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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 43 (1996), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 45 (1998), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We compared 16S-like ribosomal RNA (rRNA) coding regions of samples of the solitary spumellarian radiolarian Thalassicolla nucleata collected from the Sargasso Sea and the Pacific Ocean. Sequences derived from these locations showed variability in both length and base-pair composition. This level of sequence variability is similar to the degree of variability reported in the literature for species- or even genus-level distinctions. Explanations for our results include multiple alleles for the rRNA gene, or the existence of multiple species of Thalassicolla that are morphologically indistinguishable. The seven existing descriptions of Thalassicolla species, including T. nucleata, are discussed in view of these molecular findings and with reference to our current understanding of the physiology and life cycle of the spumellarian radiolaria.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 28 (1992), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. The occurrence and grazing activity of mixotrophic (phagotrophic) algae in three icecovered freshwater lakes of different trophic status were examined (oligotrophic Lake Giles, mesotrophic Lake Lacawac, eutrophic Lake Waynewood), Microbial population densities were low (4.1–7.2 × 105 bacteria ml−1 and 1.2–2.4 × 103 nanoplanktonic protists ml−1). All three nanoplankton communities were dominated by chloroplast-bearing forms (60–96%).2. Mixotrophs formed up to 48% of the phototrophic nanoplankton in Lake Lacawac and were responsible for up to ∼90% of the observed uptake of bacteria-sized particles. The abundance of mixotrophic algae in Lakes Giles and Waynewood were extremely low (3 and 2% of the phototrophic algae, respectively), and heterotrophs dominated nanoplankton bacterivory.3. The overall impact of nanoplankton feeding activity on the bacterial assemblage was low under the ice in Lakes Giles and Waynewood. Removal rates of bacteria based on our particle uptake experiments were 1.0 and 4.0% of the bacterial standing stock day−1 in these lakes, respectively. Removal rates were higher in Lake Lacawac and ranged from 4.9 to 11% of the bacterial standing stock day−1 on 2 successive sampling days.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Heterotrophic nanoprotozoans are known to be important components of the marine planktonic ecosystem as the primary consumers of bacterial biomass10 and recyclers of major nutrients11'12. These grazers consume particles and colloids in the 0.2-1-um size class13, which in sea water contains a ...
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The time scales involved in the transition between phototrophic and phagotrophic modes of nutrition were examined in the mixotrophic chrysophytePoterioochromonas malhamensis. Phagotrophy began almost immediately when bacteria were added to phototrophically growing cultures of the alga, and chlorophylla concentration per cell in these cultures decreased over a 24-hour period. Chlorophyll concentrations per cell began to increase when bacteria were grazed to a density of approximately 106 ml−1, but after more than 24 hours they had not returned to the higher chlorophyll concentrations observed in the phototrophically grown cultures. Bacterivory was the dominant mode of nutrition in all cultures containing heat-killed bacteria. Photosynthesis did not contribute more than ≈7% of the total carbon budget of the alga when in the presence of abundant heat-killed bacteria. Bacterial density was the primary factor influencing the ability ofP. malhamensis to feed phagotrophically, while light intensity, pH, and the presence of dissolved organic matter had no effect on phagotrophy. We conclude thatP. malhamensis is capable of phagotrophy at all times. In contrast, phototrophy is inducible in the light during starvation and is a long-term survival strategy for this mixotrophic alga (i.e., it operates on time scales greater than a diel cycle).
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mixotrophic (bacterivorous), freshwater chrysophyte Dinobryon cylindricum was cultured under a variety of light regimes and in bacterized and axenic cultures to investigate the role of phototrophy and phagotrophy for the growth of this alga. D. cylindricum was found to be an obligate phototroph. The alga was unable to survive in continuous darkness even when cultures were supplemented with high concentrations of bacteria, and bacterivory ceased in cultures placed in the dark for a period longer than one day. Axenic growth of the alga was poor even in an optimal light regime. Live bacteria were required for sustained, vigorous growth of the alga in the light. Carbon (C), nitrogen (N), and phosphorus (P) budgets determined for the alga during growth in bacterized cultures indicated that bacterial biomass ingested by the alga may have contributed up to 25% of the organic carbon budget of the alga. Photosynthesis was the source of most (⩾75%) of the organic carbon of the alga. D. cylindricum populations survived but did not grow when cultured in a continuous low light intensity (30 μE m−2 sec−1), or in a light intensity of 150 μE m−2 sec−1 for only two hours each day. Net efficiency of incorporation of bacterial C, N, and P into algal biomass under these two conditions was zero (i.e., no net algal population growth). We conclude that the primary function of bacterivorous behavior in D. cylindricum may be to provide essential growth factor(s) or major nutrients for photosynthetic growth, or to allow for the survival of individuals during periods of very low light intensity or short photoperiod.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-904X
    Keywords: calcium pectinate ; colon targeting ; gamma scintigraphy ; 'proof of concept.'
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The aim of the present study was to provide 'proof of concept' data in man for novel polysaccharide preparations designed for colonic drug delivery using gamma scintigraphy. Methods. Two placebo calcium pectinate matrix tablet formulations were studied: one contained calcium pectinate and pectin (CaP/P) and was designed to rapidly disintegrate in the ascending colon, the other contained calcium pectinate and guar gum (CaP/GG) and was designed to disintegrate more slowly, releasing its contents throughout the ascending and transverse colon. Both formulations were enteric coated in order to protect them from the stomach. Ten healthy volunteers received either a CaP/P or CaP/GG tablet, in a randomised cross-over study. Transit and disintegration of the radiolabelled formulations was followed by gamma scintigraphy. Rat studies were conducted in order to verify that the expected colonic degradation of the polysaccharide formulations was as a consequence of bacterial enzyme attack. Results. Thein vivo clinical study confirmed the results obtained in the rat and bench in vitro fermentation models; complete tablet disintegration for Formulation CaP/GG appeared to be slower than that of Formulation CaP/P and the time and the location of complete tablet disintegration was more reproducible with Formulation CaP/P compared to Formulation CaP/GG. Conclusions. These results provide 'proof of concept' data for the use of calcium pectinate preparations for drug delivery to the colon and highlight the value of scintigraphy in focusing the development strategy for colonic targeting preparations.
    Type of Medium: Electronic Resource
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  • 8
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Harmful Algae 78 (2018): 129-141, doi:10.1016/j.hal.2018.08.006.
    Description: Monterey Bay, California experiences near-annual blooms of Pseudo-nitzschia that can affect marine animal health and the economy, including impacts to tourism and commercial/recreational fisheries. One species in particular, P. australis, has been implicated in the most toxic of events, however other species within the genus can contribute to widespread variability in community structure and associated toxicity across years. Current monitoring methods are limited in their spatial coverage as well as their ability to capture the full suite of species present, thereby hindering understanding of HAB events and limiting predictive accuracy. An integrated deployment of multiple in situ platforms, some with autonomous adaptive sampling capabilities, occurred during two divergent bloom years in the bay, and uncovered detailed aspects of population and toxicity dynamics. A bloom in 2013 was characterized by spatial differences in Pseudo39 nitzschia populations, with the low-toxin producer P. fraudulenta dominating the inshore community and toxic P. australis dominating the offshore community. An exceptionally toxic bloom in 2015 developed as a diverse Pseudo-nitzschia community abruptly transitioned into a bloom of highly toxic P. australis within the time frame of a week. Increases in cell density and proliferation coincided with strong upwelling of nutrients. High toxicity was driven by silicate limitation of the dense bloom. This temporal shift in species composition mirrored the shift observed further north in the California Current System off Oregon and Washington. The broad scope of sampling and unique platform capabilities employed during these studies revealed important patterns in bloom formation and persistence for Pseudo-nitzschia. Results underscore the benefit of expanded biological observing capabilities and targeted sampling methods to capture more comprehensive spatial and temporal scales for studying and predicting future events.
    Description: This work was supported by the National Oceanic and Atmospheric Administration (NA11NOS4780055, NA11NOS4780056, NA11NOS4780030) and a fellowship to H. Bowers from the Packard Foundation.
    Keywords: Pseudo-nitzschia ; Monterey Bay ; Species diversity ; Harmful algal bloom ; Domoic acid ; Environmental Sample Processor ; ARISA
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 9
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Protist 167 (2016): 106–120, doi:10.1016/j.protis.2016.01.003.
    Description: Arranging organisms into functional groups aids ecological research by grouping organisms (irrespective of phylogenetic origin) that interact with environmental factors in similar ways. Planktonic protists traditionally have been split between photoautotrophic “phytoplankton” and phagotrophic “microzooplankton”. However, there is a growing recognition of the importance of mixotrophy in euphotic aquatic systems, where many protists often combine photoautotrophic and phagotrophic modes of nutrition. Such organisms do not align with the traditional dichotomy of phytoplankton and microzooplankton. To reflect this understanding, we propose a new functional grouping of planktonic protists in an eco-physiological context: (i) phagoheterotrophs lacking phototrophic capacity, (ii) photoautotrophs lacking phagotrophic capacity, (iii) constitutive mixotrophs (CMs) as phagotrophs with an inherent capacity for phototrophy, and (iv) non-constitutive mixotrophs (NCMs) that acquire their phototrophic capacity by ingesting specific (SNCM) or general non-specific (GNCM) prey. For the first time, we incorporate these functional groups within a foodweb structure and show, using model outputs, that there is scope for significant changes in trophic dynamics depending on the protist functional type description. Accordingly, to better reflect the role of mixotrophy, we recommend that as important tools for explanatory and predictive research, aquatic food-web and biogeochemical models need to redefine the protist groups within their frameworks.
    Description: This work was funded by grants to KJF and AM from the Leverhulme Trust (International Network Grant F00391 V) and NERC (UK) through its iMARNET programme NE/K001345/1.
    Keywords: Plankton functional types (PFTs) ; Phagotroph ; Phototroph ; Mixotroph ; Phytoplankton ; Microzooplankton
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 10
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    Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu
    Publication Date: 2022-05-26
    Description: Dataset: 18S rRNA gene tag sequences from DNA and RNA
    Description: Raw DNA and RNA V4 tag sequences include spatially and temporally distinct samples from coastal California. Samples were collected in Niskin bottles with a CTD rosette at the San Pedro Ocean Time-series (SPOT) between April of 2013 and January of 2014. This dataset contains sequence data accession numbers and metadata for the National Center for Biotechnology Information (NCBI) Sequence Read Archive (SRA) database (SRA Study ID: SRP070577, BioProject: PRJNA311248). For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/745527
    Description: NSF Division of Ocean Sciences (NSF OCE) OCE-1737409
    Repository Name: Woods Hole Open Access Server
    Type: Dataset
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