bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Single Ala139-to-Glu Substitution in theRenibacterium salmoninarumVirulence-Associated Protein p57 Results in Antigenic Variation and Is Associated with Enhanced p57 Binding to Chinook Salmon Leukocytes
Authors: Wiens Gregory D. , Pascho Ron , Winton James R. 
Published: October 2002

ABSTRACTThe gram-positive bacteriumRenibacterium salmoninarumproduces relatively large amounts of a 57-kDa protein (p57) implicated in the pathogenesis of salmonid bacterial kidney disease. Antigenic variation in p57 was identified by using monoclonal antibody 4C11, which exhibited severely decreased binding toR. salmoninarumstrain 684 p57 and bound robustly to the p57 proteins of seven otherR. salmoninarumstrains. This difference in binding was not due to alterations in p57 synthesis, secretion, or bacterial cell association. The molecular basis of the 4C11 epitope loss was determined by amplifying and sequencing the two identical genes encoding p57,msa1andmsa2. The 5′ and coding sequences of the 684msa1andmsa2genes were identical to those of the ATCC 33209msa1andmsa2genes except for a single C-to-A nucleotide mutation. This mutation was identified in both themsa1andmsa2genes of strain 684 and resulted in an Ala139-to-Glu substitution in the amino-terminal region of p57. We examined whether this mutation in p57 altered salmonid leukocyte and rabbit erythrocyte binding activities.R. salmoninarumstrain 684 extracellular protein exhibited a twofold increase in agglutinating activity for chinook salmon leukocytes and rabbit erythrocytes compared to the activity of the ATCC 33209 extracellular protein. A specific and quantitative p57 binding assay confirmed the increased binding activity of 684 p57. Monoclonal antibody 4C11 blocked the agglutinating activity of the ATCC 33209 extracellular protein but not the agglutinating activity of the 684 extracellular protein. These results indicate that the Ala139-to-Glu substitution altered immune recognition and was associated with enhanced biological activity ofR. salmoninarum684 p57.
Characterization of ISRgn
1
, a Novel Insertion Sequence of the IS
3
Family Isolated from a Bacteriocin-Negative Mutant of
Ruminococcus gnavus
E1
Authors: Gomez Ana , Ladire Monique , Marcille Francoise , Nardi Michelle , Fons Michel 
Published: October 2002

ABSTRACT

ISRgn
1
, an insertion sequence of the IS3 family, has been identified in the genome of a bacteriocin-negative mutant of
Ruminococcus gnavus
E1. The copy number of ISRgn
1
in
R. gnavus
E1, as well as its distribution among phylogenetically E1-related strains, has been determined. Results obtained suggest that ISRgn
1
is not indigenous to the
R. gnavus
phylogenetic group but that it can transpose in this bacterium.
Worldwide Distribution of
Nitrosococcus oceani
, a Marine Ammonia-Oxidizing γ-Proteobacterium, Detected by PCR and Sequencing of 16S rRNA and
amoA
Genes
Authors: Ward Bess B. , O'Mullan Gregory D. 
Published: October 2002

ABSTRACT

Diversity of cultured ammonia-oxidizing bacteria in the γ-subdivision of the
Proteobacteria
was investigated by using strains isolated from various parts of the world ocean. All the strains were very similar to each other on the basis of the sequences of both the 16S rRNA and ammonia monooxygenase genes and could be characterized as a single species. Sequences were also cloned directly from environmental DNA from coastal Pacific and Atlantic sites, and these sequences represented the first
Nitrosococcus oceani
-like sequences obtained directly from the ocean. Most of the environmental sequences clustered tightly with those of the cultivated strains, but some sequences could represent new species of
Nitrosococcus
. These findings imply that organisms similar to the cultivated
N. oceani
strains have a worldwide distribution.
Coadministration of an Interleukin-12 Gene and aTrypanosoma cruziGene Improves Vaccine Efficacy
Authors: Katae Masaharu , Miyahira Yasushi , Takeda Kazuyoshi , Matsuda Hironori , Yagita Hideo , Okumura Ko , Takeuchi Tsutomu , Kamiyama Tsuneo , Ohwada Akihiko , Fukuchi Yoshinosuke , Aoki Takashi 
Published: October 2002

ABSTRACTWe tested the immunogenicity of twoTrypanosoma cruziantigens injected into mice in the form of DNA vaccine. Immunization with DNA encoding dihydroorotate dehydrogenase did not confer protective immunity in all mouse strains tested. Immunization with DNA encoding trans-sialidase surface antigen (TSSA) protected C57BL/6 (H-2b) mice but not BALB/c (H-2d) or C3H/Hej (H-2k) mice against lethalT. cruziinfection. In vivo depletion of CD4+or CD8+T cells abolished the protective immunity elicited by TSSA gene in C57BL/6 mice. Enzyme-linked immunospot assay with splenocytes fromT. cruzi-infected mice or TSSA gene-vaccinated mice identified anH-2Kb-restricted antigenic peptide, ANYNFTLV. The CD8+-T-cell line specific for this peptide could recognizeT. cruzi-infected cells in vitro and could protect naive mice from lethal infection when adoptively transferred. Coadministration of the interleukin-12 (IL-12) gene with the TSSA gene facilitated the induction of ANYNFTLV-specific CD8+T cells and improved the vaccine efficacy against lethalT. cruziinfection. These results reinforced the utility of immunomodulatory adjuvants such as IL-12 gene for eliciting protective immunity against intracellular parasites by DNA vaccination.
Effect of
katG
Mutations on the Virulence of
Mycobacterium tuberculosis
and the Implication for Transmission in Humans
Authors: Pym Alexander S. , Saint-Joanis Brigitte , Cole Stewart T. 
Published: October 2002

ABSTRACT

The usefulness of isoniazid (INH), a key component of short-course chemotherapy of tuberculosis, is threatened by the emergence of drug-resistant strains of
Mycobacterium tuberculosis
with mutations in the
katG
gene. It is shown here that the most commonly occurring KatG mutation, where Ser 315 is replaced by Thr (S315T), is associated with clinically significant levels of INH resistance. In contrast to another resistant isolate, in which Pro replaces Thr 275, the S315T mutant produces active catalase-peroxidase and is virulent in the mouse model of the disease, indicating that a significant loss of bacterial fitness does not result from this frequent mutation. The implications of this finding for the transmission and reactivation of multidrug-resistant strains of
M. tuberculosis
are severe.
Anthrax Edema Toxin Requires Influx of Calcium for Inducing Cyclic AMP Toxicity in Target Cells
Authors: Kumar Praveen , Ahuja Nidhi , Bhatnagar Rakesh 
Published: October 2002

ABSTRACTThe anthrax edema toxin comprises two proteins: protective antigen and edema factor. Anthrax protective antigen binds to the receptors on the surface of target cells and facilitates the entry of edema factor into these target cells. Edema factor (EF) is an adenylate cyclase that catalyzes the synthesis of cyclic AMP (cAMP) in the cytosol of the host cells. In this study, we examined the requirement of extracellular calcium for anthrax edema toxin-induced toxicity in host cells. The cAMP response generated by edema toxin was analyzed in a variety of cells, including CHO, macrophage-like RAW264.7, human neutrophils, and human lymphocytes. Our investigations reveal that after EF reaches the cell cytosol, a rapid influx of calcium is triggered in the host cell that has a pivotal role in determining the cAMP response of the affected cells. Although the cAMP response generated by edema toxin in different cell types varied in intensity and in the time of initiation, the influx of calcium invariably preceded cAMP accumulation. Agents that blocked the uptake of calcium also inhibited edema toxin-induced accumulation of cAMP in the host cells. This is the first report that demonstrates that edema toxin induces accumulation of cAMP in lymphocytes. By accumulating cAMP, a potent inhibitor of immune cell function, edema toxin may actually be poisoning the immune system and thus facilitating the survival of the bacteria in the host.
Mycobacterium lepraeInfection in Monocyte-Derived Dendritic Cells and Its Influence on Antigen-Presenting Function
Authors: Hashimoto Ken , Maeda Yumi , Kimura Hiroaki , Suzuki Koichi , Masuda Akihiro , Matsuoka Masanori , Makino Masahiko 
Published: October 2002

ABSTRACTHost defense againstMycobacterium lepraeinfection is chiefly mediated by gamma interferon (IFN-γ)-secreting cytotoxic T cells. Since which antigen-presenting cell populations act to stimulate these T cells is not fully understood, we addressed the role of monocyte-derived dendritic cells (DCs). The DCs phagocytosedM. lepraeand expressed bacterially derived antigens (Ags), such as phenolic glycolipid 1 (PGL-1), in the cytoplasm, as well as on the cell surface. The expression of HLA-ABC and -DR Ags on DCs was down-regulated byM. lepraeinfection, and that of CD86 was up-regulated, but not as fully as byMycobacterium bovisBCG infection. Induction of CD83 expression required a large number ofM. lepraecells. When a multiplicity of infection of >40 was used, the DCs induced a significant proliferative and IFN-γ-producing response in autologous T cells. However, these responses were significantly lower than those induced by BCG- orMycobacterium avium-infected DCs. A CD40-mediated signaling inM. leprae-infected DCs up-regulated the expression of HLA Ags, CD86, and CD83 but did not enhance T-cell-stimulating ability. Therefore,M. leprae-infected DCs are less efficient at inducing T-cell responses. However, when the surface PGL-1 onM. leprae-infected DCs was masked by a monoclonal antibody, the DCs induced enhanced responses in both CD4+- and CD8+-T-cell subsets.M. lepraeis a unique pathogen which remains resistant to DC-mediated T-cell immunity, at least in the early stages of infection.
Simultaneous Expression of Different Variant-Specific Surface Proteins in Single
Giardia lamblia
Trophozoites during Encystation
Authors: Carranza Pedro G. , Feltes Gisela , Ropolo Andrea , Quintana Silvia M. C. , Touz María C. , Luján Hugo D. 
Published: October 2002

ABSTRACT

A novel variant-specific surface protein (VSP) from
Giardia
was identified using the monoclonal antibody 9B10, raised against purified cyst walls. VSP9B10B is preferentially induced during encystation and expressed simultaneously with other VSPs on the surface of encysting trophozoites. These results support the hypothesis that encystation and antigenic variation are processes that are mechanistically related.
Cellular Immunity, but Not Gamma Interferon, Is Essential for Resolution ofBabesia microtiInfection in BALB/c Mice
Authors: Clawson Michael L. , Paciorkowski Natalia , Rajan T. V. , La Vake Carson , Pope Conny , La Vake Morgan , Wikel Stephen K. , Krause Peter J. , Radolf Justin D. 
Published: October 2002

ABSTRACTA new strain ofBabesia microti(KR-1) was isolated from a Connecticut resident with babesiosis by hamster inoculation and adapted to C3H/HeJ and BALB/c mice. To examine the relative importance of humoral and cellular immunity for the control ofB. microtiinfection, we compared the course of disease in wild-type BALB/c mice with that in BALB/c SCID mice, JHD-null (B-cell-deficient) mice, and T-cell receptor αβ (TCRβ−/−) or gamma interferon (IFN-γ) (IFN-γ−/−) knockout mice following inoculation with the KR-1-strain. SCID mice and TCRαβ knockouts sustained a severe but nonlethal parasitemia averaging 35 to 45% infected erythrocytes. IFN-γ-deficient mice developed a less severe parasitemia but were able to clear the infection. In contrast, in six of eight JHD-null mice, the levels of parasitemia were indistinguishable from those in the wild-type animals. These data indicate that cellular immunity is critical for the clearance ofB. microtiin BALB/c mice but that disease resolution can occur even in the absence of IFN-γ.
Identification of Genes Affecting
Salmonella enterica
Serovar Enteritidis Infection of Chicken Macrophages
Authors: Zhao Yixian , Jansen Ruud , Gaastra Wim , Arkesteijn Ger , van der Zeijst Bernard A. M. , van Putten Jos P. M. 
Published: October 2002

ABSTRACT

Screening of 7,680
Salmonella enterica
serovar Enteritidis mutants for attenuation in a chicken macrophage infection model yielded a series of mutants including several with defects in previously unrecognized
Salmonella
virulence genes. One of the newly identified genes was the
pbpA2
gene, belonging to the penicillin binding protein gene family.
Identification of
Bacillus subtilis
CysL, a Regulator of the
cysJI
Operon, Which Encodes Sulfite Reductase
Authors: Guillouard Isabelle , Auger Sandrine , Hullo Marie-Françoise , Chetouani Farid , Danchin Antoine , Martin-Verstraete Isabelle 
Published: October 2002

ABSTRACT

The way in which the genes involved in cysteine biosynthesis are regulated is poorly characterized in
Bacillus subtilis
. We showed that CysL (formerly YwfK), a LysR-type transcriptional regulator, activates the transcription of the
cysJI
operon, which encodes sulfite reductase. We demonstrated that a
cysL
mutant and a
cysJI
mutant have similar phenotypes. Both are unable to grow using sulfate or sulfite as the sulfur source. The level of expression of the
cysJI
operon is higher in the presence of sulfate, sulfite, or thiosulfate than in the presence of cysteine. Conversely, the transcription of the
cysH
and
cysK
genes is not regulated by these sulfur sources. In the presence of thiosulfate, the expression of the
cysJI
operon was reduced 11-fold, whereas the expression of the
cysH
and
cysK
genes was increased, in a
cysL
mutant. A
cis
-acting DNA sequence located upstream of the transcriptional start site of the
cysJI
operon (positions −76 to −70) was shown to be necessary for sulfur source- and CysL-dependent regulation. CysL also negatively regulates its own transcription, a common characteristic of the LysR-type regulators. Gel mobility shift assays and DNase I footprint experiments showed that the CysL protein specifically binds to
cysJ
and
cysL
promoter regions. This is the first report of a regulator of some of the genes involved in cysteine biosynthesis in
B. subtilis
.
Transposase-Dependent Formation of Circular IS256Derivatives inStaphylococcus epidermidisandStaphylococcus aureus
Authors: Loessner Isabel , Dietrich Katja , Dittrich Dorothea , Hacker Jörg , Ziebuhr Wilma 
Published: October 2002

ABSTRACTIS256is a highly active insertion sequence (IS) element of multiresistant staphylococci and enterococci. Here we show that, in aStaphylococcus epidermidisclinical isolate, as well as in recombinantStaphylococcus aureusandEscherichia colicarrying a single IS256insertion on a plasmid, IS256excises as an extrachromosomal circular DNA molecule. First, circles were identified that contained a complete copy of IS256. In this case, the sequence connecting the left and right ends of IS256was derived from flanking DNA sequences of the parental genetic locus. Second, circle junctions were detected in which one end of IS256was truncated. Nucleotide sequencing of circle junctions revealed that (i) either end of IS256can attack the opposite terminus and (ii) the circle junctions vary significantly in size. Upon deletion of the IS256open reading frame at the 3′ end and site-directed mutageneses of the putative DDE motif, circular IS256molecules were no longer detectable, which implicates the IS256-encoded transposase protein with the circularization of the element.
SoxRS Down-Regulation ofrobTranscription
Authors: Michán Carmen , Manchado Manuel , Pueyo Carmen 
Published: October 2002

ABSTRACTRob is regarded as a constitutively expressed protein, although little is known about howrobgene is regulated. We show here by reverse transcription-PCR that the transcriptional levels ofrobare strongly down-regulated in response to the superoxide-generating agent paraquat (PQ). Repression reached a maximum of 20-fold after 10 min exposure at 10 μM PQ. The magnitude ofrobrepression was comparable to that of induction quantified for the most sensitive SoxS targets. β-Galactosidase expression with therob2::lacZtranscriptional fusion indicates that down-regulation ofrobexpression takes place, at least in part, at the level of transcription initiation. Moreover, ca. 50% of therobmRNA was degraded in <1 min after the addition of rifampin to inhibit transcription. This intrinsic short half-life, which is of obvious benefit for a rapid down-regulation after transcription ceases, was unaffected by the addition of PQ. No repression was observed in asoxR-null strain, indicating that therobtranscript level might be negatively modulated by the intracellular amounts of SoxS protein. Gel retardation assays support the idea that in vivo SoxS would blockrobtranscription directly.
A New Type IV Secretion System Promotes Conjugal Transfer inAgrobacterium tumefaciens
Authors: Chen Lishan , Chen Yuching , Wood Derek W. , Nester Eugene W. 
Published: October 2002

ABSTRACTTwo DNA transfer systems encoded by the tumor-inducing (Ti) plasmid have been previously identified inAgrobacterium tumefaciens. ThevirBoperon is required for the transfer of transferred DNA to the plant host, and thetrbsystem encodes functions required for the conjugal transfer of the Ti plasmid between cells ofAgrobacterium. Recent availability of the genome sequence ofAgrobacteriumallowed us to identify a third system that is most similar to the VirB type IV secretion system ofBartonella henselae. We have designated this systemavhBforAgrobacteriumvirulence homologuevirB. TheavhBloci reside on pAtC58 and encode at least 10 proteins (AvhB2 through AvhB11), 7 of which display significant similarity to the corresponding virulence-associated VirB proteins of the Ti plasmid. However, the AvhB system is not required for tumor formation; rather, it mediates the conjugal transfer of the pAtC58 cryptic plasmid between cells ofAgrobacterium. This transfer occurs in the absence of the Ti plasmid-encoded VirB and Trb systems. Like the VirB system, AvhB products promote the conjugal transfer of the IncQ plasmid RSF1010, suggesting that these products comprise a mating-pair formation system. The presence of plasmid TiC58 or plasmid RSF1010 reduces the conjugal transfer efficiency of pAtC58 10- or 1,000-fold, respectively. These data suggest that complex substrate interactions exist among the three DNA transfer systems ofAgrobacterium.
N4 RNA Polymerase II, a Heterodimeric RNA Polymerase with Homology to the Single-Subunit Family of RNA Polymerases
Authors: Willis S. H. , Kazmierczak K. M. , Carter R. H. , Rothman-Denes L. B. 
Published: October 2002

ABSTRACTBacteriophage N4 middle genes are transcribed by a phage-coded, heterodimeric, rifampin-resistant RNA polymerase, N4 RNA polymerase II (N4 RNAPII). Sequencing and transcriptional analysis revealed that the genes encoding the two subunits comprising N4 RNAPII are translated from a common transcript initiating at the N4 early promoter Pe3. These genes code for proteins of 269 and 404 amino acid residues with sequence similarity to the single-subunit, phage-like RNA polymerases. The genes encoding the N4 RNAPII subunits, as well as a synthetic construct encoding a fusion polypeptide, have been cloned and expressed. Both the individually expressed subunits and the fusion polypeptide reconstitute functional enzymes in vivo and in vitro.
prbA
, a Gene Coding for an Esterase Hydrolyzing Parabens in
Enterobacter cloacae
and
Enterobacter gergoviae
Strains
Authors: Valkova Nelly , Lépine François , Bollet Claude , Dupont Maryse , Villemur Richard 
Published: October 2002

ABSTRACT

The new gene
prbA
encodes an esterase responsible for the hydrolysis of the ester bond of parabens in
Enterobacter cloacae
strain EM. This gene is located on the chromosome of strain EM and was cloned by several PCR approaches. The
prbA
gene codes for an immature protein of 533 amino acids, the first 31 of which represent a proposed signal peptide yielding a mature protein of a putative molecular mass of 54.6 kDa. This enzyme presents analogies with other type B carboxylesterases, mainly of eukaryotic origin. The cloning and expression of the
prbA
gene in a strain of
Escherichia coli
previously unable to hydrolyze parabens resulted in the acquisition of a hydrolytic capacity comparable to the original activity of strain EM, along with an increased resistance of the transformed strain to methyl paraben. The presence of homologues of
prbA
was tested in additional ubiquitous bacteria, which may be causative factors in opportunistic infections, including
Enterobacter gergoviae
,
Enterobacter aerogenes
,
Pseudomonas agglomerans
,
E. coli
,
Pseudomonas aeruginosa
, and
Burkholderia cepacia
. Among the 41 total strains tested, 2 strains of
E. gergoviae
and 1 strain of
Burkholderia cepacia
were able to degrade almost completely 800 mg of methyl paraben liter
−1
. Two strains of
E. gergoviae
, named G1 and G12, contained a gene that showed high homology to the
prbA
gene of
E. cloacae
and demonstrated comparable paraben esterase activities. The significant geographical distance between the locations of the isolated
E. cloacae
and
E. gergoviae
strains suggests the possibility of an efficient transfer mechanism of the
prbA
gene, conferring additional resistance to parabens in ubiquitous bacteria that represent a common source of opportunistic infections.
Transposition of Cyanobacterium Insertion Element ISY100inEscherichia coli
Authors: Urasaki Akihiro , Sekine Yasuhiko , Ohtsubo Eiichi 
Published: October 2002

ABSTRACTThe genome of the cyanobacteriumSynechocystissp. strain PCC6803 has nine kinds of insertion sequence (IS) elements, of which ISY100in 22 copies is the most abundant. A typical ISY100member is 947 bp long and has imperfect terminal inverted repeat sequences. It has an open reading frame encoding a 282-amino-acid protein that appears to have partial homology with the transposase encoded by a bacterial IS, IS630, indicating that ISY100belongs to the IS630family. To determine whether ISY100has transposition ability, we constructed a plasmid carrying the IPTG (isopropyl-β-d-thiogalactopyranoside)-inducible transposase gene at one site and mini-ISY100with the chloramphenicol resistance gene, substituted for the transposase gene of ISY100, at another site and introduced the plasmid into anEscherichia colistrain already harboring a target plasmid. Mini-ISY100transposed to the target plasmid in the presence of IPTG at a very high frequency. Mini-ISY100was inserted into the TA sequence and duplicated it upon transposition, as do IS630family elements. Moreover, the mini-ISY100-carrying plasmid produced linear molecules of mini-ISY100with the exact 3′ ends of ISY100and 5′ ends lacking two nucleotides of the ISY100sequence. No bacterial insertion elements have been shown to generate such molecules, whereas the eukaryotic Tc1/marinerfamily elements, Tc1and Tc3, which transpose to the TA sequence, have. These findings suggest that ISY100transposes to a new site through the formation of linear molecules, such as Tc1and Tc3, by excision. Some Tc1/marinerfamily elements leave a footprint with an extra sequence at the site of excision. No footprints, however, were detected in the case of ISY100, suggesting that eukaryotes have a system that repairs a double strand break at the site of excision by an end-joining reaction, in which the gap is filled with a sequence of several base pairs, whereas prokaryotes do not have such a system. ISY100transposes inE. coli, indicating that it transposes without any host factor other than the transposase encoded by itself. Therefore, it may be able to transpose in other biological systems.