Intracellular Phosphorus Content Research Articles

Coupling of light and nutrients affects Microcystis gas vesicle content at different depths

Abstract Lakes are important water resources for human beings, but Microcystis blooms pose a serious threat to drinking water security and aquatic ecosystems. Gas vesicles (GVs) are an important trigger for the occurrence of Microcystis blooms. To understand the effects of light and nutrients on GV content, the phytoplankton in Lake Erhai were investigated. The results showed that the average GV content in the surface water was higher than that in the deep water. The total nitrogen in water affected the GV content by limiting the protein content, and the content of GVs increased by 9.2 μm3/cell for each 1.0 pg/cell increase in the intracellular nitrogen content. Moreover, light and total phosphorus affected the GV content in deep water by limiting the energy supply, and the content of GVs increased by 52.4 μm3/cell for each 1.0 pg/cell increase in the intracellular phosphorus content. These results indicate that for lakes with low transparency, decreasing the total phosphorus concentration can reduce the GV content. Reducing the total nitrogen concentration can reduce the GV content and decrease the dominance of Microcystis in all lakes. This study provides useful information for the control of Microcystis.

Spatial and temporal variations in algal phosphorus in Taihu Lake

AbstractPhosphorus circulation in Taihu Lake has attracted extensive attention, but the contribution of Microcystis to phosphorus circulation in this area is unknown. In this study, the phosphorus concentrations in algal samples collected from the lake in 2015–2016 were determined in the laboratory. From the concentration data, the total quantity of algal phosphorus was calculated and the seasonal variations in algal phosphorus were examined. The results indicated that the intracellular phosphorus content of Microcystis in Taihu varied from 0.044 to 0.130 pg/cell and tended to be high in spring and low in summer. The total amount of algal phosphorus in Taihu Lake ranged between 7.78 and 97.32 t over the study period. Algal phosphorus only accounted for between 1.5 and 18.5% of the phosphorus stock in the water. Because Microcystis accumulated downwind, there was a tendency for the total phosphorus concentrations to be low in the east of the lake and high in the west of the lake. This new information about the spatial and temporal distribution of algal phosphorus contributes to our understanding of how phosphorus in Microcystis contributes to phosphorus circulation in Taihu Lake.

Effect of intracellular P content on phosphate removal in Scenedesmus sp. Experimental study and kinetic expression

The present work determines the effect of phosphorus content on phosphate uptake rate in a mixed culture of Chlorophyceae in which the genus Scenedesmus dominates. Phosphate uptake rate was determined in eighteen laboratory batch experiments, with samples taken from a progressively more P-starved culture in which a minimum P content of 0.11% (w/w) was achieved. The results obtained showed that the higher the internal biomass P content, the lower the phosphate removal rate. The highest specific phosphate removal rate was 6.5mgPO4–PgTSS−1h−1. Microalgae with a P content around 1% (w/w) attained 10% of this highest removal rate, whereas those with a P content of 0.6% (w/w) presented 50% of the maximum removal rate. Different kinetic expressions were used to reproduce the experimental data. Best simulation results for the phosphate uptake process were obtained combining Steele equation and Hill function to represent the effect of light and intracellular phosphorus content, respectively.

Mixed microalgae culture for ammonium removal in the absence of phosphorus: Effect of phosphorus supplementation and process modeling

Microalgal growth and ammonium removal in a P-free medium have been studied in two batch photobioreactors seeded with a mixed microalgal culture and operated for 46 days. A significant amount of ammonium (106mg NH4-Nl−1) was removed in a P-free medium, showing that microalgal growth and phosphorus uptake are independent processes. The ammonium removal rate decreased during the experiment, partly due to a decrease in the cellular phosphorus content. After a single phosphate addition in the medium of one of the reactors, intracellular phosphorus content of the corresponding microalgal culture rapidly increased, and so did the ammonium removal rate. These results show how the amount of phosphorus internally stored affects the ammonium removal rate. A mathematical model was proposed to reproduce these observations. The kinetic expression for microalgae growth includes a Monod term and a Hill's function to represent the effect of ammonium and stored polyphosphate concentrations, respectively. The proposed model accurately reproduced the experimental data (r=0.952, P-value <0.01).

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.

Influence of phosphorus and irradiance on phytoplanktonic chlorophyll-a concentration and phosphorus contents at a diel scale in a Mediterranean reservoir

Influence of phosphorus and irradiance on phytoplanktonic chlorophyll-a concentration and phosphorus contents at a diel scale in a Mediterranean reservoir Phosphorus concentration in the water is one of the main factors regulating phytoplankton biomass and productivity in inland water bodies. However, phosphorus uptake by algae could not cause immediate growth, because other factors (light and other nutrient availability) may limit production. Nonetheless, luxurious phosphorus uptake (i.e. phosphorus uptake beyond the algal requirements) has been observed, and it has been interpreted as storage to use in situations of low nutrient availability. Thus, the assessment of the effect of phosphorus supply on algal growth is not straightforward, especially at very short time scales. In this study, we analyze the relationships between environmental phosphorus levels and internal phosphorus and chlorophyll-a contents in phytoplankton at a diel scale in a Mediterranean reservoir, considering the different algal (intracellular and membrane-associated) and water phosphorus pools. We also evaluated the influence of light on these relationships by sampling at two water depths with different irradiance levels. Our hypothesis is that chlorophyll-a and intracellular phosphorus contents in phytoplankton are both influenced by ambient phosphorus and irradiance levels, which are complementary resources for algae as the nutrient-light hypothesis proposes. Phosphorus concentration and relative contribution of each phosphorus fraction was similar at both sampling depths. Total phosphorus concentration was dominated by the particulate pool (70 %), and dissolved inorganic phosphate represented only one third of the dissolved pool. Total phosphorus content and the relative contribution of the different pools in algal cells were similar at both sampling depths. Intracellular phosphorus pool was on average 77 % of the total nutrient content, while phosphorus associated to membranes represented the remaining of the total pool. Mean intracellular SRP concentration was 36 % of the intracellular phosphorus content. None of the algal phosphorus pools showed significant correlations with un- derwater light levels at both sampling depths. Total chlorophyll-a concentration showed no significant correlations with the several water phosphorus pools at both sampling depths, because each algal group responded differently to environmental phosphorus levels, and these responses also varied with depth. We found significant relationships between the intracellular phosphorus content and the different phosphorus pools in water, but this almost 'automatic' response of algae to phosphorus levels in water was not reflected in changes in the chlorophyll-a content, at least within the 3-day time frame of this study. A possible explanation is that processes associated to nutrient uptake and biomass construction operate over different time scales. The results of this work emphasize the complexity of the links between environmental phosphorus concentration and phytoplanktonic phosphorus content and biomass, and the importance of scale in analysing such relationships.

Estimation of intracellular phosphorus content of phosphorus-accumulating organisms at different P:COD feeding ratios

The intracellular phosphorus content of phosphorus-accumulating organisms (PAO) was determined based on a stoichiometric equation and phosphorus balance for an enhanced biological phosphorus removal system fed with different P:COD ratios. The data indicated that a higher P:COD feeding ratio could significantly promote the growth of PAO. As the P:COD feeding ratio increased from 0.02:1 to 0.04:1 and 0.16:1, the phosphorus in the sludge increased considerably from 0.053 to 0.084 and 0.205 mg P (mg VSS aerobic) −1, respectively, indicating a dynamic condition in the microbial population. From the calculations, the mass fractions of the PAO, glycogen-accumulating organisms, and ordinary heterotrophs changed from 0.10–0.15, 0.83–0.88, and 0.02 at 0.02:1 to 0.19–0.28, 0.70–0.79, and 0.02 at 0.04:1 and to 0.478–0.71, 0.26–0.50, 0.03 at 0.16:1 P:COD feeding ratios, respectively. Despite the variation in microbial diversity, the calculated phosphorus contents of the PAO at all P:COD feeding ratios were consistent between 0.241 and 0.378 mg P (mg VSS PAO) −1. The initial specific phosphorus release and uptake rates were 84.7–167.9 mg P (g VSS PAO) −1 h −1 and 52.8–90.0 mg P (g VSS total) −1 h −1, respectively.

Phosphorus accumulation by a marine photosynthetic bacterium, Chromatium sp.

Among 8 strains of typical marine and freshwater photosynthetic bacteria, a Chromatium sp., which is known to flocculate upon the addition of seawater, had the highest intracellular phosphorus content of 0.865 mmol P/mg dry wt with a ratio of polyphosphate to phosphate (poly-Pi/Pi) of 2.14. Intracellular phosphorus content increased withincreasing NaCl concentration up to 260 mM. The poly-Pi/Pi value was also the highest in the medium containing 260 mM NaCl. Sodium cation in seawater enhanced intracellular phosphorus accumulation in this bacterium.

Kinetic Expression for Pigment Production in Culture of Red beet Hairy Roots.

A kinetic model was proposed to represent the profile of pigment production associated with the growth of red beet hairy roots. This model was constructed on the basis of a concept of cellular age distribution arising from a linear growth mode of the roots. The kinetics of root proliferation were formulated using a Monod-type rate equation of root elongation with intracellular phosphorus as a limiting substrate. A positional dependence of pigment content was observed along with the hairy roots; namely, content increased with increasing distance from the root tips and gradually approached a saturated value correlated with intracellular phosphorus content. The kinetics of pigment formation of hairy roots were presented by considering the variation in pigment content along the roots and the intracellular phosphorus effect. It was demonstrated that the model made it possible to describe the kinetic behaviors of growth and pigmentation during hairy root culture in a fermentor.

藻類のリン摂取と増殖に関する動力学モデル

A structured model introduced by considering algal mass to be composed of two components which were an intracellular phosphate and a structural substance, was proposed for algal phosphate uptake and growth dynamics. Further, the kinetics for phosphate uptake and growth of Microcystis aeruginosa were investigated at steady state or transient state, using continuous and batch culture experiments.Continuous culture experiments indicated that specific growth rate, μ was expressed as a hyperbolic function of intracellular phosphorus content, fP. While, specific rate of phosphate uptake, σ was inversely as fP. The fP values ranged from a maximum of about 5.0% to a minimum of about 0.15% phosphate per cell dry weight.At balanced growth, σ was related to μ and fP in the form of σ=fP·μ which was derived from the model presented here. So, parabolic relationship was found between σ and μ, because fP increased with increasing μ.The kinetic equation of transient phosphate uptake was given by dfp/dt=σ-μ·fP. This kinetic model was able to simulate overplus phenomena that when M. aeruginosa grown in a phosphate deficient continuous culture was suddenly brought into contact with a phosphate rich medium, phosphate was accumulated into the cell above the intracellular content required to sustain maximum growth rate.

Renal osteodystrophy: some new questions on an old disorder.

The two major lesions of renal osteodystrophy are osteitis fibrosa cystica (OFC) and osteomalacia (OM). OFC is the characteristic bone lesion of uremic hyperparathyroidism. Although renal failure causes predictable parathyroid hyperplasia, the precise pathogenetic mechanism is still not defined. The "hyperphosphatemia-hypocalcemia-parathyroid hormone (PTH) hypersecretion" sequence of events is no longer an adequate model for the pathogenesis of uremic hyperparathyroidism. Other abnormalities associated with uremia include reduced 1,25-dihydroxyvitamin D (1,25D) synthesis, changes in intracellular phosphorus content or transcellular phosphate fluxes, or alteration in PTH metabolism, eg, change in set-point for PTH secretion. Each abnormality interacts with others and contributes to PTH hypersecretion, but none can completely account for the development and persistence of hyperparathyroidism in renal failure. The possibility that uremia may directly cause parathyroid hyperplasia remains open. It is also possible that factor(s) that initiate hyperparathyroidism may turn out to be quite different from that which sustains the hyperparathyroid state. Although both vitamin D-deficient and vitamin D-resistant OM may develop in patients with renal failure, the majority of uremic OM seen currently is "vitamin D-refractory." Although now there is persuasive evidence implicating aluminum (Al) accumulation as the major pathogenetic cause for the mineralization defect seen in this disorder, additional disturbances may play important contributory roles. Such factors would include extraskeletal effects of Al, differences in host-susceptibility to this element, the localization of Al within bone, uremia per se, and the participation of other metals and toxins. Finally, possible interactions between hyperparathyroidism and OM of uremia are speculated on.

Kinetic model of algal growth incorporating intracellular carbohydrate and phosphorus pools

A series of studies on a kinetic model of photosynthesis, nutrient ingestion, and metabolism for algal growth were conducted. Coefficients included in the proposed model were examined referring to experimental data on growth of Chlorella sp. It was shown that the proposed model can simulate the mechanism of algal growth, change of intracellular phosphorus content, change of intracellular carbohydrate content, and effects of nutrients on algal growth.

Kinetics of phosphate limited algal growth.

The kinetics of phosphate limited growth of two green algae Chlorella pyrenoidosa and Selenastrum capricornutum have been studied in chemostats. Several kinetic models which express the specific growth rate as a function of the intracellular phosphorus content have been examined, and one of the models was found to be significantly better than the other models. The principles of this model were described in a recent paper by Nyholm. The kinetics of phosphate uptake have been investigated by adding pulses of phosphate to the chemostats, The uptake by phosphorus deficient cells could be described by Michaelis-Menten kinetics for phosphate concentrations below approximately 500 microng P/liter. Further, with the assumption of a discontinuous adjustment of the uptake rate at the onset of phosphorus deficiency, a complete kinetic model for growth and phosphate removal is proposed. The mean cell size and the contents of chlorophyll a and RNA per unit dry weight have been measured for C. pyrenoidosa as a function of the dilution rate.