Effects of light, temperature, nitrate, orthophosphate, and bacteria on growth of and hepatotoxin production by Oscillatoria agardhii strains

The effects of bacteria, temperature, light, nitrate, and orthophosphate on growth of and hepatotoxin (desmethyl-3-microcystin-RR) production by Oscillatoria agardhii strains were studied under laboratory conditions. Strains were cultivated in Z8 medium under continuous illumination. Growth was determined by measuring dry weight and chlorophyll a, while toxin was analyzed by high-performance liquid chromatography. Two of the three toxic cultures studied produced more toxins in axenic than in nonaxenic cultures. High toxin production correlated with high nitrogen concentrations (test range, 0.42 to 84 mg of N per liter) and low light intensity (test range, 12 to 95 microeinsteins/m2 per s). Toxin production depended on phosphorus concentration at low levels of phosphorus (0.1 to 0.4 mg of P per liter) and higher concentrations had no additional effect. The optimum temperature for toxin production and growth of green O. agardhii was 25 degrees C. Red O. agardhii produced almost similar amounts of toxin at temperatures of 15 to 25 degrees C. The lowest toxin production by both strains was at 30 degrees C.     

Effects of light on nitrate-limited Oscillatoria agardhii in chemostat cultures

The effects of the average light irradiance (I) on growth and nitrate uptake kinetics of the cyanobacterium Oscillatoria agardhii, in nitrate-limited chemostat cultures, were studied. Light was nonsaturating for I <9.4 Wm^–2, for all growth rates () studied. However, was throughout limited by the availability of nitrate. Under light-saturating conditions the kinetics of nitrate-limited growth could be adequately described by both the Monod and Droop equations. Under light-non-saturating conditions the internal nitrogen content (Q) was a function of both and I, for which new formulas were derived. The high uptake capacity (V _max) of nitrate-limited cells was independent of , but was significantly increased for cells growing at I <9.4 Wm^–2. The half-saturation constant for nitrate uptake (K _s ^u ) increased with increasing , but was independent of the prevailing light conditions. The effects of light during nitrate-limited growth were associated with the regulation in the nitrogen-containing pigments.The results reported herein have important consequences for the use of Q, K _s ^u and V _max values as indicators of nutrient-deficiency of natural populations.     

Effects of photoperiodicity and light irradiance on phosphate-limited Oscillatoria agardhii in chemostat cultures

Oscillatoria sp. strain 23 is a filamentous, non-heterocystous cyanobacterium that fixes nitrogen aerobically. Although, in this organism nitrogenase is inactivated by oxygen a high tolerance is observed. Up to a pO₂ of 0.15 atm, oxygen does not have any measurable effects on acetylene reduction. Higher concentrations of oxygen inhibited the activity to a relatively high degree. Evidence for two mechanisms of oxygen protection of nitrogenase in this cyanobacterium was obtained. A high rate of synthesis of nitrogenase may allow the organism to maintain a certain amount of active enzyme under aerobic conditions. Secondly, a switch off/on mechanism may reversibly convert the active enzyme into a non-active form which is insensitive to oxygen inactivation after a sudden and short-term exposure to high oxygen concentrations. It is conceived that these mechanisms in addition to a temporal separation of nitrogen fixation from oxygenic photosynthesis sufficiently explain the regulation process of aerobic nitrogen fixation in this organism.Abbreviations DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - CAP chloramphenicol     

Effects of photoperiodicity and light irradiance on phosphate-limited Oscillatoria agardhii in chemostat cultures

The cyanobacterium Oscillatoria agardhii was grown in continuous culture under various light conditions in order to study the interactions of light on phosphorus-limited growth. Under severe P-limiting (light-saturating) conditions, a low chlorophyll a and C-phycocyanin content was found. In addition, the light-harvesting capacity, reflected in the values of P _max (maximum light-saturated oxygen production rate) and (photosynthetic affinity), were low compared to light-limited cultures.Reduction of the light climate, either by reduction of the length of the photoperiod or light-intensity, resulted in an increase in light-harvesting capacity (higher pigment content, P _m and ) during growth under P-limiting conditions. Light-induced changes in P _max and could be related to the relative growth rate, being the actual growth rate as a fraction of the growth rate which would be observed under light-limiting conditions.Under P-limiting conditions, reduction of the light-climate caused a reduction in dry weight of the culture. This decrease was mainly due to a decrease in carbohydrate content of the cells. Under all conditions tested, carbohydrates were found to accumulate during the light-period and to be consumed during the dark-period.Evaluation of carbohydrate consumption in the dark yielded a specific maintenance rate constant of 0.001 h^-1. This observation leads to the conclusion that the specific maintenance rate constant is independent on the character of the growth rate limiting nutrient for O. agardhii.     

Regulation of growth and photosynthesis by Oscillatoria agardhii grown with a light/dark cycle

Abstract The cyanobacterium Oscillatoria agardhii was grown in turbidostat cultures with the light energy supply in either the continuous mode or in the pulsed mode (8/16 h light/dark (L/D) cycle). The light irradiance value used was sufficient to allow the maximal growth rate to be attained, when supplied continuously. Adaptation of O. agardhii to the L/D cycle was characterized by an increase in pigment content and photosynthetic performance, accompanied by a decrease in growth rate. This mode of adaptation resembled the adaptation of O. agardhii to continuous low light intensities. It is suggested that in this case the L/D cycle provokes this adaptation in order to allow the cells to accumulate carbohydrate rapidly during the light period. This was attributed to the storage of polyglucose, which served as a carbon and energy source for growth in the dark. The utilization of polyglucose in the dark was able to sustain the synthesis of all other cell components at the same rate as when cells were growing in the light. The growth yield in the dark, whilst metabolizing internally stored polyglucose, was 0.52 g cell C/g polyglucose C, or 0.62 g cell dry weight/g polyglucose. Although in the pulsed mode there is a 66% loss in light irradiance per 24 h when compared with a continuous light regime, the growth rate of the cyanobacteria grown in the pulsed mode was only 35% lower than the growth rate of a culture grown in continuous light. This can be explained by a high growth yield in the dark and by increased CO₂ fixation rates in the light of cells grown in the pulsed mode.     

Ammonium-limited growth and uptake by Oscillatoria agardhii in chemostat cultures

Growth of Oscillatoria agardhil was studied in ammonium-limited chemostat cultures, at various dilution rates (=growth rates, μ). The uptake kinetics for ammonium of nitrogen (ammonium or nitrate)-limited chemostat cultures also was investigated. The kinetics of ammonium-limited growth could be adequately described by both the Monod and Droop equations, and were closely similar to the nitrate-limited growth kinetics of this species. The uptake kinetics for ammonium showed similarities as well as differences with the uptake kinetics for nitrate. The similarities were apparent in the uptake capacity values for ammonium and nitrate , which were identical, high and independent of μ. The differences were to be found in the half-saturation constants for ammonium uptake and nitrate uptake , the former being hardly influenced by μ. A consitutive, high affinity, system is likely to operate in the uptake and assimilation of ammonium by nitrogen-limited O. agardhii. The use of ammonium uptake parameters in studies of growth-limiting factors in nature can provide information as to whether a nitrogen-limitation prevails in natural habitats of this species.     

Effects of macronutrients upon buoyancy regulation by metalimnetic Oscillatoria agardhii in Deming Lake, Minnesota

Gas-vacuolate filaments of Oscillatoria agardhii form a metalimneticlayer in Oeming Lake, Minnesota. The environmental factors whichaffect buoyancy and the physiological processes which mediatechanges in buoyancy were determined. Buoyant filaments losttheir buoyancy in a few hours when incubated at light intensitiesabove those found in situ ({small tilde}15 µnol photonsm^–2 s^–1, or 1% of the surface value). The rate ofbuoyancy loss was accelerated by the addition of 10 µMphosphate at irradiances >200mol photons m^–2 s^–1.The effect of nutrient additions on buoyancy was also investigatedover a longer time period by incubating metalimnetic samplesin situ. The samples were deployed for 6 days at a depth wherethe irradiance was 8% of the surface value. As found in short-termexperiments, the addition of phosphate resulted in the largestdecrease in buoyancy. However, the addition of ammonia in additionto phosphate attenuated the buoyancy loss on day 2, and on day6 the filaments in these treatments were almost completely buoyant.The physiological status of the filaments in these treatmentswas assayed by analysis of elemental ratios of C, N and P, andby measurement of cellular chlorophyll, polysaccharide and protein.In addition, the cellular content of gas vesicles was determined.The construction of ballast balance sheets from these data indicatedthat changes in buoyancy were primarily due to differences inthe amount of polysaccharide ballast in the cells. However,in another set of in situ experiments, the increase in measuredballast molecules did not explain the observed loss of buoyancy.We hypothesized that another, undetected ballast-providing moleculehad accumulated in the cells.     

In situ primary production,biomass and light regime in the Wolderwijd,the most stable Oscillatoria agardhii lake in The Netherlands

During the entire period of research from 1971 to 1982 Oscillatoria agardhii Gomont was overwhelmingly present in the Wolderwijd. Six years of measurements of primary production has pointed out that the gross production per day firstly is related to temperature and secondly to irradiation. However, the production per year is neither related to temperature nor to irradiation. In a cold summer gross production is as high as in a warm summer due to higher production in the lower part of the euphotic zone.In the discussion attention is focused on production characteristics and light climate in relation to the morphometry of the lake. Up to an average depth of 2.5 m blooming of O. agardhii occurs easily, whilst light saturated production achieves its maximum between 2.0 and 2.5 m depth. Increasing depth leads to photo-inhibition in the upper layers followed by lowering of light saturated production. Only special circumstances such as days with microstratification allow growth, resulting then in a monoculture of the alga.     

Isolation and identification of eight microcystins from thirteen Oscillatoria agardhii strains and structure of a new microcystin.

Microcystins (cyclic heptapeptide hepatotoxins), isolated from 13 freshwater Oscillatoria agardhii strains from eight different Finnish lakes by high-performance liquid chromatography, were characterized by amino acid analysis, fast atom bombardment mass spectrometry (FABMS), and tandem FABMS (FABMS/collisionary-induced dissociation/MS). All strains produced two to five different microcystins. In total, eight different compounds, of which five were known microcystins, were isolated. The known compounds identified were [D-Asp3]MCYST (microcystin)-LR, [Dha7]MCYST-LR, [D-Asp3]MCYST-RR, [Dha7]MCYST-RR, and [D-Asp3,Dha7]MCYST-RR. This is the first time that isolation of these toxins from Oscillatoria spp., with the exception of [D-Asp3]MCYST-RR, has been reported. Three of the strains produced a new microcystin, and the structure was assigned as [D-Asp3,Mser7]MCYST-RR. The structures of two new microcystins, produced as minor components by one Oscillatoria strain, could not be determined because of the small amounts isolated from the cells. Four strains produced [Dha7]MCYST-RR as the main toxin, but [D-Asp3]MCYST-RR was clearly the most abundant and most frequently occurring toxin among these isolates of O. agardhii.     

Aspects of nitrogen fixation in Lough Neagh. II. Competition between Aphanizomenon flos-aquae, Oscillatoria redekei and Oscillatoria agardhii

SUMMARY.

• 1 The effect of nutrient availability on the growth of natural samples of Lough Neagh plankton (Aphanizomenon flos-aquae, initial innoculum 0.98 mm³ l^-1, Oscillatoria redekei, 2.52 mm³ l^-1 and Oscillatoria agardhii, 4.96 mm³ l^-1) was studied, using ecologically realistic conditions of temperature (15°C), nitrate-N (<0.35g m^-3) and orthophosphate-P (<0.55g m^-3), in which the combinations –N–P, –N+P, +N–P, and +N+P were used.
• 2 After 8 days A. flos-aquae had become dominant in treatments lacking N. After 12 days with N available the mean yields of O. redekei (37.7 mm³ l^-1) and O. agardhii (10.82 mm³ l^-1) were significantly greater (P=5%) than their respective yields (3.6 and 2.6 mm³ l^-1) in the absence of N. Somewhat surprisingly the mean yield of A. flos-aquae when N was present (0.15 mm³ l^-1), was significantly less (P=5%) than in the absence of N (13.26 mm³l^-1).
• 3 The relative rates and duration of growth, the availability of P and N, and heterocyst frequency as an index of nitrogen fixation are considered in relation to the seasonal succession and dominance of these three principal cyanophyte members of the Lough Neagh phytoplankton.

     

Allelopathic activity of Spirogyra sp.: stimulating bloom formation and toxin production by Oscillatoria agardhii in some irrigation canals, Egypt

It has often been observed that irrigation canals in Egypt thatcontain Spirogyra are covered with blooms of Oscillatoria duringthe summer season. These blooms do not occur in the canals notcontaining Spirogyra. Thus, two irrigation canals, one containingSpirogyra and another not containing Spirogyra, were chosento study the possible allelopathic activity of Spirogyra onthe growth of Oscillatoria agardhii. The growth of O. agardhiiand other associated cyanobacterial species was followed inthese two canals during the period May–September 2000.The results revealed that O. agardhii was dominant and formedblooms in the canals containing Spirogyra, while it had a moderate/rareoccurrence in those not containing Spirogyra. To confirm thestimulatory allelopathic activity of this green alga on thegrowth of and microcystin production by O. agardhii, a laboratoryexperiment was run by growing O. agardhii with different concentrationsof Spirogyra aqueous extract. The results showed that the growthof and microcystin production by O. agardhii increased withincreasing concentrations of Spirogyra aqueous extract. Thisfinding demonstrates the allelopathic activity of the greenalga Spirogyra stimulating the growth of and toxin productionby O. agardhii. Such a biotic factor should be taken into considerationwhen cyanobacterial blooms are monitored in freshwater bodies.     

Effects of temperature on orthophosphate absorption by excised corn roots

The uptake of orthophosphate (³²P) by excised corn roots, Zea mays L. was studied using roots grown on 0.2 mm CaSO₄. Nine concentrations of KH₂PO₄ from 1 to 256 μm were used at temperatures of 20°, 30°, and 40°. Enzyme kinetic analysis was applied to the data obtained. Two apparent mechanisms (sites) of phosphate uptake were observed, 1 dominating at high P concentrations and 1 at low P concentrations. A Km of 1.36 × 10⁻⁴ and a Vmax of 177 × 10⁻⁹ moles per gram of roots per hour at 30° was calculated for the mechanism dominating at high P concentrations. Similar calculations gave a Km of 6.09 × 10⁻⁶ and a Vmax of 162 × 10⁻⁹ moles per gram of roots per hour at 30° for the mechanism dominating at low P concentrations. The Q₁₀ for both mechanisms was approximately 2. Calculation of thermodynamic values from the data gave ΔF of − 5200 cal, ΔH of − 950 to − 1400 cal, and a enthalpy of activation (A) of 10,300 to 13,800 cal per mole for the mechanism dominating at high P concentrations. Similar calculations from the data for the mechanism dominating at low P concentrations gave a ΔF of − 7300 cal, ΔH of − 10,700 to − 8200 cal, and a A of 9300 to 18,900 cal per mole. If the dual mechanism interpretation of this kind of data adequately describes this system, then both mechanisms of P absorption by corn roots involve chemical reactions.     

Effects of temperature, light, nitrate and pre chilling on seed germination of grassland plants

The effects of factorial combinations of alternating (20/10 ^oC) and constant temperature (20 ^oC), of light (intermittent) and dark, and of distilled water and nitrate on the germination of a range of species of indigenous grassland were investigated in 1979, and in 1980 when the effects of pre-chilling were also studied. Species differed greatly in their response to the eight sets of environmental conditions in 1979. With the exception of Lolium perenne ssp. perenne and Cynosurus cristatus, only a small percentage of seeds of most species was able to germinate in constant temperature in the dark. However, when light was supplied there was moderate germination of Anthoxanthum odoratum, Cerastium fontanum ssp. glabrescens, Festuca rubra, Holcus lanatus and Poa trivialis. Alternating temperature greatly increased the germination of most species and nitrate further increased germination of Agrostis capillaris, Deschampsia caespitosa, H. lanatus, Poa annua and P. trivialis. In alternating temperatures, light increased germination of these species even more than did nitrate. A. capillaris, D. caespitosa and P. annua required all three factors for maximum germination, and another 7% of seeds of A. capillaris also required gibberellic acid. Germination responses following sequential application of factors often differed from those resulting from simultaneous treatment: in particular, the germination of Ranunculus species was greatly enhanced. Although seeds of the species tested in 1980 were more germinable than those of the same species in 1979, they responded similarly to the different factors. Light increased the germination of both Taraxacum officinale and Plantago lanceolata in constant but not in alternating temperature, while nitrate was much more stimulatory to the latter species. About half the seeds of P. lanceolata were dormant. Pre-chilling at 4^oC for 7 days increased subsequent germination of all species when followed by constant temperature, except of A. capillaris in the dark and C. cristatus (already maximal) in the light. When followed by alternating temperature in the dark, pre-chilling greatly decreased germination of A. capillaris. In the light, where germination of most species was maximal, there was little effect of pre-chilling. Longer durations (21 and 42 days) of chilling of older seed gave similar results to the 7 day pre-chilling.     

Purification and characterization of a novel lectin from a freshwater cyanobacterium, Oscillatoria agardhii

In the survey of 14 species of laboratory-cultured cyanobacteria for hemagglutinins, we newly detected the activity in two species, Oscillatoria agardhii, strain NIES-204, and Phormidium foveolarum, strain NIES-503. From the extract of O. agardhii, which showed the highest activity with trypsin-treated erythrocytes of rabbit, a lectin was purified to homogeneity by the combination of precipitation with (NH4)2SO4, gel filtration, hydrophobic chromatography and reverse phase chromatography. The purified lectin, designated OAA, was a monomeric protein with an apparent molecular weight of 13,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 16,000 on gel filtration. The amino acid composition was rich in glycine and acidic amino acids. The hemagglutination activity was inhibited by glycoproteins such as yeast mannan, but not by any of the monosaccharides tested. The activity was stable over a wide range of pH (4-11) and at a high temperature of 80 degrees C, and independent on the presence of divalent cations. The features of OAA resembled those of many of lectins from marine macroalgae. The sequence of amino-terminal residues of OAA was determined as ALYNVENQWGGSSAPWNEGG, which was highly homologous to those of lectins from macroalgae of the genus Eucheuma and that of a myxobacterium Myxococcus xanthus hemagglutinin.     

The effect of temperature and light intensity on hydrogen gas production by different Rhodopseudomonas capsulata strains

Summary Six strains of Rhodopseudomonas capsulata were tested for their ability for anaerobic light-dependent hydrogen gas production from acetate in different incubation temperatures and light intensities.Certain strains show a higher efficiency of acetate conversion to H₂ at higher temperatures and higher light intensities, others on the other hand are insensitive or even show the opposite effect.     

Ecophysiological studies on Spirulina platensis Effect of temperature,light intensity and nitrate concentration on growth and ultrastructure

The ultrastructure of the cyanobacterium Spirulina platensis was studied in relation to temperature, light intensity and nitrate concentration. The organism was able to grow in media supplied with nitrate in concentrations up to 250mm. High nitrate concentrations increased the yield and growth rate at temperatures above 35°C. Occurrence, distribution and abundance of cyanophycin granules, polyglucan granules, cylindrical bodies, carboxysomes and mesosomes varied widely in relation to the factors studied. At low temperatures (up to 17°C) cyanophycin was the abundant organelle, especially at high nitrate concentrations, whereas in the temperature range 17–20°C polyglucan was found in large quantities particularly at low nitrate concentrations. Special attention was paid to the cylindrical bodies, the ultrastructure of which was dependent on temperature. Three types of ultrastructure were distinguished each with several possible shapes.     

Effects of nitrate,ammonium and pH on the growth of conifer seedlings and their production of nitrate reductase

Summary Lodgepole pine (Pinus contorta Dougl.), Engelmann spruce (Picea engelmanni Parry), and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were grown in open-ended tube cultures of sand and perlite, irrigated with nitrate, ammonium, and a 1∶1 mixture of ammonium and nitrate, combined factorially with pH values of 4.6, 5.3 and 6.0 giving a total of nine treatments. Douglas-fir showed intolerance to ammonium which was especially marked in root weight. Lodgepole pine and Engelmann spruce made poor growth with nitrate, but showed little difference between ammonium and mixed sources. Only Douglas-fir showed a significant response to pH treatments with pH 5.3 plants being largest. Contamination of the sand with carbonate-bicarbonate, apparently caused seedlings grown in ammonium solutions to be larger in sand than in perlite. Douglas-fir grown in perlite cultures showed a growth response like the first experiment and nitrate reductase activity in the order nitrate > nitrateammonium mixture > ammonium. Plastic bead cultures had poor growth response due to low retention of water by the substrate, but the nitrate reductase assays produced results like the perlite cultures. Lodgepole pine grown in water culture demonstrated the well known pH shift associated with different nitrogen forms, and when assayed for nitrate reductase these seedlings had larger relative activities than Douglas-fir, but the order of activity remained nitrate > mixed source > ammonium.     

温度、盐度、光照对蜈蚣藻丝状体生长的影响

为了研究蜈蚣藻丝状体在不同的盐度、温度、光照强度和光照周期下的生长特征,分别观察比较了5个盐度(18~46)、5个温度(10℃~30℃)、6个光照强度(500 lx~5500 lx)和6个光照周期(0L∶24D-24L∶0D)培养条件下蜈蚣藻丝状体增重量的变化。结果表明:温度实验中以20℃条件下,蜈蚣藻丝状体的相对增重率最大,为124.8%;盐度实验中以32盐度下,蜈蚣藻丝状体的相对增重率最高,为68.3%;光照强度以2500 lx条件为最佳,蜈蚣藻丝状体的相对增重率最高,为88.2%;光照周期以24L∶0D全光照条件下生长最快,蜈蚣藻丝状体的相对增重率达到197.3%。由此可见,在温度为20℃,盐度为32,光照强度为2500 lx,24 h光照的条件下,蜈蚣藻丝状体长势最好,是培育蜈蚣藻的最佳条件。