bluuebunny/crossref_metadata_2025_split huggingface dataset:
30S Ribosomal Subunit Assembly Is a Target for Inhibition by Aminoglycosides in
Escherichia coli
Authors: Mehta Roopal , Champney W. Scott 
Published: July 2002

ABSTRACT

The aminoglycosides paromomycin and neomycin were examined in
Escherichia coli
cells for an inhibitory effect on 30S ribosomal subunit assembly. Both compounds inhibited the growth rate, viable cell number, and protein synthesis rate with similar 50% inhibitory concentrations. Each drug also showed a concentration-dependent inhibition of 30S subunit formation. The inhibitory effect on 30S particle formation was approximately equivalent to the inhibitory effect on translation for these antibiotics.
rpoB
Mutation Conferring Rifampin Resistance in
Streptococcus pyogenes
Authors: Aubry-Damon Hélène , Galimand Marc , Gerbaud Guy , Courvalin Patrice 
Published: July 2002

ABSTRACT

Streptococcus pyogenes
BM4478 and
Staphylococcus aureus
BM4479 were isolated from a patient undergoing rifampin therapy. High-level resistance to rifampin was due to the following mutations in the
rpoB
gene: Ser
522
Leu in strain BM4478 and His
526
Asn and Ser
574
Leu in strain BM4479.
In Vitro Activities of Ravuconazole and Voriconazole Compared with Those of Four Approved Systemic Antifungal Agents against 6,970 Clinical Isolates of
Candida
spp
Authors: Pfaller M. A. , Messer S. A. , Hollis R. J. , Jones R. N. , Diekema D. J. 
Published: July 2002

ABSTRACT

The in vitro activities of ravuconazole and voriconazole were compared with those of amphotericin B, flucytosine (5FC), itraconazole, and fluconazole against 6,970 isolates of
Candida
spp. obtained from over 200 medical centers worldwide. Both ravuconazole and voriconazole were very active against all
Candida
spp. (MIC at which 90% of the isolates tested are inhibited [MIC
90
], 0.25 μg/ml; 98% of MICs were ≤1 μg/ml); however, a decrease in the activities of both of these agents was noted among isolates that were susceptible-dose dependent (fluconazole MIC, 16 to 32 μg/ml) and resistant (MIC, ≥ 64 μg/ml) to fluconazole.
Candida albicans
was the most susceptible species (MIC
90
of both ravuconazole and voriconazole, 0.03 μg/ml), and
C. glabrata
was the least susceptible species (MIC
90
, 1 to 2 μg/ml). Ravuconazole and voriconazole were each more active in vitro than amphotericin B, 5FC, itraconazole, and fluconazole against all
Candida
spp. and were the only agents with good in vitro activity against
C. krusei
. These results provide further evidence for the spectrum and potency of ravuconazole and voriconazole against a large and geographically diverse collection of
Candida
spp.
Cold Shock and Its Effect on Ribosomes and Thermal Tolerance in
Listeria monocytogenes
Authors: Bayles Darrell O. , Tunick Michael H. , Foglia Thomas A. , Miller Arthur J. 
Published: July 2002

ABSTRACT

Differential scanning calorimetry (DSC) and fatty acid analysis were used to determine how cold shocking reduces the thermal stability of
Listeria monocytogenes
. Additionally, antibiotics that can elicit production of cold or heat shock proteins were used to determine the effect of translation blockage on ribosome thermal stability. Fatty acid profiles showed no significant variations as a result of cold shock, indicating that changes in membrane fatty acids were not responsible for the cold shock-induced reduction in thermal tolerance. Following a 3-h cold shock from 37 to 0°C, the maximum denaturation temperature of the 50S ribosomal subunit and 70S ribosomal particle peak was reduced from 73.4 ± 0.1°C (mean ± standard deviation) to 72.1 ± 0.5°C (
P
≤ 0.05), indicating that cold shock induced instability in the associated ribosome structure. The maximum denaturation temperature of the 30S ribosomal subunit peak did not show a significant shift in temperature (from 67.5 ± 0.4°C to 66.8 ± 0.5°C) as a result of cold shock, suggesting that either 50S subunit or 70S particle sensitivity was responsible for the intact ribosome fragility. Antibiotics that elicited changes in maximum denaturation temperature in ribosomal components also elicited reductions in thermotolerance. Together, these data suggest that ribosomal changes resulting from cold shock may be responsible for the decrease in
D
value observed when
L. monocytogenes
is cold shocked.
Internal Trehalose Protects Endocytosis from Inhibition by Ethanol inSaccharomyces cerevisiae
Authors: Lucero P. , Peñalver E. , Moreno E. , Lagunas R. 
Published: July 2002

ABSTRACTEndocytosis inSaccharomyces cerevisiaeis inhibited by concentrations of ethanol of 2 to 6% (vol/vol), which are lower than concentrations commonly present in its natural habitats. In spite of this inhibition, endocytosis takes place under enological conditions when high concentrations of ethanol are present. Therefore, it seems that yeast has developed some means to circumvent the inhibition. In this work we have investigated this possibility. We identified two stress conditions under which endocytosis was resistant to inhibition by ethanol: fermentation during nitrogen starvation and growth on nonfermentable substrates. Under these conditions, yeast accumulates stress protectors, primarily trehalose and Hsp104, a protein required for yeast to survive ethanol stress. We found the following. (i) The appearance of ethanol resistance was accompanied by trehalose accumulation. (ii) Mutant cells unable to synthesize trehalose also were unable to develop resistance. (iii) Mutant cells that accumulated trehalose during growth on sugars were resistant to ethanol even under this nonstressing condition. (iv) Mutant cells unable to synthesize Hsp104 were able to develop resistance. We conclude that trehalose is the major factor in the protection of endocytosis from ethanol. Our results suggest another important physiological role for trehalose in yeast.
Advances in Development of a Genetic System for
Thermoanaerobacterium
spp.: Expression of Genes Encoding Hydrolytic Enzymes, Development of a Second Shuttle Vector, and Integration of Genes into the Chromosome
Authors: Mai Volker , Wiegel Juergen 
Published: July 2002

ABSTRACT

Despite recent success in transforming various thermophilic gram-type-positive anaerobes with plasmid DNA, use of shuttle vectors for the expression of genes other than antibiotic resistance markers has not previously been described. We constructed new vectors in order to express heterologous hydrolytic enzymes in our model system,
Thermoanaerobacterium saccharolyticum
JW/SL-YS485. Transformed
Thermoanaerobacterium
expressed active enzyme, indicating that this system may function as an alternate expression host, especially for genes with a thermophilic origin. To develop further the genetic system for
T. saccharolyticum
JW/SL-YS485, two improved
Escherichia coli-Thermoanaerobacterium
shuttle vectors, pRKM1 and pRUKM, were constructed. Furthermore, the kanamycin resistance cassette alone and the kanamycin resistance cassette plus the cellobiohydrolase gene (
cbhA
) from
Clostridium thermocellum
JW20 were integrated into the xylanase gene (
xynA
) region of the
Thermoanaerobacterium
chromosome via homologous recombination using pUC-based suicide vectors pUXK and pUXKC.
Isolation, Purification, and Characterization of a Killer Protein fromSchwanniomyces occidentalis
Authors: Chen Wen-Bao , Han Yuh-Fehng , Jong Shung-Chang , Chang Shenq-Chyi 
Published: July 2002

ABSTRACTThe yeastSchwanniomyces occidentalisproduces a killer toxin lethal to sensitive strains ofSaccharomyces cerevisiae. Killer activity is lost after pepsin and papain treatment, suggesting that the toxin is a protein. We purified the killer protein and found that it was composed of two subunits with molecular masses of approximately 7.4 and 4.9 kDa, respectively, but was not detectable with periodic acid-Schiff staining. A BLAST search revealed that residues 3 to 14 of the 4.9-kDa subunit had 75% identity and 83% similarity with killer toxin K2 fromS. cerevisiaeat positions 271 to 283. Maximum killer activity was between pH 4.2 and 4.8. The protein was stable between pH 2.0 and 5.0 and inactivated at temperatures above 40°C. The killer protein was chromosomally encoded. Mannan, but not β-glucan or laminarin, prevented sensitive yeast cells from being killed by the killer protein, suggesting that mannan may bind to the killer protein. Identification and characterization of a killer strain ofS. occidentalismay help reduce the risk of contamination by undesirable yeast strains during commercial fermentations.
Construction and Characterization of an
Escherichia coli
Strain Genetically Engineered for Ni(II) Bioaccumulation
Authors: Krishnaswamy Rahul , Wilson David B. 
Published: July 2002

ABSTRACT

An
Escherichia coli
strain that accumulated Ni(II) was constructed by introducing the
nixA
gene (coding for a nickel transport system) from
Helicobacter pylori
into JM109 cells that expressed a glutathione
S
-transferase–pea metallothionein fusion protein. The resulting strain accumulated 15 μmol of Ni(II) per g (dry weight) from a 10 μM Ni(II) solution, four times the level taken up by JM109 cells. Ni(II) accumulation did not require an energy source, was inhibited by only 50% by 0.1 M NaCl, and occurred over the pH range from 3 to 9.
Chemoraces and Habitat Specialization of
Claviceps purpurea
Populations
Authors: Pažoutová Sylvie , Olšovská Jana , Linka Marek , Kolı́nská Renata , Flieger Miroslav 
Published: July 2002

ABSTRACT

We studied genetic variability of 100 isolates of
Claviceps purpurea
by using randomly amplified polymorphic DNA (RAPD), an
Eco
RI restriction site polymorphism in the 5.8S ribosomal DNA (rDNA), the alkaloids produced, and conidial morphology. We identified three groups: (i) group G1 from fields and open meadows (57 isolates), (ii) group G2 from shady or wet habitats (41 isolates), and (iii) group G3 from
Spartina anglica
from salt marshes (2 isolates). The sclerotia of G1 isolates contained ergotamines and ergotoxines; G2 isolates produced ergosine and ergocristine along with small amounts of ergocryptine; and G3 isolates produced ergocristine and ergocryptine. The conidia of G1 isolates were 5 to 8 μm long, the conidia of G2 isolates were 7 to 10 μm long, and the conidia of G3 isolates were 10 to 12 μm long. Sclerotia of the G2 and G3 isolates floated on water. In the 5.8S rDNA analysis, an
Eco
RI site was found in G1 and G3 isolates but not in G2 isolates. The host preferences of the groups were not absolute, and there were host genera that were common to both G1 and G2; the presence of members of different groups in the same locality was rare. Without the use of RAPD or rDNA polymorphism, it was not possible to distinguish the three groups solely on the basis of phenotype, host, or habitat. In general, populations of
C. purpurea
are not host specialized, as previously assumed, but they are habitat specialized, and collecting strategies and toxin risk assessments should be changed to reflect this paradigm shift.
Dissimilatory Metal Reduction by the Facultative Anaerobe
Pantoea agglomerans
SP1
Authors: Francis Chris A. , Obraztsova Anna Y. , Tebo Bradley M. 
Published: July 2002

ABSTRACT

Anaerobic enrichments with acetate as the electron donor and Fe(III) as the terminal electron acceptor were obtained from sediments of Salt Pond, a coastal marine basin near Woods Hole, Mass. A pure culture of a facultatively anaerobic Fe(III) reducer was isolated, and 16S rRNA analysis demonstrated that this organism was most closely related to
Pantoea
(formerly
Enterobacter
)
agglomerans
, a member of the family
Enterobacteriaceae
within the gamma subdivision of the
Proteobacteria
. This organism, designated strain SP1, can grow by coupling the oxidation of acetate or H
2
to the reduction of a variety of electron acceptors, including Fe(III), Mn(IV), Cr(VI), and the humic substance analog 2,6-anthraquinone disulfonate, but not sulfate. To our knowledge, this is the first mesophilic facultative anaerobe reported to couple acetate oxidation to dissimilatory metal reduction.
Characterization of a Foldase, Protein Disulfide Isomerase A, in the Protein Secretory Pathway of
Aspergillus niger
Authors: Ngiam Celina , Jeenes David J. , Punt Peter J. , Van Den Hondel Cees A. M. J. J. , Archer David B. 
Published: July 2002

ABSTRACT

Protein disulfide isomerase (PDI) is important in assisting the folding and maturation of secretory proteins in eukaryotes. A gene,
pdiA
, encoding PDIA was previously isolated from
Aspergillus niger
, and we report its functional characterization here. Functional analysis of PDIA showed that it catalyzes the refolding of denatured and reduced RNase A.
pdiA
also complemented PDI function in a
Saccharomyces cerevisiae Δpdi1
mutant in a yeast-based killer toxin assay. Levels of
pdiA
mRNA and PDIA protein were raised by the accumulation of unfolded proteins in the endoplasmic reticulum. This response of
pdiA
mRNA levels was slower and lower in magnitude than that of
A. niger bipA
, suggesting that the induction of
pdiA
is not part of the primary stress response. An increased level of
pdiA
transcripts was also observed in two
A. niger
strains overproducing a heterologous protein, hen egg white lysozyme (HEWL). Although overexpression of PDI has been successful in increasing yields of some heterologous proteins in
S. cerevisiae
, overexpression of PDIA did not increase secreted yields of HEWL in
A. niger
, suggesting that PDIA itself is not limiting for secretion of this protein. Downregulation of
pdiA
by antisense mRNA reduced the levels of microsomal PDIA activity by up to 50%, lowered the level of PDIA as judged by Western blots, and lowered the secreted levels of glucoamylase by 60 to 70%.
Phosphate Inhibits Acetotrophic Methanogenesis on Rice Roots
Authors: Conrad Ralf , Klose Melanie , Claus Peter 
Published: July 2002

ABSTRACT

The contribution of acetate- and H
2
/CO
2
-dependent methanogenesis to total CH
4
production was determined in excised washed rice roots by radiolabeling, methyl fluoride inhibition, and stable carbon isotope fractionation. Addition of ≥20 mM phosphate inhibited methanogenesis, which then was exclusively from H
2
/CO
2
. Otherwise, acetate contributed about 50 to 60% of the total methanogenesis, demonstrating that phosphate specifically inhibited acetotrophic methanogens on rice roots.
pH Regulation of Pectate Lyase Secretion Modulates the Attack ofColletotrichum gloeosporioideson Avocado Fruits
Authors: Yakoby Nir , Kobiler Ilana , Dinoor Amos , Prusky Dov 
Published: July 2002

ABSTRACTGrowth ofColletotrichum gloeosporioidesin pectolytic enzyme-inducing medium (PEIM) increased the pH of the medium from 3.8 to 6.5. Pectate lyase (PL) secretion was detected when the pH reached 5.8, and the level of secretion increased up to pH 6.5. PL gene (pel) transcript production began at pH 5.0 and increased up to pH 5.7. PL secretion was never detected when the pH of the inducing medium was lower than 5.8 or whenC. gloeosporioideshyphae were transferred from PL-secreting conditions at pH 6.5 to pH 3.8. This behavior differed from that of polygalacturonase (PG), wherepgtranscripts and protein secretion were detected at pH 5.0 and continued up to 5.7. Under in vivo conditions, the pH of unripe pericarp of freshly harvested avocado (Persea americanacv. Fuerte) fruits, resistant toC. gloeosporioidesattack, was 5.2, whereas in ripe fruits, when decay symptoms were expressed, the pericarp pH had increased to 6.3. Two avocado cultivars, Ardit and Ettinger, which are resistant toC. gloeosporioidesattack, had pericarp pHs of less than 5.5, which did not increase during ripening. The present results suggest that host pH regulates the secretion of PL and may affectC. gloeosporioidespathogenicity. The mechanism found in avocado may have equivalents in other postharvest pathosystems and suggests new approaches for breeding against and controlling postharvest diseases.
Genetic Analysis of Chromosomal Regions of
Lactococcus lactis
Acquired by Recombinant Lytic Phages
Authors: Durmaz Evelyn , Klaenhammer Todd R. 
Published: July 2002

ABSTRACT

Recombinant phages are generated when
Lactococcus lactis
subsp.
lactis
harboring plasmids encoding the abortive type (Abi) of phage resistance mechanisms is infected with small isometric phages belonging to the P335 species. These phage variants are likely to be an important source of virulent new phages that appear in dairy fermentations. They are distinguished from their progenitors by resistance to Abi defenses and by altered genome organization, including regions of
L. lactis
chromosomal DNA. The objective of this study was to characterize four recombinant variants that arose from infection of
L. lactis
NCK203 (Abi
+
) with phage φ31.
Hin
dIII restriction maps of the variants (φ31.1, φ31.2, φ31.7, and φ31.8) were generated, and these maps revealed the regions containing recombinant DNA. The recombinant region of phage φ31.1, the variant that occurred most frequently, was sequenced and revealed 7.8 kb of new DNA compared with the parent phage, φ31. This region contained numerous instances of homology with various lactococcal temperate phages, as well as homologues of the lambda recombination protein BET and
Escherichia coli
Holliday junction resolvase Rus, factors which may contribute to efficient recombination processes. A sequence analysis and phenotypic tests revealed a new origin of replication in the φ31.1 DNA, which replaced the φ31 origin. Three separate
Hin
dIII fragments, accounting for most of the recombinant region of φ31.1, were separately cloned into gram-positive suicide vector pTRK333 and transformed into NCK203. Chromosomal insertions of each plasmid prevented the appearance of different combinations of recombinant phages. The chromosomal insertions did not affect an inducible prophage present in NCK203. Our results demonstrated that recombinant phages can acquire DNA cassettes from different regions of the chromosome in order to overcome Abi defenses. Disruption of these regions by insertion can alter the types and diversity of new phages that appear during phage-host interactions.
Ionizing-Radiation Resistance in the Desiccation-Tolerant Cyanobacterium
Chroococcidiopsis
Authors: Billi Daniela , Friedmann E. Imre , Hofer Kurt G. , Caiola Maria Grilli , Ocampo-Friedmann Roseli 
Published: July 2002

ABSTRACT

The effect of X-ray irradiation on cell survival, induction, and repair of DNA damage was studied by using 10
Chroococcidiopsis
strains isolated from desert and hypersaline environments. After exposure to 2.5 kGy, the percentages of survival for the strains ranged from 80 to 35%. In the four most resistant strains, the levels of survival were reduced by 1 or 2 orders of magnitude after irradiation with 5 kGy; viable cells were recovered after exposure to 15 kGy but not after exposure to 20 kGy. The severe DNA damage evident after exposure to 2.5 kGy was repaired within 3 h, and the severe DNA damage evident after exposure to 5 kGy was repaired within 24 h. The increase in trichloroacetic acid-precipitable radioactivity in the culture supernatant after irradiation with 2.5 kGy might have been due to cell lysis and/or an excision process involved in DNA repair. The radiation resistance of
Chroococcidiopsis
strains may reflect the ability of these cyanobacteria to survive prolonged desiccation through efficient repair of the DNA damage that accumulates during dehydration.
Novel Scheme for Biosynthesis of Aryl Metabolites from
l
-Phenylalanine in the Fungus
Bjerkandera adusta
Authors: Lapadatescu Carmen , Giniès Christian , Le Quéré Jean-Luc , Bonnarme Pascal 
Published: July 2002

ABSTRACT

Aryl metabolite biosynthesis was studied in the white rot fungus
Bjerkandera adusta
cultivated in a liquid medium supplemented with
l
-phenylalanine. Aromatic compounds were analyzed by gas chromatography-mass spectrometry following addition of labelled precursors (
14
C- and
13
C-labelled
l
-phenylalanine), which did not interfere with fungal metabolism. The major aromatic compounds identified were benzyl alcohol, benzaldehyde (bitter almond aroma), and benzoic acid. Hydroxy- and methoxybenzylic compounds (alcohols, aldehydes, and acids) were also found in fungal cultures. Intracellular enzymatic activities (phenylalanine ammonia lyase, aryl-alcohol oxidase, aryl-alcohol dehydrogenase, aryl-aldehyde dehydrogenase, lignin peroxidase) and extracellular enzymatic activities (aryl-alcohol oxidase, lignin peroxidase), as well as aromatic compounds, were detected in
B. adusta
cultures. Metabolite formation required de novo protein biosynthesis. Our results show that
l
-phenylalanine was deaminated to
trans
-cinnamic acid by a phenylalanine ammonia lyase and
trans
-cinnamic acid was in turn converted to aromatic acids (phenylpyruvic, phenylacetic, mandelic, and benzoylformic acids); benzaldehyde was a metabolic intermediate. These acids were transformed into benzaldehyde, benzyl alcohol, and benzoic acid. Our findings support the hypothesis that all of these compounds are intermediates in the biosynthetic pathway from
l
-phenylalanine to aryl metabolites. Additionally,
trans
-cinnamic acid can also be transformed via β-oxidation to benzoic acid. This was confirmed by the presence of acetophenone as a β-oxidation degradation intermediate. To our knowledge, this is the first time that a β-oxidation sequence leading to benzoic acid synthesis has been found in a white rot fungus. A novel metabolic scheme for biosynthesis of aryl metabolites from
l
-phenylalanine is proposed.
Bacterial Symbiont Transmission in the Wood-Boring Shipworm
Bankia setacea
(Bivalvia: Teredinidae)
Authors: Sipe Alison R. , Wilbur Ami E. , Cary S. Craig 
Published: July 2002

ABSTRACT

The Teredinidae (shipworms) are a morphologically diverse group of marine wood-boring bivalves that are responsible each year for millions of dollars of damage to wooden structures in estuarine and marine habitats worldwide. They exist in a symbiosis with cellulolytic nitrogen-fixing bacteria that provide the host with the necessary enzymes for survival on a diet of wood cellulose. These symbiotic bacteria reside in distinct structures lining the interlamellar junctions of the gill. This study investigated the mode by which these nutritionally essential bacterial symbionts are acquired in the teredinid
Bankia setacea
. Through 16S ribosomal DNA (rDNA) sequencing, the symbiont residing within the
B. setacea
gill was phylogenetically characterized and shown to be distinct from previously described shipworm symbionts. In situ hybridization using symbiont-specific 16S rRNA-directed probes bound to bacterial ribosome targets located within the host gill coincident with the known location of the gill symbionts. These specific probes were then used as primers in a PCR-based assay which consistently detected bacterial rDNA in host gill (symbiont containing), gonad tissue, and recently spawned eggs, demonstrating the presence of symbiont cells in host ovary and offspring. These results suggest that
B. setacea
ensures successful inoculation of offspring through a vertical mode of symbiont transmission and thereby enables a broad distribution of larval settlement.