bluuebunny/crossref_metadata_2025_split huggingface dataset:
Psychometric Re‐evaluation of the Image of Science and Scientists Scale (ISSS)
Authors: Marshall Carolyn E. , Blalock Cheryl L. , Liu Yan , Pruski Linda A. , Toepperwein Mary Anne , Owen Steven V. , Lichtenstein Michael J. 
Published: March 2010

An enduring concern among science education researchers is the “swing away from science” (Osborne. 2003). One of their central dilemmas is to identify—or construct—a valid outcome measure that could assess curricular effectiveness, and predict students' choices of science courses, university majors, or careers in science. Many instruments have been created and variably evaluated. The primary purpose of this paper was to re‐evaluate the psychometric properties of the Image of Science and Scientists Scale (ISSS) (Krajkovich 1978).In the current study, confirmatory factor analysis (CFA) was used to examine the dimensionality of the 29‐item ISSS, which was administered to 531 middle school students in three San Antonio. Texas school districts at the beginning of the 2004–2005 school year. The results failed to confirm the presumed 1‐factor structure of the ISSS. but instead showed a 3‐factor structure with only marginal fit with the data, even after removal of 12 inadequate items. The three dimensions were “Positive Images of Scientists” (5 items). “Negative Images of Scientists” (9 items), and “Science Avocation” (3 items). The results do not support use of the original form of the ISSS for measuring “attitudes toward science,”“images of scientists. “or “scientific attitudes. “Shortening the scale from 29 to 17 items makes it more feasible to use in a classroom setting. Determining whether the three dimensions identified in our analysis. “Positive Images of Scientists. ““Negative Images of Scientists. “and “Science Avocation “contain useful assessments of middle school student impressions and attitudes will require independent investigation in other samples.
Sequences Essential for Transmission of
Spiroplasma citri
by Its Leafhopper Vector,
Circulifer haematoceps
, Revealed by Plasmid Curing and Replacement Based on Incompatibility
Authors: Breton Marc , Duret Sybille , Danet Jean-Luc , Dubrana Marie-Pierre , Renaudin Joël 
Published: March 2010

ABSTRACT

Spiroplasma citri
GII3 contains highly related low-copy-number plasmids pSci1 to -6. Despite the strong similarities between their replication regions, these plasmids coexist in the spiroplasma cells, indicating that they are mutually compatible. The pSci1 to -6 plasmids encode the membrane proteins known as
S. citri
adhesion-related proteins (ScARPs) (pSci1 to -5) and the hydrophilic protein P32 (pSci6), which had been tentatively associated with insect transmission, as they were not detected in non-insect-transmissible strains. With the aim of further investigating the role of plasmid-encoded determinants in insect transmission, we have constructed
S. citri
mutant strains that differ in their plasmid contents by developing a plasmid curing/replacement strategy based on the incompatibility of plasmids having identical replication regions. Experimental transmission of these
S. citri
plasmid mutants through injection into the leafhopper vector
Circulifer haematoceps
revealed that pSci6, more precisely, the pSci6_06 coding sequence, encoding a protein of unknown function, was essential for transmission. In contrast, ScARPs and P32 were dispensable for both acquisition and transmission of the spiroplasmas by the leafhopper vector, even though
S. citri
mutants lacking pSci1 to -5 (encoding ScARPs) were acquired and transmitted at lower efficiencies than the wild-type strain GII3.
Application of Molecular Techniques To Elucidate the Influence of Cellulosic Waste on the Bacterial Community Structure at a Simulated Low-Level-Radioactive-Waste Site
Authors: Field Erin K. , D'Imperio Seth , Miller Amber R. , VanEngelen Michael R. , Gerlach Robin , Lee Brady D. , Apel William A. , Peyton Brent M. 
Published: March 2010

ABSTRACT

Low-level-radioactive-waste (low-level-waste) sites, including those at various U.S. Department of Energy sites, frequently contain cellulosic waste in the form of paper towels, cardboard boxes, or wood contaminated with heavy metals and radionuclides such as chromium and uranium. To understand how the soil microbial community is influenced by the presence of cellulosic waste products, multiple soil samples were obtained from a nonradioactive model low-level-waste test pit at the Idaho National Laboratory. Samples were analyzed using 16S rRNA gene clone libraries and 16S rRNA gene microarray (PhyloChip) analyses. Both methods revealed changes in the bacterial community structure with depth. In all samples, the PhyloChip detected significantly more operational taxonomic units, and therefore relative diversity, than the clone libraries. Diversity indices suggest that diversity is lowest in the fill and fill-waste interface (FW) layers and greater in the wood waste and waste-clay interface layers. Principal-coordinate analysis and lineage-specific analysis determined that the
Bacteroidetes
and
Actinobacteria
phyla account for most of the significant differences observed between the layers. The decreased diversity in the FW layer and increased members of families containing known cellulose-degrading microorganisms suggest that the FW layer is an enrichment environment for these organisms. These results suggest that the presence of the cellulosic material significantly influences the bacterial community structure in a stratified soil system.
Mechanistic Aspects of Adenovirus Serotype 2 Inactivation with Free Chlorine
Authors: Page Martin A. , Shisler Joanna L. , Mariñas Benito J. 
Published: March 2010

ABSTRACT

Free chlorine is an effective disinfectant for controlling adenoviruses in drinking water, but little is known about the underlying inactivation mechanisms. The objective of this study was to elucidate the molecular components of adenovirus type 2 (Ad2) targeted by free chlorine during the inactivation process. The effects of free chlorine treatment on several Ad2 molecular components and associated life cycle events were compared to its effect on the ability of adenovirus to complete its life cycle, i.e., viability. Free chlorine treatment of Ad2 virions did not impair their ability to interact with monoclonal antibodies specific for hexon and fiber proteins of the Ad2 capsid, as measured by enzyme-linked immunosorbent assays, nor did it impair their interaction with recombinant, purified Coxsackie-adenovirus receptor (CAR) proteins
in vitro
. Free chlorine-treated Ad2 virions also retained their ability to bind to CAR receptors on A549 cell monolayers, despite being unable to form plaques, suggesting that free chlorine inactivates Ad2 by inhibiting a postbinding event of the Ad2 life cycle. DNA isolated from Ad2 virions that had been inactivated by free chlorine was able to be amplified by PCR, indicating that genome damage was not the cause of inactivation. However, inactivated Ad2 virions were unable to express E1A viral proteins during infection of A549 host cells, as measured by using immunoblotting. Collectively, these results indicate that free chlorine inactivates adenovirus by damaging proteins that govern life cycle processes occurring after host cell attachment, such as endocytosis, endosomal lysis, or nuclear delivery.
Abundance and Expression of Enantioselective
rdpA
and
sdpA
Dioxygenase Genes during Degradation of the Racemic Herbicide (
R
,
S
)-2-(2,4-Dichlorophenoxy)Propionate in Soil
Authors: Paulin Mélanie M. , Nicolaisen Mette H. , Sørensen Jan 
Published: March 2010

ABSTRACT

The
rdpA
and
sdpA
genes encode two enantioselective α-ketoglutarate-dependent dioxygenases catalyzing the initial step of microbial degradation of the chiral herbicide (
R
,
S
)-2-(2,4-dichlorophenoxy)propionate (
R
,
S
-dichlorprop). Primers were designed to assess abundance and transcription dynamics of
rdpA
and
sdpA
genes in a natural agricultural soil. No indigenous
rdpA
genes were detected, but
sdpA
genes were present at levels of approximately 10
3
copies g of soil
−1
. Cloning and sequencing of partial
sdpA
genes revealed a high diversity within the natural
sdpA
gene pool that could be divided into four clusters by phylogenetic analysis. BLASTp analysis of deduced amino acids revealed that members of cluster I shared 68 to 69% identity, cluster II shared 78 to 85% identity, cluster III shared 58 to 64% identity, and cluster IV shared 55% identity to their closest SdpA relative in GenBank. Expression of
rdpA
and
sdpA
in
Delftia acidovorans
MC1 inoculated in soil was monitored by reverse transcription quantitative real-time PCR (qPCR) during
in situ
degradation of 2 and 50 mg kg
−1
of (
R
,
S
)-dichlorprop. (
R
,
S
)-Dichlorprop amendment created a clear upregulation of both
rdpA
and
sdpA
gene expression during the active phase of
14
C-labeled (
R
,
S
)-dichlorprop mineralization, particularly following the second dose of 50 mg kg
−1
herbicide. Expression of both genes was maintained at a low constitutive level in nonamended soil microcosms. This study is the first to report the presence of indigenous
sdpA
genes recovered directly from natural soil and also comprises the first investigation into the transcription dynamics of two enantioselective dioxygenase genes during the
in situ
degradation of the herbicide (
R
,
S
)-dichlorprop in soil.
Systematic Evaluation of the Efficacy of Chlorine Dioxide in Decontamination of Building Interior Surfaces Contaminated with Anthrax Spores
Authors: Rastogi Vipin K. , Ryan Shawn P. , Wallace Lalena , Smith Lisa S. , Shah Saumil S. , Martin G. Blair 
Published: March 2010

ABSTRACT

Efficacy of chlorine dioxide (CD) gas generated by two distinct generation systems, Sabre (wet system with gas generated in water) and ClorDiSys (dry system with gas generated in air), was evaluated for inactivation of
Bacillus anthracis
spores on six building interior surfaces. The six building materials included carpet, acoustic ceiling tile, unpainted cinder block, painted I-beam steel, painted wallboard, and unpainted pinewood. There was no statistically significant difference in the data due to the CD generation technology at a 95% confidence level. Note that a common method of CD gas measurement was used for both wet and dry CD generation types. Doses generated by combinations of different concentrations of CD gas (500, 1,000, 1,500, or 3,000 parts per million of volume [ppmv]) and exposure times (ranging between 0.5 and 12 h) were used to evaluate the relative role of fumigant exposure period and total dose in the decontamination of building surfaces. The results showed that the time required to achieve at least a 6-log reduction in viable spores is clearly a function of the material type on which the spores are inoculated. The wood and cinder block coupons required a longer exposure time to achieve a 6-log reduction. The only material showing a clear statistical difference in rate of decay of viable spores as a function of concentration was cinder block. For all other materials, the profile of spore kill (i.e., change in number of viable spores with exposure time) was not dependent upon fumigant concentration (500 to 3,000 ppmv). The CD dose required for complete spore kill on biological indicators (typically, 1E6 spores of
B
acillus atrophaeus
on stainless steel) was significantly less than that required for decontamination of most of the building materials tested.
Role of Antioxidant Enzymes in Bacterial Resistance to Organic Acids
Authors: Bruno-Bárcena Jose M. , Azcárate-Peril M. Andrea , Hassan Hosni M. 
Published: March 2010

ABSTRACTGrowth in aerobic environments has been shown to generate reactive oxygen species (ROS) and to cause oxidative stress in most organisms. Antioxidant enzymes (i.e., superoxide dismutases and hydroperoxidases) and DNA repair mechanisms provide protection against ROS. Acid stress has been shown to be associated with the induction of Mn superoxide dismutase (MnSOD) inLactococcus lactisandStaphylococcus aureus. However, the relationship between acid stress and oxidative stress is not well understood. In the present study, we showed that mutations in the gene coding for MnSOD (sodA) increased the toxicity of lactic acid at pH 3.5 inStreptococcus thermophilus. The inclusion of the iron chelators 2,2′-dipyridyl (DIP), diethienetriamine-pentaacetic acid (DTPA), andO-phenanthroline (O-Phe) provided partial protection against 330 mM lactic acid at pH 3.5. The results suggested that acid stress triggers an iron-mediated oxidative stress that can be ameliorated by MnSOD and iron chelators. These findings were further validated inEscherichia colistrains lacking both MnSOD and iron SOD (FeSOD) but expressing a heterologous MnSOD fromS. thermophilus. We also found that, inE. coli, FeSOD did not provide the same protection afforded by MnSOD and that hydroperoxidases are equally important in protecting the cells against acid stress. These findings may explain the ability of some microorganisms to survive better in acidified environments, as in acid foods, during fermentation and accumulation of lactic acid or during passage through the low pH of the stomach.
Characterization of Triclosan-Resistant Mutants Reveals Multiple Antimicrobial Resistance Mechanisms in
Rhodospirillum rubrum
S1H
Authors: Pycke Benny F. G. , Crabbé Aurélie , Verstraete Willy , Leys Natalie 
Published: March 2010

ABSTRACT

Antimicrobial resistance mechanisms were identified in 11 spontaneous high- and low-level triclosan resistance (Tcs
r
) mutants of
Rhodospirillum rubrum
S1H by genotyping complemented with transcriptional analyses, antibiotic resistance screening, and membrane permeability analyses. High-end Tcs
r
(MIC = 8 mg/liter) was the result of a FabI1(G98V) mutation. This point mutation led to an even higher level of Tcs
r
(MIC ≥ 16 mg/liter) in combination with constitutive upregulation of
mexB
and
mexF
efflux pump homologs. Hence, a mechanistic synergy of constitutive efflux pump expression and a FabI1 point mutation could prevent TCS-induced cell permeabilization, which was shown to occur between 4 and 8 mg/liter TCS in the
R. rubrum
S1H parent strain. Low-level Tcs
r
mutants constitutively upregulated the
emrAB
,
mexAB
, and/or
mexF
homolog. The mutants that overexpressed
emrAB
also derepressed the micropollutant-upregulated factors
mufA1
and
mufM
. In some cases, low-level Tcs
r
decreased innate resistance to ampicillin and tetracycline, while in others, a triclosan-induced antibiotic cross-resistance was shown for chloramphenicol and carbenicillin. This study showed that the TCS resistance degree is dependent of the initial exposure concentration in
Rhodospirillum rubrum
S1H and that similar resistance degrees can be the result of different defense mechanisms, which all have distinct antibiotic cross-resistance profiles.
Denitrifying Bacteria Isolated from Terrestrial Subsurface Sediments Exposed to Mixed-Waste Contamination
Authors: Green Stefan J. , Prakash Om , Gihring Thomas M. , Akob Denise M. , Jasrotia Puja , Jardine Philip M. , Watson David B. , Brown Steven D. , Palumbo Anthony V. , Kostka Joel E. 
Published: March 2010

ABSTRACT

In terrestrial subsurface environments where nitrate is a critical groundwater contaminant, few cultivated representatives are available to verify the metabolism of organisms that catalyze denitrification. In this study, five species of denitrifying bacteria from three phyla were isolated from subsurface sediments exposed to metal radionuclide and nitrate contamination as part of the U.S. Department of Energy's Oak Ridge Integrated Field Research Challenge (OR-IFRC). Isolates belonged to the genera
Afipia
and
Hyphomicrobium
(
Alphaproteobacteria
),
Rhodanobacter
(
Gammaproteobacteria
),
Intrasporangium
(
Actinobacteria
), and
Bacillus
(
Firmicutes
). Isolates from the phylum
Proteobacteria
were complete denitrifiers, whereas the Gram-positive isolates reduced nitrate to nitrous oxide. rRNA gene analyses coupled with physiological and genomic analyses suggest that bacteria from the genus
Rhodanobacter
are a diverse population of denitrifiers that are circumneutral to moderately acidophilic, with a high relative abundance in areas of the acidic source zone at the OR-IFRC site. Based on genome analysis,
Rhodanobacter
species contain two nitrite reductase genes and have not been detected in functional-gene surveys of denitrifying bacteria at the OR-IFRC site. Nitrite and nitrous oxide reductase gene sequences were recovered from the isolates and from the terrestrial subsurface by designing primer sets mined from genomic and metagenomic data and from draft genomes of two of the isolates. We demonstrate that a combination of cultivation and genomic and metagenomic data is essential to the
in situ
characterization of denitrifiers and that current PCR-based approaches are not suitable for deep coverage of denitrifiers. Our results indicate that the diversity of denitrifiers is significantly underestimated in the terrestrial subsurface.
A Plasmodium falciparum Transcriptional Cyclin-Dependent Kinase-Related Kinase with a Crucial Role in Parasite Proliferation Associates with Histone Deacetylase Activity
Authors: Halbert Jean , Ayong Lawrence , Equinet Leila , Le Roch Karine , Hardy Mary , Goldring Dean , Reininger Luc , Waters Norman , Chakrabarti Debopam , Doerig Christian 
Published: March 2010

ABSTRACT

Cyclin-dependent protein kinases (CDKs) are key regulators of the eukaryotic cell cycle and of the eukaryotic transcription machinery. Here we report the characterization of Pfcrk-3 (
Plasmodium falciparum
CDK-related kinase 3; PlasmoDB identifier PFD0740w), an unusually large CDK-related protein whose kinase domain displays maximal homology to those CDKs which, in other eukaryotes, are involved in the control of transcription. The closest enzyme in
Saccharomyces cerevisiae
is BUR1 (
b
ypass
u
pstream activating sequence
r
equirement 1), known to control gene expression through interaction with chromatin modification enzymes. Consistent with this, immunofluorescence data show that Pfcrk-3 colocalizes with histones. We show that recombinant Pfcrk-3 associates with histone H1 kinase activity in parasite extracts and that this association is detectable even if the catalytic domain of Pfcrk-3 is rendered inactive by site-directed mutagenesis, indicating that Pfcrk-3 is part of a complex that includes other protein kinases. Immunoprecipitates obtained from extracts of transgenic parasites expressing hemagglutinin (HA)-tagged Pfcrk-3 by using an anti-HA antibody displayed both protein kinase and histone deacetylase activities. Reverse genetics data show that the
pfcrk-3
locus can be targeted only if the genetic modification does not cause a loss of function. Taken together, our data strongly suggest that Pfcrk-3 fulfils a crucial role in the intraerythrocytic development of
P. falciparum
, presumably through chromatin modification-dependent regulation of gene expression.
Abundant 5S rRNA-Like Transcripts Encoded by the Mitochondrial Genome in Amoebozoa
Authors: Bullerwell Charles E. , Burger Gertraud , Gott Jonatha M. , Kourennaia Olga , Schnare Murray N. , Gray Michael W. 
Published: March 2010

ABSTRACT

5S rRNAs are ubiquitous components of prokaryotic, chloroplast, and eukaryotic cytosolic ribosomes but are apparently absent from mitochondrial ribosomes (mitoribosomes) of many eukaryotic groups including animals and fungi. Nevertheless, a clearly identifiable, mitochondrion-encoded 5S rRNA is present in
Acanthamoeba castellanii
, a member of Amoebozoa. During a search for additional mitochondrial 5S rRNAs, we detected small abundant RNAs in other members of Amoebozoa, namely, in the lobose amoeba
Hartmannella vermiformis
and in the myxomycete slime mold
Physarum polycephalum
. These RNAs are encoded by mitochondrial DNA (mtDNA), cosediment with mitoribosomes in glycerol gradients, and can be folded into a secondary structure similar to that of bona fide 5S rRNAs. Further, in the mtDNA of another slime mold,
Didymium nigripes
, we identified a region that in sequence, potential secondary structure, and genomic location is similar to the corresponding region encoding the
Physarum
small RNA. A mtDNA-encoded small RNA previously identified in
Dictyostelium discoideum
is here shown to share several characteristics with known 5S rRNAs. Again, we detected genes encoding potential homologs of this RNA in the mtDNA of three other species of the genus
Dictyostelium
as well as in a related genus,
Polysphondylium
. Taken together, our results indicate a widespread occurrence of small, abundant, mtDNA-encoded RNAs with 5S rRNA-like structures that are associated with the mitoribosome in various amoebozoan taxa. Our working hypothesis is that these novel small abundant RNAs represent radically divergent mitochondrial 5S rRNA homologs. We posit that currently unrecognized 5S-like RNAs may exist in other mitochondrial systems in which a conventional 5S rRNA cannot be identified.
Fungal Homoserine Kinase (
thr1
Δ) Mutants Are Attenuated in Virulence and Die Rapidly upon Threonine Starvation and Serum Incubation
Authors: Kingsbury Joanne M. , McCusker John H. 
Published: March 2010

ABSTRACT

The fungally conserved subset of amino acid biosynthetic enzymes not present in humans offer exciting potential as an unexploited class of antifungal drug targets. Since threonine biosynthesis is essential in
Cryptococcus neoformans
, we further explored the potential of threonine biosynthetic enzymes as antifungal drug targets by determining the survival in mice of
Saccharomyces cerevisiae
homoserine kinase (
thr1
Δ) and threonine synthase (
thr4
Δ) mutants. In striking contrast to aspartate kinase (
hom3
Δ) mutants,
S. cerevisiae
thr1
Δ and
thr4
Δ mutants were severely depleted after only 4 h
in vivo
. Similarly,
Candida albicans
thr1
Δ mutants, but not
hom3
Δ mutants, were significantly attenuated in virulence. Consistent with the
in vivo
phenotypes,
S. cerevisiae
thr1
Δ and
thr4
Δ mutants as well as
C. albicans
thr1
Δ mutants were extremely serum sensitive. In both species, serum sensitivity was suppressed by the addition of threonine, a feedback inhibitor of Hom3p. Because mutation of the
HOM3
and
HOM6
genes, required for the production of the toxic pathway intermediate homoserine, also suppressed serum sensitivity, we hypothesize that serum sensitivity is a consequence of homoserine accumulation. Serum survival is critical for dissemination, an important virulence determinant: thus, together with the essential nature of
C. neoformans
threonine synthesis, the cross-species serum sensitivity of
thr1
Δ mutants makes the fungus-specific Thr1p, and likely Thr4p, ideal antifungal drug targets.