bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cyclic AMP (cAMP) Receptor Protein-cAMP Complex Regulates Heparosan Production in Escherichia coli Strain Nissle 1917
Authors: Yan Huihui , Bao Feifei , Zhao Liping , Yu Yanying , Tang Jiaqin , Zhou Xianxuan 
Published: August 2015

ABSTRACT

Heparosan serves as the starting carbon backbone for the chemoenzymatic synthesis of heparin, a widely used clinical anticoagulant drug. The availability of heparosan is a significant concern for the cost-effective synthesis of bioengineered heparin. The carbon source is known as the pivotal factor affecting heparosan production. However, the mechanism by which carbon sources control the biosynthesis of heparosan is unclear. In this study, we found that the biosynthesis of heparosan was influenced by different carbon sources. Glucose inhibits the biosynthesis of heparosan, while the addition of either fructose or mannose increases the yield of heparosan. Further study demonstrated that the cyclic AMP (cAMP)-cAMP receptor protein (CRP) complex binds to the upstream region of the region 3 promoter and stimulates the transcription of the gene cluster for heparosan biosynthesis. Site-directed mutagenesis of the CRP binding site abolished its capability of binding CRP and eliminated the stimulative effect on transcription.
1
H nuclear magnetic resonance (NMR) analysis was further performed to determine the
Escherichia coli
strain Nissle 1917 (EcN) heparosan structure and quantify extracellular heparosan production. Our results add to the understanding of the regulation of heparosan biosynthesis and may contribute to the study of other exopolysaccharide-producing strains.
Rapid Proliferation of Vibrio parahaemolyticus, Vibrio vulnificus, and Vibrio cholerae during Freshwater Flash Floods in French Mediterranean Coastal Lagoons
Authors: Esteves Kevin , Hervio-Heath Dominique , Mosser Thomas , Rodier Claire , Tournoud Marie-George , Jumas-Bilak Estelle , Colwell Rita R. , Monfort Patrick 
Published: August 2015

ABSTRACT

Vibrio parahaemolyticus
,
Vibrio vulnificus
, and
Vibrio cholerae
of the non-O1/non-O139 serotype are present in coastal lagoons of southern France. In these Mediterranean regions, the rivers have long low-flow periods followed by short-duration or flash floods during and after heavy intense rainstorms, particularly at the end of the summer and in autumn. These floods bring large volumes of freshwater into the lagoons, reducing their salinity. Water temperatures recorded during sampling (15 to 24°C) were favorable for the presence and multiplication of vibrios. In autumn 2011, before heavy rainfalls and flash floods, salinities ranged from 31.4 to 36.1‰ and concentrations of
V. parahaemolyticus
,
V. vulnificus
, and
V. cholerae
varied from 0 to 1.5 × 10
3
most probable number (MPN)/liter, 0.7 to 2.1 × 10
3
MPN/liter, and 0 to 93 MPN/liter, respectively. Following heavy rainstorms that generated severe flash flooding and heavy discharge of freshwater, salinity decreased, reaching 2.2 to 16.4‰ within 15 days, depending on the site, with a concomitant increase in
Vibrio
concentration to ca. 10
4
MPN/liter. The highest concentrations were reached with salinities between 10 and 20‰ for
V. parahaemolyticus
, 10 and 15‰ for
V. vulnificus
, and 5 and 12‰ for
V. cholerae
. Thus, an abrupt decrease in salinity caused by heavy rainfall and major flooding favored growth of human-pathogenic
Vibrio
spp. and their proliferation in the Languedocian lagoons. Based on these results, it is recommended that temperature and salinity monitoring be done to predict the presence of these
Vibrio
spp. in shellfish-harvesting areas of the lagoons.
Comparison of the Seasonal Variations of Synechococcus Assemblage Structures in Estuarine Waters and Coastal Waters of Hong Kong
Authors: Xia Xiaomin , Vidyarathna Nayani K. , Palenik Brian , Lee Puiyin , Liu Hongbin 
Published: August 2015

ABSTRACTSeasonal variation in the phylogenetic composition ofSynechococcusassemblages in estuarine and coastal waters of Hong Kong was examined through pyrosequencing of therpoC1gene. Sixteen samples were collected in 2009 from two stations representing estuarine and ocean-influenced coastal waters, respectively.Synechococcusabundance in coastal waters gradually increased from 3.6 × 103cells ml−1in March, reaching a peak value of 5.7 × 105cells ml−1in July, and then gradually decreased to 9.3 × 103cells ml−1in December. The changes inSynechococcusabundance in estuarine waters followed a pattern similar to that in coastal waters, whereas its composition shifted from being dominated by phycoerythrin-rich (PE-type) strains in winter to phycocyanin-only (PC-type) strains in summer owing to the increase in freshwater discharge from the Pearl River and higher water temperature. The high abundance of PC-typeSynechococcuswas composed of subcluster 5.2 marineSynechococcus, freshwaterSynechococcus(F-PC), andCyanobium. TheSynechococcusassemblage in the coastal waters, on the other hand, was dominated by marine PE-typeSynechococcus, with subcluster 5.1 clades II and VI as the major lineages from April to September, when the summer monsoon prevailed. Besides these two clades, clade III cooccurred with clade V at relatively high abundance in summer. During winter, theSynechococcusassemblage compositions at the two sites were similar and were dominated by subcluster 5.1 clades II and IX and an undescribed clade (represented bySynechococcussp. strain miyav). Clade IXSynechococcuswas a relatively ubiquitous PE-typeSynechococcusfound at both sites, and our study demonstrates that some strains of the clade have the ability to deal with large variation of salinity in subtropical estuarine environments. Our study suggests that changes in seawater temperature and salinity caused by the seasonal variation of monsoonal forcing are two major determinants of the community composition and abundance ofSynechococcusassemblages in Hong Kong waters.
Mutual Cross-Feeding Interactions between Bifidobacterium longum subsp. longum NCC2705 and Eubacterium rectale ATCC 33656 Explain the Bifidogenic and Butyrogenic Effects of Arabinoxylan Oligosaccharides
Authors: Rivière Audrey , Gagnon Mérilie , Weckx Stefan , Roy Denis , De Vuyst Luc 
Published: August 2015

ABSTRACT

Arabinoxylan oligosaccharides (AXOS) are a promising class of prebiotics that have the potential to stimulate the growth of bifidobacteria and the production of butyrate in the human colon, known as the bifidogenic and butyrogenic effects, respectively. Although these dual effects of AXOS are considered beneficial for human health, their underlying mechanisms are still far from being understood. Therefore, this study investigated the metabolic interactions between
Bifidobacterium longum
subsp.
longum
NCC2705 (
B. longum
NCC2705), an acetate producer and arabinose substituent degrader of AXOS, and
Eubacterium rectale
ATCC 33656, an acetate-converting butyrate producer. Both strains belong to prevalent species of the human colon microbiota. The strains were grown on AXOS during mono- and coculture fermentations, and their growth, AXOS consumption, metabolite production, and expression of key genes were monitored. The results showed that the growth of both strains and gene expression in both strains were affected by cocultivation and that these effects could be linked to changes in carbohydrate consumption and concomitant metabolite production. The consumption of the arabinose substituents of AXOS by
B. longum
NCC2705 with the concomitant production of acetate allowed
E. rectale
ATCC 33656 to produce butyrate (by means of a butyryl coenzyme A [CoA]:acetate CoA-transferase), explaining the butyrogenic effect of AXOS.
Eubacterium rectale
ATCC 33656 released xylose from the AXOS substrate, which favored the
B. longum
NCC2705 production of acetate, explaining the bifidogenic effect of AXOS. Hence, those interactions represent mutual cross-feeding mechanisms that favor the coexistence of bifidobacterial strains and butyrate producers in the same ecological niche. In conclusion, this study provides new insights into the bifidogenic and butyrogenic effects of AXOS.
Rhodococcus erythropolis BG43 Genes Mediating Pseudomonas aeruginosa Quinolone Signal Degradation and Virulence Factor Attenuation
Authors: Müller Christine , Birmes Franziska S. , Rückert Christian , Kalinowski Jörn , Fetzner Susanne 
Published: August 2015

ABSTRACT

Rhodococcus erythropolis
BG43 is able to degrade the
Pseudomonas aeruginosa
quorum sensing signal molecules PQS (
Pseudomonas
quinolone signal) [2-heptyl-3-hydroxy-4(1
H
)-quinolone] and HHQ [2-heptyl-4(1
H
)-quinolone] to anthranilic acid. Based on the hypothesis that degradation of HHQ might involve hydroxylation to PQS followed by dioxygenolytic cleavage of the heterocyclic ring and hydrolysis of the resulting
N
-octanoylanthranilate, the genome was searched for corresponding candidate genes. Two gene clusters,
aqdA1B1C1
and
aqdA2B2C2
, each predicted to code for a hydrolase, a flavin monooxygenase, and a dioxygenase related to 1
H
-3-hydroxy-4-oxoquinaldine 2,4-dioxygenase, were identified on circular plasmid pRLCBG43 of strain BG43. Transcription of all genes was upregulated by PQS, suggesting that both gene clusters code for alkylquinolone-specific catabolic enzymes. An
aqdR
gene encoding a putative transcriptional regulator, which was also inducible by PQS, is located adjacent to the
aqdA2B2C2
cluster. Expression of
aqdA2B2C2
in
Escherichia coli
conferred the ability to degrade HHQ and PQS to anthranilic acid; however, for
E. coli
transformed with
aqdA1B1C1
, only PQS degradation was observed. Purification of the recombinant AqdC1 protein verified that it catalyzes the cleavage of PQS to form
N
-octanoylanthranilic acid and carbon monoxide and revealed apparent

K
m

and
k
cat
values for PQS of ∼27 μM and 21 s
−1
, respectively. Heterologous expression of the PQS dioxygenase gene
aqdC1
or
aqdC2
in
P. aeruginosa
PAO1 quenched the production of the virulence factors pyocyanin and rhamnolipid and reduced the synthesis of the siderophore pyoverdine. Thus, the toolbox of quorum-quenching enzymes is expanded by new PQS dioxygenases.
YjeH Is a Novel Exporter of
l
-Methionine and Branched-Chain Amino Acids in Escherichia coli
Authors: Liu Qian , Liang Yong , Zhang Yun , Shang Xiuling , Liu Shuwen , Wen Jifu , Wen Tingyi 
Published: August 2015

ABSTRACT

Amino acid efflux transport systems have important physiological functions and play vital roles in the fermentative production of amino acids. However, no methionine exporter has yet been identified in
Escherichia coli
. In this study, we identified a novel amino acid exporter, YjeH, in
E. coli
. The
yjeH
overexpression strain exhibited high tolerance to the structural analogues of
l
-methionine and branched-chain amino acids, decreased intracellular amino acid levels, and enhanced export rates in the presence of a Met-Met, Leu-Leu, Ile-Ile, or Val-Val dipeptide, suggesting that YjeH functions as an exporter of
l
-methionine and the three branched-chain amino acids. The export of the four amino acids in the
yjeH
overexpression strain was competitively inhibited in relation to each other. The expression of
yjeH
was strongly induced by increasing cytoplasmic concentrations of substrate amino acids. Green fluorescent protein (GFP)-tagged YjeH was visualized by total internal reflection fluorescence microscopy to confirm the plasma membrane localization of YjeH. Phylogenetic analysis of transporters indicated that YjeH belongs to the amino acid efflux family of the amino acid/polyamine/organocation (APC) superfamily. Structural modeling revealed that YjeH has the typical “5 + 5” transmembrane α-helical segment (TMS) inverted-repeat fold of APC superfamily transporters, and its binding sites are strictly conserved. The enhanced capacity of
l
-methionine export by the overexpression of
yjeH
in an
l
-methionine-producing strain resulted in a 70% improvement in titer. This study supplements the transporter classification and provides a substantial basis for the application of the methionine exporter in metabolic engineering.
Cross-Immunity and Community Structure of a Multiple-Strain Pathogen in the Tick Vector
Authors: Durand Jonas , Jacquet Maxime , Paillard Lye , Rais Olivier , Gern Lise , Voordouw Maarten J. 
Published: August 2015

ABSTRACT

Many vector-borne pathogens consist of multiple strains that circulate in both the vertebrate host and the arthropod vector. Characterization of the community of pathogen strains in the arthropod vector is therefore important for understanding the epidemiology of mixed vector-borne infections.
Borrelia afzelii
and
B. garinii
are two species of tick-borne bacteria that cause Lyme disease in humans. These two sympatric pathogens use the same tick,
Ixodes ricinus
, but are adapted to different classes of vertebrate hosts. Both
Borrelia
species consist of multiple strains that are classified using the highly polymorphic
ospC
gene. Vertebrate cross-immunity against the OspC antigen is predicted to structure the community of multiple-strain
Borrelia
pathogens.
Borrelia
isolates were cultured from field-collected
I. ricinus
ticks over a period spanning 11 years. The
Borrelia
species of each isolate was identified using a reverse line blot (RLB) assay. Deep sequencing was used to characterize the
ospC
communities of 190
B. afzelii
isolates and 193
B. garinii
isolates. Infections with multiple
ospC
strains were common in ticks, but vertebrate cross-immunity did not influence the strain structure in the tick vector. The pattern of genetic variation at the
ospC
locus suggested that vertebrate cross-immunity exerts strong selection against intermediately divergent
ospC
alleles. Deep sequencing found that more than 50% of our isolates contained exotic
ospC
alleles derived from other
Borrelia
species. Two alternative explanations for these exotic
ospC
alleles are cryptic coinfections that were not detected by the RLB assay or horizontal transfer of the
ospC
gene between
Borrelia
species.
Metabolism of Fructooligosaccharides in Lactobacillus plantarum ST-III via Differential Gene Transcription and Alteration of Cell Membrane Fluidity
Authors: Chen Chen , Zhao Guozhong , Chen Wei , Guo Benheng 
Published: August 2015

ABSTRACT

Although fructooligosaccharides (FOS) can selectively stimulate the growth and activity of probiotics and beneficially modulate the balance of intestinal microbiota, knowledge of the molecular mechanism for FOS metabolism by probiotics is still limited. Here a combined transcriptomic and physiological approach was used to survey the global alterations that occurred during the logarithmic growth of
Lactobacillus plantarum
ST-III using FOS or glucose as the sole carbon source. A total of 363 genes were differentially transcribed; in particular, two gene clusters were induced by FOS. Gene inactivation revealed that both of the clusters participated in the metabolism of FOS, which were transported across the membrane by two phosphotransferase systems (PTSs) and were subsequently hydrolyzed by a β-fructofuranosidase (SacA) in the cytoplasm. Combining the measurements of the transcriptome- and membrane-related features, we discovered that the genes involved in the biosynthesis of fatty acids (FAs) were repressed in cells grown on FOS; as a result, the FA profiles were altered by shortening of the carbon chains, after which membrane fluidity increased in response to FOS transport and utilization. Furthermore, incremental production of acetate was observed in both the transcriptomic and the metabolic experiments. Our results provided new insights into gene transcription, the production of metabolites, and membrane alterations that could explain FOS metabolism in
L. plantarum
.
A MORN Repeat Protein Facilitates Protein Entry into the Flagellar Pocket of Trypanosoma brucei
Authors: Morriswood Brooke , Schmidt Katy 
Published: August 2015

ABSTRACT

The parasite
Trypanosoma brucei
lives in the bloodstream of infected mammalian hosts, fully exposed to the adaptive immune system. It relies on a very high rate of endocytosis to clear bound antibodies from its cell surface. All endo- and exocytosis occurs at a single site on its plasma membrane, an intracellular invagination termed the flagellar pocket. Coiled around the neck of the flagellar pocket is a multiprotein complex containing the repeat motif protein
T. brucei
MORN1 (TbMORN1). In this study, the phenotypic effects of TbMORN1 depletion in the mammalian-infective form of
T. brucei
were analyzed. Depletion of TbMORN1 resulted in a rapid enlargement of the flagellar pocket. Dextran, a polysaccharide marker for fluid phase endocytosis, accumulated inside the enlarged flagellar pocket. Unexpectedly, however, the proteins concanavalin A and bovine serum albumin did not do so, and concanavalin A was instead found to concentrate outside it. This suggests that TbMORN1 may have a role in facilitating the entry of proteins into the flagellar pocket.
Unfolded Protein Response Pathways in Bloodstream-Form Trypanosoma brucei?
Authors: Tiengwe Calvin , Brown Abigail E. N. A. , Bangs James D. 
Published: August 2015

ABSTRACT

The unfolded protein response (UPR) is a stress mechanism to cope with misfolded proteins in the early secretory pathway, the hallmark being transcriptional upregulation of endoplasmic reticulum (ER) molecular chaperones such as BiP and protein disulfide isomerase. Despite the lack of transcriptional regulation and the absence of the classical UPR machinery, African trypanosomes apparently respond to persistent ER stress by a UPR-like response, including upregulation of BiP, and a related spliced leader silencing (SLS) response whereby SL RNA transcription is shut down. Initially observed by knockdown of the secretory protein translocation machinery, both responses are also induced by chemical agents known to elicit UPR in mammalian cells (H. Goldshmidt, D. Matas, A. Kabi, A. Carmi, R. Hope, S. Michaeli, PLoS Pathog 6:e1000731, 2010,
http://dx.doi.org/10.1371/journal.ppat.1000731
). As these findings were generated primarily in procyclic-stage trypanosomes, we have investigated both responses in pathogenic bloodstream-stage parasites. RNA interference (RNAi) silencing of the core translocon subunit
Trypanosoma brucei
Sec61α (TbSec61α) failed to induce either response. Interestingly, cell growth halted within 16 h of silencing, but sufficient TbSec61α remained to allow full competence for translocation of nascent secretory proteins for up to 24 h, indicating that replication is finely coupled with the capacity to synthesize and transport secretory cargo. Tunicamycin and thapsigargin at concentrations compatible with short-term (4 h) and long-term (24 h) viability also failed to induce any of the indicators of UPR-like or SLS responses. Dithiothreitol (DTT) was lethal at all concentrations tested. These results indicate that UPR-like and SLS responses to persistent ER stress do not occur in bloodstream-stage trypanosomes.
Clinical profile of diabetes mellitus in tuberculosis
Authors: Ogbera Anthonia Okeoghene , Kapur Anil , Abdur-Razzaq Hussein , Harries Anthony D , Ramaiya Kaushik , Adeleye Olufunmilayo , Kuku Sonny 
Published: August 2015

ObjectiveThe objective is to document the clinical profile of diabetes mellitus (DM) in tuberculosis (TB).Type of studyThis was a descriptive observational study.MethodsA total of 4000 persons aged above 12 years with a confirmed diagnosis of TB and on treatment were recruited. The study subjects were screened for DM and diagnoses were made on the basis of the WHO criteria. Clinical parameters were compared between persons with DM and those without DM.ResultsMean age was higher in patients with TB and DM than in persons without DM, and this difference was statistically significant (40.9 vs 39.6 years, p=0.0002). DM/TB comorbidity was noted in 480 persons and these made up 12.3% of the study population. Some clinical features of patients with TB who had DM included a positive family history of DM, a history of hypertension, and central obesity.ConclusionsGiven the substantial burden of DM and TB comorbidity, we recommend that patients with TB be screened routinely for DM. However, further research is needed to clarify the risk factors for the occurrence of DM in TB.
Sitagliptin versus mitiglinide switched from mealtime dosing of a rapid-acting insulin analog in patients with type 2 diabetes: a randomized, parallel-group study
Authors: Takeshita Yumie , Takamura Toshinari , Kita Yuki , Takazakura Akiko , Kato Ken-ichiro , Isobe Yuki , Kaneko Shuichi 
Published: August 2015

PurposeWe determined the feasibility of substituting sitagliptin or mitiglinide for bolus insulin injection therapy in patients with type 2 diabetes.Methods60 patients with type 2 diabetes were enrolled and randomized to switch from mealtime dosing of a rapid-acting insulin analog to either sitagliptin or mitiglinide for 16 weeks.ResultsBody weight, body mass index, and waist circumference decreased significantly in both groups at the end of the study. Mitiglinide significantly increased fasting plasma glucose (FPG) levels at the end of the study from 146.5±36.3 to 168.0±38.8 mg/dL, whereas sitagliptin did not affect FPG. Glycated hemoglobin (HbA1c) and 1,5-anhydroglucitol increased significantly in both groups. The C peptide immunoreactivity (CPR) responses after arginine were diminished in both groups. γ-GTP and triglycerides increased, and high-density lipoprotein cholesterol and adiponectin decreased, in the sitagliptin group, but not in the mitiglinide group. Mean Diabetes Treatment Satisfaction Questionnaire scores improved significantly in both groups. Patients whose mean total daily doses of rapid-acting insulin analog were 16.6 and 17.8 units were switched to sitagliptin and mitiglinide, respectively, without a change in the HbA1c level. Total insulin doses/body weight predicted changes in HbA1c only in the sitagliptin group, but not in the mitiglinide group. Use of >0.27 IU/kg of a rapid-acting insulin analog predicted an increase in HbA1c after switching to sitagliptin. The CPR index (CPI) was also a predictor for a change in HbA1c in the sitagliptin group, but not in the mitiglinide group; patients with a CPI<1.4 developed a worse HbA1c after switching to sitagliptin.ConclusionsSitagliptin may predominantly act on FPG, whereas mitiglinide may act on postprandial plasma glucose to achieve glycemic control after switching from a bolus insulin regimen. Additional therapy to sitagliptin or mitiglinide is clearly required to obtain equivalent glycemic control in patients using a higher dose of insulin.Trial registration number(UMIN 000007051)