Development of Opioid Use Disorder After Breast Reconstruction: Effects of Nicotine Exposure.

INTRODUCTION: After undergoing breast reconstructive surgery, patients are typically prescribed opioids. Smoking tobacco increases rate of opioid metabolism and is associated with development of opioid use disorder (OUD). The aim of this study was to determine whether patients who smoke have an increased risk of OUD after breast reconstructive surgery. Given that OUD is a known risk factor for injection drug use and intravenous drug use increases risk of acquiring blood-borne diseases including human immunodeficiency virus (HIV) and hepatitis, the secondary aim was to determine if these patients are also at increased risk of acquiring these communicable diseases associated with OUD. METHODS: A retrospective analysis was conducted using TriNetX, a multi-institutional deidentified database. Individuals included underwent a breast reconstructive surgery and received postoperative opioid treatment. The exposed group included patients who smoke. The control group did not smoke. Risk of developing OUD, hepatitis B virus (HBV), hepatitis C virus (HCV), and HIV from 12 to 36 months after surgery was compared between groups. Patients with preexisting OUD or associated diseases were excluded. Cohorts were matched to control for confounding factors including age, sex, race, mental health history, and concomitant substance use. RESULTS: There were 8648 patients included in the analysis. After matching, 4324 patients comprised the exposure group, and 4324 patients remained in the control group. Preoperative smoking was significantly associated with increased risk of OUD at 12, 24, and 36 months after breast reconstruction (36 months: odds ratio [OR], 2.722; confidence interval [CI], 2.268-6.375). Smoking was also associated with increased risk of HIV and HCV at all time points after surgery (36 months HIV: OR, 2.614; CI, 1.977-3.458; 36 months HCV: OR, 3.718; CI, 2.268-6.375) and increased risk of HBV beginning at 24 months after surgery (36 months HBV: OR, 2.722; CI, 1.502-4.935). CONCLUSIONS: Individuals who smoke have an increased risk of developing OUD, HIV, HCV, and HBV after breast reconstructive surgery. This risk persists for at least 3 years after surgery. Additional research and clinical interventions focusing on early identification of OUD, prevention efforts, and harm reduction strategies for patients who smoke or have nicotine dependence undergoing breast reconstruction are warranted.

Incidence of tethered cord syndrome in neurofibromatosis types 1 and 2 pediatric patients: a population-level analysis.

PURPOSE: Tethered spinal cord syndrome (TCS) is characterized by cutaneous attachments on the filum terminale that stretch the spinal cord, leading to musculoskeletal and urogenital sequelae. While the neurocutaneous associations with TCS remain undefined, a recent study reports a high incidence of TCS among a pediatric neurofibromatosis (NF) cohort. This present study utilizes a population-level database to estimate TCS incidence among pediatric patients with neurofibromatosis types 1 and 2 (NF1, NF2). METHODS: The TriNetX Research Network was queried to identify patients diagnosed with NF and/or TCS before the age of 21. Symptomatic TCS requiring surgical intervention was identified using corresponding procedural codes within 12 months following TCS diagnosis. Odds ratios (OR) were calculated to measure the associations of NF1/NF2 with TCS. RESULTS: 19,426 pediatric NF patients were evaluated (NF1: 18,383, NF2: 1042). The average ages of TCS diagnosis among NF1, NF2, and non-NF patients were 12, 16, and 9 years, respectively. The incidence of TCS was 1.2% in NF1 patients and 7.3% in NF2 patients, compared to 0.074% in the general population. The associations of NF incidence with TCS were significantly increased in both NF1 (OR 16.42; 14.38-18.76) and NF2 (OR 105.58; 83.56-133.40) patients compared to the general population. Symptomatic TCS requiring surgical intervention was not significantly associated with NF1/NF2 patients compared to the general TCS population. CONCLUSION: This analysis demonstrates a high incidence of TCS but delayed intervention in pediatric NF patients. Considering TCS counseling, spinal MRI, and earlier intervention may be warranted for NF patients experiencing musculoskeletal symptomatology.

Shifts in bacterial traits under chronic nitrogen deposition align with soil processes in arbuscular, but not ectomycorrhizal-associated trees.

Nitrogen (N) deposition increases soil carbon (C) storage by reducing microbial activity. These effects vary in soil beneath trees that associate with arbuscular (AM) and ectomycorrhizal (ECM) fungi. Variation in carbon C and N uptake traits among microbes may explain differences in soil nutrient cycling between mycorrhizal associations in response to high N loads, a mechanism not previously examined due to methodological limitations. Here, we used quantitative Stable Isotope Probing (qSIP) to measure bacterial C and N assimilation rates from an added organic compound, which we conceptualize as functional traits. As such, we applied a trait-based approach to explore whether variation in assimilation rates of bacterial taxa can inform shifts in soil function under chronic N deposition. We show taxon-specific and community-wide declines of bacterial C and N uptake under chronic N deposition in both AM and ECM soils. N deposition-induced reductions in microbial activity were mirrored by declines in soil organic matter mineralization rates in AM but not ECM soils. Our findings suggest C and N uptake traits of bacterial communities can predict C cycling feedbacks to N deposition in AM soils, but additional data, for instance on the traits of fungi, may be needed to connect microbial traits with soil C and N cycling in ECM systems. Our study also highlights the potential of employing qSIP in conjunction with trait-based analytical approaches to inform how ecological processes of microbial communities influence soil functioning.

Simultaneous versus staged bilateral carpal tunnel release via open and endoscopic surgeries: a retrospective propensity score-matched patient comorbidity analysis.

OBJECTIVE: Carpal tunnel syndrome (CTS) presents bilaterally in nearly 60%-70% of affected patients. Bilateral carpal tunnel release (CTR) can be performed in a staged or simultaneous fashion. There remains a limited understanding of the optimal preoperative factors to use for patient selection when determining simultaneous versus staged bilateral CTR. Moreover, it is unclear how these factors influence postoperative outcomes. In this study, the authors aimed to identify and compare preoperative comorbidities and postoperative outcomes in patients who had undergone simultaneous versus staged open and endoscopic bilateral CTR. METHODS: The authors performed a retrospective analysis of data collected from the TriNetX database. Patients with bilateral CTS who had been treated from February 1, 2002, to February 1, 2022, were dichotomized by their bilateral release approach: simultaneous or staged within 3 months. The resulting groups were analyzed separately by open versus endoscopic techniques. Next, cohorts were analyzed for preoperative comorbidities to identify possible factors for surgical determination. Then, they were propensity score matched on demographics and comorbidities. Postoperative outcomes within 6 months of surgery were measured with and without matching. RESULTS: After matching, 9286 and 3709 patients remained in the open and endoscopic groups, respectively. Those who had undergone staged surgeries via an open or endoscopic approach had more preoperative comorbidities. After matching, staged open release was associated with significantly higher rates of postprocedural care, hand/joint pain, limb pain, trigger finger, and upper respiratory tract infections. Simultaneous open release was associated with higher rates of emergency room visits. Staged endoscopic release was associated with significantly higher rates of postprocedural care, limb pain, and trigger finger. No significant outcomes were favored in the simultaneous endoscopic group. CONCLUSIONS: Before matching, patients who had undergone staged CTR had significantly higher rates of preoperative medical comorbidities compared with patients in the simultaneous CTR group. Moreover, staged CTR was significantly associated with higher rates of postoperative complications. After matching on demographics and comorbidities, staged CTR was still associated with higher rates of postoperative complications, suggesting that preoperative comorbidities do not influence postoperative outcome. Further prospective studies could be used to validate these results and provide new findings for the management and treatment of these groups.

Procainamide-Provoked Brugada Pattern in a Patient Presenting with New-Onset Atrial Fibrillation or Flutter: When Does it Matter?

BACKGROUND: Brugada syndrome (BrS) is an inherited disease that can lead to sudden cardiac death. Medications, such as antidysrhythmics, and fevers can unmask or induce the Brugada pattern on an electrocardiogram (ECG). This case report highlights a patient who developed drug-induced Brugada type I pattern after a procainamide infusion for the treatment of new-onset atrial fibrillation (AF) or flutter and discusses the implications for this incidental but potentially lethal finding. CASE REPORT: We report a case of a young man who presented to the emergency department (ED) with new-onset AF with rapid ventricular response that began within 12 h of presentation. ED treatments included a crystalloid IV fluid bolus, diltiazem pushes, synchronized electrical cardioversion, and a procainamide infusion. After the procainamide infusion, the patient developed ECG findings consistent with Brugada pattern. Both the AF and Brugada pattern resolved spontaneously within 24 h. The patient was discharged without implantable cardioverter defibrillator placement due to presumed isolated procainamide-induced Brugada pattern and lack of concerning features, such as inducible dysrhythmia during electrophysiology study, family history of sudden death, and history of syncope. The patient was counseled to follow-up with genetics and avoid BrS-inducing medications. WHY SHOULD AN EMERGENCY PHYSICIANS BE AWARE OF THIS?: Procainamide, an option for the treatment of AF in the ED, can provoke Brugada pattern. If encountered, it is important to recall that some patients may not be diagnosed with BrS if determined to be low risk according to the Shanghai criteria. All patients should be referred to cardiology for further evaluation.

A single-center descriptive account of the use of pectoral nerve I and II nerve blocks for post-operative pain relief following pediatric sternotomy.

Regional anesthesia between the pectoralis major and minor was first described in 2011 as an alternative method to paravertebral blocks or epidurals for post-operative mastectomies. Since then, the use of pectoral nerve (PECS) blocks for post-operative pain management following thoracotomy, sternotomy, and other procedures in the anterior thorax has increased. While experience with this block is growing, the current understanding of its use in pediatric patients is limited. We reviewed pediatric cases at a single institution and provide a descriptive account of our use of PECS I and II blocks for post-operative pain management following operations involving sternotomy in pediatric patients. We performed a retrospective database analysis of the use of PECS I and II blocks following procedures requiring sternotomy from 2018 to 2021 at St. Louis Children's Hospital. Patients 21 years old and younger who received either a PECS I or II block following a sternotomy for a cardiac procedure were included in the analysis. Patient's demographics, pre-, intra-, and post-operative medications, operative time, extubation status, pain evaluations, and hospital course were assessed from the electronic medical record. From 2018 to 2021, 73 ultrasound-guided PECS blocks were performed for pain relief for pediatric sternotomy. The most commonly performed operations were atrial septal defect closure (n = 12), mitral valve repair (n = 8), and ventricle septal defect closure (n = 8). Out of the 73 patients, 47 received a PECS I block and 26 received a PECS II Block. 70 of the blocks were administered after closure of the sternum while 3 were done before incision. The time to perform blocks took on average of 6 (±4) min. Mean operating room time was 7.5 h. Local anesthetics used for the blocks were as follows: Ropivacaine 0.2% (n = 54), Ropivacaine 0.5% (n = 18), and Bupivacaine 0.25% (n = 1). Twenty-five out of 73 patients did not experience severe pain, defined as ≥7/10 on a numeric pain scale, at any point in the first 24 h following surgery. We describe the of use PECS I and II nerve block following pediatric sternotomy. Blocks were straight forward to perform, and typically took a short amount of time to administer (6 min), when compared to the total operating room time (7.5 h). While this study did not include a comparative group that did not receive a block, 34 percent of patients did not suffer from severe pain in the first 24 h following surgery. Further prospective studies are needed to assess the effectiveness of PECS blocks for pain relief following sternotomy in pediatric patients when compared to current standard of care. PECS blocks may be beneficial for a range of cardiac surgeries that typically result in severe postoperative pain.

Evenness of soil organic carbon chemical components changes with tree species richness, composition and functional diversity across forests in China.

Higher tree species richness generally increases the storage of soil organic carbon (SOC). However, less attention is paid to the influence of varied tree species composition on SOC storage. Recently, the perspectives for the stronger persistence of SOC caused by the higher molecular diversity of organic compounds were proposed. Therefore, the influences of tree species richness and composition on the molecular diversity of SOC need to be explored. In this study, an index of the evenness of diverse SOC chemical components was proposed to represent the potential resistance of SOC to decomposition under disturbances. Six natural forest types were selected encompassing a diversity gradient, ranging from cold temperate to tropical forests. We examined the correlations of tree species richness, composition, and functional diversity, with the evenness of SOC chemical components at a molecular level by 13 C nuclear magnetic resonance. Across the range, tree species richness correlated to the evenness of SOC chemical components through tree species composition. The negative correlation of evenness of SOC chemical components with tree species composition, and the positive correlation of evenness of SOC chemical components with tree functional diversity were found. These indicate the larger difference in tree species composition and the lower community functional diversity resulted in the higher heterogeneity of SOC chemical components among the communities. The positive correlation of the evenness of SOC chemical components with the important value of indicator tree species, further revealed the specific tree species contributing to the higher evenness of SOC chemical components in each forest type. Soil fungal and bacterial α-diversity had effect on the evenness of SOC chemical components. These findings suggest that the indicator tree species conservation might be preferrable to simply increasing tree species richness, for enhancing the potential resistance of SOC to decomposition.

Fungivorous nematodes drive microbial diversity and carbon cycling in soil.

Soil bacteria and fungi mediate terrestrial biogeochemical cycling, but we know relatively little about how trophic interactions influence their community composition, diversity, and function. Specifically, it is unclear how consumer populations affect the activity of microbial taxa they consume, and therefore the interaction of those taxa with other members of the microbial community. Due to its extreme diversity, studying trophic dynamics in soil is a complex feat. Seeking to address these challenges, we performed a microcosm-based consumer manipulation experiment to determine the impact of a common fungal-feeding nematode (Aphelenchus avenae) on soil microbial community composition, diversity, and activity (e.g., C cycling parameters). Fungivory decreased fungal and bacterial α-diversity and stimulated C and N cycling, possibly via cascading impacts of fungivory on bacterial communities. Our results present experimental evidence that soil trophic dynamics are intimately linked with microbial diversity and function, factors that are key in understanding global patterns in biogeochemical cycling.

Tumor-Derived Biomarkers in Liquid Biopsy of Glioblastoma.

There is a pressing clinical need for minimally invasive liquid biopsies to supplement imaging in the treatment of glioblastoma. Diagnostic imaging is often difficult to interpret and the medical community is divided on distinguishing among complete response, partial response, stable disease, and progressive disease. A minimally invasive liquid biopsy would supplement imaging and clinical findings and has the capacity to be helpful in several ways: 1) diagnosis, 2) selection of patients for specific treatments, 3) tracking of treatment response, and 4) prognostic value. The liquid biome is the combination of biological fluids including blood, urine, and cerebrospinal fluid that contain small amounts of tumor cells, DNA/RNA coding material, peptides, and metabolites. Within the liquid biome, 2 broad categories of biomarkers can exist: tumor-derived, which can be directly traced to the tumor, and tumor-associated, which can be traced back to the response of the body to disease. Although tumor-associated biomarkers are promising liquid biopsy candidates, recent advances in biomarker enrichment and detection have allowed concentration on a new class of biomarker: tumor-derived biomarkers. This review focuses on making the distinction between the 2 biomarker categories and highlights promising new direction.

Analysis of ophthalmology subspecialty opioid prescribing patterns during the opioid public health crisis.

OBJECTIVE: To describe opioid prescribing practices of ophthalmology subspecialties and determine whether opioid prescribing has decreased during the public health crisis. DESIGN: Retrospective cohort study. PARTICIPANTS: Ophthalmologists prescribing at least 11 medications billed to the Medicare Part D prescription drug plan. METHODS: Publicly available Medicare data sets based on claims from the years 2016, 2017, and 2018 were used. Fellowship status was assumed based on subspecialty society membership or use of specified Current Procedural Terminology codes. The main outcome was the percentage of physicians in each subspecialty prescribing opioids. RESULTS: The database included 19,762, 19,790, and 19,840 ophthalmologists in the years 2016, 2017, and 2018, respectively. Only the subspecialties of comprehensive ophthalmology (43.5% vs 39.6% vs 35.7%; p < 0.001; φc = 0.066), retina (66.5% vs 60.7% vs 54.5%; p < 0.001; φc = 0.101), cornea (82.8% vs 83.9% vs 77.2%; p = 0.03; φc = 0.076), and glaucoma (53.4% vs 46.4% vs 42.0%; p < 0.001; φc = 0.094) underwent a small but significant reduction in the proportion of physicians prescribing opioids. The subspecialties of oculoplastics (86%-88.8%), cornea (77.2%-82.8%), retina (54.5%-66.5%), and pediatrics (51.5%-57.9%) had the highest percentage of physicians prescribing opioids. The subspecialties of glaucoma, uveitis, and comprehensive ophthalmology had the lowest percentage of opioid prescribers. Among physicians with more than 10 opioid claims, median opioid claims did not change drastically. Opioids contributed only a small proportion of medication claims for all subspecialties. CONCLUSION: All subspecialties experienced either a small reduction or no significant change in the percentage of opioid prescribers during the period analyzed. We hope to encourage collaboration between ophthalmology subspecialties in striving to reduce opioid prescribing. Further studies are needed to better fine-tune opioid prescribing practices.

Anxiety as a Risk Factor for Postoperative Delirium in Elective Spine Deformity Surgeries: A National Database Study.

Introduction Generalized anxiety disorder has become one of the most prevalent mental health disorders in the United States. In addition, postoperative delirium has been shown to increase hospital stay, increase mortality, and increased healthcare costs. Few studies have looked at the prevalence of postoperative delirium in patients diagnosed with anxiety undergoing elective spinal deformity procedures. The purpose of this study was to determine if anxiety is a risk factor for postoperative delirium in elective spinal deformity surgeries. Methods The authors performed a retrospective analysis using the TriNetX Research Database. Patients diagnosed with kyphosis or lordosis who then underwent elective spinal correction surgeries were identified. This group was then separated based on the diagnosis of a generalized anxiety disorder before the operation versus no diagnosis. Propensity score adjustment, based on mental disorders and other risk factors, was then used to match cohorts on baseline demographics and characteristics. Analysis was performed on the primary outcome of postoperative delirium, with secondary outcomes of upper respiratory tract infections, surgical site infections, sepsis, ventilator dependence, convulsions, stroke, emergency department visits, myocardial infarction, pulmonary embolism, and urinary retention within 30 days after surgery. Results Our search included 1,211 patients with a diagnosis of anxiety and 8,055 patients without anxiety. After propensity score matching, 996 patients remained in each cohort. Statistical analysis showed significant outcomes between the matched cohorts in the anxiety group for postoperative delirium (OR 2.788; 1.587-4.899) and convulsions (OR 1.615; 1.006-2.592). All other outcomes were not significant after propensity score matching. Conclusion These results showed generalized anxiety disorder is a risk factor for postoperative delirium and convulsions after elective spine surgery. Further research is necessary on the effects of mental health disorders on postoperative delirium and other outcomes to better understand the risks in this population.

Obesity Paradox and Surgical Evacuation for Chronic Subdural Hematoma.

BACKGROUND:  Chronic subdural hematoma (cSDH) has a number of risk factors for recurrence, and some studies suggest obesity is one of them. Yet obesity has been shown to have a positive survival benefit in many diseases such as ischemic stroke, chronic obstructive pulmonary disease, percutaneous coronary intervention, and mechanical thrombectomy. Therefore, we sought to determine if obesity provided a mortality benefit in patients with cSDH undergoing burr hole drainage or craniotomy. METHODS:  We performed a retrospective database analysis using a multi-institutional (TriNetX) database looking at obese versus non-obese patients with cSDH undergoing surgical drainage. Our primary endpoint was mortality. Secondary endpoints included seizure, pulmonary embolism (PE), myocardial infarction (MI), cerebral infarction, deep vein thrombosis (DVT), tracheostomy, and percutaneous endoscopic gastrostomy (PEG). These were looked at to obtain a better idea of prognosis. Cohorts were propensity score-matched for confounders, using the greedy-nearest neighbor algorithm with a caliper of 0.1 pooled standard deviations. Kaplan-Meier survival curves were also developed, and hazard ratios were calculated. Chi-square analysis was performed on categorical variables. RESULTS:  A total of 1,849 patients were identified as obese with a drainage procedure, while 12,371 were identified as non-obese. Some 1,746 patients remained in each group after propensity score matching. Thirty-day survival rates were 88.08% in the obese vs. 83.82% in the non-obese cohorts, 90-day survival 85.15% vs. 79.35%, 365-day survival at 80.89% vs. 71.90%, and five-year survival at 64.75% vs. 54.84% (p < 0.0001). The risk difference was -8.02% (95% confidence interval, Cl -11.02, -5.021%); relative risk, RR 0.757, 95% Cl (0.67, 0.841); odds ratio, OR 0.676 (0.583, 0.783); p < 0.0001). Seizures, ventilator dependence, MI, cerebral infarction, tracheostomy, and PEG rates were all non-significant. Obese patients had a higher rate of PE (7.90% vs. 4.47%, p < 0.0001) and DVTs (12.37% vs. 10.02%, p = 0.0278). CONCLUSIONS:  Obesity in patients with cSDH undergoing surgical evacuation is associated with decreased mortality but higher rates of DVT and PE.

Mortality Rate of Ischemic Stroke Patients Undergoing Decompressive Hemicraniectomy With Obesity.

Background Obesity has been shown to have a positive mortality benefit in patients undergoing percutaneous coronary intervention and dialysis and those with rheumatoid arthritis, chronic obstructive pulmonary disease, and various wasting diseases. Studies for this mortality benefit in ischemic stroke patients are conflicting and have not been well studied in hemicraniectomy patients. We sought to determine the impact of obesity on outcomes of hemicraniectomy patients. Methods We performed a retrospective case-control database analysis using a multi-institutional database (TriNetX) looking at obese versus non-obese patients with ischemic stroke undergoing hemicraniectomy. Our primary endpoint was mortality. Secondary endpoints included seizure, pulmonary embolism, myocardial infarction (MI), cerebral infarction, deep vein thrombosis, tracheostomy, and percutaneous endoscopic gastrostomy. Cohorts were propensity-score matched for confounders. Results After propensity score matching for basic demographics and common comorbidities, as well as indicators of stroke severity, 646 patients were identified that were obese and had an ischemic stroke with subsequent hemicraniectomy (cohort 1), and 646 patients were identified who were non-obese with ischemic stroke and hemicraniectomy (cohort 2). Thirty-day survival rate was 98.142% in the obese vs. 87.771% in the non-obese cohorts, 90-day survival was 85.15% vs. 79.35%, 180-day survival was 96.44% vs. 84.52%, 365-day survival was 94.272% vs. 81.734%, and five-year survival was 81.889% vs. 75.077%, respectively. At five years, risk difference was -7.276% (95% CI: -11.757, -2.794) and odds ratio was 0.666 (95% CI: 0.510, 0.871) (p = 0.0029). Despite a higher mortality rate, obese patients had a statistically significant increase in pulmonary embolism (11.61% vs. 5.108, p < 0.0001), deep venous thrombosis (16.873% vs. 9.133%, p < 0.0001), and MI (8.824% vs. 5.882%, p = 0.0428). There was no significant difference in intensive care unit length of stay, ventilator dependence, tracheostomy placement, percutaneous endoscopic gastrostomy placement, or intracerebral hemorrhage. Conclusions Despite the increased risk of ischemic stroke, obese patients who undergo hemicraniectomy have decreased mortality rates compared to their non-obese counterparts.

The effect of prescribing antibiotics with opioids on the development of opioid use disorder: a national database study.

The goal of this study was to examine the impact of inpatient- or emergency department- prescribed antibiotic treatment in combination with opioids on the risk of developing opioid use disorder 12 months following discharge from the hospital. The authors conducted a propensity score-matched cohort study with data from the TriNetX Research Network database to identify adult subjects (18-65 years old) with no previous history of an opioid use disorder. Three cohorts were defined for the analyses: subjects who were prescribed an opioid, opioid in combination with an antibiotic, or an antibiotic while in the emergency department or inpatient unit, from the years 2012 to 2018. The diagnosis of an Opioid Related Disorder (F11.10-F11.20) 12 months following discharge from the emergency department or inpatient unit was then observed within the cohorts following the index event as identified by the ICD-10 procedural coding system. Primary analysis (propensity-score matched on age and sex) showed that opioids prescribed in combination with antibiotics had a protective effect against the development of opioid use disorder. This effect was consistent throughout all of the years included in this study with the smallest protective effect observed in 2018 (2012 risk ratio = 1.27 (95% CI: 1.23, 1.32); 2018 risk ratio: 1.03 (95% CI: 1.01, 1.05). These findings suggest that opioids prescribed in combination with antibiotics in the hospital setting are protective against the development of OUD at later time points following hospital discharge.

Exploring Microbiome Functional Dynamics through Space and Time with Trait-Based Theory.

Microbiomes play essential roles in the health and function of animal and plant hosts and drive nutrient cycling across ecosystems. Integrating novel trait-based approaches with ecological theory can facilitate the prediction of microbial functional traits important for ecosystem functioning and health. In particular, the yield-acquisition-stress (Y-A-S) framework considers dominant microbial life history strategies across gradients of resource availability and stress. However, microbiomes are dynamic, and spatial and temporal shifts in taxonomic and trait composition can affect ecosystem functions. We posit that extending the Y-A-S framework to microbiomes during succession and across biogeographic gradients can lead to generalizable rules for how microbiomes and their functions respond to resources and stress across space, time, and diverse ecosystems. We demonstrate the potential of this framework by applying it to the microbiomes hosted by the carnivorous pitcher plant Sarracenia purpurea, which have clear successional trajectories and are distributed across a broad climatic gradient.

Environment-host-microbial interactions shape the Sarracenia purpurea microbiome at the continental scale.

The importance of climate, habitat structure, and higher trophic levels on microbial diversity is only beginning to be understood. Here, we examined the influence of climate variables, plant morphology, and the abundance of aquatic invertebrates on the microbial biodiversity of the northern pitcher plant Sarracenia purpurea. The plant's cup-shaped leaves fill with rainwater and support a miniature, yet full-fledged, ecosystem with a diverse microbiome that decomposes captured prey and a small network of shredding and filter-feeding aquatic invertebrates that feed on microbes. We characterized pitcher microbiomes of 108 plants sampled at 36 sites from Florida to Quebec. Structural equation models revealed that annual precipitation and temperature, plant size, and midge abundance had direct effects on microbiome taxonomic and phylogenetic diversity. Climate variables also exerted indirect effects through plant size and midge abundance. Further, spatial structure and climate influenced taxonomic composition, but not phylogenetic composition. Our results suggest that direct effects of midge abundance and climate and indirect effects of climate through its effect on plant-associated factors lead to greater richness of microbial phylotypes in warmer, wetter sites.

Land use intensification destabilizes stream microbial biodiversity and decreases metabolic efficiency.

Urbanization and agricultural intensification can transform landscapes. Changes in land-use can lead to increases in storm runoff and nutrient loadings which can impair the health and function of stream ecosystems. Microorganisms are an integral component of stream ecosystems. Due to the sensitivity of microorganisms to perturbations, changes in hydrology and water chemistry may alter microbial activity and structure. These shifts in microbial community dynamics may alter stream metabolism and water quality, potentially impacting higher trophic levels. Here we examine the effects of land-use and associated changes in water chemistry on sediment microbial communities by studying the West Run Watershed (WRW) a mixed-land-use system in West Virginia, USA. Streams were sampled throughout the growing season at six sites within the WRW spanning different levels of land use intensification. The proportion of land impacted by agricultural and urban development was positively correlated with temporal variation in stream sediment microbial community composition (adj R2 = 0.65), suggesting development can destabilize microbial communities. Moreover, streams in developed watersheds had an increased metabolic quotient (20-50% higher), this indicates that microorganisms have greater respiration per unit biomass and signifies reduced metabolic efficiency. Further, our results suggest that land use associated changes in water chemistry alter microbial function both directly and indirectly via changes in microbial community composition and biomass. Taken together our results suggest that highly developed watersheds with elevated conductivity, metal ion concentration, and pH impose stress on microbial communities resulting in reduced microbial efficiency and elevated respiration.

Differences in microbial community response to nitrogen fertilization result in unique enzyme shifts between arbuscular and ectomycorrhizal-dominated soils.

While the effect of nitrogen (N) deposition on belowground carbon (C) cycling varies, emerging evidence shows that forest soils dominated by trees that associate with ectomycorrhizal fungi (ECM) store more C than soils dominated by trees that associate with arbuscular mycorrhizae (AM) with increasing N deposition. We hypothesized that this is due to unique nutrient cycling responses to N between AM and ECM-dominated soils. ECM trees primarily obtain N through fungal mining of soil organic matter subsidized by root-C. As such, we expected the largest N-induced responses of C and N cycling to occur in ECM rhizospheres and be driven by fungi. Conversely, as AM trees rely on bacterial scavengers in bulk soils to cycle N, we predicted the largest AM responses to be driven by shifts in bacteria and occur in bulk soils. To test this hypothesis, we measured microbial community composition, metatranscriptome profiles, and extracellular enzyme activity in bulk, rhizosphere, and organic horizon (OH) soils in AM and ECM-dominated soils at Bear Brook Watershed in Maine, USA. After 27 years of N fertilization, fungal community composition shifted across ECM soils, but bacterial communities shifted across AM soils. These shifts were mirrored by enhanced C relative to N mining enzyme activities in both mycorrhizal types, but this occurred in different soil fractions. In ECM stands these shifts occurred in rhizosphere soils, but in AM stands they occurred in bulk soils. Additionally, ECM OH soils exhibited the opposite response with declines in C relative to N mining. As rhizosphere soils account for only a small portion of total soil volume relative to bulk soils, coupled with declines in C to N enzyme activity in ECM OH soils, we posit that this may partly explain why ECM soils store more C than AM soils as N inputs increase.

Stream sediment bacterial communities exhibit temporally-consistent and distinct thresholds to land use change in a mixed-use watershed.

Freshwater ecosystems are susceptible to biodiversity losses due to land conversion. This is particularly true for the conversion of land from forests for agriculture and urban development. Freshwater sediments harbor microorganisms that provide vital ecosystem services. In dynamic habitats like freshwater sediments, microbial communities can be shaped by many processes, although the relative contributions of environmental factors to microbial community dynamics remain unclear. Given the future projected increase in land use change, it is important to ascertain how associated changes in stream physico-chemistry will influence sediment microbiomes. Here, we characterized stream chemistry and sediment bacterial community composition along a mixed land-use gradient in West Virginia, USA across one growing season. Sediment bacterial community richness was unaffected by increasing anthropogenic land use, though microbial communities were compositionally distinct across sites. Community threshold analysis revealed greater community resilience to agricultural land use than urban land use. Further, predicted metagenomes suggest differences in potential microbial function across changes in land use. The results of this study suggest that low levels of urban land use change can alter sediment bacterial community composition and predicted functional capacity in a mixed-use watershed, which could impact stream ecosystem services in the face of global land use change.