High Nutrient Conditions Research Articles

Taurine Improves Lipid Metabolism and Skeletal Muscle Sensitivity to Insulin in Rats Fed with High Sugar and High Fat Diet.

Metabolic syndrome is a lifestyle-related disease caused by high nutrient condition and lack of exercise. The insulin resistance due to obesity has attracted attention as an underlying mechanism of metabolic syndrome. Insulin resistance refers to reduced insulin sensitivity in insulin target tissues. In this case, in order to maintain normal blood glucose levels, a compensatory large amount of insulin is released, leading to the occurrence of hyperinsulinemia. Taurine is widely distributed in animal tissues. Although it is not involved in protein synthesis, taurine plays an important role in maintaining the body's physiological function. In this experiment, insulin resistance model was induced by high fat and high sugar diet. Two percent taurine was added in drinking water to explore the mechanism of taurine in insulin resistance and to provide theoretical basis for using taurine to improve insulin resistance. The result showed that high-fat and high-sugar diet could decrease insulin sensitivity, and taurine could improve it by oral glucose tolerance test. Moreover, serum TG, TC were higher, while HDL-C in rats fed with high sugar and high fat diet was lower than normal rats, the changes of which can be significantly relieved by 2% taurine administration. mRNA and protein expressions of IRS1, and GLUT4 which were significantly changed by high sugar and high fat diet can also be regulated by 2% taurine. The results indicated that taurine can improve insulin sensitivity through remediating lipid metabolism disorder and regulating the expressions of IRS and GLUT4.

N:P ratio influences the competition of Microcystis with its picophytoplankton counterparts, Mychonastes and Synechococcus, under nutrient enrichment conditions

We investigated how the N:P ratio can shape the structure of picophytoplankton and Microcystis, which are abundant and widespread in eutrophic lakes. Unialgal culture and coculture batch experiments were conducted to study the growth and interspecific competition of Microcystis and two freshwater picophytoplankton species, Mychonastes and Synechococcus, with varying N:P ratios. The results showed that the Ks values of Mychonastes and Synechococcus were more than two times smaller than those of Microcystis, and their μmax values were much higher than those of Microcystis due to their small size. Our results also revealed that the N:P ratio is important for shaping phytoplankton community structure even under high nutrient conditions. The optimal N:P ratios are 64, 32, and 32 for Mychonastes, Microcystis, and Synechococcus, respectively. Thus, Mychonastes outcompeted Microcystis when the N:P ratio was higher than 64, while Microcystis and Synechococcus grew equally well under all of the N:P ratio levels, since they have the same optimal N:P ratio.

Context-Dependent Parental Effects on Clonal Offspring Performance.

Parental environments may potentially affect offspring fitness, and the expression of such parental effects may depend on offspring environments and on whether one considers an individual offspring or all offspring of a parent. Using a well-studied clonal herb, Alternanthera philoxeroides, we first grew parent plants in high and low soil-nutrient conditions and obtained 1st generation clonal offspring from these two environments. Then we grew offspring of these two types of 1st generation clonal offspring also in high and low nutrient conditions. We measured and analyzed mean performance and summed performance of the four types of 2nd generation clonal offspring. High nutrient availability of parental environments markedly increased both mean performance (i.e., the average fitness measure across all individual offspring produced by a parent) and summed performance (i.e., the sum of the fitness measure of all offspring produced by a parent) of the 2nd generation clonal offspring. The positive parental effects on summed performance of the 2nd generation clonal offspring were stronger when the 1st generation clonal offspring grew in the high instead of the low nutrient conditions, but the positive parental effects on their mean performance did not depend on the nutrient environments of the 1st generation clonal offspring. The results provide novel evidence that parental environmental effects persist across vegetative generations and strongly depend on offspring environments and levels of plants.

Plasma-membrane electrical responses to salt and osmotic gradients contradict radiotracer kinetics, and reveal Na+-transport dynamics in rice (Oryza sativa L.).

A systematic analysis of NaCl-dependent, plasma-membrane depolarization (∆∆Ψ) in rice roots calls into question the current leading model of rapid membrane cycling of Na+ under salt stress. To investigate the character and mechanisms of Na+ influx into roots, Na+-dependent changes in plasma-membrane electrical potentials (∆∆Ψ) were measured in root cells of intact rice (Oryza sativa L., cv. Pokkali) seedlings. As external sodium concentrations ([Na+]ext) were increased in a step gradient from 0 to 100mM, membrane potentials depolarized in a saturable manner, fitting a Michaelis-Menten model and contradicting the linear (non-saturating) models developed from radiotracer studies. Clear differences in saturation patterns were found between plants grown under low- and high-nutrient (LN and HN) conditions, with LN plants showing greater depolarization and higher affinity for Na+ (i.e., higher Vmax and lower Km) than HN plants. In addition, counterion effects on ∆∆Ψ were pronounced in LN plants (with ∆∆Ψ decreasing in the order: Cl- > SO42- > HPO 4 2- ), but not seen in HN plants. When effects of osmotic strength, Cl- influx, K+ efflux, and H+-ATPase activity on ∆∆Ψ were accounted for, resultant Km and Vmax values suggested that a single, dominant Na+-transport mechanism was operating under each nutritional condition, with Km values of 1.2 and 16mM for LN and HN plants, respectively. Comparing saturating patterns of depolarization to linear patterns of 24Na+ radiotracer influx leads to the conclusion that electrophysiological and tracer methods do not report the same phenomena and that the current model of rapid transmembrane sodium cycling may require revision.

Simulated microgravity and the antagonistic influence of strigolactone on plant nutrient uptake in low nutrient conditions

Human-assisted space exploration will require efficient methods of food production. Large-scale farming in presence of an Earth-like atmosphere in space faces two main challenges: plant yield in microgravity and plant nutrition in extraterrestrial soils, which are likely low in nutrients compared to terrestrial farm lands. We propose a plant-fungal symbiosis (i.e. mycorrhiza) as an efficient tool to increase plant biomass production in extraterrestrial environments. We tested the mycorrhization of Solanaceae on the model plant Petunia hybrida using the arbuscular mycorrhizal fungus Rhizophagus irregularis under simulated microgravity (s0-g) conditions obtained through a 3-D random positioning machine. Our results show that s0-g negatively affects mycorrhization and plant phosphate uptake by inhibiting hyphal elongation and secondary branching. However, in low nutrient conditions, the mycorrhiza can still support plant biomass production in s0-g when colonized plants have increased SL root exudation. Alternatively, s0-g in high nutrient conditions boosts tissue-specific cell division and cell expansion and overall plant size in Petunia, which has been reported for other plants species. Finally, we show that the SL mimic molecule rac-GR24 can still induce hyphal branching in vitro under simulated microgravity. Based on these results, we propose that in nutrient limited conditions strigolactone root exudation can challenge the negative microgravity effects on mycorrhization and therefore might play an important role in increasing the efficiency of future space farming.

Evaluation of estuarine biotic indices to assess macro-benthic structure and functioning following nutrient remediation actions: A case study on the Eden estuary Scotland

Despite a wealth of methods currently proposed by the European Water Framework Directive (WFD) to assess macro-benthic integrity, determining good ecological status (GES) and assessing ecosystem recovery following anthropogenic degradation is still one of the biggest challenges in marine ecology research. In this study, our aim was to test a number of commonly used structural (e.g. Shannon–Wiener, Average Taxonomic Diversity (Δ), M-AMBI) and functional indicators (e.g. BTA, BPc) currently used in benthic research and monitoring programmes on the Eden estuary (Scotland). Historically the estuary has a legacy of high nutrient conditions and was designated as a Nitrate Vulnerable Zone (NVZ) in 2003, whence major management measures were implemented in order to ameliorate the risk of eutrophication symptoms. We therefore collected data on intertidal macro-benthic communities over a sixteen year interval, covering a pre-management (1999) and post-management (2015) period to assess the effectiveness of the intended restoration efforts. In the post-management period, the results suggested an improvement in the structure and functioning of the estuary as a whole, but macro-benthic assemblages responded to restoration variably along the estuarine gradient. The greatest improvements were noticed in the upper and central sites of the estuary with functional traits analysis suggesting an increased ability of these sites to provide ecosystem services associated with the benthic environment such as carbon and organic matter cycling. Generally, almost all of the structural and functional indicators detected the prevailing environmental conditions (with the exception of (Pielou’s index and Average Taxonomic Diversity (Δ)), highlighting the appropriateness of such methods to be used in monitoring the recovery of transitional systems. This research also provides a robust baseline to monitor further management actions in the Eden estuary and provides evidence that notable reductions in nitrate concentrations resulting from NVZ designations may result in significant improvements to benthic structure and functioning.

Nutrient addition increases the capacity for division of labor and the benefits of clonal integration in an invasive plant

Many of the most invasive plants are clonal, and clonal integration has been proposed as an important mechanism promoting invasiveness. When the availabilities of two essential resources are negatively correlated in space, clonal integration may benefit clonal plants through division of labor. We hypothesized that environments with reciprocal patchiness of light and soil water may induce division of labor, and nutrient addition may increase both the division of labor and the benefits of clonal integration. To test this, we grew pairs of connected and disconnected ramets of the clonal invader Mikania micrantha under negative spatial covariance of light and soil water such that the proximal ramets were grown under high light and low soil water conditions and the distal ramets were grown under low light and high soil water conditions. In half of the ramet pairs, both ramets of a pair received a nutrient addition treatment. The results showed that connection decreased the root to shoot ratio in proximal ramets and increased it in distal ramets, indicating that division of labor was induced. In addition, connection increased the root to shoot ratio of distal ramets more under high soil nutrient conditions than under low soil nutrient conditions, indicating that nutrient addition increased the division of labor. Connection increased plant biomass at the whole clonal fragment level, and this increase was larger under high soil nutrient conditions than under low soil nutrient conditions. This study showed, for the first time, that in environments with reciprocal patchiness of two essential resources, the capacity for division of labor and its influence on plant performance may depend on the availability of a third essential resource. Because invasive plants often can acquire a larger amount of soil resources than native plants, our study may also contribute to the understanding why clonality is related to invasiveness.

Nutrient pollution disrupts key ecosystem functions on coral reefs.

There is a long history of examining the impacts of nutrient pollution and pH on coral reefs. However, little is known about how these two stressors interact and influence coral reef ecosystem functioning. Using a six-week nutrient addition experiment, we measured the impact of elevated nitrate (NO-3) and phosphate (PO3-4) on net community calcification (NCC) and net community production (NCP) rates of individual taxa and combined reef communities. Our study had four major outcomes: (i) NCC rates declined in response to nutrient addition in all substrate types, (ii) the mixed community switched from net calcification to net dissolution under medium and high nutrient conditions, (iii) nutrients augmented pH variability through modified photosynthesis and respiration rates, and (iv) nutrients disrupted the relationship between NCC and aragonite saturation state documented in ambient conditions. These results indicate that the negative effect of NO-3 and PO3-4 addition on reef calcification is likely both a direct physiological response to nutrients and also an indirect response to a shifting pH environment from altered NCP rates. Here, we show that nutrient pollution could make reefs more vulnerable to global changes associated with ocean acidification and accelerate the predicted shift from net accretion to net erosion.

Effects of nutrient addition and clipping on biomass production of invasive and native annual Asteraceae plants

SummaryInvasive plants dominate many habitats and cause significant harm to native plants, agriculture and the wider environment. Clipping by mowing machines has been a common method to control invasive plants, but whether it can reduce the performance of invaders and increase the performance of co‐occurring natives is not known. This study examined the effects of soil nutrient conditions and clipping on the performance of three invasive and three co‐occurring native annual Asteraceae plants under either isolated or competitive conditions. Clipping tended to reduce the aboveground biomass of the invasive plants more than that of the native plants under low, but not under high nutrient conditions. However, invasive plants still produced an aboveground biomass equal to, or larger than, that of native plants under the low nutrient and clipping treatment combination. Nutrient addition increased the aboveground biomass of the invasive plants more than that of the native plants, although this was only marginally significant under competitive conditions. Clipping did not reduce the performance advantage of invaders over natives under high soil nutrient conditions. The ability of invaders to benefit more from nutrient addition, along with its ability to perform equally well, or better than, the native plants after human mechanical control (i.e. clipping), may explain their high abundance and dominance in many habitats.

Acceleration or deceleration of litter decomposition by herbivory depends on nutrient availability through intraspecific differences in induced plant resistance traits

Abstract Herbivores often induce changes in plant defensive chemistry or nutrient content that may respectively inhibit or promote microbial decomposition of senesced litter. Often the directional impact of herbivores on decomposition is considered to be a property of a species or ecosystem. While rarely explored, plasticity in the induction of defensive strategies across environmental gradients may also result in divergent impacts of herbivores on decomposition (deceleration vs. acceleration). Here, we examined how soil nutrient conditions determine legacy effects of herbivory, using nine goldenrod genotypes grown across four levels of nutrient supply and with or without grasshopper herbivory. In this species, herbivory induces defensive traits in genotypes grown in high nutrient conditions but induces tolerance (compensatory growth) in low nutrient conditions. We combined senesced litter from each treatment with a common soil inoculum in microcosms and measured soil respiration and litter mass loss over 100 days as estimates of decomposition. Plant genotype, nutrient environment, and herbivory each altered decomposition. The legacy effect of herbivory overwhelmed the positive effect of high soil nutrient supply on decomposition. This significant herbivory × nutrient environment interaction meant that herbivore‐induced plants grown in high nutrient environments produced litter that was more resistant to microbial breakdown than litter from the same genotype not exposed to herbivores. But the opposite occurred at low nutrient levels where litter from herbivore‐induced plants was most readily decomposed. Furthermore, we mechanistically tie treatment‐induced changes in leaf traits to decomposition rates. Lastly, we demonstrate a significant correlation between herbivore growth rates on living tissue and decomposition efficiency by the microbial community of senesced tissue, suggesting that herbivores and microbes perceive the “quality” of the induced substrate similarly. Synthesis. Herbivore‐induced changes in leaf palatability and trait expression due to defense induction or compensatory growth can cascade through to either inhibit or promote the decomposability of leaf litter within a single species. Here, the key determinant of which occurs is the soil fertility environment of the goldenrod clone. These findings offer mechanistic understanding of how spatial heterogeneity in ecosystem process rates may be generated by spatial variation in herbivory and nutrient availability.

Dynamics of size-fractionated phytoplankton biomass in a monsoonal estuary: Patterns and drivers for seasonal and spatial variability

Phytoplankton size-fractionated biomass is an important determinant of the type of food web functioning in aquatic ecosystems. Knowledge about the effect of seasonal salinity gradient on the size-fractionated biomass dynamics is still lacking, especially in tropical estuaries experiencing monsoon. The phytoplankton size-fractionated chlorophyll a biomass (>3 μm and <3 μm) and picophytoplankton community structure were characterized in the monsoonal Zuari estuary, along the west coast of India, from October 2010 to September 2011 across the salinity gradient (0–35). On an annual scale, >3 μm size-fraction was the major contributor to the total phytoplankton chlorophyll a biomass with the ephemeral dominance of <3 μm size-fraction. During monsoon season, freshwater runoff and shorter water residence time resulted in a size-independent response. The lowest annual chlorophyll a biomass concentration of both size-fractions showed signs of recovery with increasing salinity downstream towards the end of the monsoon season. In contrast, the chlorophyll a biomass response was size-dependent during the non-monsoon seasons with the sporadic dominance (>50%) of <3 μm chlorophyll a biomass during high water temperature episodes from downstream to middle estuary during pre-monsoon and at low salinity and high nutrient conditions upstream during post-monsoon. These conditions also influenced the picophytoplankton community structure with picoeukaryotes dominating during the pre-monsoon, phycoerythrin containing Synechococcus during the monsoon and phycocyanin containing Synechococcus during the post-monsoon. This study highlights switching over of dominance in size-fractionated phytoplankton chlorophyll a biomass at intra, inter-seasonal and spatial scales which will likely govern the estuarine trophodynamics.

Simultaneous increase in cellular content and volumetric concentration of lipids in Bracteacoccus bullatus cultivated at reduced nitrogen and phosphorus concentrations

Manipulation of the nutrient concentration is an inexpensive and efficient method for increasing lipid and TAG accumulation in algal cells. However, high volumetric production requires finding a proper balance between the decrease of biomass production and the increase in the total lipid content. We isolated a strain of green microalga Bracteacoccus bullatus and increased its lipid content from 17 to 59% of biomass dry weight by manipulating of nitrogen and phosphorus content in the medium. The 10-fold reduction of the nitrogen and phosphorus concentration in the medium was the most efficient method of the lipid induction compared to nutrient deplete and high nutrient conditions. The oleic (48–64% mass of total fatty acids) and linoleic (14–24% mass of total fatty acids) acids dominated in the fatty acid profile, thus making this strain a suitable candidate for biodiesel production.

Succession and toxicity of Microcystis and Anabaena (Dolichospermum) blooms are controlled by nutrient-dependent allelopathic interactions

Microcystis and Anabaena (Dolichospermum) are among the most toxic cyanobacterial genera and often succeed each other during harmful algal blooms. The role allelopathy plays in the succession of these genera is not fully understood. The allelopathic interactions of six strains of Microcystis and Anabaena under different nutrient conditions in co-culture and in culture-filtrate experiments were investigated. Microcystis strains significantly reduced the growth of Anabaena strains in mixed cultures with direct cell-to-cell contact and high nutrient levels. Cell-free filtrate from Microcystis cultures proved equally potent in suppressing the growth of nutrient replete Anabaena cultures while also significantly reducing anatoxin-a production. Allelopathic interactions between Microcystis and Anabaena were, however, partly dependent on ambient nutrient levels. Anabaena dominated under low N conditions and Microcystis dominated under nutrient replete and low P during which allelochemicals caused the complete suppression of nitrogen fixation by Anabaena and stimulated glutathione S-transferase activity. The microcystin content of Microcystis was lowered with decreasing N and the presence of Anabaena decreased it further under low P and high nutrient conditions. Collectively, these results indicate that strong allelopathic interactions between Microcystis and Anabaena are closely intertwined with the availability of nutrients and that allelopathy may contribute to the succession, nitrogen availability, and toxicity of cyanobacterial blooms.

Probiotics for Plants? Growth Promotion by the Entomopathogenic Fungus Beauveria bassiana Depends on Nutrient Availability.

Cultivation of crops requires nutrient supplements which are costly and impact the environment. Furthermore, global demands for increased crop production call for sustainable solutions to increase yield and utilize resources such as nutrients more effectively. Some entomopathogenic fungi are able to promote plant growth, but studies over such effects have been conducted under optimal conditions where nutrients are abundantly available. We studied the effects of Beauveria bassiana (strain GHA) seed treatment on the growth of maize (Zea mays) at high and low nutrient conditions during 6weeks in greenhouse. As expected, B. bassiana seed treatment increased plant growth, but only at high nutrient conditions. In contrast, the seed treatment did not benefit plant growth at low nutrient conditions where the fungus potentially constituted a sink and tended to reduce plant growth. The occurrence of endophytic B. bassiana in experimental plant tissues was evaluated by PCR after 6weeks, but B. bassiana was not documented in any of the above-ground plant tissues indicating that the fungus-plant interaction was independent of endophytic establishment. Our results suggest that B. bassiana seed treatment could be used as a growth promoter of maize when nutrients are abundantly available, while the fungus does not provide any growth benefits when nutrients are scarce.

Effect of Nutrient Loadings on the Regulation of Water Nitrogen and Phosphorus by Vallisneria natans and Its Photosynthetic Fluorescence Characteristics

Submerged macrophytes are an important component of aquatic ecosystems. During the growing period, submerged macrophytes can absorb nitrogen and phosphorus nutrients to reduce pollution loadings. Shoots of submerged macrophytes can also promote the adhesion of suspended substances in water, reducing the turbidity. The release of nutrients in sediments can be suppressed by its root system, and the resuspension of sediments caused by disturbance of winds and waves can also be resisted. The role of submerged macrophytes in ecological restoration of eutrophic lakes has attracted widespread attention. In 1960, the submerged plants Vallisneria natans and Potamogeton malaianus had been the dominant species in East Taihu. However after 2002, Nymphoides peltatum, Elodea nattalii, P. malaianus, etc. have gradually taken over the dominant roles along with significant elevations of nitrogen and phosphorus levels. Nutrients in water are not the only key factors causing eutrophication of water bodies; the nutrient source for submerged plant growth affect both the purification efficiency and the photosynthetic characteristics of submerged macrophytes. Excessive nitrogen and phosphorus concentrations can inhibit the photosynthetic physiological activities of submerged macrophytes, affecting the succession of aquatic vegetation. In addition, under high nutrient conditions, the competition from periphytic algae and planktonic algae may also directly poison submerged macrophytes, leading to its degradation and disappearance. Systematic studies on the regulation and photosynthetic fluorescence response mechanism of submerged macrophytes to varied nutrient loadings are helpful in revealing their relationships. The seedlings of submerged macrophyte V. natans were transplanted in a laboratory mesocosm to study the effect of nutrient loadings on its regulation of water nitrogen and phosphorus. Three nitrogen and phosphorus loadings from low, medium, and high levels derived from nitrate, ammonium, and phosphate were setup as the aquatic medium for the plant growth. Twelve harvests were carried out to determine the evolution of nutrient removal performance of V. natans. Its photosynthetic fluorescence characteristics were measured by a pulse-amplitude modulated fluorometer (Diving-PAM). Results showed that the nitrogen and phosphorus adsorption abilities of V. natans were gradually enhanced with the increase of nutrient concentrations in the range of TN ≤ 12 mg·L-1 and TP ≤ 1.0 mg·L-1. In the treatment of high nutrient concentrations (TN=12 mg·L-1 and TP=1.0 mg·L-1), the removal rates of nitrogen and phosphorus reached more than 95%. V. natans preferentially absorbed ammonium nitrogen when its concentration was high. The medium nutrient concentrations (TN:8-12 mg·L-1 and TP:0.6-1.0 mg·L-1) did not significantly affect the Fv/Fm ratio of leaves. However, the low nutrient concentrations (TN=3 mg·L-1 and TP=0.3 mg·L-1) could improve the Fv/Fm ratio of leaves and were beneficial for the growth of V. natans. The inhibition of photosynthetic activity and light tolerance were enhanced with the increase in nutrient concentrations. The photosynthetic activity of V. natans gradually recovered with no significant changes in the capacity for light harvesting, when the nutrient concentrations gradually decreased in the water. Our results indicate that the high nitrogen and phosphorus loadings indeed hamper the photosynthetic capacity, which may subsequently restrain the maintenance of the dominance of V. natans in the submerged macrophyte communities.

Combined effects of ocean acidification and nutrient levels on the photosynthetic performance of Thalassiosira (Conticribra) weissflogii (Bacillariophyta)

:The purpose of this study was to investigate the effects of ocean acidification and nutrient level on the growth and photosynthetic performance of the diatom Thalassiosira (Conticribra) weissflogii. Cells were exposed to varying levels of CO2 [current CO2 (LC), 400 μatm; high CO2 (HC), 1000 μatm] and nutrients, with NO3− and PO43− concentrations enriched, respectively, at 50 μmol l−1 and 5 μmol l−1 [high nutrient (HN)], 20 μmol l−1 and 2 μmol l−1 [mid-level nutrient (MN)] and 10 μmol l−1 and 1 μmol l−1 [low nutrient (LN)]. After acclimatization for over 20 generations, no significant differences in growth rates were observed between LC and HC cultures under both HN and LN conditions; whereas, HC significantly reduced the growth rate under MN conditions. Lower nutrient loading significantly inhibited the growth rates of both LC and HC cultures; whereas, HC (but not LC) significantly decreased chlorophyll a and carotenoid contents in LN treatments. HC conditions significantly increased maximum relative electron transport rates (rETRmax) and saturating light intensity (Ik) of HN cultures, with rETRmax showing a positive relationship with growth rates stimulated by nutrient enrichments. The maximum (Fv/Fm) and effective quantum yield (Yield) were all inhibited under LN conditions, with the greatest reduction in Yield observed under LC conditions, corresponding to the highest nonphotochemical quenching, lowest light use efficiency (α) and lowest rETRmax. Based on these results, ocean acidification and nutrient availability may influence photosynthetic performance in T. weissflogii individually or interactively, with the future growth of marine diatoms mediated by these codependent environmental drivers.

The effects of extrinsic factors on the structural and mechanical properties of Pseudomonas fluorescens biofilms: A combined study of nutrient concentrations and shear conditions.

The growth of biofilms on surfaces is a complicated process influenced by several environmental factors such as nutrient availability and fluid shear. In this study, combinations of growth conditions were selected for the study of Pseudomonas fluorescens biofilms including as cultivation time (24- or 48 h), nutrient levels (1:1 or 1:10 King B medium), and shear conditions (75 RPM shaking, 0.4 mL min -1 or 0.7 mL min -1). The use of Confocal Laser Scanning Microscopy (CLSM) determined biofilm structure, while liquid-phase Atomic Force Microscopy (AFM) techniques resolved the mechanical properties of biofilms. Under semi-static conditions, high nutrient environments led to more abundant biofilms with three times higher EPS content compared to biofilms grown under low nutrient conditions. AFM results revealed that biofilms formed under these conditions were less stiff, as shown by their Young's modulus values of 2.35 ± 0.08 kPa, compared to 4.98 ± 0.02 kPa for that of biofilms formed under low nutrient conditions. Under dynamic conditions, however, biofilms exposed to low nutrient conditions and high shear rates led to more developed biofilms compared to other tested dynamic conditions. These biofilms were also found to be significantly more adhesive compared to their counterparts grown at higher nutrient conditions.

Biochar-enhanced composts reduce the potential leaching of nutrients and heavy metals and suppress plant-parasitic nematodes in excessively fertilized cucumber soils.

Excessive fertilization is a common agricultural practice that has largely reduced soil nutrient retention capacity and led to nutrient leaching in China. To reduce nutrient leaching, in this study, we evaluated the application of biochar, compost, and biochar-compost on soil properties, leaching water quality, and cucumber plant growth in soils with different nutrient levels. In general, the concentrations of nutrients and heavy metals in leaching water were higher under high-nutrient conditions than under low-nutrient conditions. Both biochar and compost efficiently enhanced soil cation exchange capacity (CEC), water holding capacity (WHC), and microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP), reduced the potential leaching of nutrients and heavy metals, and improved plant growth. The efficiency of biochar and compost in soil CEC, WHC, MBC, MBN, and MBP and plant growth was enhanced when applied jointly. In addition, biochar and biochar-enhanced compost efficiently suppressed plant-parasitic nematode infestation in a soil with high levels of both N and P. Our results suggest that biochar-enhanced compost can reduce the potential environmental risks in excessively fertilized vegetable soils.

Influencing factors in quantitative measurement using activated platelet levels and platelet-activating capacity for the assessment of thrombosis in pre-metabolic syndrome and type 2 diabetes mellitus.

Activated platelet levels and platelet-activating capacity are well recognized as useful index parameters for the physiological and pharmacological prediction of thrombotic events. Recently, quantitative measurements for platelet functions using a flow cytometer have been increasing gradually. However, the relation of physiological factors, such as sex, aging, and laboratory tests, to platelet functions has not been well documented. We conducted a blood analysis of people with normal/pre-metabolic syndrome and patients with type 2 diabetes mellitus to clarify the pathological factors. The levels of basal (non-stimulated)-activated, platelet-expressed P-selectin and activated platelet stimulated by agonists were measured by a flow cytometer, and ratios of platelet-activating capacity were also calculated. Statistical analyses indicated significantly high basal-activated platelet in pre-metabolic syndrome, and basal-activated platelet was positively associated with hyperlipidemia and hepatic damage. Platelet-activating capacity was significantly low in aging and hyperlipidemia, but high in hyperglycemia, and was negatively associated with hyperlipidemia and hepatic damage. Aging and high nutrient condition impaired platelet functions. Quantitative measurements of basal-activated platelet and platelet-activating capacity are precise parameters for the prediction of thrombotic events.

A conserved stem of the Myxococcus xanthus sRNA Pxr controls sRNA accumulation and multicellular development

The small RNA (sRNA) Pxr negatively controls multicellular fruiting body formation in the bacterium Myxococcus xanthus, inhibiting the transition from growth to development when nutrients are abundant. Like many other prokaryotic sRNAs, Pxr is predicted to fold into three stem loops (SL1-SL3). SL1 and SL2 are highly conserved across the myxobacteria, whereas SL3 is much more variable. SL1 is necessary for the regulatory function of Pxr but the importance of SL3 in this regard is unknown. To test for cis genetic elements required for Pxr function, we deleted the entire pxr gene from a developmentally defective strain that fails to remove Pxr-mediated blockage of development and reintroduced variably truncated fragments of the pxr region to test for their ability to block development. These truncations demonstrated that SL3 is necessary for Pxr function in the defective strain. We further show that a highly conserved eight-base-pair segment of SL3 is not only necessary for Pxr to block development in the defective strain under starvation conditions, but is also required for Pxr to prevent fruiting body development by a developmentally proficient wild-type strain under high-nutrient conditions. This conserved segment of SL3 is also necessary for detectable levels of Pxr to accumulate, suggesting that this segment either stabilizes Pxr against premature degradation during vegetative growth or positively regulates its transcription.