Jack Myers

Growth and photosynthetic characteristics of euglena gracilis

I t would appear desirable in photosynthesis studies to work with an organism which exhibits typical green plant photosynthesis, and also possesses the ability to utilize a variety of organic compounds for growth in the dark. The green flagellate, Euglena gracilis, var. bacillaris was commended to us by Dr. S. H. HUT~ER as such an organism. B~glena gracilis has not been used previously in photosynthesis studies, but extensive data on the nutrition of the organism are available (cf. reviews by Lwo~, 1932, 1943; TRAGE•, 1941; HALL, 194i, 1943; DOYLe, 1943; Jaa~, 1946; PRI~CS~IM, 1948; REI~HARD% 1950; HUTNv.R and PROVASOLI, 1951). However, conflicting reports exist on suitable nitrogen sources (PRI~GSH~r~, 1914; DuSI, 1933), on utilizable carbon sources (MAI~x, 1928; DUST, 1933; J~m~, 1935; PRI~rOSHE~, 1937), and on the nature of growth factor requirements for E. gracilis (P~I~OSHEr~, 1914; HuT~.t~, 1936; [ELLIOTT, 1937; LWOFF and DusI, 1938; HALL and SCHOE~BOR~, 1939; SCHOENBORI% 1942). The data from which the discrepancies concerning Euglena nutrition arise were obtained by techniques which do not permit quantitative estimation of growth characteristics, as summarized by Mol~oD (1942, 1949) and MYERS (1951). A major obstacle to earlier work was the lack of a complete medium, only recently defined when HUT~EI% et al. (1949) showed that a combination of vitamin BI~ and thiamin satisfied the growth factor requirements of the organism. In order to obtain background information for studies on the possibility of CO~ replacement in the metabolism of Euglena to be presented in a succeeding paper, a survey of the salient growth and photosynthetic characteristics of the species was undertaken. The results of this work are reported here and include definition of the requirements for maximal growth of Euglena in the light and in darkness ; determination of utilization of carbon sources; and characterization of photosynthesis in this flagellate.

THE PRODUCTION OF HYDROGEN PEROXIDE BY BLUE‐GREEN ALGAE: A SURVEY1

A survey of 38 axenic isolates of blue‐green algae indicated that over half the isolates produced hydrogen peroxide under defined growth conditions. Three kinetic profiles for the formation of hydrogen peroxide, were observed; these are described. The possible site or sites of hydrogen peroxide formation remain unknown.

ON PIGMENTS, GROWTH, AND PHOTOSYNTHESIS OF PHAEODACTYLUM TRICORNUTUM12

A maximum growth rate with doubling time of 18 hr at 18 C could be maintained. Continuous cultures at about half maximum growth rate provided cells for study of pigments and photosynthesis. The light intensity curve of photosynthesis had no unusual features and showed light‐saturated rates of 30‐35 μl O2/mrn3‐hr at 18 C. Pigment analysis showed chlorophylls a and c (a/c ratio = 4), fucoxanthin, β‐carotene, and diadinoxanthin. Growth under red light (±660 mμ) altered pigments only by decrease in chlorophyll c to about one‐half the content obtained under clear tungsten lamps. The large and anomalous spectral shift in fucoxanthin following organic solvent extraction runs confirmed, but efforts to isolate a native fucoxanthin were unsuccessful. Spectral analysis of acetone extracts and sonicated cell preparations allowed estimate of fractional absorption by each component pigment. The analysis shows that chlorophyll a and fucoxanthin are the principal light absorbing pigments and that absorption by other carotenoids is very small.

Pigment Variations in Anacystis nidulans Induced by Light of Selected Wavelengths

Growth of Anacystis nidulans in wavelengths of light predominantly absorbed by chlorophyll a causes dramatic lowering of the chlorophyll content with only small changes in phycocyanin and carotenoids. Steady‐state growth under red photographic safe lamps produces cells with 1/4 of the chlorophyll content of cells grown under low intensities of white (tungsten) illumination. Pigment analyses permit resolution of in vivo absorption spectra into spectra of the component pigments and also the fractional absorption vs wavelenth. Even in normally pigmented cells phycocyanin is the major collector of light quanta for photosynthesis. The observed pigment control is viewed as a special case of intensity control which has chromatic character by virtue of the presence of two different pigment systems linked to the two light reactions of photosynthesis.

On the Algae: Thoughts about Physiology and Measurements of Efficiency

Though I am honored to be a keynote speaker for this symposium, I am going to duck the responsibility of providing a review. For any thorough review of algal physiology I would not have the temerity and you would not have the patience. Thirty years ago I attempted such a review (1) because one was then needed to define a discipline emerging at the interfaces between microbiology, phycology, and plant physiology. What I can say here most usefully will be directed toward two diverse targets. First, I shall consider the consequences or corollaries of the fact that the algae (at least the microalgae) are microbes. Secondly, I shall consider the ultimate limit of productivity, the maximum efficiency of photosynthetic cell synthesis.

ACTION SPECTRA FOR PHOTOREACTIONS I AND II OF PHOTOSYNTHESIS IN THE BLUE‐GREEN ALGA ANACYSTIS NIDULANS

Abstract— Action spectra for photoreactions I and II of photosynthesis were obtained for Anacystis nidulans and three of its variants which had altered chlorophyll/phycocyanin ratios. The spectra are properly scaled to each other. They provide information on contributions of phycocyanin and chlorophyll to initial absorption and final distribution of excitation energy to reaction centers I and II. In normally pigmented cells the light harvesting pigments for photoreaction I include about 40% of the phycocyanin and 84% of the chlorophyll. Both in normal cells and in cells with altered pigmentation excitation energy from phycocyanin is delivered to photoreaction II via a small number of chlorophylls. In response to alterations in chlorophyll/phycocyanin ratio Action I spectra showed large variations whereas Action II spectra were essentially invariant. The result is taken to mean that alteration in chlorophyll components in Anacystis is attended by a special restriction: there are only small changes in amount of chlorophyll accessible to photoreaction II in the face of large changes in amount committed to photoreaction I.

Water-soluble cytochromes from a blue-green alga. I. Extraction, purification, and spectral properties of cytochromes C (549, 552, and 554, Anacystis nidulans)

Abstract 1. Three water-soluble cytochromes were isolated from the blue-green alga, Anacystis nidulans, by an aqueous extraction of lyophilized cells, the most satisfactory technique of the several tried. Separation of the cytochromes was accomplished on a DEAE-cellullose column and 2 of the cytochromes were highly purified using (NH4)2SO4 fractionation and further column chromatography. 2. The absorption spectra of the most highly purified samples of all 3 cytochromes resemble those of c- type cytochromes with α bands at 549, 552, and 554 mμ. 3. Cytochrome C (549) appears anomalous in its unusually low α peak at 549 mμ, and in being very autoxidizable. 4. The stability of cytochromes C (549 and 554) towards heat, and alkaline and acid pH is described.

CYTOCHROMES OF A BLUE-GREEN ALGA: EXTRACTION OF A C-TYPE WITH A STRONGLY NEGATIVE REDOX POTENTIAL.

Aqueous extraction of lyophilized Anacystis nidulans cells followed by chromatography on diethylaminoethyl cellulose separates three different c-type cytochromes. Of the two present in highest concentration, cytochrome-554 has a + 0.35-volt redox potential and resembles the cytochrome f of other photosynthetic tissues, while cytochrome-549 has a -0.26-volt potential. The possible participatidn of cytochrome-549 in electron transport in photosynthesis in this alga at a more negative oxidation-reduction potential than previously postulated for any cytochrome is inferred from the similarities in its spectra to the light-induced spectral changes in vivo observed by others.

Water-soluble cytochromes from a blue-green alga. II. Physicochemical properties and quantitative relationships of cytochromes C (549, 552, and 554 Anacystis nidulans)

Abstract 1. Properties of the purified cytochrome C (549) include a mesoheme prosthetic group, E 0 ′ of −0.26 V, an acid isoelectric point, and a mol. wt. of about 20 000 with 1 heme per molecule. This cytochrome forms a CO addition compound with a broad peak at 525–530 mμ with a shoulder at about 560 mμ and a sharp peak at 414 mμ but it does not react with KCN or KF. 2. Cytochrome C (554) has a mesoheme prosthetic group, an E 0 ′ of +0.35 V, an acid isoelectric point, and a mol. wt. of about 23 000 per heme and appears to be very similar to photosynthetic cytochrome f isolated from algae. 3. Cytochrome C (552) has been only partially characterized; it also has a mesoheme prosthetic group but has a basic isoelectric point like mammalian cytochromes c . 4. Quantitative analyses show the presence of 1 molecule of cytochrome C (549) per 220 molecules of chlorophyll, 1 molecule of cytochrome C (554) per 1550 molecules of chlorophyll, and 1 molecule of cytochrome C (552) per 21 500 molecules of chlorophyll. Ferredoxin is present in roughly the same molar concentration as is cytochrome C (549).

Hydrogenase and NADP-reduction reactions by a cell-free preparation of Anabaena cylindrica☆

Abstract Subcellular preparations which retained activities of hydrogenase, nicotinamide adenine dinucleotide phosphate (NADP) photoreduction and 2,6-dichlorophenol indophenol (DCPIP) Hill reaction were obtained from Anabaena cylindrica . The hydrogenase bound in the subcellular preparation reduced not only redox dyes in a manner similar to that of the solubilized enzyme obtained from acetone-dried cells but also those coupled with a NADP-reducing system retained in the same preparation. NADP reduction by the hydrogenase reaction was stimulated by addition of ferredoxin, but the NADP photoreduction was not affected by exogenous ferredoxin under the same condition, suggesting some differences in the mechanism of the redox reaction between hydrogenase and ferredoxin from that of the redox reaction between the photochemical system and ferredoxin. Light did not affect NADP reduction via hydrogenase or cause hydrogen evolution.