Nitrate Reduction and Assimilation in Chlorella

Cramer, Marian; Myers, Jack

doi:10.1085/jgp.32.1.93

Cited by 73 publications

(25 citation statements)

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“…The experiments have also allowed measurement of the C02/02 exchange quotient during photosynthetic growth (table III). The data at the low light intensity of 50 fe, which is light-limiting for both growth and photosynthesis, confirm the quotient of 0.68 measured in short-time experiments by the Warburg method (2). The low value of the quotient has been shown to be the result of nitrate reduction.…”

Section: Resultssupporting

confidence: 80%

“…12). It will also be shown elsewhere that nitrate reduction and assimilation, which do not occur in starved cells, must proceed rapidly during growth with increased carbon dioxide production and hence less complete assimilation of glucose (2) The lights were then turned on and the bottle rotated on rollers to give the common roll culture. A high light intensity of about 500 fc was provided by a bank of ten 100-watt lamps set in a water bath which extended about 3 cm.…”

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confidence: 99%

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Carbon and Nitrogen Balance of Chlorella During Growth

Myers

Johnston

1949

Plant Physiol.

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In studies on the algae remarkably little attention has been paid to those details of metabolism which have proved essential in understanding the physiology of other microbial forms. On the carbon and nitrogen balance, for instance, there is little available information. KROGH, LANGE, and SMITH (3) obtained a carbon balance on a culture of Scenedesmus which showed that 95%o of the carbon was retained by the cells under the usual conditions of algal culture. BARKER (1) made tests for but failed to find soluble photosynthate which might be excreted by diatoms. One report of excreted photosynthate is that of UHVITS (11) who found that very small amounts of acetaldehyde of the order of 10-6 to 10-5 moles could be obtained from 200 to 700 ml. of algal suspension (C. pyrenoidosa) when bisulfite had been added to the-medium. It is also common observation that algal cultures develop small amounts of bacterial growth even in completely inorganic media. More complete information on the carbon and nitrogen balance is needed.The metabolism of the algae has been studied almost exclusively by the Warburg technique, which has obvious advantages for such work. There are also certain limitations, in particular a practical restriction to short-time experiments. It has seemed desirable to devise methods for the study of algal metabolism during growth in cultures.Carbon Balance During Growth in the Continuous-Culture Apparatus METHOD The algal continuous-culture apparatus (8) allows maintenance of a constant density of population by a photometric dilution device which adds fresh medium at a rate equivalent to the rate of growth. In addition to other applications already described (4, 5, 6) the apparatus may also be adapted to metabolic studies. If the density of population is held constant, then the net uptake of any component of the nutrient medium by the cells per unit volume must equal the difference in the concentration of that component between the original medium and the final supernatant. This principle has been applied to the study of glucose assimilation in the dark according to the following procedure.The photometric control was operated by an intensity of about four

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Section: Resultssupporting

confidence: 80%

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confidence: 99%

Carbon and Nitrogen Balance of Chlorella During Growth

Myers

Johnston

1949

Plant Physiol.

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“…Actually the procedure makes some degree of overcorrection; it is based on the assumption that the photochemical apparatus is maintained at a constant degree of light Comparison of the present data on specific growth rate with those of photosynthesis studies requires conversion of k to the units measured by manometry. C02/02 has been shown to be 0.7 (4). Unless there are severe changes in nitrogen content the quotient during steady-state growth at high light intensities will be 0.7 also; at any rate it will not be higher than 0.9 as measured in short-time manometric experiments.…”

Section: Discussionmentioning

confidence: 93%

Growth Rate of Chlorella in Flashing Light.

Phillips¹,

Myers²

1954

Plant Physiol.

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145

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SUMMARYAn apparatus is described for precise measurement of growth rate of an alga as a function of intensity and intermittency of illumination. Dilution of a culture is controlled by a photometric device to just such a rate as will maintain constant density of population and balance the growth rate. Maintenance of constant volume by an automatic siphon allows direct application of the differential form of the growth equation in evaluating specific growth rate. The relationships of the new apparatus to other steady-state growth devices are discussed. periment. Cells harvested from a continuous-culture apparatus were centrifuged out and resuspended in a 1/4-strength EDTA Knops solution (13) to a population density which gave a 50 % transmission in an Evelyn colorimeter with 600 m,u glter. In the growth chamber this suspension had a transmission of 81 % as measured with a fully-illuminated photocell placed behind the suspension. Constancy of the photometric control was checked duringf and at the end of each experiment by readings of transmission of the suspension in the Evelyn colorimeter; all such readings fell within the range of 48-52 %. In each experiment the specific growth rate, k, was evaluated in loge units per day as described in the preceding paper. The temperature used throughout was 25°C.INTENSITY MEASUREMENT: Measurements of light intensity at the position of the growth chamber were made with a large surface Moll thermopile with a compensated Aryton shunt and Rubicon Type T galvanometer. It was calibrated without a shielding window against an NBS standard lamp. For subsequent measurements the thermopile was used with a thin glass shielding window. Estimate of the intensity of visible radiation was obtained by use of a Jena RG8 filter which transmits the near infrared and has a sharp cut-off at 7000 A (fig 1). Readings with the thermopile were taken alternately with the system open, with the RG8 filter, and with the system closed by a shutter. (For positions of the shutter and filter in the optical system see figure 2 of the preceding paper.) Total deflection with the system open, minus deflection with the RGS filter was taken as the measure of visible radiation. The procedure is similar to that used by Kok (8)

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“…These effects have been inferred for many years (Trelease and Trelease 1935;Cramer and Myers 1948;Rcdfield ct al. 1963;Richards 1965;Berner et al 1970;Gaines and Pilson 1972) and indeed are implicit in the Redficld-Ketchum-Richards phytoplankton equations.…”

Section: An Understandingmentioning

confidence: 98%

Alkalinity changes generated by phytoplankton growth1

Brewer

Goldman

1976

Limnology & Oceanography

395

210

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Continuous cultures of three marine phytoplankton species, Phaeodactylum tricornutum, Dunaliella tertiolecta, and Monochrysis lutheri, were monitored for changes in alkalinity of the culture medium resulting From NO, and NHa+ uptake. Uptake of NO,-caused an increase in alkalinity, whereas uptake of NH,+ produced a decrease. These results are consistent with the type of schematic equation proposed by Redfield, Ketchum, and Richards for photosynthetic assimilation of inorganic nitrogen, in which NO, uptake is balanced by OH-production and NHa+ uptake leads to H+ generation. These reactions suggest active uptake of nitrogen species by microbes. We have been unable to demonstrate the exact stoichiometry of this relationship, and the role of P uptake in the alkalinity change is unclear. An offset in the data, functionally equivalent to the production of some strong acid, may be due to reactions on the walls of the vessel, active uptake of cations, or extrusion of H' ions by the growing cells.

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Nitrate Reduction and Assimilation in Chlorella

Cited by 73 publications

References 2 publications

Carbon and Nitrogen Balance of Chlorella During Growth

Carbon and Nitrogen Balance of Chlorella During Growth

Growth Rate of Chlorella in Flashing Light.

Alkalinity changes generated by phytoplankton growth1

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