Planktonic and biofilm-grown nitrogen-cycling bacteria exhibit different susceptibilities to copper nanoparticles

Advancements in Nanoparticle-Based Strategies for Enhanced Antibacterial Interventions

The escalating global threat of antibiotic resistance underscores the urgent need for innovative antimicrobial strategies. This review explores the cutting-edge applications of nanotechnology in combating bacterial infections, addressing a critical healthcare challenge. We critically assess the antimicrobial properties and mechanisms of diverse nanoparticle systems, including liposomes, polymeric micelles, solid lipid nanoparticles, dendrimers, zinc oxide, silver, and gold nanoparticles, as well as nanoencapsulated essential oils. These nanomaterials offer distinct advantages, such as enhanced drug delivery, improved bioavailability, and efficacy against antibiotic-resistant strains. Recent advancements in nanoparticle synthesis, functionalization, and their synergistic interactions with conventional antibiotics are highlighted. The review emphasizes biocompatibility considerations, stressing the need for rigorous safety assessments in nanomaterial applications. By synthesizing current knowledge and identifying emerging trends, this review provides crucial insights for researchers and clinicians aiming to leverage nanotechnology for next-generation antimicrobial therapies. The integration of nanotechnology represents a promising frontier in combating infectious diseases, underscoring the timeliness and imperative of this comprehensive analysis.

Black Carbon Impacts on Paraburkholderia xenovorans Strain LB400 Cell Enrichment and Activity: Implications toward Lower-Chlorinated Polychlorinated Biphenyls Biodegradation Potential

Volatilization of lower-chlorinated polychlorinated biphenyls (LC-PCBs) from sediment poses health threats to nearby communities and ecosystems. Biodegradation combined with black carbon (BC) materials is an emerging bioaugmentation approach to remove PCBs from sediment, but development of aerobic biofilms on BC for long-term, sustained LC-PCBs remediation is poorly understood. This work aimed to characterize the cell enrichment and activity of biphenyl- and benzoate-grown Paraburkholderia xenovorans strain LB400 on various BCs. Biphenyl dioxygenase gene (bphA) abundance on four BC types demonstrated corn kernel biochar hosted at least 4 orders of magnitude more attached cells per gram than other feedstocks, and microscopic imaging revealed the attached live cell fraction was >1.5× more on corn kernel biochar than GAC. BC characteristics (i.e., sorption potential, pore size, pH) appear to contribute to cell attachment differences. Reverse transcription qPCR indicated that BC feedstocks significantly influenced bphA expression in attached cells. The bphA transcript-per-gene ratio of attached cells was >10-fold more than suspended cells, confirmed by transcriptomics. RNA-seq also demonstrated significant upregulation of biphenyl and benzoate degradation pathways on attached cells, as well as revealing biofilm formation potential/cell-cell communication pathways. These novel findings demonstrate aerobic PCB-degrading cell abundance and activity could be tuned by adjusting BC feedstocks/attributes to improve LC-PCBs biodegradation potential.

Synthesis of novel metal silica nanoparticles exhibiting antimicrobial potential and applications to combat periodontitis

Periodontitis is a severe form of gum disease caused by bacterial plaque that affects millions of people and has substantial worldwide health and economic implications. However, current clinical antiseptic and antimicrobial drug therapies are insufficient because they frequently have numerous side effects and contribute to widespread bacterial resistance. Recently, nanotechnology has shown promise in the synthesis of novel periodontal therapeutic materials. Nanoparticles are quickly replacing antibiotics in the treatment of bacterial infections, and their potential application in dentistry is immense. The alarming increases in antimicrobial resistance further emphasize the importance of exploring and utilizing nanotechnology in the fight against tooth diseases particularly periodontitis. We developed 16 different combinations of mesoporous silica nanomaterials in this study by ageing, drying, and calcining them with 11 different metals including silver, zinc, copper, gold, palladium, ruthenium, platinum, nickel, cerium, aluminium, and zirconium. The antibacterial properties of metal-doped silica were evaluated using four distinct susceptibility tests. The agar well diffusion antibacterial activity test, which measured the susceptibility of the microbes being tested, as well as the antibacterial efficacy of mesoporous silica with different silica/metal ratios, were among these studies. The growth kinetics experiment was used to investigate the efficacy of various metal-doped silica nanoparticles on microbial growth. To detect growth inhibitory effects, the colony-forming unit assay was used. Finally, MIC and MBC tests were performed to observe the inhibition of microbial biofilm formation. Our findings show that silver- and zinc-doped silica nanoparticles synthesized using the sol-gel method can be effective antimicrobial agents against periodontitis-causing microbes. This study represents the pioneering work reporting the antimicrobial properties of metal-loaded TUD-1 mesoporous silica, which could be useful in the fight against other infectious diseases too.

Application of CNN and ANN in assessment the effect of chemical components of biological nanomaterials in treatment of infection of inner ear and environmental sustainability

Nanoparticles (NPs) are a promising alternative to antibiotics for targeting microorganisms, especially in the case of difficult-to-treat bacterial illnesses. Antibacterial coatings for medical equipment, materials for infection prevention and healing, bacterial detection systems for medical diagnostics, and antibacterial immunizations are potential applications of nanotechnology. Infections in the ear, which can result in hearing loss, are extremely difficult to cure. The use of nanoparticles to enhance the efficacy of antimicrobial medicines is a potential option. Various types of inorganic, lipid-based, and polymeric nanoparticles have been produced and shown beneficial for the controlled administration of medication. This article focuses on the use of polymeric nanoparticles to treat frequent bacterial diseases in the human body. Using machine learning models such as artificial neural networks (ANNs) and convolutional neural networks (CNNs), this 28-day study evaluates the efficacy of nanoparticle therapy. An innovative application of advanced CNNs, such as Dense Net, for the automatic detection of middle ear infections is reported. Three thousand oto-endoscopic images (OEIs) were categorized as normal, chronic otitis media (COM), and otitis media with effusion (OME). Comparing middle ear effusions to OEIs, CNN models achieved a classification accuracy of 95%, indicating great promise for the automated identification of middle ear infections. The hybrid CNN-ANN model attained an overall accuracy of more than 0.90 percent, with a sensitivity of 95 percent and a specificity of 100 percent in distinguishing earwax from illness, and provided nearly perfect measures of 0.99 percent. Nanoparticles are a promising treatment for difficult-to-treat bacterial diseases, such as ear infections. The application of machine learning models, such as ANNs and CNNs, can improve the efficacy of nanoparticle therapy, especially for the automated detection of middle ear infections. Polymeric nanoparticles, in particular, have shown efficacy in treating common bacterial infections in children, indicating great promise for future treatments.

Pristine and sulfidized ZnO nanoparticles alter microbial community structure and nitrogen cycling in freshwater lakes

Zinc oxide nanoparticles (ZnO NPs) and its sulfidized form (ZnS NPs) are increasingly entering into freshwater systems through multiple pathways. However, their impacts on the composition and function of sedimentary microbial communities are still largely unknown. Here, two kinds of lake-derived microcosms were constructed and incubated with ZnO NPs, or ZnS NPs to investigate the short-term (7 days) and long-term (50 days) impacts on sedimentary microbial communities and nitrogen cycling. After 7 days, both ZnO NPs and ZnS NPs dosed microbial communities experienced distinct alterations as compared to the undosed controls. By day 50, the structural shifts of microbial communities caused by ZnO NPs were significantly enlarged, while the microbial shifts induced by ZnS NPs were largely resolved. Additionally, ZnO NPs and ZnS NPs could significantly alter nitrogen species and nitrogen cycling genes in sediments, revealing their non-negligible impacts on nitrogen cycling processes. Furthermore, our data clearly indicated that the impacts of ZnO NPs and ZnS NPs on nitrogen cycling differed distinctly in different lake-derived microcosms, and the impacts were significantly correlated with microbial community structure. Overall, this research suggests that the entrance of pristine or sulfidized ZnO NPs into freshwater systems may significantly impact the sedimentary microbial community structure and nitrogen cycling.

Inactivation of Staphylococcus aureus and Escherichia coli Biofilms by Air-Based Atmospheric-Pressure DBD Plasma

Air-based atmospheric-pressure plasma is an effective non-thermal method in deactivating various kinds of microbial biofilms with several advantages, including high bactericidal efficiency and low treatment costs. Bacterial biofilm formation is a major determinant in establishment of bacterial infection and also resistance to antibacterial chemotherapy. This study aims to assess the anti-biofilm potential of air-based atmospheric-pressure DBD plasma against Staphylococcus aureus and Escherichia coli biofilms. The biofilms of Staphylococcus aureus and Escherichia coli were exposed to air-based atmospheric-pressure DBD plasma for up to 4 min (control, 30 s, 90 s, 3 min, and 4 min) and their biofilm formation level, viability, and membrane integrity were determined. Based on the results, plasma exposure caused disruption up to 70% and 85% for S. aureus and E. coli biofilms, respectively. The biofilm disruption potential of air-based atmospheric-pressure DBD plasma was confirmed using the scanning electron microscopy (SEM). Besides, based on confocal laser scanning microscopy (CLSM), plasma exposure caused a significant bacterial inactivation and E. coli was found as more susceptible strain than S. aureus. In conclusion, atmospheric-pressure DBD plasma could be considered an efficient non-thermal approach against bacterial pathogenicity by biofilm disruption and thus prevention of infection establishment.

Anaerobic fermentation metabolism of Moorella thermoacetica inhibited by copper nanoparticles: Comprehensive analyses of transcriptional response and enzyme activity

Engineered nanoparticles are observed to be released into the environment and ended up in wastewater treatment plants. It has been reported that these nanoparticles in sewage might have a toxic effect on microorganisms, and thus affect anaerobic microbial fermentation. However, the mechanisms involved in nanoparticles-induced effects on the anaerobic acidification process and its related bacterial metabolism are still unclear. This work indicated that copper nanoparticles (Cu NPs) were able to cause cell membrane oxidative damage and inhibit the growth and metabolism of Moorella thermoacetica (a model acetogen). The OD₆₀₀ and acetic acid production of M. thermoacetica in the presence of 1 mg/L of Cu NPs were decreased to 29.2% and 40.7% of the control, respectively. The key mechanism of the inhibitory effect was governed by the fact that Cu NPs significantly reduced the glucose consumption, and led to the decreased pyruvate metabolism levels. Additionally, Cu NPs inhibited the gene expressions and catalytic activities of the key enzymes related to acetic acid production. It was identified that the relative activities of phosphofructokinase, pyruvate kinase, phosphotransacetylase, and acetate kinase of M. thermoacetica in the presence of 1 mg/L of Cu NPs decreased to only 70.1%, 69.3%, 50.1%, and 65.2% of the control, respectively. These results demonstrated that the release of Cu NPs in the environment could pose risks to anaerobic fermentation processes via regulating microbial transcriptional response and enzyme activity.

A mechanistic perspective on targeting bacterial drug resistance with nanoparticles

Bacterial infections are an important cause of mortality worldwide owing to the prevalence of drug resistant bacteria. Bacteria develop resistance against antimicrobial drugs by several mechanisms such as enzyme inactivation, reduced cell permeability, modifying target site or enzyme, enhanced efflux because of high expression of efflux pumps, biofilm formation or drug-resistance gene expression. New and alternative ways such as nanoparticle (NP) applications are being established to overcome the growing multidrug-resistance in bacteria. NPs have unique antimicrobial characteristics that make them appropriate for medical application to overcome antibiotic resistance. The proposed antibacterial mechanisms of NPs are cell membrane damage, changing cell wall penetration, reactive oxygen species (ROS) production, effect on DNA and proteins, and impact on biofilm formation. The present review mainly focuses on discussing various mechanisms of bacterial drug resistance and the applications of NPs as alternative antibacterial systems. Combination therapy of NPs and antibiotics as a novel approach in medicine towards antimicrobial resistance is also discussed.

Aluminium oxide nanoparticles inhibit EPS production, adhesion and biofilm formation by multidrug resistant Acinetobacter baumannii

Acinetobacter baumannii is a biofilm forming multidrug resistant (MDR) pathogen responsible for respiratory tract infections. In this study, aluminium oxide nanoparticles (Al₂O₃ NPs) were synthesized and characterized by TEM and EDX and shown to be spherical shaped nanoparticles with a diameter < 10 nm. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) for the Al₂O₃ NPs ranged between 125 and 1,000 µg ml^-1. Exposure to NPs caused cellular membrane disruption, indicated by an increase in cellular leakage of the contents. Biofilm inhibition was 11.64 to 70.2%, whereas attachment of bacteria to polystyrene surfaces was reduced to 48.8 to 51.9% in the presence of NPs. Nanoparticles also reduced extracellular polymeric substance production and the biomass of established biofilms. The data revealed the non-toxic nature of Al₂O₃ NPs up to a concentrations of 120 µg ml^-1 in HeLa cell lines. These results demonstrate an effective and safer use of Al₂O₃ NPs against the MDR A. baumannii by targeting biofilm formation, adhesion and EPS production.

Short term changes in the abundance of nitrifying microorganisms in a soil-plant system simultaneously exposed to copper nanoparticles and atrazine

Copper nanoparticles (NCu) may co-exist with other pollutants in agricultural soils, such as pesticides. However, this has been little evaluated yet. Thus, possible effects of the simultaneous applications of pesticides and NCu on biogeochemical cycles are expected, for example on the nitrogen cycle. Therefore, the aim of this work was to evaluate the effect of simultaneous application of the herbicide atrazine (ATZ) and NCu on the abundance of total bacteria and nitrifying communities: ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). Moreover, the ATZ dissipation was evaluated. A soil-plant system containing ATZ at field dose (3 mg a.i. kg^-1) was mixed with two doses of NCu (0.05% or 0.15% w/w). Changes in the abundance of 16S rRNA and ammonia monooxygenase (amoA) genes of AOA and AOB were evaluated by real-time quantitative PCR (qPCR) at three sampling times (1, 15 and 30 days). The residual ATZ and nitrate production were also measured. The results showed significant differences in microbial composition and abundance over the 30 days of the experiment. Particularly, an initial decrease was observed in total bacterial abundance due to the presence of ATZ and NCu respect to ATZ alone (~60%). The abundance of AOA was also remarkably reduced (~85%), but these communities gradually recovered towards the end of the experiment. Conversely, AOB abundance initially increased (>100%) and remained mainly unaltered in soil exposed to ATZ and NCu 0.15% w/w, where nitrate formation was also constant. Moreover, NCu decreased the ATZ dissipation, which was translated in a 2-fold increase on the ATZ half-life values (T_1/2). This study demonstrates that the simultaneous presence of NCu and ATZ may represent a risk for the total bacteria present in soil and sensitive microorganisms such as nitrifying communities, and changes in the dissipation of the pesticide could influence this process.

Size-dependent cytotoxicity of silver nanoparticles to Azotobacter vinelandii: Growth inhibition, cell injury, oxidative stress and internalization

The influence of nanomaterials on the ecological environment is becoming an increasingly hot research field, and many researchers are exploring the mechanisms of nanomaterial toxicity on microorganisms. Herein, we studied the effect of two different sizes of nanosilver (10 nm and 50 nm) on the soil nitrogen fixation by the model bacteria Azotobacter vinelandii. Smaller size AgNPs correlated with higher toxicity, which was evident from reduced cell numbers. Flow cytometry analysis further confirmed this finding, which was carried out with the same concentration of 10 mg/L for 12 h, the apoptotic rates were20.23% and 3.14% for 10 nm and 50 nm AgNPs, respectively. Structural damage to cells were obvious under scanning electron microscopy. Nitrogenase activity and gene expression assays revealed that AgNPs could inhibit the nitrogen fixation of A. vinelandii. The presence of AgNPs caused intracellular reactive oxygen species (ROS) production and electron spin resonance further demonstrated that AgNPs generated hydroxyl radicals, and that AgNPs could cause oxidative damage to bacteria. A combination of Ag content distribution assays and transmission electron microscopy indicated that AgNPs were internalized in A. vinelandii cells. Overall, this study suggested that the toxicity of AgNPs was size and concentration dependent, and the mechanism of antibacterial effects was determined to involve damage to cell membranes and production of reactive oxygen species leading to enzyme inactivation, gene down-regulation and death by apoptosis.

Differential Sensitivity of Wetland-Derived Nitrogen Cycling Microorganisms to Copper Nanoparticles

Metallic nanoparticles (NPs), the most abundant nanomaterials in consumer and industrial products, are the most probable class to enter the environment. In this study, wetland-derived microcosms were incubated with copper nanoparticles (Cu-NP) and ionic CuCl₂ to investigate acute (10 days) and chronic (100 days) exposure towards nitrogen cycling microorganisms. The microbial ecology of wetlands play a crucial role in balancing nitrogen in pristine environments as well as in areas impacted by high nutrient loads (e.g., at wastewater effluent discharges). Gene abundance and expression changes were monitored using the GeoChip 5.0 high throughput functional gene microarray and metatranscriptomic shotgun sequencing (RNA-seq), respectively. After 10 days, the Cu-NP impacted microbial communities experienced structural shifts within microorganisms associated with dissimilatory nitrogen reduction accompanied by lower nitrate removal as compared to the unexposed controls. By day 100, these differences were largely resolved and nitrate removal was similar to the unexposed control. Furthermore, the Cu-NP exposed microcosms tolerated copper and were more resilient and adaptive than the unexposed controls based on the abundance and expression of other functions, including electron transfer, metal homeostasis, and stress response. These findings suggest sudden influxes of Cu-NPs into wetland systems may impair nitrogen removal initially, but long-term microbial shifts and functional redundancy would promote the net flux of total nitrogen out of the wetlands.

Abiotic and bioaugmented granular activated carbon for the treatment of 1,4-dioxane-contaminated water

1,4-Dioxane is a probable human carcinogen and an emerging contaminant that has been detected in surface water and groundwater resources. Many conventional water treatment technologies are not effective for the removal of 1,4-dioxane due to its high water solubility and chemical stability. Biological degradation is a potentially low-cost, energy-efficient approach to treat 1,4-dioxane-contaminated waters. Two bacterial strains, Pseudonocardia dioxanivorans CB1190 (CB1190) and Mycobacterium austroafricanum JOB5 (JOB5), have been previously demonstrated to break down 1,4-dioxane through metabolic and co-metabolic pathways, respectively. However, both CB1190 and JOB5 have been primarily studied in laboratory planktonic cultures, while most environmental microbes grow in biofilms on surfaces. Another treatment technology, adsorption, has not historically been considered an effective means of removing 1,4-dioxane due to the contaminant's low K_oc and K_ow values. We report that the granular activated carbon (GAC), Norit 1240, is an adsorbent with high affinity for 1,4-dioxane as well as physical dimensions conducive to attached bacterial growth. In abiotic batch reactor studies, 1,4-dioxane adsorption was reversible to a large extent. By bioaugmenting GAC with 1,4-dioxane-degrading microbes, the adsorption reversibility was minimized while achieving greater 1,4-dioxane removal when compared with abiotic GAC (95-98% reduction of initial 1,4-dioxane as compared to an 85-89% reduction of initial 1,4-dioxane, respectively). Bacterial attachment and viability was visualized using fluorescence microscopy and confirmed by amplification of taxonomic genes by quantitative polymerase chain reaction (qPCR) and an ATP assay. Filtered samples of industrial wastewater and contaminated groundwater were also tested in the bioaugmented GAC reactors. Both CB1190 and JOB5 demonstrated 1,4-dioxane removal greater than that of the abiotic adsorbent controls. This study suggests that bioaugmented adsorbents could be an effective technology for 1,4-dioxane removal from contaminated water resources.

Effects of short- and long-term exposure of silver nanoparticles and silver ions to Nitrosomonas europaea biofilms and planktonic cells

The increasing use of silver nanoparticles (AgNPs) in consumer products, and their resulting influx into wastewater, may pose a threat to biological nutrient removal in wastewater treatment plants. Planktonic ammonia-oxidizing bacteria (AOB), which convert ammonia to nitrite in the first step of nitrification, are highly sensitive to AgNPs and their released silver ions (Ag⁺), but the sensitivity of AOB biofilms to AgNPs and Ag⁺ is less clear. This study demonstrated that biofilms of Nitrosomonas europaea, a model AOB, were more resistant to both short-term and long-term exposure to AgNP and Ag⁺ than planktonic cells. The increased resistance of N. europaea biofilms was attributed primarily to the increased biomass and slower growth rates present in the biofilm. Similar inhibition mechanisms were observed for AgNPs and Ag⁺ in both planktonic cells and biofilms with enzymatic inhibition observed at lower concentrations and cell lysis observed at higher concentrations. Long-term continuous exposure to AgNPs lowered the inhibitory concentration by 1-2 orders of magnitude below that required by short-term exposures. Although the total AgNP load was similar between the short and long-term exposure scenarios, the long-term exposure resulted in an order of magnitude more silver being associated in the biofilms and is the primary reason for the increased sensitivity observed. This suggests that short-term batch toxicity assays may greatly underestimate the sensitivity of biofilm treatment systems to long-term exposures of low concentrations of AgNPs and Ag⁺.

The antimicrobial activity of nanoparticles: present situation and prospects for the future

Nanoparticles (NPs) are increasingly used to target bacteria as an alternative to antibiotics. Nanotechnology may be particularly advantageous in treating bacterial infections. Examples include the utilization of NPs in antibacterial coatings for implantable devices and medicinal materials to prevent infection and promote wound healing, in antibiotic delivery systems to treat disease, in bacterial detection systems to generate microbial diagnostics, and in antibacterial vaccines to control bacterial infections. The antibacterial mechanisms of NPs are poorly understood, but the currently accepted mechanisms include oxidative stress induction, metal ion release, and non-oxidative mechanisms. The multiple simultaneous mechanisms of action against microbes would require multiple simultaneous gene mutations in the same bacterial cell for antibacterial resistance to develop; therefore, it is difficult for bacterial cells to become resistant to NPs. In this review, we discuss the antibacterial mechanisms of NPs against bacteria and the factors that are involved. The limitations of current research are also discussed.

Biofilms Versus Activated Sludge: Considerations in Metal and Metal Oxide Nanoparticle Removal from Wastewater

The increasing application of metal and metal oxide nanoparticles [Me(O)NPs] in consumer products has led to a growth in concentration of these nanoparticles in wastewater as emerging contaminants. This may pose a threat to ecological communities (e.g., biological nutrient removal units) within treatment plants and those subject to wastewater effluents. Here, the toxicity, fate, and process implications of Me(O)NPs within wastewater treatment, specifically during activated sludge processing and biofilm systems are reviewed and compared. Research showed activated sludge achieves high removal rate of Me(O)NPs by the formation of aggregates through adsorption. However, recent literature reveals evidence that inhibition is likely for nutrient removal capabilities such as nitrification. Biofilm systems were much less studied, but show potential to resist Me(O)NP inhibition and achieve removal through possible retention by sorption. Implicating factors during bacteria-Me(O)NP interactions such as aggregation, surface functionalization, and the presence of organics are summarized. At current modeled levels, neither activated sludge nor biofilm systems can achieve complete removal of Me(O)NPs, thus allowing for long-term environmental exposure of diverse biological communities to Me(O)NPs in streams receiving wastewater effluents. Future research directions are identified throughout in order to minimize the impact of these nanoparticles released.

Copper status of exposed microorganisms influences susceptibility to metallic nanoparticles

Although interactions of metallic nanoparticles (NPs) with various microorganisms have been previously explored, few studies have examined how metal sensitivity impacts NP toxicity. The present study investigated the effects of copper NPs (Cu-NP) exposure on the model alga Chlamydomonas reinhardtii in the presence and absence of the essential micronutrient copper. The toxic ranges for Cu-NPs and the ionic control, CuCl2 , were determined using a high-throughput adenosine triphosphate (ATP)-based fluorescence assay. The Cu-NPs caused similar mortality in copper-replete and copper-deplete cells (median inhibitory concentration [IC50]: 14-16 mg/L) but were less toxic than the ionic control, CuCl2 (IC50: 7 mg/L). Using this concentration range, the Cu-NP impacts on cell morphology, copper accumulation, chlorophyll content, and expression of stress genes under both copper supply states were assessed. Osmotic swelling, membrane damage, and chloroplast and organelle disintegration were observed by transmission electron microscopy at both conditions. Despite these similarities, copper-deplete cells showed greater accumulation of loosely bound and tightly bound copper after exposure to Cu-NPs. Furthermore, copper-replete cells experienced greater loss of chlorophyll content, 19% for Cu-NPs, compared with only an 11% net decrease in copper-deplete cells. The tightly bound copper was bioavailable as assessed by reverse-transcriptase quantitative polymerase chain reaction analysis of CYC6, a biomarker for Cu deficiency. The increased resistance of copper-deplete cells to Cu-NPs suggests that these cells potentially metabolize excess Cu-NPs or better manage sudden influxes of ions. The results suggest that toxicity assessments must account for the nutritional status of impacted organisms and use toxicity models based on estimations of the bioavailable fractions.

Impacts of Pristine and Transformed Ag and Cu Engineered Nanomaterials on Surficial Sediment Microbial Communities Appear Short-Lived

Laboratory-based studies have shown that many soluble metal and metal oxide engineered nanomaterials (ENM) exert strong toxic effects on microorganisms. However, laboratory-based studies lack the complexity of natural systems and often use "as manufactured" ENMs rather than more environmentally relevant transformed ENMs, leaving open the question of whether natural ligands and seasonal variation will mitigate ENM impacts. Because ENMs will accumulate in subaquatic sediments, we examined the effects of pristine and transformed Ag and Cu ENMs on surficial sediment microbial communities in simulated freshwater wetlands. Five identical mesocosms were dosed through the water column with either Ag(0), Ag2S, CuO or CuS ENMs (nominal sizes of 4.67 ± 1.4, 18.1 ± 3.2, 31.1 ± 12, and 12.4 ± 4.1, respectively) or Cu(2+). Microbial communities were examined at 0, 7, 30, 90, 180, and 300 d using qPCR and high-throughput 16S rRNA gene sequencing. Results suggest differential short-term impacts of Ag(0) and Ag2S, similarities between CuO and CuS, and differences between Cu ENMs and Cu(2+). PICRUSt-predicted metagenomes displayed differential effects of Ag treatments on photosynthesis and of Cu treatments on methane metabolism. By 300 d, all metrics pointed to reconvergence of ENM-dosed mesocosm microbial community structure and composition, suggesting that the long-term microbial community impacts from a pulse of Ag or Cu ENMs are limited.

Nanoparticles vs. biofilms: a battle against another paradigm of antibiotic resistance

Microbes form surface-adherent community structures called biofilms and these biofilms play a critical role in infection.