Phormidium Luridum Research Articles

A New Look at a Blue-Green Alga

Electron microscopy has enabled biologists to take a new look at the blue-green algae. Electron micrographs of cell sections are revealing details of cell structure heretofore unseen. New concepts of the membrane systems and associated organelles are beginning to appear. An electron micrograph of cells in a filament of Phormidium luridum was used as the basis of the diagram accompanying this paper. Phormidium luridum is in the same family as the more familiar Oscillatoria. The cells of the species Phormidiurn luridum are of much smaller dimensions than the cells of most blue-green algae. Such very small cells are of special interest to electron microscopists. For example, one of the cells of the species represented in Fig. 1 is scarcely two microns long. Such a cell is so very small that it is possible to draw an outline of it and draw all of its constituent parts, even its finest organelles, on the same scale. This is not possible in the case of the larger microorganisms such as a euglena, ameba, or paramecium. The nucleus of a euglena has an average diameter of about five microns. It is easy to appreciate the relative smallness of these blue-green alga cells in Fig. 1 when one determines that it would take about three of them, end-to-end, to stretch across a euglena nucleus. These very small blue-green cells are described as procaryotic because of their internal organization.

Sterols: isolation from a blue-green alga.

A crystalline mixture of sterols was isolated from the filamentous blue-green alga Phormidium luridum. The mixture consisted of unsaturated 24-ethylcholesterols possessing Delta(7)-, Delta(5,7)-, and Delta(5)-bonds together with their Delta(22)-derivatives and a small amount of cholesterol. The major component was 24-ethyl-Delta(7)-cholestenol. Squalene and phytol were also evident.

Chromophores of allophycocyanin and R-phycocyanin

The biliprotein allophycocyanin was purified from Phormidium luridum, Anabaena variabilis and Plectonema boryanum. R-phycocyanin was purified from Rhodymenia palmata. The chromophores were cleaved from the denatured protein by methanol hydrolysis. They were purified and crystallized as the dimethyl esters. Chromatographic and absorption-spectral (visible-ultraviolet and infrared) comparisons with reference material have established phycocyanobilin as the chromophore of allophycocyanin. Phycocyanobilin and phycoerythrobilin were shown to be the chromophores of R-phycocyanin.

Preparation of Metabolically Active Protoplasts and Particle Preparations from the Blue-Green Alga, Phormidium luridum

A method is described for the preparation of metabolically active protoplasts from the blue-green alga, Phormidium luridum. The isolated protoplasts are stable and are capable of endogenous respiration and photoassimilation of carbon dioxide at rates not appreciably different from the untreated filaments. The protoplasts can be ruptured by dilution of the stabilizing osmoticum and, therefore, they provide a convenient starting point for the production of cell-free preparations within a biochemical reaction mixture of interest.

Photosynthetic Reactions by Lysed Protoplasts and Particle Preparations from the Blue-Green Alga, Phormidium luridum

Reactions of photosynthetic electron transport and photophosphorylation were studied in preparations from the blue-green alga, Phormidium luridum. Osmotic lysis of protoplasts proved to be a superior technique for the production of cell-free preparations with high enzymatic activity. Such lysed protoplasts sustain high rates of photophosphorylation coupled to the photo-reduction of NADP(+) or ferricyanide. P/2e(-) ratios close to unity were routinely observed. The same preparations, and also those prepared by grinding the cells in solutions containing sucrose or ethylene glycol, are active in cyclic photophosphorylation mediated by phenazine methosulfate or dichloro-phenolindophenol. The particles prepared by grinding the cells are, however, inactive in non-cyclic photophosphorylation.Extensive washing of the membranes with solutions containing sucrose removes the majority of the residual soluble fraction of the algal cell which includes cytochromes C(554) and C(549) and phycocyanin. Cyclic photophosphorylation activity is unimpaired by this treatment, but is abolished when the membranes are washed with very dilute buffers. This activity is restored by the addition of a soluble protein which is not a known redox constituent such as cytochrome C(554) or plastocyanin, and may be a coupling factor.Analysis of the well-washed membranes by low temperature (77 degrees K) difference spectrophotometry reveals the presence of cytochrome b(6) and a bound form of cytochrome C(554) in proportions similar to that found in higher plant chloroplasts. The concentration of the membrane-bound cytochrome C(554), relative to cytochrome b(6) is not altered by extensive washing, sonication or treatment with 1% digitonin. This indicates that this cytochrome is an integral component of the cytoplasmic lamellae and we suggest that it is of functional significance. The soluble form of cytochrome C(554), which is present in concentrations about 3-fold higher than the bound form, depending upon growth conditions, is not essential for cyclic photophosphorylation. The concentration of cytochrome b(6): chlorophyll a was found to be 1:500.Under the conditions employed, we were unable to detect a bound form of the low potential cytochrome C(549).

Studies on the identity of ordinary and deuterio-phycocyanins: End-groups, amino acid compositions, minimum molecular weights, peptide maps

New data on the amino acid composition of phycocyanins extracted from Phormidium luridum and Synechococcus lividus grown in H 2O and in 99.7% 2H 2O have been acquired. The presence of tryptophan in these phycocyanins has been established. The minimum molecular weight for phycocyanin from P. luridum is calculated to be 21 000 g/mole, and for phycocyanin extracted from S. lividus, 25 000 g/mole, values considerably smaller than those previously reported. N-terminal amino acid determinations of Plectonema calothricoides, P. luridum, and S. lividus phycocyanins by the 1-fluoro-2,4-dinitrobenzene method showed methionine to be terminal in all the phycocyanins examined. Peptide maps of tryptic digests of both ordinary and deuterio-phycocyanins from P. calothricoides and P. luridum showed a close resemblance, and these serve to confirm the identity between hydrogen and deuterio-phycocyanins originating in a particular blue-green alga.

Mass cultivation of algae in pure heavy water

AbstractStrains of the green algae Scenedesmus obliquus, Chlorella vulgaris, and C. pyrenoidosa 7‐11‐05, and of the blue‐green algae Fremyella diplosiphon, Plectonema calothricoides, Phormidium luridum, and Synechococcus lividus have been mass cultured autotrophically in essentially pure D2O. Closed Lucite rocking‐box units containing 5 liters of culture media can produce 1 to 2 g. (dry weight) per day of fully deuteriated algae or of fully deuteriated, fully 15N‐substituted algae. Racks for six such culture units are readily constructed from commerically available parts. Operation has been routine and essentially trouble‐free. The algae produced have proved to be an excellent source of completely isotopically substituted metabolites.