGL GÜNTHER
Published: April 2007

A mathematical model of the A2 pulley system will enable us to have a better understanding of the mechanics of the pulley-tendon system and provide us with insights of the pulley rupture mechanism. The A2 pulley was modeled based on parallel pulley fibers attached to a phalanx with a tendon passing them. Mechanical properties of the pulleys such as stiffness, strength and friction were included in the model. A convergence test was done to ensure the accuracy of the test. The model managed to show high loads on flexed finger may lead to pulley ruptures. Further studies on the rupture mechanism showed that pulley ruptures are self-propagating when a constant force is applied and the rate of rupture increases, as fewer intact fibers are present to support the load. The initial rate of propagation is much slower and this accelerates as more fibers are ruptured. This explains the common occurrence of partial pulley ruptures.
Arrhythmia susceptibility and premature death in transgenic mice overexpressing both SUR1 and Kir6.2[ΔN30,K185Q] in the heart
Authors: Flagg Thomas P. , Patton Brian , Masia Ricard , Mansfield Carrie , Lopatin Anatoli N. , Yamada Kathryn A. , Nichols Colin G.
Published: April 2007

Sarcolemmal ATP-sensitive potassium (KATP) channels are activated after pathological depletion of intracellular ATP, unlike their pancreatic β-cell counterparts, which dynamically regulate membrane excitability in response to changes in blood glucose. We recently engineered a series of transgenic (TG) mice overexpressing an ATP-insensitive inward rectifying K+ channel protein (Kir)6.2 mutant (Kir6.2[ΔN30,K185Q]) or the accessory sulfonylurea receptor (SUR)2A (FLAG-SUR2A) or SUR1 (FLAG-SUR1) subunits of the KATP channel, under transcriptional control of the α-myosin heavy chain promoter. In the present study, we generated double transgenic (DTG) animals overexpressing both Kir6.2[ΔN30,K185Q] and FLAG-SUR1 or FLAG-SUR2A and examined the effects on cardiac excitability in vivo. No animals expressing both FLAG-SUR1 and Kir6.2[ΔN30,K185Q] transgenes at a high level were obtained. DTG mice expressing one transgene at a high level and the other at a lower level are born, but they die prematurely. Electrocardiographic analysis of both anesthetized and conscious animals revealed a constellation of arrhythmias in DTG animals, but not in wild-type or single TG littermates. The proarrhythmic effect of the transgene combination is intrinsic to the myocardium, since it persists in isolated hearts. Importantly, this effect is specific for SUR1-expressing DTG animals: DTG animals expressing both Kir6.2[ΔN30,K185Q] and FLAG-SUR2A at high levels exhibit neither impaired survival nor increased arrhythmia frequency, even with both subunits expressed at high levels. In demonstrating the profound arrhythmic consequences of KATP channels comprised of SUR1 and Kir6.2[ΔN30,K185Q] in the myocardium specifically, the results highlight the critical differential activation of SUR1 versus SUR2A, and indicate that expression of hyperactive KATP in the heart is likely to be proarrhythmic.