Rate Of Fluorescein Diacetate Hydrolysis Research Articles

Compost and Biochar to Promote Soil Biological Activities under Sweet Potatoes Cultivation in a Subtropical Semiarid Region

South Texas is located in a subtropical semiarid climate, and due to high temperature and irregular precipitation, farmers opt to leave their fields fallow during the summer months jeopardizing overall soil health. We evaluated whether sweet potato (Ipomoea batatas) cultivation coupled with drip irrigation could restore soil biological activities compared with bare fallow. Additionally, because sweet potatoes have high demand of soil nutrients, especially potassium (K), we evaluated the nutrient supply of locally sourced soil amendments. Sweet potato was cultivated during summer 2018 in McAllen, Texas, under control (no fertilizer), NPK (synthetic fertilizer), RC (yard-waste compost), and AC (compost produced under an enhanced composting process), and biochar (gasified walnut shell at 900°C), each with three replicates. Soil amendments were applied at different amounts to result in a rate of 80 kg K ha−1. Soil biological indicators were microbial biomass phosphorous, phosphatase activity, and the rate of fluorescein diacetate hydrolysis (FDA). Available nitrogen, phosphorus, potassium, and sodium were also quantified. Aboveground biomass and storage root yield estimated sweet potato’s agronomic performance. Cultivation and irrigation stimulated soil enzyme activities and microbial biomass-phosphorous. Sweet potato yields were the highest in NPK treatment but still 2.8 times lower than variety’s potential yield. Storage root yield was inversely related to aboveground biomass, suggesting that growing conditions benefited the production of shoot versus roots. Both biochar and AC treatments stimulated FDA rates and K availability. Soil pH and sodium concentration increased in all treatments over the growing season, possibly due to river-sourced irrigation water. Together, these findings show that crop cultivation promoted soil biological activities and the maintenance of nutrient cycling, compared to bare-fallow conditions. For a better agronomic performance of sweet potato, it would be necessary to identify management practices that minimize increase in soil pH and salinity.

Soil indicators respond to changes in banana plantation management

The north Queensland region of Australia produces over 90% of Australia's bananas. However, to maintain its importance as a banana-growing region, producers are seeking innovative methods to manage their plantations in order to protect environmentally sensitive areas, reduce impacts from climatic events and suppress soil borne diseases. The development of a healthy soil is an aspiration sought to address these constraints, using indicators based on soil physical, chemical and biological parameters. From 2012 to 2015, 86 soil samples were received for analysis from different banana management scenarios; conventional (53), newly planted fields (15), and Ecoganic production (18). Ecoganics is a farmer certification program that combines environmental management systems with sustainable production practices. A stepwise-discriminate analysis was used to determine a minimum set of soil parameters required to discriminate between management systems. Ten soil parameters: fluorescein diacetate hydrolysis rate (FDA), nematode enrichment and channel indices, B/(B+F) ratio (bacterivorous nematodes relative to bacterivorous and fungivorous nematodes), nematode diversity, and abundance of Fu2 fungivorous nematodes, Om4 omnivorous nematodes, Ba1 and Ba3 bacterivorous nematodes and abundance of the plant-parasitic nematode Helicotylenchus multicinctus were required to separate the different banana management systems. However, the separation of banana management groups had a 19% error, with the leave-one-out validation model confusing Ecoganic bananas with conventional bananas 22% of the time. The results confirmed that crop management has considerable effects on soil biology. The use of soil indicators can guide farm management decisions to implement practices most likely to overcome banana production constraints.

Optimisation for assay of fluorescein diacetate hydrolytic activity as a sensitive tool to evaluate impacts of pollutants and nutrients on microbial activity in coastal sediments

Fluorescein diacetate (FDA) assay has been widely applied in coastal research to quantify microbial activity in sediments. However, the present FDA assay procedures embodied in sediment studies potentially include operational errors since the protocol was established for studies of terrestrial soil. In the present study, we optimised the procedure of FDA assay using sandy and cohesive sediments to improve experiential sensitivity and reproducibility. The optimised method describes quantitative measurement of the fluorescein produced when 1.0g of fresh sediment is incubated with 50mM phosphate buffer solution (pH: 7.3) and glass beads (2g) at 35°C for 1h under a rotation of 50rpm. The covariation coefficient of the optimised method ranged from 1.9% to 3.8% and the method sensitivity ranged from 0.25 to 1.57. The improved protocol provides a more reliable measurement of the FDA hydrolysis rate over a wide range of sediments compared to the original method.

Response of soil enzymes to elevated CO2and temperature in weeds associated with rice-wheat cropping system

Biological properties of the soil have often been proposed as early and sensitive indicators of soil ecological stress or other environmental changes. In the present investigation, the soil samples were collected from weeds associated with rice-wheat cropping system from open-top chambers to assess the effect of elevated CO2 and temperature on soil enzymes. In Rabi season, higher activity of FDA hydrolysis rate was noticed in wild oat with 26.5 (μg fluorescein/g/h) at elevated CO2 + ambient temperature levels. Dehydrogenase activity was higher at enrichment of CO2for P. minor with 35.9 (μg TPF/g soil/24 h). Urease significantly was higher in enrichment of CO2+ elevated temperature with wild oat 34.6 (μg NH4/g soil/24 h) followed by wheat (31.5μg NH4/g soil/24 h) with elevated CO2+ ambient temperature. In Kharif season, enrichment of CO2 concentration in rhizosphere of Echinochloa crusgalli recorded with higher FDA hydrolysis rate (19.8 μg fluorescein/g/h), dehydrogenase activity (39.8 μg TPF/g soil/24 h) and urease activity (45.6 μg NH4/g soil/24 h) respectively. We found the carbon dioxide enrichment significantly increased the soil enzymes like dehydrogenase, fluorescein diacetate (FDA) hydrolysis and urease activity in weeds rhizosphere than the crops.

Cluster roots of Embothrium coccineum (Proteaceae) affect enzyme activities and phosphorus lability in rhizosphere soil

Cluster roots have a profound effect on their rhizosphere. Our aim was to determine the effect of cluster roots of Embothrium coccineum, growing under natural conditions, on soil enzyme activities and phosphorus (P) lability in its rhizosphere. We determined enzyme activities: acid phosphatase (P-ase), dehydrogenase and β-glucosidase, and the rate of hydrolysis of fluorescein diacetate (FDA), as well as P fractions in the cluster root rhizosphere at different cluster-root developmental stages (juvenile, mature, semi-senescent, senescent), in the non-cluster root rhizosphere, and in bulk soil. In addition, the concentrations of total P and manganese Mn in roots was measured. The rhizosphere of senescing cluster roots presented the highest P-ase, β-glucosidase and dehydrogenase activities, and fastest rate of FDA hydrolysis, being 2.6-, 4.6-, 3.3- and 25.8-fold greater, respectively, than those in the rhizosphere of mature cluster roots. The P fractionation showed that the inorganic P (Pi) fraction was 15 % greater in the rhizosphere of mature cluster roots than in that of other stages. Mature cluster roots showed the highest total [P], suggesting the fastest P uptake. Cluster roots of E. coccineum modified their rhizosphere depending on their developmental stage, presenting lower soil enzyme activities at the mature stage than at other development stages. In addition, mature cluster roots increased the Pi fraction in their rhizosphere, allowing the highest total root [P] at this developmental stage.

Short-Time Response of Microbial Communities to Waste Compost Amendment of an Intensive Cultivated Soil in Southern Italy

In an intensely cultivated soil in southern Italy, the effects of municipal waste compost on soil activities (basal respiration, β-glucosidase, and fluorescein diacetate (FDA) hydrolysis), Biolog functional diversity, pH, and electrical conductivity (EC) were estimated in a short period following amendment. Treatment with compost at 30 t ha−1 (dry matter) was compared to mineral fertilization and untreated soil. In these poor soils, organic amendment allowed the rapid recovery of an active and biodiverse soil community. While the addition of compost increased all microbial activities and EC, the pH did not change. Conversely, metabolic activity that was positively correlated to FDA hydrolysis rate initially was enhanced by compost but decreased with time and disappeared at the end of the incubation. Results indicated that waste compost amendments affected microbial activities, both at global and functional levels, favoring a rapid return of biological factors of fertility.

THE INFLUENCE OF pH ON ALGAL CELL MEMBRANE PERMEABILITY AND ITS IMPLICATIONS FOR THE UPTAKE OF LIPOPHILIC METAL COMPLEXES(1).

Uptake of lipophilic metal complexes by freshwater algae has recently been shown to be pH dependent. Here we look at different physiological aspects that could influence the diffusion of the lipophilic Cd complex, Cd(diethyldithiocarbamate)2 (0) (Cd(DDC)2 (0) ), into algal cells at different exposure pH values. Changes in cell membrane permeability were assessed as a function of pH for three species of green algae [Chlamydomonas reinhardtii P. A. Dang., Pseudokirchneriella subcapitata (Korshikov) Hindák, and Chlorella fusca var. vacuolata Shihira et R. W. Kraus] using two neutral, nonionic probes, fluorescein diacetate (FDA) and D-sorbitol. In parallel experiments, we exposed algae to inorganic Cd or to Cd(DDC)2 (0) and monitored Cd intracellular metal distribution, together with phytochelatin synthesis. For the three algal species acclimated at pH 5.5 (w/wo DDC 1 μM) and exposed at this pH, their permeability to FDA and D-sorbitol was consistently lower than for algae growing at pH 7.0 and exposed at this pH (P < 0.001). The ratio of the FDA hydrolysis rate measured at pH 7.0 with respect to the rate measured at pH 5.5 (both in the presence of DDC) correlated with the ratio of the Cd(DDC)2 (0) initial internalization rate constant obtained at pH 7.0 versus that obtained at pH 5.5 (three algae species, n = 9, r = 0.85, P = 0.004). Our results strongly suggest that acidification affects metal availability to algae not only by proton inhibition of facilitated metal uptake but also by affecting membrane permeability.

Intracellular esterase activity in living cells may distinguish between metastatic and tumor-free lymph nodes

One of the major clinical problems in breast cancer detection is the relatively high incidence of occult lymph node metastases undetectable by standard procedures. Since the ascertainment of breast cancer stage determines the following treatment, such a "hypo-diagnosis" leads to inadequate therapy, and hence is detrimental for the outcome and survival of the patients. The purpose of our study was to investigate functional metabolic characteristics of living cells derived from metastatic and tumor-free lymph nodes of breast cancer (BC) patients. Our methodology is based on the ability of living cells to hydrolyze fluorescein diacetate (FDA) by intracellular esterases and on the association of FDA hydrolysis rates with a specific cell status, both in physiological and pathological conditions. The present study demonstrates a significant difference in the ability to utilize FDA by lymph node cells derived from metastatic and tumor-free lymph nodes in general average, as well as in the metastatic and tumor-free lymph nodes of individual patients. Cells from metastatic lymph nodes had a higher capacity for FDA hydrolysis, and increased this activity after additional activation by autologous tumor tissue (tt). The association between increased FDA hydrolysis rate and activated T lymphocytes and antigen-presenting cells (APC) was shown. The results of the present study may contribute to predicting the risk of involvement of seemingly "tumor-free" axillary lymph nodes in occult metastatic processes, and to reducing false-negative results of axillary examination.

Microbiology of ornithogenic soils from the windmill islands, budd coast, continental Antarctica: Some observations on methods for measuring soil biomass in ornithogenic soils

A range of measures of microbial biomass were compared for their effectiveness and internal consistency in characterizing ornithogenic soils. Excellent correspondences ( r = 0.86–0.94, slope = 0.84–1.12) were found between four measures of total biomass (ATP, fluorescein diacetate hydrolysis rate, substrate induced respiration rate and algal + bacterial biomass) when they were compared using regression analysis. Bacterial numbers, estimated from agar plate counts, were found to be highly correlated with microscopy counts and total biomass measurements, though the best-fit relationship was curvilinear rather than linear. Measurement of the procaryotic and eucaryotic components of the soil microbiota by selective antibiotic inhibition was found to be unreliable. Other problems were noted when assay units were converted into microbial C using multiplication factors published in the literature. The substrate-induced-respiration method overestimated the bacterial biomass of occupied penguin colony soil by at least 4-fold when the standard conversion factor (1 mg C = 25μ1CO 2 h −1) was used. Total biomass was also overestimated when fluorescein-diacetate-hydrolysis rates were converted to microbial C. While all four approaches could provide relative measures of the biomass of the Antarctic microbiota, it was concluded that they should not be employed in isolation but always in parallel when such soils are initially analysed.

Development and comparison of methods for measuring growth of filamentous fungi on wood

Measures of fungal growth with potential for use on wood-chip media were developed. These included (i) visual inspection, (ii) substrate dry weight loss, (iii) rate of fluorescein diacetate hydrolysis, (iv) extractable protein content, and (v) chitin content of the colonized substrate. The responses of the various assays to different growing conditions were assessed by using them on measured weights of mycelium, collected at intervals from liquid media with various composition. Growth of various species on either nutrient supplemented or unsupplemented wood chips was then measured. Each assay measured a different aspect of growth. The relationship between these changed in a distinctive way for each species during growth. Chitin gave the best measure of biomass, whereas fluorescein diacetate hydrolysis was a measure of growth-related metabolic activity. The protein and substrate dry weight loss data gave information about fungal protein and carbohydrate metabolism of the species, respectively. Addition of nutrient supplement to the wood increased both biomass and growth-related metabolic activity. It also increased the amount of wood used to produce a given amount of biomass by about 500% with some species. Some species showed a strong capacity to lower their cellular protein concentration during growth, which is probably of advantage for growth on a low-N substrate such as wood. Used together, the assays gave insight into different strategies fungi use to grow on wood. Key words: fungi, growth, chitin, fluorescein diacetate.

Enzyme activity and microbial biomass in a field soil amended with municipal refuse

Changes in enzyme activity levels, in biomass-C content, and in the rate of fluorescein diacetate hydrolysis were measured in a loamy soil to which solid municipal refuse had been applied as compost over a 3-year period at two different rates. Addition of the compost caused significant increases in the activity of all enzymes tested. The increases were much higher at 90 t ha-1 year-1 than at 30 t ha-1 year-1. Significant increases were also observed in the biomass-C content and in the rate of fluorescein diacetate hydrolysis. Significant correlations among changes in biomass-C content and the rate of fluorescein diacetate hydrolysis and the changes in all enzymes tested were found. Two activity indices were calculated; a biological index of fertility and an enzyme activity number. No correlations were found between the biological index of fertility and the changes in the various enzyme activities. However, significant correlations were found either between enzyme activity number and most of the changes in enzyme activity, or between the enzyme activity number index and the biomass-C content (r=0.850). The use of a new activity index, the hydrolysis coefficient, is proposed. This coefficient was significantly correlated with biomass-C content (r=0.925) and with the enzyme activity number index (r=0.780).

Mineralization of monosubstituted aromatic compounds in unsaturated and saturated subsurface soils

The mineralization of benzoic acid, phenol, and benzylamine was determined as a function of depth in two 20-m sandy soil profiles, one of which was adjacent to a leach field receiving wastewater from a laundromat. Soil samples were collected aseptically, adjusted to 20–25% water content and amended with a trace level (50 ng/g soil) of the 14C-ring-labeled compounds. Evolution of CO2 was followed with time. First-order rate constants and the extents of mineralization were estimated from the resulting data by nonlinear regression. All three compounds were mineralized in every sample examined without a lag period. In general, phenol was mineralized more rapidly than benzoic acid, which was more rapidly mineralized than benzylamine. Benzylamine had the highest sorption coefficient; phenol had the lowest. Average half-life was 0.56 days for phenol, 0.84 days for benzoic acid, and 1.31 days for benzylamine. Mineralization rates did not correlate with bacterial number, fluorescein diacetate hydrolysis rate, or any soil characteristic. The ultimate percentage of all three compounds mineralized was lowest in the upper 3 m of both soil profiles. The total amounts of phenol and benzoic acid mineralized negatively correlated with cation-exchange capacity and silt content. Statistical analysis (2-level nested ANOVA) revealed that only the rate of phenol mineralization varied significantly as a function of soil profile, but rates for all three compounds varied significantly as a function of depth within a profile.

Microbial Biomass, Activity, and Community Structure in Subsurface Soils

ABSTRACTMicrobial biomass, community structure and activity were determined in the subsurface horizons of four contrasting soil types common to Alabama. Biomass and community structure were determined by analyzing the fatty acids of the extractable phospholipids. Activity was estimated by measuring the rate of enzymatic hydrolysis of fluorescein diacetate (FDA). In all four soils, biomass and activity declined with increasing depth; however, the magnitude and pattern of this decline varied as a function of soil type. Biomass concentrations in the lower Ap horizon ranged from 8.2 to 18.0 nmoles phospholipid/g dry wt soil. In the deepest subsoil horizons, the range was 0.0085 to 0.059 nmoles phospholipid/g dry wt soil. The rate of FDA hydrolysis was highly correlated with biomass (r=0.90). Polyenoic fatty acids, which are present only in cukaryotic microorganisms, were found in all horizons; however, their relative abundance differed as a function of soil type. Stepwise regression analysis revealed that soil characteristics could explain 89 and 82% of the variation in biomass and activity, respectively. The results indicated that the vertical distribution of microorganisms in a soil profile differs greatly as a function of soil type. Hence, soil type may be an important determinant as to whether potential ground‐water pollutants are biodegraded as they pass through the unsaturated zone of a soil profile.