The central role of selenium in the biochemistry and ecology of the harmful pelagophyte,Aureococcus anophagefferens

The trace element selenium (Se) is required for the biosynthesis of selenocysteine (Sec), the 21st amino acid in the genetic code, but its role in the ecology of harmful algal blooms (HABs) is unknown. Here, we examined the role of Se in the biology and ecology of the harmful pelagophyte, Aureococcus anophagefferens, through cell culture, genomic analyses, and ecosystem studies. This organism has the largest and the most diverse selenoproteome identified to date that consists of at least 59 selenoproteins, including known eukaryotic selenoproteins, selenoproteins previously only detected in bacteria, and novel selenoproteins. The A. anophagefferens selenoproteome was dominated by the thioredoxin fold proteins and oxidoreductase functions were assigned to the majority of detected selenoproteins. Insertion of Sec in these proteins was supported by a unique Sec insertion sequence. Se was required for the growth of A. anophagefferens as cultures grew maximally at nanomolar Se concentrations. In a coastal ecosystem, dissolved Se concentrations were elevated before and after A. anophagefferens blooms, but were reduced by >95% during the peak of blooms to 0.05 nℳ. Consistent with this pattern, enrichment of seawater with selenite before and after a bloom did not affect the growth of A. anophagefferens, but enrichment during the peak of the bloom significantly increased population growth rates. These findings demonstrate that Se inventories, which can be anthropogenically enriched, can support proliferation of HABs, such as A. anophagefferens through its synthesis of a large arsenal of Se-dependent oxidoreductases that fine-tune cellular redox homeostasis.     

Biodiversity and dynamics of cyanobacterial communities during blooms in temperate lake (Harsha Lake,Ohio, USA)

Cyanobacterial blooms are intensifying global ecological hazards. The fine structure and dynamics of bloom community are critical to understanding bloom development but little understood. Here, the questions whether dominant bloomers have high diversity and whether dominant OTUs (operational taxonomical units) compete with one another were addressed. 16S rRNA gene amplicons from an annual bloom at five locations in Harsha Lake (Ohio, USA) showed cyanobacteria were the dominant phylum, and co-existing major bacterial phyla included Proteobacteria, Bacteroidetes, Actinoacteria, and Verrucomicrobia. On the genus level, the initial dominance by Dolichospermum in June yielded to Planktothrix in July, which were replaced by Microcystis and Cylindrospermopsis in August throughout the bloom. Based on the number of verified unique OTUs (a within-genus biodiversity metric), dominant genera tended to have high within-genus diversity. For example, Dolichospermum had 57 unique OTUs, Planktothrix had 36, Microcystis had 12, and Cylindrospermopsis had 4 unique OTUs. Interestingly, these different OTUs showed different dynamics and association with other OTUs. First, no between-OTU competitions were observed during the bloom cycle, and dominant OTUs were abundant throughout the bloom. Such biodiversity of OTUs and their dynamics were verified in Microcystis aeruginosa with two microcystin synthetase genes (mcyA and mcyG): the relative abundance of both genes varied during the bloom based on quantitative PCR. Two Dolichospermum circinale OTUs and one P. rubescens OTU were most abundant and persistently present throughout the entire bloom. Second, these OTUs differed in the OTUs they were associated with. Third, these OTUs tended to have different levels of association with the environmental factors, even they belonged to the same genera. These findings suggest the structure and dynamics of a cyanobacterial bloom community is complex, with only few OTUs dominating the bloom. Thus, high-resolution molecular characterization will be necessary to understand bloom development.     

CYANOBACTERIAL BUOYANCY REGULATION: THE PARADOXICAL ROLES OF CARBON1

In stratified lakes, dominance of the phytoplankton by cyanobacteria is largely the result of their buoyancy and depth regulation. Bloom-forming cyanobacteria regulate the gas vesicle and storage polymer contents of their cells in response to interactive environmental factors, especially light and nutrients. While research on the roles of nitrogen and phosphorus in cyanobacterial buoyancy regulation has reached a consensus, evaluations of the roles of carbon have remained open to dispute. We investigated the various effects of changes in carbon availability on cyanobacterial buoyancy with continuous cultures of Microcystis aeruginosa Kuetz. emend. Elenkin (1924), a notorious bloom-former. Although CO₂ limitation of photosynthesis can promote buoyancy in the short term by preventing the collapse of turgor-sensitive gas vesicles and/or by limiting polysaccharide accumulation, we found that sustained carbon limitation restricts buoyancy regulation by limiting gas vesicle as well as polysaccharide synthesis. These results provide an explanation for the positive effects of bicarbonate enrichment on cyanobacterial nitrogen uptake and bloom formation in lake experiments and may help to explain the pattern of cyanobacterial dominance in phosphorus-enriched, low-carbon lakes.     

Study on the Interaction Mechanism of 2‐Aminoanthraquinone with Calf Thymus DNA

By utilizing multispectrosopic techniques, the toxic interaction of 2‐aminoanthraquinone (2‐AAQ) with calf thymus deoxyribonucleic acid (ctDNA) was investigated in vitro under simulated physiological conditions. The experimental results proved that 2‐AAQ has a toxic interaction with ctDNA. The binding capacity of DNA with 2‐AAQ is diminishing as the pH value of system increasing in the optimization of experimental condition. Moreover we selected pH 7.4, which is nearly physiological condition to enhance the practical significance. According to the Stern–Volmer equation, the quenching was the static quenching process. And the quenching constant can be derived from the fluorescence quenching spectrogram. Ultraviolet absorption spectra and the change in the fluorescence intensity at different ionic strengths further indicated that there was electrostatic binding between 2‐AAQ and ctDNA. The circular dichroism experiment showed that the DNA conformation varied from B to A conformation. The basic group enhanced after 2‐AAQ embedding. The double helix is more compact, and the DNA conformation changes. © 2013 Wiley Periodicals, Inc. J BiochemMol Toxicol 27:272‐278, 2013; View this article online at wileyonlinelibrary.com . DOI 10.1002/jbt.21487     

Turbulence, watermass stratification and harmful algal blooms: an alternative view and frontal zones as “pelagic seed banks”

Watermass stratification has been considered the essential physical condition that dinoflagellates require to bloom because of their relative inability, unlike diatoms, to tolerate the elevated shear-stress associated with water-column mixing, turbulence and high velocity, coastal currents. The swimming speeds of 71 flagellate taxa, with a focus on dinoflagellates, are compared to the turbulence fields and vertical velocities that develop during representative wind conditions, upwelling and at frontal zones. The results suggest that the classical stratification–dinoflagellate bloom paradigm needs revision. Tolerance of turbulence, growth within well-mixed watermasses and survival and dispersal while entrained within current systems are well developed capacities among dinoflagellates. Their secretion of mucous, often copious during blooms, is suggested to be an environmental engineering strategy to dampen turbulence. Biophysical tolerance of turbulence by dinoflagellates is often accompanied by high swimming speeds. Motility speeds of many species exceed in situ vertical current velocities; this also allows diel migrational patterns and other motility-based behavior to persist. Species belonging to “mixing-drift” life-form assemblages can increase their swimming speeds through chain formation, which helps to compensate for the increased turbulence and vertical water-column velocities of their habitats. The ability of dinoflagellate species to tolerate the vertical velocities of offshore, frontal zones, where abundant populations often develop, suggests that fronts may serve as “pelagic seed banks”, occurring as pelagic analogues of nearshore seed beds, from which seed stock is dispersed. The different ecologies associated with the hypothesized, “pelagic seed banks” of vegetative cells and the “seed beds” of resting stage cells deposited onto sediments are discussed. There is a contradiction in the stratification–HAB paradigm: the quiescent conditions of a stratified watermass, with its characteristic nutrient-poor conditions are expected to promote stasis of the population, rather than growth and blooms. The analyses suggest that dinoflagellate blooms do not preponderate in stratified watermasses because the bloom species are biophysically intolerant of the higher velocities and turbulence of more mixed watermasses. The watermass stratification that often accompanies flagellate blooms is probably a secondary, parallel event and less essential than some other factor(s) in triggering the observed bloom.     

Eutrophication in Australian Rivers, Reservoirs and Estuaries – A Southern Hemisphere Perspective on the Science and its Implications

Australian science has made rapid advances in the last decade in understanding eutrophication processes in inland waters and estuaries. The freshwater research on which these advances are based was triggered by well-publicised blooms of cyanobacteria during the 1980s and early 1990s, particularly a 1000 km long bloom on the Darling River. In estuaries the study which greatly enhanced our understanding but simultaneously served to stimulate further research into estuarine eutrophication, the Port Phillip Bay Study, was initially designed to address perceived problems of toxicants in the Bay but provided profound insights into drivers for, and ecosystem responses to, eutrophication. Subsequent estuarine research has largely been stimulated by management questions arising from Australia’s increasing coastal development for residential purposes. The research has shown that some of the beliefs extant at the time of the blooms were incorrect. For example, it is now clear that stratification and light penetration, not nutrient availability, are the triggers for blooms in the impounded rivers of southeastern Australia, although nutrient exhaustion limits the biomass of blooms. Again, nitrogen seems to play as important a role as phosphorus does in controlling the biomass of these freshwater blooms. The research has also shown that aspects of eutrophication, such as nutrient transport, are dominated by different processes in different parts of Australia. Many of the biophysical processes involved in eutrophication have now been quantified sufficiently for models to be developed of such processes as sediment-nutrient release, stratification, turbidity and algal growth in both freshwater and estuarine systems. In some cases the models are reliable enough for the knowledge gained in particular waterbodies to be applied elsewhere. Thus, there is now a firm scientific foundation for managers to rely upon when managing algal blooms. Whilst these findings have already been presented to managers and communities throughout Australia, there is still a considerable way to go before they are absorbed into their modus operandi.     

Rapid detection of natural cells of Alexandrium tamarense and A. catenella (Dinophyceae) by fluorescence in situ hybridization

The marine toxic dinoflagellates Alexandrium tamarense (Lebor) Balech and A. catenella (Whedon and Kofoid) Taylor that cause paralytic shellfish poisoning (PSP) are identified on the basis of morphological features in routine monitoring. Rapid and simple identification is, however, often difficult because of the morphological similarity. Fluorescent in situ hybridization (FISH) using ribosomal RNA (rRNA)-targeted probes has been studied as a method of easily identifying and enumerating species responsible for harmful algal blooms (HABs). Its application to monitoring natural populations of HAB species, however, is limited. Here, we applied the FISH method to identify and enumerate cells of A. tamarense and A. catenella in natural plankton assemblages collected from Japanese coastal waters. A. tamarense-specific (Atm1) and A. catenella-specific (Act1) probes were established based on the D2 region of the large-subunit ribosomal RNA gene (28S rDNA). With these two probes, natural cells of A. tamarense or A. catenella in field samples could easily be identified when the following three conditions were met. First, cells should be concentrated by filtration, not centrifugation, in order to avoid the loss of cells. Second, autofluorescence should be minimized; acetone was an effective decolorization reagent. Third, samples should be stored at −20 or −80 °C for long-term preservation. The results indicate that FISH is a useful tool for the rapid identification of toxic Alexandrium spp. and can facilitate the analysis of numerous natural samples.     

Climate variability and Dinophysis acuta blooms in an upwelling system

Dinophysis acuta is a frequent seasonal lipophilic toxin producer in European Atlantic coastal waters associated with thermal stratification. In the Galician Rías, populations of D. acuta with their epicentre located off Aveiro (northern Portugal), typically co-occur with and follow those of Dinophysis acuminata during the upwelling transition (early autumn) as a result of longshore transport. During hotter than average summers, D. acuta blooms also occur in August in the Rías, when they replace D. acuminata. Here we examined a 30-year (1985–2014) time series of D. acuta from samples collected by the same method in the Galician Rías. Our main objective was to identify patterns of distribution and their relation with climate variability, and to explain the exceptional summer blooms of D. acuta in 1989–1990. A dome-shaped relationship was found between summer upwelling intensity and D. acuta blooms; cell maxima were associated with conditions where the balance between upwelling intensity and heating, leading to deepened thermoclines, combined with tidal phase (3 days after neap tides) created windows of opportunity for this species. The application of a generalized additive model based on biological (D. acuta inoculum) and environmental predictors (Cumulative June–August upwelling CUI_JJA, average June–August SST_JJA and tidal range) explained more than 70% of the deviance for the exceptional summer blooms of D. acuta, through a combination of moderate (35,000–50,000 m³ s⁻¹ km⁻¹) summer upwelling (CUI_JJA), thermal stratification (SST_JJA > 17 °C) and moderate tidal range (∼2.5 m), provided D. acuta cells (inoculum) were present in July. There was no evidence of increasing trends in D. acuta bloom frequency/intensity nor a clear relationship with NAO or other long-term climatic cycles. Instead, the exceptional summer blooms of 1989–1990 appeared linked to extreme hydroclimatic anomalies (high positive anomalies in SST and NAO index), which affected most of the European Atlantic coast.     

The concentrations of essential/toxic elements in serum of COVID-19 patients are not directly related to the severity of the disease

BackgroundIn recent months, the current COVID-19 pandemic has generated thousands of studies directly or indirectly related with this disease and/or the coronavirus SARS-CoV-2 causing the infection. On August 22, 2022, the database PUBMED included 287,639 publications containing the term COVID-19. However, in spite of the importance of trace elements in human health, including the immune system, data on the levels of metals/metalloids in COVID-19 patients is very limited.MethodsThe concentrations of As, Cd, Cr, Cu, Hg, Fe, Mg, Mn, Pb, Se, V and Zn were determined by inductively coupled plasma-mass spectrometry (ICP-MS) in 126 serum samples of individuals infected with SARS-CoV-2, as well as in 88 samples of non-infected individuals. Participants were divided into four groups: i) individuals COVID-19 positive (COVID-19 +) with an asymptomatic infection course; ii) individuals suffering mild COVID-19; iii) individuals suffering severe COVID-19, and iv) individuals COVID-19 negative (COVID-19-) (control group). The occurrence of the analyzed metals/metalloids was evaluated along with the biochemical profile, including blood cell counts, lipids, proteins and crucial enzymes.ResultsSerum levels of Mg, V, Cr, Cu, Cd, and Pb were higher in COVID-19 positive patients than those in the control group. Although no significant differences were observed between the different groups of patients, the concentrations of Cd, Pb, V and Zn showed a tendency to be higher in individuals with severe COVID-19 than in those showing mild symptoms or being asymptomatic. Arsenic and Hg were rarely detected, regardless if the subjects were infected by SARS-CoV-2, or not. The current results did not show significant differences in the levels of the rest of analyzed elements according to the severity of the disease (asymptomatic, mild and severe).ConclusionsIn spite of the results here obtained, we highlight the need to reduce the exposure to Cd, Pb and V to minimize the potential adverse health outcomes after COVID-19 infection. On the other hand, although a protective role of essential elements was not found, Mg and Cu concentrations were higher in severe COVID-19 patients than in non-infected individuals.