bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrogen Production by the Unicellular, Diazotrophic Cyanobacterium
Cyanothece
sp. Strain ATCC 51142 under Conditions of Continuous Light
Authors: Min Hongtao , Sherman Louis A. 
Published: May 2010

ABSTRACT

We report on the hydrogen production properties of the unicellular, diazotrophic cyanobacterium
Cyanothece
sp. strain ATCC 51142. This organism has a versatile metabolism and can grow in the presence or absence of combined nitrogen and can grow photosynthetically or mixotrophically and heterotrophically in the presence of glycerol. The strain produces a bidirectional hydrogenase (encoded by the
hox
genes), an uptake hydrogenase (
hupLS
), and nitrogenase (
nifHDK
). We demonstrated hydrogen production by both the hydrogenase and the nitrogenase under appropriate metabolic conditions. The highest rates of hydrogen production were produced under nitrogen-fixing conditions when cells were grown and incubated under continuous light conditions, in either the presence or absence of glycerol. Under such nitrogen-fixing conditions, we have achieved rates of 300 μmol H
2
/mg chloramphenicol (Chl)/hr during the first 24 h of incubation. The levels of H
2
measured were dependent upon the incubation conditions, such as sparging with argon, which generated anaerobic conditions. We demonstrated that the same conditions led to high levels of H
2
production and N
2
fixation, indicating that low-oxygen conditions favor nitrogenase activity for both processes. The levels of hydrogen produced by the hydrogenase are much lower, typically 5 to 10 μmol H
2
/mg Chl/hr. Hydrogenase activity was dependent upon electron transport through photosystem II (PS II), whereas nitrogenase activity was more dependent on PS I, as well as on respiration. Although cells do not double under the incubation conditions when sparged with argon to provide a low-oxygen environment, the cells are metabolically active, and hydrogen production can be inhibited by the addition of chloramphenicol to inhibit protein synthesis.
Dual Reporter System for
In Situ
Detection of Plasmid Transfer under Aerobic and Anaerobic Conditions
Authors: Król Jaroslaw E. , Rogers Linda M. , Krone Stephen M. , Top Eva M. 
Published: May 2010

ABSTRACT

We designed a new genetic tool to detect plasmid transfer under anaerobic and aerobic conditions. The system is based on the T7 RNA polymerase gene and a T7 promoter-driven oxygen-independent green fluorescent protein, evoglow, alone or in combination with red fluorescent protein DsRed. Constructs are available as plasmids and mini-
mariner
transposons.
High-Throughput Procedure for Tick Surveys of Tick-Borne Encephalitis Virus and Its Application in a National Surveillance Study in Switzerland
Authors: Gäumann Rahel , Mühlemann Kathrin , Strasser Marc , Beuret Christian M. 
Published: May 2010

ABSTRACT

Tick-borne encephalitis (TBE), a viral infection of the central nervous system, is endemic in many Eurasian countries. In Switzerland, TBE risk areas have been characterized by geographic mapping of clinical cases. Since mass vaccination should significantly decrease the number of TBE cases, alternative methods for exposure risk assessment are required. We established a new PCR-based test for the detection of TBE virus (TBEV) in ticks. The protocol involves an automated, high-throughput nucleic acid extraction method (QIAsymphony SP system) and a one-step duplex real-time reverse transcription-PCR (RT-PCR) assay for the detection of European subtype TBEV, including an internal process control. High usability, reproducibility, and equivalent performance for virus concentrations down to 5 × 10
3
viral genome equivalents/μl favor the automated protocol compared to the modified guanidinium thiocyanate-phenol-chloroform extraction procedure. The real-time RT-PCR allows fast, sensitive (limit of detection, 10 RNA copies/μl), and specific (no false-positive test results for other TBEV subtypes, other flaviviruses, or other tick-transmitted pathogens) detection of European subtype TBEV. The new detection method was applied in a national surveillance study, in which 62,343
Ixodes ricinus
ticks were screened for the presence of TBE virus. A total of 38 foci of endemicity could be identified, with a mean virus prevalence of 0.46%. The foci do not fully agree with those defined by disease mapping. Therefore, the proposed molecular test procedure constitutes a prerequisite for an appropriate TBE surveillance. Our data are a unique complement of human TBE disease case mapping in Switzerland.
Disruption of the Glycine Cleavage System Enables
Sinorhizobium fredii
USDA257 To Form Nitrogen-Fixing Nodules on Agronomically Improved North American Soybean Cultivars
Authors: Lorio Julio C. , Kim Won-Seok , Krishnan Ammulu H. , Krishnan Hari B. 
Published: May 2010

ABSTRACT

The symbiosis between
Sinorhizobium fredii
USDA257 and soybean [
Glycine max
(L.) Merr.] exhibits a high degree of cultivar specificity. USDA257 nodulates primitive soybean cultivars but fails to nodulate agronomically improved cultivars such as McCall. In this study we provide evidence for the involvement of a new genetic locus that controls soybean cultivar specificity. This locus was identified in USDA257 by Tn
5
transposon mutagenesis followed by nodulation screening on McCall soybean. We have cloned the region corresponding to the site of Tn
5
insertion and found that it lies within a 1.5-kb EcoRI fragment. DNA sequence analysis of this fragment and an adjacent 4.4-kb region identified an operon made up of three open reading frames encoding proteins of deduced molecular masses of 41, 13, and 104 kDa, respectively. These proteins revealed significant amino acid homology to glycine cleavage (
gcv
) system T, H, and P proteins of
Escherichia coli
and other organisms. Southern blot analysis revealed the presence of similar sequences in diverse rhizobia. Measurement of β-galactosidase activity of a USDA257 strain containing a transcriptional fusion of gcv
T
promoter sequences to the
lacZ
gene revealed that the USDA257
gcvTHP
operon was inducible by glycine. Inactivation of either
gcvT
or
gcvP
of USDA257 enabled the mutant to nodulate several agronomically improved North American soybean cultivars. These nodules revealed anatomical features typical of determinate nodules, with numerous bacteroids within the infected cells. Unlike for the previously characterized soybean cultivar specificity locus
nolBTUVW
, inactivation of the
gcv
locus had no discernible effect on the secretion of nodulation outer proteins of USDA257.
Shotgun Proteomics of
Aspergillus niger
Microsomes upon
d
-Xylose Induction
Authors: de Oliveira José Miguel P. Ferreira , van Passel Mark W. J. , Schaap Peter J. , de Graaff Leo H. 
Published: May 2010

ABSTRACT

Protein secretion plays an eminent role in cell maintenance and adaptation to the extracellular environment of microorganisms. Although protein secretion is an extremely efficient process in filamentous fungi, the mechanisms underlying protein secretion have remained largely uncharacterized in these organisms. In this study, we analyzed the effects of the
d
-xylose induction of cellulase and hemicellulase enzyme secretion on the protein composition of secretory organelles in
Aspergillus niger
. We aimed to systematically identify the components involved in the secretion of these enzymes via mass spectrometry of enriched subcellular microsomal fractions. Under each condition, fractions enriched for secretory organelles were processed for tandem mass spectrometry, resulting in the identification of peptides that originate from 1,081 proteins, 254 of which—many of them hypothetical proteins—were predicted to play direct roles in the secretory pathway.
d
-Xylose induction led to an increase in specific small GTPases known to be associated with polarized growth, exocytosis, and endocytosis. Moreover, the endoplasmic-reticulum-associated degradation (ERAD) components Cdc48 and all 14 of the 20S proteasomal subunits were recruited to the secretory organelles. In conclusion, induction of extracellular enzymes results in specific changes in the secretory subproteome of
A. niger
, and the most prominent change found in this study was the recruitment of the 20S proteasomal subunits to the secretory organelles.
Ecological Factors Characterizing the Prevalence of Bacterial Tick-Borne Pathogens in
Ixodes ricinus
Ticks in Pastures and Woodlands
Authors: Halos Lénaïg , Bord Séverine , Cotté Violaine , Gasqui Patrick , Abrial David , Barnouin Jacques , Boulouis Henri-Jean , Vayssier-Taussat Muriel , Vourc'h Gwenaël 
Published: May 2010

ABSTRACT

Ecological changes are recognized as an important driver behind the emergence of infectious diseases. The prevalence of infection in ticks depends upon ecological factors that are rarely taken into account simultaneously. Our objective was to investigate the influences of forest fragmentation, vegetation, adult tick hosts, and habitat on the infection prevalence of three tick-borne bacteria,
Borrelia burgdorferi
sensu lato,
Anaplasma phagocytophilum
, and
Rickettsia
sp. of the spotted fever group, in questing
Ixodes ricinus
ticks, taking into account tick characteristics. Samples of questing nymphs and adults were taken from 61 pastures and neighboring woodlands in central France. The ticks were tested by PCR of pools of nymphs and individual adults. The individual infection prevalence was modeled using multivariate regression. The highest infection prevalences were found in adult females collected in woodland sites for
B. burgdorferi
sensu lato and
A. phagocytophilum
(16.1% and 10.7%, respectively) and in pasture sites for
Rickettsia
sp. (8.7%). The infection prevalence in nymphs was lower than 6%.
B. burgdorferi
sensu lato was more prevalent in woodlands than in pastures. Forest fragmentation favored
B. burgdorferi
sensu lato and
A. phagocytophilum
prevalence in woodlands, and in pastures, the
B. burgdorferi
sensu lato prevalence was favored by shrubby vegetation. Both results are probably because large amounts of edges or shrubs increase the abundance of small vertebrates as reservoir hosts. The
Rickettsia
sp. prevalence was maximal on pasture with medium forest fragmentation. Female ticks were more infected by
B. burgdorferi
sensu lato than males and nymphs in woodland sites, which suggests an interaction between the ticks and the bacteria. This study confirms the complexity of the tick-borne pathogen ecology. The findings support the importance of small vertebrates as reservoir hosts and make a case for further studies in Europe on the link between the composition of the reservoir host community and the infection prevalence in ticks.
Phylogenetic Position and Peculiar Genetic Traits of a Midgut Bacterial Symbiont of the Stinkbug
Parastrachia japonensis
Authors: Hosokawa Takahiro , Kikuchi Yoshitomo , Nikoh Naruo , Meng Xian-Ying , Hironaka Mantaro , Fukatsu Takema 
Published: May 2010

ABSTRACT

The stinkbug
Parastrachia japonensis
(Hemiptera: Parastrachiidae) is known for its prolonged prereproductive nonfeeding period, maternal care of eggs in an underground nest, and maternal collection and provisioning of food (fruits) for nymphs. A previous study suggested that a bacterial symbiont is involved in uric acid recycling in this insect during the nonfeeding period, but the identity of this symbiont has not been determined. Here we characterized a novel bacterial symbiont obtained from
P. japonensis
. Molecular phylogenetic analyses based on 16S rRNA,
gyrB
, and
groEL
gene sequences consistently indicated that this symbiont constituted a distinct lineage in the
Gammaproteobacteria
that has no close relatives but is allied with gut symbionts of acanthosomatid and plataspid stinkbugs, as well as with endocellular symbionts of sharpshooters, tsetse flies, and aphids. The symbiont genes had a remarkably AT-biased nucleotide composition and exhibited significantly accelerated molecular evolution. The symbiont genome was extremely reduced; its size was estimated to be 0.85 Mb. These results suggest that there has been an intimate host-symbiont association over evolutionary time. The symbiont was localized in swollen crypts in a posterior part of the midgut, which was a specialized symbiotic organ. The possibility that the symbiont is involved in uric acid recycling is discussed. The designation “
Candidatus
Benitsuchiphilus tojoi” is proposed for the symbiont.
Increase in Acid Tolerance of
Campylobacter jejuni
through Coincubation with Amoebae
Authors: Axelsson-Olsson Diana , Svensson Lovisa , Olofsson Jenny , Salomon Paulo , Waldenström Jonas , Ellström Patrik , Olsen Björn 
Published: May 2010

ABSTRACT

Campylobacter jejuni
is a recognized and common gastrointestinal pathogen in most parts of the world. Human infections are often food borne, and the bacterium is frequent among poultry and other food animals. However, much less is known about the epidemiology of
C. jejuni
in the environment and what mechanisms the bacterium depends on to tolerate low pH. The sensitive nature of
C. jejuni
stands in contrast to the fact that it is difficult to eradicate from poultry production, and even more contradictory is the fact that the bacterium is able to survive the acidic passage through the human stomach. Here we expand the knowledge on
C. jejuni
acid tolerance by looking at protozoa as a potential epidemiological pathway of infection. Our results showed that when
C. jejuni
cells were coincubated with
Acanthamoeba polyphaga
in acidified phosphate-buffered saline (PBS) or tap water, the bacteria could tolerate pHs far below those in their normal range, even surviving at pH 4 for 20 h and at pH 2 for 5 h. Interestingly, moderately acidic conditions (pH 4 and 5) were shown to trigger
C. jejuni
motility as well as to increase adhesion/internalization of bacteria into
A. polyphaga
. Taken together, the results suggest that protozoa may act as protective hosts against harsh conditions and might be a potential risk factor for
C. jejuni
infections. These findings may be important for our understanding of
C. jejuni
passage through the gastrointestinal tract and for hygiene practices used in poultry settings.
Assessing the Potential of an Induced-Mutation Strategy for Avermectin Overproducers
Authors: Gao Hong , Liu Mei , Zhuo Ying , Zhou Xianlong , Liu Jintao , Chen Difei , Zhang Wenquan , Gou Zhongxuan , Shang Peng , Zhang Lixin 
Published: May 2010

ABSTRACT

Mutant libraries of avermectin-producing
Streptomyces avermitilis
strains were constructed by different mutagenesis strategies. A metric was applied to assess the mutation spectrum by calculating the distribution of average phenotypic distance of each population. The results showed for the first time that a microgravity environment could introduce larger phenotype distribution and diversity than UV and
N
-methyl-
N
-nitro-
N
-nitrosoguanidine (NTG) could.
Metagenomic Analysis of Apple Orchard Soil Reveals Antibiotic Resistance Genes Encoding Predicted Bifunctional Proteins
Authors: Donato Justin J. , Moe Luke A. , Converse Brandon J. , Smart Keith D. , Berklein Flora C. , McManus Patricia S. , Handelsman Jo 
Published: May 2010

ABSTRACT

To gain insight into the diversity and origins of antibiotic resistance genes, we identified resistance genes in the soil in an apple orchard using functional metagenomics, which involves inserting large fragments of foreign DNA into
Escherichia coli
and assaying the resulting clones for expressed functions. Among 13 antibiotic-resistant clones, we found two genes that encode bifunctional proteins. One predicted bifunctional protein confers resistance to ceftazidime and contains a natural fusion between a predicted transcriptional regulator and a β-lactamase. Sequence analysis of the entire metagenomic clone encoding the predicted bifunctional β-lactamase revealed a gene potentially involved in chloramphenicol resistance as well as a predicted transposase. A second clone that encodes a predicted bifunctional protein confers resistance to kanamycin and contains an aminoglycoside acetyltransferase domain fused to a second acetyltransferase domain that, based on nucleotide sequence, was predicted not to be involved in antibiotic resistance. This is the first report of a transcriptional regulator fused to a β-lactamase and of an aminoglycoside acetyltransferase fused to an acetyltransferase not involved in antibiotic resistance.
Comparison of Different DNA-Based Methods for Molecular Typing of
Histoplasma capsulatum
Authors: Muniz Mauro de Medeiros , Morais e Silva Tavares Patrícia , Meyer Wieland , Nosanchuk Joshua Daniel , Zancope-Oliveira Rosely Maria 
Published: May 2010

ABSTRACT

Histoplasma capsulatum
is very prevalent in the environment and is one of the most common causes of mycoses in humans and diverse animals in Brazil. Multiple typing methods have been developed to study
H. capsulatum
epidemiology; however, there is limited information concerning comparisons of results obtained with different methods using the same set of isolates. To explore the diversity of
H. capsulatum
in Brazil and to determine correlations between the results of three different molecular typing techniques, we examined 51 environmental, animal, and human isolates by M13 PCR fingerprinting, PCR-restriction fragment length polymorphism (RFLP) analysis of the internal transcribed region 1 (ITS1)-5.8S-ITS2 region of the rDNA locus, and DNA sequencing and phylogenetic analysis of parts of four protein-encoding genes, the
Arf
(ADP ribosylation factor), H-anti (H antigen precursor),
Ole
(delta-9 fatty acid desaturase), and
Tub1
(alpha-tubulin) genes. Each method identified three major genetic clusters, and there was a high level of concordance between the results of the typing techniques. The M13 PCR fingerprinting and PCR-RFLP analyses produced very similar results and separated the
H. capsulatum
isolates included in this study into three major groups. An additional approach used was comparison of our Brazilian ITS1-5.8S-ITS2 sequences with the sequences deposited previously in NCBI data banks. Our analyses suggest that
H. capsulatum
can be divided into different molecular types that are dispersed around the world. Our results indicate that the three methods used in this study are reliable and reproducible and that they have similar sensitivities. However, M13 PCR fingerprinting has some advantages over the other two methods as it is faster, cheaper, and more user friendly, which especially increases its utility for molecular typing of
Histoplasma
in situations where laboratory facilities are relatively limited.
Improvement of Multiple-Stress Tolerance and Lactic Acid Production inLactococcus lactisNZ9000 under Conditions of Thermal Stress by Heterologous Expression ofEscherichia coli dnaK
Authors: Abdullah-Al-Mahin  , Sugimoto Shinya , Higashi Chihana , Matsumoto Shunsuke , Sonomoto Kenji 
Published: May 2010

ABSTRACTThe effects of nisin-induceddnaKexpression inLactococcus lactiswere examined, and this expression was shown to improve stress tolerance and lactic acid fermentation efficiency. Using a nisin-inducible expression system, DnaK proteins fromL. lactis(DnaKLla) andEscherichia coli(DnaKEco) were produced inL. lactisNZ9000. In comparison to a strain harboring the empty vector pNZ8048 (designated NZ-Vector) and one expressingdnaKLla(designated NZ-LDnaK), thednaKEco-expressing strain, named NZ-EDnaK, exhibited more tolerance to heat stress at 40°C in GM17 liquid medium. The cell viability of NZ-Vector was reduced 4.6-fold after 6 h of heat treatment. However, NZ-EDnaK showed 13.5-fold increased viability under these conditions, with a very low concentration of DnaKEcoproduction. Although the heterologous expression ofdnaKEcodid not effect DnaKLlaproduction, heat treatment increased the DnaKLlalevel 3.5- and 3.6-fold in NZ-Vector and NZ-EDnaK, respectively. Moreover, NZ-EDnaK showed tolerance to multiple stresses, including 3% NaCl, 5% ethanol, and 0.5% lactic acid (pH 5.47). In CMG medium, the lactate yield and the maximum lactate productivity of NZ-EDnaK were higher than the corresponding values for NZ-Vector at 30°C. Interestingly, at 40°C, these values of NZ-EDnaK were not significantly different from the corresponding values for the control strain at 30°C. Lactate dehydrogenase (LDH) activity was also found to be stable at 40°C in the presence of DnaKEco. These findings suggest that the heterologous expression ofdnaKEcoenhances the quality control of proteins and enzymes, resulting in improved growth and lactic acid fermentation at high temperature.
Evaluation of a Stochastic Inactivation Model for Heat-Activated Spores of
Bacillus
spp
Authors: Corradini Maria G. , Normand Mark D. , Eisenberg Murray , Peleg Micha 
Published: May 2010

ABSTRACT

Heat activates the dormant spores of certain
Bacillus
spp., which is reflected in the “activation shoulder” in their survival curves. At the same time, heat also inactivates the already active and just activated spores, as well as those still dormant. A stochastic model based on progressively changing probabilities of activation and inactivation can describe this phenomenon. The model is presented in a fully probabilistic discrete form for individual and small groups of spores and as a semicontinuous deterministic model for large spore populations. The same underlying algorithm applies to both isothermal and dynamic heat treatments. Its construction does not require the assumption of the activation and inactivation kinetics or knowledge of their biophysical and biochemical mechanisms. A simplified version of the semicontinuous model was used to simulate survival curves with the activation shoulder that are reminiscent of experimental curves reported in the literature. The model is not intended to replace current models to predict dynamic inactivation but only to offer a conceptual alternative to their interpretation. Nevertheless, by linking the survival curve's shape to probabilities of events at the individual spore level, the model explains, and can be used to simulate, the irregular activation and survival patterns of individual and small groups of spores, which might be involved in food poisoning and spoilage.
Microbial Community Structure and Denitrification in a Wetland Mitigation Bank
Authors: Peralta Ariane L. , Matthews Jeffrey W. , Kent Angela D. 
Published: May 2010

ABSTRACT

Wetland mitigation is implemented to replace ecosystem functions provided by wetlands; however, restoration efforts frequently fail to establish equivalent levels of ecosystem services. Delivery of microbially mediated ecosystem functions, such as denitrification, is influenced by both the structure and activity of the microbial community. The objective of this study was to compare the relationship between soil and vegetation factors and microbial community structure and function in restored and reference wetlands within a mitigation bank. Microbial community composition was assessed using terminal restriction fragment length polymorphism targeting the 16S rRNA gene (total bacteria) and the
nosZ
gene (denitrifiers). Comparisons of microbial function were based on potential denitrification rates. Bacterial community structures differed significantly between restored and reference wetlands; denitrifier community assemblages were similar among reference sites but highly variable among restored sites throughout the mitigation bank. Potential denitrification was highest in the reference wetland sites. These data demonstrate that wetland restoration efforts in this mitigation bank have not successfully restored denitrification and that differences in potential denitrification rates may be due to distinct microbial assemblages observed in restored and reference (natural) wetlands. Further, we have identified gradients in soil moisture and soil fertility that were associated with differences in microbial community structure. Microbial function was influenced by bacterial community composition and soil fertility. Identifying soil factors that are primary ecological drivers of soil bacterial communities, especially denitrifying populations, can potentially aid the development of predictive models for restoration of biogeochemical transformations and enhance the success of wetland restoration efforts.