Elijah Swift

University of Rhode Island, Kingston, RI, United States

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Publications (24)43.64 Total impact

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    ABSTRACT: We have examined aspects of the bioluminescence of 5 clones of Dissodinium, 1 clone of Pyrocystis acuta, 4 clones of Pyrocystis fusiformis, and 5 clones of Pyrocystis noctiluca. All clones produced the same color bioluminescence with an intensity peak near 474 nm. The in vivo emission spectra of these clones agreed with those previously determined, for 4 other species of marine dinoflagellates. The amount of light emitted by the dinoflagellates in scotophase when mechanically stimulated to exhaustion was determined for most of the clones. The largest species, P. noctiluca and P. fusiformis, emitted 37–89 × 109 photons cell−1 and 23–62 × 109 photons cell−1, respectively, about a thousand, times as much light as Gonyaulax species. Pyrocystis acuta emitted 3–6 × 109 photons cell−1. Three of the 5 clones of Dissodinium were bioluminescent. The range for 3 clones was 5–13 × 109 photons cell−1. All 5 clones of Dissodinium are morphologically distinct. Both the clones of Dissodinium and Pyrocystis produced much higher numbers of photons per cell nitrogen (ca. 7–50 times) than Gonyaulax polyedra or Pyrodinium bahamense. The data suggested that enzyme turnover occurred in the reactions producing light during mechanical stimulation of Dissodinium and Pyrocystis species.
    Journal of Phycology 06/2008; 9(4):420 - 426. · 2.24 Impact Factor
  • Elijah Swift, Valerie Meunier
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    ABSTRACT: Preadapted cultures were grown in a 12:12 LD cycle at a series of light intensities under cool-white, fluorescent lamps. Pyrocystis fusiformis Murray maintained high division rates at low light intensities at the expense of cell size. In contrast, Dissodinium lunula (Schuett) Taylor had relatively lower division rates at low light intensities with little concomitant decrease in size. The response of P. noctiluca Murray was intermediate between these two species. For all three, cell numbers did not increase above an intensity of 5–10 μEin·m−2·sec−1 and division rate was saturated at ca. 30, 60, and 60μEin·m−2·sec−1 for P. fusiformis, P. noctiluca, and D. lunula, respectively. The capacity for stimulable bioluminescence was saturated at light intensities of 0.15 μEin·m−2·day in short-term (2-day) experiments. In cultures of P. fusiformis and P. noctiluca, maintained for at least one month at lower intensities than needed to saturate division rate, a decrease in the capacity for stimulable bioluminescence was accompanied by a reduction in cell size. Our results suggest that cell size and bioluminescent capacity may prove to be a potentially useful indication of the history of exposure of natural populations of Pyrocystis spp. to ambient intensities.
    Journal of Phycology 06/2008; 12(1):14 - 22. · 2.24 Impact Factor
  • Elijah Swift, Edward G. Durbin
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    ABSTRACT: Three cultured species of Pyrocystis (Dinoccoccales) reproduced asexually by forming 2 (or 1) aplanospores or zoospores inside the parent cell wall. In all 3 species these small reproductive cells, although they may not resemble the parent cells, swell up rapidly (∼ 10 min) to the approximate size and shape of the parent cell. These swollen cells become new vegetative cells. The above asexual process is the only way by which cells numbers increase in our cultures. Pyrocystis lunula was propagated at the lunula stage of the life cycle. The nonmotile crescent-shaped cells produced reproductive cells that were Gymnodinium-shaped and had, in some cases, a trailing flagellum. With P. fusiformis and P. noctiluca, the reproductive cells were not flagellated. With P. fusiformis, these bodies had a pronounced equatorial constriction like a girdle, while in P. noctiluca the “girdle” was an inconspicuous feature if present. With P. noctiluca and P. fusiformis on a 12:12 ld cycle, reproductive cells were formed early in the dark period and they swelled up at the beginning of the light period. Reproduction of P. lunula was not well phased in our experiments, with reproductive cells developing at the end of the light period and the end of the dark period.
    Journal of Phycology 06/2008; 7(2):89 - 96. · 2.24 Impact Factor
  • Ronald L. Hersey, Elijah Swift
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    ABSTRACT: The activity of extracted NADH-NO3− reductase was measured in the marine dinoflagellates Amphidinium carteri Hulburt and Cachonina niei Loeblich. Its activity showed a diel periodicity and was ca. twice as great at midday as at midnight. The enzyme activity was unstable, with an in vitro half-life of 2–3 h. Values of enzyme activity were low or undetectable during lag phase but paralleled the instantaneous growth rate value during log phase. Nitrate reductase activity was not found in the stationary phase of growth, but additions of NO3− resulted in enzyme activity after 24h. When A. carteri was exposed to a series of light intensities for several weeks, the division rate and enzyme activity increased with increasing light intensity up to saturating intensities. In 6 h exposures, enzyme activity decreased with decreasing light intensities below light intensities saturating division rate. Additions of NH4+ (0.5–50 μm) to A. carteri cultures decreased the amount of extractable enzyme. The in vitro activity was not inhibited by similar NH+4 concentrations.
    Journal of Phycology 06/2008; 12(1):36 - 44. · 2.24 Impact Factor
  • Elijah Swift, Charles C. Remsen
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    ABSTRACT: The cell of Pyrocystis spp. is covered by an outer layer of material resistant to strong acids and bases. Internal to this layer much of the cell wall is composed of cellulose fibrils. The presence of cellulose fibrils was established by staining raw and ultra-violet–peroxide-cleaned cell walls and by combining X-ray diffraction spectroscopy with electron microscope observation. Carbon replicas of freeze-etched preparations and thin sections of P. lunula walls show outer layers, inside them ca. 24 layers of crossed parallel cellulose fibrils (4–5 nm thick, ca. 12 nm wide), then a region of smaller (ca. 6–12 nm diameter) fibrils in a disperse texture, and then the plasma membrane. Cellulose fibrils in the parallel texture are constructed of 3–5 elementary fibrils ca. 3 nm in diameter. Walls of P. fusiformis and P. pseudonctiluca also have cellulose fibrils in a crossed parallel texture similar to those of P. lunula.The Gymnodinium-type swarmer from lunate P. lunula appears to have a cell wall ultrastructure typical of other “naked” dinoflagellates.
    Journal of Phycology 06/2008; 6(1):79 - 86. · 2.24 Impact Factor
  • Elijah Swift
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    ABSTRACT: Living cells of the diatom Ethmodiscus rex (Rat-Iray) Wiseman & Hendey 1953 were found in the plankton of the southern Sargasso Sea. Apparently, this is the first report, of E rex from the plankton of the Atlantic Ocean. Scanning electron microscopy of peroxide-cleaned frustules revealed, some new morphological features for this species. When viewed, from inside the frustule, the puncta appear as rimmed pits. From outside the frustule, they appear to he shallow depressions with a small opening at the bottom. The so-called mucous tubules in the center of the valve were seen from the out side to be elongate slits and from the inside as obliquely directed flattened cylinders which cap the tubes.
    Journal of Phycology 06/2008; 9(4):456 - 460. · 2.24 Impact Factor
  • Elijah Swift, W. Rowland Taylor
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    ABSTRACT: The lunate cysts of Pyrocystis lunula have a bioluminescent emission spectrum with a peak intensity of 477.5 ± 1 mμ. The light originates from the protoplasm in the center of the cysts. Six to eight hr after the cysts were placed in the dark, they produced 300 to 800 times more luminescence than controls maintained under constant, illumination. Plastids contract distally when the cysts are placed in the dark. If kept in the dark, the plastids contract distally and expand with a circadian rhythm persisting several days. At intensities of 2200 μm cm-’or less, the plastids are expanded. The plastids are contracted into the central area of the cysts at light intensities of 4000 μw cm-2 and above. The Gymnodinium stage of the life cycle is not bioluminescent.
    Journal of Phycology 04/2007; 3(2):77 - 81. · 2.24 Impact Factor
  • Elijah Swift, W. Rowland Taylor
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    ABSTRACT: The division rate of Cricosphaera elongata was measured as a function of pH in a medium buffered with the CO2-bicarbonate-carbonate system. The optimum pH for cell division of the coccolithophorid was 7.8. A change of the partial pressure of CO2 in the medium from 0.03 to 5% did not affect the division rate. Between pH 6.4 and 7.8 changes in the bicarbonate concentration from 0.1 to 6.0 mm and carbonate concentration from 0.007 to 0.1 mm did not affect the rate of division. At loiv experimental pH, C. elongata was nonmotile and grew in clumps; at higher pH values, it was motile and solitary. Coccoliths were not found covering C. elongata if calcite was soluble in the medium.
    Journal of Phycology 04/2007; 2(3):121 - 125. · 2.24 Impact Factor
  • Richard B. Rivkin, Elijah Swift
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    ABSTRACT: Phosphate uptake by P-replete and P-depleted Pyrocystis noctiluca (Murray) Schütt grown at different ambient N:P ratios was multiphasic between 0.1 and 100 μM PO43-. Within each of the kinetic phases, the saturated uptake rate (Vmax), but not the half saturation constant (Km) was affected by the cellular-P status and light. Uptake rates in the dark were ca. 50% of that in the light and respiratory activity accounted for the observed basal uptake. The combination of multiphasic uptake, and the uncoupling of short term transient uptake from growth resulting in maximum specific uptake rates of 50 h−1 may help explain the abundance of P. noctiluca in oligotrophic regions.
    Journal of Phycology 11/2004; 18(1):113 - 120. · 2.24 Impact Factor
  • James M. Sullivan, Elijah Swift
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    ABSTRACT: Ceratium fusus (Ehrenb.) Dujardin was exposed to light of different wavelengths and photon flux densities (PFDs) to examine their effects on mechanically stimulable bioluminescence (MSL). Photoinhibition of MSL was proportional to the logarithm of PFD. Exposure to I μmol photons·m−2s−1 of broadband blue light (ca. 400–500 nm) produced near-complete photoinhibition (≥90% reduction in MSL) with a threshold at ca. 0.01 μmol photons·m−2·s−1. The threshold of photoinhibition was ca. an order of magnitude greater for both broadband green (ca. 500–580 nm) and red light (ca. 660–700 nm). Exposure to narrow spectral bands (ca. 10 nm half bandwidth) from 400 and 700 nm at a PFD of 0.1 μmol photons·m−2·s−1 produced a maximal response of photoinhibition in the blue wavelengths (peak ca. 490 nm). A photoinhibition response (≥ 10%) in the green (ca. 500–540 nm) and red wavelengths (ca. 680 nm) occurred only at higher PFDs (1 and 10 μmol photons·m−2·s−1). The spectral response is similar to that reported for Gonyaulax polyedra Stein and Pyrocystis lunula Schütt and unlike that of Alexandrium tamarense (Lebour) Balech et Tangen. The dinoflagellate's own bioluminescence is two orders of magnitude too low to result in self-photoinhibition. The quantitative relationships developed in the laboratory predict photoinhibition of bioluminescence in populations of C. fusus in the North Atlantic Ocean.
    Journal of Phycology 10/2004; 30(4):627 - 633. · 2.24 Impact Factor
  • James M. Sullivan, Elijah Swift
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    ABSTRACT: Field observations and results from previous laboratory studies on the effects of turbulence on dinoflagellates have led to a paradigm in phytoplankton ecology that dinoflagellate growth is negatively affected by turbulence. To test the paradigm, 10 species of autotrophic dinoflagellates were exposed to quantified three-dimensional turbulence generated by vertically oscillating cylindrical rods in 20-L rectangular culture tanks. Turbulence was quantified in the tanks (as the turbulent energy dissipation rate, ε) using an acoustic Doppler velocimeter. Dinoflagellates were exposed to two turbulence treatments: high turbulence (ε∼ 10−4 m2·s−3), low turbulence (ε∼ 10−8 m2·s−3), and an unstirred control. In accord with the paradigm, Ceratium fusus (Ehrenberg) Dujardin had lower net growth rates in high turbulence, whereas Pyrocystis noctiluca Murray ex Haeckel and Ceratium tripos (O. F. Müller) Nitzsch did not increase their numbers in high turbulence. However, Alexandrium tamarense (Lebour) Balech, Pyrocystis fusiformis Wyville-Thomson ex Murray, Alexandrium catenella (Whedon and Kofoid) Balech, and a Gyrodinium sp. Kofoid and Swezy were apparently unaffected by turbulence and had the same net growth rates across all turbulence treatments. Contradicting the paradigm, Lingulodinium polyedrum (Stein) Dodge (= Gonyaulax polyedra), Gymnodinium catenatum Graham, and Alexandrium fundyense Balech had increased net growth rates in high turbulence treatments. Cross-sectional area (CSA) varied little across turbulence treatments for 8 of 10 dinoflagellate species tested, CSA in C. fusus increased when net growth rate decreased in high turbulence, and, conversely, CSA decreased in L. polyedrum when net growth rate increased in high turbulence.
    Journal of Phycology 02/2003; 39(1):83 - 94. · 2.24 Impact Factor
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    ABSTRACT: The effects of small-scale turbulence on two species of dinoflagellates were examined in cultures where the turbulent forces came randomly from all directions and were intermittent both spatially and temporally; much like small-scale turbulence in the ocean. With Lingulodinium polyedrum (Stein) Dodge (syn. Gonyaulax polyedra), division rate increased linearly (from ∼0.35 to 0.5 per day) and the mean cross-sectional area (CSA) decreased linearly (from ∼1100 to 750 μm2) as a function of the logarithmic increase in turbulence energy dissipation rate (ε). These effects were noted when ε values increased between ∼10−8 and 10−4 m2 s−3. However, when ε increased to ∼10−3 m2 s−3, division rate sharply decreased and mean CSA increased. Over the same range of ε, Alexandrium catenella (Wheedon and Kofoid) Balech had its division rate decrease linearly (from ∼0.6 to 0.45 per day) and its CSA increase linearly (from ∼560 to 650 μm2) as a function of the logarithmic increase in ε. Even at the highest ε examined (∼10−3 m2 s−3), which may be unrealistically high for their ambits, both L. polyedra and A. catenella still had fairly high division rates, ∼0.2 and 0.45 per day, respectively. Turbulence strongly affected chain formation in A. catenella. In non-turbulent cultures, the mode was single cells (80–90% of the population), but at ε of ∼10−5 to 10−4 m2 s−3, the mode was 8 cells per chain. At the highest ε (∼10−3 m2 s−3), the mode decreased to 4 cells per chain. The vertical distributions of A. catenella populations in relation to hydrographic flow fields were studied in the summers of 1997 and 1998 in East Sound, Washington, USA (latitude 48°39′N, 122°53′W). In both summers, high concentrations of A. catenella were found as a subsurface bloom in a narrow depth interval (∼2 m), where both current shear and turbulence intensity were at a minimum. Other researchers have shown that A. catenella orients its swimming in shear flows, and that swimming speed increases with chain length. These responses, when combined with our observations, support a hypothesis that A. catenella actively concentrates at depths with low turbulence and shear.
    Harmful Algae. 01/2003;
  • Evelyn J. Lessard, Elijah Swift
    Journal of Plankton Research - J PLANKTON RES. 01/1986; 8(6):1209-1215.
  • R. B. Rivkin, E. Swift
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    ABSTRACT: The phosphorus metabolism of Pyrocystis noctiluca Murray (Schuett) 1886 has characteristics which may enhance its potential for success in orthophosphate impoverished waters. The steady-state phosphate uptake rates were equal in the light and dark, and were directly proportional to both the phosphorus cell quota and the cell division rate. In contrast, nutrient-saturated uptake rates were multiphasic, faster in the light than the dark, 2 to 4 orders of magnitude greater than steady-state rates, and were inversely proportional to both the phosphorus cell quota and the cell division rate. These uptake characteristics suggest that P. noctiluca may take up phosphate coincidently at their typically low ambient concentrations as well as to exploit episodic nutrient events in nature. Cell division rates were a hyperbolic function of the ambient orthophosphate concentration. The shortest doubling time was 8.7 d, the phosphate concentration at half the maximum division rate was 0.15 M and the threshold, concentration for cell division was ca 0.05 M PO 4 3- . Division rates of P. noctiluca in the ocean are much faster than predicted from the measured ambient orthophosphate concentrations. Since this dinoflagellate has high naturally occurring alkaline phosphatase activities, and can utilize organic-P compounds, we suggest that organic-P can be as important as orthophosphate in supporting the observed division rates of P. noctiluca in the sea.
    Marine Biology 07/1985; 88(2):189-198. · 2.39 Impact Factor
  • E. J. Lessard, E. Swift
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    ABSTRACT: A dual-isotope method was developed to measure grazing rates and food preferences of individual species of heterotrophic dinoflagellates from natural populations, collected from the Slope, Gulf Stream, and Sargasso Sea and from a transect from Iceland to New England, in 1983. The isotope method measures the grazing rates of microzooplankton which cannot be separated in natural populations on the basis of size. Tritiated-thymidine and 14C-bicarbonate were used to label natural heterotrophic and autotrophic food, respectively. Nine oceanic dinoflagellate species in the genera Protoperidinium, Podolampas, and Diplopsalis fed on both heterotrophic and autotrophic food particles with clearance rates of 0.4 to 8.0 l cell-1 h-1, based on 3H incorporation, and 0.0 to 28.3 l cell-1 h-1, based on 14C incorporation. Two dinoflagellate species, Protoperidinium ovatum and Podolampas palmipes, fed only on 3H-labelled food particles. Several species of dinoflagellates fed on bacteria (m) which had been prelabelled with 3H-thymidine. The clearance rates of heterotrophic dinoflagellates and ciliates were similar and within the range of tintinnid ciliate clearance rates reported in the literature. As heterotrophic dinoflagellates and ciliates can have comparable abundances in oceanic waters, we conclude that heterotrophic dinoflagellates may have an equally important impact as microheterotrophic grazers of phytoplankton and bacteria in oceanic waters.
    Marine Biology 06/1985; 87(3):289-296. · 2.39 Impact Factor
  • Journal of Plankton Research - J PLANKTON RES. 01/1985; 7(6):831-848.
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    ABSTRACT: Vertical profiles of species-specific carbon uptake rates were determined for Pyrocystis sp. collected from net tows in the Gulf Stream and Sargasso Sea and incubated for 1 to 2 h in situ. Rates of cell division (estimated from the frequency of dividing cells) and cellular Chl a, carbon and nitrogen contents were also measured. The in situ rates of cell division (0.085 to 0.116 d−1), the maximum rates of photosynthesis (1.7 to 1.9 ng carbon cell−1 h−1), and the molar C: N ratio (10) of isolated cells were similar to those observed in exponentially growing cultures data suggest that Pyrocystis, although contributing only ca. 1% to community primary production, was neither nutrient nor light limited in situ. Cell division rates were relatively constant throughout the euphotic zone. In contrast, rates of photosynthesis and carbon-specific growth declined by an order of magnitude between the mixed layer and the bottom of the euphotic zone. When integrated over the euphotic zone, rates of carbon-specific growth and cell division were similar, 0.122 and 0.116 d−1, respectively, at the most nutrient-poor station, and 0.098 and 0.085 d−1, respectively, at the most nutrient-poor station. We suggest that during its migration between the mixed layer and the base of the euphotic zone, Pyrocystis sp. assimilates carbon in excess of its immediate metabolic requirements near the surface and catabolizes the stored carbon at greater depths, thus maintaining a relatively constant division rate at all depths within the euphotic zone.
    Deep Sea Research Part A. Oceanographic Research Papers. 01/1984; 31(4):353-367.
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    ABSTRACT: In the southern Sargasso Sea, we used a pump-through bathyphotometer (15 l min−1) to investigate stimulatable bioluminescence of the epipelagic zone. Twenty-four percent (range 17-38%) in vertical profiles and 17% (range 6-24%) in discrete depth samples of the flashes were too bright to be produced by dinoflagellates. Of the total bioluminescence detected, these bright flashes contained in vertical profiles 60% (range 53-67%) and in discrete samples 56% (range 29-70%). There were enough bioluminescent dinoflagellates in the bathyphotometer effluent to account for less than 34% of the total flashes detected and less than 45% of the flashes small enough to be produced by dinoflagellates. This information, combined with plankton data, suggests that bioluminescent species of copepods, larvaceans and ostracods produce more stimulatable bioluminescence in the Sargasso Sea than dinoflagellates.
    Bulletin of Marine Science -Miami- 09/1983; 33(4):855-863. · 1.30 Impact Factor
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    ABSTRACT: Species-specific rates of photosynthetic carbon uptake (P), chlorophyll a content and P versus irradiance (P-I), have been measured for cells of Pyrocystis noctiluca and P. fusiformis isolated from natural populations collected in the euphotic zone within and below the surface mixed layer in the Sargasso Sea. These same measurements and the assay for ribulose bis-phosphate carboxylase (RuBP-Case), have been made for cultures of P. noctiluca in a 12 h L: 12 h D photoperiod at 9 different constant or at changing light intensities. In nature chl a cell-1 was constant throughout the euphotic zone. The photosynthetic capacity (Pmax), of cells captured below the surface mixed layer was lower by a factor of 10 compared with cells collected from the surface mixed layer. The Pmax for P. noctiluca collected and incubated within the surface mixed layer was the same as for cell cultures grown under high light, non nutrient-limiting conditions, suggesting that photosynthesis in the natural system was not nutrient limited. In laboratory cultures under constant low light intensities, chl a cell-1 increased by a factor of 5 while both Pmax and RuBPCase activity decreased by a factor of ca 4 compared with high light intensities. In changing light intensities both Pmax and RuBPCase activities were decreased by factors of 4 during low light intervals while chl a cell-1 approached a constant intermediate value. The change in chl a cell-1 in response to prolonged exposure to constant low light intensities was first order with a rate constant of 0.33 d-1. For all irradiance conditions in culture, the P-I dependence could be described by the simple Michaelis-Menten formula. The ratio of Pmax to KI, (the light intensity where P=Pmax/2) was a constant with a Coefficient of Variation of 12%: The constancy of this ratio, the parallel changes in RuBPCase activity with Pmax and the constant chl a cell-1 in the Sargasso Sea imply that for P. noctiluca and presumably P. fusiformis in nature, a dark enzymatic step rather than changes in photosynthetic pigment concentrations may regulate the photosynthetic capacity in the changing photic environment.
    Marine Biology 01/1982; 68(2):181-191. · 2.39 Impact Factor
  • R. B. Rivkin, E. Swift
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    ABSTRACT: Phosphate depleted Pyrocystis noctiluca (Murray) Schuett 1895 has at least one phosphomonoesterase (EC 3:1:3:1) which is triphasic between 0.1 and 222 mol P. The enzyme has a broad temperature range with maximum activity at 50 C and a Q10 of 1.4 to 1.5. A break in the Arrhenius plot at 35 C implies the enzyme is membrane-bound. Cytological staining of whole cells and cell fractionation studies (showing 26 times higher specific activity in the particulate compared with the cytoplasmic fraction) suggest the enzyme is plasmalemma-bound. The enzyme has an absolute metal requirement which would be satisfied by Mg++ but not Mn++, Zn++, Fe++, or Co++ at seawater concentrations. Alkaline phosphatase is a stable enzyme whose activity is not altered by inhibitors of protein synthesis. Orthophosphate inhibition of enzyme activity was largely eliminated in the presence of these inhibitors. Apparently, a protein induced by PO4 3-, rather than PO4 3- itself, inhibits alkaline phosphatase. Cell-free alkaline phosphatase can hydrolyze a variety of phosphate esters and linear polymers of inorganic phosphorus as well as disolved organic phosphorus from tropical oceanic waters. These same hydrolysable organic and inorganic phosphorus compounds support the axenic culture growth of P. noctiluca, suggesting that naturally occurring hydrolysable organic phosphorus compounds may also support the growth of this alga.
    Marine Biology 11/1980; 61(1):1-8. · 2.39 Impact Factor

Publication Stats

524 Citations
43.64 Total Impact Points

Institutions

  • 1977–2008
    • University of Rhode Island
      • Graduate School of Oceanography
      Kingston, RI, United States
  • 1969–2007
    • Johns Hopkins University
      • Department of Biology
      Baltimore, Maryland, United States