bluuebunny/crossref_metadata_2025_split huggingface dataset:
Suboxic Deposition of Ferric Iron by Bacteria in Opposing Gradients of Fe(II) and Oxygen at Circumneutral pH
Authors: Sobolev Dmitri , Roden Eric E. 
Published: July 2002

ABSTRACT

The influence of lithotrophic Fe(II)-oxidizing bacteria on patterns of ferric oxide deposition in opposing gradients of Fe(II) and O
2
was examined at submillimeter resolution by use of an O
2
microelectrode and diffusion microprobes for iron. In cultures inoculated with lithotrophic Fe(II)-oxidizing bacteria, the majority of Fe(III) deposition occurred below the depth of O
2
penetration. In contrast, Fe(III) deposition in abiotic control cultures occurred entirely within the aerobic zone. The diffusion microprobes revealed the formation of soluble or colloidal Fe(III) compounds during biological Fe(II) oxidation. The presence of mobile Fe(III) in diffusion probes from live cultures was verified by washing the probes in anoxic water, which removed ca. 70% of the Fe(III) content of probes from live cultures but did not alter the Fe(III) content of probes from abiotic controls. Measurements of the amount of Fe(III) oxide deposited in the medium versus the probes indicated that ca. 90% of the Fe(III) deposited in live cultures was formed biologically. Our findings show that bacterial Fe(II) oxidation is likely to generate reactive Fe(III) compounds that can be immediately available for use as electron acceptors for anaerobic respiration and that biological Fe(II) oxidation may thereby promote rapid microscale Fe redox cycling at aerobic-anaerobic interfaces.
Reduction in Exopolysaccharide Viscosity as an Aid to Bacteriophage Penetration through
Pseudomonas aeruginosa
Biofilms
Authors: Hanlon Geoffrey W. , Denyer Stephen P. , Olliff Cedric J. , Ibrahim Lamia J. 
Published: July 2002

ABSTRACT

To cause an infection, bacteriophages must penetrate the alginate exopolysaccharide of
Pseudomonas aeruginosa
to reach the bacterial surface. Despite a lack of intrinsic motility, phage were shown to diffuse through alginate gels at alginate concentrations up to 8% (wt/vol) and to bring about a 2-log reduction in the cell numbers in 20-day-old biofilms of
P. aeruginosa
. The inability of alginate to act as a more effective diffusional barrier suggests that phage may cause a reduction in the viscosity of the exopolysaccharide. Samples (
n
= 5) of commercial alginate and purified cystic fibrosis (CF) alginate were incubated with 2 × 10
8
purified phage per ml for 24 h at 37°C. After incubation the samples and controls were subjected to rheological analysis with a Carrimed controlled stress rheometer. The viscosities of phage-treated samples were reduced by up to 40% compared to those of controls incubated in the absence of phage. The experiment was repeated by using phage concentrations of 10
10
and 10
12
phage per ml and samples taken for analysis at intervals up to 4 h. The results indicated that there was a time- and concentration-dependent reduction in viscosity of up to 40% compared to the viscosities of the controls. Commercial and purified CF alginate samples, both phage treated and untreated, were subjected to gel filtration chromatography by using Sephacryl High Resolution S-400 medium in order to obtain evidence of degradation. The results demonstrated that alginate treated with phage had a lower molecular weight than untreated alginate. The data suggest that bacteriophage migration through
P. aeruginosa
biofilms may be facilitated by a reduction in alginate viscosity brought about by enzymic degradation and that the source of the enzyme may be the bacterial host itself.
Hyperthermostable Endoglucanase from
Pyrococcus horikoshii
Authors: Ando Susumu , Ishida Hiroyasu , Kosugi Yoshitsugu , Ishikawa Kazuhiko 
Published: July 2002

ABSTRACT

An endoglucanase homolog from the hyperthermophilic archaeon
Pyrococcus horikoshii
was expressed in
Escherichia coli
, and its enzymatic characteristics were examined. The expressed protein was a hyperthermostable endoglucanase which hydrolyzes celluloses, including Avicel and carboxymethyl cellulose, as well as β-glucose oligomers. This enzyme is the first endoglucanase belonging to glycosidase family 5 found from
Pyrococcus
species and is also the first hyperthermostable endoglucanase to which celluloses are the best substrates. This enzyme is expected to be useful for industrial hydrolysis of cellulose at high temperatures, particularly in biopolishing of cotton products.
Isolation and Characterization of Endophytic Colonizing Bacteria from Agronomic Crops and Prairie Plants
Authors: Zinniel Denise K. , Lambrecht Pat , Harris N. Beth , Feng Zhengyu , Kuczmarski Daniel , Higley Phyllis , Ishimaru Carol A. , Arunakumari Alahari , Barletta Raúl G. , Vidaver Anne K. 
Published: July 2002

ABSTRACT

Endophytic bacteria reside within plant hosts without causing disease symptoms. In this study, 853 endophytic strains were isolated from aerial tissues of four agronomic crop species and 27 prairie plant species. We determined several phenotypic properties and found approximately equal numbers of gram-negative and gram-positive isolates. In a greenhouse study, 28 of 86 prairie plant endophytes were found to colonize their original hosts at 42 days postinoculation at levels of 3.5 to 7.7 log
10
CFU/g (fresh weight). More comprehensive colonization studies were conducted with 373 corn and sorghum endophytes. In growth room studies, none of the isolates displayed pathogenicity, and 69 of the strains were recovered from corn or sorghum seedlings at levels of 8.3 log
10
CFU/plant or higher. Host range greenhouse studies demonstrated that 26 of 29 endophytes were recoverable from at least one host other than corn and sorghum at levels of up to 5.8 log
10
CFU/g (fresh weight). Long-range dent corn greenhouse studies and field trials with 17 wild-type strains and 14 antibiotic-resistant mutants demonstrated bacterial persistence at significant average colonization levels ranging between 3.4 and 6.1 log
10
CFU/g (fresh weight) up to 78 days postinoculation. Three prairie and three agronomic endophytes exhibiting the most promising levels of colonization and an ability to persist were identified as
Cellulomonas
,
Clavibacter
,
Curtobacterium
, and
Microbacterium
isolates by 16S rRNA gene sequence, fatty acid, and carbon source utilization analyses. This study defines for the first time the endophytic nature of
Microbacterium testaceum
. These microorganisms may be useful for biocontrol and other applications.
Experimental Study of Interactions between Purple and Green Sulfur Bacteria in Sandy Sediments Exposed to Illumination Deprived of Near-Infrared Wavelengths
Authors: Massé Astrid , Pringault Olivier , de Wit Rutger 
Published: July 2002

ABSTRACT

Sedimentary biofilms of the green sulfur bacterium
Prosthecochloris aestuarii
strain CE 2404, the purple sulfur bacterium
Thiocapsa roseopersicina
strain 5811, and a mixed culture of both were cultured in fine sand (100- to 300-μm grain size) within counter gradients of oxygen and sulfide. The artificial sediments were exposed to illumination deprived of near-infrared light (NIR) by filtering out the wavelengths longer than 700 nm to simulate the critical light conditions in submerged aquatic sediments. A 16 h of visible light-8 h of dark regimen was used. We studied the effects of these light conditions on the metabolisms of and interactions between both species by comparing the single species biofilms with the mixed biofilm. The photosynthesis rates of
P. aestuarii
were shown to be highly limited by the imposed light conditions, because the sulfide photooxidation rates were strongly stimulated when NIR was added.
T. roseopersicina
performed both aerobic chemosynthesis and photosynthesis, but the photosynthesis rates were low and poorly stimulated by the addition of NIR. This species decreased the penetration depth of oxygen in the sediment by about 1 mm by actively respiring oxygen. This way, the strict anaerobe
P. aestuarii
was able to grow closer to the surface in the mixed culture. As a result,
P. aestuarii
benefited from the presence of
T. roseopersicina
in the mixed culture, which was reflected by an increase in the biomass. In contrast, the density of the latter species was almost completely unaffected by the interaction. Both species coexisted in a layer of the same depth in the mixed culture, and the ecological and evolutionary implications of coexistence are discussed.
Universal Immunoprobe for (Per)Chlorate-Reducing Bacteria
Authors: O'Connor Susan M. , Coates John D. 
Published: July 2002

ABSTRACT

Recent studies in our lab have demonstrated the ubiquity and diversity of microorganisms which couple growth to the reduction of chlorate or perchlorate [(per)chlorate] under anaerobic conditions. We identified two taxonomic groups, the
Dechloromonas
and the
Dechlorosoma
groups, which represent the dominant (per)chlorate-reducing bacteria (ClRB) in the environment. As part of these studies we demonstrated that chlorite dismutation is a central step in the reductive pathway of (per)chlorate that is common to all ClRB and which is mediated by the enzyme chlorite dismutase (CD). Initial studies on CD suggested that this enzyme is highly conserved among the ClRB, regardless of their phylogenetic affiliation. As such, this enzyme makes an ideal target for a probe specific for these organisms. Polyclonal antibodies were commercially raised against the purified CD from the ClRB
Dechloromonas agitata
strain CKB. The obtained antiserum was deproteinated by ammonium sulfate precipitation, and the antigen binding activity was assessed using dot blot analysis of a serial dilution of the antiserum. The titers obtained with purified CD indicated that the antiserum had a high affinity for the CD enzyme, and activity was observed in dilutions as low as 10
−6
of the original antiserum. The antiserum was active against both cell lysates and whole cells of
D. agitata
, but only if the cells were grown anaerobically with (per)chlorate. No response was obtained with aerobically grown cultures. In addition to
D. agitata
, dot blot analysis employed with both whole-cell suspensions and cell lysates of several diverse ClRB representing the alpha, beta, and gamma subclasses of
Proteobacteria
tested positive regardless of phylogenetic affiliation. Interestingly, the dot blot response obtained for each of the ClRB cell lysates was different, suggesting that there may be some differences in the antigenic sites of the CD protein produced in these organisms. In general, no reactions were observed with cells or cell lysates of the organisms closely related to the ClRB which could not grow by (per)chlorate reduction. These studies have resulted in the development of a highly specific and sensitive immunoprobe based on the commonality of the CD enzyme in ClRB which can be used to assess dissimilatory (per)chlorate-reducing populations in environmental samples regardless of their phylogenetic affiliations.
Human Lymphocyte Proliferation Responses following Primary Immunization with Rabies Vaccine as Neoantigen
Authors: Ghaffari Guity , Passalacqua Dominick J. , Bender Bradley S. , Briggs Debora J. , Goodenow Maureen M. , Sleasman John W. 
Published: July 2002

ABSTRACT

Evaluation of the T-cell immune response following primary antigenic challenge with a neoantigen is a critical aspect of assessment of the cellular immune response. While many antigens can be used to accurately assess in vitro T-cell proliferation to a recall antigen, only a few neoantigens have been tested for their capacities to measure T-cell responses in vitro to a primary immunization. Rabies vaccination is an excellent candidate for the testing of T-cell proliferation responses to a primary immunization because few individuals have been exposed to rabies virus antigens. In the present study 14 rabies vaccine-naı̈ve, healthy adult volunteers were immunized against rabies virus, and T-cell proliferation and antibody responses were measured before and after vaccination. Optimal lymphocyte proliferation to soluble rabies virus antigen occurred after 8 days in culture. The average level of uptake of tritiated thymidine postimmunization was 29,620 ± 4,448 cpm, whereas preimmunization levels were 12,660 ± 3,448 cpm (
P
= 0.002). All individuals showed increases in rabies virus antibody titers from <0.05 to 5.59 ± 1.64 IU/ml. The degree of proliferation to tetanus toxoid as a recall antigen was similar to the response to rabies virus antigen among the cohort. Due to high levels of preimmunization proliferation, four subjects failed to demonstrate a twofold increase in response to rabies virus antigen. The high levels of T-cell responses may be due to a viral superantigen effect in some individuals. Rabies vaccination offers a safe and effective means for measurement of both T- and B-cell immune responses to a neoantigen in healthy and immune suppressed individuals.
Biology ofGiardia lamblia
Authors: Adam Rodney D. 
Published: July 2002

SUMMARYGiardia lambliais a common cause of diarrhea in humans and other mammals throughout the world. It can be distinguished from otherGiardiaspecies by light or electron microscopy. The two major genotypes ofG. lambliathat infect humans are so different genetically and biologically that they may warrant separate species or subspecies designations. Trophozoites have nuclei and a well-developed cytoskeleton but lack mitochondria, peroxisomes, and the components of oxidative phosphorylation. They have an endomembrane system with at least some characteristics of the Golgi complex and encoplasmic reticulum, which becomes more extensive in encysting organisms. The primitive nature of the organelles and metabolism, as well as small-subunit rRNA phylogeny, has led to the proposal thatGiardiaspp. are among the most primitive eukaryotes.G. lambliaprobably has a ploidy of 4 and a genome size of approximately 10 to 12 Mb divided among five chromosomes. Most genes have short 5′ and 3′ untranslated regions and promoter regions that are near the initiation codon. Trophozoites exhibit antigenic variation of an extensive repertoire of cysteine-rich variant-specific surface proteins. Expression is allele specific, and changes in expression from onevspgene to another have not been associated with sequence alterations or gene rearrangements. TheGiardiagenome project promises to greatly increase our understanding of this interesting and enigmatic organism.
Interleukin-1 Receptor Type I Gene-Deficient Mice Are Less Susceptible toStaphylococcus epidermidisBiomaterial-Associated Infection than Are Wild-Type Mice
Authors: Boelens Jaap Jan , van der Poll Tom , Zaat Sebastian A. J. , Murk Jean L. A. N. , Weening Jan J. , Dankert Jacob 
Published: July 2002

ABSTRACTElevated concentrations of interleukin-1 (IL-1) were found in tissue surrounding biomaterials infected withStaphylococcus epidermidis.To determine the role of IL-1 in biomaterial-associated infection (BAI), IL-1 receptor type I-deficient (IL-1R−/−) and wild-type mice received subcutaneous implants of silicon elastomer (SE) or polyvinylpyrrolidone-grafted SE (SEpvp), combined with an injection of 106CFU ofS. epidermidisor sterile saline. Neither mouse strain was susceptible to BAI around SE. IL-1R−/−mice with SEpvp implants had a no abscess formation and a reduced susceptibility to persistentS. epidermidisinfection. The normal foreign body response, characterized by giant-cell formation and encapsulation, was delayed around SEpvp in wild-type mice but not in IL-1R−/−mice. This coincided with enhanced local IL-4 production in IL-1R−/−mice. These data suggest that inhibition of local IL-1 activity may be beneficial for the outcome of BAI.
Identification of the Operon for the Sorbitol (Glucitol) Phosphoenolpyruvate:Sugar Phosphotransferase System in
Streptococcus mutans
Authors: Boyd David A. , Thevenot Tracy , Gumbmann Markus , Honeyman Allen L. , Hamilton Ian R. 
Published: July 2002

ABSTRACT

Transposon mutagenesis and marker rescue were used to isolate and identify an 8.5-kb contiguous region containing six open reading frames constituting the operon for the sorbitol
P
-enolpyruvate phosphotransferase transport system (PTS) of
Streptococcus mutans
LT11. The first gene,
srlD
, codes for sorbitol-6-phosphate dehydrogenase, followed downstream by
srlR
, coding for a transcriptional regulator;
srlM
, coding for a putative activator; and the
srlA
,
srlE
, and
srlB
genes, coding for the EIIC, EIIBC, and EIIA components of the sorbitol PTS, respectively. Among all sorbitol PTS operons characterized to date, the
srlD
gene is found after the genes coding for the EII components; thus, the location of the gene in
S. mutans
is unique. The SrlR protein is similar to several transcriptional regulators found in
Bacillus
spp. that contain PTS regulator domains (J. Stülke, M. Arnaud, G. Rapoport, and I. Martin-Verstraete, Mol. Microbiol. 28:865–874, 1998), and its gene overlaps the
srlM
gene by 1 bp. The arrangement of these two regulatory genes is unique, having not been reported for other bacteria.
Enhanced Susceptibility to Subcutaneous Abscess Formation and Persistent Infection around Catheters Is Associated with Sustained Interleukin-1β Levels
Authors: Boelens J. J. , Zaat S. A. J. , Murk J. L. , Weening J. J. , van der Poll T. , Dankert J. 
Published: July 2002

ABSTRACTA persistentStaphylococcus epidermidisinfection in mice around a subcutaneous polyvinylpyrrolidone-grafted silicon elastomer catheter (SEpvp) but not around a conventional silicon elastomer catheter was observed. With SEpvp pericatheter tissue, protracted and exaggerated interleukin-1β (IL-1β) production was found. Apparently, sustained levels of IL-1β are associated with enhanced susceptibility to biomaterial-associatedS. epidermidisinfection.
Human Dendritic Cells Are Superior to B Cells at Presenting a Major Histocompatibility Complex Class II-Restricted Heterologous Antigen Expressed on RecombinantStreptococcus gordonii
Authors: Corinti Silvia , Medaglini Donata , Prezzi Caterina , Cavani Andrea , Pozzi Gianni , Girolomoni Giampiero 
Published: July 2002

ABSTRACTBacteria are being actively investigated as vaccine carriers for inducing or boosting protective immune responses. In this study, human monocyte-derived dendritic cells (DCs) and normal B cells were compared for their capacity to present the C fragment of tetanus toxin (TTFC), expressed on the surface of recombinantStreptococcus gordonii, to specific CD4+T lymphocytes. DCs were more efficient than B cells at presenting soluble TTFC and remarkably more capable of presenting bacterium-associated TTFC both in terms of the amount of antigen required to obtain a given T-cell response and on a per-cell basis. This difference was associated with a much lower capacity of B cells to endocytose soluble TTFC and phagocytose recombinantS. gordonii. In addition,S. gordoniiinduced the phenotypic maturation of DCs but not of B cells. The results thus indicate that DCs but not B cells play a crucial role in the amplification of class II-restricted immune responses induced by immunization with recombinant gram-positive bacteria.
Induction of Apoptotic Cell Death in Peripheral Blood Mononuclear and Polymorphonuclear Cells by an Oral Bacterium,Fusobacterium nucleatum
Authors: Jewett Anahid , Hume Wyatt R. , Le Ho , Huynh Tri N. , Han Yiping W. , Cheng Genhong , Shi Wenyuan 
Published: July 2002

ABSTRACTIt is largely unknown why a variety of bacteria present in the oral cavity are capable of establishing themselves in the periodontal pockets of nonimmunocompromised individuals in the presence of competent immune effector cells. In this paper we present evidence for the immunosuppressive role ofFusobacterium nucleatum, a gram-negative oral bacterium which plays an important role in the generation of periodontal disease. Our studies indicate that the immunosuppressive role ofF. nucleatumis largely due to the ability of this organism to induce apoptotic cell death in peripheral blood mononuclear cells (PBMCs) and in polymorphonuclear cells (PMNs).F. nucleatumtreatment induced apoptosis of PBMCs and PMNs as assessed by an increase in subdiploid DNA content determined by DNA fragmentation and terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end-labeling assays. The ability ofF. nucleatumto induce apoptosis was abolished by either heat treatment or proteinase digestion but was retained after formaldehyde treatment, suggesting that a heat-labile surface protein component is responsible for bacterium-mediated cell apoptosis. The data also indicated thatF. nucleatum-induced cell apoptosis requires activation of caspases and is protected by NF-κB. Possible mechanisms ofF. nucleatum's role in the pathogenesis of periodontal disease are discussed.
Acquisition of Expression of the
Pseudomonas aeruginosa
ExoU Cytotoxin Leads to Increased Bacterial Virulence in a Murine Model of Acute Pneumonia and Systemic Spread
Authors: Allewelt Markus , Coleman Fadie T. , Grout Martha , Priebe Gregory P. , Pier Gerald B. 
Published: July 2002

ABSTRACT

Pseudomonas aeruginosa
is the nosocomial bacterial pathogen most commonly isolated from the respiratory tract. Animal models of this infection are extremely valuable for studies of virulence and immunity. We thus evaluated the utility of a simple model of acute pneumonia for analyzing
P. aeruginosa
virulence by characterizing the course of bacterial infection in BALB/c mice following application of bacteria to the nares of anesthetized animals. Bacterial aspiration into the lungs was rapid, and 67 to 100% of the inoculum could be recovered within minutes from the lungs, with 0.1 to 1% of the inoculum found intracellularly shortly after infection. At later time points up to 10% of the bacteria were intracellular, as revealed by gentamicin exclusion assays on single-cell suspensions of infected lungs. Expression of exoenzyme U (ExoU) by
P. aeruginosa
is associated with a cytotoxic effect on epithelial cells in vitro and virulence in animal models. Insertional mutations in the
exoU
gene confer a noncytotoxic phenotype on mutant strains and decrease virulence for animals. We used the model of acute pneumonia to determine whether introduction of the
exoU
gene into noncytotoxic strains of
P. aeruginosa
lacking this gene affected virulence. Seven phenotypically noncytotoxic
P. aeruginosa
strains were transformed with pUCP19
exoUspcU
which carries the
exoU
gene and its associated chaperone. Three of these strains became cytotoxic to cultured epithelial cells in vitro. These strains all secreted ExoU, as confirmed by detection of the ExoU protein with specific antisera. The 50% lethal dose of
exoU
-expressing strains was significantly lower for all three
P. aeruginosa
isolates carrying plasmid pUCP19
exoUspcU
than for the isogenic
exoU
-negative strains. mRNA specific for ExoU was readily detected in the lungs of animals infected with the transformed
P. aeruginosa
strains. Introduction of the
exoU
gene confers a cytotoxic phenotype on some, but not all, otherwise-noncytotoxic
P. aeruginosa
strains and, for recombinant strains that could express ExoU, there was markedly increased virulence in a murine model of acute pneumonia and systemic spread.