bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isolation and Characterization of a Novel As(V)-Reducing Bacterium: Implications for Arsenic Mobilization and the Genus
Desulfitobacterium
Authors: Niggemyer Allison , Spring Stefan , Stackebrandt Erko , Rosenzweig R. Frank 
Published: July 2002

ABSTRACT

Dissimilatory arsenate-reducing bacteria have been implicated in the mobilization of arsenic from arsenic-enriched sediments. An As(V)-reducing bacterium, designated strain GBFH, was isolated from arsenic-contaminated sediments of Lake Coeur d'Alene, Idaho. Strain GBFH couples the oxidation of formate to the reduction of As(V) when formate is supplied as the sole carbon source and electron donor. Additionally, strain GBFH is capable of reducing As(V), Fe(III), Se(VI), Mn(IV) and a variety of oxidized sulfur species. 16S ribosomal DNA sequence comparisons reveal that strain GBFH is closely related to
Desulfitobacterium hafniense
DCB-2
T
and
Desulfitobacterium frappieri
PCP-1
T
. Comparative physiology demonstrates that
D
.
hafniense
and
D
.
frappieri
, known for reductively dechlorinating chlorophenols, are also capable of toxic metal or metalloid respiration. DNA-DNA hybridization and comparative physiological studies suggest that
D. hafniense
,
D. frappieri
, and strain GBFH should be united into one species. The isolation of an Fe(III)- and As(V)-reducing bacterium from Lake Coeur d'Alene suggests a mechanism for arsenic mobilization in these contaminated sediments while the discovery of metal or metalloid respiration in the genus
Desulfitobacterium
has implications for environments cocontaminated with arsenious and chlorophenolic compounds.
Effects of Hydrophobic and Electrostatic Cell Surface Properties of Bacteria on Feeding Rates of Heterotrophic Nanoflagellates
Authors: Matz Carsten , Jürgens Klaus 
Published: July 2002

ABSTRACT
The influence of cell surface hydrophobicity and electrostatic charge of bacteria on grazing rates of three common species of interception-feeding nanoflagellates was examined. The hydrophobicity of bacteria isolated from freshwater plankton was assessed by using two different methods (bacterial adhesion to hydrocarbon and hydrophobic interaction chromatography). The electrostatic charge of the cell surface (measured as zeta potential) was analyzed by microelectrophoresis. Bacterial ingestion rates were determined by enumerating bacteria in food vacuoles by immunofluorescence labelling via strain-specific antibodies. Feeding rates varied about twofold for each flagellate species but showed no significant dependence on prey hydrophobicity or surface charge. Further evidence was provided by an experiment involving flagellate grazing on complex bacterial communities in a two-stage continuous culture system. The hydrophobicity values of bacteria that survived protozoan grazing were variable, but the bacteria did not tend to become more hydrophilic. We concluded that variability in bacterial cell hydrophobicity and variability in surface charge do not severely affect uptake rates of suspended bacteria or food selection by interception-feeding flagellates.
Yeast Species Associated with Orange Juice: Evaluation of Different Identification Methods
Authors: Arias Covadonga R. , Burns Jacqueline K. , Friedrich Lorrie M. , Goodrich Renee M. , Parish Mickey E. 
Published: July 2002

ABSTRACT

Five different methods were used to identify yeast isolates from a variety of citrus juice sources. A total of 99 strains, including reference strains, were identified using a partial sequence of the 26S rRNA gene, restriction pattern analysis of the internal transcribed spacer region (5.8S-ITS), classical methodology, the RapID Yeast Plus system, and API 20C AUX. Twenty-three different species were identified representing 11 different genera. Distribution of the species was considerably different depending on the type of sample. Fourteen different species were identified from pasteurized single-strength orange juice that had been contaminated after pasteurization (PSOJ), while only six species were isolated from fresh-squeezed, unpasteurized orange juice (FSOJ). Among PSOJ isolates,
Candida intermedia
and
Candida parapsilosis
were the predominant species.
Hanseniaspora occidentalis
and
Hanseniaspora uvarum
represented up to 73% of total FSOJ isolates. Partial sequence of the 26S rRNA gene yielded the best results in terms of correct identification, followed by classical techniques and 5.8S-ITS analysis. The commercial identification kits RapID Yeast Plus system and API 20C AUX were able to correctly identify only 35 and 13% of the isolates, respectively. Six new 5.8S-ITS profiles were described, corresponding to
Clavispora lusitaniae
,
Geotrichum citri-aurantii
,
H. occidentalis
,
H. vineae
,
Pichia fermentans
, and
Saccharomycopsis crataegensis
. With the addition of these new profiles to the existing database, the use of 5.8S-ITS sequence became the best tool for rapid and accurate identification of yeast isolates from orange juice.
Engineering the
Rhizobium leguminosarum
bv. viciae Hydrogenase System for Expression in Free-Living Microaerobic Cells and Increased Symbiotic Hydrogenase Activity
Authors: Brito B. , Palacios J. M. , Imperial J. , Ruiz-Argüeso T. 
Published: July 2002

ABSTRACT

Rhizobium leguminosarum
bv. viciae UPM791 induces hydrogenase activity in pea (
Pisum sativum
L.) bacteroids but not in free-living cells. The symbiotic induction of hydrogenase structural genes (
hupSL
) is mediated by NifA, the general regulator of the nitrogen fixation process. So far, no culture conditions have been found to induce NifA-dependent promoters in vegetative cells of this bacterium. This hampers the study of the
R. leguminosarum
hydrogenase system. We have replaced the native NifA-dependent
hupSL
promoter with the FnrN-dependent
fixN
promoter, generating strain SPF25, which expresses the
hup
system in microaerobic free-living cells. SPF25 reaches levels of hydrogenase activity in microaerobiosis similar to those induced in UPM791 bacteroids. A sixfold increase in hydrogenase activity was detected in merodiploid strain SPF25(pALPF1). A time course induction of hydrogenase activity in microaerobic free-living cells of SPF25(pALPF1) shows that hydrogenase activity is detected after 3 h of microaerobic incubation. Maximal hydrogen uptake activity was observed after 10 h of microaerobiosis. Immunoblot analysis of microaerobically induced SPF25(pALPF1) cell fractions indicated that the HupL active form is located in the membrane, whereas the unprocessed protein remains in the soluble fraction. Symbiotic hydrogenase activity of strain SPF25 was not impaired by the promoter replacement. Moreover, bacteroids from pea plants grown in low-nickel concentrations induced higher levels of hydrogenase activity than the wild-type strain and were able to recycle all hydrogen evolved by nodules. This constitutes a new strategy to improve hydrogenase activity in symbiosis.
AhpC, AhpD, and a Secreted 14-Kilodalton Antigen from
Mycobacterium avium
subsp.
paratuberculosis
Distinguish between Paratuberculosis and Bovine Tuberculosis in an Enzyme-Linked Immunosorbent Assay
Authors: Olsen Ingrid , Tryland Morten , Wiker Harald G. , Reitan Liv J. 
Published: July 2002

ABSTRACT

Sera from cattle naturally infected with
Mycobacterium avium
subsp.
paratuberculosis
(
n
= 56) and naturally (
n
= 4) and experimentally (
n
= 8) infected with
Mycobacterium bovis
were tested for the presence of antibodies against paratuberculosis antigens. An enzyme-linked immunosorbent assay (ELISA) was established based on absorption of
M. avium
subsp.
paratuberculosis
antigens on a hyperimmune antiserum against
M. avium
subsp.
avium
proteins in order to remove cross-reacting antigens. This absorbed-antigen ELISA recognized 66% of animals with paratuberculosis (37 of 56), while none of the animals with naturally occurring bovine tuberculosis (TB) had detectable antibodies. However, the animals with experimental bovine TB also responded in this ELISA. Similar results were found in a commercial ELISA, showing that neither of these tests was able to distinguish between paratuberculosis and bovine TB. The sera were further tested for antibody activities against purified AhpC and AhpD, which are proteins constitutively expressed by
M. avium
subsp.
paratuberculosis,
and against a secreted 14-kDa protein present in culture filtrates from the
M. avium
complex. Elevated antibody levels to AhpC, AhpD, and the 14-kDa antigen were found in 27% (13 of 48), 15% (7 of 48), and 27% (13 of 48), respectively, of the cattle with paratuberculosis. Together these ELISAs were positive with 35% (17 of 48) of the animals. None of the animals with bovine TB had detectable antibodies against any of the purified proteins despite their high levels of cross-reacting antibodies. These results show that purified specific antigens are needed to differentiate between paratuberculosis and bovine TB in ELISA.
Laboratory-Acquired Parasitic Infections from Accidental Exposures
Authors: Herwaldt Barbara L. 
Published: July 2002

SUMMARY
Parasitic diseases are receiving increasing attention in developed countries in part because of their importance in travelers, immigrants, and immunocompromised persons. The main purpose of this review is to educate laboratorians, the primary readership, and health care workers, the secondary readership, about the potential hazards of handling specimens that contain viable parasites and about the diseases that can result. This is accomplished partly through discussion of the occupationally acquired cases of parasitic infections that have been reported, focusing for each case on the type of accident that resulted in infection, the length of the incubation period, the clinical manifestations that developed, and the means by which infection was detected. The article focuses on the cases of infection with the protozoa that cause leishmaniasis, malaria, toxoplasmosis, Chagas' disease (American trypanosomiasis), and African trypanosomiasis. Data about 164 such cases are discussed, as are data about cases caused by intestinal protozoa and by helminths. Of the 105 case-patients infected with blood and tissue protozoa who either recalled an accident or for whom the likely route of transmission could be presumed, 47 (44.8%) had percutaneous exposure via a contaminated needle or other sharp object. Some accidents were directly linked to poor laboratory practices (e.g., recapping a needle or working barehanded). To decrease the likelihood of accidental exposures, persons who could be exposed to pathogenic parasites must be thoroughly instructed in safety precautions before they begin to work and through ongoing training programs. Protocols should be provided for handling specimens that could contain viable organisms, using protective clothing and equipment, dealing with spills of infectious organisms, and responding to accidents. Special care should be exercised when using needles and other sharp objects.
T-Cell Epitopes and Human Leukocyte Antigen Restriction Elements of an Immunodominant Antigen ofBlastomyces dermatitidis
Authors: Chang W. L. , Audet R. G. , Aizenstein B. D. , Hogan L. H. , DeMars R. I. , Klein B. S. 
Published: July 2002

ABSTRACTHumans infected with the dimorphic fungusBlastomyces dermatitidisdevelop strong T-lymphocyte responses to WI-1, an immunodominant antigen that has been shown to elicit protective immunity in mice. In the present study, the T-cell epitopes of WI-1 and human leukocyte antigen (HLA) restricting elements that display them were investigated. Peripheral blood mononuclear cells (PBMC) from 37 patients with a confirmed history of blastomycosis were tested for a response to WI-1 in primary proliferation assays; PBMC from 35 (95%) responded. Six patients whose PBMC proliferated strongly in response to WI-1 (defined as a stimulation index greater than 50) were tested further for responses to subcloned, recombinant fragments of the antigen. These patients responded chiefly to sequences within the N terminus and the 25-amino-acid tandem repeat. Cloned CD4+T cells from an infected individual were used to delineate more precisely the peptide epitopes in the fragments and HLA restricting elements that present them. A majority of the T-cell clones recognized an epitope spanning amino acids 149 to 172 within the N terminus, displayed by HLA-DR 15. A minority of the clones, which have been shown to perform a cytolytic function in vitro, recognized an epitope in the tandem repeat displayed by HLA-DPw4, an uncommon restricting element. Tandem repeat epitopes required display by the β chain of DPw4 heterodimers. Thus, human T cells with different functions in vitro also recognize distinct regions of WI-1, raising the possibility that HLA restricting elements that present them could modulate immunity during blastomycosis by selection and display of WI-1 peptides.
DNA Adenine Methylase Is Essential for Viability and Plays a Role in the Pathogenesis of
Yersinia pseudotuberculosis
and
Vibrio cholerae
Authors: Julio Steven M. , Heithoff Douglas M. , Provenzano Daniele , Klose Karl E. , Sinsheimer Robert L. , Low David A. , Mahan Michael J. 
Published: July 2002

ABSTRACT

Salmonella
strains that lack or overproduce DNA adenine methylase (Dam) elicit a protective immune response to different
Salmonella
species. To generate vaccines against other bacterial pathogens, the
dam
genes of
Yersinia pseudotuberculosis
and
Vibrio cholerae
were disrupted but found to be essential for viability. Overproduction of Dam significantly attenuated the virulence of these two pathogens, leading to, in
Yersinia
, the ectopic secretion of virulence proteins (
Yersinia
outer proteins) and a fully protective immune response in vaccinated hosts. Dysregulation of Dam activity may provide a means for the development of vaccines against varied bacterial pathogens.
Interleukin-6 Deficiency Increases Inflammatory Bone Destruction
Authors: Balto Khaled , Sasaki Hajime , Stashenko Philip 
Published: July 2002

ABSTRACTPeriapical bone destruction occurs as a consequence of pulpal infection. In previous studies, we showed that interleukin-1 (IL-1) is the primary stimulator of bone destruction in this model. IL-6 is a pleiotropic cytokine that is induced in these infections and has both pro- and anti-inflammatory activities. In the present study, we determined the role of IL-6 in regulating IL-1 expression and bone resorption. The first molars of IL-6 knockouts (IL-6−/−) and wild-type mice were subjected to surgical pulp exposure and infection with a mixture of four common pulpal pathogens, includingPrevotella intermedia,Fusobacterium nucleatum,Peptostreptococcus micros, andStreptococcus intermedius. Mice were killed after 21 days, and bone destruction and cytokine expression were determined. Surprisingly, bone destruction was significantly increased in IL-6−/−mice versus that in wild-type mice (by 30%;P< 0.001). In a second experiment, the effects of chronic (IL-6−/−) IL-6 deficiency and short-term IL-6 deficiency induced by in vivo antibody neutralization were determined. Both IL-6−/−(30%;P< 0.001) and anti-IL-6 antibody-treated mice (40%;P< 0.05) exhibited increased periapical bone resorption, compared to wild-type controls. The increased bone resorption in IL-6-deficient animals correlated with increases in osteoclast numbers, as well as with elevated expression of bone-resorptive cytokines IL-1α and IL-1β, in periapical lesions and with decreased expression of the anti-inflammatory cytokine IL-10. These data demonstrate that endogenous IL-6 expression has significant anti-inflammatory effects in modulating infection-stimulated bone destruction in vivo.
Combinatorial Library Cloning of Human Antibodies toStreptococcus pneumoniaeCapsular Polysaccharides: Variable Region Primary Structures and Evidence for Somatic Mutation of Fab Fragments Specific for Capsular Serotypes 6B, 14, and 23F
Authors: Lucas Alexander H. , Moulton Karen D. , Tang Vanessa R. , Reason Donald C. 
Published: July 2002

ABSTRACTAntibodies specific for capsular polysaccharides play a central role in immunity to encapsulatedStreptococcus pneumoniae, but little is known about their genetics or the variable (V) region polymorphisms that affect their protective function. To begin to address these issues, we used combinatorial library cloning to isolate pneumococcal polysaccharide (PPS)-specific Fab fragments from two vaccinated adults. We determined complete V region primary structures and performed antigen binding analyses of seven Fab fragments specific for PPS serotype 6B, 14, or 23F. Fabs were of the immunoglobulin G2 or A isotype. Several VHIII gene segments (HV 3-7, 3-15, 3-23, and 3-11) were identified. VLregions were encoded by several κ genes (KV 4-1, 3-15, 2-24, and 2D-29) and a λ gene (LV 1-51). Deviation of the VHand VLregions from their assigned germ line counterparts indicated that they were somatically mutated. Fabs of the same serotype specificity isolated from a single individual differed in affinity, and these differences could be accounted for either by the extent of mutation among clonal relatives or by usage of different V-region genes. Thus, functionally disparate anti-PPS antibodies can arise within individuals both by activation of independent clones and by intraclonal somatic mutation. For one pair of clonally related Fabs, the more extensively mutated VHwas associated with lower affinity for PPS 14, a result suggesting that somatic mutation could lead to diminished protective efficacy. These findings indicate that the PPS repertoire in the adult derives from memory B-cell populations that have class switched and undergone extensive hypermutation.
Non-Major Histocompatibility Complex Control of Antibody Isotype and Th1 versus Th2 Cytokines during Experimental Infection of Mice withMycobacterium avium
Authors: Nagabhushanam Vijaya , Cheers Christina 
Published: July 2002

ABSTRACTInfection of different strains of mice withMycobacterium aviumhas revealed genetic control of the immunoglobulin isotype induced and of the balance between Th1 and Th2 cytokines. Female BALB/c or C57BL/10 mice were infected intranasally with 105M. aviumorganisms. The antibody response was measured over 18 weeks by enzyme-linked immunosorbent assay and Western blotting, while numbers of cytokine-producing cells were assessed at 12 to 15 weeks by ELISPOT assay. Upon infection, C57BL/10 mice produced a clear Th1 response with strong gamma interferon (IFN-γ) production, no interleukin-4 (IL-4), and almost entirely immunoglobulin G2a (IgG2a) antibody. In contrast, BALB/c mice developed T cells producing IL-4, as well as those producing IFN-γ, while the antibody response was a mixture of IgG1 and IgG2a. Antibodies from BALB/c mice were also able to recognize a greater range of antigens than were C56BL/10 mice. B10D2 mice, which carry the BALB/c major histocompatibility complex haplotype on a C57BL/10 background, followed the C57BL/10 cytokine pattern. Mice infected withListeria monocytogenesdid not show a similar response dichotomy.
Preexposure of Murine Macrophages to CpG Oligonucleotide Results in a Biphasic Tumor Necrosis Factor Alpha Response to Subsequent Lipopolysaccharide Challenge
Authors: Crabtree Traves D. , Jin Long , Raymond Daniel P. , Pelletier Shawn J. , Houlgrave C. Webster , Gleason Thomas G. , Pruett Timothy L. , Sawyer Robert G. 
Published: July 2002

ABSTRACTBacterial DNA and synthetic oligonucleotides containing CpG sequences (CpG-DNA and CpG-ODN) provoke a proinflammatory cytokine response (tumor necrosis factor alpha [TNF-α], interleukin-12 [IL-12], and IL-6) and increased mortality in lipopolysaccharide (LPS)-challenged mice via a TNF-α-mediated mechanism. It was hypothesized that preexposure of macrophages to CpG-ODN would result in an increased TNF-α response to subsequent LPS challenge in vitro. Using the murine macrophage cell line RAW 264.7, we demonstrated both a rapid proinflammatory cytokine response (TNF-α) and a delayed inhibitory cytokine response (IL-10) with CpG-ODN. Preexposure of macrophages to CpG-ODN for brief periods (1 to 3 h) augmented TNF-α secretion and mRNA accumulation following subsequent LPS challenge (1 μg/ml). However, prolonged preexposure to CpG-ODN (6 to 9 h) resulted in suppression of the TNF-α protein and mRNA response to LPS. The addition of anti-IL-10 antibody to CpG-ODN during preexposure resulted in an increase in the LPS-induced TNF-α response over that induced by CpG-ODN preexposure alone. Thus, while brief preexposure of macrophages to CpG-ODN augments the proinflammatory cytokine response to subsequent LPS challenge, prolonged preexposure elicits IL-10 production, which inhibits the TNF-α response. Although the initial proinflammatory effects of CpG-DNA are well established, the immune response to CpG-DNA may also include autocrine or paracrine feedback mechanisms, leading to a complex interaction of proinflammatory and inhibitory cytokines.
DNA from Protozoan ParasitesBabesia bovis, Trypanosoma cruzi, andT. bruceiIs Mitogenic for B Lymphocytes and Stimulates Macrophage Expression of Interleukin-12, Tumor Necrosis Factor Alpha, and Nitric Oxide
Authors: Shoda Lisl K. M. , Kegerreis Kimberly A. , Suarez Carlos E. , Roditi Isabel , Corral Ricardo S. , Bertot Gustavo M. , Norimine Junzo , Brown Wendy C. 
Published: July 2002

ABSTRACTThe activation of innate immune responses by genomic DNA from bacteria and several nonvertebrate organisms represents a novel mechanism of pathogen recognition. We recently demonstrated the CpG-dependent mitogenic activity of DNA from the protozoan parasiteBabesia bovisfor bovine B lymphocytes (W. C. Brown, D. M. Estes, S. E. Chantler, K. A. Kegerreis, and C. E. Suarez, Infect. Immun. 66:5423–5432, 1998). However, activation of macrophages by DNA from protozoan parasites has not been demonstrated. The present study was therefore conducted to determine whether DNA from the protozan parasitesB. bovis, Trypanosoma cruzi, andT. bruceiactivates macrophages to secrete inflammatory mediators associated with protective immunity. DNA fromEscherichia coliand all three parasites stimulated B-lymphocyte proliferation and increased macrophage production of interleukin-12 (IL-12), tumor necrosis factor alpha (TNF-α), and nitric oxide (NO). Regulation of IL-12 and NO production occurred at the level of transcription. The amounts of IL-12, TNF-α, and NO induced byE. coliand protozoal DNA were strongly correlated (r2> 0.9) with the frequency of CG dinucleotides in the genome, and immunostimulation by DNA occurred in the orderE. coli≥T. cruzi>T. brucei>B. bovis. Induction of inflammatory mediators byE. coli, T. brucei, andB. bovisDNA was dependent on the presence of unmethylated CpG dinucleotides. However, at high concentrations,E. coliandT. cruziDNA-mediated macrophage activation was not inhibited following methylation. The recognition of protozoal DNA by B lymphocytes and macrophages may provide an important innate defense mechanism to control parasite replication and promote persistent infection.