Emerging threat: Antimicrobial resistance proliferation during epidemics - A case study of the SARS-CoV-2 pandemic in South Brazil.

The escalating global concern of antimicrobial resistance poses a significant challenge to public health. This study delved into the occurrence of resistant bacteria and antimicrobial resistance genes in the waters and sediments of urban rivers and correlated this emergence and the heightened use of antimicrobials during the COVID-19 pandemic. Isolating 45 antimicrobial-resistant bacteria across 11 different species, the study identifies prevalent resistance patterns, with ceftriaxone resistance observed in 18 isolates and ciprofloxacin resistance observed in 13 isolates. The detection of extended-spectrum ß-lactamases, carbapenemases, and acquired quinolone resistance genes in all samples underscores the gravity of the situation. Comparison with a pre-pandemic study conducted in the same rivers in 2019 reveals the emergence of previously undetected new resistant species, and the noteworthy presence of new resistant species and alterations in resistance profiles among existing species. Notably, antimicrobial concentrations in rivers increased during the pandemic, contributing significantly to the scenario of antimicrobial resistance observed in these rivers. We underscore the substantial impact of heightened antimicrobial usage during epidemics, such as COVID-19, on resistance in urban rivers. It provides valuable insights into the complex dynamics of antimicrobial resistance in environmental settings and calls for comprehensive approaches to combat this pressing global health issue, safeguarding both public and environmental health.

Locomotion behavior testing as a complementary tool in Collembola avoidance assays with neurotoxic insecticides.

This study aimed (1) to assess the ability of collembolans Folsomia candida to avoid soils contaminated with three seed dressing insecticides imidacloprid, clothianidin, and fipronil; (2) to assess the effects of the insecticides on collembolans' locomotion behavior; (3) to check if changes in the locomotion behavior would explain the avoidance/preference responses; and (4) to evaluate the possibility to use locomotion behavior as toxicity biomarker of the tested insecticides. Avoidance and locomotion behavior assays with collembolans F. candida were performed with commercial seed dressing formulations of three insecticides (imidacloprid, clothianidin, and fipronil). Results showed no avoidance behavior at any concentration, while a "preference" was observed with increasing concentrations of the three tested insecticides. Significant reductions in the locomotion of exposed collembolans were observed at ≥ 1 mg kg-1 for imidacloprid (18-38%) and fipronil (29-58%) and ≥ 4 mg kg-1 for clothianidin (10-47%). At the higher insecticide concentrations, the collembolans had their trajectories restricted to smaller areas, with a tendency for circular movements. Our results confirm that the "preference" for contaminated soils with neurotoxic substances is likely due to locomotion inhibition impairing the ability of organisms to escape. This effect highlights that only avoidance assays may be not sufficient to assure the safety of some substances and confirm the potential of locomotion behavior as a sensitive toxicity biomarker for neurotoxic insecticides.

Responses to herbicides of Arctic and temperate microalgae grown under different light intensities.

In aquatic ecosystems, microalgae are exposed to light fluctuations at different frequencies due to daily and seasonal changes. Although concentrations of herbicides are lower in Arctic than in temperate regions, atrazine and simazine, are increasingly found in northern aquatic systems because of long-distance aerial dispersal of widespread applications in the south and antifouling biocides used on ships. The toxic effects of atrazine on temperate microalgae are well documented, but very little is known about their effects on Arctic marine microalgae in relation to their temperate counterparts after light adaptation to variable light intensities. We therefore investigated the impacts of atrazine and simazine on photosynthetic activity, PSII energy fluxes, pigment content, photoprotective ability (NPQ), and reactive oxygen species (ROS) content under three light intensities. The goal was to better understand differences in physiological responses to light fluctuations between Arctic and temperate microalgae and to determine how these different characteristics affect their responses to herbicides. The Arctic diatom Chaetoceros showed stronger light adaptation capacity than the Arctic green algae Micromonas. Atrazine and simazine inhibited the growth and photosynthetic electron transport, affected the pigment content, and disturbed the energy balance between light absorption and utilization. As a result, during high light adaptation and in the presence of herbicides, photoprotective pigments were synthesized and NPQ was highly activated. Nevertheless, these protective responses were insufficient to prevent oxidative damage caused by herbicides in both species from both regions, but at different extent depending on the species. Our study demonstrates that light is important in regulating herbicide toxicity in both Arctic and temperate microalgal strains. Moreover, eco-physiological differences in light responses are likely to support changes in the algal community, especially as the Arctic ocean becomes more polluted and bright with continued human impacts.

COVID-19 pharmaceuticals in aquatic matrices: The threatening effects over cyanobacteria and microalgae.

Water contamination by pharmaceuticals is a global concern due to their potential negative effects on aquatic ecosystems and human health. This study examined the presence of three repositioned drugs used for COVID-19 treatment: azithromycin (AZI), ivermectin (IVE) and hydroxychloroquine (HCQ) in water samples collected from three urban rivers in Curitiba, Brazil, during August and September 2020. We conducted a risk assessment and evaluated the individual (0, 2, 4, 20, 100 and 200 µg.L-1) and combined (mix of the drugs at 2 µg.L-1) effects of the antimicrobials on the cyanobacterium Synechococcus elongatus and microalga Chlorella vulgaris. The liquid chromatography coupled to mass spectrometry results showed that AZI and IVE were present in all collected samples, while HCQ occurred in 78 % of them. In all the studied sites, the concentrations found of AZI (up to 2.85 µg.L-1) and HCQ (up to 2.97 µg.L-1) represent environmental risks for the studied species, while IVE (up to 3.2 µg.L-1) was a risk only for Chlorella vulgaris. The hazard quotients (HQ) indices demonstrated that the microalga was less sensitive to the drugs than the cyanobacteria. HCQ and IVE had the highest values of HQ for the cyanobacteria and microalga, respectively, being the most toxic drugs for each species. Interactive effects of drugs were observed on growth, photosynthesis and antioxidant activity. The treatment with AZI + IVE resulted in cyanobacteria death, while exposure to the mixture of all three drugs led to decreased growth and photosynthesis in the cells. On the other hand, no effect on growth was observed for C. vulgaris, although photosynthesis has been negatively affected by all treatments. The use of AZI, IVE and HCQ for COVID-19 treatment may have generated surface water contamination, which could increased their potential ecotoxicological effects. This raises the need to further investigation into their effects on aquatic ecosystems.

The phytoremediation capacity of Lemna minor prevents deleterious effects of anti-HIV drugs to nontarget organisms.

We investigated physiological responses of Lemna minor plants and their capacity to remove tenofovir (TNF; 412 ng l-1), lamivudine (LMV; 5428 ng l-1) and/or efavirenz (EFV; 4000 ng l-1) from water through phytoremediation. In addition, the toxicological safety of water contaminated with these drugs after treatment with L. minor plants to photosynthetic microorganisms (Synechococcus elongatus and Chlorococcum infusionum) was evaluated. The tested environmental representative concentrations of drugs did not have a toxic effect on L. minor, and their tolerance mechanisms involved an increase in the activity of P450 and antioxidant enzymes (catalase and ascorbate peroxidase). L. minor accumulated significant quantities of TNF, LMV and EFV from the media (>70%), and the interactive effect of LMV and EFV increased EFV uptake by plants submitted to binary or tertiary mixture of drugs. Photosynthetic microorganisms exposed to TNF + LMV + EFV showed toxicological symptoms which were not observed when exposed to contaminated water previously treated with L. minor. An increased H2O2 concentrations but no oxidative damage in S. elongatus cells exposed to non-contaminated water treated with L. minor was observed. Due to its capacity to tolerate and reclaim anti-HIV drugs, L. minor plants must be considered in phytoremediation programs. They constitute a natural-based solution to decrease environmental contamination by anti-HIV drugs and toxicological effects of these pharmaceuticals to nontarget organisms.

Unique microbiome in organic matter-polluted urban rivers.

Approximately half of the global annual production of wastewater is released untreated into aquatic environments, which results in worldwide organic matter pollution in urban rivers, especially in highly populated developing countries. Nonetheless, information on microbial community assembly and assembly-driving processes in organic matter-polluted urban rivers remains elusive. In this study, a field study based on water and sediment samples collected from 200 organic matter-polluted urban rivers of 82 cities in China and Indonesia is combined with laboratory water-sediment column experiments. Our findings demonstrate a unique microbiome in these urban rivers. Among the community assembly-regulating factors, both organic matter and geographic conditions play major roles in determining prokaryotic and eukaryotic community assemblies, especially regarding the critical role of organic matter in regulating taxonomic composition. Using a dissimilarity-overlap approach, we found universality in the dynamics of water and sediment community assembly in organic matter-polluted urban rivers, which is distinctively different from patterns in eutrophic and oligotrophic waters. The prokaryotic and eukaryotic communities are dominated by deterministic and stochastic processes, respectively. Interestingly, water prokaryotic communities showed a three-phase cyclic succession of the community assembly process before, during, and after organic matter pollution. Our study provides the first large-scale and comprehensive insight into the prokaryotic and eukaryotic community assembly in organic matter-polluted urban rivers and supports their future sustainable management.

Pesticide responses of Arctic and temperate microalgae differ in relation to ecophysiological characteristics.

Polar ecosystems play an important role in global primary production. Microalgae have adaptations that enable them to live under low temperature environments where irradiance and day length change drastically. Their adaptations, leading to different ecophysiological characteristics relative to temperate species, could also alter their sensitivity to pollutants such as pesticides. This study's objective was to understand how different ecophysiological characteristics influence the response of Arctic phytoplankton to pesticides in relation to the responses of their temperate counterparts. Ecophysiological endpoints were related to growth, cell biovolume, pigment content, photosynthetic activity, photoprotective mechanisms (NPQ, antioxidant enzyme activities), and reactive oxygen species (ROS) content. The Arctic species Micromonas polaris was more resistant to atrazine and simazine than its temperate counterpart Micromonas bravo. However, the other Arctic species Chaetoceros neogracilis was more sensitive to these herbicides than its temperate counterpart Chaetoceros neogracile. With respect to two other pesticide toxicity, both temperate microalgae were more sensitive to trifluralin, while Arctic microalgae were more sensitive to chlorpyrifos (insecticide). All differences could be ascribed to differences in the eco-physiological features of the two microalgal groups, which can be explained by cell size, pigment content, ROS content and protective mechanisms (NPQ and antioxidant enzymes).

Do anti-HIV drugs pose a threat to photosynthetic microorganisms?

We investigated the occurrence and risk assessment of three anti-HIV drugs [(tenofovir (TNF), lamivudine (LMV) and efavirenz (EFV)] in urban rivers from Curitiba (Brazil), as well as the individual and combined effects of their environmental representative concentrations on the freshwater periphytic species Synechococcus elongatus (Cyanobacteria) and Chlorococcum infusionum (Chlorophyta). The three studied drugs, except TNF, were found in 100% of the samples, and concentrations in samples ranged from 165 to 412 ng TNF L-1, 173-874 ng LMV L-1 and 13-1250 ng EFV L-1. Bioassays using artificial contaminated water showed that at environmental concentrations, TNF and LMV did not represent environmental risks to the studied photosynthetic organisms. However, EFV was shown to be toxic, affecting photosynthesis, respiration, and oxidative metabolism. The studied drugs demonstrated interactive effects. Indeed, when submitted to the combination of TNF and LMV, decreased photosynthesis was observed in C. infusionum cells. Moreover, the toxic effects of EFV were amplified in both species when TNF and/or LMV were added to the media. The simultaneous presence of TNF, LMV and EFV in environmental matrices associated with their interactive effects, lead to increased toxicological effects of water contaminated by anti-HIV drugs and thus to an ecological threat to photosynthetic microorganisms.

Periphytic Algae and Cyanobacteria from the Rio Doce Basin Respond Differently to Metals and Salinity, Showing Different Potential for Bioremediation.

We have studied the isolated and combined effects of metals (Fe and Mn) and NaCl the on growth, physiology, and metal-uptake capacity of two photosynthetic periphytic species-Synechococcus elongatus (Cyanobacteria) and Chlorococcum infusionum (Chlorophyta)-isolated from an impacted area of the Rio Doce River (Brazil) after the Fundão dam collapse. The effective concentrations found to reduce 10 and 50% growth were 15.2 and 31.6 mg Fe L-1, and 2.5 and 7.9 mg Mn L-1 for S. elongatus and 53.9 and 61.6 mg Fe L-1, and 53.2 and 60.9 mg Mn L-1 for C. infusionum. Although the metal toxicity was related to oxidative stress, both species showed activation of antioxidant systems under phytotoxic concentrations of Fe and Mn. By binding large concentrations of metals on its cell surface and thus avoiding their entrance into the cells, C. infusionum presents greater resistance to Fe and Mn than S. elongatus. Under environmental realistic concentrations of Fe and Mn in river water from the Rio Doce Basin, S. elongatus and C. infusionum showed a metal removal efficiency of 42 and 65% and 53 and 79%, respectively after 96 h. These species were insensitive to increased NaCl concentrations which, in addition, did not disrupt the metal removal capacity of the species. Due to their salt and metal tolerance, S. elongatus and C. infusionum can be used for the remediation of waters contaminated with Fe and Mn.

Light modulates the effect of antibiotic norfloxacin on photosynthetic processes of Microcystis aeruginosa.

Norfloxacin is one of the widely used antibiotics, often detected in aquatic ecosystems, and difficultly degraded in the environment. However, how norfloxacin affects the photosynthetic process of freshwater phytoplankton is still largely unknown, especially under varied light conditions. In this study, we investigated photosynthetic mechanisms of Microcystis aeruginosa in responses to antibiotic norfloxacin (0-50 µg/L) for 72 h under low (LL; 50 µmol photons m-2 s-1) and high (HL; 250 µmol photons m-2 s-1) growth light regimes. We found that environmentally related concentrations of norfloxacin inhibited the growth rate and operational quantum yield of photosynthesis system II (PSII) of M. aeruginosa more under HL than under LL, suggesting HL increased the toxicity of norfloxacin to M. aeruginosa. Further analyses showed that norfloxacin deactivated PSII reaction centers under both growth light regimes with increased minimal fluorescence yields only under HL, suggesting that norfloxacin not only damaged reaction centers of PSII, but also inhibited energy transfer among phycobilisomes in M. aeruginosa under HL. However, non-photosynthetic quenching decreased in the studied species by norfloxacin exposure under both growth light regimes, suggesting that excess energy might not be efficiently dissipated as heat. Also, we found that reactive oxygen species (ROS) content increased under norfloxacin treatments with a higher ROS content under HL compared to LL. In addition, HL increased the absorption of norfloxacin by M. aeruginosa, which could partly explain the high sensitivity to norfloxacin of M. aeruginosa under HL. This study firstly reports that light can strongly affect the toxicity of norfloxacin to M. aeruginosa, and has vitally important implications for assessing the toxicity of norfloxacin to aquatic microorganisms.

Occurrence of microcystins, anabaenopeptins and other cyanotoxins in fish from a freshwater wildlife reserve impacted by harmful cyanobacterial blooms.

Harmful algal blooms of cyanobacteria (CyanoHABs) can lead to the release of potent toxins that can seriously affect ecosystem integrity. Some freshwater watersheds are particularly at risk considering the threats to already imperiled wildlife. The consumption of tainted drinking water and contaminated food also raises concerns for human health. In the present study, a pilot survey was conducted in the riverine ecosystem of the Pike River Ecological Reserve (QC, Canada) near Missisquoi Bay, Lake Champlain. We examined the occurrence of multiclass cyanotoxins including 12 microcystins, anatoxins, cylindrospermopsin (CYN), anabaenopeptins (AP-A, AP-B), and cyanopeptolin-A in surface waters and wild-caught fish during the summer 2018. Out of the 18 targeted cyanotoxins, 14 were detected in bloom-impacted surface water samples; toxins peaked during early-mid September with the highest concentrations for MC-LR (3.8 µg L-1) and MC-RR (2.9 µg L-1). Among the 71 field-collected fish from 10 species, 30% had positive detections to at least one cyanotoxin. In positive samples, concentration ranges in fish muscle were as follows for summed microcystins (∑MCs: 0.16-9.2 µg kg-1), CYN (46-75 µg kg-1), AP-A (1.1-5.4 µg kg-1), and AP-B (0.12-5.0 µg kg-1). To the best of our knowledge, this is one the first reports of anabaenopeptins occurrence in wildlife. The maximum ∑MCs in fish was 1.15-fold higher than the World Health Organization (WHO) daily intake recommendation for adults and nearly equated the derived value for young children. The concentration of CYN was also about 3-fold higher than the limit derived from the human health guideline values.

Host development overwhelms environmental dispersal in governing the ecological succession of zebrafish gut microbiota.

Clarifying mechanisms underlying the ecological succession of gut microbiota is a central theme of gut ecology. Under experimental manipulations of zebrafish hatching and rearing environments, we test our core hypothesis that the host development will overwhelm environmental dispersal in governing fish gut microbial community succession due to host genetics, immunology, and gut nutrient niches. We find that zebrafish developmental stage substantially explains the gut microbial community succession, whereas the environmental effects do not significantly affect the gut microbiota succession from larvae to adult fish. The gut microbiotas of zebrafish are clearly separated according to fish developmental stages, and the degree of homogeneous selection governing gut microbiota succession is increasing with host development. This study advances our mechanistic understanding of the gut microbiota assembly and succession by integrating the host and environmental effects, which also provides new insights into the gut ecology of other aquatic animals.

Toxic and protective mechanisms of cyanobacterium Synechocystis sp. in response to titanium dioxide nanoparticles.

An increasing production and use of titanium dioxide nanoparticles (TiO2 NPs) pose a huge threat to phytoplankton since they are largely released into aquatic environments, which represent a sink for TiO2 NPs. However, toxicity and protective mechanisms of cyanobacteria in response to TiO2 NPs remain elusive. Here we investigated toxic effects of two sizes of TiO2 NPs (50 and 10 nm) and one bulk TiO2 (200 nm) on a cyanobacterium, Synechocystis sp. and their possible protective mechanisms. We found that 10 nm TiO2 NPs caused significant growth and photosynthesis inhibition in Synechocystis sp. cells, largely reflected in decreased growth rate (38%), operational PSII quantum yields (40%), phycocyanin (51%) and allophycocyanin (63%), and increased reactive oxygen species content (245%), superoxide dismutase activity (46%). Also, transcriptomic analysis of Synechocystis sp. exposure to 10 nm TiO2 NPs showed the up-regulation of D1 and D2 protein genes (psbA and psbD), ferredoxin gene (petF) and F-type ATPase genes (e.g., atpB), and the down-regulation of psbM and psb28-2 in PS II. We further proposed a conceptual model to explore possible toxic and protective mechanisms for Synechocystis sp. under TiO2 nanoparticle exposure. This study provides mechanistic insights into our understanding of Synechocystis sp. responses to TiO2 NPs. This is essential for more accurate environmental risk assessment approaches of nanoparticles in aquatic ecosystems by governmental environmental agencies worldwide.

Mechanistic insights into organic carbon-driven water blackening and odorization of urban rivers.

With rapid global urbanization, massive anthropogenic inputs of organic matter and inorganic nutrients are resulting in severe pollution of urban rivers and consequently altering the structure and function of their aquatic microbial communities. In contrast to nutrient-induced eutrophication of freshwaters, water blackening and odorization of urban rivers, as well as their microbial communities, are poorly understood at a mechanistic level. Here, in a one-year field study on the taxonomic composition, predicted function and spatiotemporal dynamics of water and sediment microbial communities in seven black-odorous urban rivers in a megacity in southern China, combined with laboratory water-sediment column experiments, we pinpointed organic carbon as a key parameter driving the overgrowth of aquatic heterogeneous microorganisms. These microorganisms are major constituents of suspended black flocs that mediate methanogenic digestion of organic carbon and consequent water blackening and odorization. Source tracking analysis revealed a strikingly high contribution of sewage communities to black-odorous water microbial communities, in which emerging pathogens are enriched. Our results provide mechanistic insight into organic carbon-driven water blackening and odorization of urban rivers, which brings up current remediation strategies in questioning and sheds light on the future sustainable management of urban aquatic ecosystems.

Effects of Titanium Dioxide Nanoparticles on Photosynthetic and Antioxidative Processes of Scenedesmus obliquus.

The effects of the photocatalytic toxicity of titanium dioxide nanoparticle (nano-TiO2) on phytoplankton are well understood. However, as UV light intensity decreases sharply with the depth of the water column, the effects of nano-TiO2 itself on deeper water phytoplankton, such as green algae, need further research. In this research, we investigated the effects of three sizes of TiO2 (10, 50 and 200 nm) on the photosynthetic and antioxidative processes of Scenedesmus obliquus in the absence of UV light. We found that 50 nm and 10 nm TiO2 (10 mg/L) inhibited growth rates and the maximal photosystem II quantum yield compared to the control in Scenedesmus obliquus. The minimal and maximal fluorescence yields, and the contents of reactive oxygen species and lipid peroxidation, increased, indicating that photosynthetic energy/electrons transferred to oxygen and induced oxidative stress in nano-TiO2-treated samples. In addition, we found that aggregations of algae and 10 nm TiO2 were present, which could induce cell membrane disruption, and vacuoles were induced to cope with nano-TiO2 stress in Scenedesmus obliquus. These results enhance our understanding of the effects of nano-TiO2 on the photosynthetic and antioxidative processes of green algae, and provide basic information for evaluating the ecotoxicity of nano-TiO2 in freshwater ecosystems.

Experimental evolution reveals nitrate tolerance mechanisms in Desulfovibrio vulgaris.

Elevated nitrate in the environment inhibits sulfate reduction by important microorganisms of sulfate-reducing bacteria (SRB). Several SRB may respire nitrate to survive under elevated nitrate, but how SRB that lack nitrate reductase survive to elevated nitrate remains elusive. To understand nitrate adaptation mechanisms, we evolved 12 populations of a model SRB (i.e., Desulfovibrio vulgaris Hildenborough, DvH) under elevated NaNO3 for 1000 generations, analyzed growth and acquired mutations, and linked their genotypes with phenotypes. Nitrate-evolved (EN) populations significantly (p < 0.05) increased nitrate tolerance, and whole-genome resequencing identified 119 new mutations in 44 genes of 12 EN populations, among which six functional gene groups were discovered with high mutation frequencies at the population level. We observed a high frequency of nonsense or frameshift mutations in nitrosative stress response genes (NSR: DVU2543, DVU2547, and DVU2548), nitrogen regulatory protein C family genes (NRC: DVU2394-2396, DVU2402, and DVU2405), and nitrate cluster (DVU0246-0249 and DVU0251). Mutagenesis analysis confirmed that loss-of-functions of NRC and NSR increased nitrate tolerance. Also, functional gene groups involved in fatty acid synthesis, iron regulation, and two-component system (LytR/LytS) known to be responsive to multiple stresses, had a high frequency of missense mutations. Mutations in those gene groups could increase nitrate tolerance through regulating energy metabolism, barring entry of nitrate into cells, altering cell membrane characteristics, or conferring growth advantages at the stationary phase. This study advances our understanding of nitrate tolerance mechanisms and has important implications for linking genotypes with phenotypes in DvH.

Individual and combined effects of amoxicillin, enrofloxacin, and oxytetracycline on Lemna minor physiology.

We investigated individual and combined effects of environmentally representative concentrations of amoxicillin (AMX; 2 µg l-1), enrofloxacin (ENR; 2 µg l-1), and oxytetracycline (OXY; 1 µg l-1) on the aquatic macrophyte Lemna minor. While the concentrations of AMX and ENR tested were not toxic, OXY decreased plant growth and cell division. OXY induced hydrogen peroxide (H2O2) accumulation and related oxidative stress through its interference with the activities of mitochondria electron transport chain enzymes, although those deleterious effects could be ameliorated by the presence of AMX and/or ENR, which prevented the overaccumulation of ROS by increasing catalase enzyme activity. L. minor plants accumulated significant quantities of AMX, ENR and OXY from the media, although competitive uptakes were observed when plants were submitted to binary or tertiary mixtures of those antibiotics. Our results therefore indicate L. minor as a candidate for phytoremediation of service waters contaminated by AMX, ENR, and/or OXY.