The Supramolecular Structure of Photosystem II — Phycobilisome-Complexes of Porphyridium cruentum

The structure and arrangement of phycobilisomes of the unicellular red alga Porphyridium cruentum is compared with the organization of the thylakoid freeze-fracture particles in order to determine the relationship between phycobilisomes and photosystem II. The hemi-ellipsoidal phycobilisomes, 20 nm thick, are predominantly organized into rows; their centre to centre periodicity is 30–40 nm, so that they are well separated by a gap of 10–20 nm. The phycobilisomes are cleaved by a central faint furrow, parallel to the long axis from top to base. The organization of the exoplasmic particles in rows is similar to the arrangement of the phycobilisomes so that a structural relationship between both systems, previously demonstrated in cyanobacteria, is evident. Within the rows, the 10 nm EF-particles are grouped in tetrameric complexes separated by distances similar to those observed for phycobilisomes. We propose that the tetrameric EF-particle complexes correspond to tetrameric photosystem II complexes which bind one hemi-ellipsoidal phycobilisome on the stroma exposed surface of the thylakoid. A hypothetical model of this photosystem II-phycobilisome complex is presented.     

Comparative properties of ferredoxins from a marine and freshwater species of Porphyridium

Ferredoxins were isolated from the freshwater red alga Porphyridium aerugineut, and from Porphyridium cruentum, a related marine species. A sin     

Biliprotein assembly in the disc-shaped phycobilisomes of Rhodella violacea electron microscopical and biochemical analyses of C-phycocyanin and allophycocyanin aggregates

C-phycocyanin and allophycocyanin from the red alga Rhodella violacea were investigated by electron microscopy and biochemical methods using samples taken from the same fractions.The molecular weights of the native biliprotein aggregates C-phycocyanin and allophycocyanin are about 139,000 (140,000) and 130,000 (145,000) as revealed by calibrated gel chromatography, gradient gel electrophoresis and morphological measurements on the basis of an average protein packing density. These molecular weights are direct evidence for a trimeric aggregation form ()₃ of these biliproteins. Independently, their monomers were determined to be about 34,400 (C-phycocyanin) and 33,900 (allophycocyanin).C-phycocyanin and allophycocyanin are ringshaped, six-membered, biliprotein aggregates with dimensions of about 10.2×3.0 nm and 10.0×3.0 nm, respectively. The aggregates are made up of six subunits, 3 and 3, which are assumed to be associated in alternating positions. They are arranged in regular hexagons in C₆ symmetry. Hexameric aggregates ()₆, so far only isolated for C-phycocyanin, originate by face to face association of two trimeric aggregates.     

Halogenated monoterpenes of the red alga Microcladia

The red marine algae Microcladia borealis, M. californica and M. coulteri produce several unusual halogenated monoterpenes including violacene, plocamene-B, plocamene-C, and plocamane-D. The isolation of these terpenes along with a study of their variation in each Microcladia at different locations are described.     

Cryopreservation of economically valuable marine micro-algae in the classes Bacillariophyceae, Chlorophyceae, Cyanophyceae, Dinophyceae, Haptophyceae, Prasinophyceae, and Rhodophyceae

The ability to routinely cryopreserve micro-algal species reduces costs associated with maintaining large culture collections and reduces the risks of losing particular strains or species through contamination and genetic drift. Cryopreservation is also a useful adjunct in aquaculture hatcheries for strains of micro-algae where the nutritional status may change as a result of continuous sub-culture. In this study, cryopreservation of isolates from seven micro-algal classes was investigated. Successful candidates included the marine dinoflagellates Amphidinium carterae, Amphidinium trulla, and Gymnodinium simplex, and the haptophytes Chrysochromulina simplex, Prymnesium parvum, Prymnesium parvum f. patelliferum, Isochrysis galbana, and Pavlova lutheri. Also successfully cryopreserved were the planktonic diatoms Chaetoceros calcitrans, Chaetoceros muelleri, Chaetoceros sp., and the benthic Nitzschia ovalis, the chlorophyte Chlamydomonas coccoides, the rhodophyte Porphyridium purpureum, the prasinophytes Tetraselmis chuii, and Tetraselmis suecica, and the cyanophytes Raphidiopsis sp., and Aphanizomenon flos-aquae. All species were successfully cryopreserved using 15% Me2SO.     

The influence of ionic detergents on the phospholipid fatty acid compositions of Porphyridium purpureum

The phospholipid fatty acid composition of Porphyridium purpureum on a solid medium was studied in the presence of sodium dodecyl sulphate (SDS) and cetyl trimethylammonium bromide (CTAB). The most common fatty acids in phosphatidyl choline (PC) and phosphatidyl ethanolamine (PE) were palmitic (16:0), stearic (18: 0), linoleic (18:2ω 6), arachidonic (20:4ω 6) and eicosapentaenoic (20:5ω 3) acids, 20:4ω 6 being very abundant. In phosphatidyl glycerol (PG) the most common acids were 16:0, trans-hexadecenoic acid (tr 16:1ω 13), oleic acid (18:1) and 20:4ω 6. Both detergents increased the saturation grade of PC and PE by decreasing the relative amount of the polyunsaturated acids, especially 20:4ω 6. A corresponding increase in the amounts of saturated acids was observed in PC and PE. The changes in PG fatty acid composition were not very significant: a slight increase was observed in the amounts of 16:0 and tr 16:1ω 13 , with a corresponding decrease in the amounts of 20:4ω 6 and 20:5ω 3. Both detergents decreased the PC/PE and the (PC + PE)/PG ratios very markedly, most probably as a result of increases in the amounts of PE and PG. In the presence of CTAB the cells seemed to contain much more phospholipids than in the presence of SDS, perhaps as a result of the mucilage-precipitating effect of CTAB. The significance of the findings is discussed.     

Configurational studies on red algae carotenoids

The configurations of (6′R)-β,ε-carotene, (3′R,6′R)-β,ε-caroten-3′-ol (α-cryptoxanthin), (3R,3′R,6′R)-β,ε-carotene-3,3′-diol (lutein), (3R)-β,β-caroten-3-ol (β-cryptoxanthin), (3R,3′R)-β,β-carotene-3,3′-diol (zeaxanthin) and all-trans (3S,5R,6S,3′R)-5,6-epoxy-5,6-dihydro-β,β-carotene-3,3′-diol (antheraxanthin) were established by CD and ¹H NMR studies. The red algal carotenoids consequently possessed chiralities at each chiral center (C-3, C-5, C-6, C-3′, C-6′), corresponding to the chiralities established for the same carotenoids in higher plants. Two post mortem artifacts from Erythrotrichia carnea were assigned the chiral structures (3S,5R,8R,3′R)-5,8-epoxy-5,8-dihydro-β,β-carotene-3,3′-diol [(8R)-mutatoxanthin] and (3S,5R,8S,3′R)-5,8-epoxy-5,8-dihydro-β,β-carotene-3,3′-diol [(8S)-mutatoxanthin]. This is the first well documented report of a naturally occurring β,ε-caroten-3′-ol (¹H NMR, CD, chemical derivatization).     

The glycolipid fatty acids of Porphyridium purpureum cultured in the presence of detergents

The glycolipid fatty acid composition of Porphyridium purpureum on a solid medium was studied in the presence of Triton X-100 (TX), sodium desocycholate (SDC), sodium dodecyl sulphate (SDS) and cetyl trimethylammonium bromide (CTAB). TLC and GC/MS were used in determining the relative fatty acid compositions of mono-and digalactosyl diglycerides (MGDG and DGDG) and in assessing the MGDG/DGDG ratio. The most common fatty acids were palmitic (16:0), stearic (18:0), linoleic (18:2 ω6), arachidonic (20:4 ω6) and eicosapentaenoic (20:5 ω3) acids, the long-chain polyunsaturated acids being more abundant in DGDG; α-linolenic acid (18:3 ω3) was absent. TX and SDC in particular caused an increase in the saturation grade of both MGDG and DGDG fatty acids at very low concentrations (5–15 ppm). With a detergent concentration of 20 ppm a reversion of this tendency was sometimes found, and the fatty acid composition approached the controls again. The effects of SDS and CTAB were not as prominent. All the detergents studied increased the normal MGDG/DGDG ratio (0.3) to a maximum of ～ 1. The effect of increasing detergent concentration is not linear. The results suggest that in some cases very low detergent concentrations can be more effective than higher ones, a fact which may be important in algae growing in polluted waters.     

Inorganic ion compositions in the Ulvophyceae and the Rhodophyceae, with special reference to sulfuric acid ion accumulations

Cellular pH estimated from cell extract pH, and the ion compositions of major inorganic ions (Na⁺, NH₄⁺, K⁺, Mg²⁺, Ca²⁺, Cl^?, Br^?, NO₃^?, S0₄²‐) were studied by ion chromatography in 15 species of 4 orders (Cladophorales, Codiales, Siphonocladales and Ulvales) of Ulvophyceae and 49 species of 8 orders (Bangiales, Ceramiales, Corallinales, Cryptonemiales, Gelidiales, Gigartinales, Nemaliales and Rhodymeniales) of Rhodophyceae. Among the Rhodophyceae, relatively low intracellular pH (approximately 2.0 within cells) and high concentration of S0₄^2‐ was demonstrated in Plocamium telfairiae(Harvey) Harvey. Furthermore, five species of Hypnea Lamouroux were shown to contain high concentrations of S0₄^2‐ balanced by relatively high concentrations of Na⁺. Among the Ulvophyceae, Codium cylindricum Holmes and Ulva pertusa Kjellman contained high concentrations of S0₄^2‐ balanced by relatively high concentrations of Mg²⁺.     

Carbon exchange between Polysiphonia lanosa (Rhodophyceae) and its brown algal host

Polysiphonia lanosa and its preferred Ascophyllum nodosum host exchange 14C-labeled photoassimilates. Exchange was demonstrated by injecting 14C-bicarbonate into air bladders on 15-30 cm cultured sections of field-collected host blades. Each section bore rhizoidally attached Polysiphonia. In a separate set of experiments, Polysiphonia on similar host material was surface treated with 14C-bicarbonate in sealed vessels. Movement of radioactive label was detected by autoradiographic and liquid scintillation techniques. On average, 10.5% of total label moved from host to hemiparasite following the first treatment, and 9.7% moved from hemiparasite to host following the second. Reciprocal exchange of tagged photoassimilates may play an important role in the specificity of the relationship between these two algal species.