Zeolite-supported nanoscale zero-valent iron (Z-NZVI) has great potential for metal(loid) removal, but its encapsulation mechanisms and ecological risks in real soil systems are not completely clear. We conducted long-term incubation experiments to gain new insights into the interactions between metal(loid)s (Cd, Pb, As) and Z-NZVI in naturally contaminated farmland soils, as well as the alteration of indigenous bacterial communities during soil remediation. With the pH-adjusting and adsorption capacities, 30 g kg⁻¹ Z-NZVI amendment significantly decreased the available metal(loid) concentrations by 10.2–96.8% and transformed them into strongly-bound fractions in acidic and alkaline soils after 180 d. An innovative magnetic separation of Z-NZVI from soils followed by XRD and XPS characterizations revealed that B-type ternary complexation, heterogeneous coprecipitation, and/or concurrent redox reactions of metal(loid)s, especially the formation of Cd₃(AsO₄)₂, PbFe₂(AsO₄)₂(OH)₂, and As⁰, occurred only under specific soil conditions. Sequencing of 16S rDNA using Illumina MiSeq platform indicated that temporary shifts in iron-resistant/sensitive, pH-sensitive, denitrifying, and metal-resistant bacteria after Z-NZVI addition were ultimately eliminated because soil characteristics drove the re-establishment of indigenous bacterial community. Meanwhile, Z-NZVI recovered the basic activities of bacterial DNA replication and denitrification functions in soils. These results confirm that Z-NZVI is promising for the long-term remediation of metal(loid)s contaminated farmland soil without significant ecotoxicity.

Bacteria involved with ecosystem N cycling in the rhizosphere of submerged macrophytes are abundant and diverse. Any declines of submerged macrophytes can have a great influence on the abundance and diversity of denitrifying bacteria and anammox bacteria. Natural decline, tardy decline, and sudden decline methods were applied to cultivated Potamogeton crispus. The abundance of anammox bacteria and nirS denitrifying bacteria in rhizosphere sediment were detected using real-time fluorescent quantitative PCR of 16S rRNA, and phylogenetic trees were constructed to analyze the diversities of these two microbes. The results indicated that the concentration of NH₄⁺ in pore water gradually increased with increasing distances from the roots, whereas, the concentration of NO₃⁻ showed a reverse trend. The abundance of anammox bacteria and nirS denitrifying bacteria in sediment of declined P. crispus populations decreased significantly over time. The abundance of these two microbes in the sudden decline group were significantly higher (P > 0.05) than the other decline treatment groups. Furthermore, the abundances of these two microbes were positively correlated, with RDA analyses finding the mole ratio of NH₄⁺/NO₃⁻ being the most important positive factor affecting microbe abundance. Phylogenetic analysis indicated that the anammox bacteria Brocadia fuigida and Scalindua wagneri, and nirS denitrifying bacteria Herbaspirillum and Pseudomonas, were the dominant species in declined P. crispus sediment. We suggest the sudden decline of submerged macrophytes would increase the abundance of anammox bacteria and denitrifying bacteria in a relatively short time.

The urban water ecosystems, such as the landscape ponds are commonly considered under the influence of anthropogenic disturbances, which can lead to the deterioration of the water quality. The prokaryotic communities are considered as one of the best indicators of the water quality. However, there are significant gaps in understanding the ecological processes that shape the composition and function of prokaryotic communities in the urban water ecosystems. Here, we investigated the biogeographic distribution of prokaryotic assemblages in water environments including landscape ponds, drinking water reservoirs, influents (IFs) and effluents (EFs) of wastewater treatment plants of a coastal city (Xiamen), China, by using 16S rDNA amplicon sequencing. Our results indicated that the ponds had higher α-diversity of prokaryotic communities than those in the reservoirs, while there were significant variations in the community compositions among ponds, reservoirs, IFs and EFs. Moreover, ponds harbored a significantly higher proportion of sewage- and fecal-indicator taxa than those in the reservoirs, suggesting the occurrence of exogenous pollution in the urban ponds. Null model analysis revealed that dispersal limitation was the main ecological processes resulting in the divergence of prokaryotic community compositions between ponds and other environments, while dispersal limitation and variable selection played an essential role in the formation of unique prokaryotic assemblages in the reservoirs. Function predication analysis demonstrated that the ponds shared more similar functional profiles with IFs or EFs (e.g., chemoheterotrophy, fermentation, chlorate reducers, nitrate reduction and respiration) than the reservoirs, whereas dominance of photoautotrophy was observed in the reservoirs. Overall, this study provides a profound insight of the ecological mechanisms underlying the responses of prokaryotic communities in the urban landscape ponds to the anthropogenic disturbances.

Ectomycorrhizal (ECM) fungi contribute to the survival of host trees on metal-rich soils by reducing the transfer of toxic metals into roots. However, little is known about the ability of ECM fungi to accumulate elements in ectomycorrhizae (ECMs). Here we report Ag, As, Cd, Cl, Cu, Sb, V, and Zn contents in wild-grown Norway spruce ECMs collected in a smelter-polluted area at Lhota near Příbram, Czech Republic. The ECMs data were compared with the element concentrations determined in the corresponding non-mycorrhizal fine roots, soils, and soil extracts. Bioaccumulation factors were calculated to differentiate the element accumulation ability of ECMs inhabited by different mycobionts, which were identified by ITS rDNA sequencing. Among the target elements, the highest contents were observed for Ag, Cl, Cd, and Zn; Imleria badia ECMs showed the highest capability to accumulate these elements. ECMs of Amanita muscaria, but not of other species, accumulated V. The analysis of the proportions of I. badia and A. muscaria mycelia in ECMs by using species-specific quantitative real-time PCR revealed variable extent of the colonization of roots, with median values close to 5% (w/w). Calculated Ag, Cd, Zn and Cl concentrations in the mycelium of I. badia ECMs were 1 680, 1 510, 2 670, and 37,100 mg kg−1 dry weight, respectively, indicating substantial element accumulation capacity of hyphae of this species in ECMs. Our data strengthen the idea of an active role of ECM fungi in soil-fungal-plant interactions in polluted environments.

Di-(2-ethylhexyl) phthalate (DEHP) has been classified as a priority pollutant which increased the healthy risk to human and animals dramatically. Hence, a novel biochemical system combined by DEHP-resistant bacterial flora (B) and a green oxidant of persulfate (PS) activated by Nano-Fe₃O₄ was applied to degrade DEHP in contaminated soil. In this study, the resistant bacterial flora was screened from activated sludge and immobilized by sodium alginate (SAB). Nano-Fe₃O₄ was coated on biochar (BC@Fe₃O₄) to prevent agglomerating in soil. X-ray diffraction (XRD) and scanning electron microscope (SEM) were utilized to characterize BC@Fe₃O₄. Results demonstrated that the treatment of biochemical system (SAB + BC@Fe₃O₄ + PS) presented the maximum degradation rate about 92.56% within 24 days of incubation and improved soil microecology. The 16S rDNA sequences analysis of soil microorganisms showed a significantly different abundance and a similar diversity among different treatments. Kyoto Encyclopedia of Genes and Genomes (KEGG) functional genes difference analysis showed that some metabolic pathways, such as metabolism of cofactors and vitamins, energy metabolism, cell growth and death, replication and repair, were associated with the biodegradation of DEHP. Besides, DEHP was converted to MEHP and PA by biodegradation, while DEHP was converted to DBP and PA by persulfate and BC@Fe₃O₄, and then ultimately degraded to CO₂ and H₂O.

This study investigated the impact of different environmental particles at different concentrations (0.2% and 2%, w/w) on biodegradation of dibutyl phthalate (DBP) in sediments with and without Cylindrotheca closterium, a marine benthic diatom. The particles included biochar pyrolyzed at 400 °C, multi-walled carbon nanotube (MWNT), nanoscale zero-valent iron (nZVI) and polyethylene microplastic. In treatments without C. closterium, inhibition effect of the particles on degradation percentage of DBP (up to 15.7% decrement except 1.7% increment for 0.2% nZVI) increased with the increase of particle sorption ability to DBP and particle concentration in general. The results of 16s rDNA sequencing showed that C. closterium was probably the most abundant DBP-degrader, accounting for 20.0–49.3% of the total taxon read numbers. In treatments with C. closterium, inoculation of C. closterium increased the degradation percentage of DBP in all treatments with particle addition by 0.0–11.3%, which increased with the increase of chlorophyll a content in general but decreased with the increase of particle concentration from 0.2% to 2%. The increment was the highest for treatment with 0.2% nZVI addition due to its highest promotion effect on algal growth. In contrast, the increment was the lowest for treatments with MWNT addition due to its strong sorption to DBP and strong inhibition on the growth of C. closterium. Our findings suggested that the environmental particles could influence bioavailability of DBP by sorption and biomass of C. closterium, and thus degradation of DBP in sediments.

Environmental health is increasingly compromised by persistent toxic substances, which may have serious implications in food safety and, thus, in human health. Polybrominated diphenyl ethers (PBDEs) are anthropogenic contaminants with endocrine disruption abilities and are commonly found in seafood, the main route of human exposure. Growing evidence points out that the human gut microbiota interacts with xenobiotics, which may lead to impairment of host homeostasis if functions of microbiota become compromised. The aim of this study was to ascertain if the physiological balance of human gut microbiome is affected by the presence and degree of exposure to PBDEs. Fermentation was performed in a batch closed-system using an inoculum made from fresh human stool. The volatolomic profile was analysed by solid-phase microextraction coupled to gas chromatography-mass spectrometry. Mesophilic, Gram-negative bacteria and coliforms were quantified by classic plating methods. Changes in the gut microbiome were evaluated after DNA extraction followed by deep sequencing of the 16S rDNA region. The exposure to PBDEs resulted in an imbalance in sulfur, short-chain fatty acids and aromatic organic compounds, changing the microbial volatolome in a dose- and time-dependent manner. Slight deviations in the microbial structure of human gut occurred in the presence of PBDEs, especially for high doses of exposure. For the first time, the impact of PBDEs on the microbial homeostasis of human gut microbiota was taken into consideration, revealing noteworthy modifications with serious health implications even at oral exposure doses considered as safe by worldwide regulatory entities.

Biological sulfate removal is challenging in cold climates due to the slower metabolism of mesophilic bacteria; however, cold conditions also offer the possibility to isolate bacteria that have adapted to low temperatures. The present research focused on the cold acclimation and characterization of sulfate-reducing bacterial (SRB) consortia enriched from an Arctic sediment sample from northern Finland. Based on 16S rDNA analysis, the most common sulfate-reducing bacterium in all enriched consortia was Desulfobulbus, which belongs to the δ-Proteobacteria. The majority of the cultivated consortia were able to reduce sulfate at temperatures as low as 6 °C with succinic acid as a carbon source. The sulfate reduction rates at 6 °C varied from 13 to 42 mg/L/d. The cultivation medium used in this research was a Postgate medium supplemented with lactate, ethanol or succinic acid. The obtained consortia were able to grow with lactate and succinic acid but surprisingly not with ethanol. Enriched SRB consortia are useful for the biological treatment of sulfate-containing industrial wastewaters in cold conditions.

The continued increase in the global demand for oil, which reached 4,488 Mtoe in 2018, leads to large quantities of petroleum products entering the environment posing serious risks to natural ecosystems if left untreated. In this study, we evaluated the impact of co-contamination with lead on the efficacy of two bioremediation processes, natural attenuation and biostimulation of Total Petroleum Hydrocarbons (TPH) as well as the associated toxicity and the changes in the microbial community in contaminated soils. The biostimulated treatment resulted in 96% and 84% reduction in TPH concentration in a single and a co-contamination scenario, respectively, over 28 weeks of a mesocosm study. This reduction was significantly more in comparison to natural attenuation in a single and a co-contamination scenario, which was 56% and 59% respectively. In contrast, a significantly greater reduction in the associated toxicity of in soils undergoing natural attenuation was evident compared with soils undergoing biostimulation despite the lower TPH degradation when bioassays were applied. The earthworm toxicity test showed a decrease of 72% in the naturally attenuated toxicity versus only 62% in the biostimulated treatment of a single contamination scenario. In a co-contamination scenario, toxicity decreased only 30% and 8% after natural attenuation and biostimulation treatments, respectively. 16s rDNA sequence analysis was used to assess the impact of both the co-contamination and the bioremediation treatment. NGS data revealed major bacterial domination by Nocardioides spp., which reached 40% in week 20 of the natural attenuation treatment. In the biostimulated soil samples, more than 50% of the bacterial community was dominated by Alcanivorax spp. in week 12. The presence of Pb in the natural attenuation treatment resulted in an increased abundance of a few Pb-resistant genera such as Sphingopyxis spp. and Thermomonas spp in addition to Nocardioides spp. In contrast, Pb co-contamination completely shifted the bacterial pattern in the stimulated treatment with Pseudomonas spp. comprising approximately 45% of the bacterial profile in week 12. This study confirms the effectiveness of biostimulation over natural attenuation in remediating TPH and TPH-Pb contaminated soils. In addition, the presence of co-contaminants (e.g. Pb) results in serious impacts on the efficacy of bioremediation of TPH in contaminated soils, which must be considered prior to designing any bioremediation strategy.

The identification of airborne bacteria has traditionally been performed by retrieval in culture media, but the bacterial diversity in the air is underestimated using this method because many bacteria are not readily cultured. Advances in DNA sequencing technology have produced a broad knowledge of genomics and metagenomics, which can greatly improve our ability to identify and study the diversity of airborne bacteria. However, researchers are facing several challenges, particularly the efficient retrieval of low-density microorganisms from the air and the lack of standardized protocols for sample collection and processing. In this study, we tested three methods for sampling bioaerosols — a Durham-type spore trap (Durham), a seven-day recording volumetric spore trap (HST), and a high-throughput 'Jet' spore and particle sampler (Jet) — and recovered metagenomic DNA for 16S rDNA sequencing. Samples were simultaneously collected with the three devices during one week, and the sequencing libraries were analyzed. A simple and efficient method for collecting bioaerosols and extracting good quality DNA for high-throughput sequencing was standardized. The Durham sampler collected preferentially Cyanobacteria, the HST Actinobacteria, Proteobacteria and Firmicutes, and the Jet mainly Proteobacteria and Firmicutes. The HST sampler collected the largest amount of airborne bacterial diversity. More experiments are necessary to select the right sampler, depending on study objectives, which may require monitoring and collecting specific airborne bacteria.