Effect of pesticides on blue-green algae

Summary Effect of pesticides, i.e., Benzene Hexachloride, Lindane, Diazinon and Endrin that are often used in India was observed on nitrogen-fixing blue-green algae Cylindrospermum sp., Aulosira fertilissima Ghose and aerobically non-nitrogen-fixing blue-green alga Plectonema boryanum strain 594. These algae were sensitive for BHC in comparison to other pesticides. A. fertilissima and P. boryanum were more resistant than Cylindrospermum sp.     

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.     

Algal nitrogen fixation on the lava field of Heimaey,Iceland

Summary Nitrogen fixation (C₂H₂ reduction) by blue-green algae occurring on the juvenile lava field of Heimaey, Iceland was examined both in the laboratory (potential at 20° C and 39° C) and in the field, three and a half years after the volcanic eruption.Already at this early stage of colonization representatives of unicellular and filamentous heterocystous and non-heterocystous blue-green algae were commonly observed. The predominating algae were Nostoc sp. (20° C) and Schizothrix sp. — Microcoleus chthonoplastes, (39° C), the former often in association with the protonemata-rhizoids of moss plants.The potential for nitrogen fixation was recorded at an average rate of 109.2 (20° C) and 138.1 (39° C) ng N g^-1 h^-1 in soil collected from localities randomly distributed over the lava field.Tests for nitrogen fixation performed in situ revealed significant fixation activities in all the eleven localities subject to examination. The activities ranged from 2.8 to 63.4 (mean 21.5) ng N g^-1 h^-1 and 1.9 to 17.7 (mean 7.9) ng N cm^-2 h^-1.All the nitrogen fixation data noted imply that blue-green algae contribute a substantial part of the nitrogen input to the lava. Further, it was found that material incubated under micro-aerophilic conditions exhibited considerably enhanced nitrogenase activity.The role of nitrogen-fixing blue-green algae in general and Nostoc muscorum in particular in being suitable as pioneering organisms preparing the bare lava for ingress of other plants is also discussed.     

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.     

Nitrogenase Activity in Relation to Intracellular Organisms in Sphagnum Mosses

Electron microscopic studies of Sphagnum lindbergii (Schimp.) and S. riparium (Ångstr.) have revealed the presence of intracellular organisms such as blue-green algae, green algae, bacteria and fungi. Nitrogenase activities of these Sphagnum mosses were found to be related mainly to the presence of intracellular Nostoc filaments. The appearance of nitrogen-fixing blue-green algae within bryophytes is thus not restricted to liverworts. The association is likely to be of ecological importance as it seems to occur in very acid habitats generally lacking blue-green algae. Possible interrelations between the moss, the blue-green algae and different types of bacteria are discussed.     

EFFECT OF LYSOZYME (MURAMIDASE) ON MARINE AND FRESHWATER BLUE-GREEN ALGAE1

Marine blue-green algae, Lyngbya Lagerheimii, Microcoleus chthonoplastes, Plectonema terebrans, Agmenellum quadruplicatum, and freshwater blue-green algae, Anacystis nidulans, Anabaena variabilis, Nostoc muscorura, and Oscillatoria sp. treated with lysozyme (muramidase) formed spheroplasts but not protoplasts. The time needed for spheroplast induction varied with the species. Approximate internal osmotic pressures of the blue-green algae were determined. Marine algae generally had a higher osmotic pressure than freshwater algae.     

Nitrogen Fixation by Photosynthetic Bacteria in Lowland Rice Culture

Propanil (3′,4′-dichloropropionanilide) was a potent inhibitor of the nitrogenase activity of blue-green algae (cyanobacteria) in flooded soil, but the herbicide at comparable concentrations was not toxic to rice, protozoa, and nitrogen-fixing bacteria. Ethanol-amended flooded soils treated with propanil exhibited higher rates of nitrogenase activity than those not treated with the herbicide. The enhanced nitrogenase activity in propanil-treated soils was associated with a rise in the population of purple sulfur bacteria, especially of cells resembling Chromatium and Thiospirillum. By employing propanil and a means of excluding light from the floodwater to prevent the development of phototrophs during rice growth under lowland conditions, the relative activities of blue-green algae, photosynthetic bacteria, and the rhizosphere microflora were determined. The results suggest that the potential contribution of photosynthetic bacteria may be quite high.     

Nitrogen-fixation associated with the marine blue-green alga,Trichodesmium, as measured by the acetylene-reduction technique

Summary The marine blue-green alga, Trichodesmium, was collected from the Gulf Stream, near Miami, and occurred in two distinct colonial forms both of which reduced acetylene to ethylene. Trichodesmium was more abundant during the summer but its acetylene-reducing potential showed no obvious seasonal variation. Illuminated Trichodesmium reduced acetylene to ethylene equally well either anaerobically or aerobically (20% oxygen). Acetylene-reduction in the dark, however, was oxygen-dependent and was usually 25% or less of the activity recorded in the light. 0.3–1.0 nmoles of ethylene were produced per minute per mg of protein, by illuminated cultures, and these values compare favorably with those recorded for other nitrogen-fixing blue-green algae. However, the possibility that bacteria contributed to the acetylene-reducing activity associated with Trichodesmium was not completely eliminated.Contribution No. 1578 from the University of Miami, Rosenstiel School of Marine and Atmospheric Science, 10 Rickenbacker Causeway, Miami, Florida 33149, U.S.A.     

Nitrogen fixation (acetylene reduction) associated with communities of heterocystous and non-heterocystous blue-green algae in mangrove forests of Sinai

Summary High rates of nitrogen fixation (acetylene reduction) are associated with communities of heterocystous and non-heterocystous blue-green algae, which are widespread and abundant in the coastal mangrove forests of the Sinai Peninsula.Heterocystous forms, particularly representatives of the Rivulariaceae, grow in aerobic environments, where nitrogenase activity may be limited by the availability of nutrients such as Fe and PO₄–P. Desiccated communities of Scytonema sp. reduce acetylene within ten minutes of wetting by tidal sea water. Communities dominated by the non-heterocystous Hydrocoleus sp., Hyella balani, Lyngbya aestuarii, Phormidium sp. and Schizothrix sp., occur in close contact with anaerobic sediments and reduce acetylene in the dark as well as in the light.Nitrogen fixation in all these communities is light dependant and may be supplemented by an alternative source of reductant in the dark. The indications are that nitrogen fixation by these communities of blue-green algae, makes a significant contribution to the overall nitrogen input of the mangrove ecosystem.     

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.     

Nitrogen fixation in lakes

Summary Determinations in the open waters of lakes using N¹⁵ as a tracer show that nitrogen fixation is generally associated with the presence of heterocystous blue-green algae and is light dependent. Although nitrogen-fixing blue-green algae tend to be abundant when the concentration of nitrate or ammonia in the water is low, fixation itself is not necessarily inhibited by the presence of these sources of combined nitrogen. The activity of nitrogen-fixing blue-green algae shows a direct relationship to concentration of dissolved organic nitrogen. As a result of the interaction of such factors, nitrogen fixation per unit area of lake surface per year tends to be greatest at an early stage of eutrophication. In relation to the total nitrogen budget of a lake the contribution of biological nitrogen fixation to the income is probably always small but at certain times and in particular water strata it may contribute a major part of the nitrogen assimilated by the phytoplankton.     

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.     

Host specificity and growth of kelp gametophytes symbiotic with filamentous red algae (Ceramiales,Rhodophyta)

Kelp gametophytes were previously observed in nature living endophytically in red algal cell walls. Here we examine the interactions of two kelp species and six red algae in culture. Gametophytes of Nereocystis luetkeana (Mertens) Postels et Ruprecht became endophytic in the cell walls of Griffithsia pacifica Kylin and Antithamnion defectum Kylin, and grew epiphytically in high abundance on G. japonica Okamura and Aglaothamnion oosumiense Itono. Alaria esculenta (Linnaeus) Greville from the Atlantic coast of Nova Scotia became endophytic in Aglaothamnion oosumiense, Antithamnion defectum, Callithamnion sp., G. japonica, G. pacifica, and Pleonosporium abysicola Gardner, all from the Pacific Ocean. Some cultures were treated with phloroglucinol before infection to thicken the cell walls. The endophytic gametophytes were smaller and grew more slowly than gametophytes epiphytic on the same host. N. luetkeana failed to become endophytic in some of the potential hosts, and this may reflect host specificity, or culture artifacts. This work improves our understanding of the process of infection of red algae by kelp gametophytes, and broadens our knowledge of host specificity in endophytic symbioses.Communicated by K. Lüning     

EVIDENCE FOR THE PRESENCE OF LIGNIN IN MOSS GAMETOPHYTES

Lignin has been established as a constituent of the gametophyte axes in the giant New Zealand mosses Dawsonia sp. and Dendroligotrichum sp. Isolated products comprised ca. 6-10% of the dry weight of gametophyte axes and contained 61-62% C, 6.4-6.8% H, and 5.1-7.9% OCH₃. Characteristic color reaction and ultraviolet spectra were observed, and alkaline nitrobenzene oxidation yielded perhaps 14-18% of mixed aldehydes as their 2,4-dinitrophenylhydrazones. The presence of substantial lignin in these exceptionally tall upright moss gametophytes contrasts strikingly with north temperate species such as Polytrichum, Funaria, Bryum and others, and lends support to the hypothesis that lignification is a mechanically and/or gravitationally regulated process.     

Phosphorus availability and nitrogenase activity in aquatic blue-green algae

Metabolically active phosphorus-starved cultures of blue-green algae assimilate ³²P rapidly in the light and in the dark. The uptake of phosphorus results in a rapid (within 15 min) stimulation in acetylene reduction by Anabaena cylindrica, A. flosaquae, Anabacnopsis circuiaris and Chlorogloea fritschii, with a response being obtained to less than 5 μg/1 of phosphorus. Uptake of phosphorus also causes a rapid increase in respiration in the dark but not in photo respiration, and the size of the cellular ATP pool and the ¹⁴CO₂ fixation rate both increase more slowly. The metabolism of phosphorus-sufficient cells, which assimilate phosphorus more slowly, shows little response when phosphorus is provided. Excess phosphorus is stored in the vegetative cells of blue-green algae as polyphosphate bodies which may form within 60 min of adding phosphorus to phosphorusstarved cells and which serve as a source of phosphorus for the algae when exogenous phosphorus is limiting. Preliminary results from Scottish waters suggest that urban effluents are important sources of available-phosphorus for algal growth and that the levels entering fresh waters from agricultural land are, per unit volume, lower. In both types of water the levels of available-phosphorus are rather similar to the levels of orthophosphate-phosphorus present. Most detergents tested serve as a source of phosphorus for nitrogen-fixing blue-green algae and cause a rapid stimulation in reduction when added to phosphorus-starved cultures. Of the detergents assayed, the biological types were richest in available phosphorus. The addition of detergents may result in a rapid increase in number of polyphosphate bodies present in the algae. Detergents in general also contain an inhibitor of algal metabolism. Whether a stimu-lation or an inhibition occurs depends on the quantities of detergent added and on whether or not the alga is phosphorus-deficient.     

Gametophyte Regeneration and Apospory from Archegoniate Protoplasts Under Conditions Devised for Higher Plants*

Developmental pathways from isolated protoplasts were investigated with the moss Funaria hygrometrica, the liverwort Anthoceros crispulus, and the fern Anogramma leptophylla. Gametophytic protoplasts regenerated gametophytes. Apospory was obtained with sporophytic protoplasts of the moss and the fern. The archegoniates also grew in interdivisional co-cultures with solanaceous species.     

Interaction of respiratory and photosynthetic electron transport in Anabaena variabilis Kütz.

Prelabeled Anabaena variabilis Kütz. evolves ¹⁴CO₂ in the light with KCN and DCMU (2,4-dichlorophenyl-1,1-dimethylurea) present, comparable to the dark control without inhibitors added. Double-reciprocal plots of CO₂ release vs. light intensity with either KCN or KCN+DCMU present result in two straight lines intersecting at the ordinate. Apparently, reducing equivalents originating from carbohydrate catabolism are channeled into the photosynthetic electron-transport chain, competing for electrons from photosystem II. Under these conditions, the CO₂ release is accompanied by a light-dependent oxygen uptake, presumably due to oxygen-reducing photosystem-I activity while ribulose-bisphosphate carboxylase is inhibited by KCN.Comparing nine blue-green algae it was shown that only nitrogen-fixing species release substantial amounts of CO₂ in the light with KCN or KCN+DCMU present. This release is particularly obvious with Anabaena variabilis Kütz. under nitrogen-fixing conditions, but small when the alga is grown with combined nitrogen.We conclude that nitrogen-fixing species share a common link between respiratory and photosynthetic electron transport. The physiological role may be electron supply of nitrogenase by photosystem I.     

Nitrogen Turnover in Marine and Brackish Habitats: I. Nitrogen Fixation

Potential nitrogen-fixing genera were found to be abundant intwo natural populations of blue-green algae, one from a rockycoast and the other from a sand-dune slack. ¹⁵N studies confirmedthat these populations fixed nitrogen in the laboratory andin the field. Preliminary quantitative data on Fixation in thefield suggest that the algae contribute appreciable quantitiesof fixed nitrogen to the environments in which they occur.     

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.     

Nitrogenase activity,amino acid pool patterns and amination in blue-green algae

Summary The free amino acid pools in the nitrogen-fixing blue-green algae Anabaena cylindrica, A. flos-aquae and Westiellopsis prolifica contain a variety of amino acids with aspartic acid, glutamic acid and the amide glutamine being present in much higher concentrations than the others. This pattern is characteristic of that found in organisms having glutamine synthetage/glutamate synthetase [glutamine amide-2-oxoglutarate amino transferase (oxido-reductase)] as an important pathway of ammonia incorporation. Under nitrogen-starved conditions the level of acetylene reduction (nitrogen fixation) and the glutamine pool both increase but the free ammonia pool decreases, suggesting that ammonia rather than glutamine regulates nitrogen fixation.Glutamine synthetase has been demonstrated in Anabaena cylindrica using the -glutamyl transferase assay and also using a biosynthetic assay in which P_i release from ATP during glutamine synthesis was measured. The enzyme (-glutamyl transferase assay) is present in nitrogen-fixing cultures and activity is higher in aerobic than in microaerophilic cultures. Ammonium-grown cultures have lowest levels of all and activity in the presence of nitrate-nitrogen (150 mg nitrogen 1^-1) is lower than in aerobic cultures growing on elemental nitrogen. Ammonium-nitrogen and nitrate-nitrogen have no effect on glutamine synthetase in vitro. Glutamate synthetase also operates in nitrogen-fixing cultures of Anabaena cylindrica.