Construction of algal-bacterial consortia using green microalgae Chlorella vulgaris and As(Ⅲ)-oxidizing bacteria:As tolerance and metabolomic profiling

Bioremediation became a promising technology to resolve arsenic(As)contamination in aquatic environment.Since monoculture such as microalgae or bacteria was sensitive to environmental disturbance and vulnerable to contamination,green microalgae Chlorella vulgaris and arsenite(As(Ⅲ))-oxidizing bacteria Pseudomonas sp.SMS11 were co-cultured to construct algal-bacterial consortia in the current study.The effects of algae-bacteria(A:B)ratio and exposure As(Ⅲ)concentration on algal growth,As speciation and metabolomic profile were investigated.Algal growth arrested when treated with 100 mg/L As(Ⅲ)without the co-cultured bacteria.By contrast,co-cultured with strain SMS11 significantly enhanced As tolerance in C.vulgaris especially with A:B ratio of 1:10.All the As(Ⅲ)in culture media of the consortia were oxidized into As(Ⅴ)on day 7.Methylation of As was observed on day 14.Over 1% and 0.5% of total As were converted into dimethylarsinic acid(DMA)after 21days cultivation when the initial concentrations of As(Ⅲ)were 1 and 10 mg/L,respectively.Metabolomic analysis was further performed to reveal the response of consortia metabolites to external As(Ⅲ).The enriched metabolomic pathways were associated with carbohydrate,amino acid and energy metabolisms.Tricarboxylic acid cycle and glyoxylate and dicarboxylate metabolism were upregulated under As stress due to their biological functions on alleviating oxidative stress and protecting cells.Both carbohydrate and amino acid metabolisms provided precursors and potential substrates for energy production and cell protection under abiotic stress.Alterations of the pathways relevant to carbohydrate or amino acid metabolism were triggered by energy requirement.

Ionome profiling and arsenic speciation provide evidence of arsenite detoxification in rice by phosphate and arsenite-oxidizing bacteria

Arsenite(As(III))as the most toxic and mobile form is the dominant arsenic(As)species in flooded paddy fields,resulting in higher accumulation of As in paddy rice than other terrestrial crops.Mitigation of As toxicity to rice plant is an important way to safeguard food production and safety.In the current study,As(III)-oxidizing bacteria Pseudomonas sp.strain SMS11 was inoculated with rice plants to accelerate conversion of As(III)into lower toxic arsenate(As(V)).Meanwhile,additional phosphate was supplemented to restrict As(V)uptake by the rice plants.Growth of rice plant was significantly inhibited under As(III)stress.The inhibition was alleviated by the introduction of additional P and SMS11.Arsenic speciation showed that additional P restricted As accumulation in the rice roots via competing common uptake pathways,while inoculation with SMS11 limited As translocation from root to shoot.Ionomic profiling revealed specific characteristics of the rice tissue samples from different treatment groups.Compared to the roots,ionomes of the rice shoots were more sensitive to environmental perturbations.Both extraneous P and As(III)-oxidizing bacteria SMS11 could alleviate As(III)stress to the rice plants through promoting growth and regulating ionome homeostasis.

The dynamic changes of arsenic biotransformation and bioaccumulation in muscle of freshwater food fish crucian carp during chronic dietborne exposure

Dietary uptake is the major way that inorganic arsenic(iAs)enters into benthic fish;however,the metabolic process of dietborne i As in fish muscle following chronic exposure remains unclear.This was a 40-day study on chronic dietborne i As[arsenite(AsⅢ)and arsenate(AsⅤ)]exposure in the benthic freshwater food fish,the crucian carp(Carassius auratus),which determined the temporal profiles of iAs metabolism and toxicokinetics during exposure.We found that an adaptive response occurred in the fish body after iAs dietary exposure,which was associated with decreased As accumulation and increased As transformation into a non-toxic As form(arsenobetaine).The bioavailability of dietary AsⅢwas lower than that of AsⅤ,probably because AsⅢhas a lower ability to pass through fish tissues.Dietary AsⅤexhibited a high potential for transformation into AsⅢspecies,which then accumulated in fish muscle.The largely produced AsⅢconsidered more toxic at the earlier stage of AsⅤexposure should attract sufficient attention to human exposure assessment.Therefore,the pristine As species and exposure duration had significant effects on As bioaccumulation and biotransformation in fish.The behavior determined for dietborne arsenic in food fish is crucial for not only arsenic ecotoxicology but also food safety.

A ratiometric fluorescent probe for the detection of hypochlorous acid in living cells and zebra fish with a long wavelength emission

A ratiometric fluorescence probe,NClO,for the rapid and selective detection of HClO had been designed and synthesized based on a 1,8-naphthalimide derivative.Probe NClO displayed a red emission(λmax=615 nm).In the presence of HClO,the solution of probe NClO gave off a strong green fluorescence(λem,max=520 nm)with a rapid response(within seconds).This probe had been applied to image HClO in living cells and zebra fish.

Rational design of a bifunctional fluorescent probe for distinguishing Hcy/Cys from GSH with ideal properties

By pairing two fluoropho res according to their optical prope rties such as absorption spectral overlap and absorptivity,fluorescent quantum yield and emission spectral separation,a bifunctional fluorescent probe,TQBF-NBD,was rationally designed and synthesized to discriminatively sense Hcy/Cys and GSH with good selectivity and sensitivity.It is noted that this probe could work under a single-wave length excitation and displayed a mega-large Stokes shift.TQBF-NBD reacted with Hcy/Cys to give a mixed green-red fluorescence and displayed a red fluorescence upon the treatment with GSH.Distinguishable imaging of intracellular Hcy/Cys from GSH with the help of TQBF-NBD was realized in living cells and zebrafish.