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  • 1
    Electronic Resource
    Electronic Resource
    Grazing of attached bacteria by heterotrophic microflagellates (1987)
    Springer
    Microbial ecology 13 (1987), S. 203-218 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Four species of heterotrophic microflagellates were examined for their ability to graze attached and unattached bacteria. The species tested displayed pronounced differences in their ability to graze the bacteriumPseudomonas halodurans attached to chitin particles. Two species of microflagellates (Monas andCryptobia sp.) efficiently grazed unattached bacteria but showed little or no ability to graze attached or aggregated cells. In contrast,Rhynchomonas nasuta andBodo sp. showed marked preferences for attached and aggregated bacteria and a limited ability to graze unattached cells. The density of attached bacteria was reduced by an order of magnitude due to grazing byBodo andR. nasuta, even though the density of unattached bacteria was ∼5–90× the density of attached cells. The maximum densities attained by microflagellates in the cultures were related to the density of unattached bacteria forMonas andCryptobia but not forBodo andR. nasuta. Growth of the latter two species appeared to be related to the density of attached or aggregated bacteria. Based on the results of these experiments, it is concluded that the pelagic existence of microflagellates that graze attached bacteria may be strongly linked to the distribution of suspended particles and their associated bacteria. In addition, the removal of attached bacteria by microflagellates can significantly affect the density of bacteria attached to particles in the plankton. This activity may have important implications for the controversy concerning the relative importance of attached and free-living bacteria in the plankton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02024998
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  • 2
    Electronic Resource
    Electronic Resource
    Factors responsible for the differences in cultural estimates and direct microscopical counts of populations of bacterivorous nanoflagellates (1989)
    Springer
    Microbial ecology 18 (1989), S. 89-104 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Bacterivorous nanoflagellates (microflagellates) have been routinely enumerated in marine and freshwater samples using either a Most Probable Number (MPN) culture method or by a direct microscopical counting method (DC). These two techniques typically yield highly disparate estimates of the density of nanoflagellates in natural samples. We compared these methods with seawater and marine snow (macroscopic detrital aggregate) samples collected from surface waters throughout the North Atlantic and in freshwater samples collected at three stations in Lake Ontario. Densities of nanoflagellates determined by the two methods differed by as much as four orders of magnitude; the MPN estimate rarely exceeded 10% of the microscopical count, and averaged ≈ 1% of this count. The MPN estimate constituted a higher percentage of the DC value in environments with high concentrations of nanoflagellates relative to environments with low concentrations of nanoflagellates. The ratio of the culture count to the microscopical count (MPN∶DC) increased along an environmental gradient from oligotrophy to eutrophy, and was positively correlated with the density of bacteria in the samples. In laboratory experiments with two species of bacterivorous nanoflagellates, the MPN count constituted a much greater percentage of the DC count during the exponential growth phase of the nanoflagellate than during the stationary growth phase. Differences in the estimates of nanoflagellate density obtained with these two techniques probably can be explained by the trophic mode of these protozoa, their growth stage, and the amenability of these species to laboratory culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02030118
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  • 3
    Electronic Resource
    Electronic Resource
    Light-dependent phagotrophy in the freshwater mixotrophic chrysophyte Dinobryon cylindricum (1993)
    Springer
    Microbial ecology 25 (1993), S. 93-111 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00182132
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  • 4
    Electronic Resource
    Electronic Resource
    Relationship between phototrophy and phagotrophy in the mixotrophic chrysophytePoterioochromonas malhamensis (1990)
    Springer
    Microbial ecology 19 (1990), S. 97-109 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02015056
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  • 5
    Electronic Resource
    Electronic Resource
    Mixotrophic algae in three ice-covered lakes of the Pocono Mountains, U.S.A. (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 28 (1992), S. 0 
    Details
    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
    URL: http://dx.doi.org/10.1111/j.1365-2427.1992.tb00583.x
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  • 6
    Electronic Resource
    Electronic Resource
    Antarctic amoebae adventures (2005)
    Oxford, UK : Blackwell Science Inc
    The @journal of eukaryotic microbiology 52 (2005), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Ice, slush, sediment and water samples were collected from the Ross Sea, Antarctica and enriched with a variety of inorganic and organic nutrients. All cultures were maintained at an ambient temperature of 1°C, and amoebae were observed to occur in the slush, sediment and water enrichments. Amoebae were isolated into clonal or monocultures, and their characterization was accomplished using a combination of molecular and morphological methods. Full-length 18S ribosomal DNA sequence data indicated that seven of the isolates represented four different amoebae of the Vexilliferidae and Vannellidae families. Acquisition of 18S ribosomal sequences from the parasomes of two amoebae further confirmed their identification as Neoparamoeba species. Light microscopy, fluorescence microscopy and TEM observations were accomplished and further support the molecular data. To determine whether these amoebae represented psychrophilic strains, their temperature tolerances were tested. Cultures were inoculated at 1°C and the temperature was raised 1°C/day (to a total of 5°), and then held at that temperature for 6 days. This pattern was repeated in 5°-increments, up to 20°C. The cultures were observed frequently for death and possible cyst formation. Three (2 types of Vannellids) out of seven amoeba cultures survived up to 20°C. Whereas, the two different Vexilliferids died at a range of temperatures between 10°C and 20°C. These data indicate that amoebae found in the Antarctic are varied in their physiological adaptation for growth at cold temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2005.05202003_1_62.x
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  • 7
    Electronic Resource
    Electronic Resource
    The Growing Contributions of Molecular Biology and Immunology to Protistan Ecology: Molecular Signatures as Ecological Tools (2004)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 51 (2004), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: . Modern genetic and immunological techniques have become important tools for assessing protistan species diversity for both the identification and quantification of specific taxa in natural microbial communities. Although these methods are still gaining use among ecologists, the new approaches have already had a significant impact on our understanding of protistan diversity and biogeography. For example, genetic studies of environmental samples have uncovered many protistan phylotypes that do not match the DNA sequences of any cultured organisms, and whose morphological identities are unknown at the present time. Additionally, rapid and sensitive methods for detecting and enumerating taxa of special importance (e.g. bloom-forming algae, parasitic protists) have enabled much more detailed distributional and experimental studies than have been possible using traditional methods. Nevertheless, while the application of molecular approaches has advanced some aspects of aquatic protistan ecology, significant issues still thwart the widespread adoption of these approaches. These issues include the highly technical nature of some of the molecular methods, the reconciliation of morphology-based and sequence-based species identifications, and the species concept itself.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2004.tb00159.x
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  • 8
    Electronic Resource
    Electronic Resource
    Symposium Introductory Remarks: “Protistan Molecular Ecology and Systematics” (1996)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 43 (1996), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1996.tb04485.x
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  • 9
    Electronic Resource
    Electronic Resource
    Protistan diversity in the Ross Sea, Antarctica: linking genotype, morphology and physiology (2005)
    Oxford, UK : Blackwell Science Inc
    The @journal of eukaryotic microbiology 52 (2005), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Traditional microscope-based studies of protistan assemblages in the Ross Sea, Antarctica have contributed significantly to our understanding of the microbial biogeography and food web structure in this extreme cold-water environment. However, these investigations have neither been able to characterize the genetic diversity of the communities, nor have they necessarily determined the abundances or trophic contribution of the dominant organisms. Resolution of the latter issue is hindered by the fact that physiological studies are often conducted on opportunistic species that respond to enrichment culture rather than species truly representative of intact communities. Therefore, we sought to determine the genetic diversity of microbial eukaryotes in ice, water and slush samples from the Ross Sea, and establish both morphologic and physiologic links between enrichment cultures and the genetic data. Denaturing gradient gel electrophoresis and ribosomal clone library analyses indicate that the protistan communities are very diverse, but those present in similar habitats are more alike than those in different habitats at the same site. We have been able to identify several protists from our enrichment cultures as being genetically represented in the original samples. General studies of their physiology have been initiated and methods for determining their abundances are being developed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2005.05202003_1_28.x
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  • 10
    Electronic Resource
    Electronic Resource
    Identification of Heterotrophic Nanoflagellates by Restriction Fragment Length Polymorphism Analysis of Small Subunit Ribosomal DNA (2001)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 48 (2001), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: . Thirty clones derived from twenty isolates of heterotrophic nanoflagellates originating from a variety of marine and freshwater environments were examined by restriction fragment length polymorphism analysis of small subunit ribosomal RNA genes amplified by the polymerase chain reaction (riboprinting). The data were compared with light and electron microscopical identification of the isolates. On morphological criteria, sixteen of the thirty clones belonged to the genus Paraphysomonas De Saedeleer, seven to the genus Spumella Cienkowski, four to the genus Pteridomonas Penard and three to the genus Cafeteria Fenchel and Patterson. Among these taxa, eleven ribotypes were detected by analysis with the restriction enzymes Hinf I, Hae III, Sau 3A I, and Msp I. Differentiation of nanoflagellate taxa by the riboprinting method supported taxonomic classification based on morphology at the generic and species level. The utility of the method for discriminating the ‘naked’ flagellates and for confirming the identity of polymorphic forms among species of Paraphysomonas is demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2001.tb00312.x
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