Effect of iron and phosphorus on the microalgae growth in co-culture.

Iron and phosphorus (P) are the important micro- and macro-nutrient for microalgae growth, respectively. However, the effect of iron and P on microalgae growth in co-culture associating with the formation of dominate algae has not been investigated before. In the current study, Anabaene flos-aquae, Chlorella vulgaris and Melosira sp. were co-cultivated under the addition of different initial iron and P to reveal the effect of iron and phosphorus on the growth of microalgae. The results showed that the mean growth rate of A. flos-aquae, C. vulgaris and Melosira was 0.270, 0.261 and 0.062, respectively, indicating that the A. flos-aquae and C. vulgaris algae are liable to be the dominant algae while the growth of Melosira was restrained when co-cultured. The ratio of Fe to P has a significant impact on the growth of microalgae and could be regarded as an indicator of algae growth. Microalgae showed a much more obvious uptake of iron compared to that of P. The information obtained in the current study was useful for the forecast of water quality and the control of microalgae bloom.

Using stable isotope labeling to study the nitrogen metabolism in Anabaena flos-aquae growth and anatoxin biosynthesis.

Freshwater resources are under stress around the world due to rapid urbanization and excessive water consumption. Cyanobacterial blooms have occurred frequently in surface waters, which produced toxic secondary metabolites causing a potential harm to aquatic ecosystems and humans. In this study, the relationship between different types of nitrogen source and the algal growth of Anabaena flos-aquae, which was isolated from Dianchi Lake in southern China, was investigated. Experiments were accomplished by using four types of isotope tracers including 15N-ammonium chloride, 15N-sodium nitrate, 15N-urea, 15N-l-alanine in culture medium to characterize the biosynthesis of 15N-anatoxin-a (ATX-A), which is a major algal toxin from A. flos-aquae, through liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results showed that all these four types of nitrogen can be incorporated into algal cells. The ATX-A production with urea as the nitrogen source was much higher than that with the other three types of nitrogen. The 15N labeling experiments further demonstrated that the uptake of organic nitrogen nutrients was significantly greater than that of inorganic nitrogen. These results provide new evidence and deeper insight to explore the biosynthesis of ATX-A in the specific strain of A. flos-aquae.

Allelopathic Effects of Myriophyllum aquaticum on Two Cyanobacteria of Anabaena flos-aquae and Microcystis aeruginosa.

Allelopathy has been proposed as a sustainable means to control undesired algal growth and to reduce blooms threatening freshwater systems worldwide. In this study, the allelopathic effects of Myriophyllum aquaticum and its exudate on two typical bloom-forming cyanobacteria, Microcystis aeruginosa and Anabaena flos-aquae, were investigated under laboratory conditions. The growth of the cyanobacteria was strongly inhibited by live M. aquaticum while the primary addition of M. Aquaticum exudates had a significant inhibitory effect on the growth of M. aeruginosa but not A. flos-aquae. The results suggested that the persistent release of allelochemicals from live M. aquaticum was needed to effectively constrain the growth of A. flos-aquae. Analysis of cyanobacterial physiological indexes indicated that M. aquaticum produced an inhibitory effect on SOD enzyme activity of A. flos-aquae, while it affected membrane lipid peroxidation in M. aeruginosa. The results show the potential of M. aquaticum to mitigate cyanobacterial blooms in coexistence systems.

Effects of nutrient loading on Anabaena flos-aquae biofilm: biofilm growth and nutrient removals.

Effects of three different nutrient loadings (low nutrient loading, medium nutrient loading and high nutrient loading, denoted as LNS, MNS and HNS, respectively) on the structure and functions of algal biofilm using Anabaena flos-aquae were investigated using synthetic wastewater. Nutrients removal efficiencies, biofilm thickness, microalgae dehydrogenase activity (DHA) and exopolysaccharide (EPS) productions were examined. Results showed that the changes of nutrient concentration were insignificant after 4 days of experiment for the case of HNS condition; 9 days for the case of MNS condition, and 6 days for the case of LNS condition, respectively. The biofilm thickness, nutrient removal efficiencies, algae DHA and EPS productions increased with the increase of nutrient loadings in synthetic wastewater. For the case of HNS condition, the microalgal biofilm exhibited the best performance in terms of C, N and P removal efficiencies, reaching the removal rates of 68.45, 3.56 and 1.61 mg·L(-1)·d(-1) for C, N, P, respectively. This was likely because, fact with the high nutrient loading, the high biological activity could be achieved, thus resulting in high nutrient removals. The thickness of the biofilm in HNS condition was 75 µm, which was closely related to EPS production. DHA and EPS concentrations were 7.24 and 1.8 × 10(-2) mg·mm(-2), respectively. It was also shown that apart from the nutrient loading, the structure and functions of microalgal biofilm were also influenced by other factors, such as illumination and temperature.

Effects of monosulfuron on growth, photosynthesis, and nitrogenase activity of three nitrogen-fixing cyanobacteria.

Application of monosulfuron, a new sulfonylurea herbicide, produced a simulative effect on heterocyst formation and nitrogenase activity but an inhibitory effect on photosynthesis, i.e., a lower net photosynthetic rate, fewer photosynthetic pigments, and a smaller Fv/Fm ratio at increasingly higher monosulfuron concentrations (0.001-10 mg/l) for three nonspecific filamentous nitrogen-fixing cyanobacteria: Anabaena azollae, A. flos-aquae, and A. azotica. The decrease in biliprotein of algal cells was less than that of carotenoid and chlorophyll-a. Monosulfuron was more readily degraded and less accumulated in A. azotica compared with A. azollae and A. flos-aquae. The three algae exhibited varying degrees of sensitivity to monosulfuron: Calculated 50% inhibition concentrations (IC(50)s) of algal growth and no observed-effect concentration (NOEC) values after 4 days of treatment were 0.014 and 0.005, 0.029 and 0.019, and 0.22 and 0.075 mg/l for A. flos-aquae, A. azollae, and A. azotica, respectively. Normal agricultural use of monosulfuron at postemergence rates of 0.3-0.8 mg/l in rice fields will likely be toxic to these three ubiquitous nitrogen-fixing cyanobacteria. Low-dose monosulfuron application (<0.1 mg/l) enables growth of the more tolerant A. azotica as biofertilizer, and the use of photosynthetic efficiency and growth rates as sensitive-indicator indexes of toxicity to nitrogen-fixing cyanobacteria are recommended.

A comparison of the role of two blue-green algae in THM and HAA formation.

The contribution of two blue-green algae species, Anabaena flos-aquae and Microcystis aeruginosa, to the formation of trihalomethanes (THMs) and haloacetic acids (HAAs) was investigated. The experiments examined the formation potential of these disinfection by-products (DBPs) from both algae cells and extracellular organic matter (EOM) during four algal growth phases. Algal cells and EOM of Anabaena and Microcystis exhibited a high potential for DBP formation. Yields of total THMs (TTHM) and total HAAs (THAA) were closely related to the growth phase. Reactivity of EOM from Anabaena was slightly higher than corresponding cells, while the opposite result was found for Microcystis. Specific DBP yields (yield/unit C) of Anabaena were in the range of 2-11micromol/mmol C for TTHM and 2-17micromol/mmol C for THAA, while those of Microcystis were slightly higher. With regard to the distributions of individual THM and HAA compounds, differences were observed between the algae species and also between cells and EOM. The presence of bromide shifted the dominant compounds from HAAs to THMs.

Purification and characterization of extracellular beta-glucosidase from Sinorhizobium kostiense AFK-13 and its algal lytic effect on Anabaena flos-aquae.

A beta-glucosidase from the algal lytic bacterium Sinorhizobium kostiense AFK-13, grown in complex media containing cellobiose, was purified to homogeneity by successive ammonium sulfate precipitation, and anion-exchange and gel-filtration chromatographies. The enzyme was shown to be a monomeric protein with an apparent molecular mass of 52 kDa and isoelectric point of approximately 5.4. It was optimally active at pH 6.0 and 40'C and possessed a specific activity of 260.4 U/mg of protein against 4-nitrophenyl-beta-D-glucopyranoside (pNPG). A temperature-stability analysis demonstrated that the enzyme was unstable at 50 degrees C and above. The enzyme did not require divalent cations for activity, and its activity was significantly suppressed by Hg+2 and Ag+, whereas sodium dodecyl sulfate (SDS) and Triton X-100 moderately inhibited the enzyme to under 70% of its initial activity. In an algal lytic activity analysis, the growth of cyanobacteria, such as Anabaena flos-aquae, A. cylindrica, A. macrospora, Oscillatoria sancta, and Microcystis aeruginosa, was strongly inhibited by a treatment of 20 ppm/disc or 30 ppm/disc concentration of the enzyme.

Evaluation of the production, composition and aluminum and iron complexation of algogenic organic matter.

This paper aims at the characterization of algogenic organic matter (AOM) produced by the cyanobacteria Anabaena flos-aqua and Microcystis aeruginosa and the green algae Scenedesmus quadricauda. Further, it is focused on the description of differences in the composition of extracellular organic matter (EOM) and intracellular organic matter (IOM), and on the demonstration of AOM affinity to aluminum and iron coagulants. The results from the conducted analyses imply a significant difference in the amount and properties of the proteins contained in EOM in comparison to IOM. The differences in the production of proteins also depend on the species of microorganism observed and its growth phase; ageing of the culture is accompanied by a gradual increase of the portion of proteins forming AOM. Using affinity chromatography (AC), the proteins with relative molecular weight around 60 kDa were isolated as a component of AOM of cyanobacteria A. flos-aqua and M. aeruginosa. These proteins are able to form complex compounds with iron and aluminum.

[Algaecidal effect of a nanomaterial sheet].

A nanomaterial algaecidal sheet was prepared for algaecidal treatment. The results of algaecidal activity of the nanomaterial algaecidal sheet in lab and field experiments were investigated. It was showed that under the ratio of the area of nanomaterial algaecidal sheet to the volume of algal cell suspension at 0.08 cm2 x mL(-1) and light intensity at 3000 1x, the cell density of algal cell suspension of Microcystis aeruginosa, Anabaena 7120, Euglena gracilis, and Chlamydomonas reinhardtii decreased by 77%, 69.1%, 89.1% and 56.9% respectively after 24 h treatment, and Chla concentration of algal cell suspension of Navicula incerta decreased by 18.7%. Chla concentration of a site with algal bloom in Wuli Lake decreased by 76% after 1 day treatment in the field experiment. Acute fish toxicity test (5 days) of the nanomaterial algaecidal sheet showed no significant toxicity.

Using Dirichlet tessellation to help estimate microbial biomass concentrations.

Dirichlet tessellation was applied to estimate microbial concentrations from microscope well slides. The use of microscopy/Dirichlet tessellation to quantify biomass was illustrated with two species of morphologically distinct cyanobacteria (Microcystis aeruginosa and Anabaena flos aquae), and validated empirically by comparison with chlorophyll a and Coulter count analyses. Biomass estimates obtained by microscopy/Dirichlet tessellation were significantly correlated with the results obtained from chlorophyll a and Coulter analyses.

Differential sensitivity of three cyanobacterial and five green algal species to organotins and pyrethroids pesticides.

In this work, five organotins and pyrethroids pesticides were tested to examine their effects on the three cyanobacteria Anabaena flos-aquae, Microcystis flos-aquae, Mirocystis aeruginosa and on the five green algae Selenastrum capricornutun, Scenedesmus quadricauda, Scenedesmus obliqnus, Chlorella vulgaris, Chlorella pyrenoidosa through 96 h acute toxicity tests. The results indicated that: (1) the decreasing order of the average acute toxicity to cyanobacteria and green algae of five dissimilar organotins and pyrethroids pesticides was: fentin hydroxide > cyhexatin > azocyclotin > fenbutatin oxide > beta-cyfluthrin. (2) Wide variations occurred in response to the tested pesticides among the eight individual species of cyanobacteria and green algae. The sensitivity of various species of algae exposed to fenbutatin-oxide varied over one order of magnitude, exposed to cyhexatin/fentin-hydroxide/beta-cyfluthrin varied over two orders of magnitude and exposed to azocyclotin varied three orders of magnitude. (3) In contrast with the sensitivity of cyanobacteria and green algae, cyanobacteria were much less sensitive to beta-cyfluthrin than green algae. The pollutants may result in a shift of green algal and cyanobacterial group structure, especially in a shift from dominance by green algae to dominance by cyanobacteria, and may sustain cyanobcterial blooms during the special period. Thus, the decreasing order of the aquatic ecological risk was: beta-cyfluthrin > fentin hydroxide > cyhexatin > azocyclotin > fenbutatin oxide. There was a strong variance between toxicity and ecological risk, i.e. "low toxicity" does not automatically imply "low ecological risk". The toxicity of pyrethroids pesticides was lower than that of organotins pesticides, whereas the aquatic ecological risk of pyrethroids pesticides was higher than that of organotins pesticides.

Effects of heavy-metal stress on cyanobacterium Anabaena flos-aquae.

The influence of two metals, copper and cadmium, was studied on the growth and ultrastructures of cyanobacterium Anabaena flos-aquae grown at three different temperatures: 10 degrees C, 20 degrees C, and 30 degrees C. The highest concentration of chlorophyll a was observed at 20 degrees C and the lowest at 10 degrees C. Both toxic metal ions, Cu(2+) and Cd(2+), inhibited growth of the tested cyanobacterium. Chlorophyll a concentration decreased with the increase of metal concentration. A 50% decrease in the growth of A. flos-aquae population, compared with the control, was reached at 0.61 mg l(-1) cadmium and at 0.35 mg l(-1) copper (at 20 degrees C). Copper at all temperatures tested was proven to be more toxic than cadmium. At 3 mg l(-1), the lysis and distortion of cells was observed; however, after incubation at 9 mg l(-1) cadmium, most of the cells were still intact, and only intrathylakoidal spaces started to appear. Copper caused considerably greater changes in the protein system of A. flos-aquae than did cadmium; in this case, not only phycobilins but also total proteins were destructed. The aim of this study was also to identify the place of metal accumulation and sorption in the tested cyanobacterium. Analysis of the energy-dispersion spectra of the characteristic x-ray radiation of trichomes and their sheaths showed that cadmium was completely accumulated in cells but was not found in the sheath. Spectrum of the isolated sheath after treatment with copper exhibited only traces of the metal, but isolated cells without a sheath showed a high peak of copper.