bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of the Liaison Automated Testing System for Diagnosis of Congenital Toxoplasmosis
Authors: Prusa Andrea-Romana , Hayde Michael , Pollak Arnold , Herkner Kurt R. , Kasper David C. 
Published: September 2012

ABSTRACTCongenital toxoplasmosis is a worldwide health problem, and different screening strategies exist. Testing of toxoplasma-specific antibodies in infants identifies congenital toxoplasmosis during the first year of life. However, experience with commercial available immunoassays is limited. The aim of this study was to evaluate both the performance and analytical characteristics of the Liaison diagnostic system in infants. In a retrospective study, serumToxoplasma gondiiantibodies were measured in samples from 333 infants, including 212 noninfected infants and 121 infants with congenital toxoplasmosis. A total of 1,157 umbilical cord blood and peripheral serum samples were analyzed. Liaison toxoplasma-specific IgG and IgM antibodies and the IgG avidity index were compared to the infection status of the infant, determined by the Sabin-Feldman dye test and immunosorbent agglutination assay—IgM. All noninfected infants were seronegative by Liaison IgG within the first year of life. The Liaison system showed a sensitivity of 81.8%, a specificity of 100.0%, a positive predictive value of 100.0%, a negative predictive value of 90.6%, and overall agreement of 84.4% by comparison with the dye test. Overall agreement of both IgM test systems was 96.0%. In this study cohort, avidity did not show a potential diagnostic benefit for the detection of congenital infection. In conclusion, the Liaison system is a valuable tool to monitor the serologic course of infants at risk. A final serologic confirmatory test is recommended to improve the rate of detection of congenital toxoplasmosis at 1 year of life. Protocols of routine follow-up testing in infants and accurate diagnostic tools after acute gestational infections are needed to improve medical care.
Sudden Oak Death: Interactions of the Exotic Oomycete Phytophthora ramorum with Naïve North American Hosts
Authors: Garbelotto Matteo , Hayden Katherine J. 
Published: September 2012

ABSTRACT

Ten years after a threatening and previously unknown disease of oaks and tanoaks appeared in coastal California, a significant amount of progress has been made toward the understanding of its causal agent
Phytophthora ramorum
and of the novel pathosystems associated with this exotic organism. However, a complete understanding of the ecology and epidemiology of this species still eludes us. In part, our inability to fully understand this organism is due to its phylogenetic, phylogeographic, phenotypic, and epidemiological complexities, all reviewed in this paper. Most lines of evidence suggest that the high degree of disease severity reported in California is not simply due to a generalized lack of resistance or tolerance in naïve hosts but also to an innate ability of the pathogen to survive in unfavorable climatic conditions and to reproduce rapidly when conditions become once again favorable.
The SWI/SNF KlSnf2 Subunit Controls the Glucose Signaling Pathway To Coordinate Glycolysis and Glucose Transport in Kluyveromyces lactis
Authors: Cotton Pascale , Soulard Alexandre , Wésolowski-Louvel Micheline , Lemaire Marc 
Published: September 2012

ABSTRACT

In
Kluyveromyces lactis
, the expression of the major glucose permease gene
RAG1
is controlled by extracellular glucose through a signaling cascade similar to the
Saccharomyces cerevisiae
Snf3/Rgt2/Rgt1 pathway. We have identified a key component of the
K. lactis
glucose signaling pathway by characterizing a new mutation,
rag20-1
, which impairs the regulation of
RAG1
and hexokinase
RAG5
genes by glucose. Functional complementation of the
rag20-1
mutation identified the
KlSNF2
gene, which encodes a protein 59% identical to
S. cerevisiae
Snf2, the major subunit of the SWI/SNF chromatin remodeling complex. Reverse transcription-quantitative PCR and chromatin immunoprecipitation analyses confirmed that the KlSnf2 protein binds to
RAG1
and
RAG5
promoters and promotes the recruitment of the basic helix-loop-helix Sck1 activator. Besides this transcriptional effect, KlSnf2 is also implicated in the glucose signaling pathway by controlling Sms1 and KlRgt1 posttranscriptional modifications. When KlSnf2 is absent, Sms1 is not degraded in the presence of glucose, leading to constitutive
RAG1
gene repression by KlRgt1. Our work points out the crucial role played by KlSnf2 in the regulation of glucose transport and metabolism in
K. lactis
, notably, by suggesting a link between chromatin remodeling and the glucose signaling pathway.
Pseudohyphal Growth of Cryptococcus neoformans Is a Reversible Dimorphic Transition in Response to Ammonium That Requires Amt1 and Amt2 Ammonium Permeases
Authors: Lee Soo Chan , Phadke Sujal , Sun Sheng , Heitman Joseph 
Published: September 2012

ABSTRACTCryptococcus neoformansis a human-pathogenic basidiomycete that commonly infects HIV/AIDS patients to cause meningoencephalitis (7, 19).C. neoformansgrows as a budding yeast during vegetative growth or as hyphae during sexual reproduction. Pseudohyphal growth ofC. neoformanshas been observed rarely during murine and human infections but frequently during coculture with amoeba; however, the genetics underlying pseudohyphal growth are largely unknown. Our studies found thatC. neoformansdisplays pseudohyphal growth under nitrogen-limiting conditions, especially when a small amount of ammonium is available as a sole nitrogen source. Pseudohyphal growth was observed withCryptococcus neoformansserotypes A and D andCryptococcus gattii. C. neoformanspseudohyphae bud to produce yeast cells and normal smooth hemispherical colonies when transferred to complete media, indicating that pseudohyphal growth is a conditional developmental stage. Subsequent analysis revealed that two ammonium permeases encoded by theAMT1andAMT2genes are required for pseudohyphal growth. Bothamt1andamt2mutants are capable of forming pseudohyphae; however,amt1 amt2double mutants do not form pseudohyphae. Interestingly,C. gattiipseudohypha formation is irreversible and involves a RAM pathway mutation that drives pseudohyphal development. We also found that pseudohyphal growth is related to the invasive growth into the medium. These results demonstrate that pseudohyphal growth is a common reversible growth pattern inC. neoformansbut a mutational genetic event inC. gattiiand provide new insights into understanding pseudohyphal growth ofCryptococcus.
The Putative Guanine Nucleotide Exchange Factor RicA Mediates Upstream Signaling for Growth and Development in Aspergillus
Authors: Kwon Nak-Jung , Park Hee-Soo , Jung Seunho , Kim Sun Chang , Yu Jae-Hyuk 
Published: September 2012

ABSTRACT

Heterotrimeric G proteins (G proteins) govern growth, development, and secondary metabolism in various fungi. Here, we characterized
ricA
, which encodes a putative GDP/GTP exchange factor for G proteins in the model fungus
Aspergillus nidulans
and the opportunistic human pathogen
Aspergillus fumigatus
. In both species,
ricA
mRNA accumulates during vegetative growth and early developmental phases, but it is not present in spores. The deletion of
ricA
results in severely impaired colony growth and the total (for
A. nidulans
) or near (for
A. fumigatus
) absence of asexual sporulation (conidiation). The overexpression (OE) of the
A. fumigatus ricA
gene (Af
ricA
) restores growth and conidiation in the ΔAn
ricA
mutant to some extent, indicating partial conservation of RicA function in
Aspergillus
. A series of double mutant analyses revealed that the removal of RgsA (an RGS protein of the GanB Gα subunit), but not
sfgA
,
flbA
,
rgsB
, or
rgsC
, restored vegetative growth and conidiation in ΔAn
ricA
. Furthermore, we found that RicA can physically interact with GanB in yeast and
in vitro
. Moreover, the presence of two copies or OE of
pkaA
suppresses the profound defects caused by ΔAn
ricA
, indicating that RicA-mediated growth and developmental signaling is primarily through GanB and PkaA in
A. nidulans
. Despite the lack of conidiation,
brlA
and
vosA
mRNAs accumulated to normal levels in the Δ
ricA
mutant. In addition, mutants overexpressing
fluG
or
brlA
(OE
fluG
or OE
brlA
) failed to restore development in the ΔAn
ricA
mutant. These findings suggest that the commencement of asexual development requires unknown RicA-mediated signaling input in
A. nidulans
.
Wall Teichoic Acids Restrict Access of Bacteriophage Endolysin Ply118, Ply511, and PlyP40 Cell Wall Binding Domains to the Listeria monocytogenes Peptidoglycan
Authors: Eugster Marcel R. , Loessner Martin J. 
Published: September 2012

ABSTRACTThe C-terminal cell wall binding domains (CBDs) of phage endolysins direct the enzymes to their binding ligands on the bacterial cell wall with high affinity and specificity. TheListeria monocytogenesPly118, Ply511, and PlyP40 endolysins feature related CBDs which recognize the directly cross-linked peptidoglycan backbone structure ofListeria. However, decoration with fluorescently labeled CBDs primarily occurs at the poles and septal regions of the rod-shaped cells. To elucidate the potential role of secondary cell wall-associated carbohydrates such as the abundant wall teichoic acid (WTA) on this phenomenon, we investigated CBD binding usingL. monocytogenesserovar 1/2 and 4 cells deficient in WTA. Mutants were obtained by deletion of two redundanttagOhomologues, whose products catalyze synthesis of the WTA linkage unit. While inactivation of eithertagO1(EGDelmo0959) ortagO2(EGDelmo2519) alone did not affect WTA content, removal of both alleles following conditional complementation yielded WTA-deficientListeriacells. Substitution oftagOfrom an isopropyl-β-d-thiogalactopyranoside-inducible single-copy integration vector restored the original phenotype. Although WTA-deficient cells are viable, they featured severe growth inhibition and an unusual coccoid morphology. In contrast to CBDs from otherListeriaphage endolysins which directly utilize WTA as binding ligand, the data presented here show that WTAs are not required for attachment of CBD118, CBD511, and CBDP40. Instead, lack of the cell wall polymers enables unrestricted spatial access of CBDs to the cell wall surface, indicating that the abundant WTA can negatively regulate sidewall localization of the cell wall binding domains.
Construction and Characterization of a Derivative of Neisseria gonorrhoeae Strain MS11 Devoid of All
opa
Genes
Authors: LeVan Adriana , Zimmerman Lindsey I. , Mahle Amanda C. , Swanson Karen V. , DeShong Philip , Park Juhee , Edwards Vonetta L. , Song Wenxia , Stein Daniel C. 
Published: September 2012

ABSTRACT
To better understand the role of Opa in gonococcal infections, we created and characterized a derivative of MS11 (MS11Δopa) that had the coding sequence for all 11 Opa proteins deleted. The MS11Δopa bacterium lost the ability to bind to purified lipooligosaccharide (LOS). While nonpiliated MS11Δopa and nonpiliated Opa-expressing MS11 cells grew at the same rate, nonpiliated MS11Δopa cells rarely formed clumps of more than four bacteria when grown in broth with vigorous shaking. Using flow cytometry analysis, we demonstrated that MS11Δopa produced a homogeneous population of bacteria that failed to bind monoclonal antibody (MAb) 4B12, a MAb specific for Opa. Opa-expressing MS11 cells consisted of two predominant populations, where ∼85% bound MAb 4B12 to a significant level and the other population bound little if any MAb. Approximately 90% of bacteria isolated from a phenotypically Opa-negative colony (a colony that does not refract light) failed to bind MAb 4B12; the remaining 10% bound MAb to various degrees. Piliated MS11Δopa cells formed dispersed microcolonies on ME180 cells which were visually distinct from those of piliated Opa-expressing MS11 cells. When Opa expression was reintroduced into MS11Δopa, the adherence ability of the strain recovered to wild-type levels. These data indicate that Opa contributes to both bacterium-bacterium and bacterium-host cell interactions.
Mycobacterium tuberculosis CwsA Interacts with CrgA and Wag31, and the CrgA-CwsA Complex Is Involved in Peptidoglycan Synthesis and Cell Shape Determination
Authors: Plocinski P. , Arora N. , Sarva K. , Blaszczyk E. , Qin H. , Das N. , Plocinska R. , Ziolkiewicz M. , Dziadek J. , Kiran M. , Gorla P. , Cross T. A. , Madiraju M. , Rajagopalan M. 
Published: September 2012

ABSTRACT

Bacterial cell division and cell wall synthesis are highly coordinated processes involving multiple proteins. Here, we show that Rv0008c, a novel small membrane protein from
Mycobacterium tuberculosis
, localizes to the poles and on membranes and shows an overall punctate localization throughout the cell. Furthermore, Rv0008c interacts with two proteins, CrgA and Wag31, implicated in peptidoglycan (PG) synthesis in mycobacteria. Deletion of the Rv0008c homolog in
M. smegmatis
, MSMEG_0023, caused bulged cell poles, formation of rounded cells, and defects in polar localization of Wag31 and cell wall synthesis, with cell wall synthesis measured by the incorporation of the [
14
C]
N
-acetylglucosamine cell wall precursor. The
M. smegmatis
MSMEG_0023
crgA
double mutant strain showed severe defects in growth, viability, cell wall synthesis, cell shape, and the localization of the FtsZ, FtsI, and Wag31 proteins. The double mutant strain also exhibited increased autolytic activity in the presence of detergents. Because CrgA and Wag31 proteins interact with FtsI individually, we believe that regulated cell wall synthesis and cell shape maintenance require the concerted actions of the CrgA, Rv0008c, FtsI, and Wag31 proteins. We propose that, together, CrgA and Rv0008c, renamed CwsA for
c
ell
w
all synthesis and cell
s
hape protein
A
, play crucial roles in septal and polar PG synthesis and help coordinate these processes with the FtsZ-ring assembly in mycobacteria.
A MarR-Type Regulator Directly Activates Transcription from the Brucella abortus virB Promoter by Sharing a Redundant Role with HutC
Authors: Sieira Rodrigo , Arocena Gastón M. , Zorreguieta Angeles , Comerci Diego J. , Ugalde Rodolfo A. 
Published: September 2012

ABSTRACT

Type IV secretion systems (T4SS) are multiprotein structures that direct the translocation of specific molecules across the bacterial cell envelope. As in other bacteria, pathogenicity of the genus
Brucella
essentially depends on the integrity of the T4SS-encoding
virB
operon, whose expression is regulated by multiple transcription factors belonging to different families. Previously, we identified IHF and HutC, two direct regulators of the
virB
genes that were isolated from total protein extracts of
Brucella
. Here, we report the identification of MdrA, a third regulatory element that was isolated using the same screening procedure. This transcription factor, which belongs to the MarR-family of transcriptional regulators, binds at two different sites of the
virB
promoter and regulates expression in a growth phase-dependent manner. Like other members of the MarR family, specific ligands were able to dissociate MdrA from DNA
in vitro
. Determination of the MdrA-binding sites by DNase I footprinting and analyses of protein-DNA complexes by electrophoresis mobility shift assays (EMSAs) showed that MdrA competes with IHF and HutC for the binding to the promoter because their target DNA sequences overlap. Unlike IHF, both MdrA and HutC bound to the promoter without inducing bending of DNA. Moreover, the two latter transcription factors activated
virB
expression to similar extents, and in doing so, they are functionally redundant. Taken together, our results show that MdrA is a regulatory element that directly modulates the activity of the
virB
promoter and is probably involved in coordinating gene expression in response to specific environmental signals.
Upregulation of the Phthiocerol Dimycocerosate Biosynthetic Pathway by Rifampin-Resistant,rpoBMutant Mycobacterium tuberculosis
Authors: Bisson Gregory P. , Mehaffy Carolina , Broeckling Corey , Prenni Jessica , Rifat Dalin , Lun Desmond S. , Burgos Marcos , Weissman Drew , Karakousis Petros C. , Dobos Karen 
Published: September 2012

ABSTRACTMultidrug-resistant tuberculosis has emerged as a major threat to tuberculosis control. Phylogenetically related rifampin-resistant actinomycetes with mutations mapping to clinically dominantMycobacterium tuberculosismutations in therpoBgene show upregulation of gene networks encoding secondary metabolites. We compared the expressed proteomes and metabolomes of two fully drug-susceptible clinical strains ofM. tuberculosis(wild type) to those of their respective rifampin-resistant,rpoBmutant progeny strains with confirmed rifampin monoresistance following antitubercular therapy. Each of these strains was also used to infect gamma interferon- and lipopolysaccharide-activated murine J774A.1 macrophages to analyze transcriptional responses in a physiologically relevant model. BothrpoBmutants showed significant upregulation of the polyketide synthase genesppsA-ppsEanddrrA, which constitute an operon encoding multifunctional enzymes involved in the biosynthesis of phthiocerol dimycocerosate and other lipids inM. tuberculosis, but also of various secondary metabolites in related organisms, including antibiotics, such as erythromycin and rifamycins.ppsA(Rv2931),ppsB(Rv2932), andppsC(Rv2933) were also found to be upregulated more than 10-fold in the BeijingrpoBmutant strain relative to its wild-type parent strain during infection of activated murine macrophages. In addition, metabolomics identified precursors of phthiocerol dimycocerosate, but not the intact molecule itself, in greater abundance in bothrpoBmutant isolates. These data suggest thatrpoBmutation inM. tuberculosismay trigger compensatory transcriptional changes in secondary metabolism genes analogous to those observed in related actinobacteria. These findings may assist in developing novel methods to diagnose and treat drug-resistantM. tuberculosisinfections.
Genetic and Biochemical Characterizations of Enzymes Involved in Streptococcus pneumoniae Serotype 2 Capsule Synthesis Demonstrate that Cps2T (WchF) Catalyzes the Committed Step by Addition of β1-4 Rhamnose, the Second Sugar Residue in the Repeat Unit
Authors: James David B. A. , Yother Janet 
Published: September 2012

ABSTRACT

Five genes (
cps2E
,
cps2T
,
cps2F
,
cps2G
, and
cps2I
) are predicted to encode the glycosyltransferases responsible for synthesis of the
Streptococcus pneumoniae
serotype 2 capsule repeat unit, which is polymerized to yield a branched surface structure containing glucose-glucuronic acid linked to a glucose-rhamnose-rhamnose-rhamnose backbone. Cps2E is the initiating glycosyltransferase, but experimental evidence supporting the functions of the remaining glycosyltransferases is lacking. To biochemically characterize the glycosyltransferases, the donor substrate dTDP-rhamnose was first synthesized using recombinant
S. pneumoniae
enzymes Cps2L, Cps2M, Cps2N, and Cps2O. In
in vitro
assays with each of the glycosyltransferases, only reaction mixtures containing recombinant Cps2T, dTDP-rhamnose, and the Cps2E product (undecaprenyl pyrophosphate glucose) generated a new product, which was consistent with lipid-linked glucose-rhamnose.
cps2T
,
cps2F
, and
cps2I
deletion mutants produced no detectable capsule, but trace amounts of capsule were detectable in Δ
cps2G
mutants, suggesting that Cps2G adds a nonbackbone sugar. All Δ
cps2F
, Δ
cps2G
, and Δ
cps2I
mutants contained different secondary suppressor mutations in
cps2E
, indicating that the initial mutations were lethal in the absence of reduced repeat unit synthesis. Δ
cps2T
mutants did not contain secondary mutations affecting capsule synthesis. The requirement for secondary mutations in mutants lacking Cps2F, Cps2G, and Cps2I indicates that these activities occur downstream of the committed step in capsule synthesis and reveal that Cps2T catalyzes this step. Therefore, Cps2T is the β1-4 rhamnosyltransferase that adds the second sugar to the repeat unit and, as the committed step in type 2 repeat unit synthesis, is predicted to be an important point of capsule regulation.
Iron-Regulated Surface Determinant (Isd) Proteins of Staphylococcus lugdunensis
Authors: Zapotoczna Marta , Heilbronner Simon , Speziale Pietro , Foster Timothy J. 
Published: September 2012

ABSTRACT

Staphylococcus lugdunensis
is the only coagulase-negative
Staphylococcus
species with a locus encoding iron-regulated surface determinant (Isd) proteins. In
Staphylococcus aureus
, the Isd proteins capture heme from hemoglobin and transfer it across the wall to a membrane-bound transporter, which delivers it into the cytoplasm, where heme oxygenases release iron. The Isd proteins of
S. lugdunensis
are expressed under iron-restricted conditions. We propose that
S. lugdunensis
IsdB and IsdC proteins perform the same functions as those of
S. aureus
.
S. lugdunensis
IsdB is the only hemoglobin receptor within the
isd
locus. It specifically binds human hemoglobin with a dissociation constant (

K
d

) of 23 nM and transfers heme on IsdC. IsdB expression promotes bacterial growth in an iron-limited medium containing human hemoglobin but not mouse hemoglobin. This correlates with weak binding of IsdB to mouse hemoglobin
in vitro
. Unlike IsdB and IsdC, the proteins IsdJ and IsdK are not sorted to the cell wall in
S. lugdunensis
. In contrast, IsdJ expressed in
S. aureus
and
Lactococcus lactis
is anchored to peptidoglycan, suggesting that
S. lugdunensis
sortases may differ in signal recognition or could be defective. IsdJ and IsdK are present in the culture supernatant, suggesting that they could acquire heme from the external milieu. The IsdA protein of
S. aureus
protects bacteria from bactericidal lipids due to its hydrophilic C-terminal domain. IsdJ has a similar region and protected
S. aureus
and
L. lactis
as efficiently as IsdA but, possibly due to its location, was less effective in its natural host.
Fur Activates Expression of the 2-Oxoglutarate Oxidoreductase Genes (
oorDABC
) in Helicobacter pylori
Authors: Gilbreath Jeremy J. , West Abby L. , Pich Oscar Q. , Carpenter Beth M. , Michel Sarah , Merrell D. Scott 
Published: September 2012

ABSTRACT

Helicobacter pylori
is a highly successful pathogen that colonizes the gastric mucosa of ∼50% of the world's population. Within this colonization niche, the bacteria encounter large fluctuations in nutrient availability. As such, it is critical that this organism regulate expression of key metabolic enzymes so that they are present when environmental conditions are optimal for growth. One such enzyme is the 2-oxoglutarate (α-ketoglutarate) oxidoreductase (OOR), which catalyzes the conversion of α-ketoglutarate to succinyl coenzyme A (succinyl-CoA) and CO
2
. Previous studies from our group suggested that the genes that encode the OOR are activated by iron-bound Fur (Fe-Fur); microarray analysis showed that expression of
oorD
,
oorA
, and
oorC
was altered in a
fur
mutant strain of
H. pylori.
The goal of the present work was to more thoroughly characterize expression of the
oorDABC
genes in
H. pylori
as well as to define the role of Fe-Fur in this process. Here we show that these four genes are cotranscribed as an operon and that expression of the operon is decreased in a
fur
mutant strain. Transcriptional start site mapping and promoter analysis revealed the presence of a canonical extended −10 element but a poorly conserved −35 element upstream of the +1. Additionally, we identified a conserved Fur binding sequence ∼130 bp upstream of the transcriptional start site. Transcriptional analysis using promoter fusions revealed that this binding sequence was required for Fe-Fur-mediated activation. Finally, fluorescence anisotropy assays indicate that Fe-Fur specifically bound this Fur box with a relatively high affinity (dissociation constant [

K
d

] = 200 nM). These findings provide novel insight into the genetic regulation of a key metabolic enzyme and add to our understanding of the diverse roles Fur plays in gene regulation in
H. pylori
.