Comparative assessment of bacterial diversity and composition in arsenic hyperaccumulator, Pteris vittata L. and non-accumulator, Pteris ensiformis Burm.

The use of arsenic (As) for various industrial and agricultural applications has led to worldwide environmental contamination. Phytoremediation using hyperaccumulators is a sustainable soil As mitigation strategy. Microbial processes play an important role in the tolerance and uptake of trace elements such as in plants. The rhizospheric and endophytic microbial communities are responsible for accelerating the mobility of trace elements around the roots and the production of plant growth-promoting compounds and enzymes. Several studies have reported that the As hyperaccumulator, Pteris vittata L. (PV) influences the microbial community in its rhizosphere and roots. Deciphering the differences in the microbiomes of hyperaccumulators and non-accumulators is crucial in understanding the mechanism of hyperaccumulation. We hypothesized that there are significant differences in the microbiome of roots, rhizospheric soil, and bulk soil between the hyperaccumulator PV and a non-accumulator of the same genus, Pteris ensiformis Burm. (PE), and that the differential recruitment of bacterial communities provides PV with an advantage in As contaminated soil. We compared root endophytic, rhizospheric, and bulk soil microbial communities between PV and PE species grown in As-contaminated soil in a greenhouse setting. There was a significant difference (p < 0.001) in the microbiome of the three compartments between the ferns. Differential abundance analysis showed 328 Amplicon Sequence Variants (ASVs) enriched in PV compared to 172 in PE. The bulk and rhizospheric soil of both ferns were abundant in As-resistant genera. However, As-tolerant root endophytic genera were present in PV but absent in PE. Our findings show that there is a difference between the bacterial composition of an As hyperaccumulator and a non-accumulator species grown in As-contaminated soil. These differences need to be further explored to develop strategies for improving the efficiency of metal uptake in plants growing in As polluted soil.

Near-infrared rhodol dyes bearing salicylaldehyde moieties for ratiometric pH sensing in live cells during mitophagy and under hypoxia conditions.

We describe a simple but efficient approach to make fluorescent probes A and B based on rhodol dyes incorporated with salicyaldehyde moiety for monitoring pH changes in mitochondria under oxidative stresses and hypoxia conditions, and for tracking mitophagy processes. Probes A and B possess pKa values (pKa ≈ 6.41 and 6.83 respectively) near physiological pH and exhibit decent mitochondria-targeted capabilities, low cytotoxicity, and useful ratiometric and reversible pH responses, which make the probes appropriate for monitoring pH fluctuations of mitochondria in living cells with built-in calibration feature for quantitative analysis. The probes have been effectively useful for the ratiometric determination of pH variations of mitochondria under the stimuli of carbonyl cyanide-4(trifluoromethoxy)phenylhydrazone (FCCP), hydrogen peroxide (H2O2), and N-acetyl cysteine (NAC), and during mitophagy triggered by cell nutrient deprivation, and under hypoxia conditions with cobalt chloride (CoCl2) treatment in living cells. In addition, probe A was efficient in visualizing pH changes in the larvae of fruit flies.

Near-Infrared Fluorescent Probes with Amine-Incorporated Xanthene Platforms for the Detection of Hypoxia.

Three fluorescent probes A, B, and C that function in the near-infrared wavelengths and utilize pseudo xanthene platforms with an oxygen atom at the 10-position replaced by a [Me-N]2- group have been created to identify hypoxia via nitroreductase determinations at the 0.04, 0.10, and 0.19 ng/mL levels. Theoretical calculations suggest that the probes are not planar due to steric interactions. Absorptions of photons result in the transition of electron density from the indoline moieties to delocalized orbitals on the anthranilic section, ending up on the nitro groups of the electron-poor (i.e., nonreduced) probes (i.e., A, B, and C), whereas those for the more electron-rich (i.e., reduced) probes consisted of movement from the indoline groups to the right side of the anthranilic sections, resulting in a shift in absorption.

Ratiometric Detection of Glutathione Based on Disulfide Linkage Rupture between a FRET Coumarin Donor and a Rhodamine Acceptor.

Abnormal levels of glutathione, a cellular antioxidant, can lead to a variety of diseases. We have constructed a near-infrared ratiometric fluorescent probe to detect glutathione concentrations in biological samples. The probe consists of a coumarin donor, which is connected through a disulfide-tethered linker to a rhodamine acceptor. Under the excitation of the coumarin donor at 405 nm, the probe shows weak visible fluorescence of the coumarin donor at 470 nm and strong near-infrared fluorescence of the rhodamine acceptor at 652 nm due to efficient Forster resonance energy transfer (FRET) from the donor to the acceptor. Glutathione breaks the disulfide bond through reduction, which results in a dramatic increase in coumarin fluorescence and a corresponding decrease in rhodamine fluorescence. The probe possesses excellent cell permeability, biocompatibility, and good ratiometric fluorescence responses to glutathione and cysteine with a self-calibration capability. The probe was utilized to ratiometrically visualize glutathione concentration alterations in HeLa cells and Drosophila melanogaster larvae.

Ratiometric Near-Infrared Fluorescent Probes Based on Hemicyanine Dyes Bearing Dithioacetal and Formal Residues for pH Detection in Mitochondria.

Ratiometric near-infrared fluorescent probes (AH+ and BH+) have been prepared for pH determination in mitochondria by attaching dithioacetal and formal residues onto a hemicyanine dye. The reactive formyl group on probe BH+ allows for retention inside mitochondria as it can react with a protein primary amine residue to form an imine under slightly basic pH 8.0. Probes AH+ and BH+ display ratiometric fluorescent responses to pH changes through the protonation and deprotonaton of a hydroxy group in hemicyanine dyes with experimentally determined pKa values of 6.85 and 6.49, respectively. Calculated pKa values from a variety of theoretical methods indicated that the SMDBONDI method of accounting for solvent and van der Waals radii plus including a water molecule located near the site of protonation produced the closest overall agreement with the experimental values at 7.33 and 6.14 for AH+ and BH+ respectively.