N2-fixing Cyanobacteria Research Articles

Polymixis and algal production in a tropical lake: latitudinal effects on the seasonality of photosynthesis

SUMMARY. 1. Phytoplankton production was measured during 1981–82 in Bahia de Puno. a large polymictic system that is part of LakeTiticaca in the tropical Andes (Peru‐Bolivia), Photosynthesis followed aweak seasonal pattern through each 12‐month cycle but the largestvariations occurrud between years.2. The large temporal variations in productivity appeared to becontrolled by biological events rather than by the direct effeets ofseasonal or aseasonal physical processes. Major shifts in production overthe 2‐year period were attributable to the proportional abundance andactivity of N2‐fixing blue‐green algae. Production was uncorrelated withthe seasonal radiation cycle.3. In vivo fluorescence and photosynthetic assays revealed largechanges in phytoplankton community structure over time and depth.The shifts in vertical structure were associated with changes in transparency and water column stabilily.Physiological as well as floristiceffects dictated the variations in fluorescence per unit chlorophyll a.4. An analysis of twenty‐seven primary productivity data sets fromdifferent latitudes shtiwed that Bahia dc Puno resembled other tropicallakes in its relatively weak coupling between algal photosynthesis andseasonal variations in light. Productivity in the temperate zone correlated with the annual cycle of incoming radiation while the tropicalproduction data did not. For many of the tropical lakes, but fewtemperate lakes, the between‐month variance in primary production wassignificantly higher than the between‐month variance for incomingradiation. There was a significant positive relationship between maximum production variance explained hy light (maximum r2 for each dataset) and latitude.5. As in many tropical lakes. Bahia de Puno experiences moderatelylarge variations in algal photosynthesis.The muted seasonal cycle of light explains only a small portion of the total variation In productivity, and other factors such as weuther‐related events are disproportionately important.

Properties of the glyceraldehyde-3-P dehydrogenase in heterocysts and vegetative cells of cyanobacteria

Glyceraldehyde-3-P dehydrogenase (GAPDH) in heterocysts and vegetative cells of 3 N2-fixing cyanobacteria was found to utilize both NAD+ and NADP+. The enzyme activity was enhanced by thiols (glutathione, reduced lipoic acid and dithiothreitol). GAPDH of the 3 cyanobacterial species was not activated by thioredoxin. Heterocysts have now been shown to possess all the enzymes of glycolysis and the tricarboxylic acid cycle to convert glyceraldehyde-3-phosphate (GAP) to oxoglutarate and glutamate. The GAPDH reaction is a major source for the generation of NADH, which is oxidized by a thylakoid-bound NADH:plastoquinone oxidoreductase in heterocysts.

New type of N2-fixing unicellular cyanobacterium (blue-green alga)

New type of N2-fixing unicellular cyanobacterium (blue-green alga)

New type of N2-fixing unicellular cyanobacterium (blue-green alga)

A new N2-fixing unicellular cyanobacterium identified as a Synechococcus sp. was isolated and purified as an axenic culture. It fixed N2 aerobically either under continuous illumination or in alternating light-dark cycle. The N2-fixing properties of the new isolate and Gloeocapsa are discussed.

Chemical composition of cultures and natural samples of N2-fixing blue-green algae from rice fields

Laboratory cultures, soil cultures, and natural samples of N2-fixing blue-green algae (BGA) from rice fields were analyzed for dry matter, ash, N, C, P, and a few other constituents.

The uptake and metabolism of methylamine by N2-fixing cyanobacteria

The cyanobacteria Anabaena variabilis and Nostoc CAN showed a biphasic pattern of 14CH3NH 3 + uptake at external pH values of 7.0 and 9.0. The initial phase of uptake, which was independent of metabolism of 14CH3NH 3 + , was attributed to uptake via a CH3NH 3 + (NH 4 + ) transport system at pH 7.0 and probably to passive diffusion of uncharged CH3NH2 and trapping by protonation at pH 9.0. The second slower phase of uptake was attributed to metabolism of CH3NH 3 + via glutamine synthetase to form γ-methylglutamine which accumulates. Anabaena cylindrica showed an initial rapid uptake at pH 7.0 and pH 9.0 but metabolism of 14CH3NH 3 + was undetectable at pH 7.0 and was barely detectable at pH 9.0. Pretreatment of A. variabilis with l-methionine-d,l-sulphoximine to inactivate glutamine synthetase, inhibited the second phase of 14CH3NH 3 + uptake at both pH 7.0 and pH 9.0 and the accumulation of γ-methylglutamine but had no effect on the first phase of uptake. Following transfer of A. variabilis to darkness the initial phase of 14CH3NH 3 + uptake at pH 7.0 and 9.0 was unaffected but the subsequent metabolism via glutamine synthetase was inhibited.

Stable Carbon and Nitrogen Isotope Tracers of Trophic Dynamics in Natural Populations and Fisheries of the Lahontan Lake System, Nevada

The influence of combined inorganic N on the growth of N2-fixing blue-green algae (Aphanizomenon flos-aquae) in Lahontan Reservoir was detected with N isotopic compositions (δ15N = + 1.2 to + 7.0) that were enriched in 15N. In Pyramid Lake, however, the δ15N of the entire food web was influenced by a contribution of isotopically light N released from N2-fixing blue-green algae (Nodularia spumigena). Carbon isotope ratios (δ13C) of these unpalatable, blue-green algae from both lakes were different enough from the zooplankton and higher animals to preclude a direct trophic link. An enrichment in 13C with trophic level in the food chain was measured in both lakes. Carbon isotope ratio measurements clearly illustrated the isotopic similarity between hatchery-raised Lahontan cutthroat trout (Salmo clarki henshawi) and cui-ui (Chasmistes cujus) and the artificial diet, but differed from the δ13C of their wild counterparts consuming natural foods. There is a consistent isotope fractionation between the δ13C of scales and the δ13C of muscle from fish that is species specific. This finding demonstrates that fish scales, as well as muscle, can be used to determine diet.

Effect of grazer regulation and algal inoculation on photodependent nitrogen fixation in a wetland rice field

A dry season field experiment conducted for two consecutive years highlighted problems of achieving increased populations of N2-fixing blue-green algae (BGA) in wetland rice fields. Inoculation of non-indigenous BGA strains, either dried or as fresh viable inocula even at high levels of application, was unsuccessful. A limiting effect of grazing invertebrate populations on BGA establishment was evident, but other factors were involved. Reducing grazer pressure did not permit establishment of inoculated BGA; interspecific competition and environmental factors may explain the inoculation failure. Grazer regulation permitted the establishment of a fast-growing indigenous N2-fixing Anabaena and the doubling of N2-fixing activity over a control. Neither inoculation nor grazer control affected grain yields significantly.

Identification of facultatively heterotrophic, N2-fixing cyanobacteria able to receive plasmid vectors from Escherichia coli by conjugation.

Plasmid vectors transferable by conjugation from Escherichia coli to obligately photoautotrophic strains of Anabaena spp. are also transferred to and maintained in heterotrophic, filamentous cyanobacteria of the genus Nostoc. These organisms can be used for the genetic analysis of oxygenic photosynthesis, chromatic adaptation, nitrogen fixation, and heterocyst development.

Localization of ribulose 1,5-bisphosphate carboxylase/oxygenase in the N2-fixing cyanobacterium Anabaena cylindrica

Localization of ribulose 1,5-bisphosphate carboxylase/oxygenase in the N2-fixing cyanobacterium Anabaena cylindrica

A culture system enabling in situ determination of net and gross photosynthesis, O2 evolution, N assimilation, and C2H2 reduction in cyanobacteria

A chemostat culture system is described in which measurements of rates associated with carbon and nitrogen assimilation may be made in in situ steady-state cultures of N2-fixing cyanobacteria. Net C and N assimilations were determined from the steady-state cellular carbon and nitrogen contents and the steady-state growth rate of the cultures. O2 evolution in the light and short-term 14C assimilation were measured simultaneously in unperturbed culture cuvettes. 14C assimilation was linear with time through the origin over the 20-min sampling period, thereby providing a measure of gross photosynthesis. C2H2 reduction was measured within the culture cuvette using an open gas analysis system. Steady-state rates of C2H2 reduction were obtained within 10 min and remained constant for up to 1 h. Preliminary results showed that at similar growth rates (0.018–0.019 h−1) cultures grown on [Formula: see text] and N2 contained heterocysts, were smaller, and had higher chlorophyll contents than cells grown on NH3. Corresponding gross photosynthesis was 1.6 to 1.8 times higher than net photosynthesis in [Formula: see text] and N2-grown cells; however, for NH3-grown cells the ratio of gross photosynthesis:net photosynthesis was close to unity. These results are discussed with reference to the energetic costs associated with N assimilation in cyanobacteria.

Advances in Chinese research on Azolla

SynopsisThe aquatic fern Azolla has a symbiotic relationship with an N2-fixing cyanobacterium. Fanners in China and Vietnam have used Azolla for centuries as a green manure for rice and as fodder for pigs, ducks and fish. Chinese researchers have been studying Azolla since the early 1950's but many of their achievements are unknown outside China because of language and other communication problems. This article reviews current Chinese Azolla research and focuses on the impact of newly introduced Azolla species in the areas of field application, use of spores, and isolation of the N2-fixing symbiont.

Potent Mutagenicity of a Bipyridylium Herbicide in a Nitrogen-fixing Blue-green Alga Nostoc muscorum,

The herbicide diquat (1,1′-ethylene-2,2′-bipyridylium ion) has been found to exert a growth inhibitory effect on the N2-fixing blue-green alga Nostoc muscorum in nitrogen-free (N 2 ) and NO 3 - media, without any apparent inhibitory/stimulatory effect on the heterocyst-forming capacity of the organism. With a dose of diquat permitting about 20 and 50% survival of this alga a reverse mutation (from het + nif + auxotrophy to het+ nif+ prototrophy), a forward mutation for L-methionine- DL-sulfoximine (MSO)-resistance, and an auxotrophic mutation for carbon-requirement through methylamine (MA)-resistance, have been obtained. The toxic and mutagenic effects of this agro- chemical have been compared with those of the well known mutagen MNNG (N-methyl-N′-nitro- N-nitrosoguanidine) and found to be stronger than the latter in each case.

Strong mutagenic action of a bipyridylium herbicide in a N2-fixing blue-green alga

The herbicide paraquat (1,1′-dimethyl-4,4-bipyridylium ion) has been found to exert a growth inhibitory effect on the N2-fixing blue-green algaNostoc muscorum in nitrogen-free (N2) and NO 3 − media, without any apparent inhibitory or stimulatory effect on the heterocyst-forming capacity of the organism. With a dose of paraquat permitting about 20 and 50% survival of this alga a reverse mutation (fromhet + nif − auxotrophy tohet + nif + prototrophy), a forward mutation (for L-methionine-DL-sulfoximine [MSO]-resistance), and an auxotrophic mutation (for carbon-auxotrophy through methylamine [MA]-resistance) have been obtained. The toxic and mutagenic effects of this agrochemical have been compared with those of the well known mutagen MNNG (N-methyl-N′-nitro-N-nitrosoguanidine) and found to be stronger than those of the latter in each case.

Inter-strain transfer of a pesticide-resistant marker in the N2-fixing cyanobacterium Nostoc muscorum

Inter-strain transfer of a pesticide-resistant marker in the N2-fixing cyanobacterium Nostoc muscorum

Purification and characterization of thioredoxin from the N2-fixing cyanobacterium Anabaena cylindrica.

Thioredoxin has been purified to homogeneity from the cyanobacterium Anabaena cylindrica. The protein consists of a single polypeptide chain with a relative molecular mass of about 11 680 which has two cysteine residues (residues 31 and 34) in the sequence-Cys-Gly-Pro-Cys- and an isoelectric point at pH 4.55. The N-terminal amino acid sequence of 39 residues shows distinct homologies with the sequences of Escherichia coli and Corynebacterium nephridii thioredoxins. Anti-(A. cylindrica thioredoxin) antiserum was used to quantify the thioredoxin which constituted about 0.22% of the soluble protein in cell-free extracts of N2-fixing, NO3- -grown or NH4+-grown A. cylindrica. Activation of fructose-1,6-bisphosphatase of A. cylindrica, activation of glutamine synthetase and NADP+-dependent malate dehydrogenase of the green alga Scenedesmus obliquus but not of A. cylindrica, and deactivation of glucose-6-P dehydrogenase of the cyanobacterium Anabaena variabilis were all achieved using the same thioredoxin species. No other thioredoxin species were detected in extracts of A. cylindrica when examined for the activation of these enzymes.

Thioredoxin as a Modulator of Glucose-6-phosphate Dehydrogenase in a N2-Fixing Cyanobacterium

Glucose-6-phosphate dehydrogenase (G6PDH) is a key enzyme involved in fixed carbon dissimilation in photosynthetic micro-organisms; in heterocystous cyanobacteria it may also be implicated in the supply of reductant to nitrogenase. In crude cell-free extracts of the N2-fixing cyanobacterium Anabaena variabilis G6PDH activity was reversibly deactivated by the thiol agent dithiothreitol in the presence of a low molecular weight protein (12000mol. wt). Glucose 6-phosphate reversed deactivation when added at high concentration, or prevented deactivation if added with the thiol. NADP+, which, like glucose 6-phosphate, is a G6PDH substrate, also deactivated the enzyme; deactivation was reversed or prevented by adding glucose 6-phosphate or glutamine. Purified thioredoxin from Anabaena cylindrica, at very low concentrations (2 nm), deactivated purified G6PDH in a manner identical to that observed when crude extracts were used in the presence of dithiothreitol. Glutathione did not affect the enzyme.

Glycollate Excretion by N2-fixing Cyanobacteria Treated With Photorespiratory Inhibitors

Summary We have examined the effects of various inhibitors of glycollate metabolism on glycollate excretion, photosynthetic CO2 assimilation and N2 fixation by cyanobacteria. α-HPMS (α-hydroxy-α(2-pyridyl)-methane sulphonate) increased the rate of glycollate excretion by Anabaena cylindrica considerably, but also inhibited net CO2 photoassimilation and N2 fixation. α-HPMS inhibted glycollate dehydrogenase in A. cylindrica extracts but did not affect ribulose bisphosphate carboxylase or phosphoglycollate phosphatase activities. Diamox (5 acetamido-1,3,5-thiadizaole-S-sulphonamide) also stimulated glycollate excretion, inhibited CO2 fixation and caused a low inhibition of N2 fixation. INH (isonicotinic acid hydrazide) enhanced glycollate excretion by A. cylindrica, suggesting the metabolism of glycollate via the glycineserine pathway, but again inhibited CO2 fixation and N2 fixation. Glyoxylate also stimulated glycollate excretion by A. cylindrica, Anabaena variabilis and Nostoc muscorum. The data are discussed in terms of the specificity of glycollate metabolism inhibitors in cyanobacteria and the regulation of glycollate metabolism in these organisms.

Inter-strain transfer of a pesticide-resistant marker in the N2-fixing cyanobacterium Nostoc muscorum

Co-culture of two strains of the cyanobacterium Nostoc muscorum, separately resistant to the pesticide dithane or blitox, results in the appearence of doubly resistant mutants at a frequency some 100 times higher than when the strains are separately cultured. This strongly suggests the occurrence of a gene transfer mechanism for pesticide-resistance in this organism.

Environmental regulation of H2 utilization (3H2 exchange) among natural and laboratory populations of N2 and non-N2 fixing phytoplankton

Regulation of H2 utilization, as monitored by the hydrogenase-mediated(3)H2 exchange reaction, was examined among phytoplankton communitiesin situ and populations in culture. During a 2-year study in the Chowan River, North Carolina, at least 2 major groups of phytoplankton dominated(3)H2 exchange rates. They included N2 fixing cyanobacteria and NO3 (})- utilizing genera. Utilization of(3)H2 by N2 fixers was mainly dark-mediated, whereas(3)H2 utilization associated with periods of NO3 (})- abundance revealed an increasing dependence on light. Inhibitors of N2 fixation (C2H2 and NH4 (+)) negatively affected(3)H2 utilization, substantiating previous findings that close metabolic coupling of both processes exists among N2 fixing cyanobacteria. Conversely, NO3 (})- stimulated(3)H2 utilization among N2 and non-N2 fixing genera, particularly under illuminated conditions. A variety of environmental factors were shown to control(3)H2 exchange. In addition to the nitrogen sources discussed above, dissolved O2, photosynthetically available radiation (PAR), temperature, and pH changes altered(3)H2 exchange rates. It is likely that other factors not addressed here could also affect(3)H2 exchange rates. At least 2 ecological benefits from H2 utilization in natural phytoplankton can be offered. They include the simultaneous generation of adenosine triphosphate (ATP) and consumption of O2 during the oxidation of H2 via an oxyhydrogen or "Knallgas" reaction. Both processes could help sustain phytoplankton, and particularly cyanobacterial, bloom intensity under natural conditions when O2 supersaturation is common in surface waters. H2 utilization appeared to be a general feature of natural and laboratory phytoplankton populations. The magnitudes of(3)H2 utilization rates were directly related to community biomass. Although it can be shown that utilization rates are controlled by specific environmental factors, the potential relationships between H2 utilization and phytoplankton primary production remain poorly understood.