bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cryptosporidium
spp. in Wild, Laboratory, and Pet Rodents in China: Prevalence and Molecular Characterization
Authors: Lv Chaochao , Zhang Longxian , Wang Rongjun , Jian Fuchun , Zhang Sumei , Ning Changshen , Wang Helei , Feng Chao , Wang Xinwei , Ren Xupeng , Qi Meng , Xiao Lihua 
Published: October 2009

ABSTRACT

To understand the prevalence of
Cryptosporidium
infection in rodents in China and to assess the potential role of rodents as a source for human cryptosporidiosis, 723 specimens from 18 rodent species were collected from four provinces of China and examined between August 2007 and December 2008 by microscopy after using Sheather's sugar flotation and modified acid-fast staining.
Cryptosporidium
oocysts were detected in 83 specimens, with an overall prevalence of 11.5%.
Phodopus sungorus
,
Phodopus campbelli
, and
Rattus tanezumi
were new reported hosts of
Cryptosporidium
. The genotypes and subtypes of
Cryptosporidium
strains in microscopy-positive specimens were further identified by PCR and sequence analysis of the small subunit rRNA and the 60-kDa glycoprotein (gp60) genes. In addition to
Cryptosporidium parvum
,
C. muris
,
C. andersoni
,
C. wrairi
, ferret genotype, and mouse genotype I, four new
Cryptosporidium
genotypes were identified, including the hamster genotype, chipmunk genotype III, and rat genotypes II and III. Mixed
Cryptosporidium
species/genotypes were found in 10.8% of
Cryptosporidium
-positive specimens. Sequence analysis of the gp60 gene showed that
C. parvum
strains in pet Siberian chipmunks and hamsters were all of the subtype IIdA15G1, which was found previously in a human isolate in The Netherlands and lambs in Spain. The gp60 sequences of
C. wrairi
and the
Cryptosporidium
ferret genotype and mouse genotype I were also obtained. These findings suggest that pet rodents may be potential reservoirs of zoonotic
Cryptosporidium
species and subtypes.
Assessment of Dust Sampling Methods for the Study of Cultivable-Microorganism Exposure in Stables
Authors: Normand Anne-Cécile , Vacheyrou Mallory , Sudre Bertrand , Heederik Dick J. J. , Piarroux Renaud 
Published: October 2009

ABSTRACT

Studies have shown a link between living on a farm, exposure to microbial components (e.g., endotoxins or β-
d
-glucans), and a lower risk for allergic diseases and asthma. Due to the lack of validated sampling methods, studies of asthma and atopy have not relied on exposure assessment based on culture techniques. Our objective was therefore to compare several dust sampling methods for the detection of cultivable-microorganism exposure in stables. Sixteen French farms were sampled using four different methods: (i) active air sampling using a pump, (ii) passive dust sampling with a plastic box, (iii) dust sampling with an electrostatic dust fall collector (wipe), and (iv) dust sampling using a spatula to collect dust already settled on a windowsill. The results showed that collection of settled dust samples with either plastic boxes or wipes was reproducible (pairwise correlations, 0.72 and 0.73, respectively) and resulted in highly correlated results (pairwise correlation between the two methods, 0.82). We also found that settled dust samples collected with a plastic box correctly reflected the composition of the samples collected in the air of the stable when there was no farmer activity. A loss of microbial diversity was observed when dust was kept for 3 months at room temperature. We therefore conclude that measurement of viable microorganisms within a reasonable time frame gives an accurate representation of the microbial composition of stable air.
Rehosting of Bacterial Chaperones for High-Quality Protein Production
Authors: Martínez-Alonso Mónica , Toledo-Rubio Verónica , Noad Rob , Unzueta Ugutz , Ferrer-Miralles Neus , Roy Polly , Villaverde Antonio 
Published: October 2009

ABSTRACTCoproduction of DnaK/DnaJ inEscherichia colienhances solubility but promotes proteolytic degradation of their substrates, minimizing the yield of unstable polypeptides. Higher eukaryotes have orthologs of DnaK/DnaJ but lack the linked bacterial proteolytic system. By coexpression of DnaK and DnaJ in insect cells with inherently misfolding-prone recombinant proteins, we demonstrate simultaneous improvement of soluble protein yield and quality and proteolytic stability. Thus, undesired side effects of bacterial folding modulators can be avoided by appropriate rehosting in heterologous cell expression systems.
Improved Production of Homo-
d
-Lactic Acid via Xylose Fermentation by Introduction of Xylose Assimilation Genes and Redirection of the Phosphoketolase Pathway to the Pentose Phosphate Pathway in
l
-Lactate Dehydrogenase Gene-Deficient
Lactobacillus plantarum
Authors: Okano Kenji , Yoshida Shogo , Yamada Ryosuke , Tanaka Tsutomu , Ogino Chiaki , Fukuda Hideki , Kondo Akihiko 
Published: October 2009

ABSTRACT

The production of optically pure
d
-lactic acid via xylose fermentation was achieved by using a
Lactobacillus plantarum
NCIMB 8826 strain whose
l
-lactate dehydrogenase gene was deficient and whose phosphoketolase genes were replaced with a heterologous transketolase gene. After 60 h of fermentation, 41.2 g/liter of
d
-lactic acid was produced from 50 g/liter of xylose.
Francisella tularensisType A Strains Cause the Rapid Encystment ofAcanthamoeba castellaniiand Survive in Amoebal Cysts for Three Weeks Postinfection
Authors: El-Etr Sahar H. , Margolis Jeffrey J. , Monack Denise , Robison Richard A. , Cohen Marissa , Moore Emily , Rasley Amy 
Published: October 2009

ABSTRACTFrancisella tularensis, the causative agent of the zoonotic disease tularemia, has recently gained increased attention due to the emergence of tularemia in geographical areas where the disease has been previously unknown and to the organism's potential as a bioterrorism agent. AlthoughF. tularensishas an extremely broad host range, the bacterial reservoir in nature has not been conclusively identified. In this study, the ability of virulentF. tularensisstrains to survive and replicate in the amoebaAcanthamoeba castellaniiwas explored. We observe thatA. castellaniitrophozoites rapidly encyst in response toF. tularensisinfection and that this rapid encystment phenotype is caused by factor(s) secreted by amoebae and/orF. tularensisinto the coculture medium. Further, our results indicate that in contrast to the live vaccine strain LVS, virulent strains ofF. tularensiscan survive inA. castellaniicysts for at least 3 weeks postinfection and that the induction of rapid amoeba encystment is essential for survival. In addition, our data indicate that pathogenicF. tularensisstrains block lysosomal fusion inA. castellanii. Taken together, these data suggest that interactions betweenF. tularensisstrains and amoebae may play a role in the environmental persistence ofF. tularensis.
Metabolic Engineering of the Tricarboxylic Acid Cycle for Improved Lysine Production by
Corynebacterium glutamicum
Authors: Becker Judith , Klopprogge Corinna , Schröder Hartwig , Wittmann Christoph 
Published: October 2009

ABSTRACT

In the present work, lysine production by
Corynebacterium glutamicum
was improved by metabolic engineering of the tricarboxylic acid (TCA) cycle. The 70% decreased activity of isocitrate dehydrogenase, achieved by start codon exchange, resulted in a >40% improved lysine production. By flux analysis, this could be correlated to a flux shift from the TCA cycle toward anaplerotic carboxylation.
Carbohydrate Utilization Patterns for the Extremely Thermophilic Bacterium
Caldicellulosiruptor saccharolyticus
Reveal Broad Growth Substrate Preferences
Authors: VanFossen Amy L. , Verhaart Marcel R. A. , Kengen Servé M. W. , Kelly Robert M. 
Published: October 2009

ABSTRACT

Coutilization of hexoses and pentoses derived from lignocellulose is an attractive trait in microorganisms considered for consolidated biomass processing to biofuels. This issue was examined for the H
2
-producing, extremely thermophilic bacterium
Caldicellulosiruptor saccharolyticus
growing on individual monosaccharides (arabinose, fructose, galactose, glucose, mannose, and xylose), mixtures of these sugars, as well as on xylan and xylogluco-oligosacchrides.
C. saccharolyticus
grew at approximately the same rate (
t
d
, ∼95 min) and to the same final cell density (1 × 10
8
to 3 × 10
8
cells/ml) on all sugars and sugar mixtures tested. In the monosaccharide mixture, although simultaneous consumption of all monosaccharides was observed, not all were utilized to the same extent (fructose > xylose/arabinose > mannose/glucose/galactose). Transcriptome contrasts for monosaccharide growth revealed minimal changes in some cases (e.g., 32 open reading frames [ORFs] changed ≥2-fold for glucose versus galactose), while substantial changes occurred for cases involving mannose (e.g., 353 ORFs changed ≥2-fold for glucose versus mannose). Evidence for catabolite repression was not noted for either growth on multisugar mixtures or the corresponding transcriptomes. Based on the whole-genome transcriptional response analysis and comparative genomics, carbohydrate specificities for transport systems could be proposed for most of the 24 putative carbohydrate ATP-binding cassette transporters and single phosphotransferase system identified in
C. saccharolyticus
. Although most transporter genes responded to individual monosaccharides and polysaccharides, the genes Csac_0692 to Csac_0694 were upregulated only in the monosaccharide mixture. The results presented here affirm the broad growth substrate preferences of
C. saccharolyticus
on carbohydrates representative of lignocellulosic biomass and suggest that this bacterium holds promise for biofuel applications.
Heterologous Expression Studies of
Saccharomyces cerevisiae
Reveal Two Distinct Trypanosomatid CaaX Protease Activities and Identify Their Potential Targets
Authors: Mokry David Z. , Manandhar Surya P. , Chicola Kristen A. , Santangelo George M. , Schmidt Walter K. 
Published: October 2009

ABSTRACT

The CaaX tetrapeptide motif typically directs three sequential posttranslational modifications, namely, isoprenylation, proteolysis, and carboxyl methylation. In all eukaryotic systems evaluated to date, two CaaX proteases (Rce1 and Ste24/Afc1) have been identified. Although the
Trypanosoma brucei
genome also encodes two putative CaaX proteases, the lack of detectable
T. brucei
Ste24 activity in trypanosome cell extracts has suggested that CaaX proteolytic activity within this organism is solely attributed to
T. brucei
Rce1 (J. R. Gillespie et al., Mol. Biochem. Parasitol. 153:115-124. 2007). In this study, we demonstrate that both
T. brucei
Rce1 and
T. brucei
Ste24 are enzymatically active when heterologously expressed in yeast. Using
a
-factor and GTPase reporters, we demonstrate that
T. brucei
Rce1 and
T. brucei
Ste24 possess partially overlapping specificities much like, but not identical to, their fungal and human counterparts. Of interest, a CaaX motif found on a trypanosomal Hsp40 protein was not cleaved by either
T. brucei
CaaX protease when examined in the context of the yeast
a
-factor reporter but was cleaved by both in the context of the Hsp40 protein itself when evaluated using an in vitro radiolabeling assay. We further demonstrate that
T. brucei
Rce1 is sensitive to small molecules previously identified as inhibitors of the yeast and human CaaX proteases and that a subset of these compounds disrupt
T. brucei
Rce1-dependent localization of our GTPase reporter in yeast. Together, our results suggest the conserved presence of two CaaX proteases in trypanosomatids, identify an Hsp40 protein as a substrate of both
T. brucei
CaaX proteases, support the potential use of small molecule CaaX protease inhibitors as tools for cell biological studies on the trafficking of CaaX proteins, and provide evidence that protein context influences
T. brucei
CaaX protease specificity.
Novel Putative Glycosylphosphatidylinositol-Anchored Micronemal Antigen of
Plasmodium falciparum
That Binds to Erythrocytes
Authors: Hinds Louise , Green Judith L. , Knuepfer Ellen , Grainger Munira , Holder Anthony A. 
Published: October 2009

ABSTRACT

We have identified a new
Plasmodium falciparum
erythrocyte binding protein that appears to be located in the micronemes of the merozoite stage of the parasite and membrane linked through a glycosylphosphatidylinositol (GPI) anchor. The protein is designated GPI-anchored micronemal antigen (GAMA) and was identified by applying a set of selection criteria to identify previously uncharacterized merozoite proteins that may have a role in cell invasion. The protein is also present in the proteomes of the sporozoite and ookinete micronemes and is conserved throughout the genus. GAMA contains a novel domain that may be constrained by disulfide bonds and a predicted C-terminal hydrophobic sequence that is presumably replaced by the GPI. The protein is synthesized late during schizogony, processed into two fragments that are linked by a disulfide bond, and translocated to an apical location, which is probably the micronemes. In a proportion of free merozoites GAMA can also be detected on the parasite surface. Following erythrocyte invasion the bulk of the protein is shed in a soluble form, although a short C-terminal fragment may be carried into the newly invaded red blood cell. The protein was shown to bind reversibly to erythrocytes and therefore represents a new example of a host cell binding protein.
Solution Structure, Determined by Nuclear Magnetic Resonance, of the b30-82 Domain of Subunit
b
of
Escherichia coli
F
1
F
o
ATP Synthase
Authors: Priya Ragunathan , Biuković Goran , Gayen Shovanlal , Vivekanandan Subramanian , Grüber Gerhard 
Published: October 2009

ABSTRACT

Subunit
b
, the peripheral stalk of bacterial F
1
F
o
ATP synthases, is composed of a membrane-spanning and a soluble part. The soluble part is divided into tether, dimerization, and δ-binding domains. The first solution structure of b30-82, including the tether region and part of the dimerization domain, has been solved by nuclear magnetic resonance, revealing an α-helix between residues 39 and 72. In the solution structure, b30-82 has a length of 48.07 Å. The surface charge distribution of b30-82 shows one side with a hydrophobic surface pattern, formed by alanine residues. Alanine residues 61, 68, 70, and 72 were replaced by single cysteines in the soluble part of subunit
b
, b22-156. The cysteines at positions 61, 68, and 72 showed disulfide formation. In contrast, no cross-link could be formed for the A70C mutant. The patterns of disulfide bonding, together with the circular dichroism spectroscopy data, are indicative of an adjacent arrangement of residues 61, 68, and 72 in both α-helices in b22-156.
Crystal Structure of Adenylylsulfate Reductase fromDesulfovibrio gigasSuggests a Potential Self-Regulation Mechanism Involving the C Terminus of the β-Subunit
Authors: Chiang Yuan-Lan , Hsieh Yin-Cheng , Fang Jou-Yin , Liu En-Hong , Huang Yen-Chieh , Chuankhayan Phimonphan , Jeyakanthan Jeyaraman , Liu Ming-Yih , Chan Sunney I. , Chen Chun-Jung 
Published: October 2009

ABSTRACTAdenylylsulfate reductase (adenosine 5′-phosphosulfate [APS] reductase [APSR]) plays a key role in catalyzing APS to sulfite in dissimilatory sulfate reduction. Here, we report the crystal structure of APSR fromDesulfovibrio gigasat 3.1-Å resolution. Different from the α2β2-heterotetramer of theArchaeoglobus fulgidus, the overall structure of APSR fromD. gigascomprises six αβ-heterodimers that form a hexameric structure. The flavin adenine dinucleotide is noncovalently attached to the α-subunit, and two [4Fe-4S] clusters are enveloped by cluster-binding motifs. The substrate-binding channel inD. gigasis wider than that inA. fulgidusbecause of shifts in the loop (amino acid 326 to 332) and the α-helix (amino acid 289 to 299) in the α-subunit. The positively charged residue Arg160 in the structure ofD. gigaslikely replaces the role of Arg83 in that ofA. fulgidusfor the recognition of substrates. The C-terminal segment of the β-subunit wraps around the α-subunit to form a functional unit, with the C-terminal loop inserted into the active-site channel of the α-subunit from another αβ-heterodimer. Electrostatic interactions between the substrate-binding residue Arg282 in the α-subunit and Asp159 in the C terminus of the β-subunit affect the binding of the substrate. Alignment of APSR sequences fromD. gigasandA. fulgidusshows the largest differences toward the C termini of the β-subunits, and structural comparison reveals notable differences at the C termini, activity sites, and other regions. The disulfide comprising Cys156 to Cys162 stabilizes the C-terminal loop of the β-subunit and is crucial for oligomerization. Dynamic light scattering and ultracentrifugation measurements reveal multiple forms of APSR upon the addition of AMP, indicating that AMP binding dissociates the inactive hexamer into functional dimers, presumably by switching the C terminus of the β-subunit away from the active site. The crystal structure of APSR, together with its oligomerization properties, suggests that APSR from sulfate-reducing bacteria might self-regulate its activity through the C terminus of the β-subunit.
Penetration of the Blood-Brain Barrier by
Bacillus anthracis
Requires the pXO1-Encoded BslA Protein
Authors: Ebrahimi Celia M. , Kern Justin W. , Sheen Tamsin R. , Ebrahimi-Fardooee Mohammad A. , van Sorge Nina M. , Schneewind Olaf , Doran Kelly S. 
Published: October 2009

ABSTRACT

Anthrax is a zoonotic disease caused by the gram-positive spore-forming bacterium
Bacillus anthracis
. Human infection occurs after the ingestion, inhalation, or cutaneous inoculation of
B. anthracis
spores. The subsequent progression of the disease is largely mediated by two native virulence plasmids, pXO1 and pXO2, and is characterized by septicemia, toxemia, and meningitis. In order to produce meningitis, blood-borne bacteria must interact with and breach the blood-brain barrier (BBB) that is composed of a specialized layer of brain microvascular endothelial cells (BMEC). We have recently shown that
B. anthracis
Sterne is capable of penetrating the BBB in vitro and in vivo, establishing the classic signs of meningitis; however, the molecular mechanisms underlying the central nervous system (CNS) tropism are not known. Here, we show that attachment to and invasion of human BMEC by
B. anthracis
Sterne is mediated by the pXO1 plasmid and an encoded envelope factor, BslA. The results of studies using complementation analysis, recombinant BslA protein, and heterologous expression demonstrate that BslA is both necessary and sufficient to promote adherence to brain endothelium. Furthermore, mice injected with the BslA-deficient strain exhibited a significant decrease in the frequency of brain infection compared to mice injected with the parental strain. In addition, BslA contributed to BBB breakdown by disrupting tight junction protein ZO-1. Our results identify the pXO1-encoded BslA adhesin as a critical mediator of CNS entry and offer new insights into the pathogenesis of anthrax meningitis.
Structure/Function Analysis of thePantoea stewartiiQuorum-Sensing Regulator EsaR as an Activator of Transcription
Authors: Schu Daniel J. , Carlier Aurelien L. , Jamison Katherine P. , von Bodman Susanne , Stevens Ann M. 
Published: October 2009

ABSTRACTInPantoea stewartiisubsp.stewartii, two regulatory proteins are key to the process of cell-cell communication known as quorum sensing: the LuxI and LuxR homologues EsaI and EsaR. Most LuxR homologues function as activators of transcription in the presence of their cognate acylated homoserine lactone (AHL) signal. However, EsaR was initially found to function as a repressor in the absence of AHL. Previous studies demonstrated that, in the absence of AHL, EsaR retains the ability to function as a weak activator of theluxoperon in recombinantEscherichia coli. Here it is shown that both the N-terminal and the C-terminal domains of EsaR are necessary for positive regulation. A site-directed mutagenesis study, guided by homology modeling to LuxR and TraR, has revealed three critical residues in EsaR that are involved in activation of RNA polymerase. In addition, a native EsaR-activated promoter has been identified, which controls expression of a putative regulatory sRNA inP. stewartii.
Cryo-Electron Tomography Elucidates the Molecular Architecture ofTreponema pallidum, the Syphilis Spirochete
Authors: Izard Jacques , Renken Christian , Hsieh Chyong-Ere , Desrosiers Daniel C. , Dunham-Ems Star , La Vake Carson , Gebhardt Linda L. , Limberger Ronald J. , Cox David L. , Marko Michael , Radolf Justin D. 
Published: October 2009

ABSTRACTCryo-electron tomography (CET) was used to examine the native cellular organization ofTreponema pallidum, the syphilis spirochete.T. pallidumcells appeared to form flat waves, did not contain an outer coat and, except for bulges over the basal bodies and widening in the vicinity of flagellar filaments, displayed a uniform periplasmic space. Although the outer membrane (OM) generally was smooth in contour, OM extrusions and blebs frequently were observed, highlighting the structure's fluidity and lack of attachment to underlying periplasmic constituents. Cytoplasmic filaments converged from their attachment points opposite the basal bodies to form arrays that ran roughly parallel to the flagellar filaments along the inner surface of the cytoplasmic membrane (CM). Motile treponemes stably attached to rabbit epithelial cells predominantly via their tips. CET revealed thatT. pallidumcell ends have a complex morphology and assume at least four distinct morphotypes. Images of dividing treponemes and organisms shedding cell envelope-derived blebs provided evidence for the spirochete's complex membrane biology. In the regions without flagellar filaments, peptidoglycan (PG) was visualized as a thin layer that divided the periplasmic space into zones of higher and lower electron densities adjacent to the CM and OM, respectively. Flagellar filaments were observed overlying the PG layer, while image modeling placed the PG-basal body contact site in the vicinity of the stator-P-collar junction. Bioinformatics and homology modeling indicated that the MotB proteins ofT. pallidum,Treponema denticola, andBorrelia burgdorferihave membrane topologies and PG binding sites highly similar to those of their well-characterizedEscherichia coliandHelicobacter pyloriorthologs. Collectively, our results help to clarify fundamental differences in cell envelope ultrastructure between spirochetes and gram-negative bacteria. They also confirm that PG stabilizes the flagellar motor and enable us to propose that in most spirochetes motility results from rotation of the flagellar filaments against the PG.