Transient effect of bisphenol A (BPA) and di-(2-ethylhexyl) phthalate (DEHP) on the cosmopolitan marine diatom Chaetoceros decipiens-lorenzianus.

Incubation under controlled laboratory conditions were performed to assess the toxic effects of two plastic derived chemicals, bisphenol A (BPA) and di-(2-ethylhexyl) phthalate (DEHP), on the growth, photosynthetic efficiency and photosynthetic activity of the cosmopolitan diatom Chaetoceros decipiens-lorenzianus. Non-axenic diatom cells were exposed to concentrations of BPA and DEHP (separately and in mixture), mimicking concentrations observed in contaminated marine ecosystems, for seven days. Upon short-term exposure (i.e., during the first 48 h), BPA and DEHP induced a slight but significant stimulation of biomass and photosynthetic activity relative to the control, whereas, no significant impact was observed on the photosynthetic efficiency. Nevertheless, this pattern was transient. The stimulation was followed by a return to control conditions for all treatments at the end of incubation. These results showed that the cosmopolitan diatom Chaetoceros was not impacted by representative in situ concentrations of plastic derivatives, thus confirming its ability to thrive in coastal anthropogenic environments.

TAXONOMIC REVISION OF THE DINOFLAGELLATE AMPHIDOMA CAUDATA: TRANSFER TO THE GENUS AZADINIUM (DINOPHYCEAE) AND PROPOSAL OF TWO VARIETIES, BASED ON MORPHOLOGICAL AND MOLECULAR PHYLOGENETIC ANALYSES(1).

The systematic position of Amphidoma caudata Halldal within the genus Amphidoma has remained uncertain as a result of its plate formula and the absence of molecular phylogenetic data. Also, this thecate dinoflagellate taxon has been used to designate two distinct morphotypes. The present study aims to clarify the generic affiliation of Amphidoma caudata and the taxonomic value of two different morphotypes M1 and M2. The new examination of the plate formula using SEM showed that it was the same for both morphotypes and that it corresponded to the tabulation of the recent erected genus Azadinium Elbrächter et Tillmann. Morphometric analysis, using cell size, length of apical projection in conjunction with the cell length, and the ratio of horn and spine showed that M1 and M2 formed two distinct groups. These results were supported by a molecular approach, revealing notable differences in the sequences of LSU rDNA and ITS region between these two morphotypes. Phylogenetic analyses inferred either from LSU and combined SSU, ITS region and COI data positioned M1 and M2 in a sister cluster of Azadinium species while Amphidoma languida Tillmann, Salas et Elbrächter, the only species of Amphidoma for which sequence data were available, was situated in a basal position of the Azadinium clade. Thus, we propose the transfer of Amphidoma caudata to the genus Azadinium and, consequently, the rehabilitation of the original tabulation of the genus Amphidoma Stein. To discriminate the two morphotypes, we propose a rank of variety with the following designations: Azadinium caudatum var. caudatum and Azadinium caudatum var. margalefii.

Syntheses, in vitro antibacterial and cytotoxic activities of a series of 3-substituted succinimides.

We have synthesized a series of 3-substituted succinimides and their in vitro antibacterial activities have been tested towards Gram-positive and Gram-negative bacteria from the ATCC collection. Some of them possess significant antibacterial activity against Gram-positive organisms (Staphylococcus aureus ATCC 25923 and Enterococcus faecalis ATCC 29212) but all are poorly active or inactive against Gram-negative organisms (Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853). The compounds with the lowest minimal inhibitory concentrations (esters of 3-hydroxy succinimides) are also the most cytotoxic against green monkey Vero cell line (ATCC CCL-81) and could explain that perhaps apoptosis should be implicated in eukaryotic cell cytotoxicity of succinimides.

Synthesis and antimicrobial activities of N-substituted imides.

In the field of our research programs concerning novel antimicrobial agents, a series of N-substituted imides was synthesized. These compounds were obtained by cyclization of amido-acids in acetic anhydride/sodium acetate or hexamethyldisilazane/zinc bromide for the hydroxy-aromatic derivatives. The hydroxy-alkyl maleimides were directly prepared by condensation of the corresponding amino-alcohol with maleic anhydride in boiling toluene. Most of N-substituted maleimides showed an interesting antimicrobial activity towards bacteria from the ATCC collection (Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853) but the MIC values for P. aeruginosa were always high (128 microg/ml). The imides with alkyl substituents showed higher activities than aromatic analogues with MIC values in the range of 8-32 microg/ml. Comparatively, succinimides were practically inactive.

Antifouling activities of N-substituted imides: antimicrobial activities and inhibition of Mytilus edulis phenoloxidase.

In the search for novel biodegradable antifouling agents, a series of imides (N-substituted maleimides and succinimides) have been synthesized. A large majority of N-substituted maleimides and succinimides showed an antimicrobial activity toward gram-positive and gram-negative bacteria and fungi of marine origin with minimal inhibition concentrations in the range of 6 to 24 microg/ml. The imides with an alkyl substituent showed higher activities than aromatic analogues, but structure-activity relationships were not clearly established. Some compounds were powerful inhibitors of Mytilus edulis phenoloxidase. This inhibition was noncompetitive as demonstrated with 2 maleimides, a 3-acetoxy succinimide and a succinimide. Thus, this family of products has potential interest as antifouling agents.