bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bulk and Rhizosphere Soil Bacterial Communities Studied by Denaturing Gradient Gel Electrophoresis: Plant-Dependent Enrichment and Seasonal Shifts Revealed
Authors: Smalla K. , Wieland G. , Buchner A. , Zock A. , Parzy J. , Kaiser S. , Roskot N. , Heuer H. , Berg G. 
Published: July 2002

ABSTRACT

The bacterial rhizosphere communities of three host plants of the pathogenic fungus
Verticillium dahliae
, field-grown strawberry (
Fragaria ananassa
Duch.), oilseed rape (
Brassica napus
L.), and potato (
Solanum tuberosum
L.), were analyzed. We aimed to determine the degree to which the rhizosphere effect is plant dependent and whether this effect would be increased by growing the same crops in two consecutive years. Rhizosphere or soil samples were taken five times over the vegetation periods. To allow a cultivation-independent analysis, total community DNA was extracted from the microbial pellet recovered from root or soil samples. 16S rDNA fragments amplified by PCR from soil or rhizosphere bacterium DNA were analyzed by denaturing gradient gel electrophoresis (DGGE). The DGGE fingerprints showed plant-dependent shifts in the relative abundance of bacterial populations in the rhizosphere which became more pronounced in the second year. DGGE patterns of oilseed rape and potato rhizosphere communities were more similar to each other than to the strawberry patterns. In both years seasonal shifts in the abundance and composition of the bacterial rhizosphere populations were observed. Independent of the plant species, the patterns of the first sampling times for both years were characterized by the absence of some of the bands which became dominant at the following sampling times.
Bacillus megaterium
and
Arthrobacter
sp. were found as predominant populations in bulk soils. Sequencing of dominant bands excised from the rhizosphere patterns revealed that 6 out of 10 bands resembled gram-positive bacteria.
Nocardia
populations were identified as strawberry-specific bands.
Identification of Mur, an Atypical Peptidoglycan Hydrolase Derived fromLeuconostoc citreum
Authors: Cibik Recep , Tailliez Patrick , Langella Philippe , Chapot-Chartier Marie-Pierre 
Published: July 2002

ABSTRACTA gene encoding a protein homologous to known bacterialN-acetyl-muramidases has been cloned fromLeuconostoc citreumby a PCR-based approach. The encoded protein, Mur, consists of 209 amino acid residues with a calculated molecular mass of 23,821 Da including a 31-amino-acid putative signal peptide. In contrast to most of the other known peptidoglycan hydrolases,L. citreumMur protein does not contain amino acid repeats involved in cell wall binding. The purifiedL. citreumMur protein was shown to exhibit peptidoglycan-hydrolyzing activity by renaturing sodium dodecyl sulfate-polyacrylamide gel electrophoresis. An active chimeric protein was constructed by fusion ofL. citreumMur to the C-terminal repeat-containing domain (cA) of AcmA, the major autolysin ofLactococcus lactis. Expression of the Mur-cA fusion protein was able to complement anacmAmutation inL. lactis;normal cell separation after cell division was restored by Mur-cA expression.
Purification and Characterization of a Vulnificolysin-Like Cytolysin Produced byVibrio tubiashii
Authors: Kothary Mahendra H. , Delston Rachel B. , Curtis Sherill K. , McCardell Barbara A. , Tall Ben D. 
Published: July 2002

ABSTRACTAn extracellular cytolysin fromVibrio tubiashiiwas purified by sequential hydrophobic interaction chromatography with phenyl-Sepharose CL-4B and gel filtration with Sephacryl S-200. This protein is sensitive to heat and proteases, is inhibited by cholesterol, and has a molecular weight of 59,000 and an isoelectric point of 5.3. In addition to lysing various erythrocytes, it is cytolytic and/or cytotoxic to Chinese hamster ovary cells, Caco-2 cells, and Atlantic menhaden liver cells in tissue culture. Lysis of erythrocytes occurs by a multihit process that is dependent on temperature and pH. Twelve of the first 17 N-terminal amino acid residues (Asp-Asp-Tyr-Val-Pro-Val-Val-Glu-Lys-Val-Tyr-Tyr-Ile-Thr-Ser-Ser-Lys) are identical to those of theVibrio vulnificuscytolysin.
Microbial Population Structures in Soil Particle Size Fractions of a Long-Term Fertilizer Field Experiment
Authors: Sessitsch Angela , Weilharter Alexandra , Gerzabek Martin H. , Kirchmann Holger , Kandeler Ellen 
Published: July 2002

ABSTRACT

Soil structure depends on the association between mineral soil particles (sand, silt, and clay) and organic matter, in which aggregates of different size and stability are formed. Although the chemistry of organic materials, total microbial biomass, and different enzyme activities in different soil particle size fractions have been well studied, little information is available on the structure of microbial populations in microhabitats. In this study, topsoil samples of different fertilizer treatments of a long-term field experiment were analyzed. Size fractions of 200 to 63 μm (fine sand fraction), 63 to 2 μm (silt fraction), and 2 to 0.1 μm (clay fraction) were obtained by a combination of low-energy sonication, wet sieving, and repeated centrifugation. Terminal restriction fragment length polymorphism analysis and cloning and sequencing of 16S rRNA genes were used to compare bacterial community structures in different particle size fractions. The microbial community structure was significantly affected by particle size, yielding higher diversity of microbes in small size fractions than in coarse size fractions. The higher biomass previously found in silt and clay fractions could be attributed to higher diversity rather than to better colonization of particular species. Low nutrient availability, protozoan grazing, and competition with fungal organisms may have been responsible for reduced diversities in larger size fractions. Furthermore, larger particle sizes were dominated by α-
Proteobacteria
, whereas high abundance and diversity of bacteria belonging to the
Holophaga/Acidobacterium
division were found in smaller size fractions. Although very contrasting organic amendments (green manure, animal manure, sewage sludge, and peat) were examined, our results demonstrated that the bacterial community structure was affected to a greater extent by the particle size fraction than by the kind of fertilizer applied. Therefore, our results demonstrate specific microbe-particle associations that are affected to only a small extent by external factors.
Distribution of Antibody againstErysipelothrix rhusiopathiaein Cattle
Authors: Sawada Takuo , Hassanein Raafat , Yamamoto Tohru , Yoshida Takaharu 
Published: July 2002

ABSTRACTSerum samples collected from 854 cattle in nine prefectures of Japan, from Hokkaido to Okinawa, between 1988 and 1992 were examined for presence of antibodies againstErysipelothrix rhusiopathiaeby growth agglutination test. Most of the sera showed positive reactions, and the antibody titers ranged from below 4 to above 128. Seventy-six percent of the sera showed titers of 32 or above, and 34% showed titers of 128 or above. The titers had a tendency to be higher in the south and lower in the north and were clearly low in sera from areas with no swine industry. These results indicated that Japanese cattle had been infected withE. rhusiopathiaeand that clinical cases of the disease were possible.
Reduced Levels of Nitric Oxide Metabolites in Cerebrospinal Fluid Are Associated with Equine Protozoal Myeloencephalitis
Authors: Njoku Chinedu J. , Saville William J. A. , Reed Stephen M. , Oglesbee Michael J. , Rajala-Schultz Päivi J. , Stich Roger W. 
Published: July 2002

ABSTRACTEquine protozoal myeloencephalitis (EPM) is a disease of horses that is primarily associated with infection with the apicomplexanSarcocystis neurona. Infection with this parasite alone is not sufficient to induce the disease, and the mechanism of neuropathogenesis associated with EPM has not been reported. Nitric oxide (NO) functions as a neurotransmitter, a vasodilator, and an immune effector and is produced in response to several parasitic protozoa. The purpose of this work was to determine if the concentration of NO metabolites (NOx−) in the cerebrospinal fluid (CSF) is correlated with the development of EPM. CSF NOx−levels were measured before and after transport-stressed, acclimated, or dexamethasone-treated horses (n= 3 per group) were experimentally infected withS. neuronasporocysts. CSF NOx−levels were also compared between horses that were diagnosed with EPM after natural infection withS. neuronaand horses that did not have clinical signs of disease or that showed no evidence of infection with the parasite (n= 105). Among the experimentally infected animals, the mean CSF NOx−levels of the transport-stressed group, which had the most severe clinical signs, was reduced after infection, while these values were found to increase after infection in the remaining groups that had less severe signs of EPM. Under natural conditions, horses with EPM (n= 65) had a lower mean CSF NOx−concentration than clinically normal horses with antibodies (Abs) againstS. neurona(n= 15) in CSF, and horses that developed ataxia (n= 81) had a significantly lower mean CSF NOx−concentration than horses that did not have neurologic signs (n= 24). In conclusion, lower CSF NOx−levels were associated with clinical EPM, suggesting that measurement of CSF NOx−levels could improve the accuracy of diagnostic tests that are based upon detection ofS. neurona-specific Abs in CSF alone and that reduced NO levels could be causatively related to the development of EPM.
Identification and Characterization of the
scl
Gene Encoding a Group A
Streptococcus
Extracellular Protein Virulence Factor with Similarity to Human Collagen
Authors: Lukomski Slawomir , Nakashima Kazumitsu , Abdi Iman , Cipriano Vincent J. , Ireland Robin M. , Reid Sean D. , Adams Gerald G. , Musser James M. 
Published: July 2002

ABSTRACT

Group A
Streptococcus
(GAS) expresses cell surface proteins that mediate important biological functions such as resistance to phagocytosis, adherence to plasma and extracellular matrix proteins, and degradation of host proteins. An open reading frame encoding a protein of 348 amino acid residues was identified by analysis of the genome sequence available for a serotype M1 strain. The protein has an LPATGE sequence located near the carboxy terminus that matches the consensus sequence (LPXTGX) present in many gram-positive cell wall-anchored molecules. Importantly, the central region of this protein contains 50 contiguous Gly-X-X triplet amino acid motifs characteristic of the structure of human collagen. The structural gene (designated
scl
for streptococcal collagen-like) was present in all 50 GAS isolates tested, which together express 21 different M protein types and represent the breadth of genomic diversity in the species. DNA sequence analysis of the gene in these 50 isolates found that the number of contiguous Gly-X-X motifs ranged from 14 in serotype M6 isolates to 62 in a serotype M41 organism. M1 and M18 organisms had the identical allele, which indicates very recent horizontal gene transfer. The gene was transcribed abundantly in the logarithmic but not stationary phase of growth, a result consistent with the occurrence of a DNA sequence with substantial homology with a consensus Mga binding site immediately upstream of the
scl
open reading frame. Two isogenic mutant M1 strains created by nonpolar mutagenesis of the
scl
structural gene were not attenuated for mouse virulence as assessed by intraperitoneal inoculation. In contrast, the isogenic mutant derivative made from the M1 strain representative of the subclone most frequently causing human infections was significantly less virulent when inoculated subcutaneously into mice. In addition, both isogenic mutant strains had significantly reduced adherence to human A549 epithelial cells grown in culture. These studies identify a new extracellular GAS virulence factor that is widely distributed in the species and participates in adherence to host cells and soft tissue pathology.
In Vitro Responsiveness of γδ T Cells fromMycobacterium bovis-Infected Cattle to Mycobacterial Antigens: Predominant Involvement of WC1+Cells
Authors: Smyth Allister J. , Welsh Michael D. , Girvin R. Martyn , Pollock John M. 
Published: July 2002

ABSTRACTIt is generally accepted that protective immunity against tuberculosis is generated through the cell-mediated immune (CMI) system, and a greater understanding of such responses is required if better vaccines and diagnostic tests are to be developed. γδ T cells form a major proportion of the peripheral blood mononuclear cells (PBMC) in the ruminant system and, considering data from other species, may have a significant role in CMI responses in bovine tuberculosis. This study compared the in vitro responses of αβ and γδ T cells fromMycobacterium bovis-infected and uninfected cattle. The results showed that, following 24 h of culture of PBMC withM. bovis-derived antigens, the majority of γδ T cells from infected animals became highly activated (upregulation of interleukin-2R), while a lower proportion of the αβ T-cell population showed activation. Similar responses were evident to a lesser degree in uninfected animals. Study of the kinetics of this response showed that γδ T cells remained significantly activated for at least 7 days in culture, while activation of αβ T cells declined during that period. Subsequent analysis revealed that the majority of activated γδ T cells expressed WC1, a 215-kDa surface molecule which is not expressed on human or murine γδ T cells. Furthermore, in comparison with what was found for CD4+T cells,M. bovisantigen was found to induce strong cellular proliferation but relatively little gamma interferon release by purified WC1+γδ T cells. Overall, while the role of these cells in protective immunity remains unclear, their highly activated status in response toM. bovissuggests an important role in antimycobacterial immunity, and the ability of γδ T cells to influence other immune cell functions remains to be elucidated, particularly in relation to CMI-based diagnostic tests.
Limited Mycobacterial Infection of the Liver as a Consequence of Its Microanatomical Structure Causing Restriction of Mycobacterial Growth to Professional Phagocytes
Authors: Seiler Peter , Schwendener Reto A. , Bandermann Silke , Brinkmann Volker , Grode Leander , Kaufmann Stefan H. E. , Aichele Peter 
Published: July 2002

ABSTRACTAmong sites of extrapulmonary growth ofMycobacterium tuberculosis, the liver is the least infected. Our data suggest that this is due to the complete restriction of mycobacterial growth to liver macrophages. Unlike in organs more persistently seeded byM. tuberculosis, in the liver the bacteria do not infect cell types other than professional phagocytes.
PerR Controls Oxidative Stress Resistance and Iron Storage Proteins and Is Required for Virulence in
Staphylococcus aureus
Authors: Horsburgh Malcolm J. , Clements Mark O. , Crossley Howard , Ingham Eileen , Foster Simon J. 
Published: July 2002

ABSTRACT

The
Staphylococcus aureus
genome encodes three ferric uptake regulator (Fur) homologues: Fur, PerR, and Zur. To determine the exact role of PerR, we inactivated the gene by allelic replacement using a kanamycin cassette, creating strain MJH001 (
perR
). PerR was found to control transcription of the genes encoding the oxidative stress resistance proteins catalase (KatA), alkyl hydroperoxide reductase (AhpCF), bacterioferritin comigratory protein (Bcp), and thioredoxin reductase (TrxB). Furthermore, PerR regulates transcription of the genes encoding the iron storage proteins ferritin (Ftn) and the ferritin-like Dps homologue, MrgA. Transcription of
perR
was autoregulated, and PerR repressed transcription of the iron homeostasis regulator Fur, which is a positive regulator of catalase expression. PerR functions as a manganese-dependent, transcriptional repressor of the identified regulon. Elevated iron concentrations produced induction of the PerR regulon. PerR may act as a peroxide sensor, since addition of external hydrogen peroxide to 8325-4 (wild type) resulted in increased transcription of most of the PerR regulon, except for
fur
and
perR
itself. The PerR-regulated
katA
gene encodes the sole catalase of
S. aureus,
which is an important starvation survival determinant but is surprisingly not required for pathogenicity in a murine skin abscess model of infection. In contrast, PerR is not necessary for starvation survival but is required for full virulence (
P
< 0.005) in this model of infection. PerR of
S. aureus
may act as a redox sentinel protein during infection, analogous to the in vitro activities of OxyR and PerR of
Escherichia coli
and
Bacillus subtilis
, respectively. However, it differs in its response to the metal balance within the cell and has the added capability of regulating iron uptake and storage.
Relationships between
Staphylococcus aureus
Genetic Background, Virulence Factors,
agr
Groups (Alleles), and Human Disease
Authors: Jarraud Sophie , Mougel Christophe , Thioulouse Jean , Lina Gerard , Meugnier Hélène , Forey Françoise , Nesme Xavier , Etienne Jerome , Vandenesch François 
Published: July 2002

ABSTRACT

The expression of most
Staphylococcus aureus
virulence factors is controlled by the
agr
locus, which encodes a two-component signaling pathway whose activating ligand is an
agr
-encoded autoinducing peptide (AIP). A polymorphism in the amino acid sequence of the AIP and of its corresponding receptor divides
S. aureus
strains into four major groups. Within a given group, each strain produces a peptide that can activate the
agr
response in the other member strains, whereas the AIPs belonging to different groups are usually mutually inhibitory. We investigated a possible relationship between
agr
groups and human
S. aureus
disease by studying 198
S. aureus
strains isolated from 14 asymptomatic carriers, 66 patients with suppurative infection, and 114 patients with acute toxemia. The
agr
group and the distribution of 24 toxin genes were analyzed by PCR, and the genetic background was determined by means of amplified fragment length polymorphism (AFLP) analysis. The isolates were relatively evenly distributed among the four
agr
groups, with 61 strains belonging to
agr
group I, 49 belonging to group II, 43 belonging to group III, and 45 belonging to group IV. Principal coordinate analysis performed on the AFLP distance matrix divided the 198 strains into three main phylogenetic groups, AF1 corresponding to strains of
agr
group IV, AF2 corresponding to strains of
agr
groups I and II, and AF3 corresponding to strains of
agr
group III. This indicated that the
agr
type was linked to the genetic background. A relationship between genetic background,
agr
group, and disease type was observed for several toxin-mediated diseases: for instance,
agr
group IV strains were associated with generalized exfoliative syndromes, and phylogenetic group AF1 strains with bullous impetigo. Among the suppurative infections, endocarditis strains mainly belonged to phylogenetic group AF2 and
agr
groups I and II. While these results do not show a direct role of the
agr
type in the type of human disease caused by
S. aureus
, the
agr
group may reflect an ancient evolutionary division of
S. aureus
in terms of this species’ fundamental biology.
Molecular Cloning of thefurGene fromActinobacillus actinomycetemcomitans
Authors: Haraszthy V. I. , Lally E. T. , Haraszthy G. G. , Zambon J. J. 
Published: July 2002

ABSTRACTIn several bacterial species, iron availability in host tissues is coordinated with the expression of virulence determinants through thefurgene product. Initial experiments showed that a clonedEscherichia coli furgene probe hybridized to Southern blots ofActinobacillus actinomycetemcomitansstrain JP2 (serotype b) chromosomal DNA. TheA. actinomycetemcomitans furgene was then cloned utilizing partial functional complementation of thefurmutant inE. colistrain H1780. Analysis of the cloned DNA sequence revealed a 438-bp open reading frame with a deduced 146-amino-acid sequence exhibiting 80% identity toHaemophilus influenzaeFur and 62% identity toE. coliFur. The pUCAafurgene probe (generated from JP2 serotype b) hybridized to representatives from all fiveA. actinomycetemcomitansserotypes as well as to two strains derived from monkeys, suggesting thatfuris widely distributed inA. actinomycetemcomitans.Open reading frames having >70% identity with theE. coliandH. influenzae flavodoxinandgyrase Agenes, respectively, were found. Expression of theA. actinomycetemcomitans furgene product repressedfiuexpression and siderophore production inE. coli. A gel shift assay demonstrated that the expressedA. actinomycetemcomitansFur protein bound the bacterialfurconsensus sequence. Further characterization of thefurgene product inA. actinomycetemcomitansmay improve our understanding of its role in the pathogenesis of periodontal disease and may lead to specific therapeutic modalities.
Identification of the
Vibrio cholerae
Enterobactin Receptors VctA and IrgA: IrgA Is Not Required for Virulence
Authors: Mey Alexandra R. , Wyckoff Elizabeth E. , Oglesby Amanda G. , Rab Eva , Taylor Ronald K. , Payne Shelley M. 
Published: July 2002

ABSTRACT

The gram-negative enteric pathogen
Vibrio cholerae
requires iron for growth.
V. cholerae
has multiple iron acquisition systems, including utilization of heme and hemoglobin, synthesis and transport of the catechol siderophore vibriobactin, and transport of several siderophores that it does not itself make. One siderophore that
V. cholerae
transports, but does not make, is enterobactin. Enterobactin transport requires TonB and is independent of the vibriobactin receptor ViuA. In this study, two candidate enterobactin receptor genes,
irgA
(VC0475) and
vctA
(VCA0232), were identified by analysis of the
V. cholerae
genomic sequence. A single mutation in either of these genes did not significantly impair enterobactin utilization, but a strain defective in both genes did not use enterobactin. When either
irgA
or
vctA
was supplied on a plasmid, the ability of the
irgA vctA
double mutant to use enterobactin was restored. This indicates that both VctA and IrgA transport enterobactin. We also identify the genes
vctPDGC
, which are linked to
vctA
and encode a periplasmic binding protein-dependent ABC transport system that functions in the utilization of both enterobactin and vibriobactin (VCA0227-0230). An
irgA
::Tn
phoA
mutant strain, MBG40, was shown in a previous study to be highly attenuated and to have a strong colonization defect in an infant mouse model of
V. cholerae
infection (M. B. Goldberg, V. J. DiRita, and S. B. Calderwood, Infect. Immun. 58:55-60, 1990). In this work, a new
irgA
mutation was constructed, and this mutant strain was not significantly impaired in its ability to compete with the parental strain in infant mice and was not attenuated for virulence in an assay of 50% lethal dose. These data indicate that the virulence defect in MBG40 is not due to the loss of
irgA
function and that
irgA
is unlikely to be an important virulence factor.