bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Furfural on the Respiratory Metabolism of
Saccharomyces cerevisiae
in Glucose-Limited Chemostats
Authors: Sárvári Horváth Ilona , Franzén Carl Johan , Taherzadeh Mohammad J. , Niklasson Claes , Lidén Gunnar 
Published: July 2003

ABSTRACT

Effects of furfural on the aerobic metabolism of the yeast
Saccharomyces cerevisiae
were studied by performing chemostat experiments, and the kinetics of furfural conversion was analyzed by performing dynamic experiments. Furfural, an important inhibitor present in lignocellulosic hydrolysates, was shown to have an inhibitory effect on yeast cells growing respiratively which was much greater than the inhibitory effect previously observed for anaerobically growing yeast cells. The residual furfural concentration in the bioreactor was close to zero at all steady states obtained, and it was found that furfural was exclusively converted to furoic acid during respiratory growth. A metabolic flux analysis showed that furfural affected fluxes involved in energy metabolism. There was a 50% increase in the specific respiratory activity at the highest steady-state furfural conversion rate. Higher furfural conversion rates, obtained during pulse additions of furfural, resulted in respirofermentative metabolism, a decrease in the biomass yield, and formation of furfuryl alcohol in addition to furoic acid. Under anaerobic conditions, reduction of furfural partially replaced glycerol formation as a way to regenerate NAD
+
. At concentrations above the inlet concentration of furfural, which resulted in complete replacement of glycerol formation by furfuryl alcohol production, washout occurred. Similarly, when the maximum rate of oxidative conversion of furfural to furoic acid was exceeded aerobically, washout occurred. Thus, during both aerobic growth and anaerobic growth, the ability to tolerate furfural appears to be directly coupled to the ability to convert furfural to less inhibitory compounds.
Plasmid Introduction in Metal-Stressed, Subsurface-Derived Microcosms: Plasmid Fate and Community Response
Authors: Smets Barth F. , Morrow Jayne B. , Arango Pinedo Catalina 
Published: July 2003

ABSTRACT

The nonconjugal IncQ plasmids pMOL187 and pMOL222, which contain the metal resistance-encoding genes
czc
and
ncc
, were introduced by using
Escherichia coli
as a transitory delivery strain into microcosms containing subsurface-derived parent materials. The microcosms were semicontinuously dosed with an artificial groundwater to set a low-carbon flux and a target metal stress (0, 10, 100, and 1,000 μM CdCl
2
), permitting long-term community monitoring. The broad-host-range IncPα plasmid RP4 was also transitorily introduced into a subset of microcosms. No novel community phenotype was detected after plasmid delivery, due to the high background resistances to Cd and Ni. At fixed Cd doses, however, small but consistent increases in Cd
r
or Ni
r
density were measured due to the introduction of a single pMOL plasmid, and this effect was enhanced by the joint introduction of RP4; the effects were most significant at the highest Cd doses. The pMOL plasmids introduced could, however, be monitored via
czc-
and
ncc
-targeted infinite-dilution PCR (ID-PCR) methods, because these genes were absent from the indigenous community: long-term presence of
czc
(after 14 or 27 weeks) was contingent on the joint introduction of RP4, although RP4 cointroduction was not yet required to ensure retention of
ncc
after 8 weeks. Plasmids isolated from Ni
r
transconjugants further confirmed the presence and retention of a pMOL222-sized plasmid. ID-PCR targeting the RP4-specific
trafA
gene revealed retention of RP4 for at least 8 weeks. Our findings confirm plasmid transfer and long-term retention in low-carbon-flux, metal-stressed subsurface communities but indicate that the subsurface community examined has limited mobilization potential for the IncQ plasmids employed.
Activity of Free and Clay-Bound Insecticidal Proteins from
Bacillus thuringiensis
subsp.
israelensis
against the Mosquito
Culex pipiens
Authors: Lee LanNa , Saxena Deepak , Stotzky G. 
Published: July 2003

ABSTRACT

Bacillus thuringiensis
subsp.
israelensis
produces parasporal insecticidal crystal proteins (ICPs) that have larvicidal activity against some members of the order Diptera, such as blackflies and mosquitoes. Hydrolysis of the ICPs in the larval gut results in four major proteins with a molecular mass of 27, 65, 128, and 135 kDa. Toxicity is caused by synergistic interaction between the 25-kDa protein (proteolytic product of the 27-kDa protein) and one or more of the higher-molecular-mass proteins. Equilibrium adsorption of the proteins on the clay minerals montmorillonite and kaolinite, which are homoionic to various cations, was rapid (<30 min for maximal adsorption), increased with protein concentration and then reached a plateau (68 to 96% of the proteins was adsorbed), was significantly lower on kaolinite than on montmorillonite, and was not significantly affected by the valence of the cation to which the clays were homoionic. Binding of the toxins decreased as the pH was increased from 6 to 11, and there was 35 to 66% more binding in phosphate buffer at pH 6 than in distilled water at pH 6 or 7.2. Only 2 to 12% of the adsorbed proteins was desorbed by two washes with water; additional washings desorbed no more toxins, indicating that they were tightly bound. Formation of clay-toxin complexes did not alter the structure of the proteins, as indicated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the equilibrium supernatants and desorption washes and by dot blot enzyme-linked immunosorbent assay of the complexes, which was confirmed by enhanced chemiluminescence Western blot analysis. Free and clay-bound toxins resulted in 85 to 100% mortality of the mosquito
Culex pipiens
. Persistence of the bound toxins in nonsterile water after 45 days was significantly greater (mortality of 63% ± 12.7%) than that of the free toxins (mortality of 25% ± 12.5%).
Thermal Inactivation of Susceptible and Multiantimicrobial-Resistant
Salmonella
Strains Grown in the Absence or Presence of Glucose
Authors: Bacon R. T. , Ransom J. R. , Sofos J. N. , Kendall P. A. , Belk K. E. , Smith G. C. 
Published: July 2003

ABSTRACT

The heat resistance of susceptible and multiantimicrobial-resistant
Salmonella
strains grown to stationary phase in glucose-free tryptic soy broth supplemented with 0.6% yeast extract (TSBYE−G; nonadapted), in regular (0.25% glucose) TSBYE, or in TSBYE−G with 1.00% added glucose (TSBYE+G; acid adapted) was determined at 55, 57, 59, and 61°C. Cultures were heated in sterile 0.1% buffered peptone water (50 μl) in heat-sealed capillary tubes immersed in a thermostatically controlled circulating-water bath. Decimal reduction times (
D
values) were calculated from survival curves having
r
2
values of >0.90 as a means of comparing thermal tolerance among variables.
D
59°C
values increased (
P
< 0.05) from 0.50 to 0.58 to 0.66 min for TSBYE−G, TSBYE, and TSBYE+G cultures, respectively.
D
61°C
values of antimicrobial-susceptible
Salmonella
strains increased (
P
< 0.05) from 0.14 to 0.19 as the glucose concentration increased from 0.00 to 1.00%, respectively, while
D
61°C
values of multiantimicrobial-resistant
Salmonella
strains did not differ (
P
> 0.05) between TSBYE−G and TSBYE+G cultures. When averaged across glucose levels and temperatures, there were no differences (
P
> 0.05) between the
D
values of susceptible and multiantimicrobial-resistant inocula. Collectively,
D
values ranged from 4.23 to 5.39, 1.47 to 1.81, 0.50 to 0.66, and 0.16 to 0.20 min for
Salmonella
strains inactivated at 55, 57, 59, and 61°C, respectively.

z
D

values were 1.20, 1.48, and 1.49°C for
Salmonella
strains grown in TSBYE+G, TSBYE, and TSBYE−G, respectively, while the corresponding activation energies of inactivation were 497, 493, and 494 kJ/mol. Study results suggested a cross-protective effect of acid adaptation on thermal inactivation but no association between antimicrobial susceptibility and the ability of salmonellae to survive heat stress.
Contrasting Patterns of Phytoplankton Community Pigment Composition in Two Salt Marsh Estuaries in Southeastern United States
Authors: Noble Peter A. , Tymowski Raphael G. , Fletcher Madilyn , Morris James T. , Lewitus Alan J. 
Published: July 2003

ABSTRACTPhytoplankton community pigment composition and water quality were measured seasonally along salinity gradients in two minimally urbanized salt marsh estuaries in South Carolina in order to examine their spatial and temporal distributions. The North Inlet estuary has a relatively small watershed with minimal fresh water input, while the Ashepoo, Combahee, and Edisto (ACE) Basin is characterized by a relatively greater influence of riverine drainage. Sampling stations were located in regions of the estuaries experiencing frequent diurnal tidal mixing and had similar salinity and temperature regimens. Phytoplankton community pigment composition was assessed by using high-performance liquid chromatography (HPLC) and multivariate statistical analyses. Shannon diversity index, principal-component, and cluster analyses revealed that phytoplankton community pigments in both estuaries were seasonally variable, with similar diversities but different compositions. The temporal pigment patterns indicated that there was a relatively weak correlation between the pigments in ACE Basin and the relative persistence of photopigment groups in North Inlet. The differences were presumably a consequence of the unpredictability and relatively greater influence of river discharge in the ACE Basin, in contrast to the greater environmental predictability of the more tidally influenced North Inlet. Furthermore, the timing, magnitude, and pigment composition of the annual phytoplankton bloom were different in the two estuaries. The bloom properties in North Inlet reflected the predominance of autochthonous ecological control (e.g., regenerated nutrients, grazing), and those in ACE Basin suggested that there was greater influence of allochthonous environmental factors (e.g., nutrient loading, changes in turbidity). These interestuarine differences in phytoplankton community structure and control provide insight into the organization of phytoplankton in estuaries.
A Modified
Saccharomyces cerevisiae
Strain That Consumes
l
-Arabinose and Produces Ethanol
Authors: Becker Jessica , Boles Eckhard 
Published: July 2003

ABSTRACT

Metabolic engineering is a powerful method to improve, redirect, or generate new metabolic reactions or whole pathways in microorganisms. Here we describe the engineering of a
Saccharomyces cerevisiae
strain able to utilize the pentose sugar
l
-arabinose for growth and to ferment it to ethanol. Expanding the substrate fermentation range of
S. cerevisiae
to include pentoses is important for the utilization of this yeast in economically feasible biomass-to-ethanol fermentation processes. After overexpression of a bacterial
l
-arabinose utilization pathway consisting of
Bacillus subtilis
AraA and
Escherichia coli
AraB and AraD and simultaneous overexpression of the
l
-arabinose-transporting yeast galactose permease, we were able to select an
l
-arabinose-utilizing yeast strain by sequential transfer in
l
-arabinose media. Molecular analysis of this strain, including DNA microarrays, revealed that the crucial prerequisite for efficient utilization of
l
-arabinose is a lowered activity of
l
-ribulokinase. Moreover, high
l
-arabinose uptake rates and enhanced transaldolase activities favor utilization of
l
-arabinose. With a doubling time of about 7.9 h in a medium with
l
-arabinose as the sole carbon source, an ethanol production rate of 0.06 to 0.08 g of ethanol per g (dry weight) · h
−1
under oxygen-limiting conditions, and high ethanol yields, this yeast strain should be useful for efficient fermentation of hexoses and pentoses in cellulosic biomass hydrolysates.
Reductive Dehalogenation of Brominated Phenolic Compounds by Microorganisms Associated with the Marine Sponge
Aplysina aerophoba
Authors: Ahn Young-Beom , Rhee Sung-Keun , Fennell Donna E. , Kerkhof Lee J. , Hentschel Ute , Häggblom Max M. 
Published: July 2003

ABSTRACT

Marine sponges are natural sources of brominated organic compounds, including bromoindoles, bromophenols, and bromopyrroles, that may comprise up to 12% of the sponge dry weight.
Aplysina aerophoba
sponges harbor large numbers of bacteria that can amount to 40% of the biomass of the animal. We postulated that there might be mechanisms for microbially mediated degradation of these halogenated chemicals within the sponges. The capability of anaerobic microorganisms associated with the marine sponge to transform haloaromatic compounds was tested under different electron-accepting conditions (i.e., denitrifying, sulfidogenic, and methanogenic). We observed dehalogenation activity of sponge-associated microorganisms with various haloaromatics. 2-Bromo-, 3-bromo-, 4-bromo-, 2,6-dibromo-, and 2,4,6-tribromophenol, and 3,5-dibromo-4-hydroxybenzoate were reductively debrominated under methanogenic and sulfidogenic conditions with no activity observed in the presence of nitrate. Monochlorinated phenols were not transformed over a period of 1 year. Debromination of 2,4,6-tribromophenol, and 2,6-dibromophenol to 2-bromophenol was more rapid than the debromination of the monobrominated phenols. Ampicillin and chloramphenicol inhibited activity, suggesting that dehalogenation was mediated by bacteria. Characterization of the debrominating methanogenic consortia by using terminal restriction fragment length polymorphism (TRFLP) and denaturing gradient gel electrophoresis analysis indicated that different 16S ribosomal DNA (rDNA) phylotypes were enriched on the different halogenated substrates. Sponge-associated microorganisms enriched on organobromine compounds had distinct 16S rDNA TRFLP patterns and were most closely related to the δ subgroup of the proteobacteria. The presence of homologous reductive dehalogenase gene motifs in the sponge-associated microorganisms suggested that reductive dehalogenation might be coupled to dehalorespiration.
Single-Cell Protein Profiling of Wastewater Enterobacterial Communities Predicts Disinfection Efficiency
Authors: Ponniah Gomathinayagam , Chen Han , Michielutti Ronda , Salonen Nancy , Blum Paul 
Published: July 2003

ABSTRACT
The efficiency of enterobacterial disinfection is dependent largely on enterobacterial community physiology. However, the relationship between enterobacterial community physiology and wastewater processing is unclear. The purpose of this study was to investigate this relationship. The influence of wastewater treatment processes on enterobacterial community physiology was examined at the single-cell level by using culture-independent methods. Intracellular concentrations of two conserved proteins, the growth-related protein Fis and the stationary-phase protein Dps, were analyzed by epifluoresence microscopy of uncultivated cells by using enterobacterial group-specific polyclonal fluorochrome-coupled antibodies. Enterobacterial single-cell community protein profiles were distinct for different types of biological treatment. The differences were not apparent when bulk methods of protein analysis were used. Trickling filter wastewater yielded Fis-enriched communities compared to the communities in submerged aeration basin wastewater. Community differences in Fis and Dps contents were used to predict disinfection efficiency. Disinfection of community samples by heat exposure combined with cultivation in selective media confirmed that enterobacterial communities exhibited significant differences in sensitivity to disinfection. These findings provide strategies that can be used to increase treatment plant performance, reduce the enterobacterial content in municipal wastewater, and minimize the release of disinfection by-products into receiving water.
Catabolism of Arylboronic Acids by
Arthrobacter nicotinovorans
Strain PBA
Authors: Negrete-Raymond Ana C. , Weder Barbara , Wackett Lawrence P. 
Published: July 2003

ABSTRACT

Arthrobacter
sp. strain PBA metabolized phenylboronic acid to phenol. The oxygen atom in phenol was shown to be derived from the atmosphere using
18
O
2
. 1-Naphthalene-, 2-naphthalene-, 3-cyanophenyl-, 2,5-fluorophenyl-, and 3-thiophene-boronic acids were also transformed to monooxygenated products. The oxygen atom in the product was bonded to the ring carbon atom originally bearing the boronic acid substituent with all the substrates tested.
An Anthropological Odyssey
Authors: Bernardi Bernardo 
Published: July 2003

My anthropological experience may be described as a long and inspiring journey across the seas of the human condition. I have always been struck by what I call the paradox of human reality: Born to live, we are destined to die; ready to enjoy life, we must struggle to avoid discomfort and disease; conscious of individuality, we are still unavoidably bound from birth to a social group; claiming to be equal, we nevertheless differ both as individuals and groups. Whenever it seemed I had a comprehensive view of human nature, I was led to a reorienting perspective. I regret none of the various phases of my long journey. Each has contributed to the evolution of my anthropological approach to reality. The reverse is also true: My anthropological perspective has often brought changes in my life’s route. Indeed, the study of anthropology, which revealed the essence of the human condition, decisively led me to change my social and professional stations. I left the Catholic priesthood and its missionary activity, dedicating myself fully to the study of anthropology
The Three-Dimensional Structure of Peptide-MHC Complexes
Authors: Madden Dean R. 
Published: July 2003

The ability of MHC molecules to present a broad spectrum of peptide antigens for T cell recognition requires a compromise between high affinity and broad specificity. Three-dimensional atomic structures of several class I and class II MHC molecules reveal a unique structural solution to this problem: Tight binding to the peptide main chain is supplemented by more or less restrictive interactions with peptide side chains. In spite of these contacts, peptide side-chain and conformational variability ensures that the resulting peptide-MHC complex presents an antigenically unique surface to T cell receptors. Extension of this understanding to other peptide-MHC complexes, including agonist/antagonist peptides and the identification of antigenic peptides within protein sequences, however, requires a detailed analysis of the interactions that determine both peptide-MHC binding affinity and the conformations of bound peptides. While many of these interactions can be modeled by homology with known structures, their specificity can depend sensitively on subtle and long range structural effects. Structurally and immunologically important distinctions are also found between the class I and class II peptide-binding strategies. Taken together, these interactions ultimately determine the ability of an individual to respond successfully to immune challenges.
Pathogenesis and Pathophysiology of Bacterial Meningitis
Authors: Tunkel Allan R. , Scheld W. Michael 
Published: July 2003

Despite the availability of bactericidal antibiotics with potent in vitro activity against the major meningeal pathogens, the morbidity and mortality from bacterial meningitis remains unacceptably high. Animal models have proven to be extremely valuable in the study of the pathogenesis and pathophysiology of bacterial meningitis, with the hopes of providing new information that may lead to an improved outcome from this disorder. Bacterial meningitis usually begins with nasopharyngeal colonization by a new organism, followed by invasion and bacteremia. Subsequently there is central nervous system invasion, although the exact site and mechanism of meningeal invasion are unknown. The generation of an intense subarachnoids pace inflammatory response, induced by release of bacterial virulence factors and/or inflammatory cytokines, contributes to many of the pathophysiologicc onsequences of bacterial meningitis, including cerebral edema, increased intracranial pressure, and alterations of cerebral blood flow. Attenuation of this inflammatory response ( e.g. by co-administration of antiinflammatory agents) may diminish many of these pathophysiologic consequences of meningitis, and perhaps improve morbidity and mortality from this disorder
Endothelial Dysfunction in Coronary Artery Disease
Authors: Lüscher Thomas F. , Tanner Felix C. , Tschudi Marcel R. , Noll Georg 
Published: July 2003

The endothelium is a physical barrier between the blood and vascular smooth muscle, a source of enzymes activating and deactivating cardiovascular hormones and a site of production of relaxing and contracting factors. In addition, the endothelium is a source of growth inhibitors and promoters of vascular smooth muscle cells. Monoaminooxidasc deactivates catecholamines and serotonin. Angiotensin converting enzyme transforms angiotensin I into angiotensin II and breaks down bradykinin into inactive products. Nitric oxide is a potent vasodilator and inhibitor of platelet function that under most circumstances is released together with prostacyclin, which exerts similar effects. Both substances play an important protective role in the coronary circulation in that they cause continuous vasodilation and inhibition of platelet function. In addition, the endothelium is a source of contracting factors such as endothelin-1, thromboxane A2, and endoperoxides. Endothelium-derived growth inhibitors include heparin (sulfates) and transforming growth factor β1, while basic fibroblast growth factors and platelet- derived growth factor and possibly endothelin promote proliferation. Because of its strategic anatomic position, the endothelium is a primary target for injuries and cardiovascular risk factors. In particular, aging, low density lipoproteins, hypertension, diabetes, and ischemia alter endothelium function. In arterial coronary bypass grafts, the release of nitric oxide is more pronounced than in vein grafts. Alterations of endothelial function may contribute to vasospasm, thrombus formation, and vascular proliferation and in turn myocardial ischemia, all commone vents in patients with coronary artery disease.
Folic Acid and the Prevention of Birth Defects
Authors: Butterworth C. E. , Bendich Adrianne 
Published: July 2003

Thirty years ago, it was suggested that maternal intake of certain vitamins during pregnancy affected the incidence of serious fetal malformations. Subsequent research has revealed that folate (folic acid), a B vitamin, plays a crucial role in the development of the central nervous system during the early weeks of gestation, which is generally before the pregnancy is confirmed. In a significant number of embryos, an inadequate supply of folate at this time leads to a failure of the primitive neural tube to close and differentiate normally and results in neural tube birth defects (NTD). Numerous studies have confirmed the importance of an adequate intake of folate during the weeks just before and after conception. Overall, the data predict that if women consume multivitamin supplements containing folic acid during the periconceptional period, the number of children born with serious malformations (such as spina bifida and anencephaly) could be reduced by half. Although programs to increase dietary folate intake of potential mothers may be effective in reducing NTD, the only proven and practical preventive measure currently available is to take oral multivitamin supplements containing folic acid. Multivitamin supplementation has also been associated with reduced incidence of other congenital malformations. Current research is focusing on the role of micronutrients in embryogenesis, and on methods to identify prospective mothers at increased risk for bearing a child with NTD or with other major malformations shown to occur at reduced frequency with multivitamin supplementation. Of equal importance is the development of methods to communicate current knowledge as a public health measure.