bluuebunny/crossref_metadata_2025_split huggingface dataset:
Very-Short-Patch Repair in
Escherichia coli
Requires the
dam
Adenine Methylase
Authors: Bell Derek C. , Cupples Claire G. 
Published: July 2002

ABSTRACT

Strains of
Escherichia coli
which lack the
dam
-encoded adenine methylase are mutators due to a reduction in the efficiency of postreplication mismatch repair. In this study, we show that Dam
−
strains are also defective in very-short-patch repair, the system which corrects T/G mismatches arising from the deamination of 5-methylcytosine. This defect is associated with decreased levels of Vsr, the endonuclease which initiates short-patch repair. We also show that production of the
dcm
-encoded cytosine methylase is unaffected in Dam
−
strains. Since the
dcm
and
vsr
genes are cotranscribed, the regulation of Vsr by Dam is probably posttranscriptional.
Coupling of Asymmetric Division to Polar Placement of Replication Origin Regions in
Bacillus subtilis
Authors: Graumann Peter L. , Losick Richard 
Published: July 2002

ABSTRACT

Entry into sporulation in
Bacillus subtilis
is characterized by the formation of a polar septum, which asymmetrically divides the developing cell into forespore (the smaller cell) and mother cell compartments, and by migration of replication origin regions to extreme opposite poles of the cell. Here we show that polar septation is closely correlated with movement of replication origins to the extreme poles of the cell. Replication origin regions were visualized by the use of a cassette of tandem copies of
lacO
that had been inserted in the chromosome near the origin of replication and decorated with green fluorescent protein-LacI. The results showed that extreme polar placement of replication origin regions is not under sporulation control and occurred in stationary phase under conditions under which entry into sporulation was prevented. On the other hand, the formation of a polar septum, which is under sporulation control, was almost invariably associated with the presence of a replication origin region in the forespore. Moreover, cells in which the polar placement of origin regions was perturbed by deletion of the gene (
smc
) for the structural maintenance of chromosomes (SMC) protein were impaired in polar division. A small proportion (≈1%) of the mutant cells were able to undergo asymmetric division, but the forespore compartment of these exceptional cells was generally observed to contain a replication origin region. Immunofluorescence microscopy experiments indicated that the block in polar division caused by the absence of SMC occurred at or prior to the step of bipolar Z-ring formation by the cell division protein FtsZ. A model is discussed in which polar division is under the dual control of sporulation and an event associated with the placement of a replication origin at the cell pole.
DNA-Binding Activity of Amino-Terminal Domains of the
Bacillus subtilis
AbrB Protein
Authors: Xu Ke , Strauch Mark A. 
Published: July 2002

ABSTRACT
Two truncated variants of AbrB, comprising either its first 53 (AbrBN53) or first 55 (AbrBN55) amino acid residues, were constructed and purified. Noncovalently linked homodimers of the truncated variants exhibited very weak DNA-binding activity. Cross-linking AbrBN55 dimers into tetramers and higher-order multimers (via disulfide bonding between penultimate cysteine residues) resulted in proteins having DNA-binding affinity comparable to and DNA-binding specificity identical to those of intact, wild-type AbrB. These results indicate that the DNA recognition and specificity determinants of AbrB binding lie solely within its N-terminal amino acid sequence.
Positive Selection of Mutations Leading to Loss or Reduction of Transcriptional Activity of PrfA, the Central Regulator ofListeria monocytogenesVirulence
Authors: Herler M. , Bubert A. , Goetz M. , Vega Y. , Vazquez-Boland J. A. , Goebel W. 
Published: July 2002

ABSTRACTTranscription factor PrfA controls the expression of virulence genes essential forListeria monocytogenespathogenesis. To gain insight into the structure-function relationship of PrfA, we devised a positive-selection system to isolate mutations reducing or abolishing transcriptional activity. The system is based on the observation that the listerialiapgene, encoding the p60 protein, is lethal if overexpressed inBacillus subtilis. A plasmid in which theiapgene is placed under the control of the PrfA-dependenthlypromoter was constructed and introduced intoB. subtilis. This strain was rapidly killed when expression ofiapwas induced by introduction of a second plasmid carryingprfA. Two classes ofB. subtilissurvivor mutants were identified: one carried mutations iniap, and the second carried mutations inprfA. Sequence analysis of the defectiveprfAgenes identified mutations in three regions of the PrfA protein: region A, between amino acids 58 and 67 in the β-roll domain of PrfA; region B, between amino acids 169 and 193, which corresponds to the DNA-binding helix-turn-helix motif; and region C, comprising the 38 C-terminal amino acids of PrfA, which form a leucine zipper-like structure. PrfA proteins with mutations in regions B and C were unable to bind to the PrfA-binding site in the target DNA, while mutations in region A resulted in a protein still binding the target DNA but unable to form a stable complex with RNA polymerase and initiate transcription in vitro.
Molecular Characterization of a Secreted Enzyme with Phospholipase B Activity from
Moraxella bovis
Authors: Farn Jacinta L. , Strugnell Richard A. , Hoyne Peter A. , Michalski Wojtek P. , Tennent Jan M. 
Published: July 2002

ABSTRACT

A candidate for a vaccine against infectious bovine keratoconjunctivitis (IBK) has been cloned and characterized from
Moraxella bovis.
The
plb
gene encodes a protein of 616 amino acids (molecular mass of ∼65.8 kDa) that expresses phospholipase B activity. Amino acid sequence analysis revealed that PLB is a new member of the GDSL (Gly-Asp-Ser-Leu) family of lipolytic enzymes.
Construction and Consequences of Directed Mutations Affecting the Hemin Receptor in Pathogenic
Corynebacterium
Species
Authors: Schmitt Michael P. , Drazek E. Susan 
Published: July 2002

ABSTRACT

Genes encoding an ATP-binding cassette transporter system involved in hemin iron utilization from
Corynebacterium ulcerans
were cloned and characterized. The genes are homologous to a hemin transport system previously identified in
Corynebacterium diphtheriae
. Disruption of the
hmuT
gene, which encodes the putative hemin receptor, resulted in greatly reduced ability of
C. ulcerans
to use hemin or hemoglobin as an iron source. Inactivation of
hmuT
in
C. diphtheriae
by site-specific recombination had no effect on hemin utilization, which suggests that
C. diphtheriae
has an additional system for transporting hemin.
Inhibition of Quorum Sensing by a
Pseudomonas aeruginosa dksA
Homologue
Authors: Branny Pavel , Pearson James P. , Pesci Everett C. , Köhler Thilo , Iglewski Barbara H. , Van Delden Christian 
Published: July 2002

ABSTRACT

The
Pseudomonas aeruginosa las (lasR-lasI
) and
rhl (rhlR-rhlI
) quorum-sensing systems regulate the expression of several virulence factors, including elastase and rhamnolipid.
P. aeruginosa
strain PR1-E4 is a
lasR
deletion mutant that contains a second, undefined mutation which allows production of elastase and rhamnolipid despite a nonfunctional
las
system. We have previously shown that this strain accomplishes this by increasing the expression of the autoinducer synthase gene
rhlI
. In this report, we show that the elastolytic phenotype of mutant PR1-E4 can be complemented with a
P. aeruginosa
homologue of the
Escherichia coli dnaK
mutation suppressor gene
dksA
. When supplied in
trans
on a multicopy plasmid, this gene completely suppressed elastase production by mutant PR1-E4. Cloning and Northern blot analysis revealed that
dksA
was neither mutated nor less transcribed in mutant PR1-E4. When overexpressed,
dksA
also reduced rhamnolipid production by both mutant PR1-E4 and the wild type, PAO1. Using Northern blot analysis and
lacZ
reporter fusions, we show that
dksA
inhibits
rhlI, rhlAB
, and
lasB
transcription. Exogenous
N
-butyryl–
l
-homoserine lactone overcame the reduced expression of
rhlI
and restored
rhlAB
and
lasB
expression, as well as elastase production. Our results suggest that the overproduction of the
P. aeruginosa
DksA homologue inhibits quorum-sensing-dependent virulence factor production by downregulating the transcription of the autoinducer synthase gene
rhlI
.
Yersinia pestis
pFra Shows Biovar-Specific Differences and Recent Common Ancestry with a
Salmonella enterica
Serovar Typhi Plasmid
Authors: Prentice Michael B. , James Keith D. , Parkhill Julian , Baker Stephen G. , Stevens Kim , Simmonds Mark N. , Mungall Karen L. , Churcher Carol , Oyston Petra C. F. , Titball Richard W. , Wren Brendan W. , Wain John , Pickard Derek , Hien Tran Tinh , Farrar Jeremy J. , Dougan Gordon 
Published: July 2002

ABSTRACT

Population genetic studies suggest that
Yersinia pestis
, the cause of plague, is a clonal pathogen that has recently emerged from
Yersinia pseudotuberculosis
. Plasmid acquisition is likely to have been a key element in this evolutionary leap from an enteric to a flea-transmitted systemic pathogen. However, the origin of
Y. pestis
-specific plasmids remains obscure. We demonstrate specific plasmid rearrangements in different
Y. pestis
strains which distinguish
Y. pestis
bv. Orientalis strains from other biovars. We also present evidence for plasmid-associated DNA exchange between
Y. pestis
and the exclusively human pathogen
Salmonella enterica
serovar Typhi.
Phage λ Red-Mediated Adaptive Mutation
Authors: Poteete Anthony R. , Wang Hsinju R. , Foster Patricia L. 
Published: July 2002

ABSTRACT

Replacement of the
recBCD
genes of
Escherichia coli
with the
red
recombination genes of bacteriophage lambda results in a strain in which adaptive mutation occurs at an elevated frequency. Like RecBCD-dependent adaptive mutation, Red-mediated adaptive mutation is dependent upon
recA
and
ruvABC
functions.
Regulation and Adaptive Evolution of Lactose Operon Expression in
Lactobacillus delbrueckii
Authors: Lapierre Luciane , Mollet Beat , Germond Jacques-Edouard 
Published: July 2002

ABSTRACT

Lactobacillus delbrueckii
subsp.
bulgaricus
and
L. delbrueckii
subsp.
lactis
are both used in the dairy industry as homofermentative lactic acid bacteria in the production of fermented milk products. After selective pressure for the fast fermentation of milk in the manufacture of yogurts,
L. delbrueckii
subsp.
bulgaricus
loses its ability to regulate
lac
operon expression. A series of mutations led to the constitutive expression of the
lac
genes. A complex of insertion sequence (IS) elements (ISL
4
inside ISL
5
), inserted at the border of the
lac
promoter, induced the loss of the palindromic structure of one of the operators likely involved in the binding of regulatory factors. A
lac
repressor gene was discovered downstream of the β-galactosidase gene of
L. delbrueckii
subsp.
lactis
and was shown to be inactivated by several mutations in
L. delbrueckii
subsp.
bulgaricus
. Regulatory mechanisms of the
lac
gene expression of
L. delbrueckii
subsp.
bulgaricus
and
L. delbrueckii
subsp.
lactis
were compared by heterologous expression in
Lactococcus lactis
of the two
lac
promoters in front of a reporter gene (β-glucuronidase) in the presence or absence of the
lac
repressor gene. Insertion of the complex of IS elements in the
lac
promoter of
L. delbrueckii
subsp.
bulgaricus
increased the promoter's activity but did not prevent repressor binding; rather, it increased the affinity of the repressor for the promoter. Inactivation of the
lac
repressor by mutations was then necessary to induce the constitutive expression of the
lac
genes in
L. delbrueckii
subsp.
bulgaricus
.
Comparison and Evaluation of Antimicrobial Susceptibility Testing of Enterococci Performed in Accordance with Six National Committee Standardized Disk Diffusion Procedures
Authors: Cotter Gary , Adley Catherine C. 
Published: July 2002

ABSTRACT
Studies were conducted to compare and evaluate antimicrobial susceptibility test results for enterococci obtained by six national committee disk diffusion procedures. Variations in the incidence of isolates in resistance categories and errors were associated with the use of ciprofloxacin, gentamicin, nitrofurantoin, rifampin, and teicoplanin in a number of committee procedures. Results indicate that laboratories performing disk diffusion antimicrobial susceptibility testing may have problems correctly identifying resistance in enterococci with agents used to combat infections and that it may be difficult to compare resistance data for surveillance purposes.
Use of Quantitative PCR To Measure Density of
Borrelia burgdorferi
in the Midgut and Salivary Glands of Feeding Tick Vectors
Authors: Piesman Joseph , Schneider Bradley S. , Zeidner Nordin S. 
Published: July 2002

ABSTRACT
Quantitative real-time PCR was used to assay spirochetes in feeding ticks. Spirochetes in tick midguts increased sixfold, from 998 per tick before attachment to 5,884 at 48 h of attachment. Spirochetes in tick salivary glands increased >17-fold, from 1.2 per salivary gland pair before feeding to 20.8 at 72 h postattachment. The period of the most rapid increase in the number of spirochetes in the salivary glands occurred from 48 to 60 h postattachment; this time period coincides with the maximal increase in transmission risk during nymphal tick feeding.
Novel
Ehrlichia
Genotype Detected in Dogs in South Africa
Authors: Allsopp M. T. E. P. , Allsopp B. A. 
Published: July 2002

ABSTRACT

DNA samples from dogs presenting with symptoms suggestive of canine ehrlichiosis, but with no morulae detected on blood smears, frequently failed to give a positive reaction with a North American
Ehrlichia canis
-specific PCR assay targeting the 16S rRNA gene. We suspected the presence of a pathogen genetically different from North American
E
.
canis
, and we performed experiments to test this hypothesis. DNA from one canine blood sample was subjected to PCR with primers designed to amplify
Ehrlichia
(
Cowdria
)
ruminantium
ruminantium
16S and
map1
genes. Amplicon sequencing yielded 16S and
map1
sequences which were more closely related to other
E
.
ruminantium
sequences than to those of any other
Ehrlichia
species. Fifty canine DNA samples were subjected to a PCR assay, previously found to be
Cowdria
-specific, which targets the pCS20 gene. Thirty-seven (74%) gave a positive signal, and 16 (32%) also gave visible amplicons after gel electrophoresis, suggesting that this
E
.
ruminantium
organism is common in the Pretoria-Johannesburg area. The organism has not been isolated in culture, so we cannot definitively state that it was responsible for the canine ehrlichiosis symptoms, although the occurrence of several similar cases suggests this to be so. Most importantly, we also do not yet know whether the organism is infective for, or causes heartwater in, ruminants.
Immunological and PCR Analyses for Borna Disease Virus in Psychiatric Patients and Blood Donors in Japan
Authors: Fukuda Koji , Takahashi Kazuo , Iwata Yasuhide , Mori Norio , Gonda Kenji , Ogawa Tsuguhiro , Osonoe Kouichi , Sato Minako , Ogata Shin-ichi , Horimoto Taisuke , Sawada Takashi , Tashiro Masato , Yamaguchi Kazunari , Niwa Shin-ichi , Shigeta Shiro 
Published: July 2002

ABSTRACTThe involvement of Borna disease virus (BDV) in psychiatric diseases in humans remains controversial. T-cell memory response and seroprevalence of BDV in patients with psychiatric disorders and blood donors in Japan were evaluated collectively by Western blot (WB) analysis with inhibition test, electrochemiluminescence immunoassay, immunofluorescence assay, and T-cell proliferative response as well as detection of BDV p24 RNA in peripheral blood mononuclear cells (PBMCs). Positive proliferative responses to both BDV p40 and p24 proteins were detected in 9% of patients with mood disorders (4 of 45), 4% of schizophrenic patients (2 of 45), and 2% of blood donors (1 of 45). By WB analysis, the antibody to BDV p40 was detected only in 2% of patients with mood disorders (1 of 45). The BDV p24 antibody was detected in 2% of patients with mood disorders (1 of 45) and 9% of schizophrenic patients. (4 of 45) No plasma reacted with both BDV proteins. The finding of a lower seroprevalence than previously reported suggests the presence of false-positive cases in the previous report. BDV RNA was detected only in 2% of patients with mood disorders (1 of 45). In these three serological assays, T-cell responses, and PCR analysis, there was no significant difference in the prevalence among the three groups. However, we found three psychiatric patients who were positive for both BDV antibodies and T-cell proliferative responses and one patient who was positive for BDV RNA in PBMCs. These findings suggest the usefulness of the proliferative T-cell response and that certain individuals are infected with BDV or a BDV-related virus.
Microsatellite Typing as a New Tool for Identification of
Saccharomyces cerevisiae
Strains
Authors: Hennequin C. , Thierry A. , Richard G. F. , Lecointre G. , Nguyen H. V. , Gaillardin C. , Dujon B. 
Published: July 2002

ABSTRACT

Since
Saccharomyces cerevisiae
appears to be an emerging pathogen, there is a need for a valuable molecular marker able to distinguish among strains. In this work, we investigated the potential value of microsatellite length polymorphism with a panel of 91 isolates, including 41 clinical isolates, 14 laboratory strains, and 28 strains with industrial relevance. Testing seven polymorphic regions (five trinucleotide repeats and two dinucleotide repeats) in a subgroup of 58 unrelated strains identified a total of 69 alleles (6 to 13 per locus) giving 52 different patterns with a discriminatory power of 99.03%. We found a cluster of clinical isolates sharing their genotype with a bakery strain, suggesting a digestive colonization following ingestion of this strain with diet. With the exception of this cluster of isolates and isolates collected from the same patient or from patients treated with
Saccharomyces boulardii
, all clinical isolates gave different and unique patterns. The genotypes are stable, and the method is reproducible. The possibility to make the method portable is of great interest for further studies using this technique. This work shows the possibility to readily identify
S. boulardii
(a strain increasingly isolated from invasive infections) using a unique and specific microsatellite allele.
Paratuberculosis Infection of Nonruminant Wildlife in Scotland
Authors: Beard P. M. , Daniels M. J. , Henderson D. , Pirie A. , Rudge K. , Buxton D. , Rhind S. , Greig A. , Hutchings M. R. , McKendrick I. , Stevenson K. , Sharp J. M. 
Published: July 2002

ABSTRACT

Recent reports of natural paratuberculosis (or Johne's disease) in rabbits, foxes, and stoats has focused debate on the presence and importance of wildlife reservoirs in the epidemiology of this disease. This paper describes an extensive study investigating 18 nonruminant wildlife species for evidence of paratuberculosis. Using both culture and histopathological analysis, fox, stoat, weasel, crow, rook, jackdaw, rat, wood mouse, hare, and badger were found to harbor
Mycobacterium avium
subsp.
paratuberculosis
, the causative organism of paratuberculosis, suggesting that the epidemiology of this disease is more complex than previously realized.
Etiology of Children's Diarrhea in Montevideo, Uruguay: Associated Pathogens and Unusual Isolates
Authors: Torres M. E. , Pı́rez M. C. , Schelotto F. , Varela G. , Parodi V. , Allende F. , Falconi E. , Dell'Acqua L. , Gaione P. , Méndez M. V. , Ferrari A. M. , Montano A. , Zanetta E. , Acuña A. M. , Chiparelli H. , Ingold E. 
Published: July 2002

ABSTRACT

We studied microorganisms associated with infant diarrhea in a group of 256 children admitted to a public pediatric hospital in Montevideo, Uruguay. Diagnostic procedures were updated to optimize detection of potential pathogens, which were found in 63.8% of cases, and to be able to define their characteristics down to molecular or antigenic type. Coinfection with two or more agents was detected in more than one-third of positive studies.
Escherichia coli
enteric virotypes, especially enteropathogenic
E. coli
(EPEC), were shown to be prevalent. Rotavirus,
Cryptosporidium
,
Campylobacter
(mainly
Campylobacter jejuni
), and
Shigella flexneri
were also often identified. Enterotoxigenic
E. coli,
Salmonella,
and
Giardia lamblia
were sporadically recognized. Unusual findings included two enteroinvasive
E. coli
strains, one
Shigella dysenteriae
2 isolate, and a non-O:1
Vibrio cholerae
culture. EPEC bacteria and
S. flexneri
(but not
Salmonella
) showed unusually frequent antimicrobial resistance, especially towards beta-lactam antibiotics, which is the subject of ongoing work.
Occurrence of Vancomycin-Resistant Enterococci in Pork and Poultry Products from a Cattle-Rearing Area of France
Authors: Gambarotto Karine , Ploy Marie-Cecile , Dupron Frederic , Giangiobbe Marie , Denis Francois 
Published: July 2002

ABSTRACT
Meat products were collected from public retail outlets and tested for the presence of vancomycin-resistant enterococci (VRE) in an area with a high prevalence of VRE reported in human fecal samples. VRE were detected in 66% of the samples, and a predominance of VanC strains was found, which is also true for human fecal samples.
Identification of Two Different 14-α Sterol Demethylase-Related Genes (
cyp51A
and
cyp51B
) in
Aspergillus fumigatus
and Other
Aspergillus
species
Authors: Mellado E. , Diaz-Guerra T. M. , Cuenca-Estrella M. , Rodriguez-Tudela J. L. 
Published: July 2002

ABSTRACT

Two
cyp51
-related genes (
cyp51A
and
cyp51B
) encoding 14-α sterol demethylase-like enzymes were identified in the opportunistic human pathogen
Aspergillus fumigatus
. PCR amplification using degenerate oligonucleotides based on conserved areas of cytochrome P450 demethylases of other filamentous fungi and yeasts allowed the cloning and sequencing of two different homologue genes in
A. fumigatus
. Southern analysis confirmed that both genes hybridized to distinct genomic loci and that both are represented as single copies in the genome. Comparison of the deduced Cyp51A and Cyp51B proteins with the CYP51 proteins from
Penicillium italicum, Aspergillus nidulans, Erysiphe graminis, Uncinula necator, Botrytis cinerea, Ustilago maydis, Cryptococcus neoformans, Candida albicans, Saccharomyces cerevisiae, Candida tropicalis
, and
Candida glabrata
showed that the percentages of identity of the amino acid sequences (range, 40 to 70%) were high enough to consider Cyp51A and Cyp51B to be members of the fungal CYP51 family. Fragments from both genes were also cloned from other
Aspergillus
spp. (
A. flavus, A. nidulans
, and
A. terreus
). Phylogenetic analysis showed that, at least in the most pathogenic species of
Aspergillus
, there are two fungal CYP51 proteins. This is the first report of the existence of two homologue genes coding for 14-α sterol demethylase in the fungal kingdom. This finding could provide insights into the azole resistance mechanisms operating in fungi. The primers used here may be useful molecular tools for facilitating the cloning of novel 14-α sterol demethylase genes in other filamentous fungi.