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The traditional classroom adopts the collective teaching method, uses the same unified content, unified progress, and sets the same requirements for students; but different students have different understanding and mastery of the knowledge, which greatly reduces the effectiveness of the classroom teaching result. Stratified teaching method makes good use of individual differences and knowledge foundations of students, and formulates the matching teaching plan and teaching resources, so as to promote students to obtain improvements to different extents, and then improve their overall quality and ability comprehensively. This paper researches on the meaning and practical experience of the stratified teaching method, thus enriches the corresponding theoretical contents.

The succession of dominant phytoplankton species plays an important role in harmful algal blooms. However, the molecular mechanism of algal succession remains largely unclear, including the most commonly occurring diatom/dinoflagellate succession. Here we investigated the responses of the diatom Phaeodactylum tricornutum during mixed culture with the potentially toxic dinoflagellate Alexandrium tamarense . The growth of P. tricornutum was significantly inhibited within 24 h in mixed culture. Organelles such as the chloroplasts and mitochondria of P. tricornutum were severely damaged. Transcriptional responses in P. tricornutum were revealed by RNA-seq. Genes involved in glycolysis, TCA cycle, β-oxidation, carbon fixation and oxidation phosphorylation were downregulated, indicating the inhibition of energy metabolism. Several genes associated with check points and cell cycle were also downregulated, suggesting the suppression of DNA replication and cell division. Taking into account the upregulation of genes involved in endocytosis and transporter ABCB1, P. tricornutum could perceive certain allelochemicals released from A. tamarense , which played a role in their interaction. Additionally, a family of leucine-rich repeat receptor-like kinases was upregulated, suggesting that flagellin-sensitive mediated cell-cell interactions are responsible for toxic effect other than allelopathy. Here we showed a molecular overview of interactions between diatom and dinoflagellate, thereby provide molecular insight into the unraveled mechanisms on the effects of toxic species on non-toxic species.

Using laser scanning confocal microscope (LACM) and flow cytometry (FCM), we found that MK571, a specific inhibitor of multidrug resistance-associated protein (MRP), could increase the accumulation of calcein-AM in Prorocentrum lima, a DSP toxin-producing dinoflagellate. This led to the assumption that the cells of P. lima possess MRP transporters in the plasma membrane. The contents of okadaic acid (OA), a main component of DSP toxins, and MRP activities in P. lima were determined at 4, 20, 28, and 42 days after culture and at 38 day under N- and P-limited conditions. We found that both the OA level and MRP activity in P. lima increased over time; OA concentration and MRP activity conformably increased under N- and P-limited conditions compared with control counterparts. These changes in OA concentration and associated increased MRP activity suggest that MRP might be involved in OA transport in P. lima. However, MK571 and CsA, a broad-spectrum inhibitor of multidrug resistance (MDR)-associated ABC proteins, had no observable effects on OA content in P. lima. It seems that except for MDR-associated ABC proteins, other transporters like PDR might be involved in the transport of OA in P. lima.

To find new chemical modifiers and new modified clays with excellent algae removal efficiency, the removal effects of betaine and five sulfobetaines including octyl sulfobetaine, caprylyl sulfobetaine, lauryl sulfobetaine, myristyl sulfobetaine, and palmityl sulfobetaine (SB3-16) against the harmful alga Alexandrium tamarense were observed. Betaine and the five sulfobetaines exhibited certain removal effects against A. tamarense with the highest removal efficiency by SB3-16. Hence, a series of modified clay, montmorillonite (MMT) intercalated by SB3-16 were prepared, and their removal efficiencies were evaluated. The organo-clay with 11 wt% of SB3-16 exhibited the highest removal efficiency against A. tamarense cells. Combining the environmentally benign nature of SB3-16 and the high efficiency of SB3-16 modified clay against A. tamarense, SB3-16 modified clay could be a favorable choice to control harmful algal blooms (HABs) of this species.

P-glycoprotein (P-gp), as an ATP-binding cassette transporter, can transport a variety of substrates across the cell membrane in human and animals, even in aquatic animals. Multixenobiotic resistance phenomenon (MXR) related to the P-gp has been identified and characterized in several aquatic organisms, however, the nature of this transporter and the structural basis for the resistance are still poorly understood. In this study, to provide an insight into the roles of P-gp in resistance of bivalve against environmental pollution and toxins, complete cDNA of P-gp gene in Crassostrea ariakensis was cloned and analyzed. The accumulation of okadaic acid (OA), a main component of diarrhetic shellfish poisoning (DSP) toxins, and expression of P-gp in gills, digestive glands and mantle of C. ariakensis , were detected upon exposure to Prorocentrum lima , a known producer of DSP toxins. The complete sequence of oyster P-gp showed a high identity to MDR/P-gp/ABCB proteins from other species and contained some classical features of ABCB transport proteins. Upon exposure to P. lima for 72 h, the OA level increased 2.5-fold in gills and 6.4-fold in digestive glands of C. ariakensis . Meanwhile, the expression of P-gp mRNA increased 2.4-fold in gills and decreased slightly in digestive glands. No significant difference in P-gp protein expression was found by western blot in all of the tissues analyzed in P. lima -exposed oysters. Taking all of our results into account, we speculate that P-gp likely plays a role in the response to DSP toxins in C. ariakensis .