bluuebunny/crossref_metadata_2025_split huggingface dataset:
Origins of the Recent Emergence of
Plasmodium falciparum
Pyrimethamine Resistance Alleles in Madagascar
Authors: Andriantsoanirina Valérie , Bouchier Christiane , Tichit Magali , Jahevitra Martial , Rabearimanana Stéphane , Randrianjafy Rogelin , Ratsimbasoa Arsène , Mercereau-Puijalon Odile , Durand Rémy , Ménard Didier 
Published: March 2010

ABSTRACT

The combination of sulfadoxine-pyrimethamine is recommended for use as intermittent preventive treatment of malaria during pregnancy and is deployed in Africa. The emergence and the spread of resistant parasites are major threats to such an intervention. We have characterized the
Plasmodium falciparum
dhfr
(
pfdhfr
) haplotypes and flanking microsatellites in 322
P. falciparum
isolates collected from the Comoros Islands and Madagascar. One hundred fifty-six (48.4%) carried the wild-type
pfdhfr
allele, 19 (5.9%) carried the S108N single-mutation allele, 30 (9.3%) carried the I164L single-mutation allele, 114 (35.4%) carried the N51I/C59R/S108N triple-mutation allele, and 3 (1.0%) carried the N51I/C59R/S108N/I164L quadruple-mutation allele. Microsatellite analysis showed the introduction from the Comoros Islands of the ancestral
pfdhfr
triple mutant allele of Asian origin and its spread in Madagascar. Evidence for the emergence on multiple occasions of the I164L single-mutation
pfdhfr
allele in Madagascar was also obtained. Thus, the conditions required to generate mutants with quadruple mutations are met in Madagascar, representing a serious threat to current drug policy.
In Vitro
Activity of ACH-702, a New Isothiazoloquinolone, against
Nocardia brasiliensis
Compared with Econazole and the Carbapenems Imipenem and Meropenem Alone or in Combination with Clavulanic Acid
Authors: Vera-Cabrera Lucio , Campos-Rivera Mayra Paola , Escalante-Fuentes Wendy G. , Pucci Michael J. , Ocampo-Candiani Jorge , Welsh Oliverio 
Published: March 2010

ABSTRACT

The
in vitro
activities of ACH-702 and other antimicrobials against 30
Nocardia brasiliensis
isolates were tested. The MIC
50
(MIC for 50% of the strains tested) and MIC
90
values of ACH-702 were 0.125 and 0.5 μg/ml. The same values for econazole were 2 and 4 μg/ml. The MIC
50
and MIC
90
values of imipenem and meropenem were 64 and >64 μg/ml and 2 and 8 μg/ml, respectively; the addition of clavulanic acid to the carbapenems had no effect.
Plasmodium
vivax
Susceptibility to Ferroquine
Authors: Leimanis M. L. , Jaidee A. , Sriprawat K. , Kaewpongsri S. , Suwanarusk R. , Barends M. , Phyo A. P. , Russell B. , Renia L. , Nosten F. 
Published: March 2010

ABSTRACT

The novel organometallic chloroquine analog ferroquine (SSR 97193) is effective against chloroquine-resistant
Plasmodium
falciparum
. The
ex
vivo
efficacy of ferroquine against
Plasmodium
vivax
isolates was tested. Ferroquine has a potent
ex
vivo
effect on
P
.
vivax
schizont maturation (median 50% inhibitory concentration, 15 nM;
n
= 42). No significant cross-sensitivity between ferroquine and other antimalarials was detected. This drug may be a suitable replacement for chloroquine in the treatment of drug-resistant
P
.
vivax
malaria.
The M230L Nonnucleoside Reverse Transcriptase Inhibitor Resistance Mutation in HIV-1 Reverse Transcriptase Impairs Enzymatic Function and Viral Replicative Capacity
Authors: Xu Hong-Tao , Quan Yudong , Schader Susan M. , Oliveira Maureen , Bar-Magen Tamara , Wainberg Mark A. 
Published: March 2010

ABSTRACT
The M230L mutation in HIV-1 reverse transcriptase (RT) is associated with resistance to first-generation nonnucleoside reverse transcriptase inhibitors (NNRTIs). The present study was designed to determine the effects of M230L on enzyme function, viral replication capacity (RC), and the extent to which M230L might confer resistance to the second-generation NNRTI etravirine (ETR) as well as to the first-generation NNRTIs efavirenz (EFV) and nevirapine (NVP). Phenotyping assays with TZM-bl cells confirmed that M230L conferred various degrees of resistance to each of the NNRTIs tested. Recombinant viruses containing M230L displayed an 8-fold decrease in RC compared to that of the parental wild-type (WT) virus. Recombinant HIV-1 WT and M230L mutant RT enzymes were purified; and both biochemical and cell-based phenotypic assays confirmed that M230L conferred resistance to each of EFV, NVP, and ETR. RT that contained M230L was also deficient in regard to each of minus-strand DNA synthesis, both DNA- and RNA-dependent polymerase activities, processivity, and RNase H activity, suggesting that this mutation contributes to diminished viral replication kinetics.
Lepidopteran-Active Variable-Region Sequence Imparts Coleopteran Activity in eCry3.1Ab, an Engineered
Bacillus thuringiensis
Hybrid Insecticidal Protein
Authors: Walters Frederick S. , deFontes Cheryl M. , Hart Hope , Warren Gregory W. , Chen Jeng S. 
Published: March 2010

ABSTRACT

A unique, coleopteran-active protein, termed eCry3.1Ab, was generated following variable-region exchange of a
Bacillus thuringiensis
lepidopteran-active protein, Cry1Ab, with a Cry3A region. Our results support the hypothesis that this variable-region exchange is responsible for imparting strong bioactivity against the larvae of western corn rootworm (WCR) (
Diabrotica virgifera virgifera
LeConte), a pest species which is not susceptible to either parent protein sequence. This study demonstrates the potential of successfully engineering a portion(s) of a lepidopteran-active
B. thuringiensis
sequence so that it has activity against coleopterans. Further elucidation of the eCry3.1Ab activity indicated the importance of variable regions 4 to 6 that were derived from Cry1Ab instead of Cry1Ac. There was some flexibility in making domain III of engineered hybrid insecticidal proteins even more Cry1Ab-like and retaining activity, while there was less flexibility in making domain III more Cry3A-like and retaining activity.
In vitro
binding studies with brush border membrane vesicles demonstrated that there was specific binding of chymotrypsin-processed modified Cry3A (mCry3A), which was not diminished by addition of a 100-fold molar excess of chymotrypsin-processed eCry3.1Ab or unprocessed eCry3.1Ab. In addition, in the converse experiment, specific binding of chymotrypsin-processed eCry3.1Ab was not diminished by the presence of a 75-fold molar excess of chymotrypsin-processed mCry3A. These data support the hypothesis that eCry3.1Ab can interact with different binding sites than the activated form of mCry3A in the WCR brush border and may provide a different mode of action from the standpoint of resistance management.
Heterologous Expression of Mutated Eburicol 14α-Demethylase (CYP51) Proteins of
Mycosphaerella graminicola
To Assess Effects on Azole Fungicide Sensitivity and Intrinsic Protein Function
Authors: Cools H. J. , Parker J. E. , Kelly D. E. , Lucas J. A. , Fraaije B. A. , Kelly S. L. 
Published: March 2010

ABSTRACT

The recent decrease in the sensitivity of the Western European population of the wheat pathogen
Mycosphaerella graminicola
to azole fungicides has been associated with the emergence and subsequent spread of mutations in the
CYP51
gene, encoding the azole target sterol 14α-demethylase. In this study, we have expressed wild-type and mutated
M. graminicola
CYP51 (MgCYP51) variants in a
Saccharomyces cerevisiae
mutant carrying a doxycycline-regulatable

tetO
7

-
CYC
promoter controlling native
CYP51
expression. We have shown that the wild-type MgCYP51 protein complements the function of the orthologous protein in
S. cerevisiae
. Mutant MgCYP51 proteins containing amino acid alterations L50S, Y459D, and Y461H and the two-amino-acid deletion ΔY459/G460, commonly identified in modern
M. graminicola
populations, have no effect on the capacity of the
M. graminicola
protein to function in
S. cerevisiae
. We have also shown that the azole fungicide sensitivities of transformants expressing MgCYP51 variants with these alterations are substantially reduced. Furthermore, we have demonstrated that the I381V substitution, correlated with the recent decline in the effectiveness of azoles, destroys the capacity of
MgCYP51
to complement the
S. cerevisiae
mutant when introduced alone. However, when I381V is combined with changes between residues Y459 and Y461, the function of the
M. graminicola
protein is partially restored. These findings demonstrate, for the first time for a plant pathogenic fungus, the impacts that naturally occurring CYP51 alterations have on both azole sensitivity and intrinsic protein function. In addition, we also provide functional evidence underlying the order in which CYP51 alterations in the Western European
M. graminicola
population emerged.
Succession of the Bacterial Community and Dynamics of Hydrogen Producers in a Hydrogen-Producing Bioreactor
Authors: Huang Yue , Zong Wenming , Yan Xing , Wang Ruofan , Hemme Christopher L. , Zhou Jizhong , Zhou Zhihua 
Published: March 2010

ABSTRACT

Variation in the hydrogen production rate was consistent with the succession of dominant bacteria during the batch fermentation process. Denaturing gradient gel electrophoresis (DGGE) of 16S rRNA genes and quantitative analysis of the
hyd
A
genes at both the DNA and mRNA levels confirmed that
C
lostridium perfringens
was the most dominant hydrogen producer in the bioreactor.
Anaerobic Oxidation of Fatty Acids and Alkenes by the Hyperthermophilic Sulfate-Reducing ArchaeonArchaeoglobus fulgidus
Authors: Khelifi Nadia , Grossi Vincent , Hamdi Moktar , Dolla Alain , Tholozan Jean-Luc , Ollivier Bernard , Hirschler-Réa Agnès 
Published: March 2010

ABSTRACTArchaeoglobus fulgidusoxidizes fatty acids (C4to C18) andn-alk-1-enes (C12:1to C21:1) in the presence of thiosulfate as a terminal electron acceptor. End products of metabolism were CO2and sulfide. Growth on perdeuterated hexadecene yielded C15- to C17-labeled fatty acids as metabolites, thus confirming the ability ofA. fulgidusto oxidize alkyl chains.
Homoserine Toxicity in Saccharomyces cerevisiae and Candida albicans Homoserine Kinase (
thr1
Δ) Mutants
Authors: Kingsbury Joanne M. , McCusker John H. 
Published: March 2010

ABSTRACT

In addition to threonine auxotrophy, mutation of the
Saccharomyces cerevisiae
threonine biosynthetic genes
THR1
(encoding homoserine kinase) and
THR4
(encoding threonine synthase) results in a plethora of other phenotypes. We investigated the basis for these other phenotypes and found that they are dependent on the toxic biosynthetic intermediate homoserine. Moreover, homoserine is also toxic for
Candida albicans
thr1
Δ mutants. Since increasing levels of threonine, but not other amino acids, overcome the homoserine toxicity of
thr1
Δ mutants, homoserine may act as a toxic threonine analog. Homoserine-mediated lethality of
thr1
Δ mutants is blocked by cycloheximide, consistent with a role for protein synthesis in this lethality. We identified various proteasome and ubiquitin pathway components that either when mutated or present in high copy numbers suppressed the
thr1
Δ mutant homoserine toxicity. Since the
doa4
Δ and proteasome mutants identified have reduced ubiquitin- and/or proteasome-mediated proteolysis, the degradation of a particular protein or subset of proteins likely contributes to homoserine toxicity.
Inflammatory Cytokine Response to
Bacillus anthracis
Peptidoglycan Requires Phagocytosis and Lysosomal Trafficking
Authors: Iyer Janaki K. , Khurana Taruna , Langer Marybeth , West Christopher M. , Ballard Jimmy D. , Metcalf Jordan P. , Merkel Tod J. , Coggeshall K. Mark 
Published: March 2010

ABSTRACT

During advanced stages of inhalation anthrax,
Bacillus anthracis
accumulates at high levels in the bloodstream of the infected host. This bacteremia leads to sepsis during late-stage anthrax; however, the mechanisms through which
B. anthracis
-derived factors contribute to the pathology of infected hosts are poorly defined. Peptidoglycan, a major component of the cell wall of Gram-positive bacteria, can provoke symptoms of sepsis in animal models. We have previously shown that peptidoglycan of
B. anthracis
can induce the production of proinflammatory cytokines by cells in human blood. Here, we show that biologically active peptidoglycan is shed from an active culture of encapsulated
B. anthracis
strain Ames in blood. Peptidoglycan is able to bind to surfaces of responding cells, and internalization of peptidoglycan is required for the production of inflammatory cytokines. We also show that the peptidoglycan traffics to lysosomes, and lysosomal function is required for cytokine production. We conclude that peptidoglycan of
B. anthracis
is initially bound by an unknown extracellular receptor, is phagocytosed, and traffics to lysosomes, where it is degraded to a product recognized by an intracellular receptor. Binding of the peptidoglycan product to the intracellular receptor causes a proinflammatory response. These findings provide new insight into the mechanism by which
B. anthracis
triggers sepsis during a critical stage of anthrax disease.
Lack of Interleukin-12 in p40-Deficient Mice Leads to Poor CD8+T-Cell Immunity againstEncephalitozoon cuniculiInfection
Authors: Moretto Magali M. , Lawlor Elizabeth M. , Khan Imtiaz A. 
Published: March 2010

ABSTRACTA CD8+T-cell response is critical for protection againstEncephalitozoon cuniculiinfection. However, the factors responsible for the generation of CD8+T-cell immunity duringE. cuniculiinfection and the cytokines involved in this process have not been identified. In the present study, we demonstrated that p40-deficient animals, which are unable to produce interleukin-12 (IL-12), have a serious defect in expansion of the CD8+T-cell response which compromises the survival of an infected host. Adoptive transfer of CD8+T cells from immunocompetent donors protected SCID mice infected withE. cuniculi, whereas administration of CD8+T cells from p40−/−mice failed to protect infected SCID mice.In vitrodendritic cell (DC) cultures from knockout mice pulsed withE. cuniculispores were unable to develop a robust CD8+T-cell immune response. Addition of exogenous IL-12 or transfer of CD8+T cells that were initially primed with DC from p40−/−animals to DC cultures from immunocompetent mice (directly or via transwells) led to optimal expansion of these cells. This IL-12-mediated reinstatement of CD8+T-effector immunity was independent of gamma interferon (IFN-γ) as addition of antibody to the cultures failed to have an effect. These studies demonstrated that IL-12 plays a predominant role in the expansion of effector CD8+T-cell immunity againstE. cuniculi, which is critical for host survival. These findings are very important for understanding the protective immune mechanisms needed to protect an immunocompromised host against an opportunistic infection and can be extended to other microsporidial pathogens.
Potent Neutralization of Staphylococcal Enterotoxin B by Synergistic Action of Chimeric Antibodies
Authors: Tilahun Mulualem E. , Rajagopalan Govindarajan , Shah-Mahoney Nalini , Lawlor Rebecca G. , Tilahun Ashenafi Y. , Xie Chen , Natarajan Kannan , Margulies David H. , Ratner David I. , Osborne Barbara A. , Goldsby Richard A. 
Published: March 2010

ABSTRACTStaphylococcal enterotoxin B (SEB), a shock-inducing exotoxin synthesized byStaphylococcus aureus, is an important cause of food poisoning and is a class B bioterrorism agent. SEB mediates antigen-independent activation of a major subset of the T-cell population by cross-linking T-cell receptors (TCRs) with class II major histocompatibility complex (MHC-II) molecules of antigen-presenting cells, resulting in the induction of antigen independent proliferation and cytokine secretion by a significant fraction of the T-cell population. Neutralizing antibodies inhibit SEB-mediated T-cell activation by blocking the toxin's interaction with the TCR or MHC-II and provide protection against the debilitating effects of this superantigen. We derived and searched a set of monoclonal mouse anti-SEB antibodies to identify neutralizing anti-SEB antibodies that bind to different sites on the toxin. A pair of non-cross-reactive, neutralizing anti-SEB monoclonal antibodies (MAbs) was found, and a combination of these antibodies inhibited SEB-induced T-cell proliferation in a synergistic rather than merely additive manner. In order to engineer antibodies more suitable than mouse MAbs for use in humans, the genes encoding the VL and VH gene segments of a synergistically acting pair of mouse MAbs were grafted, respectively, onto genes encoding the constant regions of human Igκ and human IgG1, transfected into mammalian cells, and used to generate chimeric versions of these antibodies that had affinity and neutralization profiles essentially identical to their mouse counterparts. When tested in cultures of human peripheral blood mononuclear cells or splenocytes derived from HLA-DR3 transgenic mice, the chimeric human-mouse antibodies synergistically neutralized SEB-induced T-cell activation and cytokine production.
Trimer Stability of YadA Is Critical for Virulence of
Yersinia enterocolitica
Authors: Schütz M. , Weiss E.-M. , Schindler M. , Hallström T. , Zipfel P. F. , Linke D. , Autenrieth I. B. 
Published: March 2010

ABSTRACT

Yersinia
adhesin A (YadA) is a trimeric autotransporter adhesin with multiple functions in host-pathogen interactions. The aim of this study was to dissect the virulence functions promoted by YadA
in vitro
and
in vivo
. To accomplish this, we generated
Yersinia enterocolitica
O:8 mutants expressing point mutations in YadA G389, a highly conserved residue in the membrane anchor of YadA, and analyzed their impact on YadA expression and virulence functions. We found that point mutations of YadA G389 led to impaired transport, stability, and surface display of YadA. YadA G389A and G389S mutants showed comparable YadA surface expression, autoagglutination, and adhesion to those of wild-type YadA but displayed reduced trimer stability and complement resistance
in vitro
and were 10- to 1,000-fold attenuated in experimental
Y. enterocolitica
infection in mice. The G389T, G389N, and G389H mutants lost trimer stability, exhibited strongly reduced surface display, autoagglutination, adhesion properties, and complement resistance, and were avirulent (>10,000-fold attenuation) in mice. Our data demonstrate that G389 is a critical residue of YadA, required for optimal trimer stability, transport, surface display, and serum resistance. We also show that stable trimeric YadA protein is essential for virulence of
Y. enterocolitica
.
Characterization of thePseudomonas aeruginosaTranscriptional Response to Phenylalanine and Tyrosine
Authors: Palmer Gregory C. , Palmer Kelli L. , Jorth Peter A. , Whiteley Marvin 
Published: March 2010

ABSTRACTPseudomonas aeruginosais a Gram-negative opportunistic pathogen often associated with chronic infections in the lungs of individuals with the heritable disease cystic fibrosis (CF). Previous work from our laboratory demonstrated that aromatic amino acids within CF lung secretions (sputum) not only serve as carbon and energy sources but also enhance synthesis of the cell signaling moleculePseudomonasquinolone signal (PQS). The present study investigates the role of the aromatic amino acid-responsive regulator PhhR in mediating these phenotypes. Transcriptome analysis revealed that PhhR controls four putative transcriptional units (phhA,hpd,hmgA, anddhcA) involved in aromatic amino acid catabolism; however, genes involved in PQS biosynthesis were unaffected. ThephhA,hpd,hmgA, anddhcApromoters were mapped by primer extension, and purified His6-PhhR was shown to bind thephhA,hpd, anddhcApromotersin vitroby use of electrophoretic mobility shift assays. Our work characterizes a transcriptional regulator of catabolic genes induced duringP. aeruginosagrowth in CF sputum.
Evidence of Localized Prophage-Host Recombination in the
lytA
Gene, Encoding the Major Pneumococcal Autolysin
Authors: Morales María , García Pedro , de la Campa Adela G. , Liñares Josefina , Ardanuy Carmen , García Ernesto 
Published: March 2010

ABSTRACT

According to a highly polymorphic region in the
lytA
gene, encoding the major autolysin of
Streptococcus pneumoniae
, two different families of alleles can be differentiated by PCR and restriction digestion. Here, we provide evidence that this polymorphic region arose from recombination events with homologous genes of pneumococcal temperate phages.
Differential Regulation of the Multiple Flagellins in Spirochetes
Authors: Li Chunhao , Sal Melanie , Marko Michael , Charon Nyles W. 
Published: March 2010

ABSTRACTThe expression of flagellin genes in most bacteria is typically regulated by the flagellum-specific sigma28factor FliA, and an anti-sigma28factor, FlgM. However, the regulatory hierarchy in several bacteria that have multiple flagellins is more complex. In these bacteria, the flagellin genes are often transcribed by at least two different sigma factors. The flagellar filament in spirochetes consists of one to three FlaB core proteins and at least one FlaA sheath protein. Here, the genetically amenable bacteriumBrachyspira hyodysenteriaewas used as a model spirochete to investigate the regulation of its four flagellin genes,flaA,flaB1,flaB2, andflaB3. We found that theflaB1andflaB2genes are regulated by sigma28, whereas theflaAandflaB3genes are controlled by sigma70. The analysis of a flagellar motor switchfliGmutant further supported this proposition; in the mutant, the transcription offlaB1andflaB2was inhibited, but that offlaAandflaB3was not. In addition, the continued expression offlaAandflaB3in the mutant resulted in the formation of incomplete flagellar filaments that were hollow tubes and consisted primarily of FlaA. Finally, our recent studies have shown that each flagellin unit contributes to the stiffness of the periplasmic flagella, and this stiffness directly correlates with motility. The regulatory mechanism identified here should allow spirochetes to change the relative ratio of these flagellin proteins and, concomitantly, vary the stiffness of their flagellar filament.
The Actinomycin Biosynthetic Gene Cluster ofStreptomyces chrysomallus: a Genetic Hall of Mirrors for Synthesis of a Molecule with Mirror Symmetry
Authors: Keller Ullrich , Lang Manuel , Crnovcic Ivana , Pfennig Frank , Schauwecker Florian 
Published: March 2010

ABSTRACTA gene cluster was identified which contains genes involved in the biosynthesis of actinomycin encompassing 50 kb of contiguous DNA on the chromosome ofStreptomyces chrysomallus. It contains 28 genes with biosynthetic functions and is bordered on both sides by IS elements. Unprecedentedly, the cluster consists of two large inverted repeats of 11 and 13 genes, respectively, with four nonribosomal peptide synthetase genes in the middle. Nine genes in each repeat have counterparts in the other, in the same arrangement but in the opposite orientation, suggesting an inverse duplication of one of the arms during the evolution of the gene cluster. All of the genes appear to be organized into operons, each corresponding to a functional section of actinomycin biosynthesis, such as peptide assembly, regulation, resistance, and biosynthesis of the precursor of the actinomycin chromophore 4-methyl-3-hydroxyanthranilic acid (4-MHA). For 4-MHA synthesis, functional analysis revealed genes that encode pathway-specific isoforms of tryptophan dioxygenase, kynurenine formamidase, and hydroxykynureninase, which are distinct from the corresponding enzyme activities of cellular tryptophan catabolism in their regulation and in part in their substrate specificity. Phylogenetic analysis indicates that the pathway-specific tryptophan metabolism inStreptomycesmost probably evolved divergently from the normal pathway of tryptophan catabolism to provide an extra or independent supply of building blocks for the synthesis of tryptophan-derived secondary metabolites.