Sensitivity Of Microorganisms Research Articles

Suspensions of antibiotics in self-emulsifying oils as a novel approach to formulate eye drops with substances which undergo hydrolysis in aqueous environment

The aim of this study was to develop eye-drops with cefuroxime (CEF) sodium or vancomycin (VAN) hydrochloride, antibiotics that are instable in water. Anhydrous self-emulsifying oils (SEO) are proposed as a carrier and antibiotics are suspended. In the contact with tear fluid, the formulation should transform into emulsion, with fast dissolution of an antibiotic. CEF or VAN (5% w/w) was suspended in SEO carriers prepared by dissolving surfactants (Tween 20 or Span 80 5% w/w) in Miglyol, castor oil, or olive oil. Formulations with or without sodium citrate (2% w/w) were compared. Six-months or 1-year stability tests were carried out at 40 °C. The content of CEF and VAN was evaluated using HPLC and the potency of the antibiotic was assessed with agar diffusion method. In contact with water, drug particles suspended in SEO dissolved rapidly and o/w emulsion was formed. After 1-year at 40 °C, the content of degradation products was at most 0.5% in CEF and 4.0% in VAN formulations. The agar diffusion assay has shown that CEF and VAN loaded into SEO retained its potency against the sensitive microorganisms comparable to an aqueous solution. Therefore, SEO can be used as a novel carrier for the active substances which may not require improved solubility or absorption but need to be protected from moisture. This is a formulation that can be produced on industrial scale, with no limitation of stability or drug concentration.

The impact of pathogen sensitivity to antibiotics loaded in cement on the number of revisions and costs in the treatment of periprosthetic knee infection.

This study aims to evaluate the impact of the pathogen's sensitivity to the loaded antibiotics on infection resolution, the number of revisions, and the associated costs in patients undergoing revision total knee arthroplasty (rTKA) due to PJI. We reviewed the treatment and follow-up processes of 61 patients who underwent rTKA for late-stage PJI following primary total knee arthroplasty in our clinic. The study included 11 patients in the resistant group and 50 in the sensitive group in line with the power analysis results. Patients' demographic characteristics and comorbidities were recorded. All patients received dual antibiotic-loaded cement. Microbiological examinations of patients were analyzed, and the number of revision surgeries each patient underwent was determined. We analyzed all surgeries related to infection treatment, including open irrigation, debridement, polyethylene exchange, implant extractions, antibiotic-loaded cement spacer placements, spacer changes, and debridements, and the implantation of revision prostheses, including tumor prostheses. The total number of surgeries each patient underwent was recorded. We also reviewed hospital system records of total protocol costs during patient admissions. Of 61 patients undergoing revision total knee arthroplasty (rTKA) for periprosthetic joint infection, 11 had antibiotic-resistant infections and 50 had antibiotic-sensitive infections. The groups had similar demographics. Polymicrobial infections were more frequent in the resistant group (p = 0.017), with all resistant cases showing gentamicin resistance and two showing teicoplanin resistance. The resistant group required more surgeries (average 3.91 ± 2.7 vs. 2.34 ± 1.3, p = 0.043) compared to the sensitive group, with teicoplanin resistance doubling revision surgeries (p = 0.005). Costs were similar between groups, averaging $6536.96. Gram-negative infections led to more revisions (p = 0.013). Polymicrobial infections did not significantly affect the number of surgeries or costs compared to single strain infections. Our study demonstrates that in rTKA surgeries using dual antibiotic-loaded bone cement, infections caused by antibiotic-resistant microorganisms are more challenging and time-consuming to treat. This underscores the necessity of exploring new methods to enhance local efficacy by loading cement with antibiotics based on specific pathogen culture and sensitivity results, while also providing clinical evidence of the effectiveness of current treatment methods against sensitive microorganisms. Level 3 (a retrospective cohort study).

Antimicrobials in Orthopedic Infections: Overview of Clinical Perspective and Microbial Resistance.

Orthopedic infections are challenging pathologies that impose a heavy burden on patients and the healthcare system. Antimicrobial therapy is a critical component of the successful management of orthopedic infections, but its effectiveness depends on patient-, surgery-, drug-, and hospital-related factors. The dramatic increase in the emergence of multidrug-resistant microbial strains necessitates new clinical approaches in order to prevent or limit this phenomenon and to ensure a favorable therapeutic outcome. The present paper reviews the currently available antimicrobial strategies in the management of orthopedic infections, highlighting their clinical use related to the occurrence of microbial resistance. Some approaches for reducing antibiotic resistance emergence in orthopedics are also presented. The use of antibiotics tailored to the microorganism's sensitivity profile, patient factors, and pharmacokinetic profile in terms of monotherapy or combinations, the understanding of microbial pathogenicity and resistance patterns, strict control measures in healthcare facilities, the development of new antimicrobial therapies (drugs, devices, technologies), and patient education for improving compliance and tolerance are some of the most important tools for overcoming microbial resistance.

Differential impact of wildfire and rice straw ash on the skin microbiota of Rana dybowskii adults and tadpoles.

Global warming has intensified severe weather conditions and increased the frequency of wildfires, posing significant threats to ecosystems. Moreover, rice straw ash, a byproduct of human agricultural activities, represents an environmental stressor that can further impact these vulnerable ecosystems. These changes particularly impact sensitive species and microorganisms, yet limited research has explored the effects of wildfire ash and agricultural byproducts, such as rice straw ash, on amphibians. This study aims to investigate the effects of both wildfire and rice straw ashes on the skin microbiota of Rana dybowskii tadpoles and adult frogs, using ash aqueous extracts (AEAs). While alpha diversity showed significant variation among tadpoles, it remained stable in adult frogs. Beta diversity analyses revealed distinct microbiota compositions, especially between control and wildfire ash-treated tadpoles. Linear discriminant analysis (LDA) Effect Size (LEfSe) analysis indicated that different ash treatments led to the enrichment of specific microbiota, reflecting the complex effects of environmental changes on amphibian skin microbiota. Specific bacterial enrichments were associated with each treatment group, and phenotypic analysis highlighted bacterial traits, including Aerobic, Anaerobic, Potentially_Pathogenic, and Stress_Tolerant, providing insights into ecological adaptations. Therefore, contrasts wildfire and rice straw ash treatments distinctly influence amphibian skin microbiota and associated bacterial traits. Our findings emphasize the impact of agricultural and wildfire ash on amphibian skin microbiota, offering key ecological insights into the challenges posed by global environmental changes.

Impact of Central Line-Associated Bloodstream Infections on Mortality and Hospital Stay in Adult Patients at a Tertiary Care Institution in Cali, Colombia, 2015-2018.

Background: Central line-associated bloodstream infections (CLABSIs) are a significant healthcare challenge globally, increasing mortality risk and complicating central vascular catheter use. In Colombia, few studies have assessed the impact of CLABSIs on hospital stay and mortality. Objective: To determine the association between CLABSIs and discharge outcomes and hospital stay duration in adult patients at a tertiary care institution in Cali, Colombia, from 1 January 2015 to 31 December 2018. Methods: A nested case-control study was conducted. The odds of mortality associated with CLABSIs were estimated using conditional logistic regression. Non-conditional logistic regression was used to determine the odds of mortality when CLABSIs were caused by resistant microorganisms. Hospital stay duration, catheter duration, and time from catheter insertion to discharge were compared between patients with and without CLABSIs. The most frequent etiological agents were identified. Results: Patients with CLABSIs had 3.89 times the odds of mortality (95% CI [1.33-11.31], p = 0.013) compared to those without CLABSIs. The odds of mortality for patients with resistant microorganism CLABSIs were 4.04 times (95% CI [1.17-13.96], p = 0.027) higher than those with sensitive microorganism CLABSIs. Hospital stay duration (median = 51 days vs. 17 days; p = 0.000), catheter duration (median = 19 days vs. 7 days; p < 0.001), and time from catheter insertion to discharge (median = 40 days vs. 9 days; p < 0.001) were significantly longer in CLABSI patients. Klebsiella pneumoniae was the most isolated pathogen (20.2%), followed by Staphylococcus aureus (14.9%). Implications: CLABSI patients have longer catheter and hospitalization durations and higher mortality risk. Resistant microorganism CLABSIs are associated with elevated mortality risk. Conclusions: This study corroborates the positive relation between CLABSI and the mortality risk, which is influenced by resistant bacteria, though causality is not established. CLABSI is also linked to longer hospital stays, underscoring the need for improving infection control strategies.

Investigation of Freezing and Freeze-Drying for Preserving and Re-Using a Whole Microbial Cheese Community.

Preserving microbial ecosystems obtained from traditional cheese-making processes is crucial to safeguarding the biodiversity of microbial cheese communities and thus ensuring that the high flavor quality of traditional cheeses is maintained. Few protocols have been proposed for the long-term storage of microbial consortia. This work aimed to develop preservation methods to stabilize the entire microbial community in smear-ripened cheese without multiplication or isolation. A simplified microbial community, capable of reproducing the metabolic pattern of cheese maturation, was used in three independent cheese productions. Cheese samples were taken before and after the ripening step, mixed with maltodextrin or saline solution, and subjected to different stabilization conditions including freezing and freeze-drying, followed by 1 month of storage. Microbial survival was quantified using the colony-forming unit assay. Differential scanning calorimetry was used to relate the physical events occurring within the samples to the microbial storage stability. Freezing at -80 °C resulted in the lowest loss of culturability (<0.8 log unit), followed by freezing at -20 °C and freeze-drying. The ripening bacteria appeared as the most sensitive microorganisms within the community. Moreover, a successful cheese production using the best-stabilized community showed the possibility of preserving and re-using an entire microbial community of interest.

Antimicrobial activities of some species in Asteraceae and Lamiaceae families from Türkiye

The study aimed to investigate the antimicrobial activities of the species belong to Asteraceae and Lamiaceae families collected from Çorum, Eskişehir and Kütahya provinces in Türkiye on Gram (+) and Gram (-) bacterial strains using EUCAST disc diffusion method. Ethanol (96%) and Ciprofloxacin (5mcg) were used as negative and positive controls, respectively. All plant extracts produced inhibition zones on S. aureus and E. faecalis ranged between 4.67-14.33 mm and 21.67-23.67 mm respectively. The variance in the antimicrobial activities of the plant extracts was significant between groups according to ANOVA. L. angustifolia samples collected from Eskişehir and Kütahya gave zone diameters close to the positive control on S. aureus and E. faecalis. It was determined that E. coli was the most resistant and S. aureus and E. faecalis were the most sensitive microorganisms in this study. L. angustifolia-E, M. piperita and S. officinalis were the species whose extracts were coming front with their high antimicrobial activities. Pearson's correlation analyses displayed that the antimicrobial activity on E. coli was correlated positively and negatively with altitude and latitude respectively, while on E. faecalis was positively correlated with altitude and negatively correlated with latitude and longitude. In conclusion, the variations in the antimicrobial activities of the secondary metabolites found in the extracts of medicinal aromatic plants are important and, although the quantity, quality, and diversity of these compounds are determined according to the genotypes of plants, the environmental conditions in which the plants grow might have an impact on these differences.

Face-Centered Central Composite Design for the Optimization of the Extraction of Phenolic Compounds from Kernels and Shells of Raphia farinifera and Evaluation of the Antioxidant, Antimicrobial, and Anti-Inflammatory Activities

This study reports the extraction of phenolic compound from shells and kernels of the Raphia farinifera fruit and the biological activities of the extract. A face-centered composite design was established to optimize the extraction conditions: ethanol/water ratio (0-100%), solvent/powder ratio (10-30 mL/g), and extraction time (90-180 min). Subsequently, the extracts obtained under the optimal conditions were used for the evaluation of the radical scavenging capacity, the capacity to chelate ferric ions, and the antimicrobial and anti-inflammatory activities. The optimal extraction conditions for the shells are an extraction time of 134.24 min, 65% ethanol in water, and a solvent/substrate ratio of 21.16 mL/g, and for the kernel, an extraction time of 180 min, 94.3% ethanol in water, and a solvent/substrate ratio of 18.6 mL/g. In these conditions, the phenolic compounds were 95.36 mg EAG/L for the shell extract and 139.72 mg EAG/L for the kernel extract. The antioxidant activity revealed that the half-maximal inhibitory concentrations (IC50) of the kernel extracts are 22.32 μg/mL and 55.73 μg/mL for the shells. A reducing activity of Fe 3+ ions with an activity of 308.39 μg EAA/mg for the kernel extracts and 293 μg EAA/mg for the shells was observed. B. cereus was the most sensitive microorganism with a minimum inhibitory concentration (MIC) equal to the minimum bactericidal concentration (MBC) with a value of 156.25 ppm for the kernel extract while the shell extract showed MIC of 625 ppm and MBC of 2500 ppm. The IC50 values for the denaturation of proteins by extracts of shells and kernels are 0.76 μg/mL and 0.56 μg/mL, respectively. Membrane stabilization revealed IC50 values of 1054.54 μg/mL and 1339 μg/mL for the shell and kernel extracts, respectively. This work has shown the potential of Raphia farinifera extracts for the food industry and cosmetics.

Inhibition of high sulfur on functional microorganisms and genes in slightly contaminated soil by cadmium and chromium

It is generally accepted that sulfur can passivate the bioavailability of heavy metals in soil, but it is not clear whether high sulfur in cadmium (Cd) and chromium (Cr) contaminated soil has negative effect on soil microbial community and ecological function. In this study, total sulfur (TS) inhibited the Chao 1, Shannon, Phylogenetic diversity (Pd) of bacterial and Pd of fungi in slightly contaminated soil by Cd and Cr around pyrite. TS, total potassium, pH, total chromium, total cadmium, total nitrogen, soil organic matter were the predominant factors for soil microbial community; the contribution of TS in shaping bacterial and fungal communities ranked at first and fifth, respectively. Compared with the low sulfur group, the abundance of sulfur sensitive microorganisms Gemmatimonas, Pseudolabrys, MND1, and Schizothecium were decreased by 68.79–97.22% (p < 0.01) at high sulfur one; the carbon fixation, nitrogen cycling, phosphorus cycling and resistance genes abundance were significantly lower (p < 0.01) at the latter. Such variations were strongly and closely correlated to the suppression of energy metabolism (M00009, M00011, M00086) and carbon fixation (M00173, M00376) functional module genes abundance in the high sulfur group. Collectively, high sulfur significantly suppressed the abundances of functional microorganisms and functional genes in slightly contaminated soil with Cd and Cr, possibly through inhibition of energy metabolism and carbon fixation of functional microorganisms. This study provided new insights into the environmental behavior of sulfur in slightly contaminated soil with Cd and Cr.

Soil health assessment of an acidic red soil agricultural area and its restoration with biochar soil conditioners

AbstractIn light of growing concerns regarding food security and soil health, there is increasing emphasis on the assessment of soil health and efforts to improve or maintain the soil health of cultivated land. This case study Niutian Town in Jiangxi Province in southern China was selected as a typical red soil and a major grain‐producing area. This research involves an integrated evaluation model based on Entropy weight TOPSIS and emergy analysis to assess the soil health of cultivated land. An evaluation system was developed, comprising 31 indicators selected on the basis of resources and environments, with an emphasis on sensitive and promising microorganisms category indicators. Additionally, experiments were conducted to assess the ecological risk of soil pollution and develop novel soil conditioners. Our results indicate that Pb, Hg and Cd present a moderate ecological risk on 92.1% of the cultivated land. Furthermore, 56.8% of the cultivated land was ‘sub‐healthy’ or ‘unhealthy’. Biochar was found to be a soil conditioner with a good adsorption effect, with absorption rates reaching up to 99.9% and 88.3% for Pb and Cd, respectively. Additionally, g‐C3N4 was added to address pesticide contamination, which showed an adsorption rate of up to 75.2% for atrazine. This work develops a targeted remediation approach based on assessment results to address regional cropland soil health issues.

Antimicrobial activity of amazon medicinal plants

In recent decades, an increase in resistance of bacteria and fungi to antimicrobials has been observed. Therefore, have each other investigated the antimicrobial potential of plants with medicinal properties. In this context, the Amazon has a high variability of plants with potentially active compounds. Thus, the present study aimed to evaluate the antimicrobial activity of ethanol extracts from Amazonian medicinal plants. Leaves and stems of 19 plant species were dried, crushed and extracted by cold maceration with ethanol. The extracts were dried and solubilized at a concentration of 100 mg mL-1 to done antimicrobial activity assays using the agar diffusion method against gram-positive and gram-negative bacteria, and fungi of the genus Candida. Of the total of 38 extracts analyzed, 14 (36.8%) had antimicrobial activity against at least one of the microorganisms tested. The Brazilnut tree stem extract was active against the highest number of microorganisms, three bacteria (S. aureus, E. coli and K. pneumoniae) and three fungi (C. tropicalis, C. parapsilosis and C. krusei). The mulateiro leaf extract was active against three microorganisms, the saracura-mira stem extract against two, and the other extracts only against one microorganism. K. pneumoniae was the most sensitive microorganism, and the most resistant was C. albicans. The lowest values for minimum inhibitory concentration (MIC) for antibacterial activity were for stone-breaker stem extract against K. pneumoniae (0.048 mg mL-1), and for antifungal activity for Brasilnut tree stem against C. krusei (3.125 mg mL-1), stone-breaker leaf against C. guillermondii (3.125 mg mL-1), and mulateiro leaf against C. tropicalis (3.125 mg mL-1). The lowest values of minimum microbicidal concentration (MMC) were for the extracts of stone-breaker stem against K. pneumoniae (0.192 mg mL-1) and mulateiro leaf against C. tropicalis (3.125 mg mL-1). The tested Amazonian medicinal plants had antimicrobial activity, especially Brazilnut tree, this being the first report for this plant species.

BACTERIOPHAGES AS ANTIBIOTICS ALTERNATIVES TO COMBAT MULTIDRUG RESISTANT PATHOGENS: A REVIEW ARTICLE

Antibodies, probiotics, and antimicrobial peptides are currently undergoing clinical studies as potential options to treat infections as bacteria become more resistant to traditional antibiotics and as more medications lose their efficacy against drug-resistant bacteria. In various regions of the world, bacteriophages have also been employed as a form of therapy. The advantage of these approaches is that the disease-causing bacteria are the only ones that are treated, leaving the beneficial commensal microbial communities of the host intact. This antimicrobial does not typically have an impact on commensal bacteria in addition to its pathogenic targets, as do the majority of antibiotics. The phage exhibits a great bactericidal effect while altering the normal flora very little. The medical benefits of phages for antibioticresistant and sensitive robotic microorganisms are comparable These unique disease-treating techniques must be further developed in order to improve their availability, effectiveness, and dependability as antibiotic substitutes

Pharmacokinetics and Therapeutic Target Attainment of Meropenem in Pediatric Post-Liver Transplant Patients: Extended vs Intermittent Infusion

The aim of this study is to characterize the concentration-time profile, pharmacokinetics parameters, and therapeutic target attainment of meropenem in pediatric post-liver transplant patients according to the duration of infusion. This is a prospective cohort of pediatric transplant recipients with preserved renal function receiving meropenem 40 mg/kg every 8 hours. The patients were stratified into 2 groups based on infusion duration: G1 (15 minutes of intermittent infusion) and G1 (3 hours of extended infusion). Two blood samples per child were collected during the same interval within 48 hours of starting the antimicrobial. Meropenem concentrations were determined by high-performance liquid chromatography with tandem mass spectrometry. Pharmacokinetic parameters were assessed using a noncompartmental analysis. The therapeutic target was defined as 100% of the time above the minimum inhibitory concentration. Fourteen patients with 28 measured meropenem concentrations were included. Lower values of volume of distribution and meropenem clearance compared with other critically ill pediatric populations were found. All patients achieved the therapeutic target against gram-negative pathogens with a minimum inhibitory concentration of ≤8 mg/L. Patients receiving a 15-minute infusion had higher values of peak and trough concentrations, resulting in unnecessary increased total drug exposure when compared to patients receiving a 3-hour infusion (P < .05). Meropenem at 120 mg/kg/d attained the therapeutic target against sensitive microorganisms in pediatric liver transplant recipients. The extended infusion should be preferred for patient safety. Because of the pharmacokinetic changes resulting from liver transplantation, individualized meropenem dosing regimens may be necessary.

Antibacterial stigmastane-type steroids and other constituents from the leaves of Vernonia glabra (Steetz) Vatke (Asteraceae)

Two new stigmastane steroids (1 and 2) were isolated from the methanol extract of the leaves of Vernonia glabra, together with seventeen known compounds (3–19) including one fatty acid, four triterpenoids, four steroids, one trinitropropanoyl glucoside, and seven flavonoids. The structures of compounds 1 and 2 were assigned based on their IR, NMR and MS data, and by comparison with literature values. The MeOH extract, its fractions and isolated compounds were subjected to in vitro antibacterial assay against two Gram-positive (Staphylococcus aureus ATCC25923 and Streptococcus pneumoniae ATCC49619) and two Gram-negative (Escherichia coli ATCC8739 and Klebsiella pneumoniae ATCC10031) bacteria, using broth microdilution method. The extract and fractions exhibited (16 ≤ MIC ≤ 512 μg/mL) antibacterial activities. The isolated and tested compounds were also active (16 ≤ MIC ≤ 128 μg/mL) against the four pathogenic bacteria, with compound 2 being the most active and E. coli, the most sensitive microorganism.

Establishment of a Single Temperature Incubation Approach for Environmental Monitoring Samples with Focus on Mold Recoveries.

A robust environmental monitoring program is essential to properly estimate and identify microorganisms in cleanrooms, ensuring that microbial contamination remains acceptably low, and a good state of control is maintained in the manufacturing areas. The incubation conditions are important to support optimal microbial recoveries, considering that there is no single culture medium, temperature and incubation time that can recover all microorganisms. Particularly molds are quite sensitive microorganisms, and some species may have very specific nutritional and environmental needs. In this study, a two-phase approach was used to identify a single incubation-temperature approach that could recover most of the cleanroom microbial flora with focus on molds. Phase 1 included a growth promotion study performed in the laboratory using pharmacopeial and in-house strains, comparing different media (SDA and TSA) at single or dual incubation-temperature approaches for 5 or 6 days. Phase 2 was based on an in situ study where sampling was performed in different areas of a pharmaceutical facility, comparing the recoveries at different incubation conditions. In addition, extension studies of phase 1 and phase 2 were performed to get a better understanding of growth requirements for in-house molds. The results show that an incubation on Tryptone Soy Agar (TSA) at 25-30° for 3-4 days was able to recover most tested microorganisms in phase 1 and a large variety of microorganisms in phase 2, indicating that the single incubation-temperature is an optimal approach for the recovery of microorganisms in cleanrooms. Exceptions were noted for one strain of the species Cutibacterium acnes, a microaerophilic bacterium for which anaerobiosis and higher temperatures were needed, and two mold strains (Sistotrema brinkmannii and Stereum hirsutum), indicating that those molds required a specific media (Sabouraud Dextrose Agar, SDA) for their proliferation. The results showed that TSA incubated at single or dual incubation-temperature approach cannot compensate for the absence of SDA for some environmental molds that may be atypical in cleanrooms. Therefore, in addition to TSA, certain monitoring with SDA at e.g., cleanroom entrance points may be beneficial to recover molds with very specific nutritional requirements.

Investigation of Antimicrobial and Antioxidant Activities of some Lichens

This study investigated the antimicrobial and antioxidant properties of methanol extracts from five lichen species: Polycauliona candelaria (Syn. Xanthoria candelaria), Nephromopsis chlorophylla (Syn. Cetraria chlorophylla), Circinaria calcarea (Syn. Aspicilia calcarea), Bryoria capillaris (Syn. Alectoria cana), and Peltigera canina (Syn. Dermatodea canina). Antimicrobial activities were determined using the agar disc diffusion method, while minimal inhibitory concentration (MIC) values were determined using the micro-well dilution method. Among the lichen species, methanol extract of Circinaria calcarea exhibited the highest antimicrobial activity, with a 15 mm zone of inhibition against Escherichia coli and Bacillus cereus. It also demonstrated the lowest MIC value (31.25 μg/mL) against Bacillus cereus, Bacillus subtilis, Clostridium perfringens and Escherichia coli were the most sensitive microorganisms to lichens. Various antioxidant determination methods were employed to assess the antioxidant activities of the lichens, including ferric ion (Fe+3) reduction capacity, cupric ion (Cu+2) reduction capacity, ferric ion reducing antioxidant power (FRAP), DPPH radical scavenging activity, DMPD radical scavenging activity and metal chelating activity using the bipyridyl reagent. All lichens exhibited excellent antioxidant activity, particularly in metal chelating activity using the bipyridyl reagent. Peltigera canina demonstrated the highest antioxidant activity among the studied lichen species across most of the applied method.

Seasonality Is the Main Determinant of Microbial Diversity Associated to Snow/Ice around Concordia Station on the Antarctic Polar Plateau.

The French-Italian Concordia Research Station, situated on the Antarctic Polar Plateau at an elevation of 3233 m above sea level, offers a unique opportunity to study the presence and variation of microbes introduced by abiotic or biotic vectors and, consequently, appraise the amplitude of human impact in such a pristine environment. This research built upon a previous work, which explored microbial diversity in the surface snow surrounding the Concordia Research Station. While that study successfully characterized the bacterial assemblage, detecting fungal diversity was hampered by the low DNA content. To address this knowledge gap, in the present study, we optimized the sampling by increasing ice/snow collected to leverage the final DNA yield. The V4 variable region of the 16S rDNA and Internal Transcribed Spacer (ITS1) rDNA was used to evaluate bacterial and fungal diversity. From the sequencing, we obtained 3,352,661 and 4,433,595 reads clustered in 930 and 3182 amplicon sequence variants (ASVs) for fungi and bacteria, respectively. Amplicon sequencing revealed a predominance of Basidiomycota (49%) and Ascomycota (42%) in the fungal component; Bacteroidota (65.8%) is the main representative among the bacterial phyla. Basidiomycetes are almost exclusively represented by yeast-like fungi. Our findings provide the first comprehensive overview of both fungal and bacterial diversity in the Antarctic Polar Plateau's surface snow/ice near Concordia Station and to identify seasonality as the main driver of microbial diversity; we also detected the most sensitive microorganisms to these factors, which could serve as indicators of human impact in this pristine environment and aid in planetary protection for future exploration missions.

Impacts of snow-farming on alpine soil and vegetation: A case study from the Swiss Alps

Snow-farming is one of the adaptive strategies used to face the snow deficit in ski resorts. We studied the impact of a shifting snow-farming technique on a pasture slope in Adelboden, Switzerland. Specifically, we compared plots covered by a compressed snow pile for 1.5, 2.5 or 3.5 years, which then recovered from the snow cover for three, two or one vegetation seasons, respectively, with control plots situated around the snow pile.In plots with >1.5 years of compressed snow pile, plant mortality was high, recovery of vegetation was very slow, and few plant species recolonized the bare surface. Soil biological activity decreased persistently under prolonged snow cover, as indicated by reduced soil respiration. The prolonged absence of fresh plant litter and root exudates led to carbon (C) limitation for soil microbial respiration, which resulted in a significant decrease in the ratio of total organic carbon to total nitrogen (TOC/TN) under the snow pile.Microbial C, nitrogen (N) and phosphorus (P) immobilization decreased, while dissolved N concentration increased with compressed snow cover. Longer snow cover and a subsequent shorter recovery period led to higher microbial C/P and N/P but lower microbial C/N. Nitrate and ammonium were released massively once the biological activity resumed after snow clearance and soil aeration.The soil microbial community composition persistently shifted towards oxygen-limited microbes with prolonged compressed snow cover. This shift reflected declines in the abundance of sensitive microorganisms, such as plant-associated symbionts, due to plant mortality or root die-off. In parallel, resistant taxa that benefit from environmental changes increased, including facultative anaerobic bacteria (Bacteroidota, Chloroflexota), obligate anaerobes (Euryarchaeota), and saprophytic plant degraders.We recommend keeping snow piles in the same spot year after year to minimize the area of the impacted soil surface and plan from the beginning soil and ecosystem restoration measures.

Adaptability of agricultural soil microbial nutrient utilization regulates community assembly under mulching measures on the Loess Plateau

Soil microbial nutrients and resource availability improve with mulching in agroecosystems, resulting in changes of soil microbial nutrient utilization strategies. However, the responses of soil microorganisms to nutrient utilization processes to regulate community assembly and thus maintain resource availability have not been clarified. Here, we performed a long-term field experiment with mulching measures, including no-mulching (NM), straw mulching (SM), plastic mulching (PM), and ridge mulching (RM), conducted on the Loess Plateau of China, to explore the community assembly process in response to microbial nutrient utilization. Microbial nutrient utilization strategies were analysed by measuring soil nutrients, microbial biomass, and extracellular enzyme activities. The results showed that PM and RM acquired C and N nutrients by secreting C- and N-extracellular enzymes in response to C:N- and C:P imbalances in soil chemistry, thereby reducing the nutrient limitation on microbial metabolism and improving microbial C utilization efficiency (CUE). Soil extracellular enzymatic stoichiometry increased and N utilization efficiency (NUE) decreased under mulching and drove an increase in beta-diversity and dominant species abundance in fungal communities. Mulching measures promoted the modular distribution of sensitive microorganisms and aggregation of fungal networks under PM and RM by reducing the stoichiometric imbalance and extracellular enzymatic N:P. At the same time, the microbial community assembly gradually changed from a stochastic to a deterministic process in response to the alleviation of soil C:P imbalance and changes in microbial nutrient utilization, in which the fungal community was dominant. In conclusion, soil microorganisms adaptively responded to changes in soil microbial nutrient utilization through the enhancement of aggregation of fungal co-occurrence networks and deterministic assembly processes. This study provides a better understanding of the impact of mulching on microbial nutrient utilization strategies from a community assembly perspective.

Evaluation of the biocontrol effect of Trichoderma sp. Trs GT2 extracts produced by fermentation processes against Botrytis cinerea Btcr GM3

AbstractIn the present work, the evaluation of the use of Trichoderma spp. for controlling different phytopathogens of agricultural importance (Fusarium oxysporum, Rhizoctonia solani, Sclerotinia sclerotiorum, Botrytis cinerea, Colletotrichum gloeosporioides, and Phytophthora sp.) was carried out. Confrontation assays by dual culture, volatile metabolites (overlapping plate assay), and diffusible metabolites (poison medium assay) were performed to identify and select the Trichoderma strain with a greater spectrum of inhibition and the most sensitive phytopathogen. The production of hydrolytic enzymes associated with biological control by the Trichoderma sp. Trs GT2 strain (chitinase, cellulase, amylase, and lipase) was evaluated. Subsequently, the use of solid‐state and submerged fermentation to produce extracts with antagonistic activity against B. cinerea was evaluated, and the production of specific activity β 1–3 glucanase was compared. It was found that Trichoderma sp. Trs GT2 presented the greatest spectrum of inhibition against the phytopathogens evaluated, resulting in the strain of B. cinerea being the most sensitive microorganism to its effects (percentages of inhibition: dual culture 100%, volatile metabolites 100% and diffusible metabolites 28.24%). The Trichoderma sp. Trs GT2 strain showed amylase, cellulase, and chitinase activity. It also produced activity titers β 1–3 glucanase of 13.22 U/g by solid‐state fermentation (SSF) and 8.19 U/mL by submerged fermentation, as well as specific activities of (1.38 U/mg) and (14.23 U/mg), respectively. The extracts produced by both fermentation systems did not present an antagonistic effect against B. cinerea; this can be attributed to the need for interaction with the phytopathogen in question for the induction of metabolites with antagonistic activity, as well as to the confusion that the evaluation of the antagonistic effect of diffusible metabolites, through the cellophane paper technique, can generate in which the mechanism of nutrient competition can cause the inhibitory effect. This work shows that the ability of one microorganism to exert biocontrol against another can vary depending on the mechanism through which it performs and demonstrates that the antagonist‐phytopathogenic interaction can promote the production of metabolites with antagonistic activity.