The Relation of Acetylene Reduction to Heterocyst Frequency in Blue-Green Algae

The variation of acetylene reduction activity and heterocystfrequency with culture age, was studied in five species of blue-greenalgae. The heterocyst frequency varied between 2.5 to 12.3 percent of total cells; and the acetylene reduction activity varied2.0-fold (average). It is suggested that an estimate of thenitrogen fixation rates in blue-green algae may be made by insitu heterocyst counts and acetylene reduction measurements.     

Nitrogen fixation and heterocysts in the blue-green alga Anabaena cylindrica

The site of nitrogen fixation in the blue-green alga Anabaenacylindrica Lemra (Fogg strain) was investigated. Less than 4%of the total nitrogen fixed during a relatively short period(5-15 min) was recovered in heterocysts. When estimated on thecellular nitrogen basis, vegetative cells can fix molecularnitrogen at the same rate as do heterocysts. There was no positivecorrelation between nitrogen fixation and heterocyst formation.Results do not support the hypothesis that the heterocyst isthe main site for nitrogen fixation in blue-green algae. ¹ This work was supported by grant (No. 38814) from the Ministryof Education. (Received July 23, 1971; )     

The pattern of sporulation in Anabaena circinalis and comments on the role of heterocysts in sporulation in blue-green algae.

Cells between two intercalary heterocysts differentiate at random into spores in A. circinalis. One or more cells, which fail to transform into spores, are present between the two adjacent spores, and these cells disorganize later. A critical C:N ratio regulates sporulation and heterocyst formation. During sporulation the reductive ability of the heterocyst gradually diminishes. It is concluded on the basis of this and other evidence that sporulation is regulated by interactions between heterocysts and vegative cells which are manifested in diverse patterns in different species of blue-green algae.     

FREQUENT HETEROCYST GERMINATION IN THE BLUE-GREEN ALGA GLOEOTRICHIA GHOSEI SINGH1

A unique feature, frequent heterocyst germination, has been observed in a nonsporulating mutant clone (of spontaneous origin) of the blue-green alga Gloeotrichia ghosei Singh. The controlling factor seems to be the presence of ammoniacal nitrogen in the medium. In addition, such a medium supports differentiation of successive crops of new heterocysts and their germination in the name medium and in the same algal culture. Contrary to previous observations with oilier blue-green algae, ammoniacal nitrogen does not seem to inhibit heterocyst differentiation in this alga. Both the parent alga and its mutant clone grow poorly in a nitrogen-free medium, which, although they are not completely free from bacteria, may indicate that they tire poor fixers or nonfixers. However, they form a large number of heterocysts under these conditions. The general conclusion is that the heterocysts of blue-green algae show a multiplicity of structure and function. In the present case they have reproductive function leading to direct propagation of the alga. The bearing of these findings on the interrelationships of the genera Gloeotrichia and Rivularia has been discussed. It has been concluded that the distinction between them is purely artificial.     

Acetylene reduction by nitrogen-fixing blue-green algae

Summary Known nitrogen-fixing species of blue-green algae are capable of reducing acetylene to ethylene, but acetylene is not reduced by Anacystis nidulans, which does not fix nitrogen. Cycad root nodules which contain blue-green algae as endophytes reduce acetylene. Acetylene reduction is inhibited by carbon monoxide. Nitrate or ammonium-nitrogen has no immediate effect on algae reducing acetylene, but algae grown on nitrate-nitrogen gradually lose their capacity to reduce acetylene. Nitrate-nitrogen also inhibits heterocyst formation in these algae and there is a fairly direct correlation between the abundance of heterocysts in a particular sample and its capacity to reduce acetylene. Aphanizomenon flosaquae reduces acetylene and fixes nitrogen in unialgal culture and there is strong presumptive evidence that these reductions are carried out by the alga rather than by associated bacteria. The molar ratios of ethylene: ammonia produced vary within the range 1.4–1.8.     

THE HETEROCYSTS OF BLUE-GREEN ALGAE (MYXOPHYCEAE)

1. Heterocysts are found in many species of filamentous blue-green algae. They are cells of slightly larger size and with a more thickened wall than the vegetative cells. 2. Structural details of the heterocyst are: the presence of three additional wall layers, the absence of granules, sparse thylakoid network throughout, except at the poles where a dense coiling of membranes occurs. Other characters include the two pores at opposite poles ‘plugged’ with refractive material called the polar granule. 3. Peculiarities in the pigment composition of the heterocyst include an abundance of carotenoids and absence of phycobilins, and a short-wave form of chlorophyll a. 4. Unique glycolipids and an acyl lipid, not found in the vegetative cells of the algae or in other plant cells, are associated with the heterocyst. The glycolipids constitute the laminated layer of the wall and probably regulate diffusion of substances through it, whereas the acyl lipids are supposed to function as carriers and intermediates in the biosynthesis of the wall. 5. The heterocysts develop from vegetative cells, and the visible changes during differentiation include cell enlargement, synthesis of additional wall layers, disappearance of granules and reorientation and synthesis of the thylakoids. 6. Heterocysts are formed sequentially with characteristic cellular spacing during the growth of cultures in medium free from combined nitrogen. 7. Various sources of combined nitrogen inhibit heterocyst formation when supplied in the culture medium. Ammonium salts are among the most powerful inhibitors. Heterocysts are formed simultaneously and within a short period after transference of ammonia-grown non-heterocystous filaments to ammonia-free medium. 8. Incompletely differentiated heterocysts or proheterocysts are found in cultures grown in the presence of combined nitrogen. If two or more proheterocysts are close together generally a single one develops to maturity after a competitive interaction in medium free from combined nitrogen. This indicates that heterocyst formation is completed in two phases: phase I, synthesis and conservation of macromolecules, which takes place during growth in ammonia-containing medium: and phase 11, morphological differentiation of the heterocyst which is unaccompanied by growth in cell number. In the ammonia-free medium phase 11 quickly succeeds phase 1 and the whole process appears as a continuum. 9. Heterocyst formation shows a definite requirement for light. Red light favours heterocyst formation, whereas green and blue light do not. The effects of light seem to be mainly due to photosynthesis, although some effects may be morphogenetic. 10. Studies with metabolic inhibitors have revealed the involvement of photosynthesis, respiration and protein synthesis in heterocyst formation. Photosynthesis provides carbon skeletons, whereas ATP is most probably supplied by oxidative metabolism. 11. Various functions have been assigned to the heterocyst from time to time. Their role in akinete formation is suggested by (i) the formation of akinetes adjacent to the heterocysts and (ii) prevention of sporulation by detachment of the heterocysts from the vegetative cells (potential akinetes). Despite substantial evidence for such a role, it is not applicable to all akinete-forming genera. 12. Heterocysts are now widely believed to be the site of nitrogen fixation in blue-green algae. The main facts in favour of such a role are: (i) fixation of nitrogen by all heterocystous algae, (ii) inhibition of heterocyst formation by combined nitrogen and (iii) direct observations on acetylene reduction by isolated heterocysts. 13. Some non-heterocystous and unicellular algae, and vegetative cells of heterocystous algae fix nitrogen under microaerophilic conditions suggesting that absence of oxygen favours nitrogenase activity. Heterocysts lack the oxygen-evolving photo-system 11, possess oxidative enzymes, and reduce externally supplied tetrazolium salts - all indicating that they are the most suitable sites for harbouring nitrogenase in aerobic conditions. 14. Heterocysts probably originated in the Precambrian in response to the earth's changing environment and seem to be the first example of morphological differentiation in the plant kingdom.     

Lipids of membranes and of the cell envelope in heterocysts of a blue-green alga

Summary Heterocysts of Anabaena cylindrica, isolated rapidly in the cold, were found—in contrast to earlier reports—to contain all of the same lipids and lipophilic pigments, and in about the same proportions, as vegetative cells. In broken filaments and in heterocysts damaged during isolation, the membrane lipids and certain pigments (myxoxanthophyll and an unidentified red pigment) break down rapidly. The glycolipids specific to heterocyst-forming blue-green algae are localized in the laminated layer of the heterocyst envelope. A possible role of the laminated layer is discussed.     

Taxonomic reexamination of the two species of blue-green algae,Calothrix scopulorum andC. crustacea

The taxonomic relationship between the 2 marine blue-green algae,Calothrix scopulorum andC. crustacea, which are considered to be conspecific by some authors, is discussed based on the statistical investigation of morphology with field and culture materials and on the phenological investigation. The presence or absence of intercalary heterocyst in the filament cannot be always used as a clear taxonomic character to distinguish the 2 species, judging from the result of culture experiment. However, it is confirmed that there are morphological differences between the two in the length of filament, the diameters of filament, trichome, hair, heterocyst and hormogon and the seriation of heterocyst in the filament, and that there are also ecological differences between the two in the color of plant, the tidal level of growth, the period of growth and the season of hormogon formation. From these facts it is concluded thatC. scopulorum andC. crustacea should be treated as separate species.     

Response of a wild type and a non-nitrogen-fixing mutant of Anabaena doliolum towards different amino acids

The effects of various amino acids on growth and heterocyst differentiation have been studied on wild type and a heterocystous, non-nitrogen-fixing (het+ nif-) mutant of Anabaena doliolum. Glutamine, arginine and asparagine showed maximum stimulation of growth. Serine, proline and alanine elicited slight stimulation of growth of wild type but failed to show any stimulatory effect on mutant strain. Valine, glutamic acid, iso-leucine and leucine at a concentration of as low as 0.1 mM were inhibitory to growth of parent type. Methionine, aspartic acid, threonine, cysteine, and tryptophan did not affect growth at concentrations lower than 0.5 mM. But at 1 mM, these amino acids were inhibitory. In addition to the stimulatory effects of glutamine, arginine and asparagine, the heterocyst frequency was also repressed by these amino acids. Glutamine and arginine at 2 mM completely repressed heterocyst differentiation in the mutant strain; however, other amino acids failed to repress the differentiation of heterocysts. Our results suggest that glutamine and arginine are utilized as nitrogen sources. This is strongly supported from the data of growth and heterocyst differentiation of mutant strain, where at least with glutamine there is good growth without heterocyst formation. Studies with glutamine and arginine on other N2-fixing blue-green algae may reveal the regulation of the heterocyst-nitrogenase sub-system.     

Components and activity of the photosynthetic electron transport system of intact heterocysts isolated from the blue-green alga Nostoc muscorum

Heterocysts of the blue-green alga Nostoc muscorum have been isolated by prolonged treatment with lysozyme. Quantitative data are presented which show the occurrence of cytochromes c-553, f-557 and b-563 in heterocysts in amounts comparable to vegetative cells. Particularly the content of the water-soluble cytochrome c-553 can be used to evaluate the intactness of a heterocyst preparation. Cytochrome f-557 has been partially purified and found to be a c-type cytochrome corresponding to cytochrome f of higher plants and other algae. Cytochrome b-559 is present in vegetative cells but not in heterocysts. The content of plastoquinone in heterocysts is reduced to 42% of the amount present in vegetative cells. These data suggest a degradation of Photosystem II during heterocyst differentiation. Measurements of photosynthetic electron transport in heterocysts proved the inability of the photosynthetic apparatus to carry out electron transport with electrons donated by water or diphenylcarbazide. In Tris-washed thylakoids from vegetative cells, however, diphenylcarbazide can act as an electron donor to Photosystem II.     

Protein-transients during heterocyst differentiation in Anabaena circularis and Cylindrospermum sp

The programme of protein synthesis accompanying cellular differentiation to the heterocyst following transfer of the blue-green algae Anabaena circularis and Cylindrospermum sp. (CBSC 1755) from ammonia-enriched medium to nitorgen-free medium was determined by polyacrylamide gel electrophoresis of whole proteins during successive intervals of differentiation. Besides this, total proteins and soluble amino acids were determined quantitatively. At least 4 sets of proteins can be distinguished on the basis of the time at which they are synthesized. Besides this, differentiation is distinguishable on the basis of the time at which their synthesis is turned off. The postmaturation stages revealed the synthesis of two sets in A. circularis andone in Cylindrospermum so. (CBSC 1755).     

Heterocyst Formation in the Blue-green Alga Anabaens doliolum--A Study of Some Aspects of Photoregulation

Of the different wavelengths of visible spectrum, red light(630–680 nm) supports maximum heterocyst production andits effect depends upon incident energy and the exposure period.The action spectrum of heterocyst formation corresponds withthe absorption spectrum of major photosynthetic pigments. Absenaof carbon dioxide is inhibitory to heterocyst formation, butsugars can partially substitute for carbon dioxide in the light,not in the dark. The inductive effect of red light is not reversedby low or high energy green or far-red. Such results are consistentwith a photosynthetic role of light in heterocyst formation,although a direct activation of some enzymes by light may alsobe of importance. Anabaena dollolum, blue-green alga, heterocyst formation, light     

Effects of some amino acid analogues on growth and heterocyst formation in the blue-green algaNostoc linckia

The effects of two amino acid analogues, viz., L-methionine-DL-sulphoximine and L-methyl-DL-methionine on growth, heterocyst differentiation and nitrogen fixation in the blue-green algaNostoc linckia have been studied with special reference to heterocyst spacing pattern. L-methionine-DL-sulphoximine strongly inhibited growth but produced an unusual number of heterocysts with changed heterocyst spacing pattern in both nitrogen-free and ammonium-containing media. L-methyl-DL-methionine was less effective than L-methionine-DL-sulphoximine. An attempt was also made to counteract the toxic effects of these analogues by supplying amino acids. Glutamine and methionine reversed the inhibitory effect of L-methionine-DL-sulphoximine while only methionine reversed the inhibitory effect of L-methyl-DL-methionine. Production of changed heterocyst spacing pattern in nitrogen-free and ammonium-containing media when supplemented with L-methionine-DL-sulphioximine suggests that ammonia may not be the inhibitor of heterocyst spacing pattern.     

Effects of concentrating phytoplankton on the acetylene-reduction assay for nitrogenase activity

SUMMARY.

• 1 The consequences of concentrating freshwater phytoplankton communities prior to measurement of nitrogenase activity using the acetylene-reduction assay were investigated.
• 2 Retention of heterocystous blue-green algae by 10 and 45 öm plankton nets was usually much less than 100% and the percent retention differed among blue-green algal species and varied for the same species both on different sampling dates and in different lakes. Retention of heterocyst numbers and helerocyst volume during concentration differed from that of total cell volume of heterocystous blue-green algae.
• 3 Effects of concentration on specific nitrogcnase activity varied among the lakes studied. In Lake Bysjön activity decreased on all sampling occasions, in Lake Trummen there was no apparent effect, and in Lake Vaxjosjon both results were found.
• 4 Effects on nitrogenase activity of mechanical disturbance during concentration and of increased pH. reduced carbon availability. light inhibition and subsaturation. photorespiration and oxygen supersaturation in concentrated samples are discussed. Interactions between these factors are suggested to explain the varying responses in the three lakes.
• 5 It is concluded that phytoplankton should not be concentrated in the acetylene-reduction assay for nitrogenase activity, since both volumetric and cell concentration factors are inadequate and effects of concentration on specific nitrogenase activity are not predictable.

     

The electrophoretic isolation and partial characterization of three chlorophyll-protein complexes from blue-green algae.

Three chlorophyll-protein complexes have been resolved from blue-green algae using an improved procedure for membrane solubilization and electrophoretic fractionation. One complex has a red absorbance maximum of 676 nm and a molecular weight equivalency of 255 000 +/- 15 000. A second complex has an absorbance maximum of 676 nm, a molecular weight equivalency of 118 000 +/- 8000, and resembles the previously described P-700-chlorophyll a-protein (CPI) of higher plants and algae. The third chlorophyll-protein has a red absorbance maximum of 671 nm and a molecular weight equivalency of 58 000 +/- 5000. Blue-green algal membrane fractions enriched in Photosystem I and heterocyst cells do not contain this third chlorophyll-protein, whereas Photosystem II-enriched membrane fractions and vegetative cells do. A component of the same spectral characteristics and molecular weight equivalency was also observed in chlorophyll b-deficient mutants of barley and maize. It is hypothesized that this third complex is involved in some manner with Photosystem II.     

The role of nitrogen as a growth limiting factor in the eutrophic Lake Vesijärvi,southern Finland

The significance of nitrogen for algal growth was studied in Lake Vesijärvi in 1979 and 1980 by algal bioassay, using Selenastrum capricornutum and Anabaena cylindrica as test organisms. Nitrogen limited the growth of Selenastrum for the major part of the investigation period, while phosphorus seemed to be the most limiting factor for Anabaena. This difference was reflected in the in situ succession of phytoplankton. As the ratio of inorganic nitrogen to phosphate phosphorus became smaller, nitrogen-fixing blue-green algae became dominant. Nitrogen fixation was greatest at the beginning of July, coinciding with maximum heterocyst numbers.     

Algal nitrogen fixation in the tropics

Summary a)Nitrogen fixation in rice fields. Nitrogen-fixing blue-green algae grow abundantly in tropical regions and are particularly common in paddy fields. Their possible role in the nitrogen accumulation of soil has been studied. The most vigorous nitrogen-fixing blue-green algae have been assessed for use as green manure in rice fields and favorable effects have been reported in India and other countries. b)Nitrogen fixation by algae in water. The planktonic blue-green algae occur abundantly at certain time of the year in sea water and lake water, and some of them are known to be nitrogen fixers. Certain Japanese species of blue-green algae can withstand high temperatures including ten nitrogen-fixing species from hot-spring waters. c)Nitrogen fixation by symbiotic blue-green algae. Certain species of blue-green algae form associations with other organisms such as fungi, liverworts, ferns and seed plants. The relationship between these two organisms is on one occasion commensal and on others symbiotic. Certain symbiotic blue-green algae are provided with the ability to fix the atmospheric nitrogen.     

Some characteristics of two morphological mutants of Nostoc linckia induced by nitrosoguanidine.

The blue-green alga Nostoc linckia was treated with nitrosoguanidine and two classes of morphological mutant clones were isolated. One class shows certain abnormal phenotypic features of vegetative cells, spores, and heterocysts. It has increased heterocyst frequency and impaired growth rate. The other class exhibits an altered heterocyst spacing pattern. Both classes of mutants have reduced nitrogenase activity.     

Observations of Toxic Blue-Green Algae (Cyanobacteria) in Some Scandinavian Lakes

Blooms of blue-green algae from 51 eutrophic Scandinavian lakes were investigated during the period 1978–1984, to ascertain the occurrence of toxinogenic species. Toxicity assays were performed by intraperitoneal injection of suspensions of freeze-dried algal material in mice. Toxin-producing blue-green algae were found in 30 lakes. They belonged to 11 different species of the six genera Anabaena, Aphanizomenon, Gomphosphaeria, Microcystis, Nodularia and Oscillatoria. The presence of toxinogenic strains of blue-green algae seemed quite constant in several of the localities studied. In some lakes, more than one toxic species were found to develop simultaneously. The level of toxicity showed large variation (MLD100, 6 to > 2500 mg/kg), but clinical and pathological changes were quite uniform. The results indicate that water-blooms of toxin-producing blue-green algae, in the geographical area in question, are regionally widespread. In some localities, blooms of blue-green algae are apparently always toxic. Several aspects of the toxic blue-green algae problem are discussed.     

太湖蓝藻滤液的遗传毒性研究

蓝藻爆发是环境污染引发的重要事件之一,随之产生的蓝藻毒素又直接危及区域水安全.该论文采用蚕豆和大蒜根尖微核试验研究了太湖蓝藻暴发期间蓝藻滤液的遗传毒性.结果表明,同阴性对照相比,所有试验处理对蚕豆根尖细胞微核发生率的影响显著增加;对大蒜根尖细胞微核发生率而言除蓝藻滤液8倍稀释液的影响不显著外,其它水平效应显著高于阴性对照,而且表现出一定的剂量效应.暴发期蓝藻滤液原液对蚕豆根尖细胞微核发生率影响显著高于阳性对照(0.8mg·mL^-1环磷酰胺)的效应,从而说明蓝藻暴发时期蓝藻滤液具有较强的遗传毒性.通过微核试验效果分析,蚕豆作为植物监测系统的敏感性和稳定性都优于大蒜材料.