Grazing exclusion-induced changes in soil fungal communities in a highly desertified Brazilian dryland.

Soil desertification poses a critical ecological challenge in arid and semiarid climates worldwide, leading to decreased soil productivity due to the disruption of essential microbial community processes. Fungi, as one of the most important soil microbial communities, play a crucial role in enhancing nutrient and water uptake by plants through mycorrhizal associations. However, the impact of overgrazing-induced desertification on fungal community structure, particularly in the Caatinga biome of semiarid regions, remains unclear. In this study, we assessed the changes in both the total fungal community and the arbuscular mycorrhizal fungal community (AMF) across 1. Natural vegetation (native), 2. Grazing exclusion (20 years) (restored), and 3. affected by overgrazing-induced degradation (degraded) scenarios. Our assessment, conducted during both the dry and rainy seasons in Irauçuba, Ceará, utilized Internal Transcribed Spacer (ITS) gene sequencing via Illumina® platform. Our findings highlighted the significant roles of the AMF families Glomeraceae (∼71% of the total sequences) and Acaulosporaceae (∼14% of the total sequences) as potential key taxa in mitigating climate change within dryland areas. Moreover, we identified the orders Pleosporales (∼35% of the total sequences) and Capnodiales (∼21% of the total sequences) as the most abundant soil fungal communities in the Caatinga biome. The structure of the total fungal community differed when comparing native and restored areas to degraded areas. Total fungal communities from native and restored areas clustered together, suggesting that grazing exclusion has the potential to improve soil properties and recover fungal community structure amid global climate change challenges.

Molecular and Dual-Isotopic Profiling of the Microbial Controls on Nitrogen Leaching in Agricultural Soils under Managed Aquifer Recharge.

Nitrate (NO3-) leaching is a serious health and ecological concern in global agroecosystems, particularly those under the application of agricultural-managed aquifer recharge (Ag-MAR); however, there is an absence of information on microbial controls affecting NO3- leaching outcomes. We combine natural dual isotopes of NO3- (15N/14N and 18O/16O) with metagenomics, quantitative polymerase chain reaction (PCR), and a threshold indicator taxa analysis (TITAN) to investigate the activities, taxon profiles, and environmental controls of soil microbiome associated with NO3- leaching at different depths from Californian vineyards under Ag-MAR application. The isotopic signatures demonstrated a significant priming effect (P < 0.01) of Ag-MAR on denitrification activities in the topsoil (0-10 cm), with a 12-25-fold increase of 15N-NO3- and 18O-NO3- after the first 24 h of flooding, followed by a sharp decrease in the enrichment of both isotopes with ∼80% decline in denitrification activities thereafter. In contrast, deeper soils (60-100 cm) showed minimal or no denitrification activities over the course of Ag-MAR application, thus resulting in 10-20-fold of residual NO3- being leached. Metagenomic profiling and laboratory microcosm demonstrated that both nitrifying and denitrifying groups, responsible for controlling NO3- leaching, decreased in abundance and potential activity rates with soil depth. TITAN suggested that Nitrosocosmicus and Bradyrhizobium, as the major nitrifier and denitrifier, had the highest and lowest tipping points with regard to the NO3- changes (P < 0.05), respectively. Overall, our study provides new insight into specific depth limitations of microbial controls on soil NO3- leaching in agroecosystems.

The circadian clock and darkness control natural competence in cyanobacteria.

The cyanobacterium Synechococcus elongatus is a model organism for the study of circadian rhythms. It is naturally competent for transformation-that is, it takes up DNA from the environment, but the underlying mechanisms are unclear. Here, we use a genome-wide screen to identify genes required for natural transformation in S. elongatus, including genes encoding a conserved Type IV pilus, genes known to be associated with competence in other bacteria, and others. Pilus biogenesis occurs daily in the morning, while natural transformation is maximal when the onset of darkness coincides with the dusk circadian peak. Thus, the competence state in cyanobacteria is regulated by the circadian clock and can adapt to seasonal changes of day length.

Evaluation of Intravenous Ranitidine on Gastric pH in Critically Ill Pediatric Patients.

OBJECTIVE: To determine the dosing regimen of intravenous ranitidine (IVR) most likely to achieve a gastric pH of ≥4 in critically ill pediatric patients. METHODS: A retrospective cohort study was designed and included patients younger than 19 years with gastric pH samples taken from a nasogastric tube within 24 hours after a dose of IVR in an intensive care unit. Data collection included patient demographics, clinical variables, IVR dosing, and gastric pH samples. Descriptive statistical analysis and multivariable logistic regression analysis with clustering of patients was performed to determine variables associated with odds of obtaining a pH of ≥4. RESULTS: A total of 628 patients (1356 nasogastric samples) met study criteria (median age 1.3 years [IQR, 0.33, 5.7 years]; 53% male). The IVR dose was 0.90 ± 0.30 mg/kg per dose every 8.1 ± 2.9 hours, and 60.9% of patients (n = 383) had a pH ≥4. Patients with a pH value ≥4 had gastric pH samples taken earlier after a dose of IVR (6.7 ± 5.0 vs. 5.9 ± 4.7 hours, p < 0.001) but had no difference in IVR dose per kilogram (0.88 ± 0.31 vs. 0.88 ± 0.26, p = 0.86) or frequency of dosing (7.9 ± 3.2 vs. 7.9 ± 3.2 hours, p = 0.89). A multivariable logistic regression model identified increasing age, decreased kidney function, and decreased time to pH sample after an IVR dose with significantly greater odds of pH ≥4. CONCLUSIONS: The IVR dosing to maintain a gastric pH ≥4 in critically ill pediatric patients should occur more frequently than every 8 hours. Gastric pH evaluation may be necessary to assess IVR efficacy.

Effect of Intravenous Phenobarbital on Left Ventricular Myocardial Contractility Determined by Echocardiography in Children.

INTRODUCTION: Animal studies and rare human studies have suggested a negative effect of barbiturates on cardiac function. Although intravenous (IV) phenobarbital is used routinely in children in the clinical setting, studies in children are lacking. We performed a study to evaluate effect of IV phenobarbital loading on myocardial systolic function of children. METHODS: In a prospective pilot study in children without congenital heart defects, the effect of IV phenobarbital was evaluated on the left ventricular systolic function measured by ejection fraction (EF) by Simpson's method via an echocardiogram. Any child less than 18 years of age who received IV loading dose of at least 20 mg/kg of phenobarbital given as an infusion over 20 - 30 minutes for various medical indications was eligible to take part in the study. Three measurements of EF by an echocardiogram were made: before loading dose, 30 minutes after completion of the loading dose, and prior to the first maintenance dose. Relevant clinical data were recorded, including vital signs, immediately prior to each echocardiogram. Change of function as measured by EF over time was analyzed using linear mixed modeling methods. For this study, significant change in blood pressure was defined as a drop of at least 20 mmHg in systolic blood pressure. RESULTS: Ten children (70% female, age range two days to 8.2 years) were enrolled. Three had hypotension with a drop of systolic blood pressure greater than 20 mmHg from baseline. On examining the trajectory of EF on each individual graphically, the left ventricular EF tended to fall immediately following phenobarbital therapy and return to baseline on re-evaluation. These trajectories were statistically significant for EF. CONCLUSIONS: Phenobarbital had a direct and transient depressant effect on systolic function of the myocardium in one third of the cases. The depression in EF appeared to be transient with return to baseline in less than 24 hours. We recommend close monitoring with anticipation of decreased function in children when using IV phenobarbital.

Thrombotic microangiopathy associated with Valproic acid toxicity.

BACKGROUND: Thrombotic microangiopathy (TMA) is a serious, sometimes life-threatening disorder marked by the presence of endothelial injury and microvascular thrombi. Drug-induced thrombotic microangiopathy (DI-TMA) is one specific TMA syndrome that occurs following drug exposure via drug-dependent antibodies or direct tissue toxicity. Common examples include calcineurin inhibitors Tacrolimus and Cyclosporine and antineoplastics Gemcitabine and Mitomycin. Valproic acid has not been implicated in DI-TMA. We present the first case of a patient meeting clinical criteria for DI-TMA following admission for valproic acid toxicity. CASE PRESENTATION: An adolescent male with difficult to control epilepsy was admitted for impaired hepatic function while on valproic acid therapy. On the third hospital day, he developed severe metabolic lactic acidosis and multiorgan failure, prompting transfer to the pediatric intensive care unit. Progressive anemia and thrombocytopenia instigated an evaluation for thrombotic microangiopathy, where confirmed by concomitant hemolysis, elevated lactate dehydrogenase (LDH), low haptoglobin, and concurrent oliguric acute kidney injury. Thrombotic thrombocytopenic purpura was less likely with adequate ADAMTS13. Discontinuing valproic acid reversed the anemia, thrombocytopenia, and normalized the LDH and haptoglobin, supporting a drug-induced cause for the TMA. CONCLUSION: To the best of our knowledge, this is the first report of drug-induced TMA from valproic acid toxicity.