Dinoflagellate Vulcanodinium Rugosum Research Articles

Cytotoxicity, Fractionation and Dereplication of Extracts of the Dinoflagellate Vulcanodinium rugosum, a Producer of Pinnatoxin G

Pinnatoxin G (PnTX-G) is a marine toxin belonging to the class of cyclic imines and produced by the dinoflagellate Vulcanodinium rugosum. In spite of its strong toxicity to mice, leading to the classification of pinnatoxins into the class of “fast-acting toxins”, its hazard for human health has never been demonstrated. In this study, crude extracts of V. rugosum exhibited significant cytotoxicity against Neuro2A and KB cells. IC50 values of 0.38 µg mL−1 and 0.19 µg mL−1 were estimated on Neuro2A cells after only 24 h of incubation and on KB cells after 72 h of incubation, respectively. In the case of Caco-2 cells 48 h after exposure, the crude extract of V. rugosum induced cell cycle arrest accompanied by a dramatic increase in double strand DNA breaks, although only 40% cytotoxicity was observed at the highest concentration tested (5 µg mL−1). However, PnTX-G was not a potent cytotoxic compound as no reduction of the cell viability was observed on the different cell lines. Moreover, no effects on the cell cycle or DNA damage were observed following treatment of undifferentiated Caco-2 cells with PnTX-G. The crude extract of V. rugosum was thus partially purified using liquid-liquid partitioning and SPE clean-up. In vitro assays revealed strong activity of some fractions containing no PnTX-G. The crude extract and the most potent fraction were evaluated using full scan and tandem high resolution mass spectrometry. The dereplication revealed the presence of a major compound that could be putatively annotated as nakijiquinone A, N-carboxy-methyl-smenospongine or stachybotrin A, using the MarinLit™ database. Further investigations will be necessary to confirm the identity of the compounds responsible for the cytotoxicity and genotoxicity of the extracts of V. rugosum.

Portimine: a bioactive metabolite from the benthic dinoflagellate Vulcanodinium rugosum

Portimine, a new polycyclic ether toxin containing a cyclic imine moiety, was isolated from the marine benthic dinoflagellate Vulcanodinium rugosum collected from Northland, New Zealand. The structure of portimine, including the relative configurations, was elucidated by spectroscopic analyses. The cyclic imine moiety consists of an unprecedented five-membered ring with a spiro-link to a cyclohexene ring. This is the only structural similarity to the pinnatoxin group of polycyclic ethers also produced by V. rugosum, which all contain a six-membered cyclic imine ring. The LD50 of portimine to mice by intraperitoneal injection was 1570 μg/kg, indicating a much lower toxicity than many other cyclic imine shellfish toxins. In contrast, portimine was highly toxic to mammalian cells in vitro with an LC50 to P388 cells of 2.7 nM, and activation of caspases indicating apoptotic activity.

Progress and Pollution: Port Cities Prepare for the Panama Canal Expansion

Early in the planning of the Panama Canal, Navy Commander Thomas Oliver Selfridge, Jr., wrote that “advantageous as an interoceanic canal would be to the commercial welfare of the whole world, it is doubly so for the necessities of American interests.”1 And indeed, since the Canal opened in 1914, it has been the main conduit for ocean-going ships carrying trade worldwide. Today the United States ranks number one in tons of cargo passing through the Canal (China ranks number two).2 In 2011 nearly 13,000 ocean-going cargo ships made the passage.3 Starting in the late 1950s (and expanding rapidly thereafter), internationally traded goods started being shipped in large metal containers, making it possible to load and unload cargo by machine instead of by hand and spurring the manufacture of larger ships.4 “Panamax” ships were designed to be just small enough to squeeze through the locks of the Canal.5 Today, even larger ships—called “post-Panamax” because they are too large to fit through the Canal6—make up 16% of the world’s container fleet but account for nearly half the fleet’s cargo capacity.7 To allow these larger ships to transit the Canal and increase its ability to handle higher volumes of ships, Panama is building a third set of locks, with construction expected to be finished in 2015.7 The Panama Canal expansion has sparked the competitive imagination of East Coast and Gulf Coast (EC/GC) port authorities, who hope to capture some of the 70% of U.S. imports currently controlled by West Coast (WC) ports.8 Ports typically make their revenues through leases with shipping lines, wharfage fees, and tariffs. So the more containers a port handles, the more money it can make. Experts at the U.S. Army Corps of Engineers (USACE) call the Panama Canal expansion a likely “game changer” for U.S. trade, potentially redistributing the market share of each coast’s ports, as well as opening up new import and export markets for agricultural and other products along inland waterways.7 Some have estimated that container volumes at EC/GC ports could more than double from 2012 to 2029.7 But with this growth come questions about what major initiatives to expand cargo capacity could mean for public health in these port cities.

Dinoflagellate Vulcanodinium rugosum identified as the causative organism of pinnatoxins in Australia, New Zealand and Japan

Rhodes L., Smith K., Selwood A., McNabb P., Munday R., Suda S., Molenaar S. and Hallegraeff G. 2011. Dinoflagellate Vulcanodinium rugosum identified as the causative organism of pinnatoxins in Australia, New Zealand and Japan. Phycologia 50: 624–628. DOI: 10.2216/11-19.1The producers of pinnatoxins E and F were first identified through systematic light microscopy-mass spectrometry (LC-MS) screening of New Zealand (NZ) dinoflagellate isolates. Pinnatoxins E, F and G were subsequently detected for South Australian (AUS) isolates, and a pinnatoxin G producer was recently identified from Okinawa, Japan. The NZ, AUS and Japanese isolates appear morphologically identical to Mediterranean field samples recently described as Vulcanodinium rugosum. Motile forms (24–32 µm long, 20–30 µm wide) have a wide, deeply incised cingulum displaced by 17% of the cell length and a deep sulcus. Photosynthetic motile cells have the same distinctive apical pore complex with raised collar and short canal plate. The reticulate thecal ornamentation resembles that of Bysmatrum because the three intercalary plates are connected. The posterior sulcal plate Sp does not touch the cingulum (as in Bysmatrum, Pentapharsodinium and Ensiculifera). The plate formula for the NZ, AUS and Japanese isolates is Po, X, 4′, 3a, 7″, 6c (5c + T), 5s, 5′″, 2″″. The dominant non-motile life-cycle stage comprises clusters of brown to black, spherical, unornamented, non-calcareous division cells (30–35 µm diameter). Genetically these isolates fall within the Peridiniales, closely related to the calciodinellid genera, Pentapharsodinium, Ensiculifera and Scrippsiella. The large subunit (LSU) rDNA and internal transcribed spacer (ITS) sequences exhibit sequence differences compared to each other and to the French field material (96–97% LSU and 84–88% ITS similarity, respectively). This variation and pinnatoxin profile differences suggest a possible species complex.