FREEZE-DRYING OF BLUE-GREEN ALGAE FOR ELECTRON MICROSCOPE STUDIES1

Cultures of Anabaena cylindrica Lemm. and Eucapsis sp. were harvested, freeze-dried, and prepared for electron microscope studies. A comparison of the freeze-dried preparations was made with control specimens not freeze-dried. Fixation and embedding were according to the Ryter and Kellenberger technique. The photosynthelic thylakoids of the freeze-dried cells were more distinct and less distorted than those of the control cells. Freeze-dried Eucapsis sp. cells exhibited a prominent mucous capsule, whereas in the nonfreeze-dried, no such capsule could be discerned.     

EVIDENCE A PHOTOPROTECTIVE FOR SECONDARY CAROTENOIDS OF SNOW ALGAE1

Snow algae occupy a unique habitat in high altitude and polar environments. These algae are often subject to extremes in nutrient availability, acidity, solar irradiance, desiccation, and ambient temperature. This report documents the accumulation of secondary carotenoids by snow algae in response to the availability of nitrogenous nutrients. Unusually large accumulations of astaxanthin esters in extra-chloroplastic lipid globules produce the characteristics red pigmentation typical of some snow algae (e.g. Chlamydomonas nivalis (Bauer) Wille). Consequently these compounds greatly reduce the amount of light available for absorption by the light-harvesting pigment-protein complexes, thus potentially limiting photoinhibition and photodamage caused by intense solar radiation. The esterification of astaxnthin with fatty acids represents a possible mechanism by which this chromophore can be concentrated within cytoplasmic globules to maximize its photoprotective efficiency.     

THE CAROTENOIDS OF FOUR BLUE-GREEN ALGAE1

The carotenoids of 4 species of blue-green algae, Anabaena variabilis, Phormidium persicinum, P. ectocarpi, and P. fragile, were investigated. In each, ft-carotene was a major pigment and the only carotene detected. The xanthophylls present in Anabaena variabilis were echinenone, canthaxanthin, and myxo-xanthophyll. Each of the Phormidium species contained zeaxanthin as the major xanthophyll. In each, this was accompanied by trace amounts of echinenone and isocryptoxanthin. In addition, 2 new xanthophylls, spectrally resembling ^-carotene, were found in Phormidium persicinum and P. ectocarpi, while another, with a spectrum similar to that of myxoxanthophyll, was found in P. fragile.     

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.     

SIMPLE CONDITIONS FOR GROWTH OF UNICELLULAR BLUE-GREEN ALGAE ON PLATES1, 2

The efficiencies of plating of 2 cultures of unicellular blue-green algae, 1 coccoid and 1 rod-shaped, were studied systematically. Reproducible colony growth and accurate viable counts are dependent on the use of a low agar concentration, and on the sterilization of the agar separately from the mineral components of the medium.     

TAXONOMIC CONFUSION CONCERNING CERTAIN FILAMENTOUS BLUE-GREEN ALGAE1

Throughout a long history many filamentous bacteria may have been identified in natural collections as blue-green algae. This problem has been especially acute regarding the thermophilic species of hot springs, especially at the higher temperatures. It is suggested that in the absence of pure cultures, the minimal criteria for distinguishing filamentous bacteria from blue-green algae microscopically should be: (1) observation of the chlorophyll fluorescence with a fluorescent microscope and (2) demonstration of light-dependent ¹⁴CO₂ fixation autoradiographically. Pure cultures of a number of filamentous thermophiles have been obtained from habitats at temperatures above 60 C. These cultures resemble microscopically the natural material, grow only heterot rophically, and do not contain chlorophyll.     

ALGAE AS COMPETITORS FOR GLUCOSE WITH HETEROTROPHIC BACTERIA1

Dissolved organic carbon (DOC) constitutes the bulk of organic carbon in aquatic environments. The importance of DOC utilization by mixotrophic algae is unclear since heterotrophic bacteria are regarded as more efficient users. We tested the hypothesis that algae decrease the DOC concentration in the light to lower levels than in darkness resulting in competitive exclusion of heterotrophic bacteria according to the mechanistic competition theory. We investigated (a) the uptake kinetics of glucose as a model substrate by two cultured algae and mixed bacteria populations, (b) the competition for glucose between algae and bacteria in chemostats, (c) the effect of discontinuous glucose supply in chemostats, and (d) the minimum glucose concentrations achieved in cultures of algae and bacteria. Bacteria showed higher specific‐glucose‐uptake rates than algae. In chemostats, algae became extinct in the dark and coexisted in the light where they decreased bacteria to lower densities. Discontinuous glucose supply promoted the algae compared to continuous substrate addition. Several algae consumed glucose to lower concentrations in the dark than in the light and showed lower or equal residual glucose concentrations than bacteria. Residual concentrations were not related to allometric traits (cell volume) and photosynthetic potential (chl content). Overall, the hypothesis was not supported, and mechanisms of competition for DOC obviously differed from those for particulate prey. However, since some algae showed lower or equal residual glucose concentrations than bacteria, algal dark uptake of DOC may be important in deep layers of many waters.     

INTERCEPTION OF ATMOSPHERIC FIXED NITROGEN AS AN ADAPTIVE ADVANTAGE OF SCUM FORMATION IN BLUE-GREEN ALGAE1

Scum formation by blue-green algae has been interpreted as a nonadaptive failure of the buoyancy control mechanism and, alternatively, as an adaptive mechanism to reduce inorganic carbon limitation. Data from Lake Valencia, Venezuela, are used to illustrate the principle that scum formers intercept significant amounts of fixed N deposited from the atmosphere at the water surface. Interception of fixed N at the surface can confer a significant selective advantage for populations that are strongly N limited, as in Lake Valencia. This additional adaptive advantage to scum formation may be alternative lo or complementary to the possible relief of carbon limitation.     

PREPARATION OF METABOLICALLY ACTIVE PROTOPLASTS OF BLUE-GREEN ALGAE1

Protoplasts that remained metabolically active for several days were obtained by treating cells of Microcystis aeruginosa, Anacystis nidulans, and Anabaena flos-aquae with lysozyme. Photosynthetic and respiratory rates were near those of control cells. Lysozymeresistant cells were isolated which may be genetic mutants.     

ALGAE AS WATER QUALITY INDICATORS FOR A DYSTROPHIC POND

Information on the population structure of planktonic dinoflagellates is reported in the coral reef-mangrove ecosystem at Pelican Cays, Belize. Six sites examined included: Cat Cay, Douglas Cay, Elbow Cay, Fisherman's Cay, Lagoon Cay and Manatee Cay. A spectacular and rich dinoflagellate taxa including oceanic, coastal and offshore species are illustrated. The presence of oceanic species in the studied cays is an unexpected observation since dinolfagellate assemblages are virtually enclosed within ponds bordered by coral ridges that limits water exchange with the open ocean except during storm events. I am also reporting significant differences in the dinoflagellate associations among the studied cays. Dominant taxa included 16 Proroperidinium species, 11 Gonyaulax species, and ten Ceratium species. Only six planktonic species were harmful. Bloom forming species included Ceratium furca and Gonyaulax polygramma. A much more diverse authotrophic and heterotrophic dinoflagellate population characterizes the Pelican Cays than previously suspected. Some species are reported the first time: Protoperidinium belizeanum sp. nov., P. pyrum Balech, P. steidingerae Balech, P. depressum (Bailey) Balech, and P. divergens (Ehrenberg) Balech. These results demonstrate that the Belizean coral reef-mangrove ecosystem is a delicate and species-rich environment, and as such, should be protected and preserved.     

ANTINEOPLASTIC ACTIVITY OF CULTURED BLUE-GREEN ALGAE (CYANOPHYTA)1

A large-scale screening program was initiated to evaluate laboratory-cultured blue-green algae (cyanobacteria) as a source of novel antineoplastic agents. Approximately 1000 cyanophyte strains from diverse habitats were cultured to provide extracts for testing. The screening program identified the families Scytonemataceae and Stigonemataceae as prolific producers of novel cytotoxic compounds. Rates of rediscovery of known compounds were relatively low.     

EVIDENCE FOR THE REPAIR OF OZONE-INDUCED MEMBRANE INJURY

The increase in [¹⁴C]-2-deoxy-D-glucose uptake by leaf discs 24 hr after fumigation was used as a measure of ozone injury to pinto bean leaves (Phaseolus vulgaris). This method showed that the primary leaves were most affected by ozone when plants were 10 to 12 days old, which coincided with the time of maximum leaf necrosis. However, 8-day-old plants, which had no visible leaf injury, still showed a higher uptake rate than controls, indicating that injury occurred at the cellular level. In these younger plants, uptake was shown to return to normal over a 5 day period. Moreover, the rate of this “repair” was retarded by cold or continuous darkness, enhanced by continuous light, and very markedly increased by glucose applied to the leaves. The timing of the glucose application was not critical, nor did H₂O or mannitol have an effect. The results suggest that ozone injury at the cellular level can be repaired by energy-dependent processes so that necrosis of the leaf tissue does not occur. These experiments also show that conditions and treatments after ozone exposure can alter the degree of ozone injury.     

ANTIVIRAL ACTIVITY OF CULTURED BLUE-GREEN ALGAE (CYANOPHYTA)1

Lipophilic and hydrophilic extracts from approximately 600 strains of cultured cyanophytes, representing some 300 species, were examined for antiviral activity against three pathogenic viruses. Approximately 10% of the cultures produced substances that caused significant reduction in cytopathic effect normally associated with viral infection. The screening program identified the order Chroococcales as commonly producing antiviral agents.     

AN IMPROVED METHOD FOR OBTAINING AXENIC CLONES OF PLANKTONIC BLUE-GREEN ALGAE1,2

Axenic clones from 5 isolates of Anabaena flosaquae, 1 isolate of Microcystis acruginosa, and 1 isolate of Aphanizomenon flos-aquae were obtained by a combination of steps that provided a 1000-fold reduction in the bacteria-algae ratio and permitted bacteria-free filaments or cells to be isolated and grown from agar pour plates. The first step consisted of the addition of phenol to a dark-treated culture to selectively reduce the numbers of actively growing bacteria while leaving the resting algal cells viable. The next steps involved washing the treated algal suspension on a Millipore filter pad or membrane followed by plating in washed agar containing buffered mineral medium plus vitamins and soil extract. The final steps consisted of incubating the agar pour plates, coring bacteria-free filaments or cells, culturing the agar cores in a buffered mineral medium, and rigorously testing the resulting cultures for bacteriological contamination. Between 50 and 90% of the cores grew, and of these about 50% were judged axenic. The method, with appropriate adaptations, should be suitable for obtaining axenic clones of other freshwater and marine algae.     

A QUALITATIVE AND QUANTITATIVE STUDY OF PLASTOQUINONE A IN TWO THERMOPHILIC BLUE-GREEN ALGAE1

The thermophilic blue-green alga Synechococcus lividus strain Y52 was shown to have plastoquinone (PQ) types A, B, and C. The values PQA per cell and chlorophyll a per cell are presented with the changes in the ratio of PQA to chlorophyll a for cells grown at different light intensities.     

BLUE-GREEN ALGAE FROM BERMUDA WATERS: ECOLOGICALLY SELECTED VARIATIONS OF A SINGLE SPECIES

Three strains were isolated from Bermuda waters as unialgal cultures. Although identical in cell shape, cell size, and general growth features, marked differences in pigmentation, filament length, and sheath thickness were noted. These differences are explained as being due to differences in physical conditions of the areas of isolation of the 3 strains. It is concluded that the 3 strains are ecologically selected mutants of the single species, Schizothrix calcicola.     

分离蓝藻原生质球的新方法：青霉素－溶菌酶法

蓝藻原生质球(体)的研究,至今尚未取得决定性突破,成为细胞壁生物之中的唯一例外。这不仅表现在原生质球(体)的再生没有成功,而且分离制备方法亦存在很大问题。从1967年沿用至今的Crespi-Biggins溶菌酶法不仅在质量上不能得到真正理想的原生质球,而且数量上也达不到。由于在分离过程中细胞大量破裂,原生质球的产率很     

COMPARATIVE PHYSIOLOGY AND MORPHOLOGY OF SIX STRAINS OF STIGONEMATACEAN BLUE-GREEN ALGAE1

Six strains of branched blue-green algae were examined in a search for lines to an explanation for apparent noncompetitiveness. Classical taxonomic treatments were often inadequate for confident species determination; forms that were very differ their morphologically frequently “keyed” to the same species. Strain distinctions based on comparative morphological and physiological studies were inconclusive. With the exception of 1 species, there were no substantial differences in physiological rates. In addition to the branching habit, diversity of cellular form was found to be an outstanding group characteristic. Individual cells of developing trichomes became a spore-like and then divided to produce either cell clusters or lateral branches. The eventual separation of daughter cells by sheath materials may be analogous to spore formation in Nostocales and could be the factor which determines the nature of these organisms. The Stigonemataceae may not represent the pinnacle of blue-green algal development but may, instead, be a primitive and basic form linking coccoid and filamentous algae.