Papers by Stephen S. Bates
The domoic acid (DA) producing pennate diatom Nitzschia pungens f. multiseries (clone POM, from N... more The domoic acid (DA) producing pennate diatom Nitzschia pungens f. multiseries (clone POM, from Nova Scotia, Canada) was grown at photon flux densities (PFD) of 80 and 180 IlE m-2 S-1 and 5°,10°,15°,20°and 25°C. The growth rate (Il) increased from 0.25 d" at 5°C to a maximum of 0.65 d-1 at 20°C; it was 0.60 d-' at 25°C. There was no significant difference in Il between cultures grown at the two PFD at any temperature. The 0 10 for Il was 1.76 and 2.06 between 5°-15°C and 10°-20°C, respectively. The highest stationary phase cell concentrations occurred at 5°to 15°C and decreased at 20°to 25°C. The DA production rate increased from 0.01 pg DA cell" d-1 at 5°C to 0.51 pg DA ceW' d-' at 25°C; the 0 10 was 19.6 and 2.11 between 5°-15°C and 15°-25°C, respectively. Scanning electron microscopy showed that cells at 5°and 15°C had 3 -4 rows of poroids between the costae. In contrast, cells at 25°C had 2 -3 rows of poroids. The higher cell concentrations at lower temp...
Journal of Photochemistry and Photobiology A: Chemistry, 2008
Domoic acid (DA) is a water-soluble marine neurotoxin produced and released by Pseudo-nitzschia s... more Domoic acid (DA) is a water-soluble marine neurotoxin produced and released by Pseudo-nitzschia species. It is remarkably pervasive in North American coastal waters, where it is a threat to public health and some marine life, and has resulted in severe economic losses ...
The domoic acid (DA) producing pennate diatom Nitzschia pungens f. multiseries (clone POM, from N... more The domoic acid (DA) producing pennate diatom Nitzschia pungens f. multiseries (clone POM, from Nova Scotia, Canada) was grown at photon flux densities (PFD) of 80 and 180 IlE m-2 S-1 and 5°,10°,15°,20° and 25°C. The growth rate (Il) increased from 0.25 d" at 5°C to a maximum of 0.65 d- 1 at 20°C; it was 0.60 d-' at 25°C.
Journal of Fish Biology, 1997
Atlantic mackerel Scomber scombrus are known to be lethal vectors of paralytic shellfish poisonin... more Atlantic mackerel Scomber scombrus are known to be lethal vectors of paralytic shellfish poisoning (PSP) toxins to predators. To elucidate dynamics of PSP toxin accumulation in this species, mackerel were sampled in the Gulf of St Lawrence from May to October 1993. Mackerel appear to retain toxins (saxitoxin, gonyautoxins 2 and 3) year-round. The toxin content of the liver, as determined by high performance liquid chromatography, increased significantly with fish age (r 2 =0•40) and length (r 2 =0•52), suggesting that mackerel progressively accumulate PSP toxins throughout their life. The toxin content of the liver also increased significantly during the summer feeding sojourn in the Gulf of St Lawrence. Comparison of profiles of saxitoxin derivatives indicated that zooplankton were the likely source of PSP toxins found in mackerel. The mean .. toxin content was 17•4 10•6 nmol liver 1 and the mean .. PSP toxicity was 112•4 67•0 g saxitoxin equivalents 100 g 1 liver wet weight (n=247).
The increased bacterial resistance to antibiotics has caused global concern, prompting the search... more The increased bacterial resistance to antibiotics has caused global concern, prompting the search for new compounds. Because of their abundance and diversity, marine phytoplankton are an important potential source of such compounds. Research on dinoflagellates has led to the discovery of inhibitors of bacterial growth. The marine dinoflagellate Lingulodinium polyedrum blooms in different regions of the world, including Mexico, and is also known to regulate the growth of other species in coastal waters. Here, we investigated the taxonomy of this dinoflagellate and characterized the ability of its extracts to inhibit the growth of two bacteria of medical importance (Vibrio vulnificus and Staphylococcus aureus). Taxonomic characterization was performed by PCR and gene amplification of ITS, and confirmed that the species isolated off the Pacific coast of Mexico was L. polyedrum. To prove the inhibitory effect of L. polyedrum extracts, cultures were harvested by centrifuga-tion. Pellets from three cellular abundances were extracted with water, methanol, hexane and chloroform. The experiments on V. vulnificus showed a high growth inhibition for the four extracts, ranging from 77 to 98 %. Surprisingly, the growth inhibition was lower when the extracts originated from a higher L. polyedrum cell abundance , ranging from 0 to 34 %. For S. aureus, the growth inhibition was also high, but not statistically different for all extracts and cell abundances, ranging from 62 to 99 %. This study obtained promising results for future pharmacological applications. Our Mexican strain of L. polyedrum did not produce any detectable yessotoxins.
The distribution of the toxic pennate diatom Nitzschia was investigated at four mangrove areas al... more The distribution of the toxic pennate diatom Nitzschia was investigated at four mangrove areas along the coastal brackish waters of Peninsular Malaysia. Eighty-two strains of N. navis-varingica were isolated and established, and their identity confirmed morphologically and molecularly. Frustule morphological characteristics of the strains examined are identical to previously identified N. navis-varingica, but with a sightly higher density of the number of areolae per 1 mm (4–7 areolae). Both LSU and ITS rDNAs phylogenetic trees clustered all strains in the N. navis-varingica clade, with high sequence homogeneity in the LSU rDNA (0–0.3%), while the intraspecific divergences in the ITS2 data set reached up to 7.4%. Domoic acid (DA) and its geometrical isomers, isodomoic A (IA) and isodomoic B (IB), were detected in cultures of N. navis-varingica by FMOC-LC-FLD, and subsequently confirmed by LC–MS/MS, with selected ion monitoring (SIM) and multiple reaction monitoring (MRM) runs. DA contents ranged between 0.37 and 11.06 pg cell À1. This study demonstrated that the toxigenic euryhaline diatom N. navis-varingica is widely distributed in Malaysian mangrove swamps, suggesting the risk of amnesic shellfish poisoning and the possibility of DA contamination in the mangrove-related fisheries products.
The increased bacterial resistance to antibiotics has caused global concern, prompting the search... more The increased bacterial resistance to antibiotics has caused global concern, prompting the search for new compounds. Because of their abundance and diversity, marine phytoplankton are an important potential source of such compounds. Research on dinoflagellates has led to the discovery of inhibitors of bacterial growth. The marine dinoflagellate Lingulodinium polyedrum blooms in different regions of the world, including Mexico, and is also known to regulate the growth of other species in coastal waters. Here, we investigated the taxonomy of this dinoflagellate and characterized the ability of its extracts to inhibit the growth of two bacteria of medical importance (Vibrio vulnificus and Staphylococcus aureus). Taxonomic characterization was performed by PCR and gene amplification of ITS, and confirmed that the species isolated off the Pacific coast of Mexico was L. polyedrum. To prove the inhibitory effect of L. polyedrum extracts, cultures were harvested by centrifuga-tion. Pellets from three cellular abundances were extracted with water, methanol, hexane and chloroform. The experiments on V. vulnificus showed a high growth inhibition for the four extracts, ranging from 77 to 98 %. Surprisingly, the growth inhibition was lower when the extracts originated from a higher L. polyedrum cell abundance , ranging from 0 to 34 %. For S. aureus, the growth inhibition was also high, but not statistically different for all extracts and cell abundances, ranging from 62 to 99 %. This study obtained promising results for future pharmacological applications. Our Mexican strain of L. polyedrum did not produce any detectable yessotoxins.
Domoic acid (DA), the responsible agent for Amnesic Shellfish Poisoning, contains three carboxyli... more Domoic acid (DA), the responsible agent for Amnesic Shellfish Poisoning, contains three carboxylic acid residues that could potentially bind trace metals such as iron. To investigate if DA production was affected by the iron status of the cell, replicate cultures of the diatom Pseudo-nitzschia multiseries were grown under tracemetal clean conditions containing 0, 0.12 µM and 11.7 µM added iron. All three iron treatments showed similar initial growth rates and resulted in stationary phase densities of >10 5 cells mL -1 after 10 days in culture. In contrast, DCMU-enhanced fluorescence indicated that the cultures without added iron were iron-limited by day 18, as evidenced by an Fv/Fm ratio of 0.2 as compared to the iron-replete cultures (11.7 µM Fe) with a ratio of 0.5 throughout the culture period. Cultures without added iron showed a marked drop in the cellular chlorophyll a content in stationary phase and never produced more than 5 pg DA cell -1 (<1000 ng mL -1 ). In contrast, iron-replete cells contained 5-10 times more chlorophyll a per cell, and DA production increased steadily throughout stationary phase to nearly 50 pg cell -1 (5500 ng mL -1 ). The intermediate level of added iron (0.12 µM) showed an intermediate response. These results indicate that the lack of available iron strongly inhibits the ability of P. multiseries to produce DA. The decrease in DA production, chlorophyll a synthesis, and photosynthetic efficiency suggest that DA is not produced as a chelator to increase the availability of iron to the cells. The cause of this decrease is unknown, but the biosynthesis of DA requires both nitrogen and energy, two resources that are likely to be limiting under iron-deficient conditions.
Nova Hedwigia
2000): Fine structure of the gamete, auxospore and initial cell in the pennate diatom Pseudo-nitr... more 2000): Fine structure of the gamete, auxospore and initial cell in the pennate diatom Pseudo-nitrschia multiseries (Bacillariophyta). -Nova Hedwigia 71: 337-357.
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Papers by Stephen S. Bates