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101.
Olivo Miotto Makoto Sekihara Shin-Ichiro Tachibana Masato Yamauchi Richard D. Pearson Roberto Amato Sonia Gonalves Somya Mehra Rintis Noviyanti Jutta Marfurt Sarah Auburn Ric N. Price Ivo Mueller Mie Ikeda Toshiyuki Mori Makoto Hirai Livingstone Tavul Manuel W. Hetzel Moses Laman Alyssa E. Barry Pascal Ringwald Jun Ohashi Francis Hombhanje Dominic P. Kwiatkowski Toshihiro Mita 《PLoS pathogens》2020,16(12)
The rapid and aggressive spread of artemisinin-resistant Plasmodium falciparum carrying the C580Y mutation in the kelch13 gene is a growing threat to malaria elimination in Southeast Asia, but there is no evidence of their spread to other regions. We conducted cross-sectional surveys in 2016 and 2017 at two clinics in Wewak, Papua New Guinea (PNG) where we identified three infections caused by C580Y mutants among 239 genotyped clinical samples. One of these mutants exhibited the highest survival rate (6.8%) among all parasites surveyed in ring-stage survival assays (RSA) for artemisinin. Analyses of kelch13 flanking regions, and comparisons of deep sequencing data from 389 clinical samples from PNG, Indonesian Papua and Western Cambodia, suggested an independent origin of the Wewak C580Y mutation, showing that the mutants possess several distinctive genetic features. Identity by descent (IBD) showed that multiple portions of the mutants’ genomes share a common origin with parasites found in Indonesian Papua, comprising several mutations within genes previously associated with drug resistance, such as mdr1, ferredoxin, atg18 and pnp. These findings suggest that a P. falciparum lineage circulating on the island of New Guinea has gradually acquired a complex ensemble of variants, including kelch13 C580Y, which have affected the parasites’ drug sensitivity. This worrying development reinforces the need for increased surveillance of the evolving parasite populations on the island, to contain the spread of resistance. 相似文献
102.
The aim of this work was to prepare recombinant amine oxidase from Aspergillus niger after overexpressing in yeast. The yeast expression vector pDR197 that includes a constitutive PMA1 promoter was used for
the expression in Saccharomyces cerevisiae. Recombinant amine oxidase was extracted from the growth medium of the yeast, purified to homogeneity and identified by activity
assay and MALDI-TOF peptide mass fingerprinting. Similarity search in the newly published A. niger genome identified six genes coding for copper amine oxidase, two of them corresponding to the previously described enzymes
AO-I a methylamine oxidase and three other genes coding for FAD amine oxidases. Thus, A. niger possesses an enormous metabolic gear to grow on amine compounds and thus support its saprophytic lifestyle. 相似文献
103.
German Andres Estrada Vera Lúcia Divan Baldani Danilo Messias de Oliveira Segundo Urquiaga José Ivo Baldani 《Plant and Soil》2013,369(1-2):115-129
Background and Aims
Plant growth-promoting bacteria, mainly diazotrophs and phosphate solubilizers, can reduce the use of chemical fertilizers for rice crops. Here, diazotrophic bacteria isolated from rice were screened for their ability to solubilize inorganic P (Pi) in vitro and in association with rice plants cultivated in pots.Methods
Forty-nine isolates were tested for the ability to solubilize Pi on NBRIP and GL agar plate media and seven selected strains were further evaluated in NBRIP liquid medium. Three of these strains were inoculated in rice plants grown in soil pots containing 15N-labeled fertilizer and two sources of P: tricalcium phosphate (TCP) or simple superphosphate (SSP). The dry matter, yield, N, P, and the 15N content accumulated in plant tissues were measured at 135 days after planting.Results
Seven strains belonging to the genera Herbaspirillum and Burkholderia formed a halo of solubilized Pi on agar plates. The Burkholderia strains showed peak soluble P (around 200 mg P L?1) on the fifth day when grown in NBRIP liquid medium for 14 days. Inoculation of Herbaspirillum strains (H18, ZA15) and a Burkholderia vietaminensis strain (AR114) increased rice grain yield from 33 to 47 % with TCP and 18 to 44 % with TSS, respectively. The bacterial inoculation led to enhanced N-use efficiency of the 15N-labeled fertilizer.Conclusion
These results suggest that the selection and use of P-solubilizing diazotrophic bacteria are a good strategy to promote P solubilization and/or N use efficiency in rice plants. 相似文献104.
Ademir Neves Cludio N. Verani Marcos A. de Brito Ivo Vencato Antnio Mangrich Glaucius Oliva Dulce D.H.F. Souza Alzir A. Batista 《Inorganica chimica acta》1999,290(2):2221-212
Copper(II) complexes were synthesized and characterized by means of elemental analysis, IR and visible spectroscopies, EPR and electrochemistry, as well as X-ray structure crystallography. The group consists of discrete mononuclear units with the general formula [Cu(II)(Hbpa)2](A)2·nH2O, where Hbpa=(2-hydroxybenzyl-2-pyridylmethyl)amine and A=ClO4 −, n=2 (1), CH3COO−, n=3 (2), NO3 −, n=2 (3) and SO4 2−, n=3 (4). The structures of the ligand Hbpa and complex 1 have been determined by X-ray crystallography. Complexes 1–4 have had their UV–Vis spectra measured in both MeCN and DMF. It was observed that the compounds interact with basic solvents, such that molecules coordinate to the metal in axial positions in which phenol oxygen atoms are coordinated in the protonated forms. The values were all less than 1000 M−1 cm−1. EPR measurements on powdered samples of 1–3 gave g/A values between 105 and 135 cm−1, typical for square planar coordination environments. Complex 4·3H2O exhibits a behaviour typical for tetrahedral coordination. The electrochemical behaviour for complexes 1 and 2 was studied showing irreversible redox waves for both compounds. 相似文献
105.
Photoisomerization and photoionization of the photoactive yellow protein chromophore in solution 下载免费PDF全文
Larsen DS Vengris M van Stokkum IH van der Horst MA de Weerd FL Hellingwerf KJ van Grondelle R 《Biophysical journal》2004,86(4):2538-2550
Dispersed pump-dump-probe spectroscopy has the ability to characterize and identify the underlying ultrafast dynamical processes in complicated chemical and biological systems. This technique builds on traditional pump-probe techniques by exploring both ground- and excited-state dynamics and characterizing the connectivity between constituent transient states. We have used the dispersed pump-dump-probe technique to investigate the ground-state dynamics and competing excited-state processes in the excitation-induced ultrafast dynamics of thiomethyl p-coumaric acid, a model chromophore for the photoreceptor photoactive yellow protein. Our results demonstrate the parallel formation of two relaxation pathways (with multiple transient states) that jointly lead to two different types of photochemistry: cis-trans isomerization and detachment of a hydrated electron. The relative transition rates and quantum yields of both pathways have been determined. We find that the relaxation of the photoexcited chromophores involves multiple, transient ground-state intermediates and the chromophore in solution does not generate persistent photoisomerized products, but instead undergoes photoionization resulting in the generation of detached electrons and radicals. These results are of great value in interpreting the more complex dynamical changes in the optical properties of the photoactive yellow protein. 相似文献
106.
Bax, a pro-apoptotic Bcl-2 family protein, translocates to mitochondria during apoptosis, where it causes MOMP (mitochondrial outer membrane permeabilization). MOMP releases pro-apoptotic factors, such as cytochrome c and SMAC (second mitochondrial activator of caspases)/Diablo, into the cytosol where they activate caspases. It is often inferred that Bax activation occurs in a single step, a conformational change in the protein causing its translocation and oligomerization into high-molecular-mass membrane pores. However, a number of studies have shown that Bax translocation to mitochondria does not necessarily induce MOMP. Indeed, Bax translocation can occur several hours prior to release of cytochrome c, indicating that its regulation may be a complex series of events, some of which occur following its association with mitochondria. In the present study, we have examined endogenous Bax in epithelial cells undergoing anoikis, a physiologically relevant form of apoptosis that occurs when normal cells lose contact with the ECM (extracellular matrix). Using BN-PAGE (blue native PAGE), we show that Bax forms a 200 kDa complex before caspase activation. Furthermore, Bax in this 200 kDa complex is not in the active conformation, as determined by exposure of N-terminal epitopes. These results indicate that Bax oligomerization is an event that must be interpreted differently from the currently held view that it represents the apoptotic pore. 相似文献
107.
Hugo Botebol Robert Sutak Ivo F. Scheiber Pierre-Louis Blaiseau François-Yves Bouget Jean-Michel Camadro Emmanuel Lesuisse 《Biometals》2014,27(1):75-88
We compared ferric EDTA, ferric citrate and ferrous ascorbate as iron sources to study iron metabolism in Ostreococcus tauri, Phaeodactlylum tricornutum and Emiliania huxleyi. Ferric EDTA was a better iron source than ferric citrate for growth and chlorophyll levels. Direct and indirect experiments showed that iron was much more available to the cells when provided as ferric citrate as compared to ferric EDTA. As a consequence, growth media with iron concentration in the range 1–100 nM were rapidly iron-depleted when ferric citrate—but not ferric EDTA was the iron source. When cultured together, P. tricornutum cells overgrew the two other species in iron-sufficient conditions, but E. huxleyi was able to compete other species in iron-deficient conditions, and when iron was provided as ferric citrate instead of ferric EDTA, which points out the critical influence of the chemical form of iron on the blooms of some phytoplankton species. The use of ferric citrate and ferrous ascorbate allowed us to unravel a kind of regulation of iron uptake that was dependent on the day/night cycles and to evidence independent uptake systems for ferrous and ferric iron, which can be regulated independently and be copper-dependent or independent. The same iron sources also allowed one to identify molecular components involved in iron uptake and storage in marine micro-algae. Characterizing the mechanisms of iron metabolism in the phytoplankton constitutes a big challenge; we show here that the use of iron sources more readily available to the cells than ferric EDTA is critical for this task. 相似文献
108.
Luiza Pinheiro Carla Ivo Brito Valéria Cataneli Pereira Adilson de Oliveira Carlos Henrique Camargo Maria de Lourdes Ribeiro de Souza da Cunha 《Memórias do Instituto Oswaldo Cruz》2014,109(7):871-878
This study aimed to correlate the presence of ica genes, biofilm
formation and antimicrobial resistance in 107 strains of Staphylococcus
epidermidis isolated from blood cultures. The isolates were analysed to
determine their methicillin resistance, staphylococcal cassette chromosome
mec (SCCmec) type, ica genes
and biofilm formation and the vancomycin minimum inhibitory concentration (MIC) was
measured for isolates and subpopulations growing on vancomycin screen agar. The
mecA gene was detected in 81.3% of the S.
epidermidis isolated and 48.2% carried SCCmec type III.
The complete icaADBC operon was observed in 38.3% of the isolates;
of these, 58.5% produced a biofilm. Furthermore, 47.7% of the isolates grew on
vancomycin screen agar, with an increase in the MIC in 75.9% of the isolates.
Determination of the MIC of subpopulations revealed that 64.7% had an MIC ≥ 4 μg
mL-1, including 15.7% with an MIC of 8 μg mL-1 and 2% with
an MIC of 16 μg mL-1. The presence of the icaADBC operon,
biofilm production and reduced susceptibility to vancomycin were associated with
methicillin resistance. This study reveals a high level of methicillin resistance,
biofilm formation and reduced susceptibility to vancomycin in subpopulations of
S. epidermidis. These findings may explain the selection of
multidrug-resistant isolates in hospital settings and the consequent failure of
antimicrobial treatment. 相似文献
109.
110.
Perea Vélez M Verhoeven TL Draing C Von Aulock S Pfitzenmaier M Geyer A Lambrichts I Grangette C Pot B Vanderleyden J De Keersmaecker SC 《Applied and environmental microbiology》2007,73(11):3595-3604
Lipoteichoic acid (LTA) is a macroamphiphile molecule which performs several functions in gram-positive bacteria, such as maintenance of cell wall homeostasis. D-alanylation of LTA requires the proteins encoded by the dlt operon, and this process is directly related to the charge properties of this polymer strongly contributing to its function. The insertional inactivation of dltD of the probiotic strain Lactobacillus rhamnosus GG (ATCC 53103) resulted in the complete absence of D-alanyl esters in the LTA as confirmed by nuclear magnetic resonance analysis. This was reflected in modifications of the bacterial cell surface properties. The dltD strain showed 2.4-fold-increased cell length, a low survival capacity in response to gastric juice challenge, an increased sensitivity to human beta-defensin-2, an increased rate of autolysis, an increased capacity to initiate growth in the presence of an anionic detergent, and a decreased capacity to initiate growth in the presence of cationic peptides compared to wild-type results. However, in vitro experiments revealed no major differences for adhesion to human intestinal epithelial cells, biofilm formation, and immunomodulation. These properties are considered to be important for probiotics. The role of the dlt operon in lactobacilli is discussed in view of these results. 相似文献