bluuebunny/crossref_metadata_2025_split huggingface dataset:
Iron-Chelating Activity of Tetracyclines and Its Impact on the Susceptibility of
Actinobacillus actinomycetemcomitans
to These Antibiotics
Authors: Grenier Daniel , Huot Marie-Pierre , Mayrand Denis 
Published: July 2002

ABSTRACT

Three tetracyclines (tetracycline, doxycycline, and minocycline) were found to possess iron-chelating activity in a colorimetric siderophore assay. Determination of MICs indicated that the activity of doxycycline against the periodontopathogen
Actinobacillus actinomycetemcomitans
was only slightly influenced by the presence of an excess of iron that likely saturates the antibiotic. On the other hand, the MICs of doxycycline and minocycline were significantly lower for
A. actinomycetemcomitans
cultivated under iron-poor conditions than under iron-rich conditions.
Pharmacokinetics of a Fluoronaphthyridone, Trovafloxacin (CP 99,219), in Infants and Children following Administration of a Single Intravenous Dose of Alatrofloxacin
Authors: Bradley John S. , Kearns Gregory L. , Reed Michael D. , Capparelli Edmund V. , Vincent John ,   The Pediatric Pharmacology Research Unit Network
Published: July 2002

ABSTRACT
The pharmacokinetics of trovafloxacin following administration of a single intravenous dose of alatrofloxacin, equivalent to 4 mg of trovafloxacin per kg of body weight, were determined in 6 infants (ages 3 to 12 months) and 14 children (ages, 2 to 12 years). There was rapid conversion of alatrofloxacin to trovafloxacin, with an average ± standard deviation (SD) peak trovafloxacin concentration determined at the end of the infusion of 4.3 ± 1.4 μg/ml. The primary pharmacokinetic parameters (average ± SD) analyzed were volume of distribution at steady state (1.6 ± 0.6 liters/kg), clearance (151 ± 82 ml/h/kg), and half-life (9.8 ± 2.9 h). The drug was well tolerated by all children. There were no age-related differences in any of the pharmacokinetic parameters studied. Less than 5% of the administered dose was excreted in the urine over 24 h. On the basis of the mean area under the concentration-time curve of 30.5 ± 10.1 μg · h/ml and the susceptibility (≤0.5 μg/ml) of common pediatric bacterial pathogens to trovafloxacin, dosing of 4 mg/kg/day once or twice daily should be appropriate.
Novel β-Lactamase Genes from Two Environmental Isolates of
Vibrio harveyi
Authors: Teo Jeanette W. P. , Suwanto Antonius , Poh Chit Laa 
Published: July 2002

ABSTRACT

Two ampicillin-resistant (Amp
r
) isolates of
Vibrio harveyi
, W3B and HB3, were obtained from the coastal waters of the Indonesian island of Java. Strain W3B was isolated from marine water near a shrimp farm in North Java while HB3 was from pristine seawater in South Java. In this study, novel β-lactamase genes from W3B (
bla
VHW-1
) and HB3 (
bla
VHH-1
) were cloned and their nucleotide sequences were determined. An open reading frame (ORF) of 870 bp encoding a deduced protein of 290 amino acids (VHW-1) was revealed for the
bla
gene of strain W3B while an ORF of 849 bp encoding a 283-amino-acid protein (VHH-1) was deduced for
bla
VHH-1
. At the DNA level, genes for VHW-1 and VHH-1 have a 97% homology, while at the protein level they have a 91% homology of amino acid sequences. Neither gene sequence showed homology to any other β-lactamases in the databases. The deduced proteins were found to be class A β-lactamases bearing low levels of homology (<50%) to other β-lactamases of the same class. The highest level of identity was obtained with β-lactamases from
Pseudomonas aeruginosa
, i.e., PSE-1, PSE-4, and CARB-3, and
Vibrio cholerae
CARB-6. Our study showed that both strains W3B and HB3 possess an endogenous plasmid of approximately 60 kb in size. However, Southern hybridization analysis employing
bla
VHW-1
as a gene probe demonstrated that the
bla
gene was not located in the plasmid. A total of nine ampicillin-resistant
V. harveyi
strains, including W3B and HB3, were examined by pulsed-field gel electrophoresis of
Not
I-digested genomic DNA. Despite a high level of intrastrain genetic diversity, the
bla
VHW-1
probe hybridized only to an 80- or 160-kb
Not
I genomic fragment in different isolates.
Sublethal Concentrations of Pleurocidin-Derived Antimicrobial Peptides Inhibit Macromolecular Synthesis in
Escherichia coli
Authors: Patrzykat Aleksander , Friedrich Carol L. , Zhang Lijuan , Mendoza Valentina , Hancock Robert E. W. 
Published: July 2002

ABSTRACT

Cationic bactericidal peptides are components of natural host defenses against infections. While the mode of antibacterial action of cationic peptides remains controversial, several targets, including the cytoplasmic membrane and macromolecular synthesis, have been identified for peptides acting at high concentrations. The present study identified peptide effects at lower, near-lethal inhibitory concentrations. An amidated hybrid of the flounder pleurocidin and the frog dermaseptin (P-Der), two other pleurocidin derivatives, and pleurocidin itself were studied. At 2 μg/ml, the MIC, P-Der inhibited
Escherichia coli
growth in a broth dilution assay but did not cause bacterial death within 30 min, as estimated by viable count analysis. Consistent with this, P-Der demonstrated a weak ability to permeabilize membranes but was able to translocate across the lipid bilayer of unilamellar liposomes. Doses of 20 μg/ml or more reduced bacterial viable counts by about 2 log orders of magnitude within 5 min after peptide treatment. Abrupt loss of cell membrane potential, observed with a fluorescent dye, dipropylthiacarbocyanine, paralleled bacterial death but did not occur at the sublethal, inhibitory concentrations. Both lethal and sublethal concentrations of P-Der affected macromolecular synthesis within 5 min, as demonstrated by incorporation of [
3
H]thymidine, [
3
H]uridine, and [
3
H]histidine, but the effects were qualitatively distinct at the two concentrations. Variations of the inhibition pattern described above were observed for pleurocidin and two other derivatives. Our results indicate that peptides at their lowest inhibitory concentrations may be less capable of damaging cell membranes, while they maintain their ability to inhibit macromolecular synthesis. Better understanding of the effects of peptides acting at their MICs will contribute to the design of new peptides effective at lower, less toxic concentrations.
Control of Expression of Divergent
Pseudomonas putida put
Promoters for Proline Catabolism
Authors: Vı́lchez Susana , Manzanera Maximino , Ramos Juan L. 
Published: July 2002

ABSTRACT

Pseudomonas putida
KT2440 uses proline as the sole C and N source. Utilization of this amino acid involves its uptake, which is mediated by the PutP protein, and its conversion into glutamate, mediated by the PutA protein. Sequence analysis revealed that the
putA
and
putP
genes are transcribed divergently. Expression from the
putP
and
putA
genes was analyzed at the mRNA level in different host backgrounds in the absence and presence of proline. Expression from the
put
promoters was induced by proline. The transcription initiation points of the
putP
and
putA
genes were precisely mapped via primer extension, and sequence analysis of the upstream DNA region showed well-separated promoters for these two genes. The PutA protein acts as a repressor of
put
gene expression in
P. putida
because expression from the
put
promoters is constitutive in a host background with a knockout
putA
gene. This regulatory activity is independent of the catabolic activity of PutA, because we show that a point mutation (Glu896→Lys) that prevents catalytic activity allowed the protein to retain its regulatory activity. Expression from the
put
promoters in the presence of proline in a
putA
-proficient background requires a positive regulatory protein, still unidentified, whose expression seems to be ς
54
dependent because the
put
genes were not expressed in a ς
54
-deficient background. Expression of the
putA
and
putP
genes was equally high in the presence of proline in ς
38
- and
ihf
-deficient
P. putida
backgrounds.
Knockout of thep-Coumarate Decarboxylase Gene fromLactobacillus plantarumReveals the Existence of Two Other Inducible Enzymatic Activities Involved in Phenolic Acid Metabolism
Authors: Barthelmebs Lise , Divies Charles , Cavin Jean-François 
Published: July 2002

ABSTRACTLactobacillus plantarumNC8 contains apdcgene coding forp-coumaric acid decarboxylase activity (PDC). A food grade mutant, designated LPD1, in which the chromosomalpdcgene was replaced with the deletedpdcgene copy, was obtained by a two-step homologous recombination process using an unstable replicative vector. The LPD1 mutant strain remained able to weakly metabolizep-coumaric and ferulic acids into vinyl derivatives or into substituted phenyl propionic acids. We have shown thatL. plantarumhas a second acid phenol decarboxylase enzyme, better induced with ferulic acid than withp-coumaric acid, which also displays inducible acid phenol reductase activity that is mostly active when glucose is added. Those two enzymatic activities are in competition forp-coumaric and ferulic acid degradation, and the ratio of the corresponding derivatives depends on induction conditions. Moreover, PDC appeared to decarboxylate ferulic acid in vitro with a specific activity of about 10 nmol · min−1· mg−1in the presence of ammonium sulfate. Finally, PDC activity was shown to confer a selective advantage on LPNC8 grown in acidic media supplemented withp-coumaric acid, compared to the LPD1 mutant devoid of PDC activity.
Input of Protein to Lake Water Microcosms Affects Expression of Proteolytic Enzymes and the Dynamics ofPseudomonasspp
Authors: Worm Jakob , Nybroe Ole 
Published: July 2002

ABSTRACTThe objective of this study was to determine how an input of protein to lake water affects expression of a proteolytic potential and influences the abundance and composition of a specific group of bacteria.Pseudomonasspp. were chosen as a target group that can be recovered on selective growth media and contain both proteolytic and nonproteolytic strains. Amendment with 2 mg of casein per liter increased total proteinase activity (hydrolysis of [3H]casein) by 74%, leucine-aminopeptidase activity (hydrolysis of leucine-methyl-coumarinylamide) by 133%, bacterial abundance by 44%, and phytoplankton biomass (chlorophylla) by 39%. The casein amendment also increased the abundance of culturablePseudomonasspp. by fivefold relative to control microcosms but did not select for proteolytic isolates. Soluble proteins immunochemically related to thePseudomonas fluorescensalkaline proteinase, AprX, were detected in amended microcosms but not in the controls. The expression of this class of proteinase was confirmed exclusively for proteolyticPseudomonasisolates from the microcosms. The population structure ofPseudomonasisolates was determined from genomic fingerprints generated by universally primed PCR, and the analysis indicated that casein amendment led to only minor shifts in population structure. The appearance of AprX-like proteinases in the lake water might thus reflect a general induction of enzyme expression rather than pronounced shifts in thePseudomonaspopulation structure. The limited effect of casein amendment onPseudomonaspopulation structure might be due to the availability of casein hydrolysates to bacteria independent of their proteinase expression. In the lake water, 44% of the total proteinase activity was recovered in 0.22-μm-pore-size filtrates and thus without a direct association with the bacteria providing the extracellular enzyme activity. Since allPseudomonasisolates expressed leucine-aminopeptidase in pure culture, proteolytic as well as nonproteolytic pseudomonads were likely members of the bacterial consortium that metabolized protein in the lake water.
In Situ Detection, Isolation, and Physiological Properties of a Thin Filamentous Microorganism Abundant in Methanogenic Granular Sludges: a Novel Isolate Affiliated with a Clone Cluster, the Green Non-Sulfur Bacteria, Subdivision I
Authors: Sekiguchi Yuji , Takahashi Hiroki , Kamagata Yoichi , Ohashi Akiyoshi , Harada Hideki 
Published: July 2002

ABSTRACT

We previously showed that very thin filamentous bacteria affiliated with the division green non-sulfur bacteria were abundant in the outermost layer of thermophilic methanogenic sludge granules fed with sucrose and several low-molecular-weight fatty acids (Y. Sekiguchi, Y. Kamagata, K. Nakamura, A. Ohashi, H. Harada, Appl. Environ. Microbiol. 65:1280–1288, 1999). Further 16S ribosomal DNA (rDNA) cloning-based analysis revealed that the microbes were classified within a unique clade, green non-sulfur bacteria (GNSB) subdivision I, which contains a number of 16S rDNA clone sequences from various environmental samples but no cultured representatives. To investigate their function in the community and physiological traits, we attempted to isolate the yet-to-be-cultured microbes from the original granular sludge. The first attempt at isolation from the granules was, however, not successful. In the other thermophilic reactor that had been treating fried soybean curd-manufacturing wastewater, we found filamentous microorganisms to outgrow, resulting in the formation of projection-like structures on the surface of granules, making the granules look like sea urchins. 16S rDNA-cloning analysis combined with fluorescent in situ hybridization revealed that the projections were comprised of the uncultured filamentous cells affiliated with the GNSB subdivision I and
Methanothermobacter
-like cells and the very ends of the projections were comprised solely of the filamentous cells. By using the tip of the projection as the inoculum for primary enrichment, a thermophilic, strictly anaerobic, filamentous bacterium, designated strain UNI-1, was successfully isolated with a medium supplemented with sucrose and yeast extract. The strain was a very slow growing bacterium which is capable of utilizing only a limited range of carbohydrates in the presence of yeast extract and produced hydrogen from these substrates. The growth was found to be significantly stimulated when the strain was cocultured with a hydrogen-utilizing methanogen,
Methanothermobacter thermautotrophicus
, suggesting that the strain is a sugar-fermenting bacterium, the growth of which is dependent on hydrogen consumers in the granules.
Phylogenetic and Functional Heterogeneity of Sediment Biofilms along Environmental Gradients in a Glacial Stream
Authors: Battin Tom J. , Wille Anton , Sattler Birgit , Psenner Roland 
Published: July 2002

ABSTRACT

We used in situ hybridization with fluorescently labeled rRNA-targeted oligonucleotide probes concurrently with measurements of bacterial carbon production, biomass, and extracellular polymeric substances (EPS) to describe the bacterial community in sediments along a glacial stream. The abundance of sediment-associated
Archaea
, as detected with the ARCH915 probe, decreased downstream of the glacier snout, and a major storm increased their relative abundance by a factor of 5.5 to 7.9. Bacteria of the
Cytophaga-Flavobacterium
group were also sixfold to eightfold more abundant in the storm aftermath. Furthermore, elevated numbers of
Archaea
and members of the
Cytophaga-Flavobacterium
group characterized the phylogenetic composition of the supraglacial ice community. We postulate that glacial meltwaters constitute a possible source of allochthonous bacteria to the stream biofilms. Although stream water temperature increased dramatically from the glacier snout along the stream (3.5 km), sediment chlorophyll
a
was the best predictor for bacterial carbon production and specific growth rates along the stream. Concomitant with an increase in sediment chlorophyll
a
, the EPS carbohydrate-to-bacterial-cell ratio declined 11- to 15-fold along the stream prior to the storm, which is indicative of a larger biofilm matrix in upstream reaches. We assume that a larger biofilm matrix is required to assure prolonged transient storage and enzymatic processing of allochthonous macromolecules, which are likely the major substrate for microbial heterotrophs. Bacteria of the
Cytophaga-Flavobacterium
cluster, which are well known to degrade complex macromolecules, were most abundant in these stream reaches. Downstream, higher algal biomass continuously supplies heterotrophs with easily available exudates, therefore making a larger matrix unnecessary. As a result, bacterial carbon production and specific growth rates were higher in downstream reaches.
Biodegradation of
n
-Alkylcycloalkanes and
n
-Alkylbenzenes via New Pathways in
Alcanivorax
sp. Strain MBIC 4326
Authors: Dutta Tapan K. , Harayama Shigeaki 
Published: July 2002

ABSTRACT

The degradation of long-chain
n
-alkylbenzenes and
n
-alkylcyclohexanes by
Alcanivorax
sp. strain MBIC 4326 was investigated. The alkyl side chain of these compounds was mainly processed by β-oxidation. In the degradation of
n
-alkylcyclohexanes, cyclohexanecarboxylic acid was formed as an intermediate. This compound was further transformed to benzoic acid via 1-cyclohexene-1-carboxylic acid.
Cyt1Ab1 and Cyt2Ba1 from
Bacillus thuringiensis
subsp.
medellin
and
B. thuringiensis
subsp
. israelensis
Synergize
Bacillus sphaericus
against
Aedes aegypti
and Resistant
Culex quinquefasciatus
(Diptera: Culicidae)
Authors: Wirth Margaret C. , Delécluse Armelle , Walton William E. 
Published: July 2002

ABSTRACT

The interaction of two cytolytic toxins, Cyt1Ab from
Bacillus thuringiensis
subsp.
medellin
and Cyt2Ba from
Bacillus thuringiensis
subsp.
israelensis
, with
Bacillus sphaericus
was evaluated against susceptible and resistant
Culex quinquefasciatus
and the nonsensitive species
Aedes aegypti
. Mixtures of
B. sphaericus
with either cytolytic toxin were synergistic, and
B. sphaericus
resistance in
C. quinquefasciatus
was suppressed from >17,000- to 2-fold with a 3:1 mixture of
B. sphaericus
and Cyt1Ab. This trait may prove useful for combating insecticide resistance and for improving the activity of microbial insecticides.
Decrease in Cell Surface Galactose Residues of
Schizosaccharomyces pombe
Enhances Its Coflocculation with
Pediococcus damnosus
Authors: Peng Xuan , Sun Jun , Michiels Chris , Iserentant Dirk , Verachtert Hubert 
Published: July 2002

ABSTRACT

Pediococcus damnosus
can coflocculate with
Saccharomyces cerevisiae
and cause beer acidification that may or may not be desired. Similar coflocculations occur with other yeasts except for
Schizosaccharomyces pombe
which has galactose-rich cell walls. We compared coflocculation rates of
S. pombe
wild-type species TP4-1D, having a mannose-to-galactose ratio (Man:Gal) of 5 to 6 in the cell wall, with its glycosylation mutants
gms1-1
(Man:Gal = 5:1) and
gms1
Δ (Man:Gal = 1:0). These mutants coflocculated at a much higher level (30 to 45%) than that of the wild type (5%). Coflocculation of the mutants was inhibited by exogenous mannose but not by galactose
.
The
S. cerevisiae mnn2
mutant, with a mannan content similar to that of
gms1
Δ, also showed high coflocculation (35%) and was sensitive to mannose inhibition. Coflocculation of
P. damnosus
and
gms1
Δ (or
mnn2
) also could be inhibited by
gms1
Δ mannan (with unbranched α-1,6-linked mannose residues), concanavalin A (mannose and glucose specific), or NPA lectin (specific for α-1,6-linked mannosyl units). Protease treatment of the bacterial cells completely abolished coflocculation. From these results we conclude that mannose residues on the cell surface of
S. pombe
serve as receptors for a
P. damnosus
lectin but that these receptors are shielded by galactose residues in wild-type strains. Such interactions are important in the production of Belgian acid types of beers in which mixed cultures are used to improve flavor.
Isolation of Toxigenic
Nocardiopsis
Strains from Indoor Environments and Description of Two New
Nocardiopsis
Species,
N. exhalans
sp. nov. and
N. umidischolae
sp. nov
Authors: Peltola Joanna S. P. , Andersson Maria A. , Kämpfer Peter , Auling Georg , Kroppenstedt Reiner M. , Busse Hans-Jürgen , Salkinoja-Salonen Mirja S. , Rainey Frederick A. 
Published: July 2002

ABSTRACT

Nocardiopsis
strains were isolated from water-damaged indoor environments. Two strains (
N. alba
subsp.
alba
704a and a strain representing a novel species, ES10.1) as well as strains of
N. prasina, N. lucentensis,
and
N. tropica
produced methanol-soluble toxins that paralyzed the motility of boar spermatozoa at <30 μg of crude extract (dry weight) ml
−1
.
N. prasina, N. lucentensis, N. tropica
, and strain ES10.1 caused cessation of motility by dissipating the mitochondrial membrane potential, Δψ, of the boar spermatozoa. Indoor strain 704a produced a substance that destroyed cell membrane barrier function and depleted the sperm cells of ATP. Indoor strain 64/93 was antagonistic towards
Corynebacterium renale
. Two indoor
Nocardiopsis
strains were xerotolerant, and all five utilized a wide range of substrates. This combined with the production of toxic substances suggests good survival and potential hazard to human health in water-damaged indoor environments. Two new species,
Nocardiopsis exhalans
sp. nov. (ES10.1
T
) and
Nocardiopsis umidischolae
sp. nov. (66/93
T
), are proposed based on morphology, chemotaxonomic and physiological characters, phylogenetic analysis, and DNA-DNA reassociations.
The Aquatic Budding Bacterium
Blastobacter denitrificans
Is a Nitrogen-Fixing Symbiont of
Aeschynomene indica
Authors: van Berkum Peter , Eardly Bertrand D. 
Published: July 2002

ABSTRACT

Blastobacter
spp. are freshwater bacteria that form rosette structures by cellular attachment to a common base. Comparative analyses of ribosomal 16S rRNA gene and internally transcribed spacer region sequences indicated that
B. denitrificans
is a member of the α-subdivision of
Proteobacteria
. Among the α-
Proteobacteria
,
B. denitrificans
was related to a cluster of genera, including
Rhodopseudomonas palustris
,
Afipia felis
,
Nitrobacter hamburgensis
, and
Bradyrhizobium
spp. Although the precise phylogenetic relationships among these genera could not be established with a high degree of confidence, the sequences of
B. denitrificans
and several bradyrhizobial isolates from nodules of
Aeschynomene indica
were almost identical. Bradyrhizobia are bacteria that form nitrogen-fixing symbioses with legumes, including soybeans (
Glycine max
) and members of the genus
Aeschynomene
. From symbiotic infectiveness tests we demonstrated that the type strain for
B. denitrificans
, IFAM 1005, was capable of forming an effective nitrogen-fixing symbiosis with
A. indica
. Not only do these results reveal a previously unknown ecological adaptation of a relatively obscure aquatic bacterium, but they also demonstrate how evidence gathered from molecular systematic analyses can sometimes provide clues for predicting ecological behavior.