Effect of Temperature on Blue-Green Algae (Cyanobacteria) in Lake Mendota

The temperature optimum for photosynthesis of natural populations of blue-green algae (cyanobacteria) from Lake Mendota was determined during the period of June to November 1976. In the spring, when temperatures ranged from 0 to 20°C, there were insignificant amounts of blue-green algae in the lake (less than 1% of the biomass). During the summer and fall, when the dominant phytoplankton was blue-green algae, the optimum temperature for photosynthesis was usually between 20 and 30°C, whereas the environmental temperatures during this period ranged from 24°C in August to 12°C in November. In general, the optimum temperature for photosynthesis was higher than the environmental temperature. More importantly, significant photosynthesis also occurred at low temperature in these samples, which suggests that the low temperature alone is not responsible for the absence of blue-green algae in Lake Mendota during the spring. Temperature optima for growth and photosynthesis of laboratory cultures of the three dominant blue-green algae in Lake Mendota were determined. The responses of the two parameters to changes in temperature were similar; thus, photosynthesis appears to be a valid index of growth. However, there was little photosynthesis by laboratory cultures at low temperatures, in contrast to the natural samples. Evidence for an interaction between temperature and low light intensities in their effect on photosynthesis of natural samples is presented.     

Effect of Interactions Among Algae on Nitrogen Fixation by Blue-Green Algae (Cyanobacteria) in Flooded Soils

Nitrogen fixation (C₂H₂ reduction) by algae in flooded soil was limited by interactions within the algal community. Nitrogen fixation by either indigenous algae or Tolypothrix tenuis was reduced severalfold by a dense suspension of the green alga Nephrocytium sp. Similarly, interactions between the nitrogen-fixing alga (cyanobacterium) Aulosira 68 and natural densities of indigenous algae limited nitrogen-fixing activity in one of two soils examined. This was demonstrated by developing a variant of Aulosira 68 that was resistant to the herbicide simetryne at concentrations that prevented development of indigenous algae. More nitrogen was fixed by the resistant variant in flooded soil containing herbicide than was fixed in herbicide-free soil by either the indigenous algae or indigenous algae plus the parent strain of Aulosira. Interference from indigenous algae may hamper the development of nitrogen-fixing algae introduced into rice fields in attempts to increase biological nitrogen fixation.     

Pseudomonas aeruginosa Chemotaxis Associated with Blooms of N(2)-Fixing Blue-Green Algae (Cyanobacteria)

Pseudomonas aeruginosa (Schroeter) Migula, a numerically significant bacterium found during N(2)-fixing blooms of the blue-green algae (cyanobacteria) Anabaena sp. in the Chowan River, North Carolina, was chemotactically attracted to amino acids when tested in a radioassay. The bacterium was labeled with P(i), and the disintegrations per minute determined by liquid scintillation counting were proportional to the number of cells accumulating in microcapillaries containing amino acids. Positive chemotaxis was observed toward all of the amino acids tested, although the degrees of response varied. Since many nitrogen-fixing blue-green algae secrete nitrogenous compounds, this attraction may be instrumental in establishing a symbiotic relationship between this bacterium and blue-green algae in freshwater.     

Pseudomonas aeruginosa Chemotaxis Associated with Blooms of N2-Fixing Blue-Green Algae (Cyanobacteria)

Pseudomonas aeruginosa (Schroeter) Migula, a numerically significant bacterium found during N₂-fixing blooms of the blue-green algae (cyanobacteria) Anabaena sp. in the Chowan River, North Carolina, was chemotactically attracted to amino acids when tested in a radioassay. The bacterium was labeled with ³²P_i, and the disintegrations per minute determined by liquid scintillation counting were proportional to the number of cells accumulating in microcapillaries containing amino acids. Positive chemotaxis was observed toward all of the amino acids tested, although the degrees of response varied. Since many nitrogen-fixing blue-green algae secrete nitrogenous compounds, this attraction may be instrumental in establishing a symbiotic relationship between this bacterium and blue-green algae in freshwater.     

Nitrogen Fixation by Thermophilic Blue-Green Algae (Cyanobacteria): Temperature Characteristics and Potential Use in Biophotolysis

Thermophilic, nitrogen-fixing, blue-green algae (cyanobacteria) were investigated for use in biophotolysis. Three strains of Mastigocladus laminosus were tested and were found to be equally effective in biophotolysis as judged by nitrogenase activity. The alga, M. laminosus NZ-86-m, which was chosen for further study, grew well in the temperature range from 35 to 50°C, with optimum growth at 45°C, at which temperature acetylene reduction activity was also greatest. The maximum tolerable temperature was 55°C. Acetylene reduction activity was saturated at a light intensity of 1 × 10⁴ ergs cm⁻² s⁻¹. Atmospheric oxygen tension was found to be slightly inhibitory to acetylene reduction of both slowly growing and exponentially growing cultures. Nonsterile continuous cultures, which were conducted to test problems of culture maintenance, could be operated for 2 months without any significant decrease in nitrogenase activity or contamination by other algae. Nitrogen-starved cultures of M. laminosus NZ-86-m produced hydrogen at comparable rates to Anabaena cylindrica. The conversion efficiency of light to hydrogen energy at maximum rates of hydrogen production was 2.7%.     

Lytic Organisms and Photooxidative Effects: Influence on Blue-Green Algae (Cyanobacteria) in Lake Mendota, Wisconsin

The effects of exposure to high light intensities on blue-green algal (cyanobacterial) populations were examined in Lake Mendota, Wis. The algal populations were shown to be susceptible to inhibition of photosynthetic activity and pigment bleaching as a result of exposure. These effects generally influence only a small percentage of the lake population and thus are probably not important in causing major declines in chlorophyll a. Lytic organisms were shown to increase in numbers in the lake in response to the seasonal development of blue-green algae, reaching values of greater than 1,000 plaque-forming units per ml in midsummer. Both bacteria and protozoa were observed in plaque zones, but it could not be determined whether these lytic organisms had a major role in algal biomass declines.     

Phycobilisomes in Blue-Green Algae

Fifteen species of freshwater blue-green algae, including unicellular, filamentous, and colonial forms, were subjected to a variety of fixatives, fixation conditions, and stains for comparison of the preservation of phycobilisomes. Absorption spectra of the corresponding in vivo and released photosynthetic pigments, in 10 of the species that were maintained in culture, demonstrated the presence of phycocyanin in all 10 species and phycoerythrin in only 2 of them. Spectroscope and electron microscope evidence was obtained for localization of phycobiliproteins in phycobilisomes of Nostoc muscorum. Phycobilisomes were observed in all species examined in situ, strenghening the hypothesis that phycobilisomes are common to all phycobiliprotein-containing photosynthetic blue-green algae.     

Photooxidative Death in Blue-Green Algae

When incubated in the light under 100% oxygen, wild-type blue-green algae (Anacystis nidulans, Synechococcus cedrorum) die out rapidly at temperatures of 4 to 15 C, and at 35 C (or at 26 C in the case of S. cedrorum) in the absence of CO(2). Photosynthesis is impaired in these cells long before they die. Blocking of photosystem II at high temperatures in the presence of CO(2) sensitizes the algae to photooxidative death. Photooxidative death and bleaching of photosynthetic pigments are separable phenomena. Photooxidative conditions were demonstrated in Israeli fish ponds using A. nidulans as the test organism during dense summer blooms, when dissolved CO(2) is low, and in winter, when water temperatures generally drop below 15 C. This finding suggests that photooxidative death may be responsible for the sudden decomposition of blue-green blooms in summer, and may be a factor in the absence of blue-green blooms in winter.     

The Lipid Phase of Thylakoid and Cytoplasmic Membranes from the Blue-Green Algae (Cyanobacteria), Anacystis nidulans and Anabaena variabilis

The lipid phases of the thylakoid and cytoplasmic membranesfrom the blue-green alga, Anacystis nidulans, were studied bya spin-probe method using 2-(14-carboxytetradecyl)-2-ethyl-4,4-dimethyl-3-oxazolidinyloxyl.The thylakoid and cytoplasmic membranes of this alga were bothin the liquid crystalline state at growth temperature, and inthe phase separation state at about 0?C. The thylakoid membranesentered the phase separation state at a temperature higher thanthe cytoplasmic membranes. The lipid phase of the thylakoidmembranes from Anabaena variabilis was studied in a similarway, and these membranes were found also to undergo the phasetransition. The temperature for the onset of the phase separationand the fluidity of the membrane lipids of both algae dependedon the growth temperature of the culture. (Received April 9, 1984; Accepted June 1, 1984)     

Reversible and Irreversible Inactivation of Photosynthesis in Relation to the Lipid Phases of Membranes in the Blue-Green Algae (Cyanobacteria) Anacystis nidulans and Anabaena variabilis

The Arrhenius plots of photosynthetic oxygen evolution in theblue-green algae Anacystis nidulans and Anabaena variabiliswere composed of two straight lines with break points whichwere very close to temperatures for the onset of phase separationof the thylakoid membranes. Irreversible inactivation of photosynthesisbegan to appear at the same temperature as the onset of phaseseparation of the cytoplasmic membranes in A. nidulans. Electrolytesbegan to leak from the cytoplasm into the outer medium, indicatingthat the permeability of the cytoplasmic membranes increasedwhen they entered the phase separation state. In A. variabilis,in which the cytoplasmic membranes had remained in the liquidcrystalline state above 0?C, no irreversible damage to photosynthesisnor leakage of electrolytes was observed between 0 and 20?C.These findings suggest that photosynthesis of the blue-greenalgae is reversibly suppressed when only the thylakoid membranesare in the phase separation state, and irreversibly inactivatedwhen the cytoplasmic membranes are in the phase separation state. (Received April 9, 1984; Accepted June 19, 1984)     

Carbon Concentration Mechanism(s) in Unicellular Green Algae and Cyanobacteria

Unicellular green algae and cyanobacteria have mechanism(s) to actively concentrate dissolved inorganic carbon (DIC) into the cells, only if they are grown with air levels of CO₂. The DIC concentration mechanisms are environmental adaptations to actively transport and accumulate inorganic carbon into the chloroplasts of green algae or into the carboxysomes of cyanobacteria. The current working model of cyanobacterial carbon concentration mechanism consists of at least two basic components: an active C_i transport system and a Rubisco-rich polyhedral carboxysome. In case of unicellular green algae, the working model for DIC concentration mechanism includes several isoforms of carbonic anhydrase (CA), and ATPase driven active bicarbonate transporters at the plasmalemma and at the inner chloroplast envelopes. In the past twenty years, significant progress has been made in isolating and characterizing the isoforms of carbonic anhydrase. However, active transporters are yet to be characterized. This mini-review summarizes the current status of research on DIC-pumps including its significance and possible application to increase the productivity of plants of economic importance.     

Pyridine Nucleotide-Dependent Glucose Dehydrogenase Activity in Blue-Green Algae

Pyridine nucleotide-dependent glucose dehydrogenase activity (GPND) is described for the first time in cell-free extracts of certain blue-green algae. When glucose is added to these crude cell extracts, nicotinamide adenine dinucleotide phosphate is reduced at twice the rate as nicotinamide adenine dinucleotide; but evidence suggests that this activity is due to a single enzyme. The distribution and level of GPND in selected blue-green algae correlates with the heterotrophic potential of each species. In all blue-green algae where GPND was detected, O(2) uptake coupled to the GPND reaction was also observed. Both GPND and O(2) uptake apparently occur in the soluble fraction of the cell. An essential role for GPND in the heterotrophic metabolism of blue-green algae is postulated.     

Metabolism of delta-Aminolevulinic Acid in Red and Blue-Green Algae

δ-Aminolevulinic acid was incorporated in vivo into C-phycocyanin and B-phycoerythrin in two species of the Rhodophyta (Cyanidium caldarium, Porphyridium cruentum) and three species of the Cyanophyta (Anacystis nidulans, Plectonema boryanum, Phormidium luridum). Amino acid analysis of phycocyanin-¹⁴C from C. caldarium cells which had been incubated with δ-aminolevulinate-4-¹⁴C showed that 84% of the radioactivity incorporated was present in the phycocyanobilin chromophore and less than 16% of the radioactivity cochromatographed with amino acids. These results indicate that δ-aminolevulinate is utilized predominantly via the porphyrin pathway in C. caldarium. Conversely, analysis of phycocyanin-¹⁴C prepared from cells of A. nidulans, P. boryanum, and P. luridum which had been incubated with radiolabeled δ-aminolevulinate demonstrated that 85%, 81%, and 93%, respectively, of the radioactivity incorporated cochromatographed with amino acids. The ratio of incorporated radioactivity in amino acids and phycoerythrobilin was 40:60 in P. cruentum phycoerythrin obtained from cells which had been incubated with δ-aminolevulinate-4-¹⁴C. Succinate-2-3-¹⁴C appeared to be as good a carbon source of amino acids as did C₄ and C₅ of δ-aminolevulinate. These data demonstrate a major alternate route (other than the porphyrin pathway) of δ-aminolevulinate metabolism in red and blue-green algae. The factors responsible for the extent to which δ-aminolevulinate is utilized for synthesis of porphyrins and their derivatives and routes of δ-aminolevulinate catabolism in the organisms employed are discussed.     

Fatty Acid Composition of Unicellular Strains of Blue-Green Algae

The fatty acids of 34 strains of unicellular blue-green algae provisionally assigned to the genera Synechococcus, Aphanocapsa, Gloeocapsa, Microcystis, and Chlorogloea by Stanier et al. have been chemically characterized. The strains analyzed can be divided into a series of compositional groups based upon the highest degree of unsaturation of the major cellular fatty acids. Twenty strains fall into the group characterized by one trienoic fatty acid isomer (alpha-linolenic acid), and seven strains fall into a group characterized by another trienoic acid isomer (gamma-linolenic acid). These groups in many cases correlate well with groupings based upon other phenotypic characters of the strains, e.g., deoxyribonucleic acid base composition. The assignment of a strain to a compositional group is not altered when the strain is grown under a variety of different culture conditions. All strains contain glycolipids with the properties of mono- and digalactosyldiglycerides.     

Biochemical Basis of Obligate Autotrophy in Blue-Green Algae and Thiobacilli

Differential rates of incorporation of sugars, organic acids, and amino acids during autotrophic growth of several blue-green algae and thiobacilli have been determined. In obligate autotrophs (both blue-green algae and thiobacilli), exogenously furnished organic compounds make a very small contribution to cellular carbon; acetate, the most readily incorporated compound of those studied, contributes about 10% of newly synthesized cellular carbon. In Thiobacillus intermedius, a facultative chemoautotroph, acetate contributes over 40% of newly synthesized cellular carbon, and succinate and glutamate almost 90%. In the obligate autotrophs, carbon from pyruvate, acetate, and glutamate is incorporated into restricted groups of cellular amino acids, and the patterns of incorporation in all five organisms are essentially identical. These patterns suggest that the tricarboxylic acid cycle is blocked at the level of alpha-ketoglutarate oxidation. Enzymatic analyses confirmed the absence of alpha-ketoglutarate dehydrogenase in the obligate autotrophs, and also revealed that they lacked reduced nicotinamide adenine dinucleotide oxidase, and had extremely low levels of malic and succinic dehydrogenase. These enzymatic deficiencies were not manifested by the two facultative chemoautotrophs examined. On the basis of the data obtained, an interpretation of obligate autotrophy in both physiological and evolutionary terms has been developed.