Reversible adsorption of iridium in lyophilized cells of the unicellular red alga .

Iridium (Ir) is one of the rarest elements in the Earth's crust and is valuable in industry due to its high corrosion resistance. In this study, we used lyophilized cells of a unicellular red alga, for the selective recovery of small amounts of Ir from hydrochloric acid (HCl) solutions. The Ir recovery efficiency of the lyophilized cells was higher than that of activated carbon and comparable to that of an ion-exchange resin in up to 0.

Cell population behavior of the unicellular red alga Galdieria sulphuraria during precious metal biosorption.

This study investigates the biosorption mechanism, including cell population behavior, of trace amounts of precious metals (gold, palladium, and platinum) in a unicellular red alga, Galdieria sulphuraria. Single-cell inductively coupled plasma mass spectrometry showed that the number of adsorbing cells and the concentration of adsorbed metal per cell varied depending on solution acidity and metal species. The X-ray absorption fine structure in 5 mM HCl solution indicated that the adsorbed Au formed inner-sphere complexes with S, whereas the adsorbed Pd and Pt formed an inner-sphere complexes with N and/or S.

Recovery of Au from dilute aqua regia solutions via adsorption on the lyophilized cells of a unicellular red alga Galdieria sulphuraria: A mechanism study.

The high electrical conductivity, chemical stability, and low toxicity of elemental Au make it a highly valuable resource. However, wastewater produced during the mining, utilization, and disposal of Au inevitably contains small amounts (10-40 mg L) of Au, thus posing environmental risks. It is too acidic to be treated with inexpensive and eco-friendly bioadsorbents previously studied for the remediation of less acidic effluents.

Structure of the triose-phosphate/phosphate translocator reveals the basis of substrate specificity.

The triose-phosphate/phosphate translocator (TPT) catalyses the strict 1:1 exchange of triose-phosphate, 3-phosphoglycerate and inorganic phosphate across the chloroplast envelope, and plays crucial roles in photosynthesis. Despite rigorous study for more than 40 years, the molecular mechanism of TPT is poorly understood because of the lack of structural information. Here we report crystal structures of TPT bound to two different substrates, 3-phosphoglycerate and inorganic phosphate, in occluded conformations.

Effective and selective recovery of gold and palladium ions from metal wastewater using a sulfothermophilic red alga, Galdieria sulphuraria.

The demand for precious metals has increased in recent years. However, low concentrations of precious metals dissolved in wastewater are yet to be recovered because of high operation costs and technical problems. The unicellular red alga, Galdieria sulphuraria, efficiently absorbs precious metals through biosorption.

Profiling of lipid and glycogen accumulations under different growth conditions in the sulfothermophilic red alga Galdieria sulphuraria.

The unicellular red alga Galdieria sulphuraria grows efficiently and produces a large amount of biomass in acidic conditions at high temperatures. It has great potential to produce biofuels and other beneficial compounds without becoming contaminated with other organisms. In G.

Recovery of rare earth elements from the sulfothermophilic red alga Galdieria sulphuraria using aqueous acid.

The demand for rare earth elements has increased dramatically in recent years because of their numerous industrial applications, and considerable research efforts have consequently been directed toward recycling these materials. The accumulation of metals in microorganisms is a low-cost and environmentally friendly method for the recovery of metals present in the environment at low levels. Numerous metals, including rare earth elements, can be readily dissolved in aqueous acid, but the efficiency of metal biosorption is usually decreased under the acidic conditions.

Air-drying of cells, the novel conditions for stimulated synthesis of triacylglycerol in a Green Alga, Chlorella kessleri.

Triacylglycerol is used for the production of commodities including food oils and biodiesel fuel. Microalgae can accumulate triacylglycerol under adverse environmental conditions such as nitrogen-starvation. This study explored the possibility of air-drying of green algal cells as a novel and simple protocol for enhancement of their triacylglycerol content.

External light conditions and internal cell cycle phases coordinate accumulation of chloroplast and mitochondrial transcripts in the red alga Cyanidioschyzon merolae.

The mitochondria and chloroplasts in plant cells are originated from bacterial endosymbioses, and they still replicate their own genome and divide in a similar manner as their ancestors did. It is thus likely that the organelle transcription is coordinated with its proliferation cycle. However, this possibility has not extensively been explored to date, because in most plant cells there are many mitochondria and chloroplasts that proliferate asynchronously.

Nucleus-independent control of the rubisco operon by the plastid-encoded transcription factor Ycf30 in the red alga Cyanidioschyzon merolae.

Chloroplasts originated from a cyanobacterium, which was engulfed by a primitive eukaryotic host cell. During evolution, chloroplasts have largely lost their autonomy due to the loss of many genes from their own genomes. Consequently, expression of genes encoded in the chloroplast genome is mainly controlled by the factors transferred from the cytosol to chloroplasts.

Nitrate assimilatory genes and their transcriptional regulation in a unicellular red alga Cyanidioschyzon merolae: genetic evidence for nitrite reduction by a sulfite reductase-like enzyme.

Cyanidioschyzon merolae is a unicellular red alga living in acid hot springs, which is able to grow on ammonium, as well as nitrate as sole nitrogen source. Based on the complete genome sequence, proteins for nitrate utilization, nitrate transporter (NRT) and nitrate reductase (NR), were predicted to be encoded by the neighboring nuclear genes CMG018C and CMG019C, respectively, but no typical nitrite reductase (NiR) gene was found by similarity searches. On the other hand, two candidate genes for sulfite reductase (SiR) were found, one of which (CMG021C) is located next to the above-noted nitrate-related genes.

Microarray profiling of plastid gene expression in a unicellular red alga, Cyanidioschyzon merolae.

Plastid genomes of red algae contain more genes than those of green plant lineages, and it is of special interest that four transcription factors derived from ancestral cyanobacteria are encoded therein. However, little is known about transcriptional regulation of the red algal plastid genome. In this study, we constructed a red algal plastid DNA microarray of Cyanidioschyzon merolae covering almost all protein coding genes, and found that plastid genes are differentially activated by illumination.

Improvement of culture conditions and evidence for nuclear transformation by homologous recombination in a red alga, Cyanidioschyzon merolae 10D.

Although the nuclear genome sequence of Cyanidioschyzon merolae 10D, a unicellular red alga, was recently determined, DNA transformation technology that is important as a model plant system has never been available thus far. In this study, improved culture conditions resulted in a faster growth rate of C. merolae in liquid medium (doubling time = 9.

Genome sequence of the ultrasmall unicellular red alga Cyanidioschyzon merolae 10D.

Small, compact genomes of ultrasmall unicellular algae provide information on the basic and essential genes that support the lives of photosynthetic eukaryotes, including higher plants. Here we report the 16,520,305-base-pair sequence of the 20 chromosomes of the unicellular red alga Cyanidioschyzon merolae 10D as the first complete algal genome. We identified 5,331 genes in total, of which at least 86.

Decrease in the efficiency of the electron donation to tyrosine Z of photosystem II in an SQDG-deficient mutant of Chlamydomonas.

Photosystem (PS) II activity of a sulfoquinovosyl diacylglycerol (SQDG)-deficient mutant (hf-2) of Chlamydomonas was partially decreased compared with that of wild-type. The susceptibility to 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) was also modified in the mutant. Photometric measurements in the isolated thylakoid membranes of hf-2 revealed that the lowered activity in the mutant was derived from a decrease in the efficiency of the electron donation from water to tyrosine Z, not from the efficiency of the electron transport from Q(A) to Q(B).

Involvement of sulfoquinovosyl diacylglycerol in the structural integrity and heat-tolerance of photosystem II.

To examine the role of sulfoquinovosyl diacylglycerol (SQDG) in thylakoid membranes, we compared the structural and functional properties of photosystem II (PSII) between a mutant of Chlamydomonas reinhardtii defective in SQDG ( hf-2) and the wild type. The PSII core complex of hf-2, as compared with that of the wild type, showed structural fragility when solubilized with a detergent, dodecyl beta- d-maltoside, suggesting that the physical properties of the PSII complex were altered by the loss of SQDG. On the other hand, exposure of the cells to 41 degrees C for 120 min in the dark decreased the PSII activity to 70% and 50% of the initial levels in the wild type and hf-2, respectively, which implies that the PSII activity, in the absence of SQDG, becomes less stable under heat-stress conditions.

Role of sulfoquinovosyl diacylglycerol for the maintenance of photosystem II in Chlamydomonas reinhardtii.

The physiological role of sulfoquinovosyl diacylglycerol (SQDG) in photosynthesis was investigated with a SQDG defective mutant (hf-2) of Chlamydomonas reinhardtii that did not have any detectable amount of SQDG. The mutant showed a lower rate of photosystem II (PSII) activity by approximately 40% and also a lower growth rate than those of the wild-type. Results of genetical analysis of hf-2 strongly suggest that the SQDG defect and the lowered PSII activity are due to a single gene mutation.