Fluorescein Diacetate Hydrolysis Research Articles

Short-term service crops affect the spatial organization of soil aggregates, microbial C[sbnd]N biomass, and microbial activities in a degraded monoculture system

Service crops are grown to provide ecosystem services, such as the ability to increase soil organic matter and fertility. Also, they reduce erosion processes, weed control, disease regulation, water purification, soil biodiversity, and physical restoration. The physical arrangement of elemental particles in soil aggregates controls many ecosystem functions such as soil stability and carbon sequestration. This study aimed to analyze the short-term effect of including different service crops on the soil aggregate dynamics in a degraded common bean monoculture system and how it influences the rhizospheric microbial activity, carbon, and nitrogen microbial biomass. Here, we measured soil water-stable aggregates, particulate and associated organic carbon, soil microbial biomass, microbial activity, service crop aerial biomass, and cash crop yield in bulk soils during the 2020/2021 and 2021/2022 agricultural cycles. Soil samples from depths of 0–10 cm from five management treatments (annual service crop/common bean) were analyzed under no-tillage: 1) Oat (O) = Avena sativa/common bean; 2) Wheat (W) = Triticale/common bean; 3) Vetch (V) = Vicia villosa/common bean; 4) Melilotus (Me) = Melilotus alba/common bean; 5) common bean monoculture (M) = common bean without service crop. Additionally, two controls were analyzed: 6) Brachiaria perennial (BP) = Brachiaria brizantha perennial; 7) Native vegetation (NV). Service crops significantly increased aggregate stability, mean weight diameter, particulate matter and associated organic carbon, promoting the formation of large macroaggregates (0.25–2 mm and > 2 mm). This led to an increase in carbon stocks. Microbial activity expressed as hydrolysis of fluorescein diacetate and acid phosphatase activity, increased in the largest fraction for all service crops. Vicia improved surface residues; on average all service crops increased the common bean yield by 107.25 %. In summary, Vicia represents the best alternative as a service crop to improve the quality and health of degraded monoculture soils.

ACC deaminase producing bacteria alleviate the polyethylene glycol induced drought stress in black gram (Vigna mungo L.) by enhancing nutrient uptake and soil respiration activity

The present study aimed to exploit ACC deaminase (ACCD) producing drought-tolerant bacteria to mitigate drought stress (PEG stress) and simultaneous enhancement of the essential nutrients (N and P), relative water content (RWC), and chlorophyll pigment. In this study, 80 previously isolated ACCD-producing bacteria were screened for drought tolerance, and the results showed that 13.75 % (11isolates) were tolerant to up to -0.73 MPa. Further, screening of these drought tolerant ACCD producers revealed that the 11 isolates produced siderophore (96.82–99.67 %), indole-3-acetic acid like substances (15.15–70.55 µg/mL), and phosphate solubilization (39.33–142.67 µg/mL). Furthermore, pot studies (2000 ppm PEG stress) revealed an enhanced root (40.97–174.24 %) and shoot length (14.06–194.86 %) in inoculated plants compared to the control plants. In addition, inoculated plants also enhanced the uptake of nitrogen (35.10–42.61 mg/g) and phosphorus (2.67–3.68 mg/g), relative water content (55.26–83.33 %), chlorophyll (15.83–47.25 mg/g) and ACCD production in the soils (2.03–5.51 µmol/mL). The inoculated bacteria also enhanced the soil respiration activity such as dehydrogenase enzyme (65.31–144.48 µg/g), fluorescein diacetate hydrolysis (19.27–55.25 µg/g), and alkaline phosphatase (611.53–1011.53 µg/g). In conclusion, IPTS 7 (Rhodococcus kroppenstedtii) and CWN 5 (Bacillus altitudinis) can be used to mitigate drought stress and mobilize essential nutrients (N and P).

Nickel sources affect soil biological properties but do not affect sorghum growth

Nickel (Ni) is an essential element, but it can be phytotoxic in high concentration, which may be caused by high availability in soil solution. The objective of this study was to evaluate the effect of sources and doses of Ni applied to a dystrophic Red Latosol cultivated with sorghum on i) the availability of the metal in the soil; ii) the impact on biological and biochemical properties of the soil; iii) the absorption and distribution in sorghum plants; and iv) crop productivity. The experiment was carried out within a completely randomized design with two nickel sources [nickel(II) nitrate, Ni(NO3)2 and nickel(III) oxide, Ni2O3], three doses (35, 70, and 140 mg Ni kg−1 soil), plus controls without Ni, with 3 replications. The concentrations of Ni in the soil, soil microbial biomass (SMB), basal soil respiration (BSR), metabolic quotient (qCO2), fluorescein diacetate (FDA) hydrolysis, and urease activity were determined. The concentrations of Ni in the leaf diagnostic and in the plant (shoot, root, and grains) were also measured. In the soil, the concentrations of available Ni remained between 0.21 and 54.01 mg Ni kg−1. Ni2O3 contributed very little to the increase in available Ni. SMB and the FDA hydrolysis were not affected by the Ni source or Ni dose, but BSR and qCO2 had significant increase with Ni application rates, suggesting the soil microorganisms faced stress. Soil urease activity was affected by Ni dose but not by Ni source. The dose of Ni as Ni(NO3)2 decreased the metal concentration in the plant, while that of Ni2O3 increased it. Nickel source did not affect dry mass production of the plants, but grain yield was affected in a dose-dependent manner when Ni2O3 was the source of Ni.

Short-term impacts of polyethylene and polyacrylonitrile microplastics on soil physicochemical properties and microbial activity of a marine terrace environment in maritime Antarctica

Evidence of microplastic (MP) pollution in Antarctic terrestrial environments reinforces concerns about its potential impacts on soil, which plays a major role in ecological processes at ice-free areas. We investigated the effects of two common MP types on soil physicochemical properties and microbial responses of a marine terrace from Fildes Peninsula (King George Island, Antarctica). Soils were treated with polyethylene (PE) fragments and polyacrylonitrile (PAN) fibers at environmentally relevant doses (from 0.001% to 1% w w−1), in addition to a control treatment (0% w w−1), for 22 days in a pot incubation experiment under natural field conditions. The short-term impacts of MPs on soil physical, chemical and microbial attributes seem interrelated and were affected by both MP dose and type. The highest PAN fiber dose (0.1%) increased macro and total porosity, but decreased soil bulk density compared to control, whereas PE fragments treatments did not affect soil porosity. Soil respiration increased with increasing doses of PAN fibers reflecting impacts on physical properties. Both types of MPs increased microbial activity (fluorescein diacetate hydrolysis), decreased the cation exchange capacity but, especially PE fragments, increased Na+ saturation. The highest dose of PAN fibers and PE fragments increased total nitrogen and total organic carbon, respectively, and both decreased the soil pH. We discussed potential causes for our findings in this initial assessment and addressed the need for further research considering the complexity of environmental factors to better understand the cumulative impacts of MP pollution in Antarctic soil environments.

Microbiological attributes as indicators of soil quality in coffee growing systems in Southwest Bahia, Brazil.

Microorganisms are important indicators of soil quality due to their sensitivity to changes, reflecting the impacts caused by different land uses. The objective of this study was to evaluate the microbiological and physical-chemical attributes of the soil in areas cultivated with coffee under three different management systems (shaded coffee and full sun coffee with two spacings), as well as in adjacent areas under pasture and native forest, in Bahia, Brazil. The microbiological and physicochemical indicators evaluated were basal soil respiration (MBR), soil total organic carbon (TOC), microbial biomass carbon (MBC), metabolic quotient (qCO2), microbial quotient (qMic), enzyme activities (urease, acid phosphataseand fluorescein diacetate hydrolysis (FDA)). Physical and chemical indicators (particle size, texture, pH, P, K+, Ca2+, Mg2+, Al3+, and sum of bases) were also evaluated. Biological and chemical attributes were much more discriminative of study areas in the dry season. Microbial quotient (qMic) and metabolic quotient (qCO2) in the dry season showed that pasture is the most degraded land use. Conversely, nature forest and coffee with Grevillea were similar and were the best ones. In general, soil quality indicators were more sensitive to discriminate pasture and native forest from coffee systems, which, in turn, were not well discriminated among themselves.

Asynchronous application of modified biochar and exogenous fungus Scedosporium sp. ZYY for enhanced degradation of oil-contaminated intertidal mudflat sediment.

Intertidal mudflats are susceptible to oil pollution due to their proximity to discharges from industries, accidental spills from marine shipping activities, oil drilling, pipeline seepages, and river outflows. The experimental study was divided into two periods. In the first period, microcosm trials were carried out to examine the effect of chemically modified biochar on biological hydrocarbon removal from sediments. The modified biochar's surface area increased from 2.544 to 25.378 m2/g, followed by a corresponding increase in the hydrogen-carbon and oxygen-carbon ratio, indicating improved stability and polarity. In the second period, the effect of exogenous fungus - Scedoporium sp. ZYY on the bacterial community structure was examined in relation to total petroleum hydrocarbon (TPH) removal. The maximum TPH removal efficiency of 82.4% was achieved in treatments with the modified biochar, followed by a corresponding increase in Fluorescein diacetate hydrolysis activity. Furthermore, high-throughput 16S RNA gene sequencing employed to identify changes in the bacterial community of the original sediment and treatments before and after fungal inoculation revealed Proteobacteria as the dominant phylum. In addition, it was observed that Scedoporium sp. ZYY promoted the proliferation of specific TPH-degraders, particularly, Hyphomonas adhaerens which accounted for 77% of the total degrading populations in treatments where TPH removal was highest. Findings in this study provide valuable insights into the effect of modified biochar and the fundamental role of exogenous fungus towards the effective degradation of oil-contaminated intertidal mudflat sediments.

Soil Microbial and Enzymatic Properties in Luvisols as Affected by Different Types of Agricultural Land-Use Systems and Soil Depth

Determination of the microbial and enzymatic properties in soil is primarily concentrated on the surface layers of the soil profiles; however, it is well known that the transformation of soil organic matter also occurs in the deeper horizons of the soil profile. The aim of this study was to assess any changes in specific sets of enzyme activities and their associated physicochemical properties as affected by two different agricultural land-use systems and soil depth. Changes in the studied properties were determined across four Luvisol profiles in two agricultural land uses (arable land and vineyards). The enzyme activities associated with the transformation of C, N and P were analyzed. Additionally, the activity of some oxidoreductases and the fluorescein diacetate hydrolysis (FDAH) rate were also determined. Moreover, the content of the various forms of soil carbon, nitrogen, phosphorus (including microbial biomass C, N and P) and some other properties (pH, clay and silt content) were assessed. Agricultural land use significantly affected the microbial biomass content and as well as the studied enzyme activities. Most of the studied enzymes exhibited a higher activity in the grapevine (GV) profiles, which was followed by the winter wheat (WW) profiles; however, the largest variability occurred for the urease activity. There was no clear differentiation between the two studied land uses for the activity of nitrate reductase, dehydrogenases, acid phosphatase, or endo- and exo-cellulase. Irrespective of the plant being cultivated, the soil variables decreased significantly with increasing soil depth, wherein the greatest changes were observed between the surface and sub-surface soil horizons (I–II). The activity of some enzymes (e.g., the urease activity in WW profiles) decreased gradually across the soil profiles, while others were located almost solely within the surface layers (e.g., the nitrate reductase activity in the GV profiles as well as invertase in the WW profiles). The α-glucosidase activity did not exhibit any statistically significant changes along the analyzed profiles. The activity of phenol oxidase and peroxidase also revealed different trends along the studied profiles compared to the other enzymes and did not decrease gradually with depth. The microbial biomass of the C, N and P content was generally the highest in the upper horizons and gradually decreased with depth, wherein the largest decrease was observed between the surface and sub-surface horizon. The studied enzyme activities were more dependent on the soil carbon content compared to the other soil properties. And thus, in the C-rich horizons (C > 4 g kg) for the surface and subsurface layers the enzyme activities were highly correlated with TOC, DOC and MBC content as compared to the deeper, C-low horizons (C < 4 g kg). By examining how the microbial and enzymatic properties change across the soil profiles, it is possible to gain valuable insight into the long-term biogeochemical processes that are involved in soil fertility and in the health of agricultural ecosystems.

Direct and indirect effects of Basta®, a glufosinate-based herbicide, on banana plantation soil microbial diversity and function

Herbicide applications have doubled over the past 30 years to control weeds, but their use may influence soil microbial communities, which mediate important ecosystem services. Here, we characterised the direct effects of a single application of Basta® (glufosinate), at 1× and 2× the recommended rate (5 and 10 kg product ha−1), as well as the indirect effects of vegetation loss on the diversity and function of soil microbial communities within a banana plantation. A 10-month pre-experimental period using Basta® to remove additional vegetation from half of the experimental area created conditions for assessing the indirect herbicide effects. Direct assessments on soil microbial communities began when the Basta® herbicide treatments were applied to the areas with and without vegetation and continued over multiple time-points, for 56 days. Herbicide treatment had no significant direct impacts on basal, and substrate induced respiration rates, or the potential activities of microbial enzymes as inferred from fluorescein diacetate hydrolysis (FDA) and β-glucosidase assays. Similarly, phylogenetic marker gene sequencing indicated that Basta® application did not significantly influence the diversity of soil bacterial or fungal communities. Indirectly, Basta® had a greater influence on the soil microbial activity and functions by removing understory vegetation cover around banana plants. This suggested that continual use of herbicides to reduce soil vegetation cover under bananas had a greater impact on soil microbial communities than a single application of the herbicide. Furthermore, the presence or absence of vegetation cover, significantly altered the abundance of Fusarium oxysporum, plus an additional eight bacterial and ten fungal taxa. Our results indicated that a single application of glufosinate as Basta® at the recommended or double the recommended rate, did not adversely affect soil microbial communities or their activities in banana plantations directly. However, application of herbicides, such as Basta® in crops like banana, indirectly alters soil microbial communities and their activities through loss of vegetation cover and should only be used as a component of an integrated weed management system.

Individual and combined effects of earthworms and Sphingobacterium sp. on soil organic C, N forms and enzyme activities in non-contaminated and Cd-contaminated soil

Earthworms and Sphingobacterium sp. are known for their strong organic compound decomposition ability and wide distribution in soil. However, interactions of soil organic matter decomposition with soil properties and whether microbial species such as Sphingobacterium sp. could assist earthworms in carbon and nitrogen transformation in soil remain poorly understood. Earthworms (Eisenia fetida, Amynthas gracilis) and Sphingobacterium sp. were introduced in non-contaminated and cadmium-contaminated soils under controlled laboratory conditions for 20 days. We examined their individual or combined effects on carbon and nitrogen forms and related enzyme activities to assess their influence on soil C and N cycling. Individual Sphingobacterium sp. inoculation led to significantly decreased organic carbon (SOC) contents, reducing it by 16.5% in non-contaminated soil and by 3.77%, in Cd-contaminated soil. It resulted in an increased microbial biomass carbon (MBC) contents, reaching 1685 ± 292 mg·kg−1 in non-contaminated soil. Individual introductions of E. fetida and A. gracilis caused a decline in SOC content in non-contaminated soil, but increased significantly dissolved organic carbon (DOC) and alkali-hydrolysable nitrogen (AN) contents by 75.8%, 53.6% and 32.9%, 20.9%, respectively. In contrast, in Cd-contaminated soil, only the significant combined effects of earthworms and Sphingobacterium sp. were linked to significant increase in SOC contents, raising by 7.22% and 9.64% in E. fetida + Sphingobacterium sp. and A. gracilis + Sphingobacterium sp. treatments, respectively. In non-contaminate soil, the combined effects of earthworm and Sphingobacterium sp. further increased DOC and AN content by 212%, 134% and 31.3%, 25.4% in the treatments of E. fetida + Sphingobacterium sp. and A. gracilis + Sphingobacterium sp., respectively; the highest ratios of DOC to SOC and AN to total Nitrogen (TN) were found in the earthworm + Sphingobacterium sp. treatments as well. In non-contaminated soil, Sphingobacterium sp. and earthworms mainly influenced β-glucosidase (BG), urease (URE), N-acetyl-β-d-glucosaminidase (NAG) activities and fluorescein diacetate hydrolysis (FDA) hydrolysis, while in Cd-contaminated soil, they mainly influenced invertase (INV), NAG, URE, and protease (PRO) activities. Principal component analysis indicated that in non-contaminated soil, the earthworm activities dominated the mineralization processes of soil carbon and nitrogen, and Sphingobacterium sp. can intensify this process when it was inoculated in soil along with earthworms. Furthermore, both earthworm species increased C and N levels by elevated INV and PRO activities in combined inoculation. However, in contaminated soil, the impact of earthworm inoculation on soil C stabilization showed a species dependent pattern. E. fetida reduced C mineralization by decreasing URE activities, while A. gracilis enhanced C stabilization by increasing INV activities and decreasing PRO activities. In conclusion, earthworms played a key role in enhancing C and N mineralization in non-contaminated soil and promoting C stabilization in contaminated soil. Both earthworm species followed similar strategies in the former process but adopted different strategies in the latter. When introduced individually, Sphingobacterium sp. was able to promote mineralization in both soils, primarily assisting earthworms in improving carbon and nitrogen mineralization in non-contaminated soil but hindering these processes in Cd-contaminated soil. These findings provide insights into the combined effects of earthworms and microorganisms on carbon and nitrogen cycling.

Litter from Native Shrubs in the Senegal River Valley Induces Modifications in Nematode Communities and Enzyme Activities in Cultivated Sandy Soils

ABSTRACT To reduce plant-parasitic nematodes (PPNs), an alternative solution based on amendments from selected native shrub was used to favor mainly the increase of free-living nematodes (FLNs) that include high trophic (bacterivorous, fungivorous, omnivorous, and carnivorous) nematodes and influence soil microbial activities. The consequences of the subsequent reduce of PPNs of the soil were also determined. Experiments were performed in a shade house using six treatments consisting of shrub residues from Piliostigma reticulatum (Pil), Boscia senegalensis (Bos), and Crotalaria juncea (Cro); a Straw-based Compost (Cs); a Farmer practice (FP) using Nitrogen-Phosphorus-Potassium (NPK) fertilizer; and a control (C0, no amendments). Abundances of nematodes, trophic groups, and nematodes ecological indices were determined. Enzymatic activities (ß-glucosidase and acid phosphatase) and the fluorescein diacetate hydrolysis (FDA) were also determined. Soil amended by Bos and Cro increased the density of nematodes compared to control soil or amended with NPK fertilizer. Indices of taxonomic diversity (H') did not differ significantly between the treatments. However, soils amended with Bos and Cro had the highest enrichment index (EI), and the lowest Nematode Channel Ratio (NCR), indicating that these two shrub residues exhibited a higher food web in response to the available resources provided by the fungal decomposition pathway. Moreover, Bos favored omnivorous and increased enzymatic activities. Bos induce ‘bottom-up’ while Cro induce ‘top-down’ controls on nematode populations.

Assessing indoor PM2.5 microbial activity in a university campus environments in Beijing

Most people spend 90 % of their time inside, indoor bioaerosols significantly impact human health. This study aimed to investigate the substantial impact of indoor bioaerosols, particularly the harmful small particle-size components within Particulate Matter 2.5 (PM2.5), on human health in a crowded campus setting. Conducted during the summer at a Beijing university, the research assesses microbial activity within PM2.5 in offices (occupied by both teachers and students) and student dormitories, encompassing bedrooms and common areas. The optimized Fluorescein Diacetate (FDA) hydrolysis method was employed for assessment. Indoor microbial activity ranged from 1.18 to 176.56 ng m−3 sodium fluorescein while outdoor activity ranged from 6.14 to 90.15 ng m−3 sodium fluorescein. Meteorological factors, including heavy rain and strong winds, influenced the correlation between indoor and outdoor microbial activity, contrasting with the effect of air pollution levels. Offices with high occupancy and outdoor environments with strong winds or heavy rain often resulted in an I/O ratio >2, and a negative correlation was observed between the I/O ratio and indoor microbial activity. The study underscores the significance of ventilation type (air conditioning vs. natural ventilation), emphasising the importance of maintenance and clean living habits in reducing indoor microbial loads. Furthermore, it identifies population density as a pivotal factor affecting microbial activity in office air. This study contributes to assessing Indoor Air Quality (IAQ) and controlling bioaerosol pollution, and provides an effective measure for rapidly evaluating biological air pollution in crowded indoor environments using the PM-based microbial activity.

Development of Fast Method to Upscaling Microbial Inoculums on Two Seedling Testplants

We investigated the effect of different microbial species on the germination and growth of white mustard (Sinapis alba L.) and perennial ryegrass (Lolium perenne L.), tested for two weeks. The experiment was carried out in a cell tray, filled with sandy soil:compost (9:1) mixture. The following microorganisms were used as treatment: Enterobacter ludwigii, Bacillus megaterium, B. subtilis, Kosakonia cowanii, Pseudomonas fluorescens Hx1 bacteria and Trichorderma harzianum T-22 microscopic fungi. After two weeks, we assessed the number of germinated mustard seeds, the wet and dry weight of the mustard, the length of the mustard, the wet and dry weight and the length of the ryegrass. We measured the enzyme activity of the fluorescein diacetate hydrolysis analysis (FDA) of the soils and calculated the correlation of FDA with the parameters, tested on seedling-plants. FDA generally was positively correlated, however, the above findings could not be verified statistically. The simple and relatively fast method can be suitable for the cost-effective pre-testing of different microbes and for the pre-selection of strains that can be used in further field tests.

Formaldehyde Removal by Expanded Clay Pellets and Biofilm in Hydroponics of a Green Wall System

Air pollution with formaldehyde (FA) has been an emerging concern over recent years. This study was aimed at evaluating the contribution of green wall system-derived expanded clay pellets (ECP) and biofilms to FA removal in liquid phase. The effects of four plant species on this process were compared. An inhibition of the fluorescein diacetate hydrolysis activity of biofilm-derived microorganisms was detected during the exposure to FA in both air and liquid phases, and this effect was plant-species-specific. Liquid chromatography with a UV detector was applied for the quantification of FA. The FA removal activity of ECP in the liquid phase was 76.5 mg ECP−1 after a 24 h incubation in the presence of 100 mg/L FA, while the removal activity of the biofilm differed depending on the plant species used, with the highest values detected in the set with Mentha aquatica, i.e., 59.2 mg ECP−1. The overall FA removal from the liquid phase during 24 h varied in the range from 63% to 82% with the initial FA concentration of 100 mg/L. Differences in biofilm formation upon ECP enrichment were detected by using confocal laser scanning microscopy. These results contribute to the understanding of air biofiltration mechanisms in hydroponic systems.

Soil biological indicators associated with nitrogen mineralization patterns in rice soils under long‐term integrated nutrient management

AbstractIn long‐term integrated nutrient management (INM) involving organic amendments with inorganic fertilizer application, understanding nitrogen (N) mineralization is key to assessing soil functioning. In this study, soil samples were collected following rice cropping from treatments consisting of various combinations of inorganic with organic fertilizers, including farm yard manure, wheat straw or Green Leaf Manuring, as well as 100% inorganic and a control (no fertilizer). The soil samples were incubated for 120 days at 30°C for determining N mineralization potential, and the mineralization patterns were fitted to double first‐order kinetic models to separate the potentially mineralizable nitrogen (PMN) into readily available N (PMN‐I) and resistant N (PMN‐II) fractions. The half‐lives of PMN‐I and PMN‐II ranged from 1.2 to 3.3 days and 22.4 to 63.0 days, respectively. In the organically amended soils, we observed that microbial biomass carbon (MBC) and nitrogen (MBN) increased by 43% and 41%, respectively, compared to inorganic fertilizer application alone. Moreover, the soil enzyme activity increased, revealing enhanced biological activity (dehydrogenase—31.96 μg TPF, Urease—35.69 μg urea‐N, glucosidase—57.78 μg p‐nitrophenol, fluorescein diacetate hydrolysis—45.84 μg fluorescein, N‐acetyl β‐glucosaminidase—46.47 μg p‐nitrophenol released g−1 dry soil h−1). We determined that PMN‐I was affected by the soil urease activity; whereas, PMN‐II was regulated by soil organic carbon, MBC, MBN, dehydrogenase activity and fluorescein diacetate hydrolysing capacity. These findings elucidate the soil biological indicators associated with nitrogen (N) mineralization, which can help optimize INM practice.

Italian ryegrass (Lolium multiflorum L.)-rice (Oryza sativa L.) rotation promotes the nitrogen cycle in the rice rhizosphere through dominant ammonia-oxidizing bacteria

The dominant ammonium bacteria established in different crop rotations are directly related to the conversion and utilization of nitrogen (N) in paddy soil. This study investigated the ammonia oxidation process in the rice rhizosphere of Italian ryegrass (Lolium multiflorum L.)-rice (IRR), celery (Apium graveolens)-rice (CLR) and winter fallow-rice (WFR) rotations in South China through the amoA functional gene analysis based on Miseq high-throughput sequencing platform and qPCR methods. The abundance of amoA gene in IRR was increased by 116.67 % (P < 0.05) and 42.76 % (P > 0.05) compared with CLR and WFR, respectively. Nitrosomonas became the dominant genus in the rhizosphere of IRR, with the highest relative abundance (59.30 %). The contents of soil organic matter, total N and nitrate nitrogen (NO3−-N) in the rice rhizosphere soil in IRR were significantly higher than other two treatments (P < 0.05) by 12.47–14.31 %, 16.88–25.00 %, and 97.48–159.60 %, respectively. Although lower microbial diversity was observed in IRR, the soil fluorescein diacetate hydrolysis enzyme activities and ammonia monooxygenase activities in the rice rhizosphere were higher in IRR than those in CLR and WFR (P < 0.05). Also, the soluble sugar and crude protein of milled rice were highest in IRR among the three rotation treatments (P < 0.05). The ammonia oxidation efficiency of ammonium-oxidizing bacteria was largely dependent on key taxa, such as Nitrosomonas (dominant genus in IRR), rather than the dynamics of AOB community structure. The key amoA-nitrifier taxa of the AOB community developed in IRR are capable of promoting rice production by improving soil N cycle efficiency and reducing the loss of N. Our findings illustrate the regulatory mechanism of IRR on the rice rhizosphere AOB community and reveal the important role of winter ryegrass in promoting soil nitrogen cycling during nutrient transformation of agricultural ecosystems in paddy fields.

Noticeable Shifts in Soil Physicochemical and Biological Properties after Contrasting Tillage Management in Crop Rotations of Bean, Maize, and Amaranth in Ecuadorian Highland Soils

Soil biological properties are sensitive indicators of soil quality changes due to perturbations occurred under agricultural management. The effects of contrasting tillage, increasing nitrogen fertilization doses, and crop rotations [e.g., bean, maize, bean (BMB) and bean, amaranth, bean (BAB)] on soil physicochemical and biological properties in an Andean soil from Ecuadorian highlands were evaluated in this study. Acid phosphatase, β-Glucosidase, fluorescein diacetate hydrolysis, microbial biomass carbon (Cmic), soil basal respiration (BR), arbuscular mycorrhizal fungi (AMF) spore density, total glomalin content (TGRSP), and soil physicochemical properties were analyzed. Conventional tillage (CT) and crop rotation showed significant effects on soil physicochemical and biological properties. Towards the final crop rotations, no-tillage (NT) promoted BR, TGRSP, and higher AMF spore density in both crop rotations; the Cmic kept stable along time in BMB and BAB, while BR doubled its value when compared to CT. Results indicated that the AMF spore density increased by 308% at the end of the BMB, and 461% at the end of the BAB, while TGRSP increased by 18% and 32% at the end of BMB and BAB, respectively. Biological traits demonstrated to be strongly associated to the organic matter accumulation originated from crop residues under the NT post-harvest which improved soil moisture, biological activity, and AMF interaction. The conservative soil management system has definitively improved general soil properties when compared to soil conditions under the intensive soil management system in this research.

Agronomic and environmental aspects of organo-mineral fertilizers produced with a by-product of the intermediate process of tanning

IntroductionThe by-product of the intermediate process of tanning (BPIPT) can be used in the manufacturing of environmentally-friendly organo-mineral fertilizers (OMF). However, the presence of potentially toxic elements (e.g., chromium, Cr), can hinder the use of BPIPT in agriculture. This study aimed: i) to evaluate soil chemical and biological properties following the application of fertilizers produced with a BPIPT, in contrast to other OMF produced with traditional organic matrices; and ii) to assess the impacts of such products on wheat growth and nutrition.MethodsSamples (0-0.2 m) of two Oxisols [Red-Yellow Latosol (LVAd) and Red Latosol (LVd)] were used in this study, consisting of two experiments (with five treatments and five replicates) using different OMF, in a sequence: 1) incubation of fertilizers in soil samples for 30 days, and 2) wheat cultivation (30 days) after the fertilizer incubation. The treatments consisted of an arrangement of mineral fertilizers based on nitrogen, phosphorus, and potassium (NPK fertilizers), associated with OMF based on BPIPT (OM-IPT and OM-IPT+S) or commercial manure (OM-CM and OM-CM+S), with or without sulfur (S), and a control treatment. Elemental availability in soils and microbial attributes were determined after the incubation of the OMF in the soils. After wheat cultivation, plant biomass, nutritional composition, β-glucosidase activity, and fluorescein diacetate hydrolysis (FDA) were measured.Results and discussionThe application of BPIPT-derived OMF in the present study increased available Cr fraction contents in both soils. However, OM-IPT caused low soil acidification, enhanced wheat growth and nutrition, and stimulated microbial activity in soils (FDA and β-glucosidase), thus evidencing the agronomic and environmental benefits of this OMF and their potential to contribute to a cleaner, more sustainable agriculture.

Characterization of Biofilm Formation and Bacterial Resistance to Benzalkonium Chloride under Contrasting Cultivation Conditions

Benzalkonium chloride (BAC) is one of the most commonly used quaternary ammonium compounds in the pharmaceutical, cosmetic, and food industries. The aim of our study was to compare the physiological responses of Escherichia coli MSCL 332, Pseudomonas putida MCCL 650, and Staphylococcus epidermidis MSCL 333 on 50 mg/L BAC in rich and poor medium (100% and 5% tryptone soya broth (TSB)) in the temperature range from 8 °C to 37 °C, under static and shaking conditions. A high-throughput, 96-well microplate method was used to compare a broad range of cultivation conditions. The effect of BAC on growth, biofilm formation activity, and dehydrogenase and fluorescein diacetate hydrolysis activity was evaluated. Addition of BAC to 100% TSB inhibited biofilm formation at 37 °C by 2.4, 1.8, and 1.6 times for E. coli, P. putida, and S. epidermidis, respectively. In turn, BAC stimulated biofilm formation in E. coli in 5% TSB at 37 °C and 100% TSB at 8 °C, i.e., 1.4 and 1.3 times, respectively. Statistical optimization of broth composition with emphasis on biofilm formation and further testing under experimental conditions was performed with P. putida.

Piperine, a Plant Alkaloid, Exhibits Efficient Disintegration of the Pre-existing Biofilm of Staphylococcus aureus: a Step Towards Effective Management of Biofilm Threats.

Staphylococcus aureus causes a range of chronic infections in humans by exploiting its biofilm machinery and drug-tolerance property. Although several strategies have been proposed to eradicate biofilm-linked issues, here, we have explored whether piperine, a bioactive plant alkaloid, can disintegrate an already existing Staphylococcal biofilm. Towards this direction, the cells of S. aureus were allowed to develop biofilm first followed by treatment with the test concentrations (8 and 16µg/mL) of piperine. In this connection, several assays such as total protein recovery assay, crystal violet assay, extracellular polymeric substances (EPS) measurement assay, fluorescein diacetate hydrolysis assay, and fluorescence microscopic image analysis confirmed the biofilm-disintegrating property of piperine against S. aureus. Piperine reduced the cellular auto-aggregation by decreasing the cell surface hydrophobicity. On further investigation, we observed that piperine could down regulate the dltA gene expression that might reduce the cell surface hydrophobicity of S. aureus. It was also observed that the piperine-induced accumulation of reactive oxygen species (ROS) could enhance biofilm disintegration by decreasing the cell surface hydrophobicity of the test organism. Together, all the observations suggested that piperine could be used as a potential molecule for the effective management of the pre-existing biofilm of S. aureus.

Microbiological characterization of soil in Guadalupe Plateau, Piauí

The effects of replacing native forest with different pasture-based animal production systems on soil microbial biomass and enzymatic activity for fruit cultivation in the Guadalupe Plateaus (PI) were evaluated. Soil samples were collected during the dry and rainy seasons (0-10 cm). The monoculture systems studied were: Acerola, Banana, Guava, and a fragment of native Cerrado forest. The areas with solely banana and guava showed higher Cmic values compared to Acerola. The highest qCO2 results were observed in the acerola treatment during both the dry and rainy seasons. The highest values of fluorescein diacetate (FDA) hydrolysis potential were detected in the guava area in both seasons. The use of soil microbial carbon (Cmic), basal soil respiration (RB), qCO2, and the enzymatic activity of β-glucosidase, acid phosphatase, and FDA demonstrate sensitivity to soil management changes, making them efficient parameters for assessing alterations and ecological sustainability in soil biology in fruit cultivation areas in the southern region of Piauí state.