43 research outputs found
Distribution of polycyclic aromatic hydrocarbons in subcellular root tissues of ryegrass (Lolium multiflorum Lam.)
BACKGROUND: Because of the increasing quantity and high toxicity to humans of polycyclic aromatic hydrocarbons (PAHs) in the environment, several bioremediation mechanisms and protocols have been investigated to restore PAH-contaminated sites. The transport of organic contaminants among plant cells via tissues and their partition in roots, stalks, and leaves resulting from transpiration and lipid content have been extensively investigated. However, information about PAH distributions in intracellular tissues is lacking, thus limiting the further development of a mechanism-based phytoremediation strategy to improve treatment efficiency. RESULTS: Pyrene exhibited higher uptake and was more recalcitrant to metabolism in ryegrass roots than was phenanthrene. The kinetic processes of uptake from ryegrass culture medium revealed that these two PAHs were first adsorbed onto root cell walls, and they then penetrated cell membranes and were distributed in intracellular organelle fractions. At the beginning of uptake (< 50 h), adsorption to cell walls dominated the subcellular partitioning of the PAHs. After 96 h of uptake, the subcellular partition of PAHs approached a stable state in the plant water system, with the proportion of PAH distributed in subcellular fractions being controlled by the lipid contents of each component. Phenanthrene and pyrene primarily accumulated in plant root cell walls and organelles, with about 45% of PAHs in each of these two fractions, and the remainder was retained in the dissolved fraction of the cells. Because of its higher lipophilicity, pyrene displayed greater accumulation factors in subcellular walls and organelle fractions than did phenanthrene. CONCLUSIONS: Transpiration and the lipid content of root cell fractions are the main drivers of the subcellular partition of PAHs in roots. Initially, PAHs adsorb to plant cell walls, and they then gradually diffuse into subcellular fractions of tissues. The lipid content of intracellular components determines the accumulation of lipophilic compounds, and the diffusion rate is related to the concentration gradient established between cell walls and cell organelles. Our results offer insights into the transport mechanisms of PAHs in ryegrass roots and their diffusion in root cells
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Alkali-earth metal bridges formed in biofilm matrices regulate the uptake of fluoroquinolone antibiotics and protect against bacterial apoptosis
Bacterially extracellular biofilms play a critical role in relieving toxicity of fluoroquinolone antibiotic (FQA) pollutants, yet it is unclear whether antibiotic attack may be defused by a bacterial one-two punch strategy associated with metal-reinforced detoxification efficiency. Our findings help to assign functions to specific structural features of biofilms, as they strongly imply a molecularly regulated mechanism by which freely accessed alkaliāearth metals in natural waters affect the cellular uptake of FQAs at the water-biofilm interface. Specifically, formation of alkali-earth-metal (Ca2+ or Mg2+) bridge between modeling ciprofloxacin and biofilms of Escherichia coli regulates the trans-biofilm transport rate of FQAs towards cells (135-nm-thick biofilm). As the addition of Ca2+ and Mg2+ (0ā3.5 mmol/L, CIP: 1.25 Ī¼mol/L), the transport rates were reduced to 52.4% and 63.0%, respectively. Computational chemistry analysis further demonstrated a deprotonated carboxyl in the tryptophan residues of biofilms acted as a major bridge site, of which one side is a metal and the other is a metal girder jointly connected to the carboxyl and carbonyl of a FQA. The bacterial growth rate depends on the bridging energy at anchoring site, which underlines the environmental importance of metal bridge formed in biofilm matrices in bacterially antibiotic resistance
Modeling Rett Syndrome Using TALEN-Edited MECP2 Mutant Cynomolgus Monkeys
Gene-editing technologies have made it feasible to create nonhuman primate models for human genetic disorders. Here, we report detailed genotypes and phenotypes of TALEN-edited MECP2 mutant cynomolgus monkeys serving as a model for a neurodevelopmental disorder, Rett syndrome (RTT), which is caused by loss-of-function mutations in the human MECP2 gene. Male mutant monkeys were embryonic lethal, reiterating that RTT is a disease of females. Through a battery of behavioral analyses, including primate-unique eye-tracking tests, in combination with brain imaging via MRI, we found a series of physiological, behavioral, and structural abnormalities resembling clinical manifestations of RTT. Moreover, blood transcriptome profiling revealed that mutant monkeys resembled RTT patients in immune gene dysregulation. Taken together, the stark similarity in phenotype and/or endophenotype between monkeys and patients suggested that gene-edited RTT founder monkeys would be of value for disease mechanistic studies as well as development of potential therapeutic interventions for RTT
Distribution of polycyclic aromatic hydrocarbons in subcellular root tissues of ryegrass (<it>Lolium multiflorum </it>Lam.)
Abstract Background Because of the increasing quantity and high toxicity to humans of polycyclic aromatic hydrocarbons (PAHs) in the environment, several bioremediation mechanisms and protocols have been investigated to restore PAH-contaminated sites. The transport of organic contaminants among plant cells via tissues and their partition in roots, stalks, and leaves resulting from transpiration and lipid content have been extensively investigated. However, information about PAH distributions in intracellular tissues is lacking, thus limiting the further development of a mechanism-based phytoremediation strategy to improve treatment efficiency. Results Pyrene exhibited higher uptake and was more recalcitrant to metabolism in ryegrass roots than was phenanthrene. The kinetic processes of uptake from ryegrass culture medium revealed that these two PAHs were first adsorbed onto root cell walls, and they then penetrated cell membranes and were distributed in intracellular organelle fractions. At the beginning of uptake ( Conclusions Transpiration and the lipid content of root cell fractions are the main drivers of the subcellular partition of PAHs in roots. Initially, PAHs adsorb to plant cell walls, and they then gradually diffuse into subcellular fractions of tissues. The lipid content of intracellular components determines the accumulation of lipophilic compounds, and the diffusion rate is related to the concentration gradient established between cell walls and cell organelles. Our results offer insights into the transport mechanisms of PAHs in ryegrass roots and their diffusion in root cells.</p
Bacterial diversity losses: A potential extracellular driving mechanism involving the molecular ecological function of hydrophobic polycyclic aromatic hydrocarbons
The DNA transformation is vital to the horizontal gene transfer (HGT). The low-efficiency transformation of bare plasmid exposed to hydrophobic polycyclic aromatic hydrocarbons (PAHs) decreases the gene transfer level, and is possibly related to the loss of bacterial diversity at present. PAHs have great affinity for bare DNA through dispersion force and ĻāĻ overlap between PAHs and bases. These noncovalent interactions between PAHs and bases reduced the transformational efficiency of plasmid into bacterial recipients. Meanwhile these low-efficiency transformations for plasmid are controlled by the ions like Ca2+ in environment, in turn, presence of 0.5Ā mmolĀ Lā1 Ca2+ recovered the efficiency from 3.2 (phenanthrene), 3.5 (pyrene) to about 4.45 and 4.75, respectively. The combination of Ca2+ with the POOā groups in DNA forms strong electrovalent bonds, weakening the molecular effect of DNA on PAHs and in turn promoting the gene transfer exposed to PAHs
Nature and Value of Freely Dissolved EPS Ecosystem Services: Insight into Molecular Coupling Mechanisms for Regulating Metal Toxicity
Extracellular polymeric substances
(EPSs) dispersed in natural
waters play a significant role in relieving impacts to microbial survival
associated with heavy metal release, yet little is known about the
association of freely dissolved EPS ecosystem services with metal
transformation in natural waters. Here, we demonstrate that dispersive
EPSs mitigate the metal toxicity to microbial cells through an associative
coordination reaction. Microtitrimetry coupled with fluorescence spectroscopy
ascribes the combination of freely dissolved EPSs from <i>Escherichia
coli</i> (<i>E. coli</i>) with Cu<sup>2+</sup>/Cd<sup>2+</sup> to a coordination reaction associated with chemical static
quenching. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron
spectroscopy (XPS), and computational chemistry confirm that carboxyl
residues in protein-like substances of the EPSs are responsible for
the coordination. Frontier molecular orbitals (MOs) of a deprotonated
carboxyl integrate with the occupied <i>d</i> orbitals of
Cu<sup>2+</sup> and/or <i>d</i>, <i>s</i> orbitals
of Cd<sup>2+</sup> to form metal-EPS complexes. Microcosmic systems
show that because the metal-EPS complexes decrease cellular absorbability
of metals, <i>E. coli</i> survivals increase by 4.3 times
for Cu<sup>2+</sup> and 1.6 times for Cd<sup>2+</sup>, respectively.
Based on bonding energies for six metals-EPS coordination, an associative
toxic effect further confirms that increased bonding energies facilitate
retardation of metals in the EPS matrix, protecting against <i>E. coli</i> apoptosis
Microbial Extracellular Polymeric Substances Reduce Ag<sup>+</sup> to Silver Nanoparticles and Antagonize Bactericidal Activity
Whereas the antimicrobial mechanisms
of silver have been extensively
studied and exploited for numerous applications, little is known about
the associated bacterial adaptation and defense mechanisms that could
hinder disinfection efficacy or mitigate unintended impacts to microbial
ecosystem services associated with silver release to the environment.
Here, we demonstrate that extracellular polymeric substances (EPS)
produced by bacteria constitute a permeability barrier with reducing
constituents that mitigate the antibacterial activity of silver ions
(Ag<sup>+</sup>). Specifically, manipulation of EPS in Escherichia coli suspensions (e.g., removal of EPS
attached to cells by sonication/centrifugation or addition of EPS
at 200 mg L<sup>ā1</sup>) demonstrated its critical role in
hindering intracellular silver penetration and enhancing cell growth
in the presence of Ag<sup>+</sup> (up to 0.19 mg L<sup>ā1</sup>). High-resolution transmission electron microscopy (HRTEM) combined
with X-ray photoelectron spectroscopy (XPS) and energy-dispersive
spectrometry (EDS) analyses showed that Ag<sup>+</sup> was reduced
to silver nanoparticles (AgNPs; 10ā30 nm in diameter) that
were immobilized within the EPS matrix. Fourier transform infrared
(FTIR) and <sup>13</sup>C nuclear magnetic resonance (NMR) spectra
suggest that Ag<sup>+</sup> reduction to AgNPs by the hemiacetal groups
of sugars in EPS contributed to immobilization. Accordingly, the amount
and composition of EPS produced have important implications on the
bactericidal efficacy and potential environmental impacts of Ag<sup>+</sup>