Large ecosystem-scale effects of restoration fail to mitigate impacts of land-use legacies in longleaf pine savannas.

Ecological restoration is a global priority, with potential to reverse biodiversity declines and promote ecosystem functioning. Yet, successful restoration is challenged by lingering legacies of past land-use activities, which are pervasive on lands available for restoration. Although legacies can persist for centuries following cessation of human land uses such as agriculture, we currently lack understanding of how land-use legacies affect entire ecosystems, how they influence restoration outcomes, or whether restoration can mitigate legacy effects. Using a large-scale experiment, we evaluated how restoration by tree thinning and land-use legacies from prior cultivation and subsequent conversion to pine plantations affect fire-suppressed longleaf pine savannas. We evaluated 45 ecological properties across four categories: 1) abiotic attributes, 2) organism abundances, 3) species diversity, and 4) species interactions. The effects of restoration and land-use legacies were pervasive, shaping all categories of properties, with restoration effects roughly twice the magnitude of legacy effects. Restoration effects were of comparable magnitude in savannas with and without a history of intensive human land use; however, restoration did not mitigate numerous legacy effects present prior to restoration. As a result, savannas with a history of intensive human land use supported altered properties, especially related to soils, even after restoration. The signature of past human land-use activities can be remarkably persistent in the face of intensive restoration, influencing the outcome of restoration across diverse ecological properties. Understanding and mitigating land-use legacies will maximize the potential to restore degraded ecosystems.

Dead but Not Forgotten: How Extracellular DNA, Moisture, and Space Modulate the Horizontal Transfer of Extracellular Antibiotic Resistance Genes in Soil.

Antibiotic-resistant bacteria and the spread of antibiotic resistance genes (ARGs) pose a serious risk to human and veterinary health. While many studies focus on the movement of live antibiotic-resistant bacteria to the environment, it is unclear whether extracellular ARGs (eARGs) from dead cells can transfer to live bacteria to facilitate the evolution of antibiotic resistance in nature. Here, we use eARGs from dead, antibiotic-resistant Pseudomonas stutzeri cells to track the movement of eARGs to live P. stutzeri cells via natural transformation, a mechanism of horizontal gene transfer involving the genomic integration of eARGs. In sterile, antibiotic-free agricultural soil, we manipulated the eARG concentration, soil moisture, and proximity to eARGs. We found that transformation occurred in soils inoculated with just 0.25 µg of eDNA g-1 soil, indicating that even low concentrations of soil eDNA can facilitate transformation (previous estimates suggested ∼2 to 40 µg eDNA g-1 soil). When eDNA was increased to 5 µg g-1 soil, there was a 5-fold increase in the number of antibiotic-resistant P. stutzeri cells. We found that eARGs were transformed under soil moistures typical of terrestrial systems (5 to 30% gravimetric water content) but inhibited at very high soil moistures (>30%). Overall, this work demonstrates that dead bacteria and their eARGs are an overlooked path to antibiotic resistance. More generally, the spread of eARGs in antibiotic-free soil suggests that transformation allows genetic variants to establish in the absence of antibiotic selection and that the soil environment plays a critical role in regulating transformation. IMPORTANCE Bacterial death can release eARGs into the environment. Agricultural soils can contain upwards of 109 ARGs g-1 soil, which may facilitate the movement of eARGs from dead to live bacteria through a mechanism of horizontal gene transfer called natural transformation. Here, we track the spread of eARGs from dead, antibiotic-resistant Pseudomonas stutzeri cells to live antibiotic-susceptible P. stutzeri cells in sterile agricultural soil. Transformation increased with the abundance of eARGs and occurred in soils ranging from 5 to 40% gravimetric soil moisture but was lowest in wet soils (>30%). Transformants appeared in soil after 24 h and persisted for up to 15 days even when eDNA concentrations were only a fraction of those found in field soils. Overall, our results show that natural transformation allows eARGs to spread and persist in antibiotic-free soils and that the biological activity of eDNA after bacterial death makes environmental eARGs a public health concern.

Contributions of environmental and maternal transmission to the assembly of leaf fungal endophyte communities.

Leaf fungal endophytes (LFEs) contribute to plant growth and responses to stress. Fungi colonize leaves through maternal transmission, e.g. via the seed, and through environmental transmission, e.g. via aerial dispersal. The relative importance of these two pathways in assembly and function of the LFE community is poorly understood. We used amplicon sequencing to track switchgrass (Panicum virgatum) LFEs in a greenhouse and field experiment as communities assembled from seed endophytes and rain fungi (integration of wet and dry aerial dispersal) in germinating seeds, seedlings, and adult plants. Rain fungi varied temporally and hosted a greater portion of switchgrass LFE richness (greater than 65%) than were found in seed endophytes (greater than 25%). Exposure of germinating seeds to rain inoculum increased dissimilarity between LFE communities and seed endophytes, increasing the abundance of rain-derived taxa, but did not change diversity. In the field, seedling LFE composition changed more over time, with a decline in seed-derived taxa and an increase in richness, in response to environmental transmission than LFEs of adult plants. We show that environmental transmission is an important driver of LFE assembly, and likely plant growth, but its influence depends on both the conditions at the time of colonization and plant life stage.

To Fix or Not To Fix: Controls on Free-Living Nitrogen Fixation in the Rhizosphere.

Free-living nitrogen fixation (FLNF) in the rhizosphere, or N fixation by heterotrophic bacteria living on/near root surfaces, is ubiquitous and a significant source of N in some terrestrial systems. FLNF is also of interest in crop production as an alternative to chemical fertilizer, potentially reducing production costs and ameliorating negative environmental impacts of fertilizer N additions. Despite this interest, a mechanistic understanding of controls (e.g., carbon, oxygen, nitrogen, and nutrient availability) on FLNF in the rhizosphere is lacking but necessary. FLNF is distinct from and occurs under more diverse and dynamic conditions than symbiotic N fixation; therefore, predicting FLNF rates and understanding controls on FLNF has proven difficult. This has led to large gaps in our understanding of FLNF, and studies aimed at identifying controls on FLNF are needed. Here, we provide a mechanistic overview of FLNF, including how various controls may influence FLNF in the rhizosphere in comparison with symbiotic N fixation occurring in plant nodules where environmental conditions are moderated by the plant. We apply this knowledge to a real-world example, the bioenergy crop switchgrass (Panicum virgatum), to provide context of how FLNF may function in a managed system. We also highlight future challenges to assessing FLNF and understanding how FLNF functions in the environment and significantly contributes to plant N availability and productivity.

Ni(II) coordination to mixed sites modulates DNA binding of HpNikR via a long-range effect.

Helicobacter pylori NikR (HpNikR) is a nickel-dependent transcription factor that regulates multiple genes in the H. pylori pathogen. There are conflicting data regarding the locations of the Ni(II) sites and the role of Ni(II) coordination in DNA recognition. Herein, we report crystal structures of (i) the metal-binding domain (MBD) of HpNikR (3.08 Å) and (ii) a mutant, H74A (2.04 Å), designed to disrupt native Ni(II) coordination. In the MBD structure, four nickel ions are coordinated to two different types of nickel sites (4-coordinate, square planar, and 5/6-coordinate, square pyramidal/octahedral). In the H74A structure, all four nickel ions are coordinated to 4-coordinate square-planar sites. DNA-binding studies reveal tighter binding for target DNA sequences for holo-HpNikR compared with the affinities of Ni(II) reconstituted apo-HpNikR and H74A for these same DNA targets, supporting a role for Ni(II) coordination to 5/6 sites in DNA recognition. Small-angle X-ray scattering studies of holo-HpNikR and H74A reveal a high degree of conformational flexibility centered at the DNA-binding domains of H74A, which is consistent with disorder observed in the crystal structure of the protein. A model of DNA recognition by HpNikR is proposed in which Ni(II) coordination to specific sites in the MBD have a long-range effect on the flexibility of the DNA-binding domains and, consequently, the DNA recognition properties.

Climate change alters ecological strategies of soil bacteria.

The timing and magnitude of rainfall events are expected to change in future decades, resulting in longer drought periods and larger rainfall events. Although microbial community composition and function are both sensitive to changes in rainfall, it is unclear whether this is because taxa adopt strategies that maximise fitness under new regimes. We assessed whether bacteria exhibited phylogenetically conserved ecological strategies in response to drying-rewetting, and whether these strategies were altered by historical exposure to experimentally intensified rainfall patterns. By clustering relative abundance patterns, we identified three discrete ecological strategies and found that tolerance to drying-rewetting increased with exposure to intensified rainfall patterns. Changes in strategy were primarily due to changes in community composition, but also to strategy shifts within taxa. These moisture regime-selected ecological strategies may be predictable from disturbance history, and are likely to be linked to traits that influence the functional potential of microbial communities.

Is bacterial moisture niche a good predictor of shifts in community composition under long-term drought?

Both biogeographical and rainfall manipulation studies show that soil water content can be a strong driver of microbial community composition. However, we do not yet know if these patterns emerge because certain bacterial taxa are better able to survive at dry soil moisture regimes or if they are due to other drought-sensitive ecosystem properties indirectly affecting microbial community composition. In this study, we evaluated (1) whether bacterial community composition changed under an 11-year drought manipulation and (2) whether shifts under drought could be explained by variation in the moisture sensitivity of growth among bacterial taxa (moisture niche partitioning). Using 454 pyrosequencing of 16S rRNA, we observed shifts in bacterial community composition under drought, coincident with changes in other soil properties. We wet-up dry soils from drought plots to five moisture levels, and measured respiration and the composition of actively growing communities using bromodeoxyuridine (BrdU) labeling of DNA. The field drought experiment affected the composition of the active community when incubated at different moisture levels in the laboratory, as well as short-term (36-hour) respiration rates. Independent of history, bacterial communities also displayed strong niche partitioning across the wet-up moisture gradient. Although this indicates that moisture has the potential to drive bacterial community composition under long-term drought, species distributions predicted by response to moisture did not reflect the community composition of plots that were subjected to long-term drought. Bacterial community structure was likely more strongly driven by other environmental factors that changed under long-term drought, or not shaped by response to water level upon wet-up. The approach that we present here for linking niches to community composition could be adapted for other environmental variables to aid in predicting microbial species distributions and community responses to environmental change.

Switching between menthol and nonmenthol cigarettes: findings from the U.S. Cohort of the International Tobacco Control Four Country Survey.

INTRODUCTION: This article examines trends in switching between menthol and nonmenthol cigarettes, smoker characteristics associated with switching, and associations among switching, indicators of nicotine dependence, and quitting activity. METHODS: Participants were 5,932 U.S. adult smokers who were interviewed annually as part of the International Tobacco Control Four Country Survey between 2002 and 2011. Generalized estimating equations (GEEs) were used to examine the prevalence of menthol cigarette use and switching between menthol and nonmenthol cigarettes (among 3,118 smokers who participated in at least 2 consecutive surveys). We also evaluated characteristics associated with menthol cigarette use and associations among switching, indicators of nicotine dependence, and quitting activity using GEEs. RESULTS: Across the entire study period, 27% of smokers smoked menthol cigarettes; prevalence was highest among Blacks (79%), young adults (36%), and females (30%). Prevalence of switching between menthol and nonmenthol cigarettes was low (3% switched to menthol and 8% switched to nonmenthol), and switchers tended to revert back to their previous type. Switching types was not associated with indicators of nicotine dependence or quit attempts. However, those who switched cigarette brands within cigarette types were more likely to attempt to quit smoking. CONCLUSIONS: While overall switching rates were low, the percentage who switched from menthol to nonmenthol was significantly higher than the percentage who switched from nonmenthol to menthol. An asymmetry was seen in patterns of switching such that reverting back to menthol was more common than reverting back to nonmenthol, particularly among Black smokers.

Electronic cigarettes: abuse liability, topography and subjective effects.

OBJECTIVE: To review the available evidence evaluating the abuse liability, topography, subjective effects, craving and withdrawal suppression associated with e-cigarette use in order to identify information gaps and provide recommendations for future research. METHODS: Literature searches were conducted between October 2012 and January 2014 using five electronic databases. Studies were included in this review if they were peer-reviewed scientific journal articles evaluating clinical laboratory studies, national surveys or content analyses. RESULTS: A total of 15 peer-reviewed articles regarding behavioural use and effects of e-cigarettes published between 2010 and 2014 were included in this review. Abuse liability studies are limited in their generalisability. Topography (consumption behaviour) studies found that, compared with traditional cigarettes, e-cigarette average puff duration was significantly longer, and e-cigarette use required stronger suction. Data on e-cigarette subjective effects (such as anxiety, restlessness, concentration, alertness and satisfaction) and withdrawal suppression are limited and inconsistent. In general, study data should be interpreted with caution, given limitations associated with comparisons of novel and usual products, as well as the possible effects associated with subjects' previous experience/inexperience with e-cigarettes. CONCLUSIONS: Currently, very limited information is available on abuse liability, topography and subjective effects of e-cigarettes. Opportunities to examine extended e-cigarette use in a variety of settings with experienced e-cigarette users would help to more fully assess topography as well as behavioural and subjective outcomes. In addition, assessment of 'real-world' use, including amount and timing of use and responses to use, would clarify behavioural profiles and potential adverse health effects.

Abuse potential of non-nicotine tobacco smoke components: acetaldehyde, nornicotine, cotinine, and anabasine.

INTRODUCTION: This review identified published animal studies evaluating the possible abuse potential of acetaldehyde, nornicotine, cotinine, and anabasine based on five commonly used paradigms. These include their effects on midbrain dopamine (DA) levels, drug discrimination and substitution for known drugs of abuse, place conditioning, self-administration behavior, and somatic withdrawal symptoms. RESULTS: Acetaldehyde had mixed effects on midbrain DA levels and drug discrimination; however, it consistently produced a conditioned place preference and supported self-administration. The single available study on withdrawal found that cessation of acetaldehyde administration resulted in a somatic withdrawal syndrome. Nornicotine increased DA in the midbrain, especially in the nucleus accumbens. Although there are no data on place conditioning, it substituted for nicotine in drug discrimination testing, partially substituted for cocaine and amphetamine, and, though only a single study, supported self-administration. Anabasine increased midbrain DA levels and that it partially substituted for nicotine in drug discrimination testing. Cotinine increased midbrain DA levels and substituted for nicotine. CONCLUSIONS: The existing literature suggests that acetaldehyde and nornicotine likely possess abuse potential, with anabasine having possible abuse potential. Although some cotinine data were available, it was insufficient to draw conclusions about possible abuse potential. Further research is needed to determine the role of minor alkaloids on tobacco dependence.

Regional biogeography versus intra-annual dynamics of the root and soil microbiome.

BACKGROUND: Root and soil microbial communities constitute the below-ground plant microbiome, are drivers of nutrient cycling, and affect plant productivity. However, our understanding of their spatiotemporal patterns is confounded by exogenous factors that covary spatially, such as changes in host plant species, climate, and edaphic factors. These spatiotemporal patterns likely differ across microbiome domains (bacteria and fungi) and niches (root vs. soil). RESULTS: To capture spatial patterns at a regional scale, we sampled the below-ground microbiome of switchgrass monocultures of five sites spanning > 3 degrees of latitude within the Great Lakes region. To capture temporal patterns, we sampled the below-ground microbiome across the growing season within a single site. We compared the strength of spatiotemporal factors to nitrogen addition determining the major drivers in our perennial cropping system. All microbial communities were most strongly structured by sampling site, though collection date also had strong effects; in contrast, nitrogen addition had little to no effect on communities. Though all microbial communities were found to have significant spatiotemporal patterns, sampling site and collection date better explained bacterial than fungal community structure, which appeared more defined by stochastic processes. Root communities, especially bacterial, were more temporally structured than soil communities which were more spatially structured, both across and within sampling sites. Finally, we characterized a core set of taxa in the switchgrass microbiome that persists across space and time. These core taxa represented < 6% of total species richness but > 27% of relative abundance, with potential nitrogen fixing bacteria and fungal mutualists dominating the root community and saprotrophs dominating the soil community. CONCLUSIONS: Our results highlight the dynamic variability of plant microbiome composition and assembly across space and time, even within a single variety of a plant species. Root and soil fungal community compositions appeared spatiotemporally paired, while root and soil bacterial communities showed a temporal lag in compositional similarity suggesting active recruitment of soil bacteria into the root niche throughout the growing season. A better understanding of the drivers of these differential responses to space and time may improve our ability to predict microbial community structure and function under novel conditions.

Fungal Communities on Standing Litter Are Structured by Moisture Type and Constrain Decomposition in a Hyper-Arid Grassland.

Non-rainfall moisture (fog, dew, and water vapor; NRM) is an important driver of plant litter decomposition in grasslands, where it can contribute significantly to terrestrial carbon cycling. However, we still do not know whether microbial decomposers respond differently to NRM and rain, nor whether this response affects litter decomposition rates. To determine how local moisture regimes influence decomposer communities and their function, we examined fungal communities on standing grass litter at an NRM-dominated site and a rain-dominated site 75 km apart in the hyper-arid Namib Desert using a reciprocal transplant design. Dominant taxa at both sites consisted of both extremophilic and cosmopolitan species. Fungal communities differed between the two moisture regimes with environment having a considerably stronger effect on community composition than did stage of decomposition. Community composition was influenced by the availability of air-derived spores at each site and by specialization of fungi to their home environment; specifically, fungi from the cooler, moister NRM Site performed worse (measured as fungal biomass and litter mass loss) when moved to the warmer, drier rain-dominated site while Rain Site fungi performed equally well in both environments. Our results contribute to growing literature demonstrating that as climate change alters the frequency, magnitude and type of moisture events in arid ecosystems, litter decomposition rates may be altered and constrained by the composition of existing decomposer communities.

Why Plants Harbor Complex Endophytic Fungal Communities: Insights From Perennial Bunchgrass Stipagrostis sabulicola in the Namib Sand Sea.

All perennial plants harbor diverse endophytic fungal communities, but why they tolerate these complex asymptomatic symbioses is unknown. Using a multi-pronged approach, we conclusively found that a dryland grass supports endophyte communities comprised predominantly of latent saprophytes that can enhance localized nutrient recycling after senescence. A perennial bunchgrass, Stipagrostis sabulicola, which persists along a gradient of extreme abiotic stress in the hyper-arid Namib Sand Sea, was the focal point of our study. Living tillers yielded 20 fungal endophyte taxa, 80% of which decomposed host litter during a 28-day laboratory decomposition assay. During a 6-month field experiment, tillers with endophytes decomposed twice as fast as sterilized tillers, consistent with the laboratory assay. Furthermore, profiling the community active during decomposition using next-generation sequencing revealed that 59-70% of the S. sabulicola endophyte community is comprised of latent saprophytes, and these dual-niche fungi still constitute a large proportion (58-62%) of the litter community more than a year after senescence. This study provides multiple lines of evidence that the fungal communities that initiate decomposition of standing litter develop in living plants, thus providing a plausible explanation for why plants harbor complex endophyte communities. Using frequent overnight non-rainfall moisture events (fog, dew, high humidity), these latent saprophytes can initiate decomposition of standing litter immediately after tiller senescence, thus maximizing the likelihood that plant-bound nutrients are recycled in situ and contribute to the nutrient island effect that is prevalent in drylands.

Impacts of nitrogen addition on switchgrass root-associated diazotrophic community structure and function.

Cellulosic bioenergy crops, like switchgrass (Panicum virgatum), have potential for growth on lands unsuitable for food production coupled with potential for climate mitigation. Sustainability of these systems lies in identifying conditions that promote high biomass yields on marginal lands under low-input agricultural practices. Associative nitrogen fixation (ANF) is a potentially important nitrogen (N) source for these crops, yet ANF contributions to plant N, especially under fertilizer N addition are unclear. In this study, we assess structure (nifH) and function (ANF) of switchgrass root-associated diazotrophic communities to long-term and short-term N additions using soil from three marginal land sites. ANF rates were variable and often unexpectedly high, sometimes 10× greater than reported in the literature, and did not respond in repeatable ways to long-term or short-term N. We found few impacts of N addition on root-associated diazotrophic community structure or membership. Instead, we found a very consistent root-associated diazotrophic community even though switchgrass seeds were germinated in soil from field sites with distinct diazotrophic communities. Ultimately, this work demonstrates that root-associated diazotrophic communities have the potential to contribute to switchgrass N demands, independent of N addition, and this may be driven by selection of the diazotrophic community by switchgrass roots.

Influence of verbal recall of a recent stress experience on anxiety and desire for cocaine in non-treatment seeking, cocaine-addicted volunteers.

It has long been postulated that stress increases the risk of drug abuse and relapse. The principal goal of this project was to evaluate the effects of verbal recall of a recent stress experience (specifically meaningful to each individual) on physiological and subjective measures in cocaine-addicted participants. Subjects described a recent stressful non-drug-related experience and a neutral non-stressful experience, and then completed mood and drug effect questionnaires, while heart rate and blood pressure were recorded. Participants (N = 25) were predominantly African American and male. As a group, participants used cocaine for more than 15 years and approximately 18 of the last 30 days, and a majority reported use of nicotine and/or alcohol. All participants were evaluated during a time in which they tested positive for cocaine metabolite. On a scale of 1-10, participants reported their verbal recall of a recent stress event as highly stressful and their verbal recall of a recent neutral event as non-stressful (p < 0.0001). The self-reported vividness of this recall was high (>8 out of 10) for both the stress and neutral events. Heart rate and systolic and diastolic blood pressure did not differ after verbal recall of either stress or neutral events. Similarly, self-reported subjective effects (including ratings of anxiety and craving for cocaine) did not differ after verbal recall of either stress or neutral events. In summary, despite the fact that participants recounted highly stressful and vivid memories, this experience did not elicit significant changes in cardiovascular or subjective effects. These data suggest that simply recalling a stressful event may not be a sufficient enough stimulus to contribute to craving or relapse in cocaine-addicted individuals.

The biology of fog: results from coastal Maine and Namib Desert reveal common drivers of fog microbial composition.

Fog supplies water and nutrients to systems ranging from coastal forests to inland deserts. Fog droplets can also contain bacterial and fungal aerosols, but our understanding of fog biology is limited. Using metagenomic tools and culturing, we provide a unique look at fungal and bacterial communities in fog at two fog-dominated sites: coastal Maine (USA) and the Namib Desert (Namibia). Microbial communities in the fog at both sites were diverse, distinct from clear aerosols, and influenced by both soil and marine sources. Fog from both sites contained Actinobacteria and Firmicutes, commonly soil- and air-associated phyla, but also contained bacterial taxa associated with marine environments including Cyanobacteria, Oceanospirillales, Novosphingobium, Pseudoalteromonas, and Bradyrhizobiaceae. Marine influence on fog communities was greatest near the coast, but still evident in Namib fogs 50 km inland. In both systems, differences between pre- and post-fog aerosol communities suggest that fog events can significantly alter microbial aerosol diversity and composition. Fog is likely to enhance viability of transported microbes and facilitate their deposition, making fog biology ecologically important in fog-dominated environments. Fog may introduce novel species to terrestrial ecosystems, including human and plant pathogens, warranting further work on the drivers of this important and underrecognized aerobiological transfer between marine and terrestrial systems.

Predictors of cardiovascular response to methamphetamine administration in methamphetamine-dependent individuals.

The goal of the present investigation was to determine predictors of cardiovascular response to methamphetamine administrated in the laboratory. Heart rate (HR) and blood pressure (BP) were measured at baseline and at several time points following the administration of methamphetamine or saline placebo. One-way ANOVA was used to determine the differences between female and male subjects in their cardiovascular response. In male subjects, linear regression and one-way ANOVA were used to determine the influence of potential predictors on cardiovascular response, including age, weight, drug use indicators, concurrent use of other substances, route of administration, and race. Methamphetamine administration provoked significant increases in HR and BP, as compared to placebo. Female gender was associated with larger peak change in diastolic BP following administration. Baseline HR and BP were found to be strong predictors of cardiovascular response to methamphetamine administration in male subjects. Lifetime use and recent use of methamphetamine and nicotine did not predict cardiovascular response to methamphetamine. Recent alcohol use was associated with increased peak change in diastolic BP. Also, current use of cannabis was negatively correlated with peak HR change. Male cannabis users show lower peak change in HR as compared to non-cannabis users. As compared to methamphetamine smokers, intravenous users demonstrated higher peak change in diastolic BP following drug administration. Race did not have a significant effect on cardiovascular response. Taken together, these findings may help in the prevention and treatment of cardiovascular events in a population at high risk of premature morbidity and mortality.

Understanding how microbiomes influence the systems they inhabit.

Translating the ever-increasing wealth of information on microbiomes (environment, host or built environment) to advance our understanding of system-level processes is proving to be an exceptional research challenge. One reason for this challenge is that relationships between characteristics of microbiomes and the system-level processes that they influence are often evaluated in the absence of a robust conceptual framework and reported without elucidating the underlying causal mechanisms. The reliance on correlative approaches limits the potential to expand the inference of a single relationship to additional systems and advance the field. We propose that research focused on how microbiomes influence the systems they inhabit should work within a common framework and target known microbial processes that contribute to the system-level processes of interest. Here, we identify three distinct categories of microbiome characteristics (microbial processes, microbial community properties and microbial membership) and propose a framework to empirically link each of these categories to each other and the broader system-level processes that they affect. We posit that it is particularly important to distinguish microbial community properties that can be predicted using constituent taxa (community-aggregated traits) from those properties that cannot currently be predicted using constituent taxa (emergent properties). Existing methods in microbial ecology can be applied to more explicitly elucidate properties within each of these three categories of microbial characteristics and connect them with each other. We view this proposed framework, gleaned from a breadth of research on environmental microbiomes and ecosystem processes, as a promising pathway with the potential to advance discovery and understanding across a broad range of microbiome science.

Maximizing smoking cessation in clinical practice: pharmacologic and behavioral interventions.

Clinicians are in a unique position to reduce cardiovascular morbidity and mortality by helping their patients quit smoking. At each visit, clinicians should document smoking status, provide strong and clear advice to quit, and recommend and prescribe pharmacotherapy for patients who are motivated to quit, which can double the odds of success. Effective pharmacotherapies include nicotine replacement, bupropion, and varenicline, which was recently approved by the Food and Drug Administration. Behavioral counseling to develop a quit plan and extended follow-up are critical to maximize quit rates but are rarely provided by clinicians due to time constraints and lack of expertise. As an alternative, the authors recommend referral to telephone quitlines that provide no-cost behavioral counseling by specialists. Hospitals should implement systemwide procedures to ensure that smokers are identified at admission and trained staff is available to provide smoking cessation consults that include a minimum of 20 minutes of inpatient counseling with follow-up for at least 1 month.