bluuebunny/crossref_metadata_2025_split huggingface dataset:
The
cel4
Gene of
Agaricus bisporus
Encodes a β-Mannanase
Authors: Tang C. M. , Waterman L. D. , Smith M. H. , Thurston C. F. 
Published: July 2002

ABSTRACT

Mannases have industrial uses in food and pulp industries, and their regulation may influence development of the mushrooms of commercially important basidiomycetes. We expressed an
Agaricus bisporus cel4
cDNA, which encodes a mannanase, in
Saccharomyces cerevisiae
and
Pichia pastoris
. CEL4 had no detectable activity on cellulose or xylan. This gene is the first isolated from this economically important fungus to encode a mannanase.
P. pastoris
secreted about three times more CEL4 than
S. cerevisiae
. The removal of the cellulose-binding domain of CEL4 lowered the secreted specific activity by
P. pastoris
by approximately 97%. The genomic sequence of
cel4
was isolated by screening a cosmid library of
A. bisporus
C54-
carb8
. The open reading frame was interrupted by 12 introns. The level of extracellular CEL4 increases dramatically at the postharvest stage in compost extracts of
A. bisporus
fruiting cultures. In laboratory liquid cultures of
A. bisporus
, the activity of CEL4 detected in the culture filtrate reached a maximum after 21 days. The levels of CEL4 broadly mirrored the levels of enzyme activity. In the Solka floc-bound mycelium, CEL4 protein showed a maximum after 2 to 3 weeks of culture and then declined. Changes in CEL4 activity during fruiting-body development suggest that hemicellulose utilization plays an important role in sporophore formation. The availability of the cloned gene will further studies of compost decomposition and the extracellular enzymes that fungi deploy in this process.
Membrane Permeabilization in Relation to Inactivation Kinetics of
Lactobacillus
Species due to Pulsed Electric Fields
Authors: Wouters Patrick C. , Bos Ad P. , Ueckert Joerg 
Published: July 2002

ABSTRACT

Membrane permeabilization due to pulsed electric field (PEF) treatment of gram-positive
Lactobacillus
cells was investigated by using propidium iodide uptake and single-cell analysis with flow cytometry. Electric field strength, energy input, treatment time, and growth phase affected membrane permeabilization of
Lactobacillus plantarum
during PEF treatment. A correlation between PEF inactivation and membrane permeabilization of
L. plantarum
cells was demonstrated, whereas no relationship was observed between membrane permeabilization and heat inactivation. The same results were obtained with a
Lactobacillus fermentum
strain, but the latter organism was more PEF resistant and exhibited less membrane permeabilization, indicating that various bacteria have different responses to PEF treatment. While membrane permeabilization was the main factor involved in the mechanism of inactivation, the growth phase and the acidity of the environment also influenced inactivation. By using flow cytometry it was possible to sort cells in the
L. plantarum
population based on different cell sizes and shapes, and the results were confirmed by image analysis. An apparent effect of morphology on membrane permeabilization was observed, and larger cells were more easily permeabilized than smaller cells. In conclusion, our results indicate that the ability of PEF treatment to cause membrane permeabilization is an important factor in determining inactivation. This finding should have an effect on the final choice of the processing parameters used so that all microorganisms can be inactivated and, consequently, on the use of PEF treatment as an alternative method for preserving food products.
Novel Ring Cleavage Products in the Biotransformation of Biphenyl by the Yeast
Trichosporon mucoides
Authors: Sietmann Rabea , Hammer Elke , Specht Michael , Cerniglia Carl E. , Schauer Frieder 
Published: July 2002

ABSTRACT

The yeast
Trichosporon mucoides
, grown on either glucose or phenol, was able to transform biphenyl into a variety of mono-, di-, and trihydroxylated derivatives hydroxylated on one or both aromatic rings. While some of these products accumulated in the supernatant as dead end products, the
ortho
-substituted dihydroxylated biphenyls were substrates for further oxidation and ring fission. These ring fission products were identified by high-performance liquid chromatography, gas chromatography-mass spectrometry, and nuclear magnetic resonance analyses as phenyl derivatives of hydroxymuconic acids and the corresponding pyrones. Seven novel products out of eight resulted from the oxidation and ring fission of 3,4-dihydroxybiphenyl. Using this compound as a substrate, 2-hydroxy-4-phenylmuconic acid, (5-oxo-3-phenyl-2,5-dihydrofuran-2-yl)acetic acid, and 3-phenyl-2-pyrone-6-carboxylic acid were identified. Ring cleavage of 3,4,4′-trihydroxybiphenyl resulted in the formation of [5-oxo-3-(4′-hydroxyphenyl)-2,5-dihydrofuran-2-yl]acetic acid, 4-(4′-hydroxyphenyl)-2-pyrone-6-carboxylic acid, and 3-(4′-hydroxyphenyl)-2-pyrone-6-carboxylic acid. 2,3,4-Trihydroxybiphenyl was oxidized to 2-hydroxy-5-phenylmuconic acid, and 4-phenyl-2-pyrone-6-carboxylic acid was the transformation product of 3,4,5-trihydroxybiphenyl. All these ring fission products were considerably less toxic than the hydroxylated derivatives.
Chlorine Disinfection of Atypical Mycobacteria Isolated from a Water Distribution System
Authors: Le Dantec Corinne , Duguet Jean-Pierre , Montiel Antoine , Dumoutier Nadine , Dubrou Sylvie , Vincent Véronique 
Published: July 2002

ABSTRACT

We studied the resistance of various mycobacteria isolated from a water distribution system to chlorine. Chlorine disinfection efficiency is expressed as the coefficient of lethality (liters per minute per milligram) as follows:
Mycobacterium fortuitum
(0.02) >
M. chelonae
(0.03) >
M. gordonae
(0.09) >
M. aurum
(0.19). For a
C
·
t
value (product of the disinfectant concentration and contact time) of 60 mg · min · liter
−1
, frequently used in water treatment lines, chlorine disinfection inactivates over 4 log units of
M. gordonae
and 1.5 log units of
M. fortuitum
or
M. chelonae
.
C
·
t
values determined under similar conditions show that even the most susceptible species,
M. aurum
and
M. gordonae
, are 100 and 330 times more resistant to chlorine than
Escherichia coli
. We also investigated the effects of different parameters (medium, pH, and temperature) on chlorine disinfection in a chlorine-resistant
M. gordonae
model. Our experimental results follow the Arrhenius equation, allowing the inactivation rate to be predicted at different temperatures. Our results show that
M. gordonae
is more resistant to chlorine in low-nutrient media, such as those encountered in water, and that an increase in temperature (from 4°C to 25°C) and a decrease in pH result in better inactivation.
Norwalk-Like Virus Sequences in Mineral Waters: One-Year Monitoring of Three Brands
Authors: Beuret Christian , Kohler Dorothe , Baumgartner Andreas , Lüthi Thomas M. 
Published: July 2002

ABSTRACT
In a recent study, RNA with nucleotide sequeces specific for “Norwalk-like viruses” (NLV) was detected in 11 different brands of European mineral waters. To clarify this finding, a 1-year monitoring study was conducted. Samples of three European brands of mineral water without gas were monitored weekly by reverse transcriptase PCR using generic and genogroup-specific oligonucleotides. Additional analyses were performed to investigate a possible correlation between NLV sequence contamination and mineral water lot numbers, the long-term stability (persistence) of NLV sequences in mineral water, and the level of contamination. NLV sequences were detected in 53 of 159 samples analyzed (33%) and belonged entirely to genogroup II. Although all NLV strains identified were closely related, three mineral water brand-specific clusters could be identified for both primer systems by sequencing. Analyses of second samples from lots previously shown to be positive for NLV sequences gave corresponding results in 45 of 53 cases (85%) (within a six-pack). NLV persistence was tested by analyzing 10 positive samples after 6 and 12 months of storage in darkness at room temperature. After 6 months, all samples remained positive; after 12 months, 9 of 10 samples were still positive for NLV sequences. No NLV sequences could be detected by analysis of 0.1-liter aliquots of 53 samples shown to be positive by testing of 1-liter volumes. Based on this fact and a test sensitivity of approximately 10 viral units, levels of contamination in positive mineral water samples were estimated to be in the range of 10 to 100 genomic equivalents per liter.
Impaired Cutinase Secretion in
Saccharomyces cerevisiae
Induces Irregular Endoplasmic Reticulum (ER) Membrane Proliferation, Oxidative Stress, and ER-Associated Degradation
Authors: Sagt C. M. J. , Müller W. H. , van der Heide L. , Boonstra J. , Verkleij A. J. , Verrips C. T. 
Published: July 2002

ABSTRACT

Impaired secretion of the hydrophobic CY028 cutinase invokes an unfolded protein response (UPR) in
Saccharomyces cerevisiae
cells. Here we show that the UPR in CY028-expressing
S. cerevisiae
cells is manifested as an aberrant morphology of the endoplasmic reticulum (ER) and as extensive membrane proliferation compared to the ER morphology and membrane proliferation of wild-type CY000-producing
S. cerevisiae
cells. In addition, we observed oxidative stress, which resulted in a 21-fold increase in carbonylated proteins in the CY028-producing
S. cerevisiae
cells. Moreover, CY028-producing
S. cerevisiae
cells use proteasomal degradation to reduce the amount of accumulated CY028 cutinase, thereby attenuating the stress invoked by CY028 cutinase expression. This proteasomal degradation occurs within minutes and is characteristic of ER-associated degradation (ERAD). Our results clearly show that impaired secretion of the heterologous, hydrophobic CY028 cutinase in
S. cerevisiae
cells leads to protein aggregation in the ER, aberrant ER morphology and proliferation, and oxidative stress, as well as a UPR and ERAD.
Expression of Regeneration and Tolerance Factor Correlates Directly with Human Immunodeficiency Virus Infection and Inversely with Hepatitis C Virus Infection
Authors: Sung C. C. , Boomer J. S. , Givens T. S. , DuChateau B. K. , Lepe M. R. , Feller A. , Westerman M. P. , Gilman-Sachs A. , Chedid A. , Beaman K. D. 
Published: July 2002

ABSTRACTHepatitis C virus (HCV) and human immunodeficiency virus (HIV) cause two of the most prevalent debilitating viral infections. HIV appears to induce a skewing toward a Th2 response, while in HCV infection a Th1 response appears to dominate. Regeneration and tolerance factor (RTF) may participate in driving or sustaining a Th2 cytokine response. The expression of RTF on CD3+T cells of HIV-seropositive (HIV+) individuals is increased. The purpose of this study was to compare the expression of RTF during HIV infections with that during HCV infections. Three-color flow-cytometric analysis of peripheral blood collected from HIV+HCV-seropositive (HCV+), HIV- and HCV-seropositive (HIV+HCV+), and HIV- and HCV-seronegative (HIV−HCV−) individuals was performed. Levels of RTF expression on T-lymphocyte subsets from these groups were compared, as were levels of RTF expression on activated T cells expressing CD38 and HLA-DR, to determine the relationship of RTF expression to these infections. We demonstrated that the expression of RTF on surfaces of T cells from HIV+individuals is upregulated and that its expression on T cells from HCV+individuals is downregulated. A twofold increase in the mean channel fluorescence of RTF on CD3+T cells was seen in both HIV+and HIV+HCV+individuals compared to HIV−HCV−individuals. HCV+individuals had lower levels of RTF expression than HIV−HCV−individuals (P< 0.005 for CD4+;P< 0.0005 for CD8+). In terms of percentages of T cells expressing RTF, the groups were ranked as follows: HIV+> HIV+HCV+> HIV−HCV−> HCV+. The results indicate that RTF expression correlates with HIV-associated immune activation and may be associated with Th2-type responses.
WdChs2p, a Class I Chitin Synthase, Together with WdChs3p (Class III) Contributes to Virulence in
Wangiella
(
Exophiala
)
dermatitidis
Authors: Wang Zheng , Zheng Li , Liu Hongbo , Wang Qingfeng , Hauser Melinda , Kauffman Sarah , Becker Jeffery M. , Szaniszlo Paul J. 
Published: July 2002

ABSTRACT

The chitin synthase structural gene
WdCHS2
was isolated by screening a subgenomic DNA library of
Wangiella dermatitidis
by using a 0.6-kb PCR product of the gene as a probe. The nucleotide sequence revealed a 2,784-bp open reading frame, which encoded 928 amino acids, with a 59-bp intron near its 5′ end. Derived protein sequences showed highest amino acid identities with those derived from the
CiCHS1
gene of
Coccidioides immitis
and the
AnCHSC
gene of
Aspergillus nidulans
. The derived sequence also indicated that WdChs2p is an orthologous enzyme of Chs1p of
Saccharomyces cerevisiae
, which defines the class I chitin synthases. Disruptions of
WdCHS2
produced strains that showed no obvious morphological defects in yeast vegetative growth or in ability to carry out polymorphic transitions from yeast cells to hyphae or to isotropic forms. However, assays showed that membranes of
wdchs2
Δ mutants were drastically reduced in chitin synthase activity. Other assays of membranes from a
wdchs1
Δ
wdchs3
Δ
wdchs4
Δ triple mutant showed that their residual chitin synthase activity was extremely sensitive to trypsin activation and was responsible for the majority of zymogenic activity. Although no loss of virulence was detected when
wdchs2
Δ strains were tested in a mouse model of acute infection,
wdchs2
Δ
wdchs3
Δ disruptants were considerably less virulent in the same model, even though
wdchs3
Δ strains also had previously shown no loss of virulence. This virulence attenuation in the
wdchs2
Δ
wdchs3
Δ mutants was similarly documented in a limited fashion in more-sensitive cyclophosphamide-induced immunocompromised mice. The importance of WdChs2p and WdChs3p to the virulence of
W. dermatitidis
was then confirmed by reconstituting virulence in the double mutant by the reintroduction of either
WdCHS2
or
WdCHS3
into the
wdchs2
Δ
wdchs3
Δ mutant background.
Further Characterization of Complement Regulator-Acquiring Surface Proteins ofBorrelia burgdorferi
Authors: Kraiczy Peter , Skerka Christine , Brade Volker , Zipfel Peter F. 
Published: July 2002

ABSTRACTThe three genospeciesBorrelia burgdorferi,Borrelia garinii, andBorrelia afzelii, all causative agents of Lyme disease, differ in their susceptibilities to human complement-mediated lysis. We recently reported that serum resistance of borrelias correlates largely with their ability to bind the human complement regulators FHL-1/reconectin and factor H. To date, two complement regulator-acquiring-proteins (CRASP-1 and CRASP-2) have been identified in serum-resistantB.afzeliiisolates (P. Kraiczy, C. Skerka, M. Kirschfink, V. Brade, and P. F. Zipfel, Eur. J. Immunol. 31:1674–1684, 2001). Here, we present a comprehensive study of the CRASPs detectable in both serum-resistant and intermediate serum-sensitiveB. afzeliiandB. burgdorferiisolates. These CRASPs were designated according to the genospecies either as BaCRASPs, when derived fromB. afzelii, or as BbCRASPs, for proteins identified inB. burgdorferiisolates. Each borrelial isolate expresses distinct CRASPs that can be differentiated by their mobility and binding phenotypes. A detailed comparison reveals overlapping and even identical binding profiles for BaCRASP-1 (27.5 kDa), BbCRASP-1 (25.9 kDa), and BbCRASP-2 (23.2 kDa), which bind FHL-1/reconectin strongly and interact weakly with factor H. In contrast, twoB. afzeliiproteins (BaCRASP-4 [19.2 kDa] and BaCRASP-5 [22.5 kDa]) and threeB. burgdorferiproteins (BbCRASP-3 [19.8 kDa], BbCRASP-4 [18.5 kDa], and BbCRASP-5 [17.7 kDa]) bind factor H but not FHL-1/reconectin. Most CRASPs bind both human immune regulators at their C-terminal ends. Temperature-dependent up-regulation of CRASPs (BaCRASP-1, BaCRASP-2, and BaCRASP-5) is detected in low-passage borrelias cultured at 33 or 37°C compared with those cultured at 20°C. The characterization of the individual CRASPs on the molecular level is expected to identify new virulence factors and potential vaccine candidates.
Functional Activity of Anti-Neisserial Surface Protein A Monoclonal Antibodies against Strains ofNeisseria meningitidisSerogroup B
Authors: Moe G. R. , Zuno-Mitchell P. , Lee S. S. , Lucas A. H. , Granoff D. M. 
Published: July 2002

ABSTRACTNeisserial surface protein A (NspA) is currently being investigated with humans as a candidate vaccine for the prevention of meningococcal disease. Although NspA is highly conserved, the ability of anti-NspA antibodies to bind to or elicit complement-mediated bactericidal activity against diverseNeisseria meningitidisserogroup B strains is controversial. To evaluate strain differences in NspA surface accessibility and susceptibility to bactericidal activity, we prepared murine immunoglobulin G2a anti-NspA monoclonal antibodies (MAbs) and evaluated their functional activity against 10 genetically diverseN. meningitidisserogroup B strains. By colony Western blot, all 10 strains expressed NspA as detected by one or more MAbs. By flow cytometry, two MAbs were found to bind to the bacterial surface of 6 of the 10 strains. In addition, two strains showed variable NspA surface accessibility for the MAbs despite being uniformly positive for NspA expression by colony Western blotting. Only 4 of the 10 strains were susceptible to anti-NspA complement-mediated bacteriolysis. Passively administered MAb protected infant rats from developing bacteremia after challenge withN. meningitidisserogroup B strain 8047 (surface binding positive, susceptible to anti-NspA bacteriolysis), was poorly protective against strain BZ232 (surface binding variable, resistant to bacteriolysis), and did not protect against strain M986 (surface binding negative, resistant to bacteriolysis). Finally, NspA does not appear to be critical for causing bacteremia, as an NspA knockout from strain 8047 was highly virulent in infant rats. Taken together, these findings suggest that an NspA-based vaccine will need to incorporate additional antigens to elicit broad protection againstN. meningitidisserogroup B.
Pulmonary and Systemic Host Response toStreptococcus pneumoniaeandKlebsiella pneumoniaeBacteremia in Normal and Immunosuppressed Mice
Authors: Wang Erjian , Ouellet Nathalie , Simard Marie , Fillion Isabelle , Bergeron Yves , Beauchamp Denis , Bergeron Michel G. 
Published: July 2002

ABSTRACTMortality related to bacteremic pneumonia remains high, and the role of sepsis in inflammation, pulmonary injury, and death remains unclear, mostly in leukopenic states. In the present study, the microbiology, histopathology, and host response toStreptococcus pneumoniaeandKlebsiella pneumoniaeinfection were determined in an experimental model of bacteremia in immunocompetent and leukopenic mice. Leukocyte depletion by cyclophosphamide did not impair the early clearance of pneumococci from blood but facilitated growth in lungs. By contrast, klebsiellae rapidly grew in blood of leukopenic mice. These observations suggest that tissue-based phagocytes and circulating leukocytes, respectively, play prominent roles inS. pneumoniaeandK. pneumoniaeeradication. The kinetics of leukocyte recruitment in lungs duringS. pneumoniaebacteremia suggested early strong inflammation in immunocompetent mice that is associated with tumor necrosis factor alpha release and histological disorders, including cell debris and surfactant in alveolar spaces. Leukocyte depletion further stimulated pulmonary capillary leakage both inS. pneumoniaeandK. pneumoniaebacteremia, which seemed attributable to bacterial virulence factors. Nitric oxide production did not differ significantly among groups. Leukopenia and low platelet counts characterized the late stage of bacteremia for both strains, but onlyK. pneumoniaealtered renal function. Understanding the pathogenesis of bacteremia will help establish beneficial therapies for both sepsis and pneumonia.
Dual Functions of
Streptococcus salivarius
Urease
Authors: Chen Yi-Ywan M. , Weaver Cheryl A. , Burne Robert A. 
Published: July 2002

ABSTRACT

A urease-deficient derivative of
Streptococcus salivarius
57.I was constructed by allelic exchange at the
ureC
locus. The wild-type strain was protected against acid killing through hydrolysis of physiologically relevant concentrations of urea, whereas the mutant was not. Also,
S. salivarius
could use urea as a source of nitrogen for growth exclusively through a urease-dependent pathway.
Genes for the Type IV Secretion System in an Intracellular Symbiont,Wolbachia, a Causative Agent of Various Sexual Alterations in Arthropods
Authors: Masui Shinji , Sasaki Tetsuhiko , Ishikawa Hajime 
Published: July 2002

ABSTRACTWolbachiaspecies are intracellular bacteria known to cause reproductive abnormalities in their hosts. In this study, we identifiedWolbachiagenes encoding homologs to the type IV secretion system by which many pathogenic bacteria secrete macromolecules. The genes identified encoded most of the essential components of the secretion system and were cotranscribed as an operon.
Hexokinase Regulates Kinetics of Glucose Transport and Expression of Genes Encoding Hexose Transporters in
Saccharomyces cerevisiae
Authors: Petit Thomas , Diderich Jasper A. , Kruckeberg Arthur L. , Gancedo Carlos , Van Dam Karel 
Published: July 2002

ABSTRACT

Glucose transport kinetics and mRNA levels of different glucose transporters were determined in
Saccharomyces cerevisiae
strains expressing different sugar kinases. During exponential growth on glucose, a
hxk2
null strain exhibited high-affinity hexose transport associated with an elevated transcription of the genes
HXT2
and
HXT7
, encoding high-affinity transporters, and a diminished expression of the
HXT1
and
HXT3
genes, encoding low-affinity transporters. Deletion of
HXT7
revealed that the high-affinity component is mostly due to
HXT7
; however, a previously unidentified very-high-affinity component (

K
m

= 0.19 mM) appeared to be due to other factors. Expression of genes encoding hexokinases from
Schizosaccharomyces pombe
or
Yarrowia lipolytica
in a
hxk1 hxk2 glk1
strain prevented derepression of the high-affinity transport system at high concentrations of glucose.
Mutational Analysis of Differences in Thermostability between Histones from Mesophilic and Hyperthermophilic Archaea
Authors: Li Wen-Tyng , Shriver John W. , Reeve John N. 
Published: July 2002

ABSTRACT

Amino acid residues responsible for the large difference in thermostability between HMfB and HFoB, archaeal histones from the hyperthermophile
Methanothermus fervidus
and the mesophile
Methanobacterium formicicum
, respectively, have been identified by site-specific mutagenesis. The thermal denaturation of ∼70 archaeal histone variants has been monitored by circular dichroism, and the data generated were fit to a two-state unfolding model (dimer→two random coil monomers) to obtain a standard-state (1M) melting temperature for each variant dimer. The results of single-, double-, and triple-residue substitutions reveal that the much higher stability of rHMfB dimers, relative to rHFoB dimers, is conferred predominantly by improved intermolecular hydrophobic interactions near the center of the histone dimer core and by additional favorable ion pairs on the dimer surface.