bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chronotropic and pressor effects of water ingestion at rest and in response to incremental dynamic exercise
Authors: Mendonca Goncalo V. , Teixeira Micael S. , Heffernan Kevin S. , Fernhall Bo 
Published: March 2013

New Findings
What is the central question of this study?The effects of water ingestion on the chronotropic response to dynamic exercise, performed below and above the ventilatory threshold, have not been previously explored.
What is the main finding and its importance?Drinking 500 ml of water before exercise reduces the chronotropic response to submaximal exercise performed below and above the ventilatory threshold, but not at maximal exercise intensities.
Ingestion of water attenuates the chronotropic response to submaximal exercise. However, it is not known whether this effect is equally manifested during dynamic exercise below and above the ventilatory threshold (VT). We explored the effects of water ingestion on the heart rate response to an incremental cycle‐ergometer protocol. In a randomized fashion, 19 healthy adults (10 men and nine women, age 20.9 ± 1.8 years) ingested 50 and 500 ml of water before completing a cycle‐ergometer protocol on two separate days. The heart rate and oxygen uptake () responses to water ingestion were analysed both at rest and during exercise performed below and above the VT. The effects of water intake on brachial blood pressure were measured only at rest. Resting mean arterial pressure increased and resting heart rate decreased, but only after 500 ml of water (P < 0.05). Compared with that seen after 50 ml of water, the 500 ml volume elicited an overall decrease in submaximal heart rate (P < 0.05). In contrast, drinking 500 ml of water did not affect submaximal . The participants’ maximal heart rate, maximal and VT were similar between conditions. Our results therefore indicate that, owing to its effects on submaximal heart rate over a broad spectrum of intensities, the drinking of water should be recognized as a potential confounder in cardiovascular exercise studies. However, by showing no differences between conditions for submaximal , they also suggest that the magnitude of heart rate reduction after drinking 500 ml of water may be of minimal physiological significance for exercise cardiorespiratory capacity.
More than Skew: Asymmetric Wave Propagation in a Reaction-Diffusion-Convection System
Authors: Flach Edward H. , Norbury John , Schnell Santiago 
Published: March 2013

Convection-induced instability in reaction-diffusion systems produces complicated patterns of oscillations behind propagating wavefronts. We transform the system twice: into lambda-omega form, then into polar variables. We find analytical estimates for the wavefront speed which we confirm numerically.Our previous work examined a simpler system [E. H. Flach, S. Schnell, and J. Norbury, Phys. Rev. E 76, 036216 (2007)]; the onset of instability is qualitatively different В in numerical solutions of this system. We modify our estimates and connect the two different behaviours. Our estimate explains how the Turing instability fits with pattern found in reaction-diffusion-convection systems. Our results can have important applications to the pattern formation analysis of biological systems.
Community Microrespirometry and Molecular Analyses Reveal a Diverse Energy Economy in Great Boiling Spring and Sandy's Spring West in the U.S. Great Basin
Authors: Murphy Caitlin N. , Dodsworth Jeremy A. , Babbitt Aaron B. , Hedlund Brian P. 
Published: March 2013

ABSTRACT

Microrespirometry showed that several organic and inorganic electron donors stimulated oxygen consumption in two ∼80°C springs. Sediment and planktonic communities were structurally and functionally distinct, and quantitative PCR revealed catabolically distinct subpopulations of
Thermocrinis
. This study suggests that a variety of chemolithotrophic metabolisms operate simultaneously in these springs.
Improving Escherichia coli FucO for Furfural Tolerance by Saturation Mutagenesis of Individual Amino Acid Positions
Authors: Zheng Huabao , Wang Xuan , Yomano Lorraine P. , Geddes Ryan D. , Shanmugam Keelnatham T. , Ingram Lonnie O. 
Published: March 2013

ABSTRACT

Furfural is an inhibitory side product formed during the depolymerization of hemicellulose with mineral acids. In
Escherichia coli
, furfural tolerance can be increased by expressing the native
fucO
gene (encoding lactaldehyde oxidoreductase). This enzyme also catalyzes the NADH-dependent reduction of furfural to the less toxic alcohol. Saturation mutagenesis was combined with growth-based selection to isolate a mutated form of
fucO
that confers increased furfural tolerance. The mutation responsible, L7F, is located within the interfacial region of FucO homodimers, replacing the most abundant codon for leucine with the most abundant codon for phenylalanine. Plasmid expression of the mutant gene increased FucO activity by more than 10-fold compared to the wild-type
fucO
gene and doubled the rate of furfural metabolism during fermentation. No inclusion bodies were evident with either the native or the mutated gene. mRNA abundance for the wild-type and mutant
fucO
genes differed by less than 2-fold. The

K
m

(furfural) for the mutant enzyme was 3-fold lower than that for the native enzyme, increasing efficiency at low substrate concentrations. The L7F mutation is located near the FucO N terminus, within the ribosomal binding region associated with translational initiation. Free-energy calculations for mRNA folding in this region (nucleotides −7 to +37) were weak for the native gene (−4.1 kcal mol
−1
) but weaker still for the
fucO
mutant (−1.0 to −0.1 kcal mol
−1
). The beneficial L7F mutation in FucO is proposed to increase furfural tolerance by improving gene expression and increasing enzyme effectiveness at low substrate levels.
Microbe-Dependent and Nonspecific Effects of Procedures To Eliminate the Resident Microbiota from Drosophila melanogaster
Authors: Ridley Emma V. , Wong Adam C. N. , Douglas Angela E. 
Published: March 2013

ABSTRACTComparisons of animals bearing and lacking microorganisms can offer valuable insight into the interactions between animal hosts and their resident microbiota. Most hosts are naturally infected, and therefore, these comparisons require specific procedures (e.g., antibiotic treatment or physical exclusion of microorganisms) to disrupt the microbiota, but the potential for confounding nonspecific effects of the procedure on the traits of the host exists. Microbe-dependent and nonspecific effects can be discriminated by using multiple procedures: microbe-dependent effects are evident in hosts made microbe free by different procedures, but nonspecific effects are unique to individual procedures. As a demonstration, two procedures, oral administration of chlortetracycline (50 μg ml−1diet) and microbiota removal by egg dechorionation, were applied toDrosophila melanogasterin a 2-by-2 factorial design. Microorganisms were undetectable in flies from dechorionated eggs and reduced by >99% in chlortetracycline-treated flies.Drosophilaflies subjected to both protocols displayed an extended preadult development time, suggesting that the microbiota promotes the development rate. Female chlortetracycline-treated flies, whether from untreated or dechorionated eggs, displayed reduced protein content and egg fecundity, which could be attributed to the nonspecific effect of the antibiotic. We recommend that procedures used to disrupt the microbiota of animals should be selected, following systematic analysis of alternative mechanistically distinct procedures, on the basis of two criteria: those that achieve the greatest reduction (ideally, elimination) of the microbiota and those that achieve minimal nonspecific effects.
High-Throughput Sequencing and Metagenomics: Moving Forward in the Culture-Independent Analysis of Food Microbial Ecology
Authors: Ercolini Danilo 
Published: March 2013

ABSTRACT
Following recent trends in environmental microbiology, food microbiology has benefited from the advances in molecular biology and adopted novel strategies to detect, identify, and monitor microbes in food. An in-depth study of the microbial diversity in food can now be achieved by using high-throughput sequencing (HTS) approaches after direct nucleic acid extraction from the sample to be studied. In this review, the workflow of applying culture-independent HTS to food matrices is described. The current scenario and future perspectives of HTS uses to study food microbiota are presented, and the decision-making process leading to the best choice of working conditions to fulfill the specific needs of food research is described.
Persistence of Vibrio parahaemolyticus in the Pacific Oyster, Crassostrea gigas, Is a Multifactorial Process Involving Pili and Flagella but Not Type III Secretion Systems or Phase Variation
Authors: Aagesen Alisha M. , Phuvasate Sureerat , Su Yi-Cheng , Häse Claudia C. 
Published: March 2013

ABSTRACT

Vibrio parahaemolyticus
can resist oyster depuration, suggesting that it possesses specific factors for persistence. We show that type I pili, type IV pili, and both flagellar systems contribute to
V. parahaemolyticus
persistence in Pacific oysters whereas type III secretion systems and phase variation do not.
Deletion of
FPS1
, Encoding Aquaglyceroporin Fps1p, Improves Xylose Fermentation by Engineered Saccharomyces cerevisiae
Authors: Wei Na , Xu Haiqing , Kim Soo Rin , Jin Yong-Su 
Published: March 2013

ABSTRACT

Accumulation of xylitol in xylose fermentation with engineered
Saccharomyces cerevisiae
presents a major problem that hampers economically feasible production of biofuels from cellulosic plant biomass. In particular, substantial production of xylitol due to unbalanced redox cofactor usage by xylose reductase (XR) and xylitol dehydrogenase (XDH) leads to low yields of ethanol. While previous research focused on manipulating intracellular enzymatic reactions to improve xylose metabolism, this study demonstrated a new strategy to reduce xylitol formation and increase carbon flux toward target products by controlling the process of xylitol secretion. Using xylitol-producing
S. cerevisiae
strains expressing XR only, we determined the role of aquaglyceroporin Fps1p in xylitol export by characterizing extracellular and intracellular xylitol. In addition, when
FPS1
was deleted in a poorly xylose-fermenting strain with unbalanced XR and XDH activities, the xylitol yield was decreased by 71% and the ethanol yield was substantially increased by nearly four times. Experiments with our optimized xylose-fermenting strain also showed that
FPS1
deletion reduced xylitol production by 21% to 30% and increased ethanol yields by 3% to 10% under various fermentation conditions. Deletion of
FPS1
decreased the xylose consumption rate under anaerobic conditions, but the effect was not significant in fermentation at high cell density. Deletion of
FPS1
resulted in higher intracellular xylitol concentrations but did not significantly change the intracellular NAD
+
/NADH ratio in xylose-fermenting strains. The results demonstrate that Fps1p is involved in xylitol export in
S. cerevisiae
and present a new gene deletion target,
FPS1
, and a mechanism different from those previously reported to engineer yeast for improved xylose fermentation.
Characterization of Helicobacter pylori Bacteriophage KHP30
Authors: Uchiyama Jumpei , Takeuchi Hiroaki , Kato Shin-ichiro , Gamoh Keiji , Takemura-Uchiyama Iyo , Ujihara Takako , Daibata Masanori , Matsuzaki Shigenobu 
Published: March 2013

ABSTRACTHelicobacter pyloriinhabits the stomach mucosa and is a causative agent of stomach ulcer and cancer. In general, bacteriophages (phages) are strongly associated with bacterial evolution, including the development of pathogenicity. Several tailed phages have so far been reported inH. pylori. We have isolated anH. pyloriphage, KHP30, and reported its genomic sequence. In this study, we examined the biological characteristics of phage KHP30. Phage KHP30 was found to be a spherical lipid-containing phage with a diameter of ca. 69 nm. Interestingly, it was stable from pH 2.5 to pH 10, suggesting that it is adapted to the highly acidic environment of the human stomach. Phage KHP30 multiplied on 63.6% of clinicalH. pyloriisolates. The latent period was ca. 140 min, shorter than the doubling time ofH. pylori(ca. 180 min). The burst size was ca. 13, which was smaller than the burst sizes of other known tailed or spherical phages. Phage KHP30 seemed to be maintained as an episome inH. pyloristrain NY43 cells, despite a predicted integrase gene in the KHP30 genomic sequence. Seven possible virion proteins of phage KHP30 were analyzed using N-terminal protein sequencing and mass spectrometry, and their genes were found to be located on its genomic DNA. The genomic organization of phage KHP30 differed from the genomic organizations in the known spherical phage familiesCorticoviridaeandTectiviridae. This evidence suggests that phage KHP30 is a new type of spherical phage that cannot be classified in any existing virus category.
Cooccurrence of Free-Living Amoebae and Nontuberculous Mycobacteria in Hospital Water Networks, and Preferential Growth of Mycobacterium avium in Acanthamoeba lenticulata
Authors: Ovrutsky Alida R. , Chan Edward D. , Kartalija Marinka , Bai Xiyuan , Jackson Mary , Gibbs Sara , Falkinham Joseph O. , Iseman Michael D. , Reynolds Paul R. , McDonnell Gerald , Thomas Vincent 
Published: March 2013

ABSTRACT

The incidence of lung and other diseases due to nontuberculous mycobacteria (NTM) is increasing. NTM sources include potable water, especially in households where NTM populate pipes, taps, and showerheads. NTM share habitats with free-living amoebae (FLA) and can grow in FLA as parasites or as endosymbionts. FLA containing NTM may form cysts that protect mycobacteria from disinfectants and antibiotics. We first assessed the presence of FLA and NTM in water and biofilm samples collected from a hospital, confirming the high prevalence of NTM and FLA in potable water systems, particularly in biofilms.
Acanthamoeba
spp. (genotype T4) were mainly recovered (8/17), followed by
Hartmannella vermiformis
(7/17) as well as one isolate closely related to the genus
Flamella
and one isolate only distantly related to previously described species. Concerning mycobacteria,
Mycobacterium gordonae
was the most frequently found isolate (9/17), followed by
Mycobacterium peregrinum
(4/17),
Mycobacterium chelonae
(2/17),
Mycobacterium mucogenicum
(1/17), and
Mycobacterium avium
(1/17). The propensity of
Mycobacterium avium
hospital isolate H87 and
M. avium
collection strain 104 to survive and replicate within various FLA was also evaluated, demonstrating survival of both strains in all amoebal species tested but high replication rates only in
Acanthamoeba lenticulata
. As
A. lenticulata
was frequently recovered from environmental samples, including drinking water samples, these results could have important consequences for the ecology of
M. avium
in drinking water networks and the epidemiology of disease due to this species.
Genetic Evidence for a Molybdopterin-Containing Tellurate Reductase
Authors: Theisen Joanne , Zylstra Gerben J. , Yee Nathan 
Published: March 2013

ABSTRACT

The genetic identity and cofactor composition of the bacterial tellurate reductase are currently unknown. In this study, we examined the requirement of molybdopterin biosynthesis and molybdate transporter genes for tellurate reduction in
Escherichia coli
K-12. The results show that mutants deleted of the
moaA
,
moaB
,
moaE
, or
mog
gene in the molybdopterin biosynthesis pathway lost the ability to reduce tellurate. Deletion of the
modB
or
modC
gene in the molybdate transport pathway also resulted in complete loss of tellurate reduction activity. Genetic complementation by the wild-type sequences restored tellurate reduction activity in the mutant strains. These findings provide genetic evidence that tellurate reduction in
E. coli
involves a molybdoenzyme.
Coordination of K
+
Transporters in Neurospora: TRK1 Is Scarce and Constitutive, while HAK1 Is Abundant and Highly Regulated
Authors: Rivetta Alberto , Allen Kenneth E. , Slayman Carolyn W. , Slayman Clifford L. 
Published: March 2013

ABSTRACT

Fungi, plants, and bacteria accumulate potassium via two distinct molecular machines not directly coupled to ATP hydrolysis. The first, designated TRK, HKT, or KTR, has eight transmembrane helices and is folded like known potassium channels, while the second, designated HAK, KT, or KUP, has 12 transmembrane helices and resembles MFS class proteins. One of each type functions in the model organism
Neurospora crassa
, where both are readily accessible for biochemical, genetic, and electrophysiological characterization. We have now determined the operating balance between Trk1p and Hak1p under several important conditions, including potassium limitation and carbon starvation. Growth measurements, epitope tagging, and quantitative Western blotting have shown the gene
HAK1
to be much more highly regulated than is
TRK1
. This conclusion follows from three experimental results: (i) Trk1p is expressed constitutively but at low levels, and it is barely sensitive to extracellular [K
+
] and/or the coexpression of
HAK1
; (ii) Hak1p is abundant but is markedly depressed by elevated extracellular concentrations of K
+
and by coexpression of
TRK1
; and (iii) Carbon starvation slowly enhances Hak1p expression and depresses Trk1p expression, yielding steady-state Hak1p:Trk1p ratios of ∼500:1,
viz.
, 10- to 50-fold larger than that in K
+
- and carbon-replete cells. Additionally, it appears that both potassium transporters can adjust kinetically to sustained low-K
+
stress by means of progressively increasing transporter affinity for extracellular K
+
. The underlying observations are (iv) that K
+
influx via Trk1p remains nearly constant at ∼9 mM/h when extracellular K
+
is progressively depleted below 0.05 mM and (v) that K
+
influx via Hak1p remains at ∼3 mM/h when extracellular K
+
is depleted below 0.1 mM.
Does Candida albicans Als5p Amyloid Play a Role in Commensalism in Caenorhabditis elegans?
Authors: Bois Michael , Singh Sean , Samlalsingh Alyssa , Lipke Peter N. , Garcia Melissa C. 
Published: March 2013

ABSTRACT

Candida albicans
, a dimorphic fungus and an opportunistic pathogen, possesses a myriad of adherence factors, including members of the agglutinin-like sequence (Als) family of mannoproteins. The adhesin Als5p mediates adhesion to many substrates and is upregulated during commensal interactions but is downregulated during active
C. albicans
infections. An amyloid-forming core sequence at residues 325 to 331 is important for Als5p function, because a single-amino-acid substitution at position 326 (V326N) greatly reduces Als5p-mediated adherence. We evaluated the role of Als5p in host-microbe interactions by using
Caenorhabditis elegans
nematodes as a host model and feeding them
Saccharomyces cerevisiae
expressing Als5p on the surface. Als5p-expressing yeast had 8.5- and 3.5-fold-increased intestinal accumulation rates compared to Als5p-nonexpressing
S. cerevisiae
or yeast expressing amyloid-deficient Als5p
V326N
, respectively. Surprisingly, this accumulation delayed
S. cerevisiae
-induced killing of
C. elegans.
The median survival time was nearly twice as long as that of nematodes fed nonexpressing or non-amyloid-forming Als5p
V326N
-expressing
S. cerevisiae
. Treatment with the amyloid-inhibiting dye Congo red or repression of Als5p expression abrogated the protective effect of Als5p. Furthermore, Als5p had no effect on oocyte quantity or quality, since nematodes fed either empty vector (EV)- or Als5p
V326N
-expressing
S. cerevisiae
had similar egg-laying and egg-hatching rates. This study is the first, to our knowledge, to show that expression of an amyloid-forming protein can attenuate pathogenicity in
C. elegans
.
Nuclear Pores and Perinuclear Expression Sites ofvarand Ribosomal DNA Genes Correspond to Physically Distinct Regions in Plasmodium falciparum
Authors: Guizetti Julien , Martins Rafael Miyazawa , Guadagnini Stéphanie , Claes Aurélie , Scherf Artur 
Published: March 2013

ABSTRACTThe human malaria parasitePlasmodium falciparummodifies the erythrocyte it infects by exporting variant proteins to the host cell surface. Thevargene family that codes for a large, variant adhesive surface protein calledP. falciparumerythrocyte membrane protein 1 (PfEMP1) plays a particular role in this process, which is linked to pathogenesis and immune evasion. A single member of this gene family is highly transcribed while the other 59 members remain silenced. Importantly,vargene transcription occurs at a spatially restricted, but yet undefined, perinuclear site that is distinct from repressedvargene clusters. To advance our understanding of monoallelic expression, we investigated whether nuclear pores associate with thevargene expression site. To this end, we studied the nuclear pore organization during the asexual blood stage using a specific antibody directed against a subunit of the nuclear pore,P. falciparumNup116 (PfNup116). Ring and schizont stage parasites showed highly polarized nuclear pore foci, whereas in trophozoite stage nuclear pores redistributed over the entire nuclear surface. Colocalization studies ofvartranscripts and anti-PfNup116 antibodies showed clear dissociation between nuclear pores and thevargene expression site in ring stage. Similar results were obtained for another differentially transcribed perinuclear gene family, the ribosomal DNA units. Furthermore, we show that in the poised state, thevargene locus is not physically linked to nuclear pores. Our results indicate thatP. falciparumdoes form compartments of high transcriptional activity at the nuclear periphery which are, unlike the case in yeast, devoid of nuclear pores.
Cch1 and Mid1 Are Functionally Required for Vegetative Growth under Low-Calcium Conditions in the Phytopathogenic Ascomycete Botrytis cinerea
Authors: Harren Karin , Tudzynski Bettina 
Published: March 2013

ABSTRACT

In the filamentous phytopathogen
Botrytis cinerea
, the Ca
2+
/calcineurin signaling cascade has been shown to play an important role in fungal growth, differentiation, and virulence. This study deals with the functional characterization of two components of this pathway, the putative calcium channel proteins Cch1 and Mid1. The
cch1
and
mid1
genes were deleted, and single and double knockout mutants were analyzed during different stages of the fungal life cycle. Our data indicate that Cch1 and Mid1 are functionally required for vegetative growth under conditions of low extracellular calcium, since the growth of both deletion mutants is strongly impaired when they are exposed to the Ca
2+
-chelating agents EGTA and 1,2-bis(
o
-aminophenoxy)ethane-
N
,
N
,
N
′,
N
′-tetraacetic acid (BAPTA). The impact of external Ca
2+
was investigated by supplementing with CaCl
2
and the ionophore A23187, both of which resulted in elevated growth for all mutants. However, deletion of either gene had no impact on germination, sporulation, hyphal morphology, or virulence. By use of the aequorin reporter system to measure intracellular calcium levels, no differences between the mutant strains and the wild type were obtained. Localization studies revealed a subcellular distribution of the Mid1–green fluorescent protein (GFP) fusion protein in network-like filaments, probably the endoplasmic reticulum (ER) membranes, indicating that Mid1 is not a plasma membrane-located calcium channel in
B. cinerea
.