Anthracene phytotoxicity in the freshwater flagellate alga Euglena agilis Carter

The freshwater flagellate alga Euglena agilis Carter was exposed to the polycyclic aromatic hydrocarbon (PAH) anthracene for 96 h under optimal photosynthetically active radiation (PAR), and responses of growth, photosynthetic pigment production, and photosynthetic efficiency were assessed. Anthracene reduced the growth rate (mu) and levels of chlorophyll a (Chl a), chlorophyll b (Chl b), and total carotenoids. The growth rate was more sensitive than photosynthetic parameters, with a median effective concentration (EC50) of 4.28 mg L-1. Between 5 and 15 mg L-1, anthracene inhibited the maximum quantum yield (F-v/F-m) of photosystem II (PSII) and the maximum photosynthetic electron transport rate through PSII (rETR(max)) with EC50 values of 14.88 and 11.8 mg L-1, respectively. At all anthracene concentrations, intracellular reactive oxygen species (ROS) were elevated, indicating increased oxidative stress. Anthracene presumably reduced the PSII efficiency of photochemical energy regulation and altered the photochemistry through intracellular ROS formation. Acute exposure to PAHs may induce severe physiological changes in phytoplankton cells, which may influence vital ecological processes within the aquatic environments. Additionally, growth and Chl a content may serve as sensitive risk assessment parameters of anthracene toxicity in water management since EC50 values for both overlap with anthracene levels (8.3 mg L-1) permitted by the US Environmental Protection Agency (USEPA)

Rapid toxicity assessment of six antifouling booster biocides using a microplate-based chlorophyll fluorescence in Undaria pinnatifida gametophytes

Biocides of antifouling agents can cause problems in marine ecosystems by damaging to non-target algal species. Aquatic bioassays are important means of assessing the quality of water containing mixtures of contaminants and of providing a safety standard for water management in an ecological context. In this study, a rapid, sensitive and inexpensive test method was developed using free-living male and female gametophytes of the brown macroalga Undaria pinnatifida. A conventional fluorometer was employed to evaluate the acute (48 h) toxic effects of six antifouling biocides: 4,5-Dichloro-2-octyl-isothiazolone (DCOIT), diuron, irgarol, medetomidine, tolylfluanid, zinc pyrithione (ZnPT). The decreasing toxicity in male and female gametophytes as estimated by EC50 (effective concentration at which 50% inhibition occurs) values was: diuron (0.037 and 0.128 mg l(-1), respectively) > irgarol (0.096 and 0.172 mg l(-1), respectively) > tolylfluanid (0.238 and 1.028 mg l(-1), respectively) > DCOIT (1.015 and 0.890 mg l(-1), respectively) > medetomidine (12.032 and 12.763 mg l(-1), respectively). For ZnPT, 50% fluorescence inhibition of U. pinnatifida gametophytes occurred at concentrations above 0.4 mg l(-1). The Undaria method is rapid, simple, practical, and cost-effective for the detection of photosynthesis-inhibiting biocides, thus making a useful tool for testing the toxicity of antifouling agents in marine environments

Characteristics of Relative Navigation Algorithms Using Laser

This paper presents a satellite relative navigation strategy for formation flying, which chooses an appropriate navigation algorithm according to the operating environment. Not only global positioning system (GPS) measurements, but laser measurements can also be utilized to determine the relative positions of satellites. Laser data is used solely or together with GPS measurements. Numerical simulations were conducted to compare the relative navigation algorithm using only laser data and laser data combined with GPS data. If an accurate direction of laser pointing is estimated, the relative position of satellites can be determined using only laser measurements. If not, the combined algorithm has better performance, and is irrelevant to the precision of the relative angle data between two satellites in spherical coordinates. Within 10 km relative distance between satellites, relative navigation using double difference GPS data makes more precise relative position estimation results. If the simulation results are applied to the relative navigation strategy, the proper algorithm can be chosen, and the relative position of satellites can be estimated precisely in changing mission environments

Toxicity testing of cosmetic ingredients using gametophyte beads of the brown alga Undaria pinnatifida (Laminariales, Phaeophyta)

File embargoed until 03.01.2020 (publisher’s embargo period).A 6-h toxicity test of cosmetic ingredients (methylparaben, 2-phenoxyethanol, sodium dodecyl sulfate, triethanolamine) was developed, based on the photosynthetic maximum quantum yield (Fv/Fm) of immobilized gametophytes of the brown macroalga Undaria pinnatifida. From calculated EC50 values, the toxicity ranking of the tested ingredients is: SDS (0.0060%) > MP (0.0634%) > 2-PE (0.2418%) > TEA (3.7023%). Compared to the results from conventional endpoints with other ecotoxicity test organisms, measurements of Fv/Fm is a more sensitive indicator of the toxic effects of cosmetic ingredients. The present technique is simple, rapid, practical, accurate, and requires little space to carry out. This novel method will be a useful tool for assessing the toxicity of a wide range of cosmetic ingredients once the respective sensitivities are fully established

Rapid analytical approach for bioprofiling compounds with radical scavenging and antimicrobial activities from seaweeds

Brown seaweeds are traditionally used as food in Asian countries, and they are a valuable source of bioactive compounds. Herein, a novel high-throughput methodological approach was developed for the tracing of compounds with radical scavenging and antimicrobial activities in Saccharina japonica and Undaria pinnatifida methanol extracts. The seaweed metabolites were separated by a novel high-performance thin-layer chromatography method, the bioactive bands were identified by bioautography assays. The bioactive compounds were characterized with ultra-high-performance liquid chromatography coupled with linear trap quadrupole tandem mass spectrometry. Stearidonic, eicosapentaenoic, and arachidonic acids were identified as major components having radical scavenging and antimicrobial activities. The suggested method provides a fast identification and quantification of bioactive compounds in multicomponent biological samples.This is the peer reviewed version of the following article: (1) Ristivojević, P.; Jovanović, V.; Milojković-Opsenica, D.; Park, J.; Rollinger, J. M.; Ćirković-Veličković, T. Rapid Analytical Approach for Bioprofiling Compounds with Radical Scavenging and Antimicrobial Activities from Seaweeds. Food Chemistry 2021, 334, 127562. [https://doi.org/10.1016/j.foodchem.2020.127562].Supplementary material: [https://cherry.chem.bg.ac.rs/handle/123456789/4865

Phaeoviral infections are present in macrocystis, ecklonia and undaria (laminariales) and are influenced by wave exposure in ectocarpales

Two sister orders of the brown macroalgae (class Phaeophyceae), the morphologically complex Laminariales (commonly referred to as kelp) and the morphologically simple Ectocarpales are natural hosts for the dsDNA phaeoviruses (family ) that persist as proviruses in the genomes of their hosts. We have previously shown that the major capsid protein (MCP) and DNA polymerase concatenated gene phylogeny splits phaeoviruses into two subgroups, A and B (both infecting Ectocarpales), while MCP-based phylogeny suggests that the kelp phaeoviruses form a distinct third subgroup C. Here we used MCP to better understand the host range of phaeoviruses by screening a further 96 and 909 samples representing 11 and 3 species of kelp and Ectocarpales, respectively. Sporophyte kelp samples were collected from their various natural coastal habitats spanning five continents: Africa, Asia, Australia, Europe, and South America. Our phylogenetic analyses showed that while most of the kelp phaeoviruses, including one from , belonged to the previously designated subgroup C, new lineages of in 3 kelp species, , , , grouped instead with subgroup A. In addition, we observed a prevalence of 26% and 63% in kelp and Ectocarpales, respectively. Although not common, multiple phaeoviral infections per individual were observed, with the Ectocarpales having both intra- and inter-subgroup phaeoviral infections. Only intra-subgroup phaeoviral infections were observed in kelp. Furthermore, prevalence of phaeoviral infections within the Ectocarpales is also linked to their exposure to waves. We conclude that phaeoviral infection is a widely occurring phenomenon in both lineages, and that phaeoviruses have diversified with their hosts at least since the divergence of the Laminariales and Ectocarpales

Genome editing in macroalgae: advances and challenges

This minireview examines the current state and challenges of genome editing in macroalgae. Despite the ecological and economic significance of this group of organisms, genome editing has seen limited applications. While CRISPR functionality has been established in two brown (Ectocarpus species 7 and Saccharina japonica) and one green seaweed (Ulva prolifera), these studies are limited to proof-of-concept demonstrations. All studies also (co)-targeted ADENINE PHOSPHORIBOSYL TRANSFERASE to enrich for mutants, due to the relatively low editing efficiencies. To advance the field, there should be a focus on advancing auxiliary technologies, particularly stable transformation, so that novel editing reagents can be screened for their efficiency. More work is also needed on understanding DNA repair in these organisms, as this is tightly linked with the editing outcomes. Developing efficient genome editing tools for macroalgae will unlock the ability to characterize their genes, which is largely uncharted terrain. Moreover, given their economic importance, genome editing will also impact breeding campaigns to develop strains that have better yields, produce more commercially valuable compounds, and show improved resilience to the impacts of global change

Reappraisal of the toxicity test method using the green alga Ulva pertusa Kjellman (Chlorophyta),

This study was aimed to develop an objective way of quantifying the reproductive status of the green macroalga, Ulva pertusa using a vital stain and programmed automated analysis (by Image J program). The EC50 values (with 95% CI), the concentrations of toxicants inducing a reduction of 50% in sporulation after 96 h exposure, from the newly developed method were similar to those obtained by the conventional method: 0.651 (0.598-0.705) mg l(-1) for Cd, 0.144 (0.110-0.162) mg l(-1) for Cu, 0.180 (0.165-0.195) mg l(-1) for atrazine, 0.076 (0.049-0.094) mg l(-1) for diuron and 30.6 (26.5-34.4) ml l(-1) for DMSO, respectively. When the EC50 values from this study were compared to that those from literatures, the sensitivity for some toxicants was similar or higher than that of U. fasciata (1.930 mg l(-1) for germination for Cd), U. armoricana (0.250 mg l(-1) for Fv/Fm for Cu), U. reticulata (0.126-1.585 mg l(-1) for growth for Cu), and U. intestinalis (0.650 mg l(-1) for Fv/Fm for atrazine). The subjective views of the experimental performers can be eliminated using the newly developed method. The Ulva method gave consistent responses to Cu and Cd of internationally allowable ranges for effluents, implying that the method is a useful tool for monitoring industrial wastewaters containing these metals

Photosynthetic and biochemical traits change in the green-tide-forming macroalga Ulva pertusa during sporulation

The physiological and biochemical changes in the green macroalga Ulva pertusa during the progression of sporulation have been characterized. The transition from the vegetative to the sporulation stage was accompanied by an increase in chlorophyll a (Chl a), chlorophyll b (Chl b), and carotenoid content, as well as an increase in DPPH scavenging and responsiveness to diphenylamine. However, oxygen evolution and maximum electron transport rate decreased. The discrepancy between photosynthetic performance and pigment content might relate to the self-shading of spores within a sporangium. Spore-forming U. pertusa thalli were low-light-adapted, due to an increase in the number of photosynthetic units. Decreased electron transport during sporulation might trigger sporulation, as for some cyanobacteria and other Ulva spp., via oxidization of the plastoquinone pool and cyclic phosphorylation, thus producing ATP to generate carbon and nitrogen skeletons required for spores. It is thus concluded that carotenoids function both in spore initiation and/or maturation and in their photoprotection

To speak or not to speak: silence in classrooms

The enrollment number of Chinese students in North American universities is increasing every year. Even though graduate courses are discussion-based, many university instructors have experienced the "silent Chinese" phenomenon in classrooms. This study looks through investigating the reasons for Chinese international students' silence in classrooms. Basil Bernstein's language code theory was used as a theoretical framework to explain the difficulties international students experience in speaking up in class. From students' narratives, the aim of this study is to understand genuine reasons for their silence so that the school community can better assist students with diverse backgrounds. Using in-depth interviews, this study explores six international Chinese students' experiences studying abroad in a graduate program at a large university in Canada. Three themes were identified from the interviews: First, language proficiency; second, previous schooling experience in China; and third, Chinese typical culture of face. This thesis concludes with implications on how this study to understand Chinese international students' difficulties can bring in great learning opportunities to the classroom and also create a multicultural classroom that values diverse ideas.Keywords: Chinese international students, silence in classrooms, face culture, language codesLe nombre d'inscriptions d'étudiants chinois dans les universités nord-américaines augmente chaque année. Bien que les cours de troisième cycle soient basés sur des discussions, de nombreux professeurs d'université ont expérimenté le phénomène du «chinois silencieux» dans les salles de classe. Cette étude examine les raisons du silence des étudiants étrangers chinois dans les salles de classe. La théorie des codes linguistiques de Basil Bernstein a été utilisée comme un cadre théorique pour expliquer les difficultés rencontrées par les étudiants internationaux pour s'exprimer en classe. À partir des récits des élèves, l'objectif de cette étude est de comprendre les véritables raisons de leur silence afin que la communauté scolaire puisse mieux assister les élèves d'origines diverses. À partir d'entrevues approfondies, cette étude explore les expériences de six étudiants chinois internationaux qui étudient à l'étranger dans le cadre d'un programme de cycles supérieurs dans une grande université canadienne. Les entretiens ont permis de dégager trois thèmes: premièrement, la maîtrise de la langue; deuxièmement, une expérience scolaire antérieure en Chine; et troisièmement, la culture de visage typique chinoise. Cette thèse se termine par des implications sur la manière dont cette étude visant à comprendre les difficultés des étudiants étrangers chinois peut apporter de grandes opportunités d'apprentissage en classe et également créer une classe multiculturelle qui valorise des idées diverses.Mots-clés: étudiants internationaux chinois, silence en classe, culture chinoise du face, codes de langu