bluuebunny/crossref_metadata_2025_split huggingface dataset:
SalmonellaHost Cell Invasion Emerged by Acquisition of a Mosaic of Separate Genetic Elements, IncludingSalmonellaPathogenicity Island 1 (SPI1), SPI5, andsopE2
Authors: Mirold Susanne , Ehrbar Kristin , Weissmüller Astrid , Prager Rita , Tschäpe Helmut , Rüssmann Holger , Hardt Wolf-Dietrich 
Published: July 2002

ABSTRACTSalmonellaspp. possess a conserved type III secretion system encoded within the pathogenicity island 1 (SPI1; centisome 63), which mediates translocation of effector proteins into the host cell cytosol to trigger responses such as bacterial internalization. Several translocated effector proteins are encoded in other regions of theSalmonellachromosome. It remains unclear how this complex chromosomal arrangement of genes for the type III apparatus and the effector proteins emerged and how the different effector proteins cooperate to mediate virulence. By Southern blotting, PCR, and phylogenetic analyses of highly diverseSalmonellaspp., we show here that effector protein genes located in the core of SPI1 are present in allSalmonellalineages. Surprisingly, the same holds true for several effector protein genes located in distant regions of theSalmonellachromosome, namely,sopB(SPI5, centisome 20),sopD(centisome 64), andsopE2(centisomes 40 to 42). Our data demonstrate thatsopB,sopD,andsopE2, along with SPI1, were already present in the last common ancestor of all contemporarySalmonellaspp. Analysis ofSalmonellamutants revealed that host cell invasion is mediated by SopB, SopE2, and, in the case ofSalmonella entericaserovar Typhimurium SL1344, by SopE: asopB sopEsopE2-deficient triple mutant was incapable of inducing membrane ruffling and was >100-fold attenuated in host cell invasion. We conclude that host cell invasion emerged early during evolution by acquisition of a mosaic of genetic elements (SPI1 itself, SPI5 [sopB], andsopE2) and that the last common ancestor of all contemporarySalmonellaspp. was probably already invasive.
Conservative Duplication of Spindle Poles during Meiosis in
Saccharomyces cerevisiae
Authors: Wesp Andreas , Prinz Susanne , Fink Gerald R. 
Published: July 2002

ABSTRACT

During sporulation in diploid
Saccharomyces cerevisiae,
spindle pole bodies acquire the so-called meiotic plaque, a prerequisite for spore formation. Mpc70p is a component of the meiotic plaque and is thus essential for spore formation. We show here that
MPC70/mpc70
heterozygous strains most often produce two spores instead of four and that these spores are always nonsisters. In wild-type strains, Mpc70p localizes to all four spindle pole bodies, whereas in
MPC70/mpc70
strains Mpc70p localizes to only two of the four spindle pole bodies, and these are always nonsisters. Our data can be explained by conservative spindle pole body distribution in which the two newly synthesized meiosis II spindle pole bodies of
MPC70/mpc70
strains lack Mpc70p.
Allelic Diversity and Recombination in
Campylobacter jejuni
Authors: Suerbaum Sebastian , Lohrengel Marc , Sonnevend Agnes , Ruberg Florian , Kist Manfred 
Published: July 2002

ABSTRACT

The allelic diversity and population structure of
Campylobacter jejuni
were studied by multilocus nucleotide sequence analysis. Sequences from seven housekeeping genes were obtained from 32
C. jejuni
isolates isolated from enteritis patients in Germany, Hungary, Thailand, and the United States. Also included was strain NCTC 11168, the complete genomic sequence of which has recently been published. For all loci analyzed, multiple strains carried identical alleles. The frequency of synonymous and nonsynonymous sequence polymorphisms was low. The number of unique alleles per locus ranged from 9 to 15. These alleles occurred in 31 different combinations (sequence types), so that all but two pairs of strains could be distinguished from each other. Sequences were analyzed for evidence of recombination by the homoplasy test and split decomposition. These analyses showed that intraspecific recombination is frequent in
C. jejuni
and has generated extensive diversity of allelic profiles from a small number of polymorphic nucleotides.
Chlorobium tepidum
Mutant Lacking Bacteriochlorophyll
c
Made by Inactivation of the
bchK
Gene, Encoding Bacteriochlorophyll
c
Synthase
Authors: Frigaard Niels-Ulrik , Voigt Ginny D. , Bryant Donald A. 
Published: July 2002

ABSTRACT

The gene encoding bacteriochlorophyll (BChl)
c
synthase was identified by insertional inactivation in the photosynthetic green sulfur bacterium
Chlorobium tepidum
and was named
bchK
. The
bchK
mutant of
C. tepidum
was rusty-orange in color and completely lacked BChl
c
. Because of the absence of the BChl
c
antenna, the mutant grew about seven times slower than the wild type at light intensities that were limiting to the wild type (<90 μmol m
−2
s
−1
). Various pheophorbides, which probably represent precursors of BChl
c
which had lost magnesium, accumulated in the mutant cells. A small fraction of these pheophorbides were apparently esterified by the remaining chlorophyll (Chl)
a
and BChl
a
synthases in cells. The amounts of BChl
a
, Chl
a
, isoprenoid quinones, carotenoids, Fenna-Matthews-Olson protein, and chlorosome envelope protein CsmA were not significantly altered on a cellular basis in the mutant compared to in the wild type. This suggests that the BChl
a
antennae, photosynthetic reaction centers, and remaining chlorosome components were essentially unaffected in the mutant. Electron microscopy of thin sections revealed that the mutant lacked normal chlorosomes. However, a fraction containing vestigial chlorosomes, denoted “carotenosomes,” was partly purified by density centrifugation; these structures contained carotenoids, isoprenoid quinones, and a 798-nm-absorbing BChl
a
species that is probably protein associated. Because of the absence of the strong BChl
c
absorption found in the wild type, the
bchK
mutant should prove valuable for future analyses of the photosynthetic reaction center and of the roles of BChl
a
in photosynthesis in green bacteria. An evolutionary implication of our findings is that the photosynthetic ancestor of green sulfur bacteria could have evolved without chlorosomes and BChl
c
and instead used only BChl
a
-containing proteins as the major light-harvesting antennae.
In Vivo DNA-Binding and Oligomerization Properties of the
Shigella flexneri
AraC-Like Transcriptional Regulator VirF as Identified by Random and Site-Specific Mutagenesis
Authors: Porter Megan E. , Dorman Charles J. 
Published: July 2002

ABSTRACT

In
Shigella flexneri
expression of the plasmid-encoded virulence genes is regulated via a complex mechanism involving both environmental signals and specific transactivators. The primary regulator protein, VirF, is a member of the AraC family of transcription factors and shares with other AraC-like proteins a conserved carboxy-terminal domain thought to be important for DNA binding. Random and site-directed mutagenesis of the
virF
gene encoding VirF yielded a number of mutations along the length of the protein which severely affected the ability of VirF to activate gene expression. The mutant proteins were shown to be affected in their ability to activate the virulence genes
virB
and
icsA
, both known to be regulated directly by VirF, as well as the
virB
-dependent virulence gene
mxiC
. Mutating key residues predicted to be important for DNA recognition had a significant negative effect, thereby suggesting that VirF interacts with its target sequence via two helix-turn-helix motifs. Two mutants that were dominant negative when coexpressed with the wild-type VirF protein were also isolated, indicating a role for protein-protein oligomerization in normal VirF function.
A Bacterial Signal Transduction System Controls Genetic Exchange and Motility
Authors: Lang Andrew S. , Beatty J. Thomas 
Published: July 2002

ABSTRACT

The bacterium
Rhodobacter capsulatus
is capable of an unusual form of genetic exchange, mediated by a transducing bacteriophage-like particle called the gene transfer agent (GTA). GTA production by
R. capsulatus
is controlled at the level of transcription by a cellular two-component signal transduction system that includes a putative histidine kinase (CckA) and response regulator (CtrA). We found that, in addition to regulating genetic exchange by
R. capsulatus
, this signal transduction system controls motility. As with the regulation of GTA production, the control of motility by CckA and CtrA occurs through modulation of gene transcription. Disruptions of the
cckA
and
ctrA
genes resulted in a loss of class II, class III, and class IV flagellar gene transcripts, suggesting that
cckA
and
ctrA
function in motility as class I flagellar genes. We also found that, analogous to the GTA genes, transcription of
R. capsulatus
flagellar genes appears to be growth phase dependent: class II flagellar gene transcripts are maximal in the mid-log phase of the culture growth cycle, whereas class III gene transcripts are maximal in the late-log phase of growth. We speculate that coordinate regulation of motility and GTA-mediated genetic exchange in
R. capsulatus
exists because these two processes are complementary mechanisms for cells to cope with unfavorable conditions in natural environments.
Molecular Typing of
Mycobacterium bovis
Isolates from Cameroon
Authors: Njanpop-Lafourcade Berthe M. , Inwald Jacqueline , Ostyn Annick , Durand Benoı̂t , Hughes Steven , Thorel Marie-Françoise , Hewinson Glyn , Haddad Nadia 
Published: July 2002

ABSTRACT

In order to gain a better understanding of the molecular epidemiology of
Mycobacterium bovis
isolates in Cameroon, 75 isolates of
M. bovis
collected in three provinces of northern Cameroon were studied by spoligotyping. For 65 of these isolates, typing was also carried out by pulsed-field gel electrophoresis (PFGE) with
Dra
I, and 18 of the isolates were also typed by restriction fragment length polymorphism (RFLP) analysis with probe IS
6110
-RHS. Molecular typing of the isolates by these techniques revealed a high degree of homogeneity, with 10 spoligotypes for 75 isolates, four PFGE profiles for 65 isolates, and three RFLP types for 18 isolates. Some types were present in the three different provinces, while some were confined to one or two areas. These results suggest that geographical mapping of
M. bovis
strains could be helpful for the control of bovine tuberculosis at the regional level. An interesting feature of all the spoligotypes was the absence of spacer 30, suggesting a common origin for all of the Cameroon isolates tested; an evolutionary scenario for the isolates is discussed. In addition, a comparison of the three techniques showed that for
M. bovis
strain differentiation in Cameroon and in surrounding countries, spoligotyping would be a more discriminating and practical tool for molecular typing than the other two techniques used in this study.
Automated Ribotyping Provides Rapid Phylogenetic Subgroup Affiliation of Clinical Extraintestinal Pathogenic
Escherichia coli
Strains
Authors: Clermont Olivier , Cordevant Christophe , Bonacorsi Stephane , Marecat Armelle , Lange Marc , Bingen Edouard 
Published: July 2002

ABSTRACT
Using the automated Riboprinter system, we have initiated the construction of an electronic Riboprint database composed of 72 ECOR reference strains and 15 archetypal virulent strains in order to provide a new simple molecular characterization method. More than 90% of the ECOR strains clustered in their original phylogenetic group. All but one of the archetypal virulent strains had a profile identical to that of one of the ECOR strains and could be easily affiliated with a phylogenetic group. This method appears to be an accurate and practical tool especially for investigating the genetic relationship between clinical extraintestinal pathogenic strains and B2 subgroup ECOR strains or archetypal pathotype strains.
Recurrent Soft Tissue Abscesses Caused by
Legionella cincinnatiensis
Authors: Gubler Jacques G. H. , Schorr Mirjam , Gaia V. , Zbinden R. , Altwegg M. 
Published: July 2002

ABSTRACT

Recurrent soft tissue abscesses of the jaw, wrist, and arm developed in a 73-year-old housewife with nephrotic syndrome and immunoglobulin A(κ) gammopathy of unknown etiology. Conventional cultures remained negative, despite visible gram-negative rods on microscopy. Broad-spectrum PCR revealed
Legionella cincinnatiensis
, which was confirmed by isolation of the organism on special
Legionella
medium. Infections due to
Legionella
species outside the lungs are rare.
L. cincinnatiensis
has been implicated in only four cases of clinical infection; these involved the lungs in three patients and the central nervous system in one patient. We conclude that broad-spectrum PCR can be a valuable tool for the evaluation of culture-negative infections with a high probability of bacterial origin and that
Legionella
might be an underdiagnosed cause of pyogenic soft tissue infection.
One Case Each of Recurrent Meningitis and Hemoperitoneum Infection with
Ralstonia mannitolilytica
Authors: Vaneechoutte Mario , De Baere Thierry , Wauters Georges , Steyaert Sophia , Claeys Geert , Vogelaers Dirk , Verschraegen Gerda 
Published: July 2002

ABSTRACT

Two clinical cases of infection with
Ralstonia mannitolilytica
are described: a recurrent meningitis on an implanted intraventricular catheter and an infected hemoperitoneum as a complication of a cholangiocarcinoma. The strains were first misidentified as
Pseudomonas fluorescens
and
Burkholderia cepacia
. Further testing lead to the identification as
Ralstonia pickettii
biovar 3/“
thomasii
,” which was recently shown to represent a separate species,
R. mannitolilytica
(List editor N. Weiss, Int. J. Syst. Evol. Microbiol. 51:795–796, 2001), originally described as
R. mannitolytica
(De Baere et al., Int. J. Syst. Evol. Microbiol. 51:547–558, 2001).
R. mannitolilytica
can be distinguished from all described
Ralstonia
species by its acidification of
d
-arabitol and mannitol and by its lack of nitrate reduction and of alkalinization of tartrate. In order to determine the true prevalence of infections with this species, colistin-resistant “
P. fluorescens
” strains and strains growing on
B. cepacia
selective medium deserve further attention.
Are Two
Cryptococcus neoformans
Strains Epidemiologically Linked?
Authors: Garcia-Hermoso Dea , Dromer Françoise , Mathoulin-Pelissier Simone , Janbon Guilhem 
Published: July 2002

ABSTRACT

The aim of this study was to standardize a method to determine whether two strains of
Cryptococcus neoformans
could be considered epidemiologically linked. We hypothesized that strains isolated from the same patient were epidemiologically linked and that those isolated from different patients were unrelated. We used 17 environmental isolates and 97 clinical isolates from 31 patients diagnosed with cryptococcosis (1 to 14 isolates per patient). Using the plasmid pCnTel-1-labeled probe CENTEL, we were able to differentiate some unrelated strains that yielded the same hybridization profile with the
C. neoformans
middle-repetitive-element CNRE-1 probe. The genetic distances separating the strains isolated from the same patient and those separating the strains isolated from different patients were estimated, and the results obtained with the two probes were compared. Analysis of the results enabled the calculation of two Dice coefficient limits defining the zones containing the pairs of linked strains and the pairs of unrelated strains, as well as an intermediate uncertainty zone for which it was not possible to establish whether the pairs of strains were linked.
Cryptococcus laurentii
Fungemia in a Premature Neonate
Authors: Cheng Ming-Fang , Chiou Christine C. , Liu Yung-Ching , Wang Hao-Zan , Hsieh Kai-Sheng 
Published: July 2002

ABSTRACT

Cryptococcus
spp. other than
Cryptococcus neoformans
are generally considered nonpathogenic to humans. There are only 15 case reports of disease in humans caused by
Cryptococcus laurentii
infection. Underlying diseases and predisposing risk factors seem to play an important role in these cases. Our patient is the first case of an extremely low birth weight infant with
C. laurentii
fungemia reported in the English literature. In our case, the MIC of amphotericin B for
C. laurentii
was 0.25 to 1 μg/ml and the patient had a good outcome following the administration of amphotericin B at 10 mg/kg combined with central venous catheter removal. There will undoubtedly be an increasing occurrence of unusual fungal infections accompanying further advances in medicine. A high degree of suspicion and improvements in the techniques for culture and identification will contribute to the earlier diagnosis and treatment of unusual fungal infections.
Evaluation of Current Methods for Detection of Staphylococci with Reduced Susceptibility to Glycopeptides
Authors: Walsh Timothy R. , Bolmström Anne , Qwärnström Anette , Ho Phion , Wootton Mandy , Howe Robin A. , MacGowan Alasdair P. , Diekema Dan 
Published: July 2002

ABSTRACT

The sensitivity and specificity of seven methods (agar dilution, broth microdilution, Etest at 0.5 and 2.0 McFarland (McF) inocula, two agar screening methods, and population studies [PS]) were evaluated in a double-blind study involving 284 methicillin-resistant
Staphylococcus aureus
(MRSA) strains and 45
Staphylococcus
strains with reduced susceptibilities to vancomycin (SRSV). The results were compared to the population analysis profile-area under the curve ratio method (PAP-AUC ratio compared to that of Mu3) as described by Wootton et al. The agar screening method using brain heart infusion agar (6 μg of vancomycin per ml) gave a sensitivity of 22% and a specificity of 97%. A similar method using Mueller-Hinton agar (5 μg of vancomycin per ml) gave a sensitivity of 20% and a specificity of 99%. The PS method detected 34 false positives (12%) and gave a sensitivity of 71% and a specificity of 88%. Etest using 0.5 and 2.0 McF inocula gave sensitivities and specificities of 82 and 93% and of 96 and 97%, respectively. The best Etest interpretative criteria for the 2.0 McF inoculum was ≥8 mg of vancomycin per liter and ≥8 μg teicoplanin per ml or ≥12 μg of teicoplanin per ml. The direct colony suspension inoculum for this method was found to be equally accurate in detecting (hetero-)glycopeptide-intermediate
S. aureus
compared to the overnight broth inoculum preparation method. Agar dilution and broth microdilution using the NCCLS breakpoint criteria for vancomycin gave sensitivities and specificities of 20 and 100% and of 11 and 100%, respectively. Using the Etest with a 2.0 McF inoculum, six different media were assessed against a selection of SRSV (
n
= 48) and MRSA (
n
= 12). Brain heart infusion agar yielded the highest sensitivity and specificity values: 88 and 88%, respectively.
Fluorogenic PCR-Based Quantitative Detection of a Murine Pathogen,
Helicobacter hepaticus
Authors: Ge Zhongming , White Deborah A. , Whary Mark T. , Fox James G. 
Published: July 2002

ABSTRACT

Helicobacter hepaticus
infection in mice is being used as an animal model for elucidating the pathogenesis of gastrointestinal and biliary diseases in humans.
H. hepaticus
, which forms a spreading film on selective agar, is not amenable to routine quantitative counts of organisms in tissues using a CFU method. In this study, a fluorogenic PCR-based assay was developed to quantitatively detect
H. hepaticus
in mouse ceca and feces using the ABI Prism 7700 sequence detection system. A pair of primers and a probe for this assay were generated from the
H. hepaticus cdtB
gene (encoding subunit B of the
H. hepaticus
cytolethal distending toxin). Using this assay, the sensitivity for detection of
H. hepaticus
chromosomal DNA prepared from pure culture was 20 fg, which is equivalent to approximately 14 copies of the
H. hepaticus
genome based on an estimated genome size of ≈1.3 Mb determined by pulsed-field gel electrophoresis.
H. hepaticus
present in feces and cecal samples from
H. hepaticus
-infected mice was readily quantified. The selected PCR primers and probe did not generate fluorescent signals from eight other helicobacters (
H. canis
,
H. cineadi
,
H. felis, H. mustelae, H. nemestrinae, H. pullorum, H. pylori
, and
H. rodentium
)
.
A fluorescent signal was detected from 20 ng of
H. bilis
DNA but with much lower sensitivity (10
6
-fold) than from
H. hepaticus
DNA. Therefore, this assay can be used with high sensitivity and specificity to quantify
H. hepaticus
in experimentally infected mouse models as well as in naturally infected mice.
Genotyping of a Homogeneous Group of
Yersinia pestis
Strains Isolated in the United States
Authors: Huang Xiao-Zhe , Chu May C. , Engelthaler Dave M. , Lindler Luther E. 
Published: July 2002

ABSTRACT

Yersinia pestis
, the causative agent of deadly plague, is considered a reemerging infectious disease and a significant biological terrorism threat. The present project focused on epidemiological investigation of the genetic variability of well-documented strains of
Y. pestis
from the United States by pulsed-field gel electrophoresis (PFGE) and restriction fragment length polymorphism (RFLP) analysis with insertion sequences IS
100
and IS
285
as probes. We examined 37 U.S.
Y. pestis
strains and isolates of a single ribotype, ribotype B, recovered between 1939 and 1998 from patients, animals, and fleas. Our results showed that all isolates had similar PFGE patterns, but minor differences such as missing, additional, and shifted bands were found among almost all strains if they came from different parent strains. The 37 strains and isolates were divided into 26 PFGE types. RFLP analysis with IS
100
as a probe divided these strains and isolates into 16 types, with 43% belonging to IS
100
type 1. Typing with IS
285
as a probe was less specific and led to only four RFLP types, with 81% belonging to type 1. Similarity analysis with BioNumerics software showed that all strains shared ≥80, 86, and 91% similarities on dendrograms prepared from digitized PFGE, IS
100
RFLP analysis, and IS
285
RFLP analysis images, respectively. Our results demonstrate that PFGE offers an increased ability to discriminate between strains (Simpson's index of diversity, 0.98) and therefore can significantly improve epidemiological studies related to the origin of new plague isolates.
Impact of Human Immunodeficiency Virus Type 1 RNA Dimerization on Viral Infectivity and of Stem-Loop B on RNA Dimerization and Reverse Transcription and Dissociation of Dimerization from Packaging
Authors: Shen Ni , Jetté Louis , Liang Chen , Wainberg Mark A. , Laughrea Michael 
Published: July 2002

ABSTRACT

The kissing-loop domain (KLD) encompasses a stem-loop, named kissing-loop or dimerization initiation site (DIS) hairpin (nucleotides [nt] 248 to 270 in the human immunodeficiency virus type 1 strains HIV-1
Lai
and HIV-1
Hxb2
), seated on top of a 12-nt stem-internal loop called stem-loop B (nt 243 to 247 and 271 to 277). Destroying stem-loop B reduced genome dimerization by ∼50% and proviral DNA synthesis by ∼85% and left unchanged the dissociation temperature of dimeric genomic RNA. The most affected step of reverse transcription was plus-strand DNA transfer, which was reduced by ∼80%. Deleting nt 241 to 256 or 200 to 256 did not reduce genome dimerization significantly more than the destruction of stem-loop B or the DIS hairpin. We conclude that the KLD is nonmodular: mutations in stem-loop B and in the DIS hairpin have similar effects on genome dimerization, reverse transcription, and encapsidation and are also “nonadditive”; i.e., a larger deletion spanning both of these structures has the same effects on genome dimerization and encapsidation as if stem-loop B strongly impacted DIS hairpin function and vice versa. A C258G transversion in the palindrome of the kissing-loop reduced genome dimerization by ∼50% and viral infectivity by ∼1.4 log. Two mutations, CGCG261→U
UA
A261 (creating a weaker palindrome) and a Δ241–256 suppressor mutation, were each able to reduce genome dimerization but leave genome packaging unaffected.