Amount Of Available Substrate Research Articles

Will root-associated fungi affect enzyme activity in the root-detritusphere?

Root-associated fungal groups play a key role in plant productivity and belowground processes. However, how root-associated fungi will affect rhizosphere processes after the death of root still remain unknown. We applied soil zymography to visualize the spatio-temporal distributions of enzyme activities involved in root decomposition processes of European Spruce (Picea abies) between rhizosphere (living root) and detritusphere (7, 14, and 28 days after shoot cutting), and evaluated the effects of different root associated functional fungal groups (ectomycorrhizal fungi: EcMF; non-mycorrhizal rhizosphere fungi: NMRF; a mixture of EcMF and NMRF: Mix) on microbial growth rate and enzyme functions. In the root-detritusphere, the amount of available substrate released by dead root was increased, which stimulated microbial growth and enzyme activity. This was supported by larger hotspots area and broader extension of C-, N-, and P-enzyme activity (1.3–12.8 times) compared to rhizosphere (at day 0 after shoot cutting). This further shifted microorganisms from K-strategies in the rhizosphere to r-strategies in the detritusphere. Since NMRF benefited from the newly available resources as well as from the decreased competition with EcMF after root dead, enzyme activities were higher under a mixture of EcMF and NMRF than that under bare root or individual fungi alone. Furthermore, plants inoculated with EcMF increased the secretion of enzymes after shooting cutting, which may be explained by that the C and nutrients remaining in the root support the growth of EcMF to searching for new nutrients in the short-term. Overall, turnover of fungal biomass in detritusphere and soil represents an important process in the environment.

Apolipoprotein C-II mimetic peptide is an efficient activator of lipoprotein lipase in human plasma as studied by a calorimetric approach

Elevated plasma triglyceride (TG) levels are associated with higher risk of atherosclerotic cardiovascular disease. One way to reduce plasma TG is to increase the activity of lipoprotein lipase (LPL), the rate limiting enzyme in plasma TG metabolism. An apolipoprotein (apo) C-II mimetic peptide (18A–CII–a) has been recently developed that stimulated LPL activity in vitro and decreased plasma TG concentration in animal models for hypertriglyceridemia. Since this peptide can serve as a new therapeutic approach for treatment of hypertriglyceridemia, we investigated how 18A–CII–a peptide influences LPL activity in human plasma. We used recently described isothermal titration calorimetry based approach to assess the peptide, which enables the analysis in nearly undiluted human plasma. The 18A–CII–a peptide was 3.5-fold more efficient in stimulating LPL activity than full-length apoC-II in plasma sample from normolipidemic individual. Furthermore, 18A–CII–a also increased LPL activity in hypertriglyceridemic plasma samples. Unlike apoC-II, high concentrations of the 18A–CII–a peptide did not inhibit LPL activity. The increase in LPL activity after addition of 18A–CII–a or apoC-II to plasma was due to the increase of the amount of available substrate for LPL. Measurements with isolated lipoproteins revealed that the relative activation effects of 18A–CII–a and apoC-II on LPL activity were greater in smaller size lipoprotein fractions, such as remnant lipoproteins, low-density lipoproteins and high-density lipoproteins. In summary, this report describes a novel mechanism of action for stimulation of LPL activity by apoC-II mimetic peptides.

Modeling of fungal mycelium growth by fourth-class continuous stochastic cellular automaton with continuously defined growth conditions

The aim of this work was to simulate the growth and spatial structure of the fungal mycelium using a cellular automaton based on the synthesis of various model approaches. The spatial structure of the mycelium is described in the structural submodel of the cellular automaton, which determines the growth rate in the direction of larger resource amount and the number of branches of the mycelium per area unit. The amount of available substrate determines the probability of unidirectional apical growth. Another, biochemical part of the model allows us to describe the rate of transport of resources into the cell, their transport within the mycelium, and also their excretion, and is intended to describe the vertical and horizontal migration in the soil of two nutrients. The proposed model makes it possible to quantitatively describe such a feature of fungal colony growth as more active absorption of resources by external cells, compared to central ones due to separation of transport resources into active and passive resources. The active transport was described using the Michaelis-Menten kinetics. We were able to simulate the stockpiling of surplus resources and their redistribution over the mycelium after the exhaustion of reserves in the external environment, and also to simulate typical growth patterns of mycelial colonies that were observed in experiments published in the literature.

Changes in consortial links of aphyllophoroid fungi and Quercus robur L. in the recreational forests of the green zone of city

Recreational degradation of forest ecosystems of the green zone of the town Uman was described on the example of the forest array «Belogrudivska Dacha». The vitality and health conditions of Quercus robur L. and species, systematic, trophic, spatial compositions of xylotrophic fungi were investigated. Changes in the compositions of xylotrophic fungi and Q. robur were indicated an intensification of degradation processes in fresh maple oak. However, the entwinement between the development and distribution of xylotrophic fungi with the degree of damage and drying of trees, the intensity of recreational load did not found. This effect was indirect. The consorts links of Q. robur and xylotrophic fungi essentially depend on the amount of available substrate and evaporation from the soil surface, density of canopy, the projective coverage of herb stratum, in general, the forestry and mensurational characteristics of the stands. These components determine the development of forest ecosystems, the formation of myco-horizons of trees, the rate of accumulation of wood of various categories of substrates, which favorable for the settlement and development of xylotrophic fungi, certain levels of organization of consorts. The deterioration of the conditions of growth and development of Q. robur in fresh maple oak, drying and degradation of canopy cause changes in the composition of the consorts of these trees and xylotrophic fungi due to violation of the conditions of the forest environment, changes in the quantitative and qualitative characteristics of the substrates, their distribution in time and space. Recreational impact was essentially neutralized due to the complex composition and large buffer capacity of the forest ecosystem, a large number of mechanisms for its sustainability, and the ability to quickly restore degraded elements and links of the forest. Highly productive young and medieval medium-attractive woodlands of Q. robur of recreational forests of the woodland part of the green zone of city Uman, affected a moderate and medium recreational impact. The territory of the tract has the first (75 %) and second (25 %) stage of recreational degradation. This was primarily due to the close location of the city, suburban villages, main transport networks and the availability of forest for the population. Species diversity of investigated fungi in all experimental plots acquired rather high values. Such indicators testified to the stability of xylomycocenosis to the existing recreational impact, unlike other, more vulnerable structural and functional components of the forest ecosystem: herb stratum, underbrush, undergrowth, soil surface. At all studied experimental plots of the tract, the best development of xylomycobiota was in the trees of the highest Kraft classes. According to the state categories in the investigated plots, weakened and strongly weakened trees were prevailed, in which the maximum number of species and findings of fungi was detected. The findings of xylotrophic fungi on the recently dead stands was minimal. The analysis of the vegetation under ombraregime has shown that subaridophytes and subomorophytes were predominated. In the medium- and low-transformed experimental plots, the magnitude of the ecological amplitude under ombraregime is slightly higher than that of the highly transformated experimental plot. This indicates a greater evaporation from the surface of the soil with an increase in the degree of recreational transformation. A significant change in the forest environment and substratum fund due to the intense degradation of the ecosystem may limit the development and spread of xylotrophic fungi.

Synergistic effects of anaerobic digestion from sewage sludge with lime mud

Waste reuse and renewable energy generation are encouraged in many countries. Anaerobic digestion of sewage sludge is usually limited by the slow hydrolysis rate of the sludge. To resolve the problem the lime mud was used in this biomethane production. Batch tests were performed at 55 °C with lime mud concentrations ranging from 1.25 to 5.00 g/L. The results showed that the highest methane yield per gram of volatile solid and volatile solid reduction were 146 ml and 42.4% at lime mud concentration of 2.50 g/L, which were 1.77 and 3.01 times higher than that of the control tests without lime mud, respectively. However, high levels of lime mud reduced the amount of available substrate and inhibited the anaerobes, thereby decreasing the methane production. The modified Gompertz model showed a better fit for the results than the first-order model. It was also found that the eco-friendly treatment of two types of solid waste had the potential to synergistically contribute to waste reuse and energy recovery.

Occurrence Patterns of Lichens on Stumps in Young Managed Forests

The increasing demand for forest-derived bio-fuel may decrease the amount of dead wood and hence also the amount of available substrate for saproxylic ( = dead-wood dependent) organisms. Cut stumps constitute a large portion of dead wood in managed boreal forests. The lichen flora of such stumps has received little interest. Therefore, we investigated which lichens that occur on stumps in young (4–19 years), managed forests and analyzed how species richness and occurrence of individual species were related to stump and stand characteristics. We performed lichen inventories of 576 Norway spruce stumps in 48 forest stands in two study areas in Central Sweden, recording in total 77 lichen species. Of these, 14 were obligately lignicolous, while the remaining were generalists that also grow on bark, soil or rocks. We tested the effect of characteristics reflecting successional stage, microclimate, substrate patch size, and the species pool in the surrounding area on (1) total lichen species richness, (2) species richness of obligately lignicolous lichens and (3) the occurrence of four obligately lignicolous lichen species. The most important variables were stump age, with more species on old stumps, and study area, with similar total species richness but differences in occupancy for individual species. Responses for total lichen species richness and species richness of obligately lignicolous lichens were overall similar, indicating similar ecological requirements of these two groups. Our results indicate that species richness measurements serve as poor proxies for the responses of individual, obligately lignicolous lichen species.

The relationship of water-soluble carbon and hot-water-soluble carbon with soil respiration in agricultural fields

Abstract Factors controlling soil respiration (RS) are of great interest because RS plays a critical role in determining global atmospheric carbon dioxide (CO2) concentrations. Substrate availability is one of the most important factors controlling RS. Soil microorganisms consume various substrates ranging from simple sugars supplied by aboveground photosynthesis to complex humic acids in soil organic matter; however, substrate decomposition rates depend on substrate availability. Thus, RS is partly determined by the amount and quality of available substrate. However, accurate quantification of the amount of available substrate is difficult because soil microorganisms utilize carbon (C) substrates of varying quality for RS. Water-soluble C (WSC), hot-water-soluble C (HWSC), and microbial biomass C are known as indicators of the amount of available soil C substrate. We continuously measured RS in two contrasting soils, Andosol and Fluvisol, during the cultivation of soybean and brassica crops with a 6-month fallow period between them. The total annual RS in Andosol and Fluvisol were 376 ± 23 and 408 ± 49 g CO2-C m−2, respectively, with no significant difference between them. WSC and HWSC were measured every month during RS measurement. During the soybean growth period, RS and WSC were correlated, and soil type did not affect RS. During the fallow period, RS, HWSC and microbial biomass C in Fluvisol were higher than those in Andosol, despite the total soil C in Andosol being higher than that in Fluvisol. RS during brassica crop growth was not correlated with any of the measured substrate indicators. We therefore concluded that the relationships among the measures of available substrates and RS at the field level could provide vital information on seasonal changes in the interaction between the effects of soil type and plants on RS, thereby leading to a better understanding of belowground C dynamics.

Model‐based evaluation of microbial mass fractions: effect of absolute anaerobic reaction time on microbial mass fractions

Although enhanced biological phosphorus removal processes (EBPR) are popular methods for nutrient control, unstable treatment performances of full‐scale systems are still not well understood. In this study, the interaction between electron acceptors present at the start of the anaerobic phase of an EBPR system and the amount of organic acids generated from simple substrate (rbsCOD) was investigated in a full‐scale wastewater treatment plant. Quantification of microbial groups including phosphorus‐accumulating microorganisms (PAOs), denitrifying PAOs (DPAOs), glycogen‐accumulating microorganisms (GAOs) and ordinary heterotrophic microorganisms (OHOs) was based on a modified dynamic model. The intracellular phosphorus content of PAOs was also determined by the execution of mass balances for the biological stages of the plant. The EBPR activities observed in the plant and in batch tests (under idealized conditions) were compared with each other statistically as well. Modelling efforts indicated that the use of absolute anaerobic reaction (ηı) instead of nominal anaerobic reaction time (η), to estimate the amount of available substrate for PAOs, significantly improved model accuracy. Another interesting result of the study was the differences in EBPR characteristics observed in idealized and real conditions.

Variation in oral volatile sulphur compound formation

It has been suggested that the level of orally produced volatile sulphur compounds (VSCs) can be of use when monitoring oral malodour or in determining patients at risk of periodontal disease in longitudinal studies. It is not known, however, to what extent the level of VSC in mouth air is a stable, individual characteristic over time. Aim: The hypothesis to be tested was that the level of VSC in mouth air is an individual trait that is stable over time. Methods: Two groups of dental students participated in the study (n = 30 and n = 11). The amount of available substrate for VSC formation was standardized by rinses with 6 mM aqueous solutions of cysteine (pH 7.2). Part 1 used a Halimeter® to measure 'morning breath' and response to cysteine rinses. Part 2 measured response to cysteine rinsing using a gas chromatograph. Repeated measurements provided information concerning the longitudinal intra-individual variations in level of oral VSC formation. Results: Both groups showed large intra-individual variations in oral VSC. The differences were enhanced by cysteine rinses. Conclusion: The hypothesis was not supported. Oral VSC levels cannot be taken as diagnostic criteria in a normal population because of marked intra-individual variations over time.

Nonlinearity in the growth of bacterial colonies: conditions and causes

The universally recognized kinetic model of colony growth, introduced by Pirt, predicts a linear increase of colony size. The linearity follows from the assumption that the colony expands through the growth of only such cells that are located immediately behind the moving colony front, in the so-called peripheral zone of constant width and density. In this work, Pirt's model was tested on two bacteria--Alcaligenes sp. and Pseudomonas fluorescens--having markedly distinct cultural properties and grown on agarized medium with pyruvate. The colony size dynamics was followed for different densities of the inoculum, ranging from a single cell to a microdroplet of bacterial suspension (10(5)-10(6) cells), and for different depths of the agar layer, determining the amount of available substrate. A linear growth mode was observed only with P. fluorescens and only in the case of growth from a microdroplet. When originating from a single cell, colonies of both organisms displayed nonlinear growth with a distinct peak of Kr (the rate of colony radius increase) occurring after 2-3 days of growth. The growth of P. fluorescens colonies showed virtually no dependence on the depth of the agarized medium, whereas the rate of colony size increase of Alcaligenes sp. turned out to be directly related to the medium layer thickness. The departure from linearity is consistently explained by a new kinetic chart stipulating a possible contribution to the colony growth not only of peripheral cells but also (much more distinct in Alcaligenes) of cells at the colony center. The colony growth dynamics is determined not only by the concentration of the limiting substrate but also by the amount of autoinhibitor, the synthesis of which is governed by age of cells. The distinctions of growth from a single cell and microdroplet could also originate as a result of dissociation into the R- and S-forms and competition between the corresponding subpopulations for oxygen and the common substrate.

Longitudinal changes in body composition and energy balance in lean women with normal and abnormal glucose tolerance during pregnancy

OBJECTIVE: The objective of this study was to evaluate the longitudinal changes in energy expenditure and body composition in relationship to alterations in carbohydrate metabolism in women with normal and abnormal glucose metabolism. We hypothesized that women with decreased insulin sensitivity before conception would have less fat accretion and smaller increases in energy expenditure. STUDY DESIGN: Six women with normal glucose tolerance and 10 women with abnormal glucose tolerance were evaluated before conception, and in early (12 to 14 weeks) and late (34 to 36 weeks) gestation. Body composition was estimated by hydrodensitometry, resting energy expenditure, and glucose and fat metabolism by indirect calorimetry, endogenous glucose production by infusion of [6-6 2H.. 2] glucose, and insulin sensitivity using a hyperinsulinemic-euglycemic clamp (40 mU/m 2/min). RESULTS: There was a smaller increase in fat mass (1.3 kg [ P = .04]) in early pregnancy in women with abnormal glucose tolerance before pregnancy. Indirect calorimetry measured gestational age–related increases in basal oxygen utilization, with or without correction for fat-free mass (v̇ o 2, P = .002), resting energy expenditure (expressed in kilocalories, P = .0001), and carbohydrate oxidation ( P = .0003). The insulin-mediated elevation in v̇ o 2 increased in later gestation v̇ o 2 ( P = .005), as did resting energy expenditure ( P = .0001) and fat oxidation ( P = 0.0001). However, there was a decrease in respiratory quotient ( P = .0001), carbohydrate oxidation ( P = .002), and nonoxidative carbohydrate metabolism ( P = .0001) with advancing gestation during insulin infusion. In early pregnancy, changes in fat mass correlated inversely with changes in insulin sensitivity ( r = –0.52, P = .04) and changes in basal v̇ o 2 correlated inversely with decreases in basal endogenous glucose production ( r = –0.74, P = .01). CONCLUSION: In early gestation, the changes in maternal fat mass and basal oxygen consumption are inversely related to the changes in insulin sensitivity. This response in lean women with decreased insulin sensitivity before conception may have survival value by providing a larger amount of available substrate to meet fetoplacental needs during gestation. (Am J Obstet Gynecol 1998;179:156-65.)

Nitrogen Loss and Denitrification as Studied in Relation to Reductions in Nitrogen Loading in a Shallow, Hypertrophic Lake (Lake Søbygård, Denmark)

AbstractA detailed mass balance on nitrogen was carried out in shallow and hypertrophic Lake Søbygård during 4.5 years before through 2.5 years after a 36 % reduction in nitrogen loading. Annual mean loss rate of nitrogen was 159–229 mg N m−2 d−1 before the loading reduction and 125 mg N m−2 d−1 after. In spite of a short hydraulic retention time (18–27 days) the proportion of nitrogen loading lost in the lake was high (38–53 %) and not affected by changes in loading. Calculated denitrification accounted for 86–93% of the loss rate, while 7–14% was permanently buried. Marked seasonal variations in the loss percentage were found during the season, ranging from 23 % in first quarter to 65 % in third quarter. The seasonal variation in the loss percentage of nitrogen showed a hysteresis like relationship to temperature, with a high percentage in fourth quarter. This suggests that the amount of available substrate, which mainly consists of sedimentated phytoplankton, accumulated during summer, is an important regulating factor. The ability of various published input‐output models to predict the observed changes in in‐lake nitrogen concentration in Lake Søbygård was tested. This study has further confirmed that small lakes with short retention and high nitrogen loading may significantly reduce the nitrogen loading of downstream aquatic environments.

The influence of the carbohydrate fraction and additives on silage quality

AbstractRespiration losses, effect of sugar content, formic acid addition and inoculation were evaluated in relation to initial fermentation and silage quality in three experiments. Changes in the content of fermentable substrate during post–harvest respiration and initial fermentation were studied in the laboratory. Soluble carbohydrates were estimated as glucose, fructose, sucrose, fructans and starch by an enzymatic method.About 70% of the sugars remained after 30 h of conventional wilting, as opposed to less than 50% in a chopped sample kept in the dark. During the first days of fermentation the metabolic activity was very intensive. Sugars, which accounted for 10% of the dry matter, were fermented within 4 d. There were indications, mainly in clover silages, that substances other than water‐soluble carbohydrates were used as energy sources.Low‐sugar crops were obtained by shading the fields. After 3 d the sugar in the grass had decreased to half of the original content. This effect was less pronounced in clover. The amount of available substrate and dry matter (DM) content had a major influence on silage quality. In an unwilted crop at least 25 g of water‐soluble carbohydrate was needed per kg of fresh material to obtain an acceptable silage quality in the controls, while 20 g was sufficient in inoculated silage. Formic acid addition makes the fermentation less sensitive to water–soluble carbohydrate content. Inoculation of willed silage increased lactic acid production and decreased the pH. There was also less variation in silage quality.

Effect of Oxygen and carbon Diozide Concentrations on Gross Dark CO2 Fixation and Dark Respiration in Bryophyllim diagremontiaum

Effects of O2 and CO2 concentrations on the rates of net and gross dark CO2 fixation in B. daigremontianum were examined. Raising [CO2]i from 60 to 420 �ll-� resulted in a decrease in the rate of dark respiration, increase in the rate of gross dark fixation (GDF) and shortened the time taken to reach maximum rate of GDF. However, cumulative GDF was relatively unaffected by [CO2]i at that range. At 14�C, lowering [O2] from 21 to 1.5 % had little effect on the rates and time course of dark respiration and GDF. However, at 24�C, this caused a drop in the rate of dark respiration, changed the time dependence of GDF and slightly increased cumulative GDF. Consequently, at 24�C cumulative net CO2 uptake was 3 .3 times higher at 1 .5 % versus 21% O2. These data are discussed in view of the suggested hypothesis that the amount of available substrate, at the end of the light period, is a principal component of the regulation of the amount of gross dark fixation and dark respiration in the following dark period.

Respiration in cell development.

Dark oxygen uptake was measured manometrically for cells of green high-temperature alga, Chlorella 7-11-05, separated from nonsynchronized populations by centrifugation into fractions of predominantly small or large cells. In the presence of exogenous glucose, respiration activity of the smaller (younger) cell fraction was invariably higher than that of the larger (older) cell fraction. In the absence of exogenous substrate, the difference in respiration rates in two fractions of cells was inconsistent from one experiment to another both in size and in sign. The dependence of dark respiration on the amount of available substrate makes the endogenous respiration rate unsuitable as an indicator of the inherent capacity of respiratory mechanisms. In observations on synchronized heterotrophically grown cells, the glucose respiration rate expressed per dry weight of cells gradually declined over the developmental period irrespective of the adequate exogenous supply of glucose or illumination by weak light. Observations on synchronized heterotrophically grown Chlorella cells thus corroborated studies of glucose respiration in cells separated into are groups by centrifugation. The decline in metabolic activity in the course of cell development previously established for growth and photosynthesis extends to include respiration activity. Disagreements among several investigators in regard to the course of respiration during cell development are probably due to the effects of accessory factors such as strong light during the preceding growth period or the scarcity of respiratory substrate during respiration measurements which affect and distort changes in the inherent capacity of metabolic mechanisms in the course of cell development.