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Donald M Anderson

Publications and source records attributed to Donald M Anderson.

7 recordsLinked to original sources
PubMed2006

Global transcriptional profiling of the toxic dinoflagellate Alexandrium fundyense using Massively Parallel Signature Sequencing.

BACKGROUND: Dinoflagellates are one of the most important classes of marine and freshwater algae, notable both for their functional diversity and ecological significance. They occur naturally as free-living cells, as endosymbionts of marine invertebrates and are well known for their involvement in "red tides". Dinoflagellates are also notable for their unusual genome content and structure, which suggests that the organization and regulation of dinoflagellate genes may be very different from that of most eukaryotes. To investigate the content and regulation of the dinoflagellate genome, we performed a global analysis of the transcriptome of the toxic dinoflagellate Alexandrium fundyense under nitrate- and phosphate-limited conditions using Massively Parallel Signature Sequencing (MPSS). RESULTS: Data from the two MPSS libraries showed that the number of unique signatures found in A. fundyense cells is similar to that of humans and Arabidopsis thaliana, two eukaryotes that have been extensively analyzed using this method. The general distribution, abundance and expression patterns of the A. fundyense signatures were also quite similar to other eukaryotes, and at least 10% of the A. fundyense signatures were differentially expressed between the two conditions. RACE amplification and sequencing of a subset of signatures showed that multiple signatures arose from sequence variants of a single gene. Single signatures also mapped to different sequence variants of the same gene. CONCLUSION: The MPSS data presented here provide a quantitative view of the transcriptome and its regulation in these unusual single-celled eukaryotes. The observed signature abundance and distribution in Alexandrium is similar to that of other eukaryotes that have been analyzed using MPSS. Results of signature mapping via RACE indicate that many signatures result from sequence variants of individual genes. These data add to the growing body of evidence for widespread gene duplication in dinoflagellates, which would contribute to the transcriptional complexity of these organisms. The MPSS data also demonstrate that a significant number of dinoflagellate mRNAs are transcriptionally regulated, indicating that dinoflagellates commonly employ transcriptional gene regulation along with the post-transcriptional regulation that has been well documented in these organisms.

Animals↗
PubMed2006

Fiber-optic microarray for simultaneous detection of multiple harmful algal bloom species.

Harmful algal blooms (HABs) are a serious threat to coastal resources, causing a variety of impacts on public health, regional economies, and ecosystems. Plankton analysis is a valuable component of many HAB monitoring and research programs, but the diversity of plankton poses a problem in discriminating toxic from nontoxic species using conventional detection methods. Here we describe a sensitive and specific sandwich hybridization assay that combines fiber-optic microarrays with oligonucleotide probes to detect and enumerate the HAB species Alexandrium fundyense, Alexandrium ostenfeldii, and Pseudo-nitzschia australis. Microarrays were prepared by loading oligonucleotide probe-coupled microspheres (diameter, 3 mum) onto the distal ends of chemically etched imaging fiber bundles. Hybridization of target rRNA from HAB cells to immobilized probes on the microspheres was visualized using Cy3-labeled secondary probes in a sandwich-type assay format. We applied these microarrays to the detection and enumeration of HAB cells in both cultured and field samples. Our study demonstrated a detection limit of approximately 5 cells for all three target organisms within 45 min, without a separate amplification step, in both sample types. We also developed a multiplexed microarray to detect the three HAB species simultaneously, which successfully detected the target organisms, alone and in combination, without cross-reactivity. Our study suggests that fiber-optic microarrays can be used for rapid and sensitive detection and potential enumeration of HAB species in the environment.

Base Sequence↗
PubMed2005

Hydrogen peroxide is not the cause of fish kills associated with Chattonella marina: cytological and physiological evidence.

Chattonella marina, a harmful algal bloom (HAB) causative species, was used to study the mortality, physiology, and pathology of a marine stenohaline fish, goldlined seabream exposed to the toxic alga. The median lethal time (LT50) was 3 h upon exposure to 8000 cells/ml of C. marina. Significant induction of filamental chloride cells (CCs) [i.e. increases in CC fractional area and in the volume density of CCs], concomitant with significant reduction of blood osmolality, were found in C. marina treated fish. To verify whether the toxicity of C. marina was mediated through oxidative stress, a hydrogen peroxide exposure experiment was carried out and the toxicity as well as cytological and physiological changes were compared with the C. marina treatment. Hydrogen peroxide at a concentration of 500 microM H2O2, (i.e. 25 times higher than that produced by 8000 cells/ml of C. marina (20 microM H2O2)) was unable to induce similar CC alterations and osmoregulatory impairment in fish as observed in the C. marina treatment. Non-specific membrane damage such as severe loss of microvilli projections on the CC apical opening and rupture of epithelial membranes in the lamellae were observed. The LT50 was 6 h, two times longer than that with 8000 cells/ml of C. marina. Based on the cytological and physiological evidence and toxicity data, the mechanism by which C. marina kills fish appears to be very different from that caused by H2O2/ROS. Osmoregulatory distress is the major cause of fish death upon exposure to C. marina.

Analysis of Variance↗
PubMed2004

The loss of PSP toxin production in a formerly toxic Alexandrium lusitanicum clone.

Toxin production has always been considered a constitutive characteristic of dinoflagellates in the genus Alexandrium. Here we demonstrate that saxitoxin production can be lost by an Alexandrium species during routine culture maintenance. This is the first report of any marine saxitoxin-producing alga ever to have completely lost the ability to produce toxins. A clonal toxic isolate of Alexandrium lusitanicum from Portugal has been maintained in culture since 1962. In 1992, a subculture was established and sent to a different laboratory. Recent comparisons of the parental strain and the subculture revealed that the former had lost its toxicity, whereas the latter still produces saxitoxins. This loss of toxicity was confirmed by three independent toxin detection methods: mouse bioassay, mouse neuroblastoma assay and HPLC. Sequence analyses of different rRNA domains demonstrated that the toxic and non-toxic cultures are genetically identical for those markers. Morphological analysis showed that both cultures have the same plate tabulation and are A. lusitanicum. These results strongly argue that the loss of toxicity is not a result of a culturing artifact or mistake, such as mislabeling or contamination. The clonal cultures also show a significant difference in growth. Possible explanations for the change include genetic mutations or the effects of prolonged treatment of the non-toxic culture with antibiotics.

Animals↗
PubMedDate not supplied

Controlling harmful algal blooms through clay flocculation.

The potential use of clays to control harmful algal blooms (HABs) has been explored in East Asia, Australia, the United States, and Sweden. In Japan and South Korea, minerals such as montmorillonite, kaolinite, and yellow loess, have already been used in the field effectively, to protect fish mariculture from Cochlodinium spp. and other blooms. Cell removal occurs through the flocculation of algal and mineral particles, leading to the formation of larger aggregates (i.e. marine snow), which rapidly settle and further entrain cells during their descent. In the U.S., several clays and clay-rich sediments have shown high removal abilities (e.g. > 80% cell removal efficiency) against Karenia brevis, Heterosigma akashiwo, Pfiesteria piscicida and Aureococcus anophagefferens. In some cases, the removal ability of certain clays was further enhanced with chemical flocculants, such as polyaluminum chloride (PAC), to increase their adhesiveness. However, cell removal was also affected by bloom concentration, salinity, and mixing. Cell mortality was observed after clay addition, and increased with increasing clay concentration, and prolonged exposure to clays in the settled layer. Mesocosm, field enclosure, and flume experiments were also conducted to address cell removal with increasing scale and flow, water-column impacts, and the possible benthic effects from clay addition. Results from these studies will be presented, especially those in regards to water quality, seawater chemistry, bottom erodibility and faunal impacts in the benthos. At this time, clay dispersal continues to be a promising method for controlling HABs and mitigating their impacts based on existing information and experimental data.

Aluminum Hydroxide↗
PubMedDate not supplied

Sterols of the syndinian dinoflagellate Amoebophrya sp., a parasite of the dinoflagellate Alexandrium tamarense (Dinophyceae).

Several harmful photosynthetic dinoflagellates have been examined over past decades for unique chemical biomarker sterols. Little emphasis has been placed on important heterotrophic genera, such as Amoebophrya, an obligate, intracellular parasite of other, often harmful, dinoflagellates with the ability to control host populations naturally. Therefore, the sterol composition of Amoebophrya was examined throughout the course of an infective cycle within its host dinoflagellate, Alexandrium tamarense, with the primary intent of identifying potential sterol biomarkers. Amoebophrya possessed two primary C(27) sterols, cholesterol and cholesta-5,22Z-dien-3beta-ol (cis-22-dehydrocholesterol), which are not unique to this genus, but were found in high relative percentages that are uncommon to other genera of dinoflagellates. Because the host also possesses cholesterol as one of its major sterols, carbon-stable isotope ratio characterization of cholesterol was performed in order to determine whether it was produced by Amoebophrya or derived intact from the host. Results indicated that cholesterol was not derived intact from the host. A comparison of the sterol profile of Amoebophrya to published sterol profiles of phylogenetic relatives revealed that its sterol profile most closely resembles that of the (proto)dinoflagellate Oxyrrhis marina rather than other extant genera.

Animals↗