Uptake and subcellular distribution of aluminum in a marine diatom

Abstract

Aluminum (Al) is widespread in the environment including the ocean. The effects of Al on marine organisms have attracted more and more attention in recent years. However, the mechanisms of uptake of Al by marine organisms and the subcellular distribution of Al once assimilated are unknown. Here we report the uptake and subcellular distribution of Al in a marine diatom Thalassiosira weissflogii. Short-term (< 120 min) uptake experiments showed that the Al uptake rate by the diatom was 0.033 ± 0.013 fmol/cell/min (internalization flux normalized to the exposure Al concentration of 2 µM = 0.034 ± 0.013 nmol•m-2 •min-1 •nM-1). Subcellular fractionation experiments showed that the internalized Al was partitioned to subcellular components in the following order: granules (69 ± 5%) > debris (17 ± 4%) > organelles (12 ± 2%) > heat-stable peptides (HSP) (~2%) > heat-denaturable proteins (HDP) (< 1%), indicating that the majority of intracellular Al was detoxified and stored in inorganic forms. The subcellular distribution of Al in the diatom is different from that of Al in freshwater green algae, in which most of the internalized Al is partitioned to organelles. We also evaluated an artificial seawater-based EDTA rinse solution to remove Al adsorbed on the diatom cell surface. Overall, our study provides new information to understand the mechanisms of uptake of Al by marine diatoms, and the mechanisms responsible for the biological effects (both toxic and beneficial) of Al on the growth of marine phytoplankton, especially diatoms.

Aluminum increases net carbon fixation by marine diatoms and decreases their decomposition: Evidence for the iron–aluminum hypothesis

“…The higher growth rates observed in the Al-enriched treatments during this phase, when phosphorus limitation occurred, are likely related to the proposed mechanism of Al-facilitated DOP utilization (Zhou et al 2016;Fig.1). The diatoms may also use polyphosphate bound to the internalized Al in diatom cells, as our recent study showed that most (69%) of the internalized Al in T. weissflogii cells was bound as inorganic granules, likely in polyphosphate bodies (Liu et al 2019).…”

“…receiving high dust deposition (40 nM) (Menzel Barraqueta et al 2019), the upper limit of dissolved Al in natural seawater (200 nM), and the concentration in estuarine waters (2000 nM), respectively (Zhou et al 2016). All the added Al will remain in the dissolved form in the culture media (Liu et al 2019) ) (Zhou et al 2018b). Aluminum will not form complexes significantly with EDTA or phosphate in alkaline seawater (Zhou et al 2016;Liu et al 2019).…”

“…All the added Al will remain in the dissolved form in the culture media (Liu et al 2019) ) (Zhou et al 2018b). Aluminum will not form complexes significantly with EDTA or phosphate in alkaline seawater (Zhou et al 2016;Liu et al 2019).…”

Modifying the thickness, pore size, and composition of diatom frustule in Craspedostauros sp. with Al3+ ions

“…grown in the presence of 2 μM Al 3+ as found by TGA appeared to be approximately 60% higher. The role of mineral particles inside the cell, most likely being metal-polyphosphate granules, has been suggested to be a tolerance mechanism for many organisms including diatoms to detoxify Al and other hard cations 28,46 . Therefore, the formation of the particles within the cell in the presence of Al 3+ which contained a high amount of P, O, Si and Al (Fig.…”

“…Most notably, Al incorporation into frustules of several diatom species has shown a significantly enhanced hydrolysis resistance compared to their Al-free types 26,27 . To date, the internalization of Al into the diatom cells has been investigated from a biological perspective in which Al is distributed within the cell at different subcellular compounds such as granules, debris, organelles, and proteins 28,29 . From the material science perspective exploring the effect of inorganic constituents like Al on the frustule pore size or thickness and the parameters controlling silicification are important too.…”