Phosphorus-deficient Conditions Research Articles

Isolation of the inorganic phosphorus-solubilizing bacteria Lysinibacillus sphaericus and assessing its role in promoting rice growth.

Soluble phosphorus scarcity severely limits plant growth and crop yield. In this study, a strain of inorganic phosphorus-solubilizing bacteria, Lysinibacillus sphaericus, was isolated from rice rhizosphere soil. The available phosphorus content in liquid inorganic phosphorus identification medium and in L. sphaericus-inoculated soil increased from 204.28mg/L to 1124.68mg/L and from 4.75mg/kg to 7.04mg/kg, respectively. The pH decreased significantly from 6.87 to 6.14. Incubation with L. sphaericus significantly increased malic and succinic acid content in the liquid inorganic phosphorus identification medium and increased acid phosphatase and alkaline phosphatase activity in the soil. Inoculation with L. sphaericus significantly increased rice growth, chlorophyll a/b content, and photosynthesis by increasing the soluble phosphorus content in the rice rhizosphere soil under phosphorus-deficient conditions. Further analysis revealed that L. sphaericus improved soil phosphorus release by decreasing soil pH and promoting acid phosphatase and alkaline phosphatase activity. This study supports the production of microbial fertilizers to improve rice yield in phosphorus-deficient conditions.

Understanding filamentous cyanobacteria and their adaptive niches in Lake Honghu, a shallow eutrophic lake

Freshwater lakes globally are witnessing an escalation in the frequency and intensity of cyanobacterial harmful blooms. However, underlying factors influencing the succession or coexistence of cyanobacteria, especially filamentous ones, remain poorly understood. Lake Honghu, a Ramsar Wetland of International Importance with degrading aquatic ecological quality, served as a case study to elucidate the intricate relationship between environmental changes and cyanobacterial dynamics. Our analysis revealed a significant increase in the dominance of filamentous cyanobacteria, marked by high spatiotemporal variability in community structure. This dominance of filamentous diazotrophic cyanobacteria is attributed to a decrease in the ratio of dissolved inorganic nitrogen to total phosphorus and their capacity to utilize organic phosphorus in phosphorus-deficient conditions. Species-specific density variations were linked to diverse environmental factors, with total nitrogen or total phosphorus concentration remaining as a crucial factor influencing dominant cyanobacterial density fluctuations. The dominance of low-temperature-tolerant Aphanizomenon and Pseudanabaena was evident in spring and winter, whereas Dolichospermum and Cylindrospermopsis, which prefer higher temperatures, thrived in summer and autumn. Additionally, non-algal turbidity and heterogeneity can potentially alter the competitive outcome among filamentous cyanobacteria or foster coexistence under conditions of elevated temperatures and nutrient limitation. This study predicts that filamentous cyanobacteria may spread and persist in lakes spanning a wide trophic range. Current findings enhance our comprehension of the dynamic responses exhibited by filamentous bloom-forming cyanobacteria in the face of environmental changes within shallow eutrophic lakes and provide valuable insights for lake managers involved in the remediation of degraded shallow lakes.

Physiological effects of seed priming on barley cultivated under phosphorus deficiency conditions

Physiological effects of seed priming on barley cultivated under phosphorus deficiency conditions

Genetic Variability Analysis for Yield and Its Attributing Traits in Rice (Oryza Sativa L.) under Phosphorus-sufficient and Deficient Field Conditions

Aim: The present study aims to identify phosphorus deficiency tolerant rice genotypes under both phosphorus-sufficient and deficient conditions. Materials and Methods: Two kinds of fields (high and low phosphorus content) were selected based on their soil phosphorus availability. Hundred diverse rice germplasm was collected and planted in an augmented design along with four local checks namely, Swarna sub-1, MTU 1153, MTU 7029 and Uttar Sona. The data was recorded for 14 traits and subjected to different types of variability analysis. Place and Season of Study: The experiment took place at instructional Farm of Uttar Banga Krishi Vishwavidyalaya, Cooch Behar, West Bengal, India during the Kharif season of 2021. Results: The variability analysis revealed that phosphorus uptake showed a high genotypic coefficient of variation (GCV) under phosphorus-deficient condition and high phenotypic coefficient of variation (PCV) under both conditions. Grain yield showed high GCV and PCV under both the phosphorus conditions. Heritability was moderate whereas high Genetic advance as percentage of mean was observed under both the conditions for both phosphorus uptake and grain yield. Strong positive correlations were observed between days to flowering and various yield-related traits under both the conditions. Positive correlation was observed between phosphorus uptake and grain yield under phosphorus-sufficient condition, but a weaker correlation under phosphorus-deficient condition.

Influence and Role of Fungi, Bacteria, and Mixed Microbial Populations on Phosphorus Acquisition in Plants

Phosphorus (P) stands as a pivotal macroelement in relation to the growth of plants. It plays a significant role in physiological processes, as components of biofilms and nucleotides, and in metabolic activities within plants. The deprivation of phosphorus detrimentally impacts the growth and developmental of plants. However, the rhizosphere’s beneficial fungi and bacteria augment the efficacy of phosphorus uptake, participate in the molecular regulation of phosphorus, stimulate physiological alterations in plants, and facilitate signal transmission. In order to give readers a better understanding of the effects and positive roles of soil beneficial fungi and bacteria in regulating plant phosphorus acquisition and transport, this present review introduces the role and influence of rhizosphere microorganisms (fungi and bacteria) in assisting plant phosphorus absorption, and summarizes the key phosphorus transporters found in their interaction with plants. Using mixed microbial populations as composite microbial fertilizers has a positive effect on plants under phosphorus-deficiency conditions. It will be conducive to a better understanding of the mutualistic relationship between fungi, bacteria, and plants to provide a way to reduce the application of phosphorus fertilizers efficiently, and to provide a research background for the development of microbiological fertilizers.

Bacillus megaterium Compensates for Growth Inhibition from Phosphorus Deficiency by Improving Photosynthetic Capacity, Changing Antioxidant Potential, and Regulating Non-Structural Carbohydrate Concentrations in Glycyrrhiza uralensis

This study assessed the effect of Bacillus megaterium on seedling growth of Glycyrrhiza uralensis Fisch. under control and phosphorus (P) deficiency conditions. The results showed that P deficiency improved 1) G. uralensis root growth, 2) superoxide dismutase, catalase, and peroxidase activities, 3) inorganic P, starch, and soluble sugar contents in roots, 4) dissipated energy flux per reaction center, trapped energy flux per reaction center, and absorption flux per reaction center, and 5) net photosynthetic rate, stomatal conductance, transpiration rate, maximum fluorescence intensity after dark adaptation, and variable fluorescence. However, P deficiency significantly decreased chlorophyll and carotenoid contents in G. uralensis, but enhanced chlorophyll and carotenoid contents in B. megaterium. Our findings on the regulatory mechanisms of B. megaterium in response to P starvation hold promise for improving the success of G. uralensis cultivation.
 Keywords: Bacillus megaterium; Glycyrrhiza uralensis Fisch; Phosphorus deficiency; Chlorophyll fluorescence; Antioxidant enzymes superoxide; Non-structural carbohydrate

Nanosilica enhances morphogenic and chemical parameters of Megathyrsus maximus grass under conditions of phosphorus deficiency and excess stress in different soils

Phosphorus (P) imbalances are a recurring issue in cultivated soils with pastures across diverse regions. In addition to P deficiency, the prevalence of excess P in soil has escalated, resulting in damage to pasture yield. In response to this reality, there is a need for well-considered strategies, such as the application of silicon (Si), a known element for alleviating plant stress. However, the influence of Si on the morphogenetic and chemical attributes of forage grasses grown in various soils remains uncertain. Consequently, this study aimed to assess the impact of P deficiency and excess on morphogenetic and chemical parameters, as well as digestibility, in Zuri guinea grass cultivated in Oxisol and Entisol soils. It also sought to determine whether fertigation with nanosilica could mitigate the detrimental effects of these nutritional stresses. Results revealed that P deficiency led to a reduction in tiller numbers and grass protein content, along with an increase in lignin content. Conversely, P excess resulted in higher proportions of dead material and lignin, a reduced mass leaf: stem ratio in plants, and a decrease in dry matter (DM) yield. Fertigation with Si improved tillering and protein content in deficient plants. In the case of P excess, Si reduced tiller mortality and lignin content, increased the mass leaf:stem ratio, and enhanced DM yield. This approach also increased yields in plants with sufficient P levels without affecting grass digestibility. Thus, Si utilization holds promise for enhancing the growth and chemical characteristics of forage grasses under P stress and optimizing yield in well-nourished, adapted plants, promoting more sustainable pasture yields.

Comparative physiological, metabolomic, and transcriptomic analyses reveal mechanisms of apple dwarfing rootstock root morphogenesis under nitrogen and/or phosphorus deficient conditions.

Nitrogen (N) and phosphorus (P) are essential phytomacronutrients, and deficiencies in these two elements limit growth and yield in apple (Malus domestica Borkh.). The rootstock plays a key role in the nutrient uptake and environmental adaptation of apple. The objective of this study was to investigate the effects of N and/or P deficiency on hydroponically-grown dwarfing rootstock 'M9-T337' seedlings, particularly the roots, by performing an integrated physiological, transcriptomics-, and metabolomics-based analyses. Compared to N and P sufficiency, N and/or P deficiency inhibited aboveground growth, increased the partitioning of total N and total P in roots, enhanced the total number of tips, length, volume, and surface area of roots, and improved the root-to-shoot ratio. P and/or N deficiency inhibited influx into roots, and H+ pumps played a important role in the response to P and/or N deficiency. Conjoint analysis of differentially expressed genes and differentially accumulated metabolites in roots revealed that N and/or P deficiency altered the biosynthesis of cell wall components such as cellulose, hemicellulose, lignin, and pectin. The expression of MdEXPA4 and MdEXLB1, two cell wall expansin genes, were shown to be induced by N and/or P deficiency. Overexpression of MdEXPA4 enhanced root development and improved tolerance to N and/or P deficiency in transgenic Arabidopsis thaliana plants. In addition, overexpression of MdEXLB1 in transgenic Solanum lycopersicum seedlings increased the root surface area and promoted acquisition of N and P, thereby facilitating plant growth and adaptation to N and/or P deficiency. Collectively, these results provided a reference for improving root architecture in dwarfing rootstock and furthering our understanding of integration between N and P signaling pathways.

Arbuscular Mycorrhizal Fungi Response on Soil Phosphorus Utilization and Enzymes Activities in Aerobic Rice under Phosphorus-Deficient Conditions.

The prominence of arbuscular mycorrhizal fungi (AMF) in sustainable rice production has long been recognized. However, there is little information about AMF response in aerobic rice cultivation under phosphorus (P)-deficient conditions. The aim of this experiment was to compare and determine the preeminent AMF effects on rice mycorrhizal colonization, responsiveness, P utilization, and different growth-promoting traits under P-deficient conditions. Different AMF genera viz. (Funneliformis sp., Rhizophagus sp., Glomus sp., Acaulospora sp., and Claroideoglomus sp.) in four different aerobic rice varieties developed by ICAR-NRRI, India (CR Dhan 201, CR Dhan 204, CR Dhan 205, and CR Dhan 207) were investigated using the check P-susceptible variety (IR 36) and the P-tolerant variety (Kasalath IC459373). Data analyzed through linear modeling approaches and bivariate associations found that AMF colonization was highly correlated with soil enzymes, particularly fluorescein diacetate (FDA) and plant P uptake. The microbial biomass carbon (MBC) and FDA content were significantly changed among rice varieties treated with AMF compared to uninoculated control. Out of four different rice varieties, CR Dhan 207 inoculated with AMF showed higher plant P uptake compared to other varieties. In all the rice varieties, AMF colonization had higher correlation coefficients with soil enzymes (FDA), MBC, and plant P uptake than uninoculated control. The present study indicates that AMF intervention in aerobic rice cultivation under P-deficient conditions significantly increased plant P uptake, soil enzymes activities and plant growth promotion. Thus, the information gathered from this study will help us to develop a viable AMF package for sustainable aerobic rice cultivation.

OPTIMIZATION OF THE MINERAL NUTRITION CONDITIONS OF MUSTARD

The article gives an assessment of one of the promising and valuable oilseeds - mustard, the cultivation of which is provided by the program of diversification of grain production in Kazakhstan, in particular, crop production. It was revealed that the conditions of mineral nutrition of mustard in the steppe zone of Northern Kazakhstan were not studied. Therefore, experiments were laid to study the optimization of the conditions for the mineral nutrition of mustard. A 14-variant scheme was presented to create different levels of phosphorus and nitrogen in the soil in order to determine the quantitative connection between the level of nutrients in the soil and the productivity of mustard varieties. The purpose of the research (2019-2021) was to study the features of mineral nutrition and fertilizer of mustard in the conditions of the steppe zone of Northern Kazakhstan. Their main directions were: to study the requirements of this crop to the level of fertility and soil properties; study the properties of the soil and determine its ability to meet the needs of crops. The conclusions of the research suggest that in all year’s mustard has developed under conditions of phosphorus deficiency in the soil, an average supply of nitrogen, and an increased supply of potassium. The application of nitrogenphosphorus fertilizers contributed to an increase in the content of nitrogen, nitrates and mobile phosphorus in the soil by 2-3 times and was determined by the amount of fertilizers applied.

Impact of overflow vs. limitation of propionic acid on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) biosynthesis

The 3HV content of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)), a biobased and biodegradable polyester, must be controlled for improved thermomechanical properties. Propionic acid (PA) is the main acid allowing 3HV monomer biosynthesis which is present in volatile fatty acid mixes produced from agro-industrial coproducts acidogenesis. With the strain Cupriavidus necator, we investigated the impact of carbon-limiting vs. carbon-overflow conditions thanks to fed-batch cultures, with sequential or continuous feeding of propionic acid as the sole carbon source, and phosphorus deficiency conditions. Regardless of the C-limiting continuous specific feeding rate imposed (i.e., below the determined critical specific feeding rate (qPAcrit) of 0.24 Cmol.Cmol−1.h−1), a regular incorporation of the 3HV in the copolymer at a content of 23 ± 4 mol% was observed with a high molecular weight (≈ 1000 kDa) and a remarkably low polydispersity index (≈ 1.5). This feeding strategy maximized both the productivity (up to 0.78 g.L−1.h−1) and conversion yield of propionic acid into P(3HB-co-3HV) (up to 0.59 Cmol.Cmol−1) if operated close to qPAcrit. With C-overflow sequential feeding (i.e., above qPAcrit), the residual propionic acid concentration has been highlighted as a key parameter in 3HV content improvement (≥ 44 mol%) even though it occurred at the expense of the copolymer yield and productivity.

NtPIN3 positively regulates low phosphorus tolerance by changing root elongation, Pi concentration and antioxidant capacity in tobacco

Phosphorus (P) is a critical nutrient for plants, and inorganic orthophosphate (Pi) deficiency results in declining crop quality and yields. Auxin plays a key regulatory effect on plant growth in response to Pi deficiency, yet the regulatory mechanisms remain poorly understood. In this study, we cloned and identified an auxin efflux transporter, NtPIN3, involved in the low phosphate response of tobacco (Nicotiana tabacum). NtPIN3 is located on the cytoplasmic membrane, and high expression levels of NtPIN3 were observed under phosphorus deficiency conditions. Moreover, NtPIN3 overexpression in tobacco could dramatically enhance low Pi tolerance by increasing the root length, which was consistent with the GUS activity and the auxin concentration in the root. Notably, Pi concentration and antioxidant capacity in overexpression transgenic tobacco were significantly increased compared with the wild type (WT) under low Pi stress conditions due to Pi uptake (NtPT1 and NtPT2) and antioxidant capacity (superoxide dismutase, peroxidase, and catalase). In contrast, compared with WT, the ntpin3 mutant significantly reduced root length, auxin concentration, Pi concentration, and antioxidant capacity under low Pi stress conditions, suggesting that NtPIN3 is a positive regulator of low phosphate in tobacco. In addition, the yeast-two-hybrid and luciferase complementation imaging assay confirmed that NtPIN3 interacted with NtPIN2. Altogether, the NtPIN3 involved in low Pi response and overexpression of NtPIN3 contributed to enhanced tolerance to low Pi stress, which proved an underlying gene for breeding low Pi-stress tolerant plants.

In-frame mutation in rice TEOSINTE BRANCHED1 (OsTB1) improves productivity under phosphorus deficiency

Tillering is an important trait in rice productivity. We introduced mutations into the coding region of rice TEOSINTE BRANCHED1 (OsTB1), which is a negative regulator of tillering, using CRISPR/Cas9. The frameshift mutants exhibited substantially enhanced tillering and produced 3.5 times more panicles than the non-mutated plants at maturity. This enhanced tillering resulted in increased spikelet number; however, grain yields did not increase due to substantially reduced filled grain rate and 1,000-grain weight. In contrast, in-frame mutations in OsTB1 had the effect of slightly increasing tiller numbers, and the in-frame mutants had 40% more panicles than non-mutated plants. The grain yield of in-frame mutants also did not increase on nutrient-rich soil; however, under phosphorus-deficient conditions, where tillering is constrained, the in-frame mutants gave a significantly higher grain yield than non-mutated plants due to higher spikelet number and maintained filled grain rate. Rice grassy tiller1 (OsGT1)/OsHox12, which is directly regulated by OsTB1 to suppress tillering, was moderately down-regulated in in-frame mutants, suggesting that OsTB1 with the in-frame mutation shows partial function of intact OsTB1 in regulating OsGT1/OsHox12. We propose that mildly enhanced tillering by in-frame mutation of OsTB1 can improve grain yield under low phosphorus conditions.

Overexpression of soybean microRNA156b enhanced tolerance to phosphorus deficiency and seed yield in Arabidopsis

microRNAs (miRNAs) are endogenous small RNAs that are key regulatory factors participating in various biological activities such as the signaling of phosphorus deficiency in the plant. Previous studies have shown that miR156 expression was modulated by phosphorus starvation in Arabidopsis and soybean. However, it is not clear whether the over-expression of soybean miR156b (GmmiR156b) can improve a plant’s tolerance to phosphorus deficiency and affect yield component traits. In this study, we generated Arabidopsis transgenic lines overexpressing GmmiR156b and investigated the plant’s response to phosphorus deficiency. Compared with the wild type, the transgenic Arabidopsis seedlings had longer primary roots and higher phosphorus contents in roots under phosphorus-deficit conditions, but lower fresh weight root/shoot ratios under either phosphorus-deficient or sufficient conditions. Moreover, the GmmiR156b overexpression transgenic lines had higher phosphorus content in shoots of adult plants and grew better than the wide type under phosphorus-deficient conditions, and exhibited increased seed yields as well as strong pleiotropic developmental morphology such as dwarfness, prolonged growth period, bushy shoot/branching, and shorter silique length, suggesting that the transgenic lines were more tolerant to phosphorus deficiency. In addition, the expression level of four SQUAMOSA PROMOTER BINDING PROTEIN LIKE (SPL) genes (i.e., AtSPL4/5/6/15) were markedly suppressed in transgenic plants, indicating that they were the main targets negatively regulated by GmmiR156b (especially AtSPL15) and that the enhanced tolerance to phosphorus deficiency and seed yield is conferred mainly by the miR156-mediated downregulation of AtSPL15.

NADPH oxidase contributes to the production of reactive oxygen species in Chlorella pyrenoidosa.

Reactive Oxygen Species (ROS) play an important role in oxidative stress and are related to the lipid accumulation in microalgae. Nicotinamide Adenine Dinucleotide Phosphate (NADPH) oxidase can oxidize O2 to O2- ultimately. However, the function of NADPH oxidase and its contribution to the production of the intracellular total ROS are still unclear. In this study, the function of NADPH oxidase in Chlorella pyrenoidosa (C. pyrenoidosa) was investigated by adding activators Ca2+ and NADPH and inhibitors EGTA, LaCl3, DPI and BAPTA of NADPH oxidase. The results show that the addition of activators of Ca2+ or NADPH significantly increased the intracellular concentrations of ROS molecules (H2O2, O2-, and OH·) in C. pyrenoidosa. Moreover, the intracellular ROS level was higher under the nitrogen-deficient and phosphorus-deficient conditions than in control condition, but the addition of the inhibitors (EGTA, LaCl3, DPI, and BAPTA) of NADPH oxidase significantly reduced the intracellular concentrations of H2O2, O2-, and OH·. The study shows that NADPH oxidase actively participated in the production of intracellular ROS in C. pyrenoidosa, demonstrating that NADPH oxidase was another important element in the production of intracellular ROS in addition to mitochondria, chloroplasts and lysozymes in microalgae.

Optimizing phosphorus removal for municipal wastewater post-treatment with Chlorella vulgaris

The microalgal species Chlorella vulgaris was cultivated in batch conditions to identify the optimum set of initial conditions for the best biomass growth rate, phosphate removal, polyphosphate accumulation, and protein productivity. To study the effect of phosphorus deficiency caused stress, the microalgal biomass was exposed to phosphorus deficiency conditions for periods varying between 1 and 10 days and inoculated at different initial biomass and phosphate concentrations. A 10-day period of phosphate deficiency, supported by low initial biomass concentration (∼0.25 mg DW L−1), increased the phosphate removal by 62–175% when compared to the reference conditions. A 10-day period of biomass P-deficiency also boosted the polyphosphate accumulation and protein productivity, increasing them up to 40 and 46.8 times, respectively, if compared to reference conditions. At the same time, optimization algorithm model results suggested one-day biomass P-starvation with low initial biomass concentration as the optimum combination to achieve the highest performance while the initial phosphate concentration had less impact. The initial conditions suggested by the optimization model were validated in a sequencing batch photobioreactor, giving 101.7 and 138.0% more phosphate removal and polyphosphate accumulation, compared to the reference conditions. The obtained results present microalgae exposure to phosphorus stress as a supplementary tool for wastewater post-treatment targeted on rapid phosphorus removal.

Preferences of Pinus sylvestris seedling roots for different phosphorus sources under phosphorus-deficient conditions

PurposePhosphorus (P) is a limiting nutrient in many managed forests. To further understand the risks and benefits of biochars as sustainable P source in forest management, an improved mechanistic understanding of its interactions in root systems is required.MethodsA rhizobox experiment was conducted to observe root response of P. sylvestris (Scots pine) seedlings to different biochars in comparison to triple superphosphate (TSP) fertiliser as a P source. Three types of wood-derived biochar were compared: biochar from mixed softwood pellets (“Reference biochar”); from the vascular cambium zone of Picea sitchensis (“VCZ biochar”) and from mixed softwood pellets infused with TSP (“Processed biochar”). These biochars presented a range of available P from low to high. Seedling root development was spatially analysed using GIS software.ResultsThe total length of P. sylvestris roots did not significantly differ between treatments. However, seedling roots showed strong preference for soil proximal to VCZ biochar and strong avoidance to TSP fertiliser. There was a milder avoidance effect for Processed biochar. Differences in root responses could be explained by available P: roots favored a moderate, sustained P source and avoided high available P sources. The avoidance effect can be attributed partially to lower soil pH around TSP fertiliser.ConclusionThe extent concentration and duration of P availability affects the root response of P. sylverstris to P sources. Under P-deficient conditions, P. sylvestris root growth was markedly improved by introducing biochar with a certain P concentration, and VCZ biochar has potential as an effective source of P in forest establishment.

Monogalactosyl diacylglycerol synthase 3 affects phosphate utilization and acquisition in rice.

Galactolipids are essential to compensate for the loss of phospholipids by 'membrane lipid remodelling' in plants under phosphorus (P) deficiency conditions. Monogalactosyl diacylglycerol (MGDG) synthases catalyse the synthesis of MGDG which is further converted into digalactosyl diacylglycerol (DGDG), later replacing phospholipids in the extraplastidial membranes. However, the roles of these enzymes are not well explored in rice. In this study, the rice MGDG synthase 3 gene (OsMGD3) was identified and functionally characterized. We showed that the plant phosphate (Pi) status and the transcription factor PHOSPHATE STARVATION RESPONSE 2 (OsPHR2) are involved in the transcriptional regulation of OsMGD3. CRISPR/Cas9 knockout and overexpression lines of OsMGD3 were generated to explore its potential role in rice adaptation to Pi deficiency. Compared with the wild type, OsMGD3 knockout lines displayed a reduced Pi acquisition and utilization while overexpression lines showed an enhancement of the same. Further, OsMGD3 showed a predominant role in roots, altering lateral root growth. Our comprehensive lipidomic analysis revealed a role of OsMGD3 in membrane lipid remodelling, in addition to a role in regulating diacylglycerol and phosphatidic acid contents that affected the expression of Pi transporters. Our study highlights the role of OsMGD3 in affecting both internal P utilization and P acquisition in rice.

Distinct responses of aerobic granular sludge sequencing batch reactors to nitrogen and phosphorus deficient conditions

The nutrients availability determines efficiency of biological treatment systems, along with the structure and metabolism of microbiota. Herein nutrients deficiencies on aerobic granular sludge were comparatively evaluated, treating wastewater with mass ratios of chemical oxygen demand : nitrogen : phosphorus being 200:20:4, 200:2:4, and 200:20:0.4 (deemed as nutrient-balanced, nitrogen-deficient, and phosphorus-deficient), respectively. Results revealed that both nitrogen and phosphorus deficiencies significantly raised the effluent qualities especially nitrogen removal. However, nitrogen deficiency aroused considerable growth of filamentous bacteria, while granules kept compact structure under phosphorus deficient condition. Extracellular polymeric substances (EPS) also varied in contents and structures in response to different wastewaters. Microbial community structure analysis demonstrated that nitrogen deficiency led to lower richness and higher diversity, while the reverse was observed under phosphorus deficient condition. Nitrogen deficiency mainly induced decrease of nitrifying bacteria, while similarly phosphorus deficiency led to loss of phosphorus accumulating organisms. Dramatic enrichment Candidatus_Competibacter and filamentous Thiothrix were found under nutrients deficiencies, in which the latter explained and indicated filamentous bulking potential especially under nitrogen limited condition. Bacterial metabolism patterns verified the functions of microbial community responding to nutrients via PICRUSt2 prediction mainly by up-regulating cell motility, and cellular processes and signaling. This study could aid understanding of long-term stability of aerobic granular sludge for low-strength wastewater treatment.

Remodeling and protecting the membrane system to resist phosphorus deficiency in wild soybean (Glycine soja) seedling leaves.

The poor-soil-tolerant wild soybean resist phosphorus deficiency by remodeling membrane lipids to reuse phosphorus. The plants synthesize phenolic acids and flavonoids to remove reactive oxygen species and protect membrane stability. Poor soil largely limits plant yields, and the development and utilization of high-quality wild plant resources is an effective approach to resolving this problem. Two ecotypes of wild soybean were used as experimental materials in this experiment. We integrated metabolomics and transcriptomics to determine whether wild soybean (Glycine soja) could resist phosphorus deficiency by remodeling and protecting its membrane system. Under phosphorus-deficient conditions, the plant height and aboveground fresh and dry weight of poor-soil-tolerant wild soybean seedlings were less inhibited than those in common wild soybean. In poor-soil-tolerant wild soybean seedling leaves, the glycerol-3-phosphate content decreased significantly, while caffeic acid, ferulic acid, shikimic acid, phenylalanine, tyrosine, and tryptophan increased significantly. β-Glucosidase and chalcone synthase genes and those that encode SQD2, a crucial enzyme in thiolipid biosynthesis, were specifically up-regulated, whereas the glucosyltransferase UGT74B1 gene was down-regulated. The poor-soil-tolerant wild soybean enhanced glycerolipid metabolism to decompose phospholipids and release phosphorus for reuse to improve resistance to phosphorus deficiency. The plants synthesized thiolipids to replace phospholipids and maintain membrane structure integrity and inhibited glucosinolate biosynthesis to promote phenylpropanoid biosynthesis, leading to the production of phenolic acids and flavonoids that removed reactive oxygen species and protected membrane system stability. The experiments evaluated and provided insight into the innovative utilization of wild soybean germplasm resources.