Triclosan (TCS) is a commonly used antimicrobial agent that enters wastewater treatment plants (WWTPs) and the environment. An estimated 1.1 × 10(5) to 4.2 × 10(5) kg of TCS are discharged from these ...WWTPs per year in the United States. The abundance of TCS along with its antimicrobial properties have given rise to concern regarding its impact on antibiotic resistance in the environment. The objective of this review is to assess the state of knowledge regarding the impact of TCS on multidrug resistance in environmental settings, including engineered environments such as anaerobic digesters. Pure culture studies are reviewed in this paper to gain insight into the substantially smaller body of research surrounding the impacts of TCS on environmental microbial communities. Pure culture studies, mainly on pathogenic strains of bacteria, demonstrate that TCS is often associated with multidrug resistance. Research is lacking to quantify the current impacts of TCS discharge to the environment, but it is known that resistance to TCS and multidrug resistance can increase in environmental microbial communities exposed to TCS. Research plans are proposed to quantitatively define the conditions under which TCS selects for multidrug resistance in the environment.
Triclocarban (TCC) is one of the most abundant organic micropollutants detected in biosolids. Lab-scale anaerobic digesters were amended with TCC at concentrations ranging from the background ...concentration of seed biosolids (30 mg/kg) to toxic concentrations of 850 mg/kg to determine the effect on methane production, relative abundance of antibiotic resistance genes, and microbial community structure. Additionally, the TCC addition rate was varied to determine the impacts of acclimation time. At environmentally relevant TCC concentrations (max detect = 440 mg/kg), digesters maintained function. Digesters receiving 450 mg/kg of TCC maintained function under gradual TCC addition, but volatile fatty acid concentrations increased, pH decreased, and methane production ceased when immediately fed this concentration. The concentrations of the mexB gene (encoding for a multidrug efflux pump) were higher with all concentrations of TCC compared to a control, but higher TCC concentrations did not correlate with increased mexB abundance. The relative abundance of the gene tet(L) was greater in the digesters that no longer produced methane, and no effect on the relative abundance of the class 1 integron integrase encoding gene (intI1) was observed. Illumina sequencing revealed substantial community shifts in digesters that functionally failed from increased levels of TCC. More subtle, yet significant, community shifts were observed in digesters amended with TCC levels that did not inhibit function. This research demonstrates that TCC can select for a multidrug resistance encoding gene in mixed community anaerobic environments, and this selection occurs at concentrations (30 mg/kg) that can be found in full-scale anaerobic digesters (U.S. median concentration = 22 mg/kg, mean = 39 mg/kg).
Triclosan (TCS) is a broad-spectrum antimicrobial used in a variety of consumer products. While it was recently banned from hand soaps in the US, it is still a key ingredient in a top-selling ...toothpaste. TCS is a hydrophobic micropollutant that is recalcitrant under anaerobic digestion thereby resulting in high TCS concentrations in biosolids. The objective of this study was to determine the impact of TCS on the antibiotic resistome and potential cross-protection in lab-scale anaerobic digesters using shotgun metagenomics. It was hypothesized that metagenomics would reveal selection for antibiotic resistance genes (ARGs) not previously found in pure culture studies or mixed-culture studies using targeted qPCR. In this study, four different levels of TCS were continuously fed to triplicate lab-scale anaerobic digesters to assess the effect of TCS levels on the antibiotic resistance gene profiles (resistome). Blasting metagenomic reads against antibiotic/metal resistance gene database (BacMet) revealed that ARG diversity and abundance changed along the TCS concentration gradient. While loss of bacterial diversity and digester function were observed in the digester treated with the highest TCS concentration, FabV, which is a known TCS resistance gene, increased in this extremely high TCS environment. The abundance of several other known ARG or metal resistance genes (MRGs), including corA and arsB, also increased as the concentrations of TCS increased. Analysis of other functional genes using SEED database revealed the increase of potentially key genes for resistance including different types of transporters and transposons. These results indicate that antimicrobials can alter the abundance of multiple resistance genes in anaerobic digesters even when function (i.e. methane production) is maintained. This study also suggests that enriched ARGs could be released into environments with biosolids land application.
Display omitted
•ARGs resistomes of anaerobic digesters were altered by TCS additions.•The changes in the resistome were dependent on TCS concentration.•Previously known ARGs, including fabV, were enriched under the highest TCS concentration.•Shotgun metagenomics revealed novel genes potentially involved in TCS resistance.•Novel genes include metal resistance genes, transporters, and mobile elements.
Triclosan selected for metal and antibiotic resistance genes in anaerobic digesters even when function was maintained in the digesters.
Anaerobic digestion is an important biotechnology treatment process for conversion of waste to energy. In this study, a comparative core microbiome approach, i.e., determining taxa that are shared in ...functioning digesters but not shared in non-functioning digesters, was used to determine microbial taxa that could play key roles for effective anaerobic digestion. Anaerobic digester functions were impaired by adding the broad-spectrum antimicrobial triclosan (TCS) or triclocarban (TCC) at different concentrations, and the core microbiomes in both functioning and non-functioning anaerobic digesters were compared. Digesters treated with high (2500 mg/kg) or medium (450 mg/kg) TCS and high (850 mg/kg) TCC concentrations lost their function, i.e., methane production decreased, effluent volatile fatty acid concentrations increased, and pH decreased. Changes in microbial community diversity and compositions were assessed using 16S rRNA gene amplicon sequencing. Microbial richness decreased significantly in non-functioning digesters (
p
< 0.001). Microbial community compositions in non-functioning digesters significantly differed from those in functioning digesters (
p
= 0.001, ANOSIM). Microbes identified as potentially key taxa included previously known fatty acid-degrading syntrophs and amino acid-degrading syntrophs. A diverse group of syntrophs detected in this study had low relative abundance in functioning digesters, suggesting the importance of rare microbes in anaerobic digester operation. The comparative microbiome approach used in this study can be applied to other microbial systems where a community-driven biological phenomena can be observed directly.
Display omitted
•Biorefineries can be designed to recover N, P, and K alongside energy and chemicals.•Low-value waste feedstock is advantageous for conversion to valorized products.•Key nutrient ...products include mixtures, N/P/K precipitates, and single cell protein.•Most agricultural fertilizer needs can be met using nutrients recovered from waste.•N, P, and K recovery from biorefineries alleviates nonrenewable resource extraction.
This review lays the foundation for why nutrient recovery must be a key consideration in design and operation of biorefineries and comprehensively reviews technologies that can be used to recover an array of nitrogen, phosphorus, and/or potassium-rich products of relevance to agricultural applications. Recovery of these products using combinations of physical, chemical, and biological operations will promote sustainability at biorefineries by converting low-value biomass (particularly waste material) into a portfolio of higher-value products. These products can include a natural partnering of traditional biorefinery outputs such as biofuels and chemicals together with nutrient-rich fertilizers. Nutrient recovery not only adds an additional marketable biorefinery product, but also avoids the negative consequences of eutrophication, and helps to close anthropogenic nutrient cycles, thereby providing an alternative to current unsustainable approaches to fertilizer production, which are energy-intensive and reliant on nonrenewable natural resource extraction.
Measuring the structural composition of the cortex is critical to understanding typical development, yet few investigations in humans have charted markers in vivo that are sensitive to tissue ...microstructural attributes. Here, we used a well-validated quantitative MR protocol to measure four parameters (R1, MT, R2*, PD*) that differ in their sensitivity to facets of the tissue microstructural environment (R1, MT: myelin, macromolecular content; R2*: myelin, paramagnetic ions, i.e., iron; PD*: free water content). Mapping these parameters across cortical regions in a young adult cohort (18–39 years, N = 93) revealed expected patterns of increased macromolecular content as well as reduced tissue water content in primary and primary adjacent cortical regions. Mapping across cortical depth within regions showed decreased expression of myelin and related processes – but increased tissue water content – when progressing from the grey/white to the grey/pial boundary, in all regions. Charting developmental change in cortical microstructure cross-sectionally, we found that parameters with sensitivity to tissue myelin (R1 & MT) showed linear increases with age across frontal and parietal cortex (change 0.5–1.0% per year). Overlap of robust age effects for both parameters emerged in left inferior frontal, right parietal and bilateral pre-central regions. Our findings afford an improved understanding of ontogeny in early adulthood and offer normative quantitative MR data for inter- and intra-cortical composition, which may be used as benchmarks in further studies.
•We mapped multi-parameter maps (MPMs) across and within cortical regions.•We charted age effects (ages 18–39) on myelin and related processes.•MPMs sensitive to myelin (R1, MT) showed elevated values in primary areas over most cortical depths.•R2* map foci tended to overlap MPMs sensitive to myelin (R1, MT).•R1 and MT increased with age (0.5–1.0% per year) at mid-depth in frontal and parietal cortex.
Here we report the Joule heating of graphite-based pixel arrays using direct current (DC) power and alternating current (AC) power. We show performance of a DC applicator for scalable heating and ...thermal pattern generation. We demonstrate, for the first time, large-area non-contact heating using microstrip patch antennas operating at 2.45 GHz. We find that the steady-state temperature correlates with the surface conductivity of the individual pixel, and there is an optimum conductivity of the pixel associated with efficient heating in both DC and AC applicators. The applicators developed in this study allow for thermal gradients and patterns by tuning the conductivity of each individual pixel and can be used with any type of carbon-based material such as carbon nanotubes and laser-induced graphene. The applicators could be extended to use for thermal displays, deicing and defrosting, and localized curing of composites. We also demonstrate Joule heating as a useful metric for damage sensing in conductive coatings.
Display omitted
There is an established cross-sectional association between orthostatic hypotension (OH) and late-life depression. The aim of this observational study was to clarify the longitudinal association ...between baseline symptomatic OH (sOH-30) and incident depression in a sample of >3000 older people without baseline depression (mean age62 years at baseline). This study was embedded within the Irish Longitudinal Study on Ageing using data from waves 1 to 3, collected between 2009 and 2014. At 2- and 4-year follow-up, a score ≥9 on the 8-item Center for Epidemiological Studies Depression Scale was used to define incident depression. sOH-30 was defined as a drop in systolic blood pressure ≥20 mm Hg or diastolic blood pressure ≥10 mm Hg at 30 seconds post-standing in conjunction with orthostatic symptoms, such as dizziness, using beat-to-beat measurements. Almost one fifth (proportion, 18%; 95% confidence interval CI, 16–20) of the study sample had sOH-30. One tenth (proportion, 10%; 95% CI, 9–12) had incident depression. Participants with incident depression were twice as likely to have sOH-30 at baseline compared with those without incident depression (linear regression, 13% 95% CI, 8–19 versus 7% 95% CI, 6–8). Weighted logistic regression models demonstrated that sOH-30 predicted incident depression with an odds ratio of 1.90 (95% CI, 1.15–3.15) after controlling for covariates, including subthreshold depression, hypotension, cognitive impairment, and antidepressant use. Asymptomatic OH at 30 seconds and initial OH did not predict depression. This study demonstrates that sOH-30 predicts incident depression in a population-representative sample of older people and may, therefore, represent a potentially modifiable risk factor for late-life depression.
Bench-scale anaerobic digesters were amended to elevated steady-state concentrations of triclosan (850 mg/kg) and triclocarban (150 mg/kg) using a synthetic feed. After more than 9 solids retention ...time (SRT) values of acclimatization, biomass from each digester (and a control digester that received no antimicrobials) was used to assess the toxicity of three antibiotics. Methane production rate was measured as a surrogate for activity in microcosms that received doses of antibiotics ranging from no-antibiotic to inhibitory concentrations. Biomass amended with triclocarban was more sensitive to tetracycline compared to the control indicating synergistic inhibitory effects between this antibiotic and triclocarban. In contrast, biomass amended with triclosan was able to tolerate statistically higher levels of ciprofloxacin indicating that triclosan can induce functional resistance to ciprofloxacin in an anaerobic digester community.
•Antimicrobials can alter anaerobic digester biomass tolerance to antibiotics.•Triclocarban decreased tolerance of biomass to tetracycline (synergistic inhibition).•Triclosan increased tolerance of biomass to ciprofloxacin (cross-resistance).
PDF
