bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exercise performance is regulated during repeated sprints to limit the development of peripheral fatigue beyond a critical threshold
Authors: Hureau Thomas J. , Olivier Nicolas , Millet Guillaume Y. , Meste Olivier , Blain Gregory M. 
Published: April 2014

New Findings
What is the central question of this study?
We asked whether exercise performance is regulated during all‐out repeated sprints (involving peak cycling‐specific muscle activation and limited pacing strategy) in order to restrain the total degree of peripheral fatigue development.
What is the main finding and its importance?
Our results showed that power output is adjusted during repeated sprints to limit the development of peripheral fatigue to a critical threshold, independently of the degree of pre‐existing fatigue. These findings emphasize the important role of peripheral fatigue in adjustment of power output during exercise.
We hypothesized that exercise performance is adjusted during repeated sprints in order not to surpass a critical threshold of peripheral fatigue. Twelve men randomly performed three experimental sessions on different days, i.e. one single 10 s all‐out sprint and two trials of 10 × 10 s all‐out sprints with 30 s of passive recovery in between. One trial was performed in the unfatigued state (CTRL) and one following electrically induced quadriceps muscle fatigue (FTNMES). Peripheral fatigue was quantified by comparing pre‐ with postexercise changes in potentiated quadriceps twitch force (ΔQtw‐pot) evoked by supramaximal magnetic stimulation of the femoral nerve. Central fatigue was estimated by comparing pre‐ with postexercise voluntary activation of quadriceps motor units. The root mean square (RMS) of the vastus lateralis and vastus medialis EMG normalized to maximal M‐wave amplitude (RMS.Mmax−1) was also calculated during sprints. Compared with CTRL condition, pre‐existing quadriceps muscle fatigue in FTNMES (ΔQtw‐pot = −29 ± 4%) resulted in a significant (P < 0.05) reduction in power output (−4.0 ± 0.9%) associated with a reduction in RMS.Mmax−1. However, ΔQtw‐pot postsprints decreased by 51% in both conditions, indicating that the level of peripheral fatigue was identical and independent of the degree of pre‐existing fatigue. Our findings show that power output and cycling EMG are adjusted during exercise in order to limit the development of peripheral fatigue beyond a constant threshold. We hypothesize that the contribution of peripheral fatigue to exercise limitation involves a reduction in central motor drive in addition to the impairment in muscular function.
Correlating Microbial Diversity Patterns with Geochemistry in an Extreme and Heterogeneous Environment of Mine Tailings
Authors: Liu Jun , Hua Zheng-Shuang , Chen Lin-Xing , Kuang Jia-Liang , Li Sheng-Jin , Shu Wen-Sheng , Huang Li-Nan 
Published: April 2014

ABSTRACT

Recent molecular surveys have advanced our understanding of the forces shaping the large-scale ecological distribution of microbes in Earth's extreme habitats, such as hot springs and acid mine drainage. However, few investigations have attempted dense spatial analyses of specific sites to resolve the local diversity of these extraordinary organisms and how communities are shaped by the harsh environmental conditions found there. We have applied a 16S rRNA gene-targeted 454 pyrosequencing approach to explore the phylogenetic differentiation among 90 microbial communities from a massive copper tailing impoundment generating acidic drainage and coupled these variations in community composition with geochemical parameters to reveal ecological interactions in this extreme environment. Our data showed that the overall microbial diversity estimates and relative abundances of most of the dominant lineages were significantly correlated with pH, with the simplest assemblages occurring under extremely acidic conditions and more diverse assemblages associated with neutral pHs. The consistent shifts in community composition along the pH gradient indicated that different taxa were involved in the different acidification stages of the mine tailings. Moreover, the effect of pH in shaping phylogenetic structure within specific lineages was also clearly evident, although the phylogenetic differentiations within the
Alphaproteobacteria
,
Deltaproteobacteria
, and
Firmicutes
were attributed to variations in ferric and ferrous iron concentrations. Application of the microbial assemblage prediction model further supported pH as the major factor driving community structure and demonstrated that several of the major lineages are readily predictable. Together, these results suggest that pH is primarily responsible for structuring whole communities in the extreme and heterogeneous mine tailings, although the diverse microbial taxa may respond differently to various environmental conditions.
Impact of UV and Peracetic Acid Disinfection on the Prevalence of Virulence and Antimicrobial Resistance Genes in Uropathogenic Escherichia coli in Wastewater Effluents
Authors: Biswal Basanta Kumar , Khairallah Ramzi , Bibi Kareem , Mazza Alberto , Gehr Ronald , Masson Luke , Frigon Dominic 
Published: April 2014

ABSTRACT

Wastewater discharges may increase the populations of pathogens, including
Escherichia coli
, and of antimicrobial-resistant strains in receiving waters. This study investigated the impact of UV and peracetic acid (PAA) disinfection on the prevalence of virulence and antimicrobial resistance genes in uropathogenic
Escherichia coli
(UPEC), the most abundant
E. coli
pathotype in municipal wastewaters. Laboratory disinfection experiments were conducted on wastewater treated by physicochemical, activated sludge, or biofiltration processes; 1,766
E. coli
isolates were obtained for the evaluation. The target disinfection level was 200 CFU/100 ml, resulting in UV and PAA doses of 7 to 30 mJ/cm
2
and 0.9 to 2.0 mg/liter, respectively. The proportions of UPECs were reduced in all samples after disinfection, with an average reduction by UV of 55% (range, 22% to 80%) and by PAA of 52% (range, 11% to 100%). Analysis of urovirulence genes revealed that the decline in the UPEC populations was not associated with any particular virulence factor. A positive association was found between the occurrence of urovirulence and antimicrobial resistance genes (ARGs). However, the changes in the prevalence of ARGs in potential UPECs were different following disinfection, i.e., UV appears to have had no effect, while PAA significantly reduced the ARG levels. Thus, this study showed that both UV and PAA disinfections reduced the proportion of UPECs and that PAA disinfection also reduced the proportion of antimicrobial resistance gene-carrying UPEC pathotypes in municipal wastewaters.
Evolved Osmotolerant Escherichia coli Mutants Frequently Exhibit Defective
N
-Acetylglucosamine Catabolism and Point Mutations in Cell Shape-Regulating Protein MreB
Authors: Winkler James D. , Garcia Carlos , Olson Michelle , Callaway Emily , Kao Katy C. 
Published: April 2014

ABSTRACT

Biocatalyst robustness toward stresses imposed during fermentation is important for efficient bio-based production. Osmotic stress, imposed by high osmolyte concentrations or dense populations, can significantly impact growth and productivity. In order to better understand the osmotic stress tolerance phenotype, we evolved sexual (capable of
in situ
DNA exchange) and asexual
Escherichia coli
strains under sodium chloride (NaCl) stress. All isolates had significantly improved growth under selection and could grow in up to 0.80 M (47 g/liter) NaCl, a concentration that completely inhibits the growth of the unevolved parental strains. Whole genome resequencing revealed frequent mutations in genes controlling
N
-acetylglucosamine catabolism (
nagC
,
nagA
), cell shape (
mrdA
,
mreB
), osmoprotectant uptake (
proV
), and motility (
fimA
). Possible epistatic interactions between
nagC
,
nagA
,
fimA
, and
proV
deletions were also detected when reconstructed as defined mutations. Biofilm formation under osmotic stress was found to be decreased in most mutant isolates, coupled with perturbations in indole secretion. Transcriptional analysis also revealed significant changes in
ompACGL
porin expression and increased transcription of sulfonate uptake systems in the evolved mutants. These findings expand our current knowledge of the osmotic stress phenotype and will be useful for the rational engineering of osmotic tolerance into industrial strains in the future.
hypD
as a Marker for [NiFe]-Hydrogenases in Microbial Communities of Surface Waters
Authors: Beimgraben Christian , Gutekunst Kirstin , Opitz Friederike , Appel Jens 
Published: April 2014

ABSTRACT

Hydrogen is an important trace gas in the atmosphere. Soil microorganisms are known to be an important part of the biogeochemical H
2
cycle, contributing 80 to 90% of the annual hydrogen uptake. Different aquatic ecosystems act as either sources or sinks of hydrogen, but the contribution of their microbial communities is unknown. [NiFe]-hydrogenases are the best candidates for hydrogen turnover in these environments since they are able to cope with oxygen. As they lack sufficiently conserved sequence motifs, reliable markers for these enzymes are missing, and consequently, little is known about their environmental distribution. We analyzed the essential maturation genes of [NiFe]-hydrogenases, including their frequency of horizontal gene transfer, and found
hypD
to be an applicable marker for the detection of the different known hydrogenase groups. Investigation of two freshwater lakes showed that [NiFe]-hydrogenases occur in many prokaryotic orders. We found that the respective
hypD
genes cooccur with oxygen-tolerant [NiFe]-hydrogenases (groups 1 and 5) mainly of
Actinobacteria
,
Acidobacteria
, and
Burkholderiales
; cyanobacterial uptake hydrogenases (group 2a) of cyanobacteria; H
2
-sensing hydrogenases (group 2b) of
Burkholderiales
,
Rhizobiales
, and
Rhodobacterales
; and two groups of multimeric soluble hydrogenases (groups 3b and 3d) of
Legionellales
and cyanobacteria. These findings support and expand a previous analysis of metagenomic data (M. Barz et al., PLoS One 5:e13846, 2010,
http://dx.doi.org/10.1371/journal.pone.0013846
) and further identify [NiFe]-hydrogenases that could be involved in hydrogen cycling in aquatic surface waters.
High Prevalence of Enterocytozoon bieneusi in Asymptomatic Pigs and Assessment of Zoonotic Risk at the Genotype Level
Authors: Zhao Wei , Zhang Weizhe , Yang Fengkun , Cao Jianping , Liu Hua , Yang Dong , Shen Yujuan , Liu Aiqin 
Published: April 2014

ABSTRACT

Enterocytozoon bieneusi
is an emerging and clinically significant enteric parasite infecting humans and animals and can cause life-threatening diarrhea in immunocompromised people. Pigs are considered to be one of the main reservoir hosts of
E. bieneusi
based on their high prevalence rates and zoonotic genotypes in pigs. As an opportunistic pathogen,
E. bieneusi
infection of pigs can be inapparent, which leads to neglect in detecting this parasite in pigs and assessing the epidemiological role of pigs in the transmission of human microsporidiosis. In the present study, 95 healthy pigs aged 2 or 3 months were randomly selected from three areas in Heilongjiang Province, China.
E. bieneusi
isolates were identified and genotyped based on the small-subunit (SSU) rRNA and internal transcribed spacer (ITS) regions of the rRNA gene by PCR and sequencing. A high prevalence of
E. bieneusi
was observed, 83.2% (79/95) at the SSU rRNA locus versus 89.5% (85/95) at the ITS locus. Ten ITS genotypes were obtained, comprising six known genotypes—EbpA (
n
= 30), D (
n
= 19), H (
n
= 18), O (
n
= 11), CS-1 (
n
= 1), and LW1 (
n
= 1)—and four novel genotypes named HLJ-I to HLJ-IV; 70.6% (60/85) of
E. bieneusi
genotypes were zoonotic (genotypes EbpA, D, and O). The findings of a high prevalence of
E. bieneusi
in pigs and a large percentage of zoonotic genotypes indicate that pigs may play a role in the transmission of
E. bieneusi
to humans and may become an important source of water contamination in our investigated areas.
Verrucomicrobia Are Candidates for Polysaccharide-Degrading Bacterioplankton in an Arctic Fjord of Svalbard
Authors: Cardman Z. , Arnosti C. , Durbin A. , Ziervogel K. , Cox C. , Steen A. D. , Teske A. 
Published: April 2014

ABSTRACTIn Arctic marine bacterial communities, members of the phylumVerrucomicrobiaare consistently detected, although not typically abundant, in 16S rRNA gene clone libraries and pyrotag surveys of the marine water column and in sediments. In an Arctic fjord (Smeerenburgfjord) of Svalbard, members of theVerrucomicrobia, together withFlavobacteriaand smaller proportions ofAlpha- andGammaproteobacteria, constituted the most frequently detected bacterioplankton community members in 16S rRNA gene-based clone library analyses of the water column. Parallel measurements in the water column of the activities of six endo-acting polysaccharide hydrolases showed that chondroitin sulfate, laminarin, and xylan hydrolysis accounted for most of the activity. SeveralVerrucomicrobiawater column phylotypes were affiliated with previously sequenced, glycoside hydrolase-rich genomes of individualVerrucomicrobiacells that bound fluorescently labeled laminarin and xylan and therefore constituted candidates for laminarin and xylan hydrolysis. In sediments, the bacterial community was dominated by different lineages ofVerrucomicrobia,Bacteroidetes, andProteobacteriabut also included members of multiple phylum-level lineages not observed in the water column. This community hydrolyzed laminarin, xylan, chondroitin sulfate, and three additional polysaccharide substrates at high rates. Comparisons with data from the same fjord in the previous summer showed that the bacterial community in Smeerenburgfjord changed in composition, most conspicuously in the changing detection frequency ofVerrucomicrobiain the water column. Nonetheless, in both years the community hydrolyzed the same polysaccharide substrates.
Development and Evaluation of a Novel Multicopy-Element-Targeting Triplex PCR for Detection of Mycobacterium avium subsp. paratuberculosis in Feces
Authors: Sevilla Iker A. , Garrido Joseba M. , Molina Elena , Geijo María V. , Elguezabal Natalia , Vázquez Patricia , Juste Ramón A. 
Published: April 2014

ABSTRACT

The enteropathy called paratuberculosis (PTB), which mainly affects ruminants and has a worldwide distribution, is caused by
Mycobacterium avium
subsp.
paratuberculosis
. This disease significantly reduces the cost-effectiveness of ruminant farms, and therefore, reliable and rapid detection methods are needed to control the spread of the bacterium in livestock and in the environment. The aim of this study was to identify a specific and sensitive combination of DNA extraction and amplification to detect
M. avium
subsp.
paratuberculosis
in feces. Negative bovine fecal samples were inoculated with increasing concentrations of two different bacterial strains (field and reference) to compare the performance of four extraction and five amplification protocols. The best results were obtained using the JohnePrep and MagMax extraction kits combined with an in-house triplex real-time PCR designed to detect IS
900
, IS
Map02
(an insertion sequence of
M. avium
subsp.
paratuberculosis
present in 6 copies per genome), and an internal amplification control DNA simultaneously. These combinations detected 10
M. avium
subsp.
paratuberculosis
cells/g of spiked feces. The triplex PCR detected 1 fg of genomic DNA extracted from the reference strain K10. The performance of the robotized version of the MagMax extraction kit combined with the IS
900
and IS
Map02
PCR was further evaluated using 615 archival fecal samples from the first sampling of nine Friesian cattle herds included in a PTB control program and followed up for at least 4 years. The analysis of the results obtained in this survey demonstrated that the diagnostic method was highly specific and sensitive for the detection of
M. avium
subsp.
paratuberculosis
in fecal samples from cattle and a very valuable tool to be used in PTB control programs.
Identification of Obscure yet Conserved Actin-Associated Proteins in Giardia lamblia
Authors: Paredez Alexander R. , Nayeri Arash , Xu Jennifer W. , Krtková Jana , Cande W. Zacheus 
Published: April 2014

ABSTRACT

Consistent with its proposed status as an early branching eukaryote,
Giardia
has the most divergent actin of any eukaryote and lacks core actin regulators. Although conserved actin-binding proteins are missing from
Giardia
, its actin is utilized similarly to that of other eukaryotes and functions in core cellular processes such as cellular organization, endocytosis, and cytokinesis. We set out to identify actin-binding proteins in
Giardia
using affinity purification coupled with mass spectroscopy (multidimensional protein identification technology [MudPIT]) and have identified >80 putative actin-binding proteins. Several of these have homology to conserved proteins known to complex with actin for functions in the nucleus and flagella. We validated localization and interaction for seven of these proteins, including 14-3-3, a known cytoskeletal regulator with a controversial relationship to actin. Our results indicate that although
Giardia
lacks canonical actin-binding proteins, there is a conserved set of actin-interacting proteins that are evolutionarily indispensable and perhaps represent some of the earliest functions of the actin cytoskeleton.
The
mtfA
Transcription Factor Gene Controls Morphogenesis, Gliotoxin Production, and Virulence in the Opportunistic Human Pathogen Aspergillus fumigatus
Authors: Smith Timothy D. , Calvo Ana M. 
Published: April 2014

ABSTRACT

Aspergillus fumigatus
is the leading causative agent of invasive aspergillosis (IA). The number of cases is on the rise, with mortality rates as high as 90% among immunocompromised patients. Molecular genetic studies in
A. fumigatus
could provide novel targets to potentially set the basis for antifungal therapies. In the current study, we investigated the role of the transcription factor gene
mtfA
in
A. fumigatus
. Our results revealed that
mtfA
plays a role in the growth and development of the fungus. Deletion or overexpression of
mtfA
leads to a slight reduction in colony growth, as well as a reduction in conidiation levels, in the overexpression strain compared to the wild-type strain. Furthermore, production of the secondary metabolite gliotoxin increased when
mtfA
was overexpressed, coinciding with an increase in the transcription levels of the gliotoxin genes
gliZ
and
gliP
with respect to the wild type. In addition, our study showed that
mtfA
is also necessary for normal protease activity in
A. fumigatus
; deletion of
mtfA
resulted in a reduction of protease activity compared to wild-type levels. Importantly, the absence of
mtfA
caused a decrease in virulence in the
Galleria mellonella
infection model, indicating that
mtfA
is necessary for
A. fumigatus
wild-type pathogenesis.
Identification and Characterization of a Gene Cluster Required for Proper Rod Shape, Cell Division, and Pathogenesis in Clostridium difficile
Authors: Ransom Eric M. , Williams Kyle B. , Weiss David S. , Ellermeier Craig D. 
Published: April 2014

ABSTRACT

Little is known about cell division in
Clostridium difficile
, a strict anaerobe that causes serious diarrheal diseases in people whose normal intestinal microbiome has been perturbed by treatment with broad-spectrum antibiotics. Here we identify and characterize a gene cluster encoding three cell division proteins found only in
C. difficile
and a small number of closely related bacteria. These proteins were named MldA, MldB, and MldC, for
m
idcell
l
ocalizing
d
ivision proteins. MldA is predicted to be a membrane protein with coiled-coil domains and a peptidoglycan-binding SPOR domain. MldB and MldC are predicted to be cytoplasmic proteins; MldB has two predicted coiled-coil domains, but MldC lacks obvious conserved domains or sequence motifs. Mutants of
mldA
or
mldB
had morphological defects, including loss of rod shape (a curved cell phenotype) and inefficient separation of daughter cells (a chaining phenotype). Fusions of cyan fluorescent protein (CFP) to MldA, MldB, and MldC revealed that all three proteins localize sharply to the division site. This application of CFP was possible because we discovered that O
2
-dependent fluorescent proteins produced anaerobically can acquire fluorescence after cells are fixed with cross-linkers to preserve native patterns of protein localization. Mutants lacking the Mld proteins are severely attenuated for pathogenesis in a hamster model of
C. difficile
infection. Because all three Mld proteins are essentially unique to
C. difficile
, they might be exploited as targets for antibiotics that combat
C. difficile
without disrupting the intestinal microbiome.
Construction and Characterization of
tetH
Overexpression and Knockout Strains of Acidithiobacillus ferrooxidans
Authors: Yu Yangyang , Liu Xiangmei , Wang Huiyan , Li Xiuting , Lin Jianqun 
Published: April 2014

ABSTRACT

Acidithiobacillus ferrooxidans
is a major participant in consortia of microorganisms used for bioleaching. It can obtain energy from the oxidation of Fe
2+
, H
2
, S
0
, and various reduced inorganic sulfur compounds (RISCs). Tetrathionate is a key intermediate during RISC oxidation, hydrolyzed by tetrathionate hydrolase (TetH), and used as sole energy source. In this study, a
tetH
knockout (Δ
tetH
) mutant and a
tetH
overexpression strain were constructed and characterized. The
tetH
overexpression strain grew better on sulfur and tetrathionate and possessed a higher rate of tetrathionate utilization and TetH activity than the wild type. However, its cell yields on tetrathionate were much lower than those on sulfur. The Δ
tetH
mutant could not grow on tetrathionate but could proliferate on sulfur with a lower cell yield than the wild type's, which indicated that tetrathionate hydrolysis is mediated only by TetH, encoded by
tetH
. The Δ
tetH
mutant could survive in ferrous medium with an Fe
2+
oxidation rate similar to that of the wild type. For the
tetH
overexpression strain, the rate was relatively higher than that of the wild type. The reverse transcription-quantitative PCR (qRT-PCR) results showed that
tetH
and
doxD2
acted synergistically, and
doxD2
was considered important in thiosulfate metabolism. Of the two
sqr
genes, AFE_0267 seemed to play as important a role in sulfide oxidation as AFE_1792. This study not only provides a substantial basis for studying the function of the
tetH
gene but also may serve as a model to clarify other candidate genes involved in sulfur oxidation in this organism.