Limited Nutrient Availability Research Articles

Distinct ecological niches and community dynamics: understanding free-living and particle-attached bacterial communities in an oligotrophic deep lake.

Oligotrophic deep-water lakes are unique and sensitive ecosystems with limited nutrient availability. Understanding bacterial communities within these lakes is crucial for assessing ecosystem health, biogeochemical cycling, and responses to environmental changes. In this study, we investigated the seasonal and vertical dynamics of both free-living (FL) and particle-attached (PA) bacteria in Lake Fuxian, a typical oligotrophic deep freshwater lake in southeast China. Our findings revealed distinct seasonal and vertical dynamics of FL and PA bacterial communities, driven by similar physiochemical environmental factors. PA bacteria exhibited higher α- and β-diversity and were enriched with Proteobacteria, Cyanobacteria, Firmicutes, Patescibacteria, Planctomycetota, and Verrucomicrobiota, while FL bacteria were enriched with Actinobacteria and Bacteroidota. FL bacteria showed enrichment in putative functions related to chemoheterotrophy and aerobic anoxygenic photosynthesis, whereas the PA fraction was enriched with intracellular parasites (mainly contributed by Rickettsiales, Chlamydiales, and Legionellales) and nitrogen metabolism functions. Deterministic processes predominantly shaped the assembly of both FL and PA bacterial communities, with stochastic processes playing a greater role in the FL fraction. Network analysis revealed extensive species interactions, with a higher proportion of positively correlated edges in the PA network, indicating mutualistic or cooperative interactions. Cyanobium, Comamonadaceae, and Roseomonas were identified as keystone taxa in the PA network, underscoring potential cooperation between autotrophic and heterotrophic bacteria in organic particle microhabitats. Overall, the disparities in bacterial diversity, community composition, putative function, and network characteristics between FL and PA fractions highlight their adaptation to distinct ecological niches within these unique lake ecosystems.IMPORTANCEUnderstanding the diversity of microbial communities, their assembly mechanisms, and their responses to environmental changes is fundamental to the study of aquatic microbial ecology. Oligotrophic deep-water lakes are fragile ecosystems with limited nutrient resources, rendering them highly susceptible to environmental fluctuations. Examining different bacterial types within these lakes offers valuable insights into the intricate mechanisms governing community dynamics and adaptation strategies across various scales. In our investigation of oligotrophic deep freshwater Lake Fuxian in China, we explored the seasonal and vertical dynamics of two bacterial types: free-living (FL) and particle-attached (PA). Our findings unveiled distinct patterns in the diversity, composition, and putative functions of these bacteria, all shaped by environmental factors. Understanding these subtleties provides insight into bacterial interactions, thereby influencing the overall ecosystem functioning. Ultimately, our research illuminates the adaptation and roles of FL and PA bacteria within these unique lake environments, contributing significantly to our broader comprehension of ecosystem stability and health.

Productivity and health of soil cultivated with forage cactus (Opuntia cochenillifera (L.) Mill.) with combined use of topsoil and biochar

Agricultural production in semi-arid environments represents a significant challenge, as these are areas that have soils with limited nutrient availability and scarcity of precipitation, which require adaptive and innovative strategies. The application of biochar to improve soil quality and increase productivity has been well studied. However, there is still a gap regarding the use of biochar with the technique of incorporating different topsoils on plant development and soil health. This technique has emerged as an alternative for producers to increase soil fertility. This technique is emerging as an alternative for producers to enhance soil fertility. The hypothesis of the present study is that the use of biochar associated with the topsoil technique increases the productivity and yield of cactus, mainly by changing the properties of the soil and its microbiological interactions. To test this hypothesis, we used different sources of biochar (bean husk, coffee grounds and soursop residue) in association with two types of topsoil (Acrisol and Luvisol). Our analyzes revealed changes on plants development, chemical and microbiological soil attributes. The topsoil technique significantly interfered with mean cladode length (COM), stem diameter (DI), plant height (AL), pH, Na+, K+ and urease enzymatic activity, while biochar had a significant effect on microbial respiration rate. In general, our results expand the knowledge about the use of biochar associated with topsoil, suggesting it as a promising, low-cost way that guarantees the conservation and health of the agroecosystem, contributing with important information for the development of alternative technologies to conventional ones.

Culture of Bovine Aortic Endothelial Cells in Galactose Media Enhances Mitochondrial Plasticity and Changes Redox Sensing, Altering Nrf2 and FOXO3 Levels.

Understanding the complex biological processes of cells in culture, particularly those related to metabolism, can be biased by culture conditions, since the choice of energy substrate impacts all of the main metabolic pathways. When glucose is replaced by galactose, cells decrease their glycolytic flux, working as an in vitro model of limited nutrient availability. However, the effect of these changes on related physiological processes such as redox control is not well documented, particularly in endothelial cells, where mitochondrial oxidation is considered to be low. We evaluated the differences in mitochondrial dynamics and function in endothelial cells exposed to galactose or glucose culture medium. We observed that cells maintained in galactose-containing medium show a higher mitochondrial oxidative capacity, a more fused mitochondrial network, and higher intercellular coupling. These factors are documented to impact the cellular response to oxidative stress. Therefore, we analyzed the levels of two main redox regulators and found that bovine aortic endothelial cells (BAEC) in galactose media had higher levels of FOXO3 and lower levels of Nrf2 than those in glucose-containing media. Thus, cultures of endothelial cells in a galactose-containing medium may provide a more suitable target for the study of in vitro mitochondrial-related processes than those in glucose-containing media; the medium deeply influences redox signaling in these cells.

Skeletal muscle p53-depletion uncovers a mechanism of fuel usage suppression that enables efficient energy conservation.

The ability of skeletal muscle to respond adequately to changes in nutrient availability, known as metabolic flexibility, is essential for the maintenance of metabolic health and loss of flexibility contributes to the development of diabetes and obesity. The tumour suppressor protein, p53, has been linked to the control of energy metabolism. We assessed its role in the acute control of nutrient allocation in skeletal muscle in the context of limited nutrient availability. A mouse model with inducible deletion of the p53-encoding gene, Trp53, in skeletal muscle was generated using the Cre-loxP-system. A detailed analysis of nutrient metabolism in mice with control and knockout genotypes was performed under ad libitum fed and fasting conditions and in exercised mice. Acute deletion of p53 in myofibres of mice activated catabolic nutrient usage pathways even under ad libitum fed conditions, resulting in significantly increased overall energy expenditure (+10.6%; P=0.0385) and a severe nutrient deficit in muscle characterized by depleted intramuscular glucose and glycogen levels (-62,0%; P<0.0001 and -52.7%; P<0.0001, respectively). This was accompanied by changes in marker gene expression patterns of circadian rhythmicity and hyperactivity (+57.4%; P=0.0068). These metabolic changes occurred acutely, within 2-3days after deletion of Trp53 was initiated, suggesting a rapid adaptive response to loss of p53, which resulted in a transient increase in lactate release to the circulation (+46.6%; P=0.0115) from non-exercised muscle as a result of elevated carbohydrate mobilization. Conversely, an impairment of proteostasis and amino acid metabolism was observed in knockout mice during fasting. During endurance exercise testing, mice with acute, muscle-specific Trp53 inactivation displayed an early exhaustion phenotype with a premature shift in fuel usage and reductions in multiple performance parameters, including a significantly reduced running time and distance (-13.8%; P=0.049 and -22.2%; P=0.0384, respectively). These findings suggest that efficient nutrient conservation is a key element of normal metabolic homeostasis that is sustained by p53. The homeostatic state in metabolic tissues is actively maintained to coordinate efficient energy conservation and metabolic flexibility towards nutrient stress. The acute deletion of Trp53 unlocks mechanisms that suppress the activity of nutrient catabolic pathways, causing substantial loss of intramuscular energy stores, which contributes to a fasting-like state in muscle tissue. Altogether, these findings uncover a novel function of p53 in the short-term regulation of nutrient metabolism in skeletal muscle and show that p53 serves to maintain metabolic homeostasis and efficient energy conservation.

Intersection of the microbiome and immune metabolism in lupus.

Systemic lupus erythematosus is a complex autoimmune disease resulting from a dysregulation of the immune system that involves gut dysbiosis and an altered host cellular metabolism. This review highlights novel insights and expands on the interactions between the gut microbiome and the host immune metabolism in lupus. Pathobionts, invasive pathogens, and even commensal microbes, when in dysbiosis, can all trigger and modulate immune responses through metabolic reprogramming. Changes in the microbiota's global composition or individual taxa may trigger a cascade of metabolic changes in immune cells that may, in turn, reprogram their functions. Factors contributing to dysbiosis include changes in intestinal hypoxia, competition for glucose, and limited availability of essential nutrients, such as tryptophan and metal ions, all of which can be driven by host metabolism changes. Conversely, the accumulation of some host metabolites, such as itaconate, succinate, and free fatty acids, could further influence the microbial composition and immune responses. Overall, mounting evidence supports a bidirectional relationship between host immunometabolism and the microbiota in lupus pathogenesis.

Contribution of livestock to organic agriculture: Modelling nitrogen flows at the national scale

Organic agriculture (OA) is the promoted sustainable agriculture model in the European Union (EU), yet its expansion is hindered by limited nutrient availability, particularly nitrogen (N). OA's main sources of N include biological N fixation by legume crops and manure from both conventional and organic livestock. However, potential stricter EU regulations on allowed external N resources for OA and pressure to reduce livestock numbers could impact N availability in OA. Understanding national-scale N flows is essential. Here, we analysed N flows in organic agri-food systems in France, the largest OA area in Europe. We show that approximately 20 % of the manure used to fertilise organic cropland came from conventional agriculture and 15 % from the dietary N nutritional requirements of organic livestock imported from outside France. N surplus is half that of the conventional agriculture at national scale. This first national assessment highlights biophysical and regulatory constraints providing insights into the possibilities of achieving the EU's target of having 25 % of agricultural land under OA.

Vigna marina as a Potential Leguminous Cover Crop for High Salinity Soils

The beach bean (Vigna marina) exhibits robust growth in habitats characterised by sandy substrates, limited nutrient availability, and elevated saline levels. The utilisation of V. marina, a potentially beneficial leguminous cover crop, allows for its cultivation in regions characterised by soil salinity, hence facilitating the alleviation of environmental stress and the promotion of nitrogen fixation within the soil. A study assessed the feasibility of V. marina as a leguminous cover crop, in which this legume was cultivated in both coastal and inland soils. Pueraria javanica and Mucuna bracteata, widely recognised as established leguminous cover crops, were used as the control in this experiment. The observations involved were total plant biomass, nitrogenase activity, and leaf chlorophyll content of the host plants. The experiment consisted of five replicates arranged in a randomised complete block design, respectively. The effects of commercialised rhizobial compost on the development of the leguminous plants planted in both plots were also investigated. The results indicated that V. marina flourished in coastal and inland soils with the highest leaf chlorophyll concentration throughout the eight weeks of growth. It showed that V. marina has the potential to outperform the other two established leguminous cover crops when planted in highly salinised soils. The results also showed evidence that V. marina was an excellent potential leguminous cover crop, especially for any agricultural plots of high salinity soils, compared to the other two well-established leguminous cover crops, P. javanica and M. bracteata.

Unveiling the Potential Scope of Nanoparticles in the Current Era of Crop Productivity

Nanotechnology, a revolutionary field encompassing the manipulation of matter on an atomic or molecular scale, holds immense potential for upgrading wide areas, including agriculture. Understanding the scope of nanotechnology, researchers have directed their focus towards addressing the challenges in agriculture and enhancing crop productivity. Nanoparticles offer unique properties, including high surface area and reactivity, that can be harnessed to optimize nutrient delivery, mitigate soil toxicity, and enhance plant growth. Various studies have demonstrated the effectiveness of nanoparticles in increasing crop yields, improving nutrient uptake efficiency, and reducing environmental impacts associated with conventional agricultural practices with sustainable agriculture. Nanotechnology overcomes various challenges encountered in traditional agricultural practices including limited availability of nutrients in the soil, inefficient nutrient uptake by plants, soil degradation, and environmental pollution by providing targeted nutrient delivery, improving nutrient absorption, and mitigating environmental impacts. Also, nanoparticle interactions with plants and microbes and strengthening symbiotic relationships by providing active nutrient supplies to microbes. Furthermore, nanoparticles can improve soil structure and fertility by reducing compaction, increasing water retention, and enhancing soil aggregation. These improvements in soil quality not only benefit crop growth but also contribute to sustainable land management practices.This review paper provides an overview of the current research landscape in the application of nanoparticles in agriculture, highlighting key findings, challenges, and future prospects. By leveraging the principles of nanotechnology, agricultural scientists and practitioners aim to revolutionize crop production, meet the needs of farmers, and ensure food security in the face of evolving environmental and socio-economic challenges.

Exploring LHCSR3 expression and its role in Chlamydomonas reinhardtii under osmotic stress: Implications for non-photochemical quenching mechanism

Plants have a protective mechanism called non-photochemical quenching to prevent damage caused by excessive sunlight. A critical component of this mechanism is energy-dependent quenching (qE). In Chlamydomonas reinhardtii, the protein expression called light-harvesting complex stress-related protein 3 (LHCSR3) is crucial for the qE mechanism. LHCSR3 expression is observed in various conditions that result in photooxidation, such as exposure to high light or nutrient deprivation, where the amount of captured light surpasses the maximum photosynthetic capacity. Although the role of LHCSR3 has been extensively studied under high light (HL) conditions, its function during nutrient starvation remains unclear. In this study, we demonstrate that LHCSR3 expression can occur under light intensities below saturation without triggering qE, particularly when nutrients are limited. To investigate this, we cultivated C. reinhardtii cells under osmotic stress, which replicates conditions of nutrient scarcity. Furthermore, we examined the photosynthetic membrane complexes of wild-type (WT) and npq4 mutant strains grown under osmotic stress. Our analysis revealed that LHCSR3 expression might modify the interaction between the photosystem II core and its peripheral light-harvesting complex II antennae. This alteration could potentially impede the transfer of excitation energy from the antenna to the reaction center.

Culture Shock! Investigating the Importance of Physiological Tumour-Like Conditions on Cultured Cancer Cells

The tumour microenvironment (TME) is complex and dynamic, characterized by poor vascularization, limited nutrient availability, hypoxia, and an acidic pH. This environment plays a critical role in cancer progression, driving hallmark changes in cancer cell metabolism, morphology, proliferation, and motility. Although mammalian cell culture is a foundational tool for investigating cancer cell biology in vitro, standard cell culture practices fall short of replicating the in vivo conditions of tumours. Recently, ‘physiologic’ cell culture media that closely resemble human plasma (e.g., Plasmax, HPLM) have been developed, along with more frequent adoption of physiological oxygen conditions (2-8% O2) rather than standard atmosphere (~18% O2). Although an improvement, these conditions are not representative of all in vivo cellular environments, particularly that of the TME. Considering the tight regulatory capacity of cancer cells to sense and respond to changes in metabolic availability, we hypothesized that alterations in nutrient and oxygen availability, even if within the physiological range, may subtly rewire the metabolism in cultured cancer cells. This may necessitate further refinement of cell-specific physiologic culture conditions to better maintain the in vivo biology of cells. In this study, we directly address this hypothesis by describing the development of a tumour microenvironment-like medium (TMEM) based on metabolomic profiling of murine pancreatic ductal adenocarcinoma tumour interstitial fluid from relevant literature. We found that murine pancreatic ductal adenocarcinoma (KPCY) cells cultured under TME-like conditions (TMEM, pH 7.0, 1.5% O2) exhibited increased glucose uptake and lactate production rates compared to those cultured under healthy plasma-like conditions (Mouse Plasma-like Medium, pH 7.4, 5% O2), despite lower initial glucose concentrations in TMEM (2.3 mM vs. 4.4 mM in Mouse Plasma-like Medium). Moreover, cell proliferation rates were lower in TMEM, suggesting an overall reduction in ATP consumption fueling cell division. Seahorse Extracellular Flux Analysis is being performed to determine effects on cellular bioenergetics. Metabolomic amino acid uptake using LCMS is also being performed to further assess the effect of TMEM on nutrient utilization. Using RNA-sequencing, we showed that culture in TMEM increased expression of genes associated with angiogenesis, amino acids biosynthesis, cell migration, and endothelial-to-mesenchymal transition. Migration assays confirmed increased motility in KPCY cells cultured in TMEM. Taken together, these results demonstrate that growth in a medium designed to simulate the TME alters KPCY cell biology in ways that are relevant to their pathology, which highlights the significance of maintaining TME-like conditions in culture. This research was funded by a Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant from JAS and a NSERC Canadian Graduate Student (Masters) Grant awarded to GLG. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Testing Alternative Hydroponic Nutrition of Wick System on Vegetable Growth Planted in Limited Land

This research aims to obtain suitable alternative nutrients for vegetable cultivation using the Hydroponic Wick System so that the production costs of hydroponic cultivation can be cheaper and more affordable. The research was conducted in the Tebeng area, Ratu Agung Kodya Bengkulu, at an elevation of 50 meters above sea level. The research method used was a Randomized Block Design with a Factorial pattern (RAKF). The first factor had 3 levels of vegetable types: kailan (S1), caisim (S2), and pakcoy (S3). The second factor had 3 levels of nutrients: AB Mix 100% (N1), alternative 100% (N2), and ABMix 50% + alternative 50% (N3). Thus, there were 9 treatment combinations with 3 replications. The results of the research showed that the plant height, number of leaves, wet weight, and dry weight of plants using Alternative Nutrients for kailan, caisim, and pakcoy vegetables significantly influenced the use of AB Mix nutrients, Alternative Nutrients, and the mixture of both nutrients when grown using the Hydroponic Wick system. The best results were achieved using alternative nutrients. This was evident from the tallest plant height at harvest, which was 34.20 grams at 42 days after planting (HST), 16.62 leaves, 142.69 grams wet weight, and 7.60 grams dry weight. These results were significantly better compared to using other nutrients, offering a potential solution to the high costs of hydroponic cultivation due to the expensive price and limited availability of AB Mix nutrients, especially in the region.

Enhancing cotton (Gossypium hirsutum L.) productivity and quality with magnetized ionized water and Bacillus subtilis intervention under film-mulched drip irrigation in saline soil in Xinjiang

ContextSoil salinity stress and limited nutrient availability significantly impede crop production. Addressing these challenges, the activation of irrigation water and soil enhancement strategies have proven increasingly effective in improving crop production in saline soils. In particular, magnetized ionized water technology has been shown to augment the leaching of soil salinity, while Bacillus subtilis has been applied to increase nutrient availability. However, information on the synergistic effects of magnetized ionized water and B. subtilis are presently limited. ObjectiveThis study aimed to investigate the potential of utilizing B. subtilis in combination with magnetized ionized water to enhance cotton (Gossypium hirsutum L.) production and understand its underlying driving mechanism. MethodsA two-year field experiment explored the impact of varying amounts of B. subtilis, with two types of irrigation water [non-magnetized-ionized water (NMIW) and magnetized ionized water (MIW)] on soil conditions (pH, salt accumulation, and nutrient content), and cotton growth (dry matter, nutrient accumulation, seed cotton yield, and quality) in southern Xinjiang's saline soil. The experiment included five B. subtilis levels (0, 15, 30, 45, and 60 kg ha−1) with NMIW (designated as B0, B1, B2, B3, and B4) and MIW (designated as MB0, MB1, MB2, MB3, and MB4). ResultsMIW and B. subtilis significantly (p < 0.05) reduced soil pH and salt accumulation, while B. subtilis significantly (p < 0.01) increased soil residual nitrate nitrogen and residual available phosphorus content in the 0–40 cm soil layers compared to B0. Furthermore, a significant increase (p < 0.05) in cotton dry matter, nitrogen, and phosphorus accumulation was observed with both measures compared to B0. Seed cotton yield (Y), water productivity (WP), and fiber quality index (FQI) also showed significant improvements (p < 0.05). Compared with the NMIW treatments, the MIW treatments resulted in an average increase in Y of 5.7%, WP of 3.7%, and FQI of 20.2%. Similarly, B. subtilis treatments, compared to no B. subtilis treatments, led to an average increase in Y by 10.6%, WP by 6.9%, and FQI by 29.1%. Quadratic function relationships with Y, WP, and FQI were established using B. subtilis amount as an independent variable. The appropriate range of B. subtilis amount under MIW treatment, corresponding to 99.5% of the maximum values of Y, WP, and FQI, was determined to be 51.1–56.4 kg ha−1. ConclusionMIW and B. subtilis have been found to increase nutrient accumulation in cotton by reducing 0–40 cm soil salinity and alkalinity and increasing 0–40 cm soil nutrient content, thereby enhancing cotton production. To optimize the cotton cultivation under film-mulched drip irrigation in saline soil of southern Xinjiang, China, it is recommended to apply 51.1–56.4 kg ha−1B. subtilis under MIW.

Analisis Kandungan Hara N, P, dan K pada Perbedaan Lahan yang Ditanami Karet dan Kelapa Sawit

The general obstacles in cultivating rubber and oil palm are soil acidity and limited availability of nutrients, especially N, P, and K. These nutrients play an important role in the growth of rubber and oil palm plants. Knowing the nutrient content is necessary to be able to determine the management that needs to be carried out. The objective of this study is to determine differences in the nutrient content of N, P, and K on various lands planted with rubber and oil palm plants. Soil sample analysis was conducted in the laboratory for available N, available P, and available K. To determine differences in land use for the elements N, P and K, data were analyzed using an unpaired two sample t test. The results showed differences in available K and available P levels between the two land types, while no differences were observed in N availability between the two land types. This variation may be caused by differences in land management practices.

Climate Variability and Glacier Dynamics Linked to Fjord Productivity Changes Over the Last ca. 3300 Years in Nuup Kangerlua, Southwest Greenland

AbstractGreenlandic fjords, located between the ice sheet and the ocean, are dynamic systems that can sustain highly variable levels of primary productivity and are sensitive to climate change. In our current climate trajectory, meltwater discharge is expected to significantly increase but its long‐term effects on fjord productivity are still poorly constrained. Paleo‐archives can offer valuable insights into long‐term effects. Here, we present two marine sediment core records from Nuup Kangerlua, Southwest Greenland. Our goal is to better understand to what extent, and on what time‐scales, climate fluctuations and associated glacier dynamic changes have impacted fjord productivity over the past ca. 3300 years. Our multiproxy records include diatom fluxes and assemblage composition, sediment biogeochemistry, and grain‐size distribution. Our study reveals that fjord productivity is tightly linked to regional climate variability; relatively higher productivity levels coincided with mild climate periods whereas the climate cooling of the last millennium led to a decrease in productivity. The diatom records suggest that lower productivity is associated with shorter or less intense summer blooms, increased sea‐ice cover and/or a stratified water column. Diatom assemblages demonstrate cold sea‐surface conditions around 1600 CE that might be linked to local advance of glaciers. Cold conditions and decreasing productivity culminated at 1850 CE, when glaciers in the fjord retreated and high glacial meltwater discharge would have altered the fjord hydrography, likely leading to limited nutrient availability. Our long‐term records support the idea that changing climate and cryosphere conditions have a non‐linear impact on the productivity of Greenlandic fjords.

Examining avascular tumour growth dynamics: A variable-order non-local modelling perspective

This study investigates the growth of an avascular tumour described through the interchange of mass among its constituents and the production of inelastic distortions induced by growth itself. A key contribution of this research examines the role of non-local diffusion arising from the complex and heterogeneous tumour micro-environment. In our context, the non-local diffusion is enhanced by a variable-order fractional operator that incorporates crucial information about regions of limited nutrient availability within the tissue. Our research also focuses on the identification of an evolution law for the growth-induced inelastic distortions recast through the identification of non-conventional forces dual to suitable kinematic descriptors associated with the growth tensor. The establishment of such evolution law stems from examining the dissipation inequality and subsequently determining a posteriori connections between the inelastic distortions and the source/sink terms in the mass balance laws. To gain insights into the dynamics of tumour growth and its response to the proposed modelling framework, we first study how the variables governing the tissue evolution are affected by the introduction of the new growth law. Second, we investigate how regions of limited diffusion within the tumour, encoded into a fractional operator of variable-order, influence its growth.

Response of the growth and survival of tree species planted in a degraded land with a supplement of diammonium phosphate (DAP) fertilizer

AbstractDegraded lands pose significant challenges for tree establishment and growth due to poor soil quality and limited nutrient availability. This research aims to explore the potential of using DAP (diammonium phosphate) fertilizer as a supplement for enhancing the survival and growth of tree species in degraded lands; Casuarina equisetifolia L., Grevillea robusta var. robusta R.Br., and Olea europaea subsp. cuspidata (Wall. &amp; G. Don). To achieve the objectives, seedlings of the species were planted in degraded land using a randomized complete block design (RCBD), with a supplement of DAP fertilizer. Six replications, each consisting of 20 seedlings, were used for each of the species with the DAP treatment. The survival and growth data were collected from January 2015 to May 2022. One‐way ANOVA, t‐test, and mean survival percentage were used for data analysis. The results revealed that the mean final survival percentage of C. equisetifolia that received DAP fertilizer (73.6%) was higher than that of C. equisetifolia without fertilizer (44.4%). The statistical t‐test also showed significant differences between the mean survival percentages of C. equisetifolia planted with a supplement of DAP and without fertilizer (p = 0.033). The mean survival percentage of O. europaea and G. robusta, whether fertilized or not, was poor (0%–7%). The one‐way ANOVA result showed significant differences in both fertilized and unfertilized seedlings among the C. equisetifolia, G. robusta, and O. europaea species (p &lt; 0.001). The dry biomass of C. equisetifolia grown with a supplement of DAP fertilizer and the unfertilized was 15.4 kg/tree and 11.2 kg/tree. The t‐test result revealed no significant differences in the dry biomass of the C. equisetifolia grown with a supplement of DAP fertilizer and without fertilizer. Finally, it is concluded that the effect of DAP fertilizer on the growth and survival of the species is species‐specific.

Seasonal variations in C/N/P/K stoichiometric characteristics in different plant organs in the various forest types of Sygera Mountain.

We explored the resource acquisition and growth strategies of plants adapting to different environments, focusing on the typical forest types of Sygera Mountain: Pinus armandii, Picea likiangensis var. Linzhiensis, Abies georgei var. Smithii, and Juniperus saltuaria. Then, we analyzed the nutrient content and stoichiometric ratios of C, N, P, and K in different plant organs (leaves, branches, trunks, and roots) to examine the stoichiometric characteristics and nutrient balance mechanisms in these forests. Results show that within the same forest type, different plant organs exhibit high C and low N, P, and K levels. N content in all organs followed the order leaves > branches > roots > trunks. During the growth phase, the concentrations of P and K in PLL and AGS follow the order branches > leaves > roots > trunks. In the dormant phase, the distribution in different organs had the order leaves > branches > roots > trunks. C content remained relatively stable over time. In the same organ across different forest types, increase in nitrogen content in plant leaves is an active adaptation of JS plants, indicating that JS has a conservative growth strategy and can adapt to environmental stress. Owing to the influence of seasons, the evolution process of N and P content fluctuates, allocating nutrients to supporting and transporting organs for resource optimization and allocation. The N and P content were lower in the growth phase than in the dormant phase. Seasonal variations in the C/N, C/P, and C/K ratios in different forests were inversely correlated with changes in N, P, and K content in plant organs, supporting the "growth rate hypothesis." Stoichiometric analysis suggests that different limiting elements exist in organs across various forest types. Principal component analysis indicates that the seasonal patterns of stoichiometric ratios in the organs of different forest types show species-specific characteristics, reflecting the evolutionary nutrient utilization strategies of plant genera. In summary, plant growth in different Sygera Mountain forest types is limited by N and P, with a high tendency toward nitrogen limitation. The nutrient utilization and distribution differences among various organs during different growth stages are primarily influenced by the limited availability of environmental nutrients and inherent physiological characteristics of the plants.

An iron fist in a velvet glove: The cooperation of a novel pyoverdine from Pseudomonas donghuensis P482 with 7-hydroxytropolone is pivotal for its antibacterial activity.

Pseudomonas donghuensis P482 exhibits broad antimicrobial activity against phytopathogens, including the soft rot bacteria of the Dickeya genus. Here, we report that under limited nutrient availability, the antibacterial activity of P. donghuensis P482 against Dickeya solani requires the reciprocal action of two iron scavengers: 7-hydroxytropolone (7-HT) and a newly characterized pyoverdine (PVDP482 ) and is quenched in the iron-augmented environment. Further, we show that the biosynthesis of pyoverdine and 7-HT is metabolically coordinated, and the functional BV82_4709 gene involved in 7-HT synthesis is pivotal for expressing the BV82_3755 gene, essential for pyoverdine biosynthesis and vice versa. The synthesis of both scavengers is under the control of Gac/Rsm, but only PVD is controlled by Fur. The isoelectric focusing profile of the P482 siderophore differs from that of the other Pseudomonas spp. tested. This finding led to the unveiling of the chemical structure of the new pyoverdine PVDP482 . To summarize, the antibacterial activity of P. donghuensis P482 is attributed to 7-HT and PVDP482 varies depending on the nutrient and iron availability, highlighting the importance of these factors in the competition between P482 and D. solani.

Antimicrobial Activity Screening of Bacteria Isolated from Tasik Cermin

Introduction: With the emergence of the multi-drug resistant bacteria that threaten the human health, novel antimicrobial compounds from natural environment have been increasingly explored. Tasik Cermin is a lake completely covered by karst towers and hills and lacks any inflow or outflow of water making it an oligotrophic environment with limited nutrient availability. Increased competition among microorganisms leads to production of antimicrobial compounds that can inhibit the growth of its competitor. Thus, the aim of this study is to assess antimicrobial activity of bacterial isolates from Tasik Cermin and identify the most resistant isolate. Methods: The isolates were tested against five test bacteria: Staphylococcus aureus, Bacillus subtilis, Streptococcus pneumoniae, Escherichia coli, and Proteus vulgaris by primary screening through perpendicular streak method, secondary screening followed by MIC and MBC and the most resistant bacteria was identified by molecular identification. Results: The result indicates that only one isolate (Isolate TC1A) was able to show potential antimicrobial activity against P. vulgaris and S. pneumoniae. This isolate was further tested by secondary screening through agar well diffusion method and inhibition zone were observed on P. vulgaris (14.97 ± 0.05), E. coli (9.23 ± 0.25) and S. pneumoniae (14.93 ± 0.12). Statistical analysis by One-Way ANOVA and Tukey test method indicates that inhibition zone of E. coli is significantly different as compared to S. pneumoniae and P. vulgaris. Molecular identification revealed that the isolate TC1A was identified as Achromobacter sp. with 97.68% similarity percentage. Conclusion: This finding shows that bacterial isolates from under-explored areas have the potential of producing novel antimicrobial compounds.

Unlocking the potential of elemental sulfur autotrophic denitrification through inorganic nutrient optimization

Elemental sulfur packed-bed (S0PB) bioreactors are increasingly employed to treat secondary effluents from wastewater treatment plants. Limited availability of inorganic nutrients, such as ammonium, phosphate, and inorganic carbon, significantly determines the growth of autotrophic microorganisms and the denitrification efficiency. This study investigated the constraining thresholds of inorganic nutrients on the elemental sulfur autotrophic denitrification process. In the absence of ammonium, phosphate, and bicarbonate, the denitrification rate decreased. Specifically, the ammonium assimilation process could be replaced by nitrate assimilation pathways, resulting in a 29.5 % decline in denitrification efficiency when the ammonium-N feed was reduced from 2.0 to 0 mg-N/L. However, the absence of phosphate-P and bicarbonate-C led to substantial drops in denitrification efficiency by 66.7 % and 77.5 %, respectively. This was primarily attributed to diminished biomass yield, as evidenced by reductions of 77.8–82.6 % in ATP and 35.7–44.3 % in protein content, along with a 12.4 %–14.7 % decrease in the relative abundances of dominant sulfur-oxidizing bacteria. Correlation analyses established specific thresholds for desired nitrate removal amounts: 0.131 for ammonium-N, 0.053 for phosphate-P, and 0.597 for bicarbonate-C. These thresholds provided valuable guidance for adjusting real-life wastewater through external supplementation when employing a pilot-scale S0PB bioreactor, leading to a significant enhancement of denitrification efficiency. This study emphasizes the significance of considering the concentrations of inorganic nutrients in wastewater when implementing S0PB bioreactors, which is a context that frequently neglects potential negative consequences.