bluuebunny/crossref_metadata_2025_split huggingface dataset:
Alkyl-Lysophospholipid Resistance in Multidrug-Resistant
Leishmania tropica
and Chemosensitization by a Novel P-Glycoprotein-Like Transporter Modulator
Authors: Pérez-Victoria José M. , Pérez-Victoria F. Javier , Parodi-Talice Adriana , Jiménez Ignacio A. , Ravelo Angel G. , Castanys Santiago , Gamarro Francisco 
Published: July 2002

ABSTRACT

Drug resistance has emerged as a major impediment in the treatment of leishmaniasis. Alkyl-lysophospholipids (ALP), originally developed as anticancer drugs, are considered to be the most promising antileishmanial agents. In order to anticipate probable clinical failure in the near future, we have investigated possible mechanisms of resistance to these drugs in
Leishmania
spp. The results presented here support the involvement of a member of the ATP-binding cassette (ABC) superfamily, the
Leishmania
P-glycoprotein-like transporter, in the resistance to ALP. (i) First, a multidrug resistance (MDR)
Leishmania tropica
line overexpressing a P-glycoprotein-like transporter displays significant cross-resistance to the ALP miltefosine and edelfosine, with resistant indices of 9.2- and 7.1-fold, respectively. (ii) Reduced expression of P-glycoprotein in the MDR line correlates with a significant decrease in ALP resistance. (iii) The ALP were able to modulate the P-glycoprotein-mediated resistance to daunomycin in the MDR line. (iv) We have found a new inhibitor of this transporter, the sesquiterpene C-3, that completely sensitizes MDR parasites to ALP. (v) Finally, the MDR line exhibits a lower accumulation than the wild-type line of bodipy-C
5
-PC, a fluorescent analogue of phosphatidylcholine that has a structure resembling that of edelfosine. Also, C-3 significantly increases the accumulation of the fluorescent analogue to levels similar to those of wild-type parasites. The involvement of the
Leishmania
P-glycoprotein-like transporter in resistance to drugs used in the treatment of leishmaniasis also supports the importance of developing new specific inhibitors of this ABC transporter.
Mutator Bacteria as a Risk Factor in Treatment of Infectious Diseases
Authors: Giraud Antoine , Matic Ivan , Radman Miroslav , Fons Michel , Taddei François 
Published: July 2002

ABSTRACT
We show in a gnotobiotic mouse model that, in addition to direct selection of antibiotic-resistant bacteria, some antibiotic treatments also select for mutator alleles. Because of these mutator alleles' high mutation rates, the initial treatment failure increases the probability of failures in subsequent treatments with other drugs.
Crystal Structure of (−)-Mefloquine Hydrochloride Reveals Consistency of Configuration with Biological Activity
Authors: Karle Jean M. , Karle Isabella L. 
Published: July 2002

ABSTRACT

The absolute configuration of (−)-mefloquine has been established as 11
R
,12
S
by X-ray crystallography of the hydrochloride salt, thus allowing comparison of the configuration of mefloquine's optical isomers to those of quinine and quinidine. (−)-Mefloquine has the same stereochemistry as quinine, and (+)-mefloquine has the same stereochemistry as quinidine. Since (+)-mefloquine is more potent than (−)-mefloquine in vitro against the D6 and W2 strains of
Plasmodium falciparum
and quinidine is more potent than quinine, a common stereochemical component for antimalarial activity is implicated. The crystal of (−)-mefloquine hydrochloride contained four different conformations which mainly differ in a small rotation of the piperidine ring. These conformations are essentially the same as the crystalline conformations of racemic mefloquine methylsulfonate monohydrate, mefloquine hydrochloride, and mefloquine free base. The crystallographic parameters for (−)-mefloquine hydrochloride hydrate were as follows: C
17
H
17
F
6
N
2
O
+
Cl
−
· 0.25 H
2
O;

M
r

, 419.3; symmetry of unit cell, orthorhombic; space group,

P2
1
2
1
2
1

; parameters of unit cell,
a
= 12.6890 ± 0.0006 Å (1 Å = 0.1 nm),
b
= 18.9720 ± 0.0009 Å,
c
= 32.189 ± 0.017 Å; volume of unit cell, 7,749 ± 4 Å
3
; number of molecules per unit cell, 16; calculated density, 1.44 g cm
−3
; source of radiation, Cu Kα (λ = 1.54178 Å); μ (absorption coefficient), 2.373 mm
−1
; room temperature was used; final

R
1

(residual index), 0.0874 for 3,692 reflections with intensities greater than 2σ. All of the hydroxyl and amine hydrogen atoms participate in intermolecular hydrogen bonds with chloride ions. The orientation of the amine and hydroxyl groups in (+)-mefloquine may define the optimal geometry for hydrogen bonding with cellular constituents.
Broad-Spectrum Bactericidal Activity of Ag
2
O-Doped Bioactive Glass
Authors: Bellantone Maria , Williams Huw D. , Hench Larry L. 
Published: July 2002

ABSTRACT

Bioactive glass has found extensive application as an orthopedic and dental graft material and most recently also as a tissue engineering scaffold. Here we report an initial investigation of the in vitro antibacterial properties of AgBG, a novel bioactive glass composition doped with Ag
2
O. The bacteriostatic and bactericidal properties of this new material and of two other bioactive glass compositions, 45S5 Bioglass and BG, have been studied by using
Escherichia coli
,
Pseudomonas aeruginosa
, and
Staphylococcus aureus
as test microorganisms. Concentrations of AgBG in the range of 0.05 to 0.20 mg of AgBG per ml of culture medium were found to inhibit the growth of these bacteria. Not only was AgBG bacteriostatic, but it also elicited a rapid bactericidal action. A complete bactericidal effect was elicited within the first hours of incubation at AgBG concentrations of 10 mg ml
−1
. 45S5 Bioglass and BG had no effect on bacterial growth or viability. The antibacterial action of AgBG is attributed exclusively to the leaching of Ag
+
ions from the glass matrix. Analytical measurements rule out any contribution to AgBG-mediated bacterial killing by changes in pH or ionic strength or the dissolution of other ionic species from the biomaterials. Our observations of the dissolution profiles of Ag
+
from AgBG in the presence and absence of bacteria are consistent with silver accumulation by the bacteria.
Seasonal Population Dynamics and Interactions of Competing Bacteriophages and Their Host in the Rhizosphere
Authors: Ashelford Kevin E. , Norris Susan J. , Fry John C. , Bailey Mark J. , Day Martin J. 
Published: July 2002

ABSTRACTWe describe two prolonged bacteriophage blooms within sugar beet rhizospheres ensuing from an artificial increase in numbers of an indigenous soil bacterium. Further, we provide evidence of in situ competition between these phages. This is the first in situ demonstration of such microbial interactions in soil. To achieve this, sugar beet seeds were inoculated withSerratia liquefaciensCP6RS or its lysogen, CP6RS-ly-Φ1. These were sown, along with uninoculated seeds, in 36 field plots arranged in a randomized Latin square. The plots were then sampled regularly over 194 days, and the plants were assayed for the released bacteria and any infectious phages. Both the lysogen and nonlysogen forms of CP6RS survived equally well in situ, contradicting earlier work suggesting lysogens have a competitive disadvantage in nature. APodoviridaephage, identified as ΦCP6-4, flourished on the nonlysogen-inoculated plants in contrast to those plants inoculated with the lysogen. Conversely, theSiphoviridaephage ΦCP6-1 (used to construct the released lysogen) was isolated abundantly from the lysogen-treated plants but almost never on the nonlysogen-inoculated plants. The uninoculated plants also harbored some ΦCP6-1 phage up to day 137, yet hardly any ΦCP6-4 phages were found, and this was consistent with previous years. We show that the different temporal and spatial distributions of these two physiologically distinct phages can be explained by application of optimal foraging theory to phage ecology. This is the first time that such in situ evidence has been provided in support of this theoretical model.
Prevalence of Lyme Disease
Borrelia
spp. in Ticks from Migratory Birds on the Japanese Mainland
Authors: Ishiguro Fubito , Takada Nobuhiro , Masuzawa Toshiyuki , Fukui Takako 
Published: July 2002

ABSTRACT

Borrelia
sp. prevalence in ticks on migratory birds was surveyed in central Japan. In autumn, a total of 1,733 birds representing 40 species were examined for ticks. A total of 361 ticks were obtained from 173 birds of 15 species, and these ticks were immature
Haemaphysalis flava
(94.4%),
Haemaphysalis longicornis
,
Ixodes columnae
,
Ixodes persulcatus
,
Ixodes turdus
, and an unidentified
Ixodes
species. Of these, 27 juveniles of
H. flava
on
Turdus pallidus
,
Turdus cardis
, or
Emberiza spodocephala
, 2 juveniles of
I. persulcatus
on
T. pallidus
, and 1 female
H. flava
molted from a
T. pallidus
-derived nymph were positive for the presence of
Borrelia
by Barbour-Stoenner-Kelly culture passages. In spring, a total of 16 ticks obtained from 102 birds of 21 species were negative for the spirochete. Isolates from 15 ticks were characterized by 5S-23S rRNA intergenic spacer restriction fragment length polymorphism analysis; all isolates were identified as
Borrelia garinii
with pattern B/B′ based on the previous patterning. According to the intergenic spacer sequences, 2 of 15 isolates, strains Fi14f and Fi24f, were highly similar to
B. garinii
strains 935T of Korea and ChY13p of Inner Mongolia, China, respectively. These findings indicate that Lyme disease-causing
B. garinii
may have been introduced to Japan by migratory birds from northeastern China via Korea. Additionally, a case of transstadial transmission of
B. garinii
from nymph to adult
H. flava
suggests that the infected
H. flava
may transmit
Borrelia
to large animals.
Multiplex PCR for Detection and Identification of Lactococcal Bacteriophages
Authors: Labrie Steve , Moineau Sylvain 
Published: July 2002

ABSTRACT

Three genetically distinct groups of
Lactococcus lactis
phages are encountered in dairy plants worldwide, namely, the 936, c2, and P335 species. The multiplex PCR method was adapted to detect, in a single reaction, the presence of these species in whey samples or in phage lysates. Three sets of primers, one for each species, were designed based on conserved regions of their genomes. The c2-specific primers were constructed using the major capsid protein gene (
mcp
) as the target. The
mcp
sequences for three phages (eb1, Q38, and Q44) were determined and compared with the two available in the databases, those for phages c2 and bIL67. An 86.4% identity was found over the five
mcp
genes. The gene of the only major structural protein (
msp
) was selected as a target for the detection of 936-related phages. The
msp
sequences for three phages (p2, Q7, and Q11) were also established and matched with the available data on phages sk1, bIL170, and F4-1. The comparison of the six
msp
genes revealed an 82.2% identity. A high genomic diversity was observed among structural proteins of the P335-like phages suggesting that the classification of lactococcal phages within this species should be revised. Nevertheless, we have identified a common genomic region in 10 P335-like phages isolated from six countries. This region corresponded to
orfF17-orf18
of phage r1t and
orf20-orf21
of Tuc2009 and was sequenced for three additional P335 phages (Q30, P270, and ul40). An identity of 93.4% within a 739-bp region of the five phages was found. The detection limit of the multiplex PCR method in whey was 10
4
to 10
7
PFU/ml and was 10
3
to 10
5
PFU/ml with an additional phage concentration step. The method can also be used to detect phage DNA in whey powders and may also detect prophage or defective phage in the bacterial genome.
Nitrile Hydratase and Amidase from
Rhodococcus rhodochrous
Hydrolyze Acrylic Fibers and Granular Polyacrylonitriles
Authors: Tauber M. M. , Cavaco-Paulo A. , Robra K.-H. , Gübitz G. M. 
Published: July 2002

ABSTRACT

Rhodococcus rhodochrous
NCIMB 11216 produced nitrile hydratase (320 nkat mg of protein
−1
) and amidase activity (38.4 nkat mg of protein
−1
) when grown on a medium containing propionitrile. These enzymes were able to hydrolyze nitrile groups of both granular polyacrylonitriles (PAN) and acrylic fibers. Nitrile groups of PAN40 (molecular mass, 40 kDa) and PAN190 (molecular mass, 190 kDa) were converted into the corresponding carbonic acids to 1.8 and 1.0%, respectively. In contrast, surfacial nitrile groups of acrylic fibers were only converted to the corresponding amides. X-ray photoelectron spectroscopy analysis showed that 16% of the surfacial nitrile groups were hydrolyzed by the
R. rhodochrous
enzymes. Due to the enzymatic modification, the acrylic fibers became more hydrophilic and thus, adsorption of dyes was enhanced. This was indicated by a 15% increase in the staining level (
K/S
value) for C.I. Basic Blue 9.
Molecular and Ecological Evidence for Species Specificity and Coevolution in a Group of Marine Algal-Bacterial Symbioses
Authors: Ashen Jon B. , Goff Lynda J. 
Published: July 2002

ABSTRACT

The phylogenetic relationships of bacterial symbionts from three gall-bearing species in the marine red algal genus
Prionitis
(Rhodophyta) were inferred from 16S rDNA sequence analysis and compared to host phylogeny also inferred from sequence comparisons (nuclear ribosomal internal-transcribed-spacer region). Gall formation has been described previously on two species of
Prionitis
,
P. lanceolata
(from central California) and
P. decipiens
(from Peru). This investigation reports gall formation on a third related host,
Prionitis filiformis
. Phylogenetic analyses based on sequence comparisons place the bacteria as a single lineage within the
Roseobacter
grouping of the α subclass of the division
Proteobacteria
(99.4 to 98.25% sequence identity among phylotypes). Comparison of symbiont and host molecular phylogenies confirms the presence of three gall-bearing algal lineages and is consistent with the hypothesis that these red seaweeds and their bacterial symbionts are coevolving. The species specificity of these associations was investigated in nature by whole-cell hybridization of gall bacteria and in the laboratory by using cross-inoculation trials. Whole-cell in situ hybridization confirmed that a single bacterial symbiont phylotype is present in galls on each host. In laboratory trials, bacterial symbionts were incapable of inducing galls on alternate hosts (including two non-gall-bearing species). Symbiont-host specificity in
Prionitis
gall formation indicates an effective ecological separation between these closely related symbiont phylotypes and provides an example of a biological context in which to consider the organismic significance of 16S rDNA sequence variation.
Characterization of the Minimal Replicon of a Cryptic
Deinococcus radiodurans
SARK Plasmid and Development of Versatile
Escherichia coli-D. radiodurans
Shuttle Vectors
Authors: Meima Rob , Lidstrom Mary E. 
Published: July 2002

ABSTRACT

The nucleotide sequence of a 12-kb fragment of the cryptic
Deinococcus radiodurans
SARK plasmid pUE10 was determined, in order to direct the development of small, versatile cloning systems for
Deinococcus
. Annotation of the sequence revealed 12 possible open reading frames. Among these are the
repU
and
resU
genes, the predicted products of which share similarity with replication proteins and site-specific resolvases, respectively. The products of both genes were demonstrated using an overexpression system in
Escherichia coli
. RepU was found to be required for replication, and ResU was found to be required for stable maintenance of pUE10 derivatives. Gel shift analysis using purified His-tagged RepU identified putative binding sites and suggested that RepU may be involved in both replication initiation and autoregulation of
repU
expression. In addition, a gene encoding a possible antirestriction protein was found, which was shown to be required for high transformation frequencies. The arrangement of the replication region and putative replication genes for this plasmid from
D. radiodurans
strain SARK is similar to that for plasmids found in
Thermus
but not to that for the 45.7-kb plasmid found in
D. radiodurans
strain R1. The minimal region required for autonomous replication in
D. radiodurans
was determined by sequential deletion of segments from the 12-kb fragment. The resulting minimal replicon, which consists of approximately 2.6 kb, was used for the construction of a shuttle vector for
E. coli
and
D. radiodurans
. This vector, pRAD1, is a convenient general-purpose cloning vector. In addition, pRAD1 was used to generate a promoter probe vector, and a plasmid containing
lacZ
and a
Deinococcus
promoter was shown to efficiently express LacZ.
Response of a Soil Bacterial Community to Grassland Succession as Monitored by 16S rRNA Levels of the Predominant Ribotypes
Authors: Felske Andreas , Wolterink Arthur , Van Lis Robert , De Vos Willem M. , Akkermans Antoon D. L. 
Published: July 2002

ABSTRACT

The composition of predominant soil bacteria during grassland succession was investigated in the Dutch Drentse A area. Five meadows, taken out of agricultural production at different time points, and one currently fertilized plot represented different stages of grassland succession. Since fertilization and agricultural production were stopped, the six plots showed a constant decline in the levels of nutrients and vegetation changes. The activity of the predominant bacteria was monitored by direct ribosome isolation from soil and temperature gradient gel electrophoresis of reverse transcription (RT)-PCR products generated from bacterial 16S rRNA. The amounts of 16S rRNA of 20 predominant ribosome types per gram of soil were monitored via multiple competitive RT-PCR in six plots at different succession stages. These ribosome types mainly represented
Bacillus
and members of the
Acidobacterium
cluster and the α subclass of the class
Proteobacteria
. The 20 16S rRNA molecules monitored represented approximately half of all bacterial soil rRNA which was estimated by dot blot hybridizations of soil rRNA with the
Bacteria
probe EUB338. The grasslands showed highly reproducible and specific shifts of bacterial ribosome type composition. The total bacterial ribosome level increased during the first years after agricultural production and fertilization stopped. This correlated with the collapse of the dominant
Lolium perenne
population and an increased rate of mineralization of organic matter. The results indicate that there is a true correlation between the total activity of the bacterial community in soil and the amount of bacterial ribosomes.
Application of Sequence-Specific Labeled 16S rRNA Gene Oligonucleotide Probes for Genetic Profiling of Cyanobacterial Abundance and Diversity by Array Hybridization
Authors: Rudi Knut , Skulberg Olav M. , Skulberg Randi , Jakobsen Kjetill S. 
Published: July 2002

ABSTRACT

DNA sequence information for the small-subunit rRNA gene (16S rDNA) obtained from cyanobacterial cultures was used to investigate the presence of cyanobacteria and their abundance in natural habitats. Eight planktonic communities developing in lakes characterized by relatively low algal biomass (mesotrophic) and in lakes with correspondingly high biomass (eutrophic) were selected for the study. The organismal compositions of the water samples were analyzed genetically, using multiplex sequence-specific labeling of oligonucleotide probes targeted to 16S rDNA and subsequent hybridization of the labeled probes to their respective complements spotted onto a solid support (DNA array). Ten probes were established to determine the relative abundances of the discernible cyanobacteria encountered in the selected lakes. The probes were generally specific for their targets, as determined through analyses of clone cultures. Reproducible abundance profiles were established for the lakes investigated in the subsequent analyses of natural cyanobacterial communities. The results from the genetic analyses were then compared with information obtained from standard hydrobiological and hydrochemical analyses. Qualitatively, there were relatively good correlations among the groups of organisms (
Nostoc
,
Microcystis
, and
Planktothrix
species) found in the different lakes. The levels of correlation were lower for the quantitative data. This may, however, be due to differences in sample processing technique. The conclusions from these comparisons are that the genetic abundance profiles may provide a foundation for separating and quantifying genetically distinct groups of cyanobacteria in their natural habitats.
Role for Outer Membrane Cytochromes OmcA and OmcB of
Shewanella putrefaciens
MR-1 in Reduction of Manganese Dioxide
Authors: Myers Judith M. , Myers Charles R. 
Published: July 2002

ABSTRACT

Shewanella putrefaciens
MR-1 can use a wide variety of terminal electron acceptors for anaerobic respiration, including certain insoluble manganese and iron oxides. To examine whether the outer membrane (OM) cytochromes of MR-1 play a role in Mn(IV) and Fe(III) reduction, mutants lacking the OM cytochrome OmcA or OmcB were isolated by gene replacement. Southern blotting and PCR confirmed replacement of the
omcA
and
omcB
genes, respectively, and reverse transcription-PCR analysis demonstrated loss of the respective mRNAs, whereas mRNAs for upstream and downstream genes were retained. The
omcA
mutant (OMCA1) resembled MR-1 in its growth on trimethylamine
N
-oxide (TMAO), dimethyl sulfoxide, nitrate, fumarate, thiosulfate, and tetrathionate and its reduction of nitrate, nitrite, ferric citrate, FeOOH, and anthraquinone-2,6-disulfonic acid. Similarly, the
omcB
mutant (OMCB1) grew on fumarate, nitrate, TMAO, and thiosulfate and reduced ferric citrate and FeOOH. However, OMCA1 and OMCB1 were 45 and 75% slower than MR-1, respectively, at reducing MnO
2
. OMCA1 lacked only OmcA. While OMCB1 lacked OmcB, other OM cytochromes were also missing or markedly depressed. The total cytochrome content of the OM of OMCB1 was less than 15% of that of MR-1. Western blots demonstrated that OMCB1 still synthesized OmcA, but most of it was localized in the cytoplasmic membrane and soluble fractions rather than in the OM. OMCB1 had therefore lost the ability to properly localize multiple OM cytochromes to the OM. Together, the results suggest that the OM cytochromes of MR-1 participate in the reduction of Mn(IV) but are not required for the reduction of Fe(III) or other electron acceptors.