CCR5 drives NK cell-associated airway damage in pulmonary ischemia-reperfusion injury.

Primary graft dysfunction (PGD) limits clinical benefit after lung transplantation, a life-prolonging therapy for patients with end-stage disease. PGD is the clinical syndrome resulting from pulmonary ischemia-reperfusion injury (IRI), driven by innate immune inflammation. We recently demonstrated a key role for NK cells in the airways of mouse models and human tissue samples of IRI. Here, we used 2 mouse models paired with human lung transplant samples to investigate the mechanisms whereby NK cells migrate to the airways to mediate lung injury. We demonstrate that chemokine receptor ligand transcripts and proteins are increased in mouse and human disease. CCR5 ligand transcripts were correlated with NK cell gene signatures independently of NK cell CCR5 ligand secretion. NK cells expressing CCR5 were increased in the lung and airways during IRI and had increased markers of tissue residency and maturation. Allosteric CCR5 drug blockade reduced the migration of NK cells to the site of injury. CCR5 blockade also blunted quantitative measures of experimental IRI. Additionally, in human lung transplant bronchoalveolar lavage samples, we found that CCR5 ligand was associated with increased patient morbidity and that the CCR5 receptor was increased in expression on human NK cells following PGD. These data support a potential mechanism for NK cell migration during lung injury and identify a plausible preventative treatment for PGD.

Soil arthropod community responses to restoration in areas impacted by iron mining tailings deposition after Fundão dam failure.

In 2015, the failure of the Fundão dam in Mariana, Brazil released ~43 million m3 of iron mining tailings into the environment. Despite restoration initiatives in the following years, few studies-and most focused on revegetation-have evaluated the effectiveness of the restoration process in areas impacted by the disaster. We aimed to evaluate the responses of the arthropod community in areas impacted by iron mining tailings deposition from the Fundão dam that is in the restoration process. We defined sampling units in the riparian zone of the Gualaxo do Norte River, which is under restoration, and in a native not impacted riparian zone. We collected soil arthropods using pitfall traps and sampled environmental variables in the same sites. We used generalize least squares models (GLS) to test if the restored areas already presented values of arthropod diversity and functional group abundance similar to the reference area and to test which environmental variables are influencing arthropod diversity. We also tested how large the differences of arthropod community composition between the study areas and used the index of indicator species (IndVal) to verify which species could be used as an indicator of reference or restoration areas. The diversity of arthropods and the functional groups of detritivores and omnivores were higher in the native riparian zone. Understory density, soil density, organic matter content, and microbial biomass carbon were the environmental variables that significantly explained the diversity and species composition of arthropods. We show that restoration areas still have different soil arthropod diversity values and community composition when compared to reference areas. Evaluating the response of the arthropod community to the restoration process and long-term monitoring are essential to achieve a satisfactory result in this process and achieve a self-sustaining ecosystem.

Management of primary graft dysfunction after lung transplantation with extracorporeal life support: an evidence-based review.

Primary graft dysfunction (PGD) is a complex inflammatory syndrome that can lead to respiratory failure after lung transplantation (LTx). The pathogenesis of PGD is multifactorial and can be driven by attributes of both the donor and recipient, perioperative characteristics, and technical handling of the graft. Despite significant advancements in patient and donor selection, perioperative management and surgical technique, PGD is still a major contributor to morbidity and mortality after lung transplant. Although there are no known durable treatment options for PGD after LTx, an increasing body of evidence and experience in high-volume lung transplant centers show that extracorporeal life support (ECLS) is a reliable option for both preventing PGD and supporting critically ill patients with PGD. Both veno-venous (V-V) ECLS and veno-arterial (V-A) ECLS are proven and feasible strategies for mitigating the morbidity and mortality associated with post-LTx PGD. In this evidence-based review, we provide an overview of the epidemiology and physiology of PGD as well as a growing body of data that supports ECLS as a major tool to manage PGD. We describe the role of ECMO in PGD prevention and management, worldwide outcomes of LTx with ECLS support, and outline our step-wise approach to managing this complex respiratory syndrome leading up to institution of ECLS.

Decreased Lymphocytic Bronchitis Severity in the Era of Azithromycin Prophylaxis.

Large-airway lymphocytic inflammation (LB), assessed on endobronchial biopsies, has been associated with acute cellular rejection and chronic lung allograft dysfunction (CLAD). Azithromycin (AZI) prophylaxis has been used to prevent airway inflammation and subsequent CLAD, with inconsistent results. We hypothesized that AZI prophylaxis would be associated with reduced LB, changes in bronchoalveolar lavage (BAL) immune cell populations, and improved CLAD-free survival. Methods: We compared frequencies of LB from endobronchial biopsies before (N = 1856) and after (N = 975) protocolized initiation of AZI prophylaxis at our center. LB was classified as none, minimal, mild, or moderate by histopathologic analysis. LB grades were compared using ordinal mixed-model regression. Corresponding automated BAL leukocyte frequencies were compared using mixed-effects modeling. The effect of AZI prophylaxis on CLAD-free survival was assessed by a Cox proportional hazards model adjusted for age, sex, ethnicity, transplant indication, and cytomegalovirus serostatus. Results: Biopsies in the pre-AZI era had 2-fold increased odds (95% confidence interval, 1.5-2.7; P < 0.001) of higher LB grades. LB was associated with BAL neutrophilia in both eras. However, there was no difference in risk for CLAD or death between AZI eras (hazard ratio 1.3; 95% confidence interval, 0.7-2.0; P = 0.45). Conclusions: Decreased airway inflammation in the era of AZI prophylaxis may represent a direct effect of AZI therapy or reflect other practices or environmental changes. In this cohort, AZI prophylaxis was not associated with improved CLAD-free survival.

Detailed characterization of iron-rich tailings after the Fundão dam failure, Brazil, with inclusion of proximal sensors data, as a secure basis for environmental and agricultural restoration.

Following the Fundão dam failure in Brazil, 60 million m3 of iron-rich tailings were released impacting an extensive area. After this catastrophe, a detailed characterization and monitoring of iron-rich tailings is required for agronomic and environmental purposes. This can be facilitated by using proximal sensors which have been an efficient, fast, and cost-effective tool for eco-friendly analysis of soils and sediments. This work hypothesized that portable X-ray fluorescence (pXRF) spectrometry combined with a pocket-sized (Nix™ Pro) color sensor and benchtop magnetic susceptibilimeter can produce substantial data for fast and clean characterization of iron-rich tailings. The objectives were to differentiate impacted and non-impacted areas (soils and sediments) based on proximal sensors data, and to predict attributes of agronomic and environmental importance. A total of 148 composite samples were collected on totally impacted, partially impacted, and non-impacted areas (natural soils). The samples were analyzed via pXRF to obtain the total elemental composition; via Nix™ Pro color sensor to obtain the red (R), green (G), and blue (B) parameters; and assessed for magnetic susceptibility (MS). The same samples used for analyses via the aforementioned sensors were wet-digested (USEPA 3051a method) followed by ICP-OES quantification of potentially toxic elements. Principal component analysis was performed to differentiate impacted and non-impacted areas. The pXRF data alone or combined with other sensors were used to predict soil agronomic properties and semi-total concentration of potentially toxic elements via random forest regression. For that, samples were randomly separated into modeling (70%) and validation (30%) datasets. The pXRF proved to be an efficient method for rapid and eco-friendly characterization of iron-rich tailings, allowing a clear differentiation of impacted and non-impacted areas. Also, important soil agronomic properties (clay, cation exchange capacity, soil organic carbon, pH and macronutrients availability) and semi-total concentrations of Ba, Pb, Cr, V, Cu, Co, Ni, Mn, Ti, and Li were accurately predicted (based upon the lowest RMSE and highest R2 and RPD values). Sensor data fusion (pXRF + Nix Pro + MS) slightly improved the accuracy of predictions. This work highlights iron-rich tailings from the Fundão dam failure can be in detail characterized via pXRF ex situ, providing a secure basis for complementary studies in situ aiming at identify contaminated hot spots, digital mapping of soil and properties variability, and embasing pedological, agricultural and environmental purposes.

Intercostal Nerve Cryoanalgesia Versus Thoracic Epidural Analgesia in Lung Transplantation: A Retrospective Single-Center Study.

INTRODUCTION: The optimal pain management strategy after lung transplantation is unknown. This study compared analgesic outcomes of intercostal nerve blockade by cryoanalgesia (Cryo) versus thoracic epidural analgesia (TEA). METHODS: Seventy-two patients who underwent bilateral lung transplantation via clamshell incision at our center from 2016 to 2018 were managed with TEA (N = 43) or Cryo (N = 29). We evaluated analgesic-specific complications, opioid use in oral morphine equivalents (OME), and pain scores (0-10) through postoperative day 7. Adjusted linear regression was used to assess for non-inferiority of Cryo to TEA. RESULTS: The overall mean pain scores (Cryo 3.2 vs TEA 3.8, P = 0.21), maximum mean pain scores (Cryo 4.7 vs TEA 5.5, P = 0.16), and the total opioid use (Cryo 484 vs TEA 705 OME, P = 0.12) were similar in both groups, while the utilization of postoperative opioid-sparing analgesia, measured as use of lidocaine patches, was lower in the Cryo group (Cryo 21% vs TEA 84%, P < 0.001). Analgesic outcomes remained similar between the cohorts after adjustment for pertinent patient and analgesic characteristics (P = 0.26), as well as after exclusion of Cryo patients requiring rescue TEA (P = 0.32). There were no Cryo complications, with four patients requiring subsequent TEA for pain control. Two TEA patients experienced hemodynamic instability following a test TEA bolus requiring code measures. Additionally, TEA placement was delayed beyond postoperative day 1 in 33% owing to need for anticoagulation or clinical instability. CONCLUSIONS: In lung transplantation, Cryo was found to be safe with analgesic effectiveness similar to TEA. Cryo may be advantageous in this complex patient population, as it can be used in all clinical scenarios and eliminates risks and delays associated with TEA.

Outcomes of Anastomotic Evaluation Using Indocyanine Green Fluorescence during Minimally Invasive Esophagectomy.

BACKGROUND: Limited evidence exists assessing whether anastomotic evaluation using indocyanine green fluorescence (IGF) during minimally invasive esophagectomy (MIE) predicts or improves outcomes. We hypothesized that IGF helps surgeons predict anastomotic complications and reduces anastomotic leaks after MIE. METHODS: In September 2019, our institution began routinely using IGF for intraoperative evaluation of anastomoses during MIE. Data were collected from patients undergoing MIE in the two years before and after this technology began being routinely used. Baseline characteristics and outcomes, including anastomotic leak, in patients who underwent indocyanine green fluorescence evaluation (ICG) and those who did not (nICG) were compared. Outcomes were also compared between ICG patients with normal versus abnormal fluorescence. RESULTS: Overall, 181 patients were included. Baseline demographic and clinical characteristics did not differ between the ICG and nICG groups. ICG patients experienced higher rates of anastomotic leak (10.2% vs. 1.6%, P = .015) and 90-day mortality (8.5% vs. 1.6%, P = .04) compared to nICG patients. Due to lack of equipment availability, 19 nICG patients underwent MIE after the use of IGF became routine, and none developed leaks. ICG patients with abnormal fluorescence had higher rates of anastomotic leak (71.4% vs 1.9%, P < .001) and 30-day mortality (28.6% vs 0%, P = .012) compared to those with normal fluorescence. DISCUSSION: Abnormal intraoperative IGF was associated with increased rate of anastomotic leak, suggesting predictive potential of IGF. However, its use was associated with an increased leak rate and higher mortality. Further studies are warranted to assess possible physiologic effects of indocyanine green on the esophageal anastomosis.

Purple acid phosphatases in coffee-genome-wide identification and the transcriptional profile of selected members in roots upon Pi starvation.

Phosphorus (P) availability is determinant for crop productivity and, despite the sufficient amount of this nutrient in arable land, most of it remains insoluble, leading to the need of high fertilizer input. To cope with P scarcity forecasts and also for cropping costs alleviation, genotypes better adapted to promote P solubilization and absorption are required, especially for perennial crops. Coffee is one of these important perennial crops cultivated in soils with low P availability, and thus we aimed to study adaptive strategies to coffee genotypes in acquire phosphorus. In this study, we focused on rhizosphere phosphatase activity, a major characteristic related to P solubilization from organic pools. To explore the genetic basis of this characteristic, we firstly identified 29 Purple Acid Phosphatases (PAP) genes in C. canephora genome and selected five candidates with higher potential to encode secreted PAPs. We found that C. arabica genotypes have diverse profiles of rhizosphere phosphatase activity, as well as microbial biomass carbon, which we measured to explore the impact of the plant on microbiota and also to discriminate the phosphatase activity origin (plant or microorganism-derived). We selected two C. arabica cultivars with contrasting phosphatase activity and found that one PAP gene has a correlated gene expression profile with this characteristic. This work explores coffee adaptative responses to P starvation conditions, and the information provided can further contribute to breeding programs aiming better adapted genotypes for sustainable agriculture in face of current challenges. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-022-03399-6.

Lymphocytic Airway Inflammation in Lung Allografts.

Lung transplant remains a key therapeutic option for patients with end stage lung disease but short- and long-term survival lag other solid organ transplants. Early ischemia-reperfusion injury in the form of primary graft dysfunction (PGD) and acute cellular rejection are risk factors for chronic lung allograft dysfunction (CLAD), a syndrome of airway and parenchymal fibrosis that is the major barrier to long term survival. An increasing body of research suggests lymphocytic airway inflammation plays a significant role in these important clinical syndromes. Cytotoxic T cells are observed in airway rejection, and transcriptional analysis of airways reveal common cytotoxic gene patterns across solid organ transplant rejection. Natural killer (NK) cells have also been implicated in the early allograft damage response to PGD, acute rejection, cytomegalovirus, and CLAD. This review will examine the roles of lymphocytic airway inflammation across the lifespan of the allograft, including: 1) The contribution of innate lymphocytes to PGD and the impact of PGD on the adaptive immune response. 2) Acute cellular rejection pathologies and the limitations in identifying airway inflammation by transbronchial biopsy. 3) Potentiators of airway inflammation and heterologous immunity, such as respiratory infections, aspiration, and the airway microbiome. 4) Airway contributions to CLAD pathogenesis, including epithelial to mesenchymal transition (EMT), club cell loss, and the evolution from constrictive bronchiolitis to parenchymal fibrosis. 5) Protective mechanisms of fibrosis involving regulatory T cells. In summary, this review will examine our current understanding of the complex interplay between the transplanted airway epithelium, lymphocytic airway infiltration, and rejection pathologies.

The use of monoclonal antibody therapy in pediatric patients with COVID-19: a retrospective case series.

BACKGROUND: Monoclonal antibody (MCA) therapies have been utilized under emergency use authorization (EUA) for high-risk pediatric patients with mild to moderate coronavirus disease 2019 (COVID-19) in the outpatient setting since late 2019. The purpose of this study was to describe the use of MCA therapy in pediatric patients in the pediatric emergency department (ED) at a large community hospital. METHODS: This was a retrospective case series of high-risk pediatric patients 12 to 17 years of age who received MCA therapy in the pediatric ED between December 8, 2020 and June 3, 2021. The primary outcome was to describe the patient characteristics, clinical presentation, and safety profile of the pediatric population that received MCA therapy. The secondary outcome was to describe the incidence of hospitalizations or ED visits up to 28 days following therapy. RESULTS: A total of 44 patients were included in the analysis. The median number of days of symptoms was 4 with 41% of patients having symptoms between 0 and 3 days at time of MCA administration. Only one patient experienced a mild adverse event that did not require epinephrine administration. Two patients returned to the ED for reevaluation during the study follow-up period. No patients required admission within 28 days post-therapy. CONCLUSIONS: The administration of MCA therapy in high-risk pediatric patients in the pediatric ED was well-tolerated with subjective improvement noted in COVID-19 symptoms post-therapy. Further studies are necessary to determine the role MCA therapy may play in reducing morbidity from COVID-19 infection in high-risk pediatric patients.

Reduced opioid utilization and post-operative pain in Asian vs. Caucasian populations after video-assisted thoracoscopic surgery lobectomy with liposomal bupivacaine-based intercostal nerve blockade.

BACKGROUND: Regional analgesia, such as intercostal nerve blockade (INB), is a viable modality for postoperative pain control in thoracic surgery patients. Asian patients have historically been underrepresented in studies of pain responses and pain medication requirements based on race. In this study, we examined the postoperative opioid medications used by Asian and Caucasian patients undergoing video-assisted thoracoscopic surgery (VATS) lobectomy who received different bupivacaine-based INB. METHODS: We retrospectively reviewed patients undergoing VATS lobectomy who received standard bupivacaine (SB), liposomal bupivacaine (LB), or liposomal bupivacaine mixed with standard bupivacaine (MIX). Length of stay (LOS), postoperative pain scores, postoperative opioid use (in intravenous morphine equivalents) were evaluated. The Chi-square test was used to compare categorical variables; Student's t-test for normally distributed variables; and the Wilcoxon rank-sum test for non-normally distributed variables. Multivariable linear regression was used to assess opioid use in Asians compared to Caucasians. RESULTS: Of the 239 patients in the cohort, 212 received LB or MIX and 27 received SB. In the LB/MIX group, 48 (22.6%) were Asian and 164 (77.4%) were Caucasian. In the SB group, 7 (25.9%) were Asian and 20 (74.1%) were Caucasian. There were no differences in height, weight, and body mass index (BMI) between the SB and LB/MIX groups, but there was a significant difference in weight and BMI between Asian and Caucasian patients. The median LOS was comparable between the SB and LB/MIX groups. The average 24-hour postoperative pain score in the LB/MIX group was 2.5, and 2.0 and 2.7 in the Asian and Caucasian subgroups, respectively (P<0.01). The median opioid use in the LB/MIX group was 27.2 mg, and 16.9 and 31.1 mg in the Asian and Caucasian subgroups, respectively (P<0.01). On multivariable linear regression analysis adjusting for sex, age, BMI, and bupivacaine type, we found Asians used 25.5 mg less opioids compared to Caucasians (P<0.01). CONCLUSIONS: INB with LB or liposomal-standard bupivacaine mix resulted in statistically significant decreased postoperative pain scores and opioid use in Asians compared to Caucasians. There was no difference in LOS between the LB/MIX and SB groups.

Impact of the utilization of 500 mL IV bags on crystalloid resuscitation volumes administered to trauma patients.

INTRODUCTION: Administering large volumes of crystalloids to trauma patients has been shown to exacerbate metabolic complications of hemorrhage including dilutional coagulopathy and worsening acidosis The aim of this study was to evaluate crystalloid administration volumes in trauma patients after replacing 1 L IV containers with 500 mL IV containers in the emergency department trauma resuscitation bay. MATERIALS AND METHODS: This was a single-center, IRB-approved, retrospective cohort evaluation of adult trauma patients conducted at an 864-bed community tertiary referral center located in the southeastern United States. Patterns of crystalloid administration were examined before and after the trauma resuscitation bay began to exclusively stock 500 mL IV containers. The primary outcome was mean total crystalloid volume infused from time of injury to hospital admission. Secondary outcomes included mean total crystalloid volume infused prior to administration of blood products, proportion of patients who received less than 2 L total of crystalloids, time to initiation of blood products, and mortality in both the emergency department and in-hospital. RESULTS: Patient characteristics were largely similar between both groups including age, mechanism of injury, and Injury Severity Score. For the primary outcome, the mean total crystalloid volume infused from time of injury to hospital administration, patients in the 500 mL IV fluid container group were administered 555 mL less crystalloid when compared to the 1 L IV fluid container group, 1048 mL vs 1603 mL (p < 0.01; 95% CI 406 mL - 704 mL), respectively. After conversion to the 500 mL IV container bags, there was a 27.5% increase in the proportion of patients receiving less than 2 L of crystalloid, 90.5% vs 63.0% in the 500 mL IV fluid container and 1 L IV fluid container groups, respectively (p < 0.01). CONCLUSIONS: Due to reduced mortality, expanding literature and guidelines clearly support minimizing IV crystalloid resuscitation. Institutions must now work to minimize use of IV crystalloids to hemorrhaging trauma patients and a simple solution of using smaller IV fluid bags was shown to improve adherence to this practice.

Impact of early versus late administration of bamlanivimab on readmissions in patients with high-risk COVID-19.

BACKGROUND: Recombinant monoclonal antibody therapies have been utilized under emergency use authorization (EUA) for the prevention of clinical decompensation in high-risk COVID-19 positive patients for up to 10 days from symptom onset. The purpose of this study was to determine the impact of the timing of the monoclonal antibody, bamlanivimab, on clinical outcomes in high-risk COVID-19 positive patients. METHODS: This was an IRB-approved, retrospective evaluation of adult patients who received bamlanivimab per EUA criteria in the emergency department (ED). Patients were dichotomized into two groups- 3 days of symptoms or less (early) versus 4 to 10 days (late). The primary outcome was hospitalization for COVID-related illness at 28 days (or treatment failure). Secondary outcomes were COVID-related ED visits at 28 days, hospital and intensive care unit (ICU) length of stay (LOS), and in-hospital mortality at 28 days. RESULTS: A total of 839 patients were included in the analysis. There was no difference observed in COVID-related hospitalization rates within 28 days between the early and late bamlanivimab administration groups (7.5% vs. 8.2%, p = 0.71). There was no difference in COVID-related ED visits within 28 days with 13% of patients returning to the ED. CONCLUSIONS: In conclusion, there were no differences in the rates of hospitalization at 28 days when bamlanivimab was administered in the first 3 days of illness versus days 4 to 10. Future prospective studies are warranted to expand upon the characteristics of patients that may or may not benefit from monoclonal antibody therapy.

Chemical, physical, and biological attributes in soils affected by deposition of iron ore tailings from the Fundão Dam failure.

Monitoring degraded areas is essential for evaluation of the quality of the rehabilitation process. In this study, we evaluate how the physical and chemical characteristics of the mixture of iron ore tailings with the soil have affected the soil microbial biomass and activity in areas along the Gualaxo do Norte River after the Fundão Dam disaster. Composite soil samples were collected from areas that were impacted (I) and not impacted (NI) by the tailings. The following attributes were evaluated: chemical element content; soil density, porosity, and texture; microbial biomass carbon; basal respiration; and enzyme activity and density of microbial groups (bacteria, actinobacteria, fungi, arbuscular mycorrhizae, phosphate solubilizers, cellulolytic microorganisms, nitrifiers, ammonifiers, and diazotrophs). According to result, the deposition of tailings increased the pH and the soil available P, Cr, Fe, and Mn content and reduced organic matter. The physical and biological attributes were negatively affected, with increases in the silt content and density of the soil, and reduction in macroporosity and in the microbial biomass and activity of the soil (respiration and enzymes) in the impacted area. However, the impacted areas exhibited greater densities of some microbial groups (cellulolytic microorganisms, nitrifiers, and diazotrophic bacteria). Modifications in the organic matter and silt content are the main attributes associated with deposition of the tailings that affected soil microbial biomass and microbial activity. This may affect erosive conditions and the functionality of the ecosystem, indicating an imbalance in this environment. In contrast, the higher density of some microbial groups in the impacted areas show the high rehabilitation potential of these areas.

Formononetin accelerates mycorrhization and increases maize production at low phosphorus application rates.

The formononetin biostimulant may be an option for reducing P fertilization once it stimulates mycelial growth of arbuscular mycorrhizal fungi and increases plant ability to take up nutrients through the roots, especially phosphorus. The objective of this study was to evaluate the effect of formononetin associated with phosphorus fertilization in maize. Field experiments were conducted in a randomized block design with a 3 × 4 factorial arrangement (0, 50 or 70, and 140 kg ha-1 P2O5; and formononetin application rates: 0, 25, 50, and 100 g ha-1), with four replications. Formononetin (100 g ha-1) increased the mycorrhizal colonization rate up to 30% in maize in the first four weeks after emergence when no P fertilizer was applied, and to 17% when 50 or 70 kg ha-1 of P2O5 were applied. The application of 50 and 100 g ha-1 of formononetin significantly increased plant height, ear height, and grain yield (22% - 76%) when no P fertilizer was applied. The use of formononetin in the field stimulates mycorrhizal colonization, has a positive effect on maize yield, and reduces the need for P fertilizer application in maize. However, this effect was evident only at low P soil contents.

Environmental drivers of shifts on microbial traits in sites disturbed by a large-scale tailing dam collapse.

This study aimed to assess the most affected traits related to microbial ecophysiology and activity and investigate its relationships with environmental drivers in mine tailings spilled from the Fundão dam at disturbed sites across Gualaxo do Norte river, Minas Gerais, Brazil. The mine tailings are characterized by increased pH value, silt percentage, and bulk density, while clay percentage, organic carbon (Corg), total nitrogen (Nt), and moisture contents are reduced. Microbial biomass, enzymatic activities (arylsulfatase, ß-1,4-glucosidase, acid and alkaline phosphatases), and the total microbial activity potential (FDA hydrolysis) were generally lower in tailings compared to undisturbed reference soil (Und). Enzyme-based indexes (GMea, WMean, and IBRv2) showed microbial communities with significantly lower degradative efficacy in the tailings than Und in all sites (R2 ≥ 0.94, p < 0.001). Non-metric multidimensional scaling and distance-based redundancy analysis revealed that microbial communities exhibited significant differentiation (R2 adjusted = 0.73, p = 0.0001) between mine tailings and Und over the different studied sites, which was strongly influenced by changes on physicochemical properties (pH, Corg and Nt contents, the predominance of small-sized particles of silt, and bulk density) and the presence of Se, Cr, Fe, and Ni, even at low concentrations. Our study suggests that the physicochemical properties and the presence of low bioavailable concentrations of heavy metals in dam tailings promote shifts on microbial communities through reductions in the C storage and biogeochemical cycling of nutrients by these communities compared to those in undisturbed reference soils surrounding and, therefore, has negative implications for the ecosystem functioning.

Microbiological Indicators of Soil Quality Under Native Forests are Influenced by Topographic Factors.

Several microbiological indicators of soil quality present high sensitivity, but little is known about the influence of topographic factors on them. This work aimed to evaluate variability of biological indicators of soil quality across a hillslope under native forest and the influence of topographic factors on them. Four positions on a hillslope were evaluated. Activity of the enzymes ß-glucosidase, acid phosphatase, urease and fluorescein diacetate (FDA) hydrolysis were determined, as well as basal and substrate-induced respiration, and density of microorganisms: total bacteria, total fungi, actinobacteria, phosphate solubilizers, ammonifiers, native rhizobia, free-living N2-fixing bacteria, spores of arbuscular mycorrhizal fungi and percentage of root colonization by arbuscular mycorrhizal fungi. Activity and density of microorganisms were correlated with topographic factors. The relation of these factors to the variations of the evaluated indicators was determined using the random forest algorithm. Microbiological indicators varied according to the hillslope positions. The indicators urease, basal respiration, spore density, mycorrhizal colonization, total bacteria and fungi, phosphate solubilizers, and free-living N2-fixing bacteria detected in JNFB and FAM culture medium did not vary with terrain attributes and were therefore more indicated in cases of topographic variations. This and future studies can help to select the best microbiological indicators for different conditions.

Arbuscular Mycorrhizal Fungi Favor the Initial Growth of Acacia mangium, Sorghum bicolor, and Urochloa brizantha in Soil Contaminated with Zn, Cu, Pb, and Cd.

This study evaluated the effect of inoculation with a mixture of spores of arbuscular mycorrhizal fungi (AMF) (Glomus macrocarpum, Paraglomus occultum, and Glomus sp.) on the initial establishment of Acacia mangium, Sorghum bicolor, and Urochloa brizantha in soil contaminated with heavy metals. The experiment was conducted in a greenhouse, in plastic pots containing 1.8 kg of soil, which presented 7200, 1140, 480, and 72 mg of Zn, Cu, Pb, and Cd, respectively. The chlorophyll content (SPAD index) of inoculated plants of A. mangium and U. brizantha was higher than those of non-inoculated plants (p < 0.05). No differences were detected for the concentration of heavy metals in plant shoots, whether the plant was inoculated or not. However, inoculated plants had greater root length (S. bicolor and U. brizantha) (p < 0.05) and greater plant height (A. mangium) (p < 0.05). The present results demonstrate that the beneficial effects of AMF on plant growth and the alleviation of contaminants are imperative factors for the rehabilitation of soils contaminated with heavy metals.

Enrichment of arbuscular mycorrhizal fungi in a contaminated soil after rehabilitation

Abstract Spore counts, species composition and richness of arbuscular mycorrhizal fungi, and soil glomalin contents were evaluated in a soil contaminated with Zn, Cu, Cd and Pb after rehabilitation by partial replacement of the contaminated soil with non-contaminated soil, and by Eucalyptus camaldulensis planting with and without Brachiaria decumbens sowing. These rehabilitation procedures were compared with soils from contaminated non-rehabilitated area and non-contaminated adjacent soils. Arbuscular mycorrhizal fungi communities attributes were assessed by direct field sampling, trap culture technique, and by glomalin contents estimate. Arbuscular mycorrhizal fungi was markedly favored by rehabilitation, and a total of 15 arbuscular mycorrhizal fungi morphotypes were detected in the studied area. Species from the Glomus and Acaulospora genera were the most common mycorrhizal fungi. Number of spores was increased by as much as 300-fold, and species richness almost doubled in areas rehabilitated by planting Eucalyptus in rows and sowing B. decumbens in inter-rows. Contents of heavy metals in the soil were negatively correlated with both species richness and glomalin contents. Introduction of B. decumbens together with Eucalyptus causes enrichment of arbuscular mycorrhizal fungi species and a more balanced community of arbuscular mycorrhizal fungi spores in contaminated soil.

Enrichment of arbuscular mycorrhizal fungi in a contaminated soil after rehabilitation.

Spore counts, species composition and richness of arbuscular mycorrhizal fungi, and soil glomalin contents were evaluated in a soil contaminated with Zn, Cu, Cd and Pb after rehabilitation by partial replacement of the contaminated soil with non-contaminated soil, and by Eucalyptus camaldulensis planting with and without Brachiaria decumbens sowing. These rehabilitation procedures were compared with soils from contaminated non-rehabilitated area and non-contaminated adjacent soils. Arbuscular mycorrhizal fungi communities attributes were assessed by direct field sampling, trap culture technique, and by glomalin contents estimate. Arbuscular mycorrhizal fungi was markedly favored by rehabilitation, and a total of 15 arbuscular mycorrhizal fungi morphotypes were detected in the studied area. Species from the Glomus and Acaulospora genera were the most common mycorrhizal fungi. Number of spores was increased by as much as 300-fold, and species richness almost doubled in areas rehabilitated by planting Eucalyptus in rows and sowing B. decumbens in inter-rows. Contents of heavy metals in the soil were negatively correlated with both species richness and glomalin contents. Introduction of B. decumbens together with Eucalyptus causes enrichment of arbuscular mycorrhizal fungi species and a more balanced community of arbuscular mycorrhizal fungi spores in contaminated soil.