Adaptive responses of marine diatoms to zinc scarcity and ecological implications

Modification of Living Diatom, Thalassiosira weissflogii, with a Calcium Precursor through a Calcium Uptake Mechanism: A Next Generation Biomaterial for Advanced Delivery Systems

The diatom's frustule, characterized by its rugged and porous exterior, exhibits a remarkable biomimetic morphology attributable to its highly ordered pores, extensive surface area, and unique architecture. Despite these advantages, the toxicity and nonbiodegradable nature of silica-based organisms pose a significant challenge when attempting to utilize these organisms as nanotopographically functionalized microparticles in the realm of biomedicine. In this study, we addressed this limitation by modulating the chemical composition of diatom microparticles by modulating the active silica metabolic uptake mechanism while maintaining their intricate three-dimensional architecture through calcium incorporation into living diatoms. Here, the diatom Thalassiosira weissflogii was chemically modified to replace its silica composition with a biodegradable calcium template, while simultaneously preserving the unique three-dimensional (3D) frustule structure with hierarchical patterns of pores and nanoscale architectural features, which was evident by the deposition of calcium as calcium carbonate. Calcium hydroxide is incorporated into the exoskeleton through the active mechanism of calcium uptake via a carbon-concentrating mechanism, without altering the microstructure. Our findings suggest that calcium-modified diatoms hold potential as a nature-inspired delivery system for immunotherapy through antibody-specific binding.

Biogenic-to-lithogenic handoff of particulate Zn affects the Zn cycle in the Southern Ocean

Zinc (Zn) is vital to marine organisms. Its active uptake by phytoplankton results in a substantial depletion of dissolved Zn, and Zn bound to particulate organic matter replenishes dissolved Zn in the ocean through remineralization. However, we found that particulate Zn changes from Zn bound to phosphoryls in cells to recalcitrant inorganic pools that include biogenic silica, clays, and iron, manganese, and aluminum oxides in the Southern Ocean water column. The abundances of inorganic pools increase with depth and are the only phases preserved in sediments. Changes in the particulate-Zn speciation influence Zn bioavailability and explain the decoupling of Zn and phosphorus and the correlation of Zn and silicon in the water column. These findings reveal a new dimension to the ocean Zn cycle, implicating an underappreciated role of inorganic Zn particles and their impact on biological productivity.

A brief history of metal recruitment in protozoan predation

Metals and metalloids are used as weapons for predatory feeding by unicellular eukaryotes on prokaryotes. This review emphasizes the role of metal(loid) bioavailability over the course of Earth's history, coupled with eukaryogenesis and the evolution of the mitochondrion to trace the emergence and use of the metal(loid) prey-killing phagosome as a feeding strategy. Members of the genera Acanthamoeba and Dictyostelium use metals such as zinc (Zn) and copper (Cu), and possibly metalloids, to kill their bacterial prey after phagocytosis. We provide a potential timeline on when these capacities first evolved and how they correlate with perceived changes in metal(loid) bioavailability through Earth's history. The origin of phagotrophic eukaryotes must have postdated the Great Oxidation Event (GOE) in agreement with redox-dependent modification of metal(loid) bioavailability for phagotrophic poisoning. However, this predatory mechanism is predicted to have evolved much later - closer to the origin of the multicellular metazoans and the evolutionary development of the immune systems.

Trace and rare earth elements in phytoplankton from the Tyrrhenian Sea (Italy)

Plankton plays a very crucial role in bioaccumulation and transfer of metals in the marine food web and represents a suitable bioindicator of the occurrence of trace and rare earth elements in the ecosystem. Trace elements and REEs were analyzed by ICP-MS in phytoplankton samples from the northwestern Mediterranean Sea. Metal concentrations in phytoplankton were found strongly influenced by seasons and depth of collection (- 30 m, - 50 m). Principal component analysis (PCA) has shown that Al, As, Cr, Cu, Ga, and Sn concentrations were related to summer and autumn in samples collected at 30 m depth, while Fe, Mn, Ni, V, and Zn levels related strongly with summer and spring at 50 m depth. Fe, Al, and Zn were the most represented elements in all samples (mean values respectively in the ranges 4.2-8.2, 9.6-13, and 1.0-4.4 mg kg-1) according to their widespread presence in the environment and in the earth crust. Principal component analysis (PCA) performed on REEs showed that mostly all lanthanides' concentrations strongly correlate with summer and autumn seasons (- 30 m depth); the highest ∑REE concentration (75 µg kg-1) was found in winter. Phytoplankton REE normalized profile was comparable to those of other marine biota collected in the same area according to the suitability of lanthanides as geological tracers.

Implications of ocean acidification on micronutrient elements-iron, copper and zinc, and their primary biological impacts: A review

This review has been undertaken to understand the effectiveness of ocean acidification on oceanic micronutrient metal cycles (iron, copper and zinc) and its potential impacts on marine biota. Ocean acidification will slow down the oxidation of Fe(II) thereby retarding Fe(III) formation and subsequent hydrolysis/precipitation leading to an increase in iron bioavailability. Further, the increased primary production sustains enzymatic bacteria assisted Fe(III) reduction and subsequently the binding of weaker ligands favours the dissociation of free Fe(II) ions, thus increasing the bioavailability. The increasing pCO2 condition increases the bioavailability of copper ions by decreasing the availability of free CO32- ligand concentration. The strong complexation by dissolved organic matter may decrease the bioavailable iron and zinc ion concentration. Since ocean acidification affects the bioavailability of essential metals, studies on the uptake rates of these elements by phytoplankton should be carried out to reveal the future scenario and its effect on natural environment.

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.

The elements of life: A biocentric tour of the periodic table

Living systems are built from a small subset of the atomic elements, including the bulk macronutrients (C,H,N,O,P,S) and ions (Mg,K,Na,Ca) together with a small but variable set of trace elements (micronutrients). Here, we provide a global survey of how chemical elements contribute to life. We define five classes of elements: those that are (i) essential for all life, (ii) essential for many organisms in all three domains of life, (iii) essential or beneficial for many organisms in at least one domain, (iv) beneficial to at least some species, and (v) of no known beneficial use. The ability of cells to sustain life when individual elements are absent or limiting relies on complex physiological and evolutionary mechanisms (elemental economy). This survey of elemental use across the tree of life is encapsulated in a web-based, interactive periodic table that summarizes the roles chemical elements in biology and highlights corresponding mechanisms of elemental economy.

Thalassiosira weissflogii grown in various Zn levels shows different ecophysiological responses to seawater acidification

The presence of zinc (Zn), a vital element for algal physiological functions, coupled with the silicification of diatoms implies that it plays an integral role in the carbon and silicon cycles of the sea. In this study, we examined the effects of different pCO₂ and Zn levels on growth rate, elemental compositions and silicification by Thalassiosira weissflogii. The results showed that under normal pCO₂ (400 μatm), cultures of T. weissflogii were depressed for growth rate and silica incorporation rate, but encouraged for cellular silicon content, Si/C, Si/N, and sinking rate when Zn deficient (0.3 pmol L^-1). However, cellular silicon and sinking rate of Zn-deficient and Zn-replete (25 pmol L^-1) T. weissflogii were decreased and increased at higher pCO₂ (800 μatm), respectively. Thus, acidification may affect diatoms significantly differently depending on the Zn levels of the ocean and then alter the biochemical cycling of carbon and silica.

Effects of nitrogen and phosphorus availability on cadmium tolerance in the marine diatom Phaeodactylum tricornutum

Although the influence of major nutrients on metal toxicity in marine phytoplankton has been widely explored, the mechanisms involving the cell surface are poorly understood. Here, the model marine diatom Phaeodactylum tricornutum was cultured under different nitrogen (N), and phosphorus (P) availabilities from the f/2 to the f/20 level in the laboratory; the diatom's accumulation of cadmium (Cd) and the effects of the physical and chemical properties of the cell wall were investigated at the single-cell level. Under higher N and/or P supply at the f/2 level, both the adsorption and uptake of Cd were enhanced in the P. tricornutum cells. The N and P increased the ion-binding sites on the cell surface, causing more negative surface potential and less depolarization of the diatoms' cell walls. Up-regulated transporter genes were detected in those cells with enriched nutrient supply, which could be attributed to the higher Cd uptake. These results strongly indicate that N and P are critical nutrients for frustule-mediated metal accumulation and tolerance in marine diatoms. Our study provides new clues on the nutrient-dependent cell-surface physical and chemical mechanisms involved in metal toxicity in marine diatoms.