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Parkinson's disease (PD) is characterized by multiple symptoms including olfactory dysfunction, whose underlying mechanisms remain unclear. Here, we explored pathologic changes in the olfactory pathway of transgenic (Tg) mice of both sexes expressing the human A30P mutant α-synuclein (α-syn; α-syn-Tg mice) at 6–7 and 12–14 months of age, representing early and late-stages of motor progression, respectively. α-Syn-Tg mice at late stages exhibited olfactory behavioral deficits, which correlated with severe α-syn pathology in projection neurons (PNs) of the olfactory pathway. In parallel, olfactory bulb (OB) neurogenesis in α-syn-Tg mice was reduced in the OB granule cells at six to seven months and OB periglomerular cells at 12–14 months, respectively, both of which could contribute to olfactory dysfunction. Proteomic analyses showed a disruption in endocytic and exocytic pathways in the OB during the early stages which appeared exacerbated at the synaptic terminals when the mice developed olfactory deficits at 12–14 months. Our data suggest that (1) the α-syn-Tg mice recapitulate the olfactory functional deficits seen in PD; (2) olfactory structures exhibit spatiotemporal disparities for vulnerability to α-syn pathology; (3) α-syn pathology is restricted to projection neurons in the olfactory pathway; (4) neurogenesis in adult α-syn-Tg mice is reduced in the OB; and (5) synaptic endocytosis and exocytosis defects in the OB may further explain olfactory deficits.SIGNIFICANCE STATEMENTOlfactory dysfunction is a characteristic symptom of Parkinson's disease (PD). Using the human A30P mutant α-synuclein (α-syn)-expressing mouse model, we demonstrated the appearance of olfactory deficits at late stages of the disease, which was accompanied by the accumulation of α-syn pathology in projection neurons (PNs) of the olfactory system. This dysfunction included a reduction in olfactory bulb (OB) neurogenesis as well as changes in synaptic vesicular transport affecting synaptic function, both of which are likely contributing to olfactory behavioral deficits.

Voltage-gated calcium (Cav) channels are a prerequisite for signal transmission at the first olfactory sensory neuron (OSN) synapse within the glomeruli of the main olfactory bulb (MOB). We showed previously that the N-type Cav channel subunit Cav2.2 is present in the vast majority of glomeruli and plays a central role in presynaptic transmitter release. Here, we identify a distinct subset of glomeruli in the MOB of adult mice that is characterized by expression of the P/Q-type channel subunit Cav2.1. Immunolocalization shows that Cav2.1+ glomeruli reside predominantly in the medial and dorsal MOB, and in the vicinity of the necklace glomerular region close to the accessory olfactory bulb. Few glomeruli are detected on the ventral and lateral MOB. Cav2.1 labeling in glomeruli colocalizes with the presynaptic marker vGlut2 in the axon terminals of OSNs. Electron microscopy shows that Cav2.1+ presynaptic boutons establish characteristic asymmetrical synapses with the dendrites of second-order neurons in the glomerular neuropil. Cav2.1+ glomeruli receive axonal input from OSNs that express molecules of canonical OSNs: olfactory marker protein, the ion channel Cnga2, and the phosphodiesterase Pde4a. In the main olfactory epithelium, Cav2.1 labels a distinct subpopulation of OSNs whose distribution mirrors the topography of the MOB glomeruli, that shows the same molecular signature, and is already present at birth. Together, these experiments identify a unique Cav2.1+ multiglomerular domain in the MOB that may form a previously unrecognized olfactory subsystem distinct from other groups of necklace glomeruli that rely on cGMP signaling mechanisms.

The biodegradation of dispersed crude oil in the ocean is relatively rapid (a half-life of a few weeks). However, it is often much slower on shorelines, usually attributed to low moisture content, nutrient limitation, and higher oil concentrations in beaches than in dispersed plumes. Another factor may be the increased salinity of the upper intertidal and supratidal zones because these parts of the beach are potentially subject to prolonged evaporation and only intermittent inundation. We have investigated whether such an increase in salinity has inhibitory effects on oil biodegradation in seashores. Lightly weathered Hibernia crude oil was added to beach sand at 1 or 10 mL/kg, and fresh seawater, at salinities of 30, 90, and 160 g/L, was added to 20% saturation. The biodegradation of oil was slower at higher salinities, where the half-life increased from 40 days at 30 g/L salts to 58 and 76 days at 90 and 160 g/L salts, respectively, and adding fertilizers somewhat enhanced oil biodegradation. Increased oil concentration in the sand, from 1 to 10 mL/kg, slowed the half-life by about 10-fold. Consequently, occasional irrigation with fertilization could be a suitable bioremediation strategy for the upper parts of contaminated beaches. However, dispersing oil at sea is probably the most suitable option for the optimal removal of spilled crude oil from the marine environment.

At high latitudes, lake whitefish (Coregonus clupeaformis) and others in the closely relatedCoregonusspecies complex (CSC), including cisco (C. autumnalisandC. sardinella), can be diadromous, seasonally transitioning between freshwater lakes and the Arctic Ocean. CSC skin- and intestine microbiomes were collected, facilitated by Inuit fishers at sites on and around King William Island, Nunavut, at the northern range limits of lake whitefish. Community composition was explored using 16S rRNA gene sequencing, with significant differences in microbiota dispersions depending on fishing site salinity for lake whitefish intestine and skin, as well as cisco skin. Overall, lake whitefish intestine communities appeared more variable than cisco and had higher Shannon diversity, suggesting that lake whitefish and their microbiomes could be more susceptible to environmental stress possibly leading to dysbiosis. Although cisco condition was similar among distinct seasonal habitats, the higher average lake whitefish condition in freshwater rivers suggests that fishing these diadromous whitefish in estuaries may be optimal from a sustainable fishery perspective. Taken together, the impact of changing habitats on fish condition and different microbial composition may inform new approaches to CSC health in fisheries and aquaculture, in addition to being relevant for northern Indigenous peoples with subsistence and economic interests in these resources.

Lake Erie is subject to recurring events of cyanobacterial harmful algal blooms (cHABs), but measures of nutrients and total phytoplankton biomass seem to be poor predictors of cHABs when taken individually. A more integrated approach at the watershed scale may improve our understanding of the conditions that lead to bloom formation, such as assessing the physico-chemical and biological factors that influence the lake microbial community, as well as identifying the linkages between Lake Erie and the surrounding watershed. Within the scope of the Government of Canada’s Genomics Research and Development Initiative (GRDI) Ecobiomics project, we used high-throughput sequencing of the 16S rRNA gene to characterize the spatio-temporal variability of the aquatic microbiome in the Thames River–Lake St. Clair-Detroit River–Lake Erie aquatic corridor. We found that the aquatic microbiome was structured along the flow path and influenced mainly by higher nutrient concentrations in the Thames River, and higher temperature and pH downstream in Lake St. Clair and Lake Erie. The same dominant bacterial phyla were detected along the water continuum, changing only in relative abundance. At finer taxonomical level, however, there was a clear shift in the cyanobacterial community, with Planktothrix dominating in the Thames River and Microcystis and Synechococcus in Lake St. Clair and Lake Erie. Mantel correlations highlighted the importance of geographic distance in shaping the microbial community structure. The fact that a high proportion of microbial sequences found in the Western Basin of Lake Erie were also identified in the Thames River, indicated a high degree of connectivity and dispersal within the system, where mass effect induced by passive transport play an important role in microbial community assembly. Nevertheless, some cyanobacterial amplicon sequence variants (ASVs) related to Microcystis, representing less than 0.1% of relative abundance in the upstream Thames River, became dominant in Lake St. Clair and Erie, suggesting selection of those ASVs based on the lake conditions. Their extremely low relative abundances in the Thames suggest additional sources are likely to contribute to the rapid development of summer and fall blooms in the Western Basin of Lake Erie. Collectively, these results, which can be applied to other watersheds, improve our understanding of the factors influencing aquatic microbial community assembly and provide new perspectives on how to better understand the occurrence of cHABs in Lake Erie and elsewhere.

Greenhouse gas (GHG) emissions from Arctic permafrost soils create a positive feedback loop of climate warming and further GHG emissions. Active methane uptake in these soils can reduce the impact of GHG on future Arctic warming potential. Aerobic methane oxidizers are thought to be responsible for this apparent methane sink, though Arctic representatives of these organisms have resisted culturing efforts. Here, we first used in situ gas flux measurements and qPCR to identify relative methane sink hotspots at a high Arctic cytosol site, we then labeled the active microbiome in situ using DNA Stable Isotope Probing (SIP) with heavy 13CH4 (at 100 ppm and 1000 ppm). This was followed by amplicon and metagenome sequencing to identify active organisms involved in CH4 metabolism in these high Arctic cryosols. Sequencing of 13C-labeled pmoA genes demonstrated that type II methanotrophs (Methylocapsa) were overall the dominant active methane oxidizers in these mineral cryosols, while type I methanotrophs (Methylomarinovum) were only detected in the 100 ppm SIP treatment. From the SIP-13C-labeled DNA, we retrieved nine high to intermediate quality metagenome-assembled genomes (MAGs) belonging to the Proteobacteria, Gemmatimonadetes, and Chloroflexi, with three of these MAGs containing genes associated with methanotrophy. A novel Chloroflexi MAG contained a mmoX gene along with other methane oxidation pathway genes, identifying it as a potential uncultured methane oxidizer. This MAG also contained genes for copper import, synthesis of biopolymers, mercury detoxification, and ammonia uptake, indicating that this bacterium is strongly adapted to conditions in active layer permafrost and providing new insights into methane biogeochemical cycling. In addition, Betaproteobacterial MAGs were also identified as potential cross-feeders with methanotrophs in these Arctic cryosols. Overall, in situ SIP labeling combined with metagenomics and genome binning demonstrated to be a useful tool for discovering and characterizing novel organisms related to specific microbial functions or biogeochemical cycles of interest. Our findings reveal a unique and active Arctic cryosol microbial community potentially involved in CH4 cycling.

Oil spill attenuation in Arctic marine environments depends on oil-degrading bacteria. However, the seasonally harsh conditions in the Arctic such as nutrient limitations and sub-zero temperatures limit the activity even for bacteria capable of hydrocarbon metabolism at low temperatures. Here, we investigated whether the variance between epipelagic (seasonal temperature and inorganic nutrient variations) and mesopelagic zone (stable environmental conditions) could limit the growth of oil-degrading bacteria and lead to lower oil biodegradation rates in the epipelagic than in the mesopelagic zone. Therefore, we deployed absorbents coated with three oil types in a SW-Greenland fjord system at 10–20 m (epipelagic) and 615–650 m (mesopelagic) water depth for one year. During this period we monitored the development and succession of the bacterial biofilms colonizing the oil films by 16S rRNA gene amplicon quantification and sequencing, and the progression of oil biodegradation by gas chromatography – mass spectrometry oil fingerprinting analysis. The removal of hydrocarbons was significantly different, with several polycyclic aromatic hydrocarbons showing longer half-life times in the epipelagic than in the mesopelagic zone. Bacterial community composition and density (16S rRNA genes/ cm2) significantly differed between the two zones, with total bacteria reaching to log-fold higher densities (16S rRNA genes/cm2) in the mesopelagic than epipelagic oil-coated absorbents. Consequently, the environmental conditions in the epipelagic zone limited oil biodegradation performance by limiting bacterial growth.

Crop breeding has traditionally ignored the plant-associated microbial communities. Consideration of the interactions between plant genotype and associated microbiota is of value since different genotypes of the same crop often harbor distinct microbial communities which can influence the plant phenotype. However, recent studies have reported contrasting results, which led us to hypothesize that the effect of genotype is constrained by time (growth stage, year) and space (plant compartment). To test this hypothesis, we sampled bulk soil, rhizosphere soil and roots of 10 wheat genotypes, twice per year, for 4 years. DNA was extracted and regions of the bacterial 16S rRNA and CPN60 genes and the fungal ITS region were amplified and sequenced. The effect of genotype was highly contingent on the time of sampling and on the plant compartment sampled. Only for a few sampling dates, were the microbial communities significantly different across genotypes. The effect of genotype was most often significant for root microbial communities. The three marker genes used provided a highly coherent picture of the effect of genotype. Taken together, our results confirm that microbial communities in the plant environment strongly vary temporally and spatially and that this can mask the effect of genotype.

Parkinson’s Disease (PD) is characterized by multiple symptoms including olfactory dysfunction, whose underlying mechanisms remain unclear. Here, we explored pathological changes in the olfactory pathway of transgenic (Tg) mice expressing the human A30P mutant α-synuclein (α-syn) (α-syn-Tg mice) at 6-7 and 12-14 months of age, representing early and late-stages of motor progression, respectively. α-Syn-Tg mice at late stages exhibited olfactory behavioral deficits, which correlated with severe α-syn pathology in projection neurons of the olfactory pathway. In parallel, olfactory bulb (OB) neurogenesis in α-syn-Tg mice was reduced in the OB granule cells at 6-7 months, and OB periglomerular cells at 12-14 months, respectively, both of which could contribute to olfactory dysfunction. Proteomic analyses showed a disruption in endo- and exocytic pathways in the OB during the early stages which appeared exacerbated at the synaptic terminals when the mice developed olfactory deficits at 12-14 months. Our data suggest that, 1) the α-syn-Tg mice recapitulate the olfactory functional deficits seen in PD; 2) olfactory structures exhibit spatiotemporal disparities for vulnerability to α-syn pathology; 3) α-syn pathology is restricted to projection neurons in the olfactory pathway; 4) neurogenesis in adult α-syn-Tg mice is reduced in the OB; and 5) synaptic endo- and exocytosis defects in the OB may further explain olfactory deficits.

Draft whole-genome sequences of a coculture are presented. One component was a polar cyanobacterium, Leptolyngbya sp. strain Cla-17. The second was a heterotrophic bacterium, Flavobacterium saccharophilum , found in the phycosphere of the cyanobacterium.

The biodegradability of residues produced during in-situ burning, an oil spill response strategy involving the burning of oil on the sea surface, has not yet been fully studied. A growing risk of oil spills necessitates a better understanding of the fate of these burn residues containing potentially toxic substances. Microcosm experiments were performed to study the microbial community response and potential biodegradability of burn residues generated from Ultra Low Sulfur (ULS) marine diesel. Burn residues were incubated in natural seawater and sacrificed for 16SrRNA gene amplicon and shotgun metagenomic sequencing. Unweathered andweathered diesel were used for the microcosm experiments, and the addition of a fertilizer and dispersant were also included in the experimental design. After incubation, chemistry analyses revealed that some hydrocarbons, notably medium chain-length n-alkanes, had significantly decreased in most treatments. Burn residuemicrocosms also had distinct microbial communities with an enrichment in putative hydrocarbon degraders and hydrocarbon-degrading genes. These results suggest that some residual compounds in ULS marine diesel burn residue were potentially biodegraded.Future studies involving longer microcosm incubation periods could yield insight into the fate of the more recalcitrant aromatic compounds.

Microglia invade the neuroblast migratory corridor of the rostral migratory stream (RMS) early in development. This work examines how microglia maintain the homeostatic conditions permissive to neuroblast migration in the RMS during the early postnatal period. GFP labeled microglia in CX3CR-1GFP/+ mice assemble primarily along the outer borders of the RMS during the first postnatal week, where they exhibit predominantly an ameboid morphology and associate with migrating neuroblasts. Microglia ablation for 3 days postnatally does not impact the density of pulse labeled BrdU+ neuroblasts nor the distance migrated by tdTomato electroporated neuroblasts in the RMS. However, microglia wrap DsRed-labeled neuroblasts in the RMS of P7 CX3CR-1GFP/+;DCXDsRed/+ mice and express the phagocytic markers CD68, CLEC7A and MERTK, suggesting active phagocytosis of neuroblasts in the developing RMS. Microglia depletion for 14 days postnatally further induced an accumulation of DCX+ neuroblasts and CC3+ apoptotic cells in the RMS, a wider RMS and extended patency of the lateral ventricle extension in the olfactory bulb. These findings illustrate the importance of microglia phagocytosis in maintaining the homeostasis of the early postnatal RMS.SIGNIFICANCE STATEMENTMicroglia are brain-resident immune cells responsible for both maintaining homeostatic conditions necessary for normal neurodevelopment as well as orchestrating the brain’s response to environmental insults. The effects of microglia-mediated immune response during development may be of special relevance to the olfactory system, which is unique in both its vulnerability to environmental insults as well as its extended period of neurogenesis and neuronal migration. The work presented here examines how microglia maintain homeostatic conditions in the neuroblast migratory corridor of the rostral migratory stream (RMS) in the olfactory system during early postnatal development. Our findings illustrate the importance of microglia phagocytosis in the early postnatal RMS and provides insights into microglia function during periods of neurogenesis and neuronal migration.

Summary Intestinal microbial communities from 362 anadromous Arctic char (Salvelinus alpinus) from the high Arctic Kitikmeot region, Nunavut, Canada, were characterized using high‐throughput 16S rRNA gene sequencing. The resulting bacterial communities were compared across four seasonal habitats that correspond to different stages of annual migration. Arctic char intestinal communities differed by sampling site, salinity and stages of freshwater residence. Although microbiota from fish sampled in brackish water were broadly consistent with taxa seen in other anadromous salmonids, they were enriched with putative psychrophiles, including the nonluminous gut symbiont Photobacterium iliopiscarium that was detected in >90% of intestinal samples from these waters. Microbiota from freshwater‐associated fish were less consistent with results reported for other salmonids, and highly variable, possibly reflecting winter fasting behaviour of these char. We identified microbiota links to age for those fish sampled during the autumn upriver migration, but little impact of the intestinal content and water microbiota on the intestinal community. The strongest driver of intestinal community composition was seasonal habitat, and this finding combined with identification of psychrophiles suggested that water temperature and migratory behaviour are key to understanding the relationship between Arctic char and their symbionts.

Oil spills in coastal waters can have devastating impacts on local ecosystems, from the microscopic base through to mammals and seabirds. Increasing transport of diluted bitumen has led to concerns about how this novel product might impact coastal ecosystems. A mesocosm study determined that the type of diluent and the season can affect the concentrations of hydrocarbons entering the water column from a surface spill. Those same mesocosms were sampled to determine whether diluent type and season also affected the microbial response to a surface spill. Overall, there were no differences in impacts among the three types of diluted bitumen, but there were consistent responses to all products within each season. Although microbial abundances with diluted bitumen rarely differed from unoiled controls, community structure in these organisms shifted in response to hydrocarbons, with hydrocarbon-degrading bacteria becoming more abundant. The relative abundance of heterotrophic eukaryotes also increased with diluted bitumen, with few photosynthetic organisms responding positively to oil. Overall shifts in the microbial communities were minimal relative to spills of conventional oil products, with low concentrations of hydrocarbons in the water column. Oil spill response should focus on addressing the surface slick to prevent sinking or stranding to minimize ecosystem impacts.

Growing concerns over the risk of accidental releases of oil into the marine environment have emphasized our need to improve both oil spill preparedness and response strategies. Among the available spill response options, dispersants offer the advantages of breaking oil slicks into small oil droplets and promoting their dilution, dissolution, and biodegradation within the water column. Thus dispersants can reduce the probability of oil slicks at sea from reaching coastal regions and reduce their direct impact on mammals, sea birds and shoreline ecosystems. To facilitate marine oil spill response operations, especially addressing spill incidents in remote/Arctic offshore regions, an in-depth understanding of the transportation, fate and effects of naturally/chemically dispersed oil is of great importance. This review provides a synthesis of recent research results studies related to the application of dispersants at the surface and in the deep sea, the fate and transportation of naturally and chemically dispersed oil, and dispersant application in the Arctic and ice-covered waters. Future perspectives have been provided to identify the research gaps and help industries and spill response organizations develop science-based guidelines and protocols for the application of dispersants application.

Despite many studies of diluted bitumen (DB) behavior during spills in saltwater, limited information is available on DB behavior in fresh water. This study examined the collective weathering processes on changes of fresh DB spilled in the North Saskatchewan River water and sediment mixture in a mesoscale spill tank under average air/water temperatures of 14 °C/15 °C and 6 °C/2 °C. Temporal changes of the hydrocarbon and microbial community compositions in the water column were assessed during the two 35-day tests under intermittent wave action. The contents of total organic carbon (TOC), benzene/toluene/ethylbenzene/xylenes (BTEX) and polycyclic aromatic hydrocarbons (PAHs) in water decreased with time during both tests. The final contents remained at higher values in warm water (15 °C) than in cold water (2 °C) after the collective weathering processes. A quick response of the main phyla, Proteobacteria and Actinobacteria, was observed, where the members of Proteobacteria enriched during both DB spills. In contrast, the members of Actinobacteria reduced with time. The microbial shifts coincided with the changes of PAHs in the waters at both temperatures. A comparison of the physical properties and chemical compositions of fresh and weathered DBs at both temperatures showed that the oil had undergone weathering that increased oil density and viscosity due to losing the light oil fraction with boiling points204 °C and emulsifying with water. This corresponded to losses of 19.0 wt% and 17.2 wt% of the fresh DB at 15 °C and 2 °C tests, respectively. For organic compounds in the DB with boiling points204 °C, there were small losses of saturates and 2-3-ring PAH aromatics (more during the 15 °C test than the 2 °C test), and negligible losses in the subfractions of resins and asphaltenes by the ends of the tests.1.0 wt% of the DB was recovered from the bottom sediment, regardless of the temperature.

Microglia invade the neuroblast migratory corridor of the rostral migratory stream (RMS) early in development. The early postnatal RMS does not yet have the dense astrocyte and vascular scaffold that helps propel forward migrating neuroblasts, which led us to consider whether microglia help regulate conditions permissive to neuroblast migration in the RMS. GFP-labeled microglia inCX3CR-1GFP/+mice assemble primarily along the outer borders of the RMS during the first postnatal week, where they exhibit predominantly an ameboid morphology and associate with migrating neuroblasts. Microglia ablation for 3 d postnatally does not impact the density of pulse labeled BrdU+ neuroblasts nor the distance migrated by tdTomato electroporated neuroblasts in the RMS. However, microglia wrap DsRed-labeled neuroblasts in the RMS of P7CX3CR-1GFP/+;DCXDsRed/+mice and express the markers CD68, CLEC7A, MERTK, and IGF-1, suggesting active regulation in the developing RMS. Microglia depletion for 14 d postnatally further induced an accumulation of CC3+ DCX+ apoptotic neuroblasts in the RMS, a wider RMS and extended patency of the lateral ventricle extension in the olfactory bulb. These findings illustrate the importance of microglia in maintaining a healthy neuroblast population and an environment permissive to neuroblast migration in the early postnatal RMS.

In 1999, a tidal wetland located along the St. Lawrence River close to Ste. Croix de Lotbinière (Quebec, Eastern Canada) was the site of an experimental oil spill. Test plots were established and subjected to an experimental crude oil spill to evaluate natural attenuation, nutrient amendment and vegetation cropping as countermeasures. In 2020, this study re-visited the test plots to investigate residual oil and habitat recovery. Only concentrations of mid-chain length n-alkanes (C10-C36), but not of polycyclic aromatic hydrocarbons (PAHs), were significantly above detection limit, and were detected in both test plot and control sediments. Hydrocarbon, total organic carbon, nitrogen and phosphate contents did not differ significantly between test plot and control sediments. Microbial analyses did not detect significant differences in microbial load, microbial diversity or microbial community composition between test plot and control sediments. Key genes for the aerobic and anaerobic degradation of n-alkanes as well as for the aerobic degradation of PAHs were detected in all sediment samples. Associated gene abundances did not differ significantly between test plot and control sediments. This study shows that oil-exposed test plot sediments of the Ste. Croix wetland can be considered completely recovered after 21 years irrespective of the performed countermeasure.

Understanding microbial responses to hydrocarbon and plastic pollution are crucial for limiting the detrimental impacts of environmental contaminants on marine ecosystems. Herein, we reported a new Alcanivorax species isolated from the North Atlantic Ocean capable of degrading alkanes and polyhydroxybutyrate (PHB) plastic (one of the emerging bioplastics that may capture the future plastic market). The whole-genome sequencing showed that the species harbors three types of alkane 1-monooxygenases (AlkB) and one PHB depolymerase (PhaZ) to initiate the degradation of alkanes and plastics. Growth profiling demonstrated that n-pentadecane (C15, the main alkane in the marine environment due to cyanobacterial production other than oil spills) and PHB could serve as preferential carbon sources. However, the cell membrane composition, PhaZ activity, and expression of three alkB genes were utterly different when grown on C15 and PHB. Further, Alcanivorax was a well-recognized alkane-degrader that participated in the ocean hydrocarbon cycles linking with hydrocarbon production and removal. Our discovery supported that the existing biogeochemical processes may add to the marine ecosystem's resilience to the impacts of plastics.

Surficial application of waste glycerol (WG) for enhanced bioremediation was tested in situ at an old military range site to address hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) contaminated groundwater. This treatment was effective in inducing strong reducing conditions (range: −4 to −205 mV) and increasing the concentrations of organic carbon (from 10 to 729 mg/L) and fatty acids (from 0 to 940 mg/L) concomitantly with a decrease in RDX concentrations (range: 17 to 143 μg/L) to below detection limits (0.1 μg/L) in 2 of the 3 monitoring wells (MWs) evaluated. None of these changes were observed in the control MW. RDX disappeared without the detection of any common anaerobic nitroso degradation intermediates, with the exception of one MW where the concentration of organics did not significantly increase (range: 10 to 20 mg/L), suggesting the conditions were not favourable for biodegradation. Ecotoxicological analysis suggested that the use of WG may have some dose-related deleterious effects on different soil and aquatic receptors. Analysis of the microbial community composition, using 16S rRNA gene amplicon sequences, which provided insight into whether the process design had selected for and stimulated the optimal microbial populations, indicated co-existence of numerous Operational Taxonomic Units (OTUs) belonging to groups known to be capable of RDX degradation under anaerobic conditions, with a positive link between Geobacter spp. enrichment and the presence of RDX nitroso metabolites. Overall, the results from this field test show that this treatment process can provide an effective long-term, semi-passive remediation option for RDX contaminated groundwater.

Microbial metabolism of the thawing organic carbon stores in permafrost results in a positive feedback loop of greenhouse gas emissions. CO2 and CH4 fluxes and the associated microbial communities in Arctic cryosols are important in predicting future warming potential of the Arctic. We demonstrate that topography had an impact on CH4 and CO2 flux at a high Arctic ice-wedge polygon terrain site, with higher CO2 emissions and lower CH4 uptake at troughs compared to polygon interior soils. The pmoA sequencing suggested that USCα cluster of uncultured methanotrophs is likely responsible for observed methane sink. Community profiling revealed distinct assemblages across the terrain at different depths. Deeper soils contained higher abundances of Verrucomicrobia and Gemmatimonadetes, whereas the polygon interior had higher Acidobacteria and lower Betaproteobacteria and Deltaproteobacteria abundances. Genome sequencing of isolates from the terrain revealed presence of carbon cycling genes including ones involved in serine and ribulose monophosphate pathways. A novel hybrid network analysis identified key members that had positive and negative impacts on other species. Operational Taxonomic Units (OTUs) with numerous positive interactions corresponded to Proteobacteria, Candidatus Rokubacteria and Actinobacteria phyla, while Verrucomicrobia and Acidobacteria members had negative impacts on other species. Results indicate that topography and microbial interactions impact community composition.

Water tracks in the Antarctic Dry Valleys are dark linear features of increased soil moisture that flow downslope over the spring and summer, providing a source of moisture in a cold-arid desert. They are typically sourced from melting snow, ground ice, and deliquescence (Levy et al., 2011). This research presents the first in-depth study of the activity potential and diversity of microbial communities of Antarctic water tracks. We investigated whether these water track soils are more habitable to microbial communities by ascertaining the differences in diversity, total and culturable cell counts, and microbial respiratory activity in water track soils compared with the adjacent dry soils in Pearse Valley. Total cell counts ranged from 1.47 × 10³ to 4.17 × 10⁵ cells/g dry weight soil. Water track soils had higher total and culturable biomass, in addition to higher microbial activity at 5° and −5°C, compared with adjacent dry soils. Microbial respiration was positively correlated with soil moisture content, but total cell counts and plate counts were not. Surprisingly, microbial community composition did not differ between wet and dry soil communities, and was not related to soil moisture content. The microbial community composition instead appeared to differ spatially based on location and depth. Overall, the data suggest that cold water tracks are more habitable than the surrounding cold-arid soils. Our results suggest that recurring slope lineae, which are dark linear features that grow downslope on Mars over the spring and summer, where liquid water might be a recurring phenomenon, could be sites of astrobiological potential.

Oil biodegradation has been extensively studied in the wake of the deepwater horizon spill, but the application of dispersant to oil spills in marine environments remains controversial. Here, we report metagenomic (MG) and metatranscriptomic (MT) data mining from microcosm experiments investigating the oil degrading potential of Canadian west and east coasts to estimate the gene abundance and activity of oil degrading bacteria in the presence of dispersant. We found that the addition of dispersant to crude oil mainly favours the abundance of Thalassolituus in the summer and Oleispira in the winter, two key natural oil degrading bacteria. We found a high abundance of genes related not only to n‐alkane and aromatics degradation but also associated with transporters, two‐component systems, bacterial motility, secretion systems and bacterial chemotaxis.

Greenhouse gas (GHG) emissions from Arctic permafrost soils create a positive feedback loop of climate warming and further GHG emissions. Active methane uptake in these soils can reduce the impact of GHG on future Arctic warming potential. Aerobic methane oxidizers are thought to be responsible for this apparent methane sink, though Arctic representatives of these organisms have resisted culturing efforts. Here, we first used in situ gas flux measurements and qPCR to identify relative methane sink hotspots at a high Arctic cytosol site, we then labeled the active microbiome in situ using DNA Stable Isotope Probing (SIP) with heavy 13CH4 (at 100 ppm and 1000 ppm). This was followed by amplicon and metagenome sequencing to identify active organisms involved in CH4 metabolism in these high Arctic cryosols. Sequencing of 13C-labeled pmoA genes demonstrated that type II methanotrophs (Methylocapsa) were overall the dominant active methane oxidizers in these mineral cryosols, while type I methanotrophs (Methylomarinovum) were only detected in the 100 ppm SIP treatment. From the SIP-13C-labeled DNA, we retrieved nine high to intermediate quality metagenome-assembled genomes (MAGs) belonging to the Proteobacteria, Gemmatimonadetes, and Chloroflexi, with three of these MAGs containing genes associated with methanotrophy. A novel Chloroflexi MAG contained a mmoX gene along with other methane oxidation pathway genes, identifying it as a potential uncultured methane oxidizer. This MAG also contained genes for copper import, synthesis of biopolymers, mercury detoxification, and ammonia uptake, indicating that this bacterium is strongly adapted to conditions in active layer permafrost and providing new insights into methane biogeochemical cycling. In addition, Betaproteobacterial MAGs were also identified as potential cross-feeders with methanotrophs in these Arctic cryosols. Overall, in situ SIP labeling combined with metagenomics and genome binning demonstrated to be a useful tool for discovering and characterizing novel organisms related to specific microbial functions or biogeochemical cycles of interest. Our findings reveal a unique and active Arctic cryosol microbial community potentially involved in CH4 cycling.

Biosurfactant-based dispersants (BBDs) may be more effective, cost-efficient and environmentally friendly than dispersants currently used for oil spill response. An improved understanding of BBD performance is needed to advance their development and commercial use. In this study, the ability of four BBDs, i.e. sufactins, trehalose lipids, rhamnolipids and exmulsins, alone and as various combinations to disperse Arabian light crude oil and weathered Alaska North Slope crude oil was compared to a widely used commercial oil dispersant (Corexit 9500A). Surfactin and trehalose lipids, which have balanced surface activity/emulsification ability, showed dispersion efficacy comparable to Corexit 9500A. Rhamnolipids (primarily a surface-active agent) and exmulsins (primarily an emulsifier) when used alone had significantly lower efficacy. However, blends of these surfactants had excellent dispersion performance because of synergistic effects. Balanced surface activity and emulsification ability may be key to formulate effective BBDs. Of the BBDs evaluated, surfactins with an effective dispersant-to-oil ratio as low as 1:62.3 and trehalose lipids with high oil affinity, biodegradation rate, and low toxicity characteristics show the most promise for commercial development.

Heavy crude oil (HCO) pollution has gained global attention, but traditional bioremediating practices demonstrate limited effectiveness. This study developed magnetic nanoparticles decorated bacteria (MNPB) using an oil-degrading and biosurfactant-producing Rhodococcus erythropolis species and identified a novel access-dispersion-recovery strategy for enhanced HCO pollution mitigation. The strategy entails (1) magnetic navigation of the MNPB towards HCO layer, (2) enhanced oil dispersion and formation of suspended oil-bacteria aggregates, and (3) magnetic recovery of these aggregates. The UV-spectrophotometer analysis showed that this strategy can enable up to 62% removal of HCO. The GC–MS analysis demonstrated that the MNPB enhanced the degradation of low-molecular-weight aromatics comparing with the pure bacteria, and the recovery process further removed oil-bacteria aggregates and entrained high-molecular-weight aromatics. The feasibility of using MNPB to mitigate HCO pollution could shed light on the emerging bioremediation applications.

1141488 Production of bitumen from oil sands is predicted to rise over the next decade. Some of this increased production will be transported to coastal areas for export. While some product will be transported via rail, the majority is likely to be transported through pipelines as diluted bitumen. This unconventional oil product is a mixture of the highly viscous bitumen with differing amounts of diluent, which can include condensates, synthetic crudes or conventional crudes. As a mixture of products, the behaviour of diluted bitumen may differ from conventional heavy crude oils following a spill. This is of concern in Canada as the main transportation route for exporting diluted bitumen will go through the Salish Sea, home to endangered southern resident killer whales, economically important commercial and traditional fisheries including Pacific salmon, and millions of people. Knowing how diluted bitumen products will behave and their potential impacts if a spill occurs in these coastal waters is important in developing an effective response plan. The Centre for Offshore Oil, Gas and Energy Research (COOGER) within Fisheries and Oceans Canada (DFO) has been carrying out research to characterize and predict the fate and behaviour of diluted bitumen products in marine environments over the last seven years. Using a combination of small-scale microcosms, medium-scale mesocosms, large-scale weathering and wave tank studies as well as field experiments, we have collected a broad range of data providing insights into how diluted bitumen might behave following a spill. Our research suggests that diluted bitumen will weather rapidly, with density and viscosity increasing significantly over the first 48 h. Low concentrations of hydrocarbons are typically detected in the water column, even in the presence of high energy breaking waves. The amount of weathering and water column hydrocarbons vary with season, but overall the microbial community shows a small response to the presence of diluted bitumen. Conventional spill response technologies may be used within the first 48 h of a spill, but extensive weathering will further limit their effectiveness. While the studies provide a more complete understanding of the fate and behaviour of diluted bitumen in coastal waters, there are important questions yet to be answered, some of which are presented here.

Climate change, the opening of the northwest passage, the production and transportation of oil reserves in addition to the large size and number of ocean-going vessels, are putting all Canada's oceans at an elevated risk for an oil spill. Responses to marine oil spills include physical (skimming and recovery), chemical (dispersants, herders) and biological processes (biodegradation). Natural attenuation, a weathering process that includes physical, chemical and biological action on spilled oil, is a potential remediation strategy that needs to be explored and exploited. In the Canadian context, we are using genomics approaches to better understand the natural populations of oil degrading microorganisms in our oceans, their diversity, spatial and temporal dynamics, and locations that may be more vulnerable to oil spills. The purpose of this study was to perform an evaluation of the effectiveness of an in situ microcosm experimental system to study indigenous microbial communities that have oil degrading potential and to determine whether this experimental system could have an impact on acute toxicity to various marine organisms. In situ microcosms are slitted columns that contain support matrices such as clay beads or river rocks, with or without an oil coating. Columns can be incubated in different locations, at different depths and different time periods, during which microbial biofilm develops on the support materials. By using oil coated and uncoated matrices, comparative microbial community data that demonstrates the response of the microbial community to the presence of oil can be obtained. Long-term incubations (1 year) conducted at CFS-Alert showed that known oil-degrading bacteria (Colwellia, Oleibacter, Thalassolituus, Cycloclasticus, Oceanobacter and Alcanivorax) became dominant only on the oil coated matrices, confirming their presence in the local seawater. Acute toxicity tests were performed in aquaria on a variety of test organisms to evaluate the possible effects of oil components leaching into the water from the in situ microcosms. Limited and transient toxicity to only two tested organisms (green sea urchin fertilization and green algal growth). Considering the analyses were conducted in a closed circulation system, it is highly likely that in an open ocean environment, toxicity would be negligible. Data from these studies will be valuable to support guidelines for the exploitation of natural attenuation as an alternative response measure (ARM) to address oil spills in Canadian waters.

Drinking water producers continuously develop innovative treatment processes to effectively remove organic micropollutants from raw water. Biological ion-exchange (BIEX) water treatment is one of these new techniques under development and showing great potential. In order to investigate if biodegradation is highly involved in such a removal technique, cultures were prepared with microorganisms sampled on the resins of a BIEX filter. Then, organic micropollutants were spiked into these cultures and their (bio)degradation was followed over 30 days by ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS). The purpose of this study was firstly to develop an analytical method using UHPLC-HRMS able to monitor the degradation of three spiked organic micropollutants in culture. Beyond quantification, this method allowed the simultaneous recording of fragmentation information via the use of a data-independent acquisition approach to perform a non-exhaustive search of transformation products related to the spiked micropollutants in culture aliquots. Secondly, a data treatment approach was developed to process raw spectral data generated by aliquots analysis by optimizing the precursor isolation mass windows, the accurate mass tolerance, peak intensity thresholds and choice of database. The use of this new method with a post-data acquisition treatment approach completed by the exhaustive study of fragmentation spectra allowed the tentative identification of 11 transformation products related to the spiked compounds. Finally, 16S rRNA gene amplicon sequencing revealed that bacterial genera known for their ability to degrade the spiked micropollutants were present in the microbial community of the BIEX drinking water filter.