Nutrient Metal Research Articles

Declining nutrient availability and metal pollution in the Red Sea

Reconstructing sediment accumulation rates reveals historical environmental shifts. We analyzed 15 element concentrations and accumulation rates in two Red Sea sediment cores over 500 years. Post-1870s, the South Red Sea experienced a significant drop in element accumulation rates, with a noticeable decline in nutrients like magnesium (−8.52%), organic carbon (−14.9%), nitrogen (−14.0%), phosphorus (−16.4%), sulfur (−17.2%), and calcium (−17.8%). This suggests a potential reduction in nutrient inflow from the Indian Ocean, possibly due to warming-induced ocean stratification. Conversely, the North Red Sea saw an increase in all element accumulation rates after the 1870s, highlighting a rise in trace elements such as iron (4.56%), cadmium (8.69%), vanadium (12.6%), zinc (13.8%), copper (14.4%), chromium (17.6%), and nickel (19.5%), indicative of increased anthropogenic coastal activities. We introduce the term “Cai-Agusti Marine Crisis Conflux” to encapsulate the escalating thermal stress, nutrient depletion, and elemental pollution in the Red Sea, underscoring potential risks to its ecosystems and global implications.

Patterns of accumulation and baseline values for metals in agricultural soils from a copper mining region in southern Peru

As global copper demand surges, it's vital to conduct a thorough analysis of metal concentrations in the agricultural soils of mining districts. This is especially pertinent for the Andean region, where, in the face of clear soil degradation, there's a notable lack of in-depth research. This study is the first attempt to characterize variations in the concentration of 17 metals in the agricultural soils of Moquegua – a region with a long history of mining activity that contributes significantly to Peru's position as the world's second-largest producer of copper. The surface horizons of 336 agricultural soils under vegetable crops were sampled between 9 and 3,934 m above sea level (m.a.s.l.) to determine the total content of metal nutrients (MNs) (Ca, Mg, K, Na, Fe, Cu, Mn, Zn) and heavy metals (HMs) (Cd, Cr, Ni, Pb, As, Co, Ba, V, Al) by inductively coupled plasma-optical emission spectrometry (ICP-OES). The accumulation of metals was found to increase with altitude. The study identified hotspots with a high concentration of metals and spatial patterns in their geographic distribution. The observed median values for As (70.9 mg/kg), Cd (7.1 mg/kg), and Pb (89.7 mg/kg) represent the highest metal concentrations among the identified clusters. Notably, these values surpass the Environmental Quality Standards (ECA) set for agricultural soils in Peru. As there are no local standards for all the metals studied, our results can serve as reference values for guiding land management practices, particularly in the context of copper mining.

The influence of a copper efflux pump in Histoplasma capsulatum virulence.

During the infectious process, pathogenic microorganisms must obtain nutrients from the host in order to survive and proliferate. These nutritional sources include the metallic nutrient copper. Despite its essentiality, copper in large amounts is toxic. Host defense mechanisms use high copper poisoning as a fungicidal strategy to control infection. Transcriptional analyses showed that yeast cultured in the presence of copper or inside macrophages (24 h) had elevated expression of CRP1, a copper efflux pump, suggesting that Histoplasma capsulatum could be exposed to a high copper environment in macrophages during the innate immune stage of infection. Accordingly, macrophages cultured in high copper are more efficient in controlling H. capsulatum growth. Also, silencing of ATP7a, a copper pump that promotes the copper influx in phagosomes, increases fungal survival in macrophages. The rich copper environment faced by the fungus is not dependent on IFN-γ, since fungal CRP1 expression is induced in untreated macrophages. Appropriately, CRP1 knockdown fungal strains are more susceptible to macrophage control than wild-type yeasts. Additionally, CRP1 silencing decreases fungal burden in mice during the phase of innate immune response (4-day postinfection) and CRP1is required for full virulence in a macrophage cell lines (J774 A.1 and RAW 264.7), as well as primary cells (BMDM). Thus, induction of fungal copper detoxifying genes during innate immunity and the attenuated virulence of CRP1-knockdown yeasts suggest that H. capsulatum is exposed to a copper-rich environment at early infection, but circumvents this condition to establish infection.

Local staples, and global solutions: optimizing the effect of traditional fermentation on heavy metals and mineral nutrients

PurposeThis study aims to examine the effect of traditional fermentation on gari’s total heavy metal and mineral nutrient content.Design/methodology/approachThis study used a quantitative approach, descriptive-analytical design to baseline the risk of heavy metals and experimental design to assess the effect of traditional fermentation. Data were analyzed using descriptives, univariate and multivariate analysis.FindingsAlthough gari is rich in mineral nutrients (total calcium 3.9 ± 0.1 g/kg, copper 5.5 ± 0.02 mg/kg, iron 97.1 ± 5.8 mg/kg, potassium 9.1 ± 0.29 g/kg and zinc 3.4 ± 0.11 mg/kg), the significant levels of heavy metals (total arsenic 1.2 ± 0.01, cadmium 2.5 ± 0.04, lead 1.7 ± 0.01, mercury 2.8 ± 0.01 and tin 1.7 ± 0.02 mg/kg) present are a cause for concern. The results further suggested that traditional fermentation has reductive effects on some heavy metals and stabilizing or concentrating effects on mineral nutrients.Research limitations/implicationsThis paper provides evidence that traditional fermentation may have exploitable differential effects on heavy metal contaminants and mineral nutrients that should be further explored.Practical implicationsThise study reports fermentation implications for mitigating food with high heavy metal contaminants with minimal nutrient loss.Originality/valueThis study fulfills an identified need to optimize traditional fermentation to ensure food safety and nutrient security.

Fetoplacental Disposition and Toxicity of Cadmium in Mice Lacking the Bcrp Transporter.

The environmental toxicant cadmium (Cd) impairs the growth of rodents and humans in utero which in turn heightens susceptibility to diseases later in life. We previously demonstrated that the maternal-facing efflux transporter, breast cancer resistance protein (human BCRP/ABCG2, mouse Bcrp/Abcg2) confers resistance against Cd toxicity in human trophoblasts. In the current study, we sought to determine whether the absence of Bcrp alters the fetoplacental disposition and toxicity of Cd in mice. Pregnant female wild-type (WT) and Bcrp-null mice (n = 9-10/group) were administered a single injection of saline (5 ml/kg) or CdCl2 (5 mg/kg) on gestational day (GD) 9. Following Cd treatment, Bcrp-null offspring were shorter and accumulated more Cd in their placentas on GD 17 compared to WT mice. Because Cd can adversely impact placentation and transplacental nutrient delivery in mice, multiple pathways were assessed using morphometrics and immunohistochemistry including placenta zonation, vasculature development, and nutrient transporter expression. Most notably, the placentas of Bcrp-null mice had reduced immunostaining of the cell adhesion marker, β-catenin, and the trophoblast marker, cytokeratin, as well as decreased expression of divalent metal nutrient transporters (Dmt1, Zip14, and ZnT1) following Cd treatment. In summary, the absence of Bcrp expression increased placental concentrations of Cd which was associated with shorter fetal size that may be related to differential changes in molecular patterns of placental development and nutrition.

Supplementation of strigolactone analog for enhancing the removal of nutrient and heavy metal by microalgae-fungi symbionts

The purification effects of Chlorella vulgaris and Chlorella vulgaris-Clonostachys symbionts on nutrients and heavy metals in wastewater were investigated to determine the optimal symbiotic treatment technology and the suitable concentration of GR24. The results showed that exogenous GR24 not only promoted the formation of uniform green spheres in microalgae-fungi symbionts, but also increased its photosynthetic performance and growth. At 10−7 M GR24 addition concentration, the specific growth rate of microalgae-fungi symbionts was 0.367 ± 0.04 d−1, the maximum removal efficiency of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) were 81.96 ± 7.93 %, 80.26 ± 7.91 % and 82.96 ± 8.05 %, respectively. When the concentration of exogenous GR24 was 10−5 M, the removal efficiency of heavy metals was the best at both low and high pollution levels. It was worth noting that the removal efficiency of Zn at low concentration pollution levels (1 mg L−1) was 99.32 ± 0.43 %, nearly 100 %. This study promoted the development of microalgae-fungal symbionts in the field of wastewater treatment.

Two related families of metal transferases, ZNG1 and ZNG2, are involved in acclimation to poor Zn nutrition in Arabidopsis.

Metal homeostasis has evolved to tightly modulate the availability of metals within the cell, avoiding cytotoxic interactions due to excess and protein inactivity due to deficiency. Even in the presence of homeostatic processes, however, low bioavailability of these essential metal nutrients in soils can negatively impact crop health and yield. While research has largely focused on how plants assimilate metals, acclimation to metal-limited environments requires a suite of strategies that are not necessarily involved in metal transport across membranes. The identification of these mechanisms provides a new opportunity to improve metal-use efficiency and develop plant foodstuffs with increased concentrations of bioavailable metal nutrients. Here, we investigate the function of two distinct subfamilies of the nucleotide-dependent metallochaperones (NMCs), named ZNG1 and ZNG2, that are found in plants, using Arabidopsis thaliana as a reference organism. AtZNG1 (AT1G26520) is an ortholog of human and fungal ZNG1, and like its previously characterized eukaryotic relatives, localizes to the cytosol and physically interacts with methionine aminopeptidase type I (AtMAP1A). Analysis of AtZNG1, AtMAP1A, AtMAP2A, and AtMAP2B transgenic mutants are consistent with the role of Arabidopsis ZNG1 as a Zn transferase for AtMAP1A, as previously described in yeast and zebrafish. Structural modeling reveals a flexible cysteine-rich loop that we hypothesize enables direct transfer of Zn from AtZNG1 to AtMAP1A during GTP hydrolysis. Based on proteomics and transcriptomics, loss of this ancient and conserved mechanism has pleiotropic consequences impacting the expression of hundreds of genes, including those involved in photosynthesis and vesicle transport. Members of the plant-specific family of NMCs, ZNG2A1 (AT1G80480) and ZNG2A2 (AT1G15730), are also required during Zn deficiency, but their target protein(s) remain to be discovered. RNA-seq analyses reveal wide-ranging impacts across the cell when the genes encoding these plastid-localized NMCs are disrupted.

Cascade dams altered taxonomic and functional composition of bacterioplankton community at the regional scale.

Dams are increasingly disrupting natural river systems, yet studies investigating their impact on microbial communities at regional scale are limited. Given the indispensable role of bacterioplankton in aquatic ecosystems, 16S rRNA gene sequencing was performed to explore how these communities respond to dam-influenced environmental changes at the regional scale in the Shaying River Basin. Our findings revealed that cascade dams create distinct environments, shaping bacterioplankton communities near the dams differently from those in natural rivers. In the upstream of the cascade dams, water quality was superior, while bacterioplankton community structure was simple with weak community interactions. In the midstream, nutrient and heavy metal content were increased, making bacterioplankton structures more susceptible to environmental changes. In the downstream of the cascade dams, water quality had a significant impact on the community and the bacterioplankton structures were highly complex. Additionally, environmental variables significantly influenced bacterioplankton functional groups. However, the response to these factors, as well as the interplay between functional and taxonomic diversity, varied markedly depending on the specific region of the cascade dams. We here delved into the effects of cascade dams on the taxonomic diversity and functional groups of bacterioplankton to provide a theoretical basis for segmentally regulating these dams.

Mechanistic insights into synergistic facilitation of copper/zinc ions and dewatered swine manure-derived biochar on anaerobic digestion of swine wastewater

Biochar-assisted anaerobic digestion (AD) has been proposed an advanced system for swine wastewater (SW) management. However, the effects of metallic nutrients in SW, such as copper/zinc ions (Cu2+/Zn2+), on the biochar-assisted AD of SW are not well understood. This study investigated the influences of individual Cu2+/Zn2+ or dewatered swine manure-derived biochar, as well as their combined additions, on the AD of SW. The results showed that exposure to 50 mg/L Cu2+/Zn2+ temporary inhibited methane production, but the addition of 20 g/L biochar alleviated this inhibition by shortening the methanogenic lag time and increasing methane yield. Following a period of acclimation, both Cu2+/Zn2+ and biochar promoted methane production, although metagenomic analysis revealed distinct mechanisms underlying their promotion. Cu2+/Zn2+ enhanced ATP processing, including electron exchange between NADH/NAD+ and succinate/fumarate transformation, by 26.0–35.8%. Additionally, the gene encoding Coenzyme M methylation was upregulated by 36.2% along with enrichments of Methanocullus and Methanosarcina, contributing to accelerated hydrolysis and methanogenesis rates by 54.7% and 44.8%, respectively. On the other hand, biochar mainly stimulated bacterial F-type ATPase activities by 28.4%, likely facilitating direct interspecies electron transfer between Geobacter and Methanosarcina for syntrophic methanogenesis. The combined addition of Cu2+/Zn2+ and biochar resulted in “win-win” benefits, significantly increasing the maximum methane production rate from 40.3 mL CH4/d to 53.7 mL CH4/d. Moreover, the introduction of biochar into AD of SW facilitated the transformation of more Cu2+/Zn2+ from a reducible Fe–Mn oxides form to a residual form, which potentially reduced the metallic toxicity of the digestate for soil amendment. The findings of this study provide novel insights into understanding the synergistic impacts of heavy metals and biochar in regulating SW during AD, as well as the management of associated digestate.

Nutrient and heavy metal dynamics in the coastal waters of St. Martin’s island in the Bay of Bengal

Seasonal variation observations were conducted in the coastal waters of St. Martin's Island in the Bay of Bengal to examine the influence of physical processes and the distribution pattern of nutrients in the ocean water. Pollution evaluation indices, health index and statistical techniques were incorporated to assess the heavy metal contamination. Two seasons, cool dry winter and pre-monsoon hot, were considered for sampling from 12 stations around the island. The Cool dry winter season has higher nutrient concentrations than the Pre-monsoon Hot season. The concentration of nutrients appeared as follows: Silicate > Nitrate > Ammonia > Phosphate > Nitrite. PCA and Pearson's Correlation showed that fresh water from nearby rivers, deep water upwelling, and, in some situations, modest anthropogenic sources are crucial. Hence, low DO and phosphate levels during the pre-monsoon hot season indicate there is a planktonic process like photosynthesis prevailing. The island's north-western and south-eastern regions have higher nutrient concentrations, which may be seasonal and due to wind action. Pb, Cu, As, Cr, Cd, and Zn were also considered to comprehend the island's geo-chemical perspectives and ecological and human health risks. The Pre-monsoon Heavy Metal Pollution Index (HPI) and Heavy Metal Evaluation Index (HEI) demonstrated that some places are much higher than the threshold limit, even though no significantly higher value was detected in the cool winter season. The Nemerow Index, the Total Ecological Risk Index (TERI), indicated that heavy metal contamination was severe to moderate and low to moderate. Finally, Pearson's correlation showed the association between physical and chemical characteristics, similar to PCA and Pearson's correlation for nutrients and heavy metals. Thus, this research may help shed light on the state of the seas around St. Martin's Island. This study may also provide explicit insights for the authority to take the necessary measures to preserve marine ecology and the associated terrestrial ecosystem.

Inflammation alters iron distribution in bone and spleen in mice.

Anemia of inflammation (or inflammation-associated anemia) decreases the quality of life in billions of patients suffering from various inflammatory diseases, such as infection, autoimmune diseases, and cancer, associated with a prolonged state of immune activation. While proper utilization of iron, a nutrient metal essential for erythropoiesis, is important for the prevention of anemia, the alteration of body iron homeostasis upon inflammation, which can contribute to the development of anemia, is not completely understood. Thus, we sought to examine temporal and spatial changes in the distribution of iron and iron-associated molecules during inflammation in mice. To induce inflammation, C57BL/6J mice were injected with turpentine oil weekly for 3 weeks, which resulted in anemia, decreased protein expression of ferroportin, a cellular iron exporter, in the spleen, duodenum, and liver, and increased iron stores in the duodenum and spleen. Tracer kinetic studies after oral administration of 59Fe revealed that more iron was found in the spleen and less in the femur bone in turpentine oil-injected mice compared to the saline-injected mice, indicating tissue-specific abnormalities in iron distribution during inflammation. However, there was no difference in the utilization of iron for red blood cell production after turpentine oil injection; instead, serum hemopexin level and lactate dehydrogenase activity were increased, suggesting increased red blood cell destruction upon inflammation. Our findings provide an improved understanding of temporal and spatial changes in the distribution and utilization of iron during inflammation.

Drivers and mechanisms of spontaneous plant community succession in abandoned Pb[sbnd]Zn mining areas in Yunnan, China

The drivers and mechanisms underlying succession and the spontaneous formation of plant communities in mining wasteland remain largely unknown. This study investigated the use of nature-based restoration to facilitate the recovery of viable plant communities in mining wasteland. It was found that scientific analyses of spontaneously formed plant communities in abandoned mining areas can provide insights for nature-based restoration. A chronosequence (“space for time”) approach was used to establish sites representing three successional periods with six successional stages, and 90 quadrats were constructed to investigate changes in plant species and functional diversity during succession in abandoned PbZn mining areas. A total of 140 soil samples were collected to identify changes in soil properties, including plant nutrient and heavy metal concentrations. Then, this paper used structural equation models to analyze the mechanisms that drive succession. It was found that the functional diversity of plant communities fluctuated substantially during succession. Species had similar functional traits in early and mid-succession, but traits tended to diverge during late succession. Soil bulk density and soil organic matter gradually increased during succession. Total nitrogen (N), pH, and soil Zn concentrations first increased and then decreased during succession. Concentrations of Mn and Cd gradually decreased during succession. During early succession, soil organic matter was the key factor driving plant colonization and succession. During mid-succession, soil Zn functioned as an environmental filter factor limiting the rates of succession in mining wasteland communities. During late succession, soil bulk density and competition for nutrient resources contributed to more balanced differentiation among plant species. This thesis proposed that a nature-based strategy for the stabilization of abandoned mining lands could facilitate effective plant community restoration that promotes ecosystem services and functioning.

Rhizosphere interface microbiome reassembly by arbuscular mycorrhizal fungi weakens cadmium migration dynamics.

The prevalence of cadmium (Cd)-polluted agricultural soils is increasing globally, and arbuscular mycorrhizal fungi (AMF) can reduce the absorption of heavy metals by plants and improve mineral nutrition. However, the immobilization of the rhizosphere on cadmium is often overlooked. In this study, Glomus mosseae and Medicago sativa were established as symbiotes, and Cd migration and environmental properties in the rhizosphere were analyzed. AMF reduced Cd migration, and Cd2+ changed to an organic-bound state. AMF symbiosis treatment and Cd exposure resulted in microbial community variation, exhibiting a distinct deterministic process (|βNTI| > 2), which ultimately resulted in a core microbiome function of heavy metal resistance and nutrient cycling. AMF increased available N and P, extracellular enzyme activity(LaC, LiP, and CAT), organic matter content (TOC, EOC, and GRSP), and Eh of the rhizosphere soil, significantly correlating with decreased Cd migration (p < 0.05). Furthermore, AMF significantly affected root metabolism by upregulating 739 metabolites, with flavonoids being the main factor causing microbiome variation. The structural equation modeland variance partial analysisrevealed that the superposition of the root metabolites, microbial, and soil exhibited the maximum explanation rate for Cd migration reduction (42.4%), and the microbial model had the highest single explanation rate (15.5%). Thus, the AMF in the rhizosphere microenvironment can regulate metabolite-soil-microbial interactions, reducing Cd migration. In summary, the study provides a new scientific explanation for how AMF improves plant Cd tolerance and offers a sustainable solution that could benefit both the environment and human health.

Seasonal purification efficiency, greenhouse gas emissions and microbial community characteristics of a field-scale surface-flow constructed wetland treating agricultural runoff

Controlling nonpoint source pollution (NPSP) is very important for protecting the water environment, and surface-flow constructed wetlands (SFCWs) have been widely established to mitigate NPSP loads. In this study, the pollutant removal efficiencies, greenhouse gas (GHG) emissions, and chemical and microbial community properties of the sediment in a large-scale SFCW established beside a plateau lake (Qilu Lake) in southwestern China to treat agricultural runoff were evaluated over a year. The SFCW performed best in terms of nitrogen removal in autumn (average efficiency of 63.5% at influent concentrations of 9.3–35.4 mg L−1) and demonstrated comparable efficiency in other seasons (23.7–40.0%). The removal rates of total phosphorus (TP) and chemical oxygen demand (COD) were limited (18.6% and 12.4% at influent concentrations of 1.1 and 45.5 mg L−1 on average, respectively). The SFCW was a hotspot of CH4 emissions, with an average flux of 31.6 mg m−2·h−1; moreover, CH4 emissions contributed the most to the global warming potential (GWP) of the SFCW. Higher CH4 and N2O fluxes were detected in winter and in the front-end section of the SFCW with high pollutant concentrations, and plant presence increased CH4 emissions. Significant positive relationships between nutrient and heavy metal contents in the SFCW sediment were detected. The microbial community compositions were similar in autumn and winter, with Thiobacillus, Lysobacter, Acinetobacter and Pseudomonas dominating, and this distribution pattern was clearly distinct from those in spring and summer, with high proportions of Spirochaeta_2 and Denitratisoma. The microbial co-occurrence network in spring was more complex with stronger positive correlations than those in winter and autumn, while it was more stable in autumn with more keystone taxa. Optimization of the construction, operation and management of SFCWs treating NPSP in lake watersheds is necessary to promote their environmental benefits.

Evaluation of the nutritive value and metal content of prevalent edible mushrooms in Bangladesh

Mushroom cultivation in Bangladesh has been on the rise, however, their nutrient and heavy metal content is not well investigated. Herein, prevalent cultivars and strains of five mushroom species (Pleurotus ostreatus, Pleurotus sajor-caju, Pleurotus citrinopileatus, Auricularia auricula and Ganoderma lucidum) were analyzed for their nutritional values (total ash, lipid, crude fiber, protein and carbohydrates) as well as metal concentrations using standard methods. This study was conducted at the Laboratory of the Biochemistry Department at Sher-e Bangla Agricultural University, Dhaka, Bangladesh, from January to December 2022. The proximate composition of mushrooms varied from 2.67–11.57%, 2.05-3.81%, 15.52-22.61%, 6.1-12.71% and 46.01-57.85% for total ash, lipid, crude fiber, protein and carbohydrates, respectively. The highest values of Fe, Mn, Zn, P, Ca, Mg, K, S and N were 315.87, 19.14, 267.96, 2.92, 1.07, 0.44, 4.62, 0.78 and 3.06 μg/g, respectively. Remarkably, the highest amounts of heavy metals, Pb (5.65 μg/g) and Cd (0.22 μg/g) were found in Pleurotus citrinopileatus, while Cr (3.22 μg/g) and Ni (1.65 μg/g) were found in a variety of Pleurotus ostreatus. The findings revealed that heavy metal concentrations in two mushroom varieties exceeded the maximum permissible limit recommended by WHO/FAO. To the best of our knowledge, this is the first comprehensive analysis comparing the nutritional value and metal content of popular mushroom species of Bangladesh.

Effect of cage culture on sedimentary heavy metal and water nutrient pollution: Case study in Sansha Bay, China

The aquaculture area in China's coastal waters has increased rapidly from 6000 km2 in 1990 to 22,000 km2 in 2020. Despite extensive research regarding the effect of coastal aquaculture on water and sediment pollution, evaluating the quantitative relationship between aquaculture and pollutants remains challenging. Sansha Bay, the world's largest cage aquaculture base for Pseudosciaena crocea, is a typical enclosed bay used for investigating aquaculture pollution. A cage culture database is established from 2000 to 2020 in Sansha Bay. Meanwhile, 236 sediment samples from 3 sediment cores and 67 water samples from 4 transects are obtained from the bay for experiments. The main indicators are five nutrients (NO3−, SiO32−, PO43−, NH4+, and NO2−) in the water samples, the grain size, the heavy metal (Zn, Cu, Pb, Cr, Cd, and As) content, and the 210Pb radioactivity in sediment samples. Based on data obtained and a new calculation method, the annual increment in Zn, Cu, As, Cd, Pb, and Cr contents in the cultured zone is shown to increase by 2137 %, 1881 %, 506 %, 300 %, 202 %, and 118 % in 2000–2018, respectively, as compared with the levels in a noncultured zone. The activities of the cage culture increased NO3− by 9 %, PO43− by 30 %, NH4+ by 115 %, and NO2− by 232 %, compared with natural conservative mixing processes, such as the mixing of SiO32−, in 2020. A novel quantitative approach with broad applicability is proposed to evaluate the magnitude of anthropogenically induced environmental contamination. The effectiveness of the proposed technique is demonstrated through a case study conducted in Sansha Bay, China.

Control of nutrient metal availability during host-microbe interactions: beyond nutritional immunity.

The control of nutrient availability is an essential ecological function of the host organism in host-microbe systems. Although often overshadowed by macronutrients such as carbohydrates, micronutrient metals are known as key drivers of host-microbe interactions. The ways in which host organisms control nutrient metal availability are dictated by principles in bioinorganic chemistry. Here I ponder about the actions of metal-binding molecules from the host organism in controlling nutrient metal availability to the host microbiota. I hope that these musings will encourage new explorations into the fundamental roles of metals in the ecology of diverse host-microbe systems.

Endophyte inoculation enhanced microbial metabolic function in the rhizosphere benefiting cadmium phytoremediation by Phytolaccaacinosa

Microbial metabolic activities in rhizosphere soil play a critical role in plant nutrient utilization and metal availability. However, its specific characteristics and influence on endophyte assisted phytoremediation remains unclear. In this study, an endophyte strain Bacillus paramycoides (B. paramycoides) was inoculated in the rhizosphere of Phytolacca acinosa (P. acinosa), and microbial metabolic characteristics of rhizosphere soils were analyzed using Biolog system to investigate how they influence phytoremediation performance of different types of cadmium contaminated soil. The results indicated that endophyte B. paramycoides inoculation enhanced bioavailable Cd percentage by 9–32%, resulting in the increased Cd uptake (32–40%) by P. acinosa. With endophyte inoculation, the utilization of carbon sources was significantly promoted by 4–43% and the microbial metabolic functional diversity increased by 0.4–36.8%. Especially, B. paramycoides enhanced the utilization of recalcitrant substrates carboxyl acids, phenolic compounds and polymers by 48.3–225.6%, 42.4–65.8% and 15.6–25.1%, respectively. Further, the microbial metabolic activities were significant correlated with rhizosphere soil microecology properties and impact phytoremediation performance. This study provided new insight into the microbial processes during endophyte assisted phytoremediation.

Assessment of the Potentials of Water Hyacinth (Eichhornia crassipes) as Raw Material for Biofertilizer

This research investigated the potentials of water hyacinth as raw material for biofertilizers. Water hyacinth was collected from Alape River in Ilaje Local Government Area of Ondo State and processed for microbiological, proximate and physicochemical analyses by standard methods. Results revealed that the total heterotrophic bacterial and fungal populations were 5.0 x 107 (CFU/g) and 3.5 x 105 (CFU/g) and 3.6 x 102 SFU/g and 3.0 x 102 (SFU/g) for root and leaf parts respectively. The population of phosphate solubilizing bacteria, Azospirillum spp., Azotobacter spp. and Rhizobium spp. were 3.5 x 104 - 1.3 x 106 CFU/g, 1.4 x 103- 2.6 x 104 (CFU/g), 3.4 x 103 – 1.7 x 104 (CFU/g) and 1.2 x 103 – 1.1 x 104 (CFU/g) respectively. 16S rRNA gene sequencing revealed the presence of Enterobacter cloacae (LT 221670.1 -53%) and Bacillus safensis (AB711138.1 -99%), Pseudomonas mendocina (LN 881702.1 – 99%) and Aeromonas veroni (LC 487867.1 – 97%) from the root and leaf respectively. Aspergillus spp., Fusarium sp., Rhizopus sp., Trichoderma sp. Cladosporium sp. were among the fungi from the water weed parts. The proximate, nutrient and heavy metal constituents of water hyacinth vary among the leaf, stem and root. The proximate values for moisture (65.45%), protein (12.18%) and carbohydrate (5.30%) were highest in the leaf part compared to the stem and roots. Also, the highest values of ash (18.48%), fat (3.84%) and crude fibre (12.50%) were obtained in the plant root relative to leaf and stem. Apart from magnesium and phosphorous, mineral elements such as sodium, calcium and potassium were more abundant in the leaf. Among the heavy metal, Lead, Cadmium, Nickel, Arsenic and Cobalt had undetectable values for all parts. This study concludes that the presence of microbial biofertilizer and micro and macro nutrients on water hyacinth suggests its potential as raw material for biofertilizer and can be used to promote plant growth without negative consequences.

Low carbon accumulation in a macro‐tidal mangrove forest on the Amazon coast

AbstractThe important role mangrove forests play in sequestering organic carbon is well known, yet rates of organic carbon accumulation in macro‐tidal mangrove ecosystems are poorly resolved. Here we use 210Pb dating to present a 125‐yr record of carbon, nutrient and trace metal accumulation in sediments from an Amazon macro‐tidal mangrove forest. We find that the rate of organic carbon accumulation ranged from 23.7 to 74.7 g m−2 yr−1 (average 38 ± 13.5 g m−2 yr−1), significantly lower than global averages for mangrove forests. These low rates may be associated with sediment grain‐size and sediment–water interface processes that drive organic matter oxidation and reduce carbon stocks in these highly dynamic macro‐tidal forests. Total nitrogen accumulation ranged from 1.4 to 5.1 g m−2 yr−1 (average 2.7 ± 0.9 g m−2 yr−1) and phosphorus from 1.5 to 8.4 g m−2 yr−1(average 4.3 ± 1.9 g m−2 yr−1). Trace metal accumulation rates (As, Pb, Cr, Cu, Mn, Ni, Zn, Hg, Bo, V, Co, Mo, S, and Ba) were also lower than other tropical mangrove forests globally, but trace metal in more recent sediments for Mn, As, Cu, and Hg were elevated, likely reflecting human footprint in the region since early the 20th century. The ability to accurately quantify carbon accumulation rates in mangrove ecosystems is critical for climate change mitigation strategies and the implementation of carbon offset schemes globally.