bluuebunny/crossref_metadata_2025_split huggingface dataset:
OXA-28, an Extended-Spectrum Variant of OXA-10 β-Lactamase fromPseudomonas aeruginosaand Its Plasmid- and Integron-Located Gene
Authors: Poirel Laurent , Girlich Delphine , Naas Thierry , Nordmann Patrice 
Published: July 2002

ABSTRACTPseudomonas aeruginosaED-1, isolated from a pulmonary brush of a patient hospitalized in a suburb of Paris, France, was resistant to ceftazidime and of intermediate susceptibility to ureidopenicillins and to cefotaxime. Cloning and expression of the β-lactamase gene content of this isolate inEscherichia coliDH10B identified a novel OXA-10 variant, OXA-28, with a pI value of 8.1 and a molecular mass of 29 kDa. It differed from OXA-10 by 10 amino acid changes and from OXA-13 and OXA-19 by 2 amino acid changes, including a glycine instead of tryptophan at position 164, which is likely involved in its resistance to ceftazidime. Like OXA-11, -14, -16, and -19 and as opposed to OXA-17, OXA-28 predominantly compromised ceftazidime and had only marginal effect on the MICs of aztreonam and cefotaxime inP. aeruginosa. Once expressed inE. coli, OXA-28 raised the MIC of ceftazidime to a much higher level than those of amoxicillin, cephalothin, and cefotaxime (128, 16, 8, and 4 μg/ml, respectively). OXA-28 β-lactamase had a broad spectrum of activity, including ceftazidime. Its activity was partially antagonized by clavulanic acid (50% inhibitory concentration, 10 μM) and NaCl addition. Theoxa28gene cassette was inserted in the variable region of a class 1 integron, In57, immediately downstream of an amino 6′-N-acetyltransferase gene cassette,aac(6′)Ib. The structures of the integrons carrying eitheroxa28,oxa13, oroxa19gene cassettes were almost identical, suggesting that they may have derived from a common ancestor as a result of the common European origin of theP. aeruginosaisolates. In57 was located on a self-transferable plasmid of ca. 150 kb that was transferred fromP. aeruginosatoP. aeruginosa.
An ATP-Binding Cassette Transporter and Two rRNA Methyltransferases Are Involved in Resistance to Avilamycin in the Producer Organism
Streptomyces viridochromogenes
Tü57
Authors: Weitnauer Gabriele , Gaisser Sibylle , Trefzer Axel , Stockert Sigrid , Westrich Lucy , Quiros Luis M. , Mendez Carmen , Salas Jose A. , Bechthold Andreas 
Published: July 2002

ABSTRACT

Three different resistance factors from the avilamycin biosynthetic gene cluster of
Streptomyces viridochromogenes
Tü57, which confer avilamycin resistance when expressed in
Streptomyces lividans
TK66, were isolated. Analysis of the deduced amino acid sequences showed that AviABC1 is similar to a large family of ATP-binding transporter proteins and that AviABC2 resembles hydrophobic transmembrane proteins known to act jointly with the ATP-binding proteins. The deduced amino acid sequence of
aviRb
showed similarity to those of other rRNA methyltransferases, and AviRa did not resemble any protein in the databases. Independent expression in
S. lividans
TK66 of
aviABC1
plus
aviABC2, aviRa
, or
aviRb
conferred different levels of resistance to avilamycin: 5, 10, or 250 μg/ml, respectively. When either
aviRa
plus
aviRb
or
aviRa
plus
aviRb
plus
aviABC1
plus
aviABC2
was coexpressed in
S. lividans
TK66, avilamycin resistance levels reached more than 250 μg/ml. Avilamycin A inhibited poly(U)-directed polyphenylalanine synthesis in an in vitro system using ribosomes of
S. lividans
TK66(pUWL201) (GWO),
S. lividans
TK66(pUWL201-Ra) (GWRa), or
S. lividans
TK66(pUWL201-Rb) (GWRb), whereas ribosomes of
S. lividans
TK66 containing pUWL201-Ra+Rb (GWRaRb) were highly resistant.
aviRa
and
aviRb
were expressed in
Escherichia coli
, and both enzymes were purified as fusion proteins to near homogeneity. Both enzymes showed rRNA methyltransferase activity using a mixture of 16S and 23S rRNAs from
E. coli
as the substrate. Coincubation experiments revealed that the enzymes methylate different positions of rRNA.
Screening System for Xenosiderophores as Potential Drug Delivery Agents in Mycobacteria
Authors: Schumann Gisbert , Möllmann Ute 
Published: July 2002

ABSTRACT

In order to establish a screening system for xenosiderophores which can be utilized by mycobacteria, we generated a set of mutants of
Mycobacterium smegmatis
that are blocked in different steps of the well-known iron acquisition system. One mutant with a block in mycobactin biosynthesis was generated from strain mc
2
155 by chemical mutagenesis. The exochelin biosynthesis gene
fxbA
and the ferric exochelin uptake gene
fxuA
, previously identified by Fiss et al. (E. H. Fiss, S. Yu, and W. R. Jacobs, Jr., Mol. Microbiol. 14:557–559, 1994), were knocked out by gene replacement. Adjacent chromosomal fragments were used for homologous recombination in order to replace wild-type genes by the kanamycin resistance gene from transposon Tn
903
. Gene replacement was confirmed by PCR. The isolated mutants show the expected phenotype:
fxbA
mutants are defective in exochelin biosynthesis, whereas
fxuA
mutants excrete a significantly larger amount of exochelin compared to the amount excreted by the parent strain. This is due to their defectiveness in ferriexochelin uptake, as demonstrated in growth promotion assays. This new set of mutants allows differentiation of siderophores that supply mycobacteria with iron by ligand exchange with exochelin or mycobactin, by the use of separate siderophore uptake routes, or by the use of the exochelin permease. All these types of iron uptake routes were identified with 25 exogenous siderophores as test substances. Siderophores that act without ligand exchange are potential candidates as drug vectors that can be used to overcome permeability-mediated resistance.
Inducible Macrolide Resistance in
Corynebacterium jeikeium
Authors: Rosato Adriana E. , Lee Bonnie S. , Nash Kevin A. 
Published: July 2002

ABSTRACT

Corynebacterium jeikeium
is an opportunistic pathogen primarily of immunocompromised (neutropenic) patients. Broad-spectrum resistance to antimicrobial agents is a common feature of
C. jeikeium
clinical isolates. We studied the profiles of susceptibility of 20 clinical strains of
C. jeikeium
to a range of antimicrobial agents. The strains were separated into two groups depending on the susceptibility to erythromycin (ERY), with one group (17 strains) representing resistant organisms (MIC > 128 μg/ml) and the second group (3 strains) representing susceptible organisms (MIC ≤ 0.25 μg/ml). The ERY resistance crossed to other members of the macrolide-lincosamide-streptogramin B (MLSb) group. Furthermore, this resistance was inducible with MLSb agents but not non-MLSb agents. Expression of ERY resistance was linked to the presence of an allele of the class X
erm
genes,
erm
(X)cj, with >93% identity to other
erm
genes of this class. Our evidence indicates that
erm
(X)cj is integrated within the chromosome, which contrasts with previous reports for the plasmid-associated
erm
(X) genes found in
C. diphtheriae
and
C. xerosis
. In 40% of
C. jeikeium
strains,
erm
(X)cj is present within the transposon, Tn
5432
. However, in the remaining strains, the components of Tn
5432
(i.e., the
erm
and transposase genes) have separated within the chromosome. The rearrangement of Tn
5432
leads to the possibility that the other drug resistance genes have become included in a new composite transposon bound by the IS
1249
elements.
Immunoprecipitation of [
3
H]Dihydroartemisinin Translationally Controlled Tumor Protein (TCTP) Adducts from
Plasmodium falciparum
-Infected Erythrocytes by Using Anti-TCTP Antibodies
Authors: Bhisutthibhan Jamaree , Meshnick Steven R. 
Published: July 2002

ABSTRACT

Artemisinin and its derivatives are endoperoxide-containing antimalarial drugs that appear to form adducts in situ with the
Plasmodium falciparum
translationally controlled tumor protein (TCTP) homolog. Immunoprecipitation with antibody to recombinant TCTP suggests that adducts may form with both monomeric and dimeric TCTP.
New Class of Small Nonpeptidyl Compounds Blocks
Plasmodium falciparum
Development In Vitro by Inhibiting Plasmepsins
Authors: Jiang Suping , Prigge Sean T. , Wei Lan , Gao Yu-e , Hudson Thomas H. , Gerena Lucia , Dame John B. , Kyle Dennis E. 
Published: July 2002

ABSTRACT

Malarial parasites rely on aspartic proteases called plasmepsins to digest hemoglobin during the intraerythrocytic stage. Plasmepsins from
Plasmodium falciparum
and
Plasmodium vivax
have been cloned and expressed for a variety of structural and enzymatic studies. Recombinant plasmepsins possess kinetic similarity to the native enzymes, indicating their suitability for target-based antimalarial drug development. We developed an automated assay of
P. falciparum
plasmepsin II and
P. vivax
plasmepsin to quickly screen compounds in the Walter Reed chemical database. A low-molecular-mass (346 Da) diphenylurea derivative (WR268961) was found to inhibit plasmepsins with a
K

i

of 1 to 6 μM. This compound appears to be selective for plasmepsin, since it is a poor inhibitor of the human aspartic protease cathepsin D (
K

i

greater than 280 μM). WR268961 inhibited the growth of
P. falciparum
strains W2 and D6, with 50% inhibitory concentrations ranging from 0.03 to 0.16 μg/ml, but was much less toxic to mammalian cells. The Walter Reed chemical database contains over 1,500 compounds with a diphenylurea core structure, 9 of which inhibit the plasmepsins, with
K

i

values ranging from 0.05 to 0.68 μM. These nine compounds show specificity for the plasmepsins over human cathepsin D, but they are poor inhibitors of
P. falciparum
growth in vitro. Computational docking experiments indicate how diphenylurea compounds bind to the plasmepsin active site and inhibit the enzyme.
Countrywide Spread of CTX-M-3 Extended-Spectrum β-Lactamase-Producing Microorganisms of the Family
Enterobacteriaceae
in Poland
Authors: Baraniak Anna , Fiett Janusz , Sulikowska Agnieszka , Hryniewicz Waleria , Gniadkowski Marek 
Published: July 2002

ABSTRACT

Eighty-four clinical isolates of the family
Enterobacteriaceae
, recovered from 1998 to 2000 in 15 hospitals in 10 Polish cities, were analyzed. All the isolates produced β-lactamases with pIs of 8.4 and 5.4, and the pI 8.4 enzymes were demonstrated to hydrolyze cefotaxime but not ceftazidime in the in vitro bioassay. PCR analysis and DNA sequencing have revealed that in all cases the pI 8.4 β-lactamase was probably the CTX-M-3 extended-spectrum β-lactamase (ESBL) variant, which was originally identified in 1996 in Praski Hospital in Warsaw. In the majority of isolates,
bla
CTX-M-3
genes resided within large conjugative plasmids with similar fingerprints, which, in the context of the high degree of diversity of the randomly amplified polymorphic DNA types of the isolates, suggested that horizontal transfer of plasmids was likely the main mechanism of CTX-M-3 spread. The dissemination of plasmids was probably preceded by the center-to-center transmission of several strains, as indicated by the identification by pulsed-field gel electrophoresis of closely related or possibly related
Klebsiella pneumoniae
,
Escherichia coli
, and
Citrobacter freundii
isolates in five different hospitals. CTX-M-3-producing organisms revealed a very high degree of diversity in β-lactam resistance levels and patterns. This was attributed to several factors, such as the production of other β-lactamases including additional ESBLs, possible quantitative variations in CTX-M-3 expression, segregation of AmpC derepressed mutants, and permeability alterations.
bla
VIM-2
Cassette-Containing Novel Integrons in Metallo-β-Lactamase-Producing
Pseudomonas aeruginosa
and
Pseudomonas putida
Isolates Disseminated in a Korean Hospital
Authors: Lee Kyungwon , Lim Jong Back , Yum Jong Hwa , Yong Dongeun , Chong Yunsop , Kim June Myung , Livermore David M. 
Published: July 2002

ABSTRACT

We investigated the phenotypic and genetic properties of metallo-β-lactamase-producing
Pseudomonas
isolates collected at a tertiary-care hospital in Korea since 1995. The prevalence of imipenem resistance among
Pseudomonas aeruginosa
isolates reached 16% in 1997, when 9% of the resistant organisms were found to produce VIM-2 β-lactamase, a class B enzyme previously found only in
P. aeruginosa
isolates from Europe. VIM-2-producing isolates of
Pseudomonas putida
were also detected. Resistance was transferable from both these species to
P. aeruginosa
PAO4089Rp by filter mating, although the resistance determinant could not be found on any detectable plasmid. Serotyping showed that many of the VIM-2-producing
P. aeruginosa
isolates belonged to serotypes O:11 and O:12, and pulsed-field gel electrophoresis of
Xba
I-digested genomic DNA revealed that many had identical profiles, whereas the
P. putida
isolates were diverse. Sequencing showed that the
bla
VIM-2
genes resided as cassettes in class 1 integrons. In contrast to previous VIM-encoding integrons, the integron sequenced from a
P. aeruginosa
isolate had
bla
VIM
located downstream of a variant of
aacA4. bla
VIM
also lay in a class 1 integron in a representative
P. putida
strain, but the organization of this integron was different from that sequenced from the
P. aeruginosa
strain. In conclusion, the metallo-β-lactamase produced by these imipenem-resistant
Pseudomonas
isolates was VIM-2, and the accumulation of producers reflected clonal dissemination as well as horizontal spread. Strict measures are required in order to control a further spread of resistance.
Design and Antileishmanial Activity of Amphotericin B-Loaded Stable Ionic Amphiphile Biovector Formulations
Authors: Loiseau P. M. , Imbertie L. , Bories C. , Betbeder D. , De Miguel I. 
Published: July 2002

ABSTRACT

A new delivery system, Ionic Amphiphilic Biovector (ABV), comprised of anionic lipids (dipalmitoyl phosphatidyl glycerol) included in a cationic cross-linked polysaccharide matrix was used as a reservoir for amphotericin B (AmB). Two ABV formulations exhibited an in vitro and in vivo efficacy similar to commercial AmBisome against
Leishmania donovani
-infected mice. The higher stability of these ABV formulations indicates their potential for further development and applications.
Urea Hydrogen Peroxide Reduces the Numbers of Lactobacilli, Nourishes Yeast, and Leaves No Residues in the Ethanol Fermentation
Authors: Narendranath N. V. , Thomas K. C. , Ingledew W. M. 
Published: July 2002

ABSTRACT

Urea hydrogen peroxide (UHP) at a concentration of 30 to 32 mmol/liter reduced the numbers of five
Lactobacillus
spp. (
Lactobacillus plantarum
,
L. paracasei
,
Lactobacillus
sp. strain 3,
L. rhamnosus
, and
L. fermentum
) from ∼10
7
to ∼10
2
CFU/ml in a 2-h preincubation at 30°C of normal-gravity wheat mash at ∼21 g of dissolved solids per ml containing normal levels of suspended grain particles. Fermentation was completed 36 h after inoculation of
Saccharomyces cerevisiae
in the presence of UHP, even when wheat mash was deliberately contaminated (infected) with
L. paracasei
at ∼10
7
CFU/ml. There were no significant differences in the maximum ethanol produced between treatments when urea hydrogen peroxide was used to kill the bacteria and controls (in which no bacteria were added). However, the presence of
L. paracasei
at ∼10
7
CFU/ml without added agent resulted in a 5.84% reduction in the maximum ethanol produced compared to the control. The bactericidal activity of UHP is greatly affected by the presence of particulate matter. In fact, only 2 mmol of urea hydrogen peroxide per liter was required for disinfection when mashes had little or no particulate matter present. No significant differences were observed in the decomposition of hydrogen peroxide in normal-gravity wheat mash at 30°C whether the bactericidal agent was added as H
2
O
2
or as urea hydrogen peroxide. NADH peroxidase activity (involved in degrading H
2
O
2
) increased significantly (
P
= 0.05) in the presence of 0.75 mM hydrogen peroxide (sublethal level) in all five strains of lactobacilli tested but did not persist in cells regrown in the absence of H
2
O
2
. H
2
O
2
-resistant mutants were not expected or found when lethal levels of H
2
O
2
or UHP were used. Contaminating lactobacilli can be effectively managed by UHP, a compound which when used at ca. 30 mmol/liter happens to provide near-optimum levels of assimilable nitrogen and oxygen that aid in vigorous fermentation performance by yeast.
A Rhamnolipid Biosurfactant Reduces Cadmium Toxicity during Naphthalene Biodegradation
Authors: Sandrin Todd R. , Chech Andrea M. , Maier Raina M. 
Published: July 2002

ABSTRACT

A model cocontaminated system was developed to determine whether a metal-complexing biosurfactant, rhamnolipid, could reduce metal toxicity to allow enhanced organic biodegradation by a
Burkholderia
sp. isolated from soil. Rhamnolipid eliminated cadmium toxicity when added at a 10-fold greater concentration than cadmium (890 μM), reduced toxicity when added at an equimolar concentration (89 μM), and had no effect at a 10-fold smaller concentration (8.9 μM). The mechanism by which rhamnolipid reduces metal toxicity may involve a combination of rhamnolipid complexation of cadmium and rhamnolipid interaction with the cell surface to alter cadmium uptake.
Ingested Blood Contributes to the Specificity of the Symbiosis ofAeromonas veroniiBiovar Sobria andHirudo medicinalis, the Medicinal Leech
Authors: Indergand Stefan , Graf Joerg 
Published: July 2002

ABSTRACTHirudo medicinalis, the medicinal leech, usually carries in its digestive tract a pure culture ofAeromonas veroniibv. sobria. Such specificity is unusual for digestive tracts that are normally colonized by a complex microbial consortium. Important questions for the symbiotic interaction and for the medical application after microvascular surgery are whether other bacteria can proliferate or at least persist in the digestive tract ofH. medicinalisand what factors contribute to the reported specificity. Using a colonization assay, we were able to compare experimentally the ability of clinical isolates and of a symbiotic strain to colonizeH. medicinalis. The symbioticA. veroniibv. sobria strain proliferated well and persisted for at least 7 days inside the digestive tract. In contrast, the proliferation ofPseudomonas aeruginosaandStaphylococcus aureuswas inhibited inside the animal compared to growth in the in vitro control, indicating that the ingested blood was modified within the digestive tract. However, both strains were able to persist in the digestive tract for at least 7 days. For anEscherichia colistrain, the viable counts decreased approximately 1,000-fold within 42 h. The decrease of viableE. colicould be prevented by interfering with the activation of the membrane-attack complex of the complement system that is present in blood. This suggests that the membrane-attack complex remained active insideH. medicinalisand prevented the proliferation of sensitive bacteria. Thus, antimicrobial properties of the ingested vertebrate blood contribute to the specificity of theA. veronii-H. medicinalissymbiosis, in addition to modifications of the blood inside the digestive tract ofH. medicinalis.
Introduction of an N-Glycosylation Site Increases Secretion of Heterologous Proteins in Yeasts
Authors: Sagt C. M. J. , Kleizen B. , Verwaal R. , de Jong M. D. M. , Müller W. H. , Smits A. , Visser C. , Boonstra J. , Verkleij A. J. , Verrips C. T. 
Published: July 2002

ABSTRACT

Saccharomyces cerevisiae
is often used to produce heterologous proteins that are preferentially secreted to increase economic feasibility. We used N-glycosylation as a tool to enhance protein secretion. Secretion of cutinase, a lipase, and llama V
HH
antibody fragments by
S. cerevisiae
or
Pichia pastoris
improved following the introduction of an N-glycosylation site. When we introduced an N-glycosylation consensus sequence in the N-terminal region of a hydrophobic cutinase, secretion increased fivefold. If an N-glycosylation site was introduced in the C-terminal region, however, secretion increased only 1.8-fold. These results indicate that the use of N glycosylation can significantly enhance heterologous protein secretion.
Sequence Diversity of
rulA
among Natural Isolates of
Pseudomonas syringae
and Effect on Function of
rulAB
-Mediated UV Radiation Tolerance
Authors: Sundin George W. , Jacobs Janette L. , Murillo Jesús 
Published: July 2002

ABSTRACT

The
rulAB
locus confers tolerance to UV radiation and is borne on plasmids of the pPT23A family in
Pseudomonas syringae.
We sequenced 14
rulA
alleles from
P. syringae
strains representing seven pathovars and found sequence differences of 1 to 12% within pathovar syringae, and up to 15% differences between pathovars. Since the sequence variation within
rulA
was similar to that of
P. syringae
chromosomal alleles, we hypothesized that
rulAB
has evolved over a long time period in
P. syringae.
A phylogenetic analysis of the deduced amino acid sequences of
rulA
resulted in seven clusters. Strains from the same plant host grouped together in three cases; however, strains from different pathovars grouped together in two cases. In particular, the
rulA
alleles from
P. syringae
pv. lachrymans and
P. syringae
pv. pisi were grouped but were clearly distinct from the other sequenced alleles, suggesting the possibility of a recent interpathovar transfer. We constructed chimeric
rulAB
expression clones and found that the observed sequence differences resulted in significant differences in UV (wavelength) radiation sensitivity. Our results suggest that specific amino acid changes in RulA could alter UV radiation tolerance and the competitiveness of the
P. syringae
host in the phyllosphere.
Application of a Propionyl Coenzyme A Synthetase for Poly(3-Hydroxypropionate-
co
-3-Hydroxybutyrate) Accumulation in Recombinant
Escherichia coli
Authors: Valentin Henry E. , Mitsky Timothy A. , Mahadeo Debbie A. , Tran Minhtien , Gruys Kenneth J. 
Published: July 2002

ABSTRACT

The genetic operon for propionic acid degradation in
Salmonella enterica
serovar Typhimurium contains an open reading frame designated
prpE
which encodes a propionyl coenzyme A (propionyl-CoA) synthetase (A. R. Horswill and J. C. Escalante-Semerena, Microbiology 145:1381–1388, 1999). In this paper we report the cloning of
prpE
by PCR, its overexpression in
Escherichia coli
, and the substrate specificity of the enzyme. When propionate was utilized as the substrate for PrpE, a

K
m

of 50 μM and a specific activity of 120 μmol · min
−1
· mg
−1
were found at the saturating substrate concentration. PrpE also activated acetate, 3-hydroxypropionate (3HP), and butyrate to their corresponding coenzyme A esters but did so much less efficiently than propionate. When
prpE
was coexpressed with the polyhydroxyalkanoate (PHA) biosynthetic genes from
Ralstonia eutropha
in recombinant
E. coli
, a PHA copolymer containing 3HP units accumulated when 3HP was supplied with the growth medium. To compare the utility of acyl-CoA synthetases to that of an acyl-CoA transferase for PHA production, PHA-producing recombinant strains were constructed to coexpress the PHA biosynthetic genes with
prpE
, with
acoE
(an acetyl-CoA synthetase gene from
R. eutropha
[H. Priefert and A. Steinbüchel, J. Bacteriol. 174:6590–6599, 1992]), or with
orfZ
(an acetyl-CoA:4-hydroxybutyrate-CoA transferase gene from
Clostridium propionicum
[H. E. Valentin, S. Reiser, and K. J. Gruys, Biotechnol. Bioeng. 67:291–299, 2000]). Of the three enzymes, PrpE and OrfZ enabled similar levels of 3HP incorporation into PHA, whereas AcoE was significantly less effective in this capacity.