Cyanobacterial Suspension Research Articles

Toxicity of Diuron, Diquat and Terbutryn to Cyanobacterial Mats

This study investigated acute toxicity of Diuron, Diquat and Terbutryn to cyanobacterial mats collected from Wadi Gaza, Palestine. Toxicity was measured by the reduction of population growth of cyanobacterial mats exposed to various herbicide concentrations in the range of 0-15.44 μmole L-1. Optical density of cyanobacterial suspension was recorded using a spectrophotometer at 680 nm from time zero up to 8 days and taken as an indicator of growth. EC50 and ET50 values were estimated using linear regression equations. Results showed that cyanobacterial mats adapted and grew fast under laboratory conditions. The toxicity of Diuron, Terbutryn and Diquat reached 89.35, 76.02 and 71.24%, respectively. Toxicity of binary mixtures (Diuron and Diquat) decreased from 77.35% to 65.33% due to the reduction of Diuron concentration in the mixture. EC50 values for Diuron, Terbutryn and Diquat were 0.009, 0.031and 0.381 μmole L-1 whereas ET50 values were 32.32, 35.89 and 23.45 h, respectively. EC50 values of binary mixtures (B1-B3) were 0.004, 0.01 and 0.012 toxicity units. Tertiary mixtures (T1-T7) had a wide range of EC50 (0.043-2.9E-07) TUs. The mixture toxicity index (MTI) had positive and negative value in mixtures, indicating synergetic and antagonistic effects. Application of the above-mentioned herbicides may severely damage the ecosystem. Our results are the first of its kind in the region and may be considered as a guideline for future studies.

Enhancement of Essential Oil Production and Expression of Some Menthol Biosynthesis-Related Genes in Mentha piperita Using Cyanobacteria.

Mentha piperita L. is one of the most important aromatic crops and is cultivated worldwide for essential oils (EOs). The aim of the present study was to investigate the potential of two cyanobacteria, Anabaena vaginicola ISB42 and Nostoc spongiaeforme var. tenue ISB65, as biological-elicitors to improve the growth and essential oil production of M. piperita. In this experiment, inoculation of M. piperita with cyanobacteria was performed by adding 1% cyanobacterial suspension to the soil of treated pots on the first time of planting and every 20 days thereafter. The experiment was performed in a randomized complete block design in an experimental greenhouse condition. After 90 days planting, the vegetative growth factors, the content of photosynthetic pigments, as well as the quantity and quality of EOs of treated and control plants were evaluated. Also, quantitative changes in the expression of some menthol biosynthesis-related genes were investigated. Cyanobacterial application led to significant increases in M. piperita growth indices including root and shoot biomass, leaf number, leaf area, node number and ramification, as well as photosynthetic pigments content. The statistical analysis showed a 41-75 % increase in some of these growth indices, especially in Nostoc-treated plants. A. vaginicola and N. spongiaeforme var. tenue inoculation led to a 13% and 25% increase in the EOs content of M. piperita, respectively. The EOs components were also affected by cyanobacterial treatments. According to the statistical analysis, Nostoc-treated plants showed the highest amount of (-)-menthone and (-)-limonene, with a 2.36 and 1.87-fold increase compared to the control. A. vaginicola and N. spongiaeforme var. tenue inoculation also led to 40% and 98% increase in transcript level of (-)-limonene synthase gene, respectively. The expression of the (-)-menthone reductase gene, was also increased by 65% and 55% in response to A. vaginicola and N. spongiaeforme var. tenue application, respectively. Our data demonstrated that in addition to growth enhancement, these two heterocystous cyanobacteria improved the quantity and quality of EOs by up-regulating the key genes involved in the menthol biosynthetic pathway. Based on our results, these cyanobacteria can be considered valuable candidates in the formulation of low-cost and environmentally friendly biofertilizers in sustainable peppermint production.

Intracellular microcystins degradation and acute toxicity decrease towards Daphnia similis by low electron-beam irradiation doses

Ionizing radiation has attracted attention due to its ability to inhibit pathogens and microorganisms, with low doses reported as being able to degrade cyanotoxins and inhibit toxic cyanobacteria growth. In this context, the aim of the present study was to investigate how electron beam irradiation (EBI) applied at doses between 1 and 10 kGy affect intracellular and extracellular microcystin variants. Effects on M. aeruginosa culture recovery, as well as changes in physico-chemical cyanobacterial suspension parameters and water quality alterations were assessed through ecotoxicity assays. The findings indicate that doses over 2 kGy may are lethal to M. aeruginosa even at 48 h post-irradiation. Concerning physico-chemical parameters, exposure to 2–5 kGy doses decrease pH values and later stabilizing. At least 50 % of intracellular MC led to significant degradation of all variants at 3 kGy. No acute toxicity effects were observed in Daphnia similis exposed to sample supernatants. Statistically significant differences were observed when cladocerans were exposed to M. aeruginosa cells treated with EBI doses ranging from 3 to 10 kGy compared to non-treated cyanobacterial suspensions. These findings suggest that low EBI radiation doses are suitable for the control of toxic cyanobacteria in water treatment processes, providing a less toxic environment compared to non-treated solutions.

State of Cyanobacteria <i>Arthrospira platensis</i> and of Associated Microflora during Long-Term Storage in the State of Anhydrobiosis

Abstract—The biochemical composition of Arthrospira (Spirulina) platensis (Nordstedt) Gomont after long-term storage in the state of anhydrobiosis (4 years, 17 years) was determined by the standard methods. It was shown that protein content (55.3–61.2%) and total carbohydrates content (13.0–15.6%) in cyanobacterial cells were in agreement with the data known from the literature and with our results obtained at the onset of storage. The biomass had low content of free nucleotides (1.8–2.6%), lipids (1.3–11.0%), and especially pigments (0.5–1.3, 0.03–0.12, 1.4–2.0, 0.03–0.05% for chlorophyll a, carotenoids, C-phycocyanin, and allophycocyanin, respectively). The content of nucleic acids content was 3.1–24.0 and 0.11–0.16% for RNA and DNA, respectively. Microscopic examination of A. platensis (17 years of storage) showed high numbers of irreversibly damaged and dead cells (34.2 and 65.8%, respectively). To determine the quantitative and morphological parameters of associated microflora, a complex physicochemical treatment (methanol, ultrasound, and centrifugation) of the reactivated cyanobacterial suspension proved the most efficient. Three main groups were distinguished in the morphological structure of the microbiome (rod-shaped, rounded, and convoluted forms). The community was dominated by rod-shaped forms: large and small rods accounted for 60.5 and 14.4%, respectively. Mycelial forms (thin filaments), cocci, and convoluted forms were less common. On average, the volume of a bacterial cell was 0.27 ± 0.04 µm3. The contribution of bacteria to the biomass of A. platensis varied from 3.3 to 11.3% (8.3 ± 4.4% on average) of the dry weight of A. platensis. It has been suggested that the biochemical parameters and viability of cyanobacteria were affected by the accompanying microflora.

A system-oriented strategy to enhance electron production of Synechocystis sp. PCC6803 in bio-photovoltaic devices: experimental and modeling insights

Bio-photovoltaic devices (BPVs) harness photosynthetic organisms to produce bioelectricity in an eco-friendly way. However, their low energy efficiency is still a challenge. A comprehension of metabolic constraints can result in finding strategies for efficiency enhancement. This study presents a systemic approach based on metabolic modeling to design a regulatory defined medium, reducing the intracellular constraints in bioelectricity generation of Synechocystis sp. PCC6803 through the cellular metabolism alteration. The approach identified key reactions that played a critical role in improving electricity generation in Synechocystis sp. PCC6803 by comparing multiple optimal solutions of minimal and maximal NADH generation using two criteria. Regulatory compounds, which controlled the enzyme activity of the key reactions, were obtained from the BRENDA database. The selected compounds were subsequently added to the culture media, and their effect on bioelectricity generation was experimentally assessed. The power density curves for different culture media showed the BPV fed by Synechocystis sp. PCC6803 suspension in BG-11 supplemented with NH4Cl achieved the maximum power density of 148.27 mW m−2. This produced power density was more than 40.5-fold of what was obtained for the BPV fed with cyanobacterial suspension in BG-11. The effect of the activators on BPV performance was also evaluated by comparing their overpotential, maximum produced power density, and biofilm morphology under different conditions. These findings demonstrated the crucial role of cellular metabolism in improving bioelectricity generation in BPVs.

Вплив віброкавітаційного оброблення суспензії ціанобактерій на інтенсивність синтезу біогазу

Досліджено вплив віброкавітаційного оброблення біомаси суспензії ціанобактерій на інтенсивність та ефективність синтезу біогазу внаслідок реалізації в подальшому процесу метаногенезу. Показано актуальність розроблення технології утилізації надлишкової біомаси ціанобактерій, яка утворюється внаслідок їх неконтрольованого розвитку у мілководних ділянках штучних водойм і в технологіях біологічного очищення забруднених поверхневих та стічних вод. Запропоновано використання для руйнування міжклітинних перегородок ціанобактерій та вивільнення їх біомаси, яка стає доступною біорозкладу та реалізації метаногенезу, віброкавітаційного оброблення. Наведено опис конструкції віброкавітатора, який сприяє ефективній руйнації міжклітинних перегородок біомаси ціанобактерій та може працювати у безперервному режимі. Сконструйовано та використано для попереднього оброблення ціанобактерій лабораторну установку віброкавітатора, який працює у періодичному режимі. Створено дослідну установку для дослідження динаміки метаногенезу обробленої у віброкавітаторі біомаси ціанобактерій у безперервному режимі із використанням відеореєстрації синтезу біогазу та передачі даних щодо динаміки синтезу біогазу на монітор. Отримано експериментальні залежності динаміки синтезу біогазу із біомаси ціанобактерій від періоду їх оброблення у віброкавітаційному полі. Встановлено що оптимальні параметри синтезу біогазу досягаються після попереднього оброблення біомаси ціанобактерій у віброкавітаторові впродовж 15 хв. Встановлено автокаталітичний характер процесу, що дає змогу висунути припущення про підпорядкованість його рівнянню Міхаеліса – Ментена. Отриманий після закінчення процесу метаногенезу дигестат запропоновано використовувати як ефективне біоорганічне або органомінеральне (у разі створення композиції із природними дисперсними сорбентами) добриво.

Impact of incubation conditions on protein and C-Phycocyanin recovery from Arthrospira platensis post- pulsed electric field treatment

Pulsed electric field (PEF) was conducted for the extraction of proteins/C-Phycocyanins from Arthrospira platensis. The cyanobacterial suspension was treated with 1 µs long pulses at an electric field strength of 40 kV·cm−1 and a treatment energy of 114 kJ·kgsus−1 and 56 kJ·kgsus−1. For benchmarking, additional biomass was processed by high pressure homogenization. Homogeneity of the suspension prior to PEF-treatment influenced the protein/C-phycocyanin extraction efficiency. Stability of C-Phycocyanin during post-PEF incubation time was affected by incubation temperature and pH of the external medium. Biomass concentration severely affect proteins/C-Phycocyanins extraction yield via PEF-treatment. The optimum conditions for extraction of proteins/C-Phycocyanin was obtained at 23 °C while incubating in pH 8-buffer. The energy demand for PEF-treatment amounts to 0.56 MJ·kgdw−1 when processing biomass at 100 gdw·kgsus−1. PEF treatment enhances the protein/C-Phycocyanin extraction yield, thus, it can be suggested as preferential downstream processing method for the production of C-Phycocyanin from A. platensis biomass.

Effect of chlorine dioxide on cyanobacterial cell integrity, toxin degradation and disinfection by-product formation

Bench scale tests were conducted to study the effect of chlorine dioxide (ClO2) oxidation on cell integrity, toxin degradation and disinfection by-product formation of Microcystis aeruginosa. The simulated cyanobacterial suspension was prepared at a concentration of 1.0×106cells/mL and the cell integrity was measured with flow cytometry. Results indicated that ClO2 can inhibit the photosynthetic capacity of M. aeruginosa cells and almost no integral cells were left after oxidation at a ClO2 dose of 1.0mg/L. The total toxin was degraded more rapidly with the ClO2 dosage increasing from 0.1mg/L to 1.0mg/L. Moreover, the damage on cell structure after oxidation resulted in released intracellular organic matter, which contributed to the formation of trihalomethanes (THMs) and haloacetic acids (HAAs) as disinfection by-products. Therefore, the use of ClO2 as an oxidant for treating algal-rich water should be carefully considered.

Coupling the microbial food web with fish: are bacteria attached to cyanobacteria an important food source for underyearling roach?

1. After observing that juvenile roach fed intensively on cyanobacteria and that cyanobacteria were densely colonized by heterotrophic bacteria, we tested whether the bacteria are used by underyearling roach and the extent to which they contribute to the energy requirements of the fish.2. We radiolabelled attached bacteria in a natural cyanobacterial suspension, fed the fish with these particles, and estimated their assimilation by roach. Biomass of attached bacteria on cyanobacteria increased with the proportion of the cyanobacterium Microcystis in total cyanobacteria. Biomass‐specific thymidine incorporation of attached bacteria was higher than that of free bacteria.3. In feeding experiments, we detected assimilation of bacterial biomass into muscle tissue of underyearling roach. Fish consumed Microcystis to a lesser extent compared with Aphanizomenon but assimilation of attached bacteria was higher when roach fed on Microcystis because of the higher biomass of epibacteria on this cyanobacterium. However, biomass of attached bacteria was too low to be an important food source for underyearling roach.4. We conclude that assimilation of epibacteria from cyanobacteria cannot explain the success of roach in eutrophic lakes.

Glycolaldehyde inhibition of CO2 transport in the cyanobacterium Synechococcus UTEX 625

In studies of the inorganic carbon (Ci) concentrating mechanism of cyanobacteria glycolaldehyde is often used to inhibit photosynthetic CO2 fixation. As a partial inhibition of active CO2 transport by glycolaldehyde under steady-state Ci flux conditions has been recently suggested, in this paper, using mass spectrometry, we investigate in detail the relationship between glycolaldehyde concentration ((GLY)) and CO2 transport both during the initial period following illumination of a cyanobacterial cell suspension and during the so-called steady state when an internal Ci pool has been allowed to develop. Carbon dioxide uptake following illumination of a cyanobacterial cell suspension was progressively reduced by increasing (GLY) in the medium, both in the absence or in the presence of carbonic anhydrase. The same features were found when either Ci in the form of bicarbonate was injected to a pre-illuminated cell suspension in the presence of carbonic anhydrase in the medium or a pulse of CO2 was provided to the cells in the light without carbonic anhydrase in the extracellular medium. Although photosynthesis was completely abolished with 10 mM glycolaldehyde, CO2 uptake was only inhibited 20% but was decreased further by higher (GLY). Double reciprocal plots of CO2 uptake versus initial (CO2) determined with a range of (GLY) showed the inhibition to be noncompetitive. To simultaneously study CO2 uptake and CO2 efflux, H 13 C 18 O3 was used with cells in which CO2 transport alone, or both CO2 and HCO3 n transport system were allowed to proceed. Cells were inhibited with either iodoacetamide or glycolaldehyde and the time course of the various CO2 species in the medium demonstrated that CO2 uptake was inhibited partially with glycolaldehyde resulting in a greater CO2 efflux from the cells. When the cell suspension was again illuminated, in the presence of glycolaldehyde, initial CO2 uptake was greatly reduced, and the extracellular (CO2) eventually rose to a level higher than that which would be expected to be in equilibrium with the amount of Ci present in the medium. Results are discussed in terms of glycolaldehyde use in Ci transport mechanism studies in cyanobacteria.

Glycolaldehyde inhibition of CO2transport in the cyanobacteriumSynechococcusUTEX 625

In studies of the inorganic carbon (Ci) concentrating mechanism of cyanobacteria glycolaldehyde is often used to inhibit photosynthetic CO2fixation. As a partial inhibition of active CO2transport by glycolaldehyde under steady-state Ciflux conditions has been recently suggested, in this paper, using mass spectrometry, we investigate in detail the relationship between glycolaldehyde concentration ([GLY]) and CO2transport both during the initial period following illumination of a cyanobacterial cell suspension and during the so-called steady state when an internal Cipool has been allowed to develop. Carbon dioxide uptake following illumination of a cyanobacterial cell suspension was progressively reduced by increasing [GLY] in the medium, both in the absence or in the presence of carbonic anhydrase. The same features were found when either Ciin the form of bicarbonate was injected to a pre-illuminated cell suspension in the presence of carbonic anhydrase in the medium or a pulse of CO2was provided to the cells in the light without carbonic anhydrase in the extracellular medium. Although photosynthesis was completely abolished with 10 mM glycolaldehyde, CO2uptake was only inhibited 20% but was decreased further by higher [GLY]. Double reciprocal plots of CO2uptake versus initial [CO2] determined with a range of [GLY] showed the inhibition to be noncompetitive. To simultaneously study CO2uptake and CO2efflux, H13C18O3was used with cells in which CO2transport alone, or both CO2and HCO3-transport system were allowed to proceed. Cells were inhibited with either iodoacetamide or glycolaldehyde and the time course of the various CO2species in the medium demonstrated that CO2uptake was inhibited partially with glycolaldehyde resulting in a greater CO2efflux from the cells. When the cell suspension was again illuminated, in the presence of glycolaldehyde, initial CO2uptake was greatly reduced, and the extracellular [CO2] eventually rose to a level higher than that which would be expected to be in equilibrium with the amount of Cipresent in the medium. Results are discussed in terms of glycolaldehyde use in Citransport mechanism studies in cyanobacteria. Key words: Synechococcus UTEX 625, blue-green algae, cyanobacteria, CO2transport, HCO3-transport, CO2efflux, inhibitor, Ciconcentrating mechanism.

Vertical thin-layer photoreactor for controlled cultivation of cyanobacteria

Nostoc sp. was cultivated in an air-lift reactor with continuous recirculation of the head gas phase that aerated and agitated the cyanobacterial suspension at regulated flow rates. The supply of inorganic carbon for growth was coupled with pH control, in the range of 7.7 to 8.1, by intermittent sparging of CO2-head gas mixtures. The formation of irregular bubbles with swirling motion at the photostage of the reactor promoted efficient CO2 transference in dense populations of Nostoc sp. (1.1 g/l) when bubbling at flow rates of 10 l/min. Biomass productivity was almost six-fold higher in the photoreactor (16.4 mg/l.h) than in a conventional system (2.8 mg/l.h). The exponential growth phase of cultures in the photoreactor amounted to 60% of the total growth period.

Measurements of oxygen production rate in flowing Spirulina suspension

The oxygen production rates for a cyanobacterial suspension flowing in straight and coiled tubes were measured to find a way of achieving higher efficiency of light utilization by means of convective mixing. The photosynthetic flow chambers were made of glass tubes and illumination was by fluorescent light. The cyanobacterium used was Spirulina platensis, which has a high growth rate. The oxygen production rate for fluid flow in straight and coiled tubes increase with the increase in Reynolds number. The maximum oxygen production rate was achieved at 30°C for both tube reactors, but the oxygen production rate was higher for the coiled tube unit than the straight tube unit at 30°C. Thus the convective mixing generated in the coiled tube reactor contributed to an increased in light utilization, which played an important part in improving the oxygen production rate.

Photooxidation of cyanobacteria in natural conditions.

Photodynamic effects were demonstrated and assayed under field conditions in a number of different laboratory strains and pond isolates of cyanobacteria; parameters assayed for resistance to photooxidation were viable count, turbidity of the cyanobacterial suspension, and protein and pigment contents. The effects of density, colonial structure, and internal gas vacuoles on the lethal outcome were investigated. The stability and formation of superoxide dismutase under photooxidative conditions in the field and laboratory were studied in the different strains. An isolate of Microcystis from blooms in ponds exhibited extremely high resistance to photooxidation, which was abolished by exposure to chloramphenicol.