Nitrous oxide (N2O) is a potent greenhouse gas and the predominant ozone depleting substance. The only enzyme known to reduce N2O is the nitrous oxide reductase, encoded by the nosZ gene, which is ...present among bacteria and archaea capable of either complete denitrification or only N2O reduction to di-nitrogen gas. To determine whether the occurrence of nosZ, being a proxy for the trait N2O reduction, differed among taxonomic groups, preferred habitats or organisms having either NirK or NirS nitrite reductases encoded by the nirK and nirS genes, respectively, 652 microbial genomes across 18 phyla were compared. Furthermore, the association of different co-occurrence patterns with enzymes reducing nitric oxide to N2O encoded by nor genes was examined. We observed that co-occurrence patterns of denitrification genes were not randomly distributed across taxa, as specific patterns were found to be more dominant or absent than expected within different taxonomic groups. The nosZ gene had a significantly higher frequency of co-occurrence with nirS than with nirK and the presence or absence of a nor gene largely explained this pattern, as nirS almost always co-occurred with nor. This suggests that nirS type denitrifiers are more likely to be capable of complete denitrification and thus contribute less to N2O emissions than nirK type denitrifiers under favorable environmental conditions. Comparative phylogenetic analysis indicated a greater degree of shared evolutionary history between nosZ and nirS. However 30% of the organisms with nosZ did not possess either nir gene, with several of these also lacking nor, suggesting a potentially important role in N2O reduction. Co-occurrence patterns were also non-randomly distributed amongst preferred habitat categories, with several habitats showing significant differences in the frequencies of nirS and nirK type denitrifiers. These results demonstrate that the denitrification pathway is highly modular, thus underpinning the importance of community structure for N2O emissions.
Abstract Background Heroin use and overdose deaths have increased in recent years. Emerging information suggests this is the result of increases in nonmedical use of opioid pain relievers and ...nonmedical users transitioning to heroin use. Understanding this relationship is critically important for the development of public health interventions. Methods Combined data from the 2002–2004 National Surveys on Drug Use and Health were compared to the 2008–2010 surveys to examine patterns of heroin use and risk behaviors among past year nonmedical users of opioid pain relievers. Results Between 2002–2004 and 2008–2010, past year heroin use increased among people reporting past year nonmedical use (PYNMU) of opioid pain relievers ( p < 0.01), but not among those reporting no PYNMU. Frequent nonmedical users – people reporting 100–365 days of PYNMU – had the highest rate of past year heroin use and were at increased risk for ever injecting heroin (aOR 4.3, 95% CI 2.5–7.3) and past year heroin abuse or dependence (aOR 7.8, 95% CI 4.7–12.8) compared to infrequent nonmedical users (1–29 days of PYNMU). In 2008–2010, 82.6% of frequent nonmedical users who used heroin in the past year reported nonmedical use of opioid pain relievers prior to heroin initiation compared to 64.1% in 2002–2004. Conclusions Heroin use among nonmedical users of opioid pain relievers increased between 2002–2004 and 2008–2010, with most reporting nonmedical use of opioid pain relievers before initiating heroin. Interventions to prevent nonmedical use of these drugs are needed and should focus on high-risk groups such as frequent nonmedical users of opioids.
Genomics and Ecology of Novel N2O-Reducing Microorganisms Hallin, Sara; Philippot, Laurent; Löffler, Frank E. ...
Trends in microbiology (Regular ed.),
January 2018, 2018-01-00, 20180101, 2018, 2018-01-01, Letnik:
26, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Microorganisms with the capacity to reduce the greenhouse gas nitrous oxide (N2O) to harmless dinitrogen gas are receiving increased attention due to increasing N2O emissions (and our need to ...mitigate climate change) and to recent discoveries of novel N2O-reducing bacteria and archaea. The diversity of denitrifying and nondenitrifying microorganisms with capacity for N2O reduction was recently shown to be greater than previously expected. A formerly overlooked group (clade II) in the environment include a large fraction of nondenitrifying N2O reducers, which could be N2O sinks without major contribution to N2O formation. We review the recent advances about fundamental understanding of the genomics, physiology, and ecology of N2O reducers and the importance of these findings for curbing N2O emissions.
N2O is produced in several microbial processes, but N2O reduction is limited to a single process catalyzed by the N2O reductase present among taxonomically diverse bacteria and archaea. This enzyme is used for energy conservation through anaerobic respiration, detoxification, or removal of excess electrons.
The N2O reductase has evolved into two lineages, clade I and the recently described clade II. Surveys indicate that clade II N2O reductase (NosZ) is abundant in many biomes.
Genome analyses and culture-based studies suggest that the physiology of N2O reduction differs between the clades. Evidence from community ecology supports niche differentiation of organisms with either type of N2O reductase, and within the two clades.
Identifying factors that drive physiological and ecological responses of N2O-reducing communities could lead to effective and innovative strategies to curb N2O emissions.
Microbial communities transform nitrogen (N) compounds, thereby regulating the availability of N in soil. The N cycle is defined by interacting microbial functional groups, as inorganic N‐products ...formed in one process are the substrate in one or several other processes. The nitrification pathway is often a two‐step process in which bacterial or archaeal communities oxidize ammonia to nitrite, and bacterial communities further oxidize nitrite to nitrate. Little is known about the significance of interactions between ammonia‐oxidizing bacteria (AOB) and archaea (AOA) and nitrite‐oxidizing bacterial communities (NOB) in determining the spatial variation of overall nitrifier community structure. We hypothesize that nonrandom associations exist between different AO and NOB lineages that, along with edaphic factors, shape field‐scale spatial patterns of nitrifying communities. To address this, we sequenced and quantified the abundance of AOA, AOB, and Nitrospira and Nitrobacter NOB communities across a 44‐hectare site with agricultural fields. The abundance of Nitrobacter communities was significantly associated only with AOB abundance, while that of Nitrospira was correlated to AOA. Network analysis and geostatistical modelling revealed distinct modules of co‐occurring AO and NOB groups occupying disparate areas, with each module dominated by different lineages and associated with different edaphic factors. Local communities were characterized by a high proportion of module‐connecting versus module‐hub nodes, indicating that nitrifier assemblages in these soils are shaped by fluctuating conditions. Overall, our results demonstrate the utility of network analysis in accounting for potential biotic interactions that define the niche space of nitrifying communities at scales compatible to soil management.
Mortality associated with methamphetamine use has increased markedly in the US. Understanding patterns of methamphetamine use may help inform related prevention and treatment.
To assess the national ...trends in and correlates of past-year methamphetamine use, methamphetamine use disorder (MUD), injection, frequent use, and associated overdose mortality from 2015 to 2019.
This cross-sectional study analyzed methamphetamine use, MUD, injection, and frequent use data from participants in the 2015 to 2019 National Surveys on Drug Use and Health (NSDUH). Mortality data were obtained from the 2015 to 2019 National Vital Statistics System Multiple Cause of Death files.
Methamphetamine use.
Methamphetamine use, MUD, injection, frequent use, and overdose deaths.
Of 195 711 NSDUH respondents aged 18 to 64 years, 104 408 were women (weighted percentage, 50.9%), 35 686 were Hispanic individuals (weighted percentage, 18.0%), 25 389 were non-Hispanic Black (hereafter, Black) individuals (weighted percentage, 12.6%), and 114 248 were non-Hispanic White (hereafter, White) individuals (weighted percentage, 60.6%). From 2015 to 2019, overdose deaths involving psychostimulants other than cocaine (largely methamphetamine) increased 180% (from 5526 to 15 489; P for trend <.001); methamphetamine use increased 43% (from 1.4 million 95% CI, 1.2-1.6 million to 2.0 million 95% CI, 1.7-2.3 million; P for trend = .002); frequent methamphetamine use increased 66% (from 615 000 95% CI, 512 000-717 000 to 1 021 000 95% CI, 860 000-1 183 000; P for trend = .002); methamphetamine and cocaine use increased 60% (from 402 000 95% CI, 306 000-499 000 to 645 000 95% CI, 477 000-813 000; P for trend = .001); and MUD without injection increased 105% (from 397 000 95% CI, 299 000-496 000 to 815 000 95% CI, 598 000-1 033 000; P for trend = .006). The prevalence of MUD or injection surpassed the prevalence of methamphetamine use without MUD or injection in each year from 2017 to 2019 (60% to 67% vs 37% to 40%; P for trend ≤.001). Adults with MUD or using injection were more likely to use methamphetamine frequently (52.68%-53.84% vs 32.59%; adjusted risk ratio, 1.62-1.65; 95% CI, 1.35-1.94). From 2015 to 2019, the adjusted prevalence of MUD without injection more than tripled among heterosexual women (from 0.24% to 0.74%; P < .001) and lesbian or bisexual women (from 0.21% to 0.71%; P < .001) and more than doubled among heterosexual men (from 0.29% to 0.79%; P < .001) and homosexual or bisexual men (from 0.29% to 0.80%; P = .007). It increased over 10-fold among Black individuals (from 0.06% to 0.64%; P < .001), nearly tripled among White individuals (from 0.28% to 0.78%; P < .001), and more than doubled among Hispanic individuals (from 0.39% to 0.82%; P < .001). Risk factors for methamphetamine use, MUD, injection, and frequent use included lower educational attainment, lower annual household income, lack of insurance, housing instability, criminal justice involvement, comorbidities (eg, HIV/AIDS, hepatitis B or C virus, depression), suicidal ideation, and polysubstance use.
This cross-sectional study found consistent upward trends in overdose mortality, greater risk patterns of methamphetamine use, and populations at higher risk for MUD diversifying rapidly, particularly those with socioeconomic risk factors and comorbidities. Evidence-based prevention and treatment interventions are needed to address surges in methamphetamine use and MUD.
Introduction Opioid analgesics and benzodiazepines are the prescription drugs most commonly associated with drug overdose deaths. This study was conducted to assess trends in nonmedical use−related ...emergency department (ED) visits and drug overdose deaths that involved both opioid analgesics and benzodiazepines in the U.S. from 2004 to 2011. Methods Opioid analgesic and benzodiazepine nonmedical use−related ED visits from the Drug Abuse Warning Network and drug overdose deaths from the National Vital Statistics System were analyzed for 2004−2011 to determine trends and demographic-specific rates. Data were analyzed from March 2014 to June 2014. Results From 2004 to 2011, the rate of nonmedical use–related ED visits involving both opioid analgesics and benzodiazepines increased from 11.0 to 34.2 per 100,000 population ( p- trend<0.0001). During the same period, drug overdose deaths involving both drugs increased from 0.6 to 1.7 per 100,000 ( p- trend<0.0001). Statistically significant increases in ED visits occurred among males and females, non-Hispanic whites, non-Hispanic blacks, and Hispanics, and all age groups except 12- to 17-year-olds. For overdose deaths, statistically significant increases were seen in males and females, all three race/ethnicity groups, and all age groups except 12- to 17-year-olds. Benzodiazepine involvement in opioid analgesic overdose deaths increased each year, increasing from 18% of opioid analgesic overdose deaths in 2004 to 31% in 2011 ( p- trend<0.0001). Conclusions ED visits and drug overdose deaths involving both opioid analgesics and benzodiazepines increased significantly between 2004 and 2011. Interventions to improve the appropriate prescribing and use of these medications are needed.
Introduction Opioid analgesic prescriptions are driving trends in drug overdoses, but little is known about prescribing patterns among medical specialties. We conducted this study to examine the ...opioid-prescribing patterns of the medical specialties over time. Methods IMS Health’s National Prescription Audit (NPA) estimated the annual counts of pharmaceutical prescriptions dispensed in the U.S. during 2007–2012. We grouped NPA prescriber specialty data by practice type for ease of analysis, and measured the distribution of total prescriptions and opioid prescriptions by specialty. We calculated the percentage of all prescriptions dispensed that were opioids, and evaluated changes in that rate by specialty during 2007–2012. The analysis was conducted in 2013. Results In 2012, U.S. pharmacies and long-term care facilities dispensed 4.2 billion prescriptions, 289 million (6.8%) of which were opioids. Primary care specialties accounted for nearly half of all dispensed opioid prescriptions. The rate of opioid prescribing was highest for specialists in pain medicine (48.6%); surgery (36.5%); and physical medicine/rehabilitation (35.5%). The rate of opioid prescribing rose during 2007–2010 but leveled thereafter as most specialties reduced opioid use. The greatest percentage increase in opioid-prescribing rates during 2007–2012 occurred among physical medicine/rehabilitation specialists (+12.0%). The largest percentage drops in opioid-prescribing rates occurred in emergency medicine (–8.9%) and dentistry (–5.7%). Conclusions The data indicate diverging trends in opioid prescribing among medical specialties in the U.S. during 2007–2012. Engaging the medical specialties individually is critical for continued improvement in the safe and effective treatment of pain.
The symptoms of Alzheimer disease reflect a loss of neural circuit integrity in the brain, but neurons do not work in isolation. Emerging evidence suggests that the intricate balance of interactions ...between neurons, astrocytes, microglia and vascular cells required for healthy brain function becomes perturbed during the disease, with early changes likely protecting neural circuits from damage, followed later by harmful effects when the balance cannot be restored. Moving beyond a neuronal focus to understand the complex cellular interactions in Alzheimer disease and how these change throughout the course of the disease may provide important insight into developing effective therapeutics.
The conversion of nitrite to nitric oxide in the denitrification pathway is catalyzed by at least two structurally dissimilar nitrite reductases, NirS and NirK. Although they are functionally ...equivalent, a genome with genes encoding both reductases has yet to be found. This exclusivity raises questions about the ecological equivalency of denitrifiers with either nirS or nirK, and how different ecological and evolutionary factors influence community assembly of nirS and nirK denitrifiers. Using phylogeny-based methods for analyzing community structure, we analyzed nirS and nirK data sets compiled from sequence repositories. Global patterns of phylogenetic community structure were determined using Unifrac, whereas community assembly processes were inferred using different community relatedness metrics. Similarities between globally distributed communities for both genes corresponded to similarities in habitat salinity. The majority of communities for both genes were phylogenetically clustered; however, nirK marine communities were more phylogenetically overdispersed than nirK soil communities or nirS communities. A more in-depth analysis was performed using three case studies in which a comparison of nirS and nirK community relatedness within the sites could be examined along environmental gradients. From these studies we observed that nirS communities respond differently to environmental gradients than nirK communities. Although it is difficult to attribute nonrandom patterns of phylogenetic diversity to specific niche-based or neutral assembly processes, our results indicate that coexisting nirS and nirK denitrifier communities are not under the same community assembly rules in different environments.
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