Nitrogen Limitation Research Articles

The Spatial Dynamics of Diazotrophs in the Forefield of Three Tibetan Glaciers.

Nitrogen is often a limiting nutrient for microbial communities and plants in glacier forefields. Nitrogen-fixing microorganisms (diazotrophs) play an important role in providing bioavailable nitrogen, with their composition determining the nitrogen-fixating capacities. This study investigates the spatial and temporal dynamics of diazotrophs in the forefields of three Tibetan glaciers: Qiangyong, Kuoqionggangri, and Longxiazailongba. We collected soil samples from recently deglaciated barren grounds, and also along an ecosystem succession transect at Kuoqionggangri glacier, encompassing barren ground, herb steppe, legume steppe, and alpine meadow ecosystems. Our finding revealed abundant and diverse diazotrophs in the recently deglaciated barren ground. They are taxonomically affiliated with anaerobic Bradyrhizobium, Desulfobulbus, and Pelobacter, which may be relics from subglacial sediments. The vegetated soils (herb steppe, legume steppe, and alpine meadow) were dominated by phototrophic Nostoc and Anabaena, as well as symbiotic Sinorhizobium. Soil physicochemical parameters, such as soil organic carbon, pH, and nitrate ion, significantly influenced diazotroph community structure. This study highlights the critical role of diazotrophs in mitigating nitrogen limitation during early ecosystem development in glacier forefields. Understanding the distribution and ecological drivers of diazotrophs in these rapidly changing environments provides insights into biogeochemical cycling and ecosystem resilience under climate change.

Coral larvae increase nitrogen assimilation to stabilize algal symbiosis and combat bleaching under increased temperature.

Rising sea surface temperatures are increasingly causing breakdown in the nutritional relationship between corals and algal endosymbionts (Symbiodiniaceae), threatening the basis of coral reef ecosystems and highlighting the critical role of coral reproduction in reef maintenance. The effects of thermal stress on metabolic exchange (i.e., transfer of fixed carbon photosynthates from symbiont to host) during sensitive early life stages, however, remains understudied. We exposed symbiotic Montipora capitata coral larvae in Hawai'i to high temperature (+2.5°C for 3 days), assessed rates of photosynthesis and respiration, and used stable isotope tracing (4 mM 13C sodium bicarbonate; 4.5 h) to quantify metabolite exchange. While larvae did not show any signs of bleaching and did not experience declines in survival and settlement, metabolic depression was significant under high temperature, indicated by a 19% reduction in respiration rates, but with no change in photosynthesis. Larvae exposed to high temperature showed evidence for maintained translocation of a major photosynthate, glucose, from the symbiont, but there was reduced metabolism of glucose through central carbon metabolism (i.e., glycolysis). The larval host invested in nitrogen cycling by increasing ammonium assimilation, urea metabolism, and sequestration of nitrogen into dipeptides, a mechanism that may support the maintenance of glucose translocation under thermal stress. Host nitrogen assimilation via dipeptide synthesis appears to be used for nitrogen limitation to the Symbiodiniaceae, and we hypothesize that nitrogen limitation contributes to retention of fixed carbon by favoring photosynthate translocation to the host. Collectively, our findings indicate that although these larvae are susceptible to metabolic stress under high temperature, diverting energy to nitrogen assimilation to maintain symbiont population density, photosynthesis, and carbon translocation may allow larvae to avoid bleaching and highlights potential life stage specific metabolic responses to stress.

Improving the biodiesel production in the marine diatom Thalassiosira pseudonana cultivated in nutrient deficiency and sewage water.

The use of microalgae as a feedstock in biofuel production is highly encouraging. The marine diatom in this study, Thalassiosira pseudonana, was used as a test organism to evaluate the impact of nitrogen or phosphorus limitation and sewage water on improving biodiesel production. The growth rate is more affected in cultures without phosphorus by 41.8% lower than in control and the highest dry weight estimated in control. The cellular dry weight significantly increased in cultures treated with mix1 and mix2 wastewater compared to the control cultures. Chlorophyll a content decreased in the absence of nitrogen and phosphorous and in sewage water cultures. Lipid content in algal cultures without nitrogen or phosphorus and in sewage water accumulated nearly twice as much lipid content in synthetic medium. T. pseudonana showed high FAME contents; the two most abundant fatty acids, stearic acid (C18:0) and palmitoleic acid (C16:1), in the algal extracts revealed that T. pseudonana was predominantly composed of these fatty acids. T. pseudonana grown in nitrogen or phosphorus-deficient conditions exhibited an extreme percentage of saturated fatty acids (SFAs) by 87.38% and 85.47%, respectively, of the total fatty acids (TFAs). More importantly, the low polyunsaturated fatty acid content in oils indicates a high cetane number, low iodine value, and low corrosion for biodiesel quality indicators. Producing biodiesel that closely meets worldwide biodiesel requirements (ASTM D6751 and EN 14214) is the goal of this work, which shows that growing T. pseudonana under nutrient limitations leads to algal metabolism in that direction.

Acclimation of Photosynthesis to CO2 Increases Ecosystem Carbon Storage due to Leaf Nitrogen Savings.

Photosynthesis is the largest flux of carbon between the atmosphere and Earth's surface and is driven by enzymes that require nitrogen, namely, ribulose-1,5-bisphosphate (RuBisCO). Thus, photosynthesis is a key link between the terrestrial carbon and nitrogen cycle, and the representation of this link is critical for coupled carbon-nitrogen land surface models. Models and observations suggest that soil nitrogen availability can limit plant productivity increases under elevated CO2. Plants acclimate to elevated CO2 by downregulating RuBisCO and thus nitrogen in leaves, but this acclimation response is not currently included in land surface models. Acclimation of photosynthesis to CO2 can be simulated by the photosynthetic optimality theory in a way that matches observations. Here, we incorporated this theory into the land surface component of the Energy Exascale Earth System Model (ELM). We simulated land surface carbon and nitrogen processes under future elevated CO2 conditions to 2100 using the RCP8.5 high emission scenario. Our simulations showed that when photosynthetic acclimation is considered, photosynthesis increases under future conditions, but maximum RuBisCO carboxylation and thus photosynthetic nitrogen demand decline. We analyzed two simulations that differed as to whether the saved nitrogen could be used in other parts of the plant. The allocation of saved leaf nitrogen to other parts of the plant led to (1) a direct alleviation of plant nitrogen limitation through reduced leaf nitrogen requirements and (2) an indirect reduction in plant nitrogen limitation through an enhancement of root growth that led to increased plant nitrogen uptake. As a result, reallocation of saved leaf nitrogen increased ecosystem carbon stocks by 50.3% in 2100 as compared to a simulation without reallocation of saved leaf nitrogen. These results suggest that land surface models may overestimate future ecosystem nitrogen limitation if they do not incorporate leaf nitrogen savings resulting from photosynthetic acclimation to elevated CO2.

Nitrogen Stress Memory in Quinoa: Maternal Effects on Seed Metabolism and Offspring Growth and Physiology.

Plants have developed various strategies to deal with abiotic stresses throughout their lifetimes. However, environmental stresses can have long-lasting effects, positively modifying plant physiological responses to subsequent stress episodes, a phenomenon known as preconditioning or stress memory. Intriguingly, this memory can even be transmitted to offspring, referred to as "inter- or transgenerational memory". Chenopodium quinoa is a pseudocereal that can withstand several abiotic stresses, including nitrogen (N) limitation. This research highlights the critical role of maternal N conditions in shaping the physiological and metabolic responses of their offspring. Mother quinoa plants (F0) were grown under High N (HN) or Low N (LN) conditions. LNF0 plants exhibited lower panicle biomass, net photosynthesis, and yield compared to HNF0 plants. Seeds from LNF0 retained proteins, reduced amino acids' levels, and increased lipids (such as PI 34:2), especially phosphatidylcholines, and their unsaturation level, which was associated with faster germination compared to HNF0 seeds. Offsprings seedlings (F1) grown under either HN or LN had similar proteins and amino acid proportions of their seeds. However, LNF0LNF1 seedlings displayed significantly higher biomass and number of root tips. These changes were significantly correlated with transpiration, net photosynthesis, and stomatal conductance, as well as with starch content, suggesting higher CO2 fixation at the whole plant level in LNF0LNF1 plants. Our findings suggest that quinoa transmits maternal environmental stress information to its offspring, modulating their resilience. This work underscores the potential of utilizing maternal environmental conditions as a natural priming tool to enhance crop resilience against nutritional stress.

Production of Biomass and Lipid Yields of Chlorella sp. Cultivated in Autotrophic and Mixotrophic Media

In this work, we analyze the biomass and lipid yields of Chlorella sp., when it grows in synthetic wastewater with and without nitrogen limitation and in both cases, adding glucose to both medium, autotrophic and mixotrophic. Our results confirm that it is possible to expand their possibilities of use, which range from their use for the bioremediation of bodies of water to obtaining various biofuels due to their high content of lipids and carbohydrates. It was identified that both the biomass and lipids were higher in the media with mixotrophy with 535.71 mg L-1 and 244.60 mg L-1, respectively. Similarly, the importance of nitrogen present in the growth medium was recognized as a determining variable for the accumulation of lipids in the species, while it is concluded that the use of Chlorella sp. eliminates a significant percentage of nitrogen and phosphorus present in wastewater, thereby reducing nutrient contamination. The nutrient stress to which the microalgae were subjected allowed a greater accumulation of lipids in the cells, which leads to the conclusion that in a large-scale study, Chlorella sp. It could be used as a raw material to obtain oils and their subsequent transformation into biodiesel.

Engineering Halomonas bluephagenesis for synthesis of polyhydroxybutyrate (PHB) in the presence of high nitrogen containing media

The trade-offs exist between microbial growth and bioproduct synthesis including intracellular polyester polyhydroxybutyrate (PHB). Under nitrogen limitation, more carbon flux is directed to PHB synthesis while growth is inhibited with diminishing overall carbon utilization, similar to the suboptimal carbon utilization during glycolysis-derived pyruvate decarboxylation. This study reconfigured the central carbon network of Halomonas bluephagenesis to improve PHB yield theoretically and practically. It was found that the downregulation of glutamine synthetase (GS) activity led to a synchronous improvement on PHB accumulation and cell growth under nitrogen non-limitation condition, increasing the PHB yield from glucose (g/g) to 85% of theoretical yield, PHB titer from 7.6 g/L to 12.9 g/L, and from 51 g/L to 65 g/L when grown in shake flasks containing a rich N-source, and grown in a fed-batch cultivation conducted in a 7-L bioreactor also containing a rich N-source, respectively. Results offer better metabolic balance between glucose conversion efficiency and microbial growth for economic PHB production.

Contrasting Supply Dynamics of Dissolved Iron and Nitrate Shape the Biogeography of Nutrient‐Limiting Conditions in the North Pacific

AbstractThe North Pacific is known with iron limitation for phytoplankton growth in the subarctic region and nitrogen limitation in the subtropical gyre. Although the growth rate of phytoplankton is determined by the concentration of limiting nutrient, the supply ratio of iron to nitrogen is suggested to be essential to this biogeographic pattern. However, the underlying dynamics determining the ratio remain largely unknown. We investigated mechanisms of dissolved iron (dFe) and nitrate (NO3−) transport to the euphotic zone of the North Pacific using an eddy‐resolvable biogeochemical model. We show that lateral advection and atmospheric deposition are dominant drivers for dFe transport, resulting in high Fe:N supply ratio in both subarctic and subtropical regions. Conversely, significant vertical supplies of NO3− through upwelling and diffusion processes markedly reduce the supply ratio in the subarctic region. These dynamics combined lead to high Fe:N supply ratio in the gyre and low ratio in the subarctic, ultimately driving high nitrogen fixation condition in the gyre and the iron‐limited phytoplankton growth condition in the subarctic region.

Microbial necromass in soil profiles increases less efficiently than root biomass in long-term fenced grassland: Effects of microbial nitrogen limitation and soil depth

Grassland fencing is acknowledged as a crucial initiative to enhance biodiversity and to increase soil organic carbon (SOC) content in ecologically fragile regions or barren systems. Theoretical perspectives propose that fencing induced an increase in root biomass, and its penetration into the soil profile introduced organic matter that facilitated SOC formation through microbial necromass and root residues. It is hypothesized that long-term grassland fencing increases root biomass, thereby enhancing SOC formation within the soil profile through microbial residues in badland ecosystems. To test this hypothesis, we selected grasslands subjected to varying durations of fencing post-grazing (i.e., 10, 15, 20, 30, and 40 y). Our investigation aimed to clarify microbial necromass dynamics in 0–100 cm soil profiles after fencing and to identify the influencing factors. Long-term grassland fencing (i.e., >30 y) increased root biomass by 160 %, SOC by 69 %, and necromass by 41 % compared to grazed grassland within the 0–40 cm horizon; in contrast, increased root biomass by 870 %, SOC by 111 %, and necromass by 46 % in the 40–100 cm horizon. Necromass in deep soil (40–100 cm) accounted for about 50 % of total residues in the 0–100 cm profile. Increased root and living microbial biomass stimulated the necromass accumulation, with a more pronounced increase in fungal residues compared with bacterial residues. Nonetheless, microbial nutrient limitation increases C or N-acquisition enzyme coefficients, which subsequently reduced fungal and bacterial residues and stimulated their recycling. Despite substantial increases in root biomass within the soil profile after fencing, limitation of microbial N and depth reduced the effectiveness of enhancing SOC and necromass. In conclusion, although microbial residues were the important source of SOC in grasslands of the Loess Plateau, microbial N limitation impeded necromass accumulation, and the interplay of root biomass, soil depth, and nutrient limitation regulated the dynamics of necromass following grassland fencing.

Refining habitat selection for sulfate-reducing bacteria: Evaluating suitability and adaptability for sulfate-metal wastewater treatment during anaerobic-to-aerobic transitions

Inoculating sulfate-reducing bacteria (SRB) habitats offers an eco-friendly method for treating sulfate-metal laden wastewater, characterized by high sulfate levels, low pH, and elevated heavy metals. This study optimizes source habitat selection of SRB by evaluating groundwater, sewage sludge, and lake sediment, focusing on their suitability and adaptability to aerobic-anaerobic transitions in industrial settings. Sewage sludge, with its slightly acidic pH, reducing environment, and high nutrient levels (Total organic carbon: 207.53 g kg−1, Total nitrogen: 47.12 g kg−1), provides robust SRB potential, as supported by its highest diversity index. However, heavy metals and polycyclic aromatic hydrocarbons pose application challenges. All habitats effectively reduced metal concentrations anaerobically, with Cu removal reaching 95%–99%, and groundwater achieved the highest chemical oxygen demand reduction (63.6%) aerobically. Sludge and sediment showed high biomass and extracellular polymeric substances (EPS) accumulation, while groundwater's nucleic acid-rich EPS enhanced metal immobilization, resulting in stable residual metal forms but with potential remobilization under oxidative conditions. Microbial analysis revealed that Proteobacteria and Firmicutes were key players during transitions, with the highest SRB abundance in groundwater. SRB composition varied across habitats, with Sedimentibacter (13.04%), Desulfovibrio (6.33%), and Desulfomonile (8.1%) dominating in groundwater, sludge, and sediment, respectively, during the anaerobic stage. Functional analysis highlighted sludge's persistence in sulfate reduction under aerobic conditions, while groundwater's limited nitrogen cycle involvement indicated broader biogeochemical limitations. Collectively, these findings highlight strengths and limitations of each habitat as SRB inoculum source, emphasizing the importance of tailored anaerobic-to-aerobic strategies for effective wastewater management.

The GCN4 Transcription Factor: A Review of Its Functional Progress in Fungi

Nitrogen serves as a pivotal nutrient for the proliferation, maturation, and pathogenicity of fungi. Despite its importance, nitrogen starvation is a common challenge encountered during fungal development and host invasion. A key regulatory transcription factor, known as general control non-derepressible 4 (GCN4), has been characterized in various fungal groups, including model fungal, pathogens, and basidiomycetes. This factor is triggered by nitrogen limitation and subsequently stimulates the expression of a multitude of genes involved in amino acid synthesis, thereby countering the effects of nitrogen deficiency. This paper provides a comprehensive review on the activation mechanisms, the structural characteristics and stability of GCN4, and how GCN4 activates its downstream target genes to regulate the physiological processes of fungi. This study lays the theoretical groundwork for future research endeavors that seek to enhance nitrogen utilization, preserve the delicate balance of carbon–nitrogen metabolism, and stimulate growth, development, and secondary metabolism in fungi, especially under nitrogen-limited conditions.

Responses of soil properties and foliar traits of a dominant tree species Pseudotsuga sinensis to rocky desertification in a karst ecosystem

Rocky desertification is a prevalent environmental challenge across karst landscapes that hinders regional sustainable development. Understanding how soil properties and plant traits respond to increasing levels of rocky desertification is crucial for developing effective restoration strategies. Here, we investigated soil characteristics and intraspecific leaf stoichiometric traits of Pseudotsuga sinensis across a gradient of rocky desertification in a karst ecosystem. We employed principal component analysis to assess changes in soil properties and leaf chemical traits and used leaf trait network analysis to explore shifts in trait network topology. Our results revealed that severe desertification sites had soil with high bulk density and pH, and low levels of available nitrogen, phosphorus, magnesium, as well as soil organic carbon. Leaf stoichiometry shifted markedly along the gradient, with elevated nitrogen limitation and cation imbalance in degraded sites. Trait network analysis showed that network diameter and modularity increased while connectance decreased with rocky desertification, indicating reduced integration among traits. On the other hand, higher adaptation capacity to environmental harshness under moderate level of rocky desertification was also observed. These findings suggest that both soil properties and leaf traits would experience substantial shifts across rocky desertification gradient, with increasing functional fragmentation and nutrient limitation as degradation intensifies. Based on our results, we propose management strategies targeted to different levels of rocky desertification to mitigate its negative impacts and promote ecosystem recovery.

Characteristics and Drivers of Soil Carbon, Nitrogen, and Phosphorus Ecological Stoichiometry at the Heavy Degradation Stage of the Alpine Meadow

An in-depth understanding of the soil nutrient status and balance relationship can help the effective recovery and management of alpine degraded meadows. In order to study the balance relationship among soil carbon, nitrogen, and phosphorus nutrients during the heavy degradation stage of meadows, field sampling and investigation, indoor analysis, and mathematical statistics were used to explore the characteristics and driving factors of changes in soil carbon, nitrogen, and phosphorus content, storage, and ecological stoichiometry during the heavy degradation stage of alpine meadows in the Sanjiangyuan region. The results showed that in the heavy degradation stage, miscellaneous grass plants occupied absolute dominance, soil C∶N∶P was approximately 32.83∶3.87∶0.67, and there was certain nitrogen limitation. The coefficients of variation of soil carbon, nitrogen, and phosphorus content were in the following order： organic carbon （1.09） > total nitrogen （0.63） > total phosphorus （0.29）. The organic carbon content and the carbon and nitrogen ratio showed a significant linear decreasing trend with the increase in the grassland degradation index （GDI）, while the total phosphorus content and organic carbon storage showed a significant non-linear change, in which the total phosphorus content showed a significant gentle U-shaped distribution, and the organic carbon storage decreased more gently at the beginning of the heavy degradation stage and then decreased sharply when the GDI was 57.9. The results of Mantel correlation analysis showed that the soil carbon to nitrogen ratio, carbon to phosphorus ratio, and nitrogen to phosphorus ratio showed significant correlation with organic carbon content and storage and total nitrogen storage. The results of structural equation modeling indicated that soil water content had direct effects as well as indirect through vegetation factors, soil carbon, nitrogen, and phosphorus ecological stoichiometry ratios, and soil water content and vegetation factors （height, cover, and biomass） were key environmental factors affecting soil ecological stoichiometry. The research results can provide scientific basis and practical guidance for the restoration of heavily degraded grassland in alpine meadows.

Uncovering the small proteome of Methanosarcina mazei using Ribo-seq and peptidomics under different nitrogen conditions

The mesophilic methanogenic archaeal model organism Methanosarcina mazei strain Gö1 is crucial for climate and environmental research due to its ability to produce methane. Here, we establish a Ribo-seq protocol for M. mazei strain Gö1 under two growth conditions (nitrogen sufficiency and limitation). The translation of 93 previously annotated and 314 unannotated small ORFs, coding for proteins ≤ 70 amino acids, is predicted with high confidence based on Ribo-seq data. LC-MS analysis validates the translation for 62 annotated small ORFs and 26 unannotated small ORFs. Epitope tagging followed by immunoblotting analysis confirms the translation of 13 out of 16 selected unannotated small ORFs. A comprehensive differential transcription and translation analysis reveals that 29 of 314 unannotated small ORFs are differentially regulated in response to nitrogen availability at the transcriptional and 49 at the translational level. A high number of reported small RNAs are emerging as dual-function RNAs, including sRNA154, the central regulatory small RNA of nitrogen metabolism. Several unannotated small ORFs are conserved in Methanosarcina species and overproducing several (small ORF encoded) small proteins suggests key physiological functions. Overall, the comprehensive analysis opens an avenue to elucidate the function(s) of multitudinous small proteins and dual-function RNAs in M. mazei.

Impact of Nitrogen Limitation, Irrigation Levels, and Nitrogen-Rich Biostimulant Application on Agronomical and Chemical Traits of Hydroponically Grown Cichorium spinosum L.

Impact of Nitrogen Limitation, Irrigation Levels, and Nitrogen-Rich Biostimulant Application on Agronomical and Chemical Traits of Hydroponically Grown Cichorium spinosum L.

A mycoheterotrophic orchid uses very limited soil inorganic nitrogen in its natural habitat

Mycoheterotrophic plants acquire nitrogen (N) directly from the soil and through their symbiotic fungi. The fungi-derived N has received considerable attention, but the contribution of soil-derived N has been largely overlooked. We investigated how the leafless, rootless, and almost mycoheterotrophic orchid Cymbidium macrorhizon obtains soil N by applying 15N-labeled ammonium nitrate in its natural habitat, and tracking metabolite accumulation and mycorrhizal fungal association after N application. The decline of N in the rhizome from flowering to fruiting indicated a transfer of N from the rhizome to fruits. At current dose of N application (0.6 g NH4NO3 each plant), only 1.5% of the plant's N was derived from fertilizer, resulting in a low nitrogen use efficiency of 0.27%. The majority of those newly absorbed N (88.89%) was found sank in the rhizome. Amino acids (or their derivatives) and alkaloids were predominant differentially accumulated nitrogenous metabolites after N application, with amino acids occurring in both fruits and the rhizome, and alkaloids primarily in the fruits. The addition of N did not alter the richness of mycorrhizal fungi, but did affect their relative abundance. Our findings suggest that Cymbidium macrorhizon uses very limited soil inorganic nitrogen in its natural habitat, and the root-like rhizome primarily stores N rather than absorbs its inorganic forms, offering new insights into how mycoheterotrophic plants utilize soil N, and the influence of nutrient availability on the orchid-fungi association.

Nutrient depletion and phytoplankton shifts driven by the Pearl River plume in the Taiwan Strait

The intrusion of the Pearl River plume into the Taiwan Strait provides a unique case study that challenges traditional assumptions about the impacts of nutrient-rich river plumes on coastal phytoplankton communities. In this study, we conducted a detailed analysis of nutrient dynamics and phytoplankton composition within the Taiwan Strait, focusing on the effects of the Pearl River plume. Our findings reveal significant nutrient depletion, particularly of nitrogen, in the surface waters as the plume extends seaward, resulting in nitrogen limitation and a marked reduction in phytoplankton biomass. Vertical stratification within the Taiwan Strait creates distinct ecological niches, with the mid-layer supporting a deep chlorophyll maximum and the surface layer becoming dominated by the picophytoplankton Synechococcus. This shift from diatom-dominated communities to Synechococcus dominance has far-reaching implications for carbon cycling and food web dynamics in the region. Our results suggest that the Pearl River plume’s influence on the Taiwan Strait represents a departure from the typical nutrient enrichment associated with river plumes, highlighting the complexity of coastal biogeochemical processes.

Mycelial mass, microbial lipids and γ-linolenic acid (GLA) by Cunninghamella elegans cultivated on agro-industrial residues

In the current study, the Zygomycetes fungus Cunninghamella elegans NRRL Y-1392 was evaluated for its ability to grow in extracts derived from dried and ground agricultural residues, such as mushroom stalks and roots from hydroponically cultivated lettuces and produce poly-unsaturated fatty acids (PUFA) and γ-linolenic acid (GLA) rich lipids. Initially, the compositions of stalks and lettuce roots were analysed, and the fungus was batch-flask cultivated on six different commercial semi-defined substrates containing different sugars detected in stalks and roots to evaluate its catabolic ability. C. elegans was capable to assimilate all sugars, but at a lower rate in the case of arabinose. Subsequently, C. elegans was cultivated on tailor-made semi-defined commercial substrates, resembling hydrolysates containing carbohydrates found in mushroom stalks, under both nitrogen-excess and nitrogen-limited conditions, and resembling that of hydrolysates of roots, under nitrogen-excess conditions. Based on the results, under nitrogen-excess conditions, in the case of media resembling stalks hydrolysates, higher production values for biomass, PUFAs, and GLA were observed (20.3 g/L, 1906 mg/L, 668 mg/L), accompanied by high productivity values due to short cultivation periods, while under nitrogen limitation, high lipid accumulation (lipid in dry cell weight =48%, w/w) was presented, and lipids rich in oleic acid were produced. Finally, the fungus was cultivated on a medium derived from hot water-extraction applied to mushroom stalks, enriched with organic nitrogen sources. The fungus was successfully grown on the sugar-rich water-extract derived from mushroom stalks, resulting in dry biomass of 14.5 g/L, lipids of 1.8 g/L, with 15% (w/w) of GLA in cellular lipids.

The legacy effects of mycorrhizal fungal inoculation alleviate soil nitrogen limitations by modulating the homeostasis of extracellular enzymes and fungal function in arid mining regions

AbstractRe‐vegetation types and the application of arbuscular mycorrhizal fungi (AMF) play a crucial role in regulating soil conditions and enhancing vegetation cover during ecological restoration in the northern arid mining area. However, the impact of AMF on the balance of soil–plant–microbial ecosystems through its influence on microbial activities remains unclear. Therefore, we studied the influence of AMF on soil nutrient limitation and the soil fungal community in five different vegetation types in the Daliuta reclamation area. Through the measurement of soil extracellular enzyme activity and the analysis of soil fungal communities by high‐throughput sequencing, we found that the ratio of lnBG:ln(NAG + LAP):lnAP in the AMF sample was closer to 1:1:1, and the soil ecological enzyme stoichiometry was more balanced. The results of enzyme vector showed that AMF inoculation could alleviate the restriction of soil nitrogen nutrients. The results of high‐throughput sequencing showed that AMF improved the diversity of soil fungal community by regulating the composition of soil fungal community, and finally alleviated the nitrogen restriction during decomposition. Functional prediction of soil fungi using FUNGuild indicated that the soil fungi present were mainly saprophytic, saprophytic–symbiotic, and pathotroph–saprophytic–symbiotic trophic types. AMF reduced the percentage of pathotroph fungi and also tended to transform saprophytic into saprophytic–symbiotic type. The findings suggest that mycorrhizal reclamation can enhance the homeostasis of extracellular enzyme dynamics by optimizing fungal community structure and modulating fungal functionality, thereby alleviating microbial nutrient constraints and improving plant adaptability to arid environments. This article provides a theoretical underpinning for eco‐friendly mining construction and sustainable ecological development in arid mining areas.

The evaluation of Starmerella magnoliae X3 as a biodiesel feedstock based on triacylglycerol (TAG) production, lipid productivity, and fatty acid profile under nitrogen limitation and acidic pH conditions.

The effects of four initial culture pH values (3, 4, 5, and 6) and nitrogen limitation on growth, TAG accumulation, lipid production, fatty acid profile, and estimated biodiesel quality of Starmerella magnoliae X3 were investigated. TAG and lipid levels were measured by Nile Red fluorescence and sulfo-phospho-vanilin (SPV) techniques, respectively. The results showed that a combination of nitrogen limitation and acidic pH significantly (p < 0.05) increased TAG accumulation, total lipid contents, and lipid productivity in Starmerella magnoliae X3 compared to the control group. Under nitrogen limitation, the highest TAG accumulation was achieved at initial pHs of 3 and 5 after 72h of cultivation, and the highest lipid productivity (0.306g L-1 d-1) was observed after 48h at pH 3; the major fatty acids at the four pH values were oleic acid (63.6%-64%), palmitoleic acid (11.3%-12.5%), stearic acid (9.7%-11.4%), and palmitic acid (9.4%-10%). In addition, both stresses were associated with lower iodine value and higher cetane number of the biodiesel compared to the control. These findings suggest that cultivation in a low-nitrogen medium at an initial pH of 3 or 5 holds promise in increasing TAG production in Starmerella magnoliae X3.