Genera Anabaena Research Articles

The crane fly glycosylated triketide δ-lactone cornicinine elicits akinete differentiation of the cyanobiont in aquatic Azolla fern symbioses.

The restriction of plant-symbiont dinitrogen fixation by an insect semiochemical had not been previously described. Here we report on a glycosylated triketide δ-lactone from Nephrotoma cornicina crane flies, cornicinine, that causes chlorosis in the floating-fern symbioses from the genus Azolla. Only the glycosylated trans-A form of chemically synthesized cornicinine was active: 500 nM cornicinine in the growth medium turned all cyanobacterial filaments from Nostoc azollae inside the host leaf-cavities into akinetes typically secretingCTB-bacteriocins. Cornicinine further inhibited akinete germination in Azolla sporelings, precluding re-establishment of the symbiosis during sexual reproduction. It did not impact development of the plant Arabidopsis thaliana or several free-living cyanobacteria from the genera Anabaena or Nostoc but affected the fern host without cyanobiont. Fern-host mRNA sequencing from isolated leaf cavities confirmed high NH4-assimilation and proanthocyanidin biosynthesis in this trichome-rich tissue. After cornicinine treatment, it revealed activation of Cullin-RING ubiquitin-ligase-pathways, known to mediate metabolite signaling and plant elicitation consistent with the chlorosis phenotype, and increased JA-oxidase, sulfate transport and exosome formation. The work begins to uncover molecular mechanisms of cyanobiont differentiation in a seed-free plant symbiosis important for wetland ecology or circular crop-production today, that once caused massive CO2 draw-down during the Eocene geological past.

Astudy of organic solvents to obtain bio-products from two genus of cyanobacteria, Anabaena sp. 65, Nostoc sp. 69 and identification of toxins in these bio-products by Hplc/Ms technique

This study was conducted to determine the effect of the types of organic solvents (Ethanol, Methanol, Diethyl ether, Acetone and water) on the amount of bio-products derived from two genus of cyanobacteria (Anabaena sp. Tu 65 and Nostoc sp. Tu 69) who were isolated and growth on selective media ASM-1 under temperature at (26) °C and pH (7.6) under continuous lighting intensity (2500) Lux for 30 days. The growth were measured by optical density by spectrophotometer at wave length 436 nm. The daily growth of the genus Anabaena sp. Tu 65 showed higher than that of the genus Nostoc sp. Tu 69.Extractionby organic solvents shown that the Methanol is the best solvent for extraction of bio-products from the two genus followed by Ethanol, Diethyl ether, Acetone and water respectively.
 Identification the toxic compounds in the bio-products by HPLC_MS technique shown that the bio-products from the genus Anabaena sp. Tu 65, the presence of neurotoxin (anatoxin a (s)) as well as the presence of the compound ADDA (3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid), one of the key parts for all types of Microcystins which considered as important of liver toxins produced by cyanobacteria, which, as the spectrum readings showed the presence of hepatic toxin [D-Asp3, Dha7] MCYST-LR is one of the types of Microcystins.
 While the bio-products from the genus Nostoc sp. Tu 69 shown the presence of the compound (MCYST-YM (O)) which also one of the types of liver toxin Microcystin, as well as the presence of another hepatic toxin [D-Asp3, Dha7] MCYST-LR, whichis another type of Microcystins too, as well as the presence of neurotoxin Anatoxin a( s),also the probability of the presence of another neurotoxin Anatoxin, which appeared in the spectrum readings.

The occurrence of the cis/trans geometric isomerism of myxoxanthophyll and 4-ketomyxoxanthophyll in the cyanobacterium Anabaena sp. PCC7120.

The cyanobacteria of the genus Anabaena have recently been recognized as a potential source of secondary metabolites of pharmacological and biotechnological importance. In particular, myxoxanthophylls - specific carotenoid glycosides that accumulate in cyanobacterial cells, are attracting increasing interest. Anabaena (Nostoc) sp. PCC7120, a filamentous, mesophilic, nitrogen-fixing cyanobacterium, is a model organism used in biochemical and genetic studies. The carotenoid pool of Anabaena sp. PCC7120 consists of five main species of pigments, namely β-carotene, echinenone, canthaxanthin and two derivatives of myxoxanthophyll: myxoxanthophyll ((3R,2'S)-myxol 2'-fucoside) and 4-ketomyxoxanthophyll ((3S,2'S)-4-ketomyxol 2'-fucoside). Recent findings show that the carotenoid biosynthesis pathway functions in Anabaena sp. PCC7120 cells are affected by environmental factors. Specifically, the balance between β-carotene and ketocarotenoids alters according to the temperature conditions. In this study, a new method, based on single-step liquid adsorption chromatography was developed and applied to separate a fraction containing myxoxanthophyll and 4-ketomyxoxanthophyll from Anabaena sp. PCC7120 cells. It was found that this method allowed a high purity fraction of carotenoid glycosides to be obtained from pigment pools as extracted from cyanobacterial cells. The subsequent analysis using the methods HPLC and LC/MS demonstrated that this fraction consists of a mixture of compounds with different retention times. On the basis of their fragmentation spectra and optical properties, these compounds were identified as geometrical isomers of myxoxanthophyll and 4-ketomyxoxanthophyll, including the dominant all-trans forms and less abundant cis forms. Proposals regarding the structures of myxoxanthophyll isomers are made.

Tutorial for increasing the potential of microalgae in restoring the ecosystem of the Don River

The article raises questions of anthropogenic impact on continental water bodies. The results of expeditionary studies to increase the potential of microalgae in the improvement of the Tsimlyansk reservoir, created on the Don River on the basis of the use of biological reclamation - algolization, are presented. The reasons for the deterioration of water quality in the reservoir are determined, which are associated with the intensive introduction of pollutants and hydrometeorological conditions that contribute to the intensive development of phytoplankton in the summer-autumn period. At the end of May, the water column warms up rather quickly (+20° C), phytoplankton begins to multiply strongly, the number reaches - 20.5 million cells/l, biomass 15.5 g/m3. The most active are blue-green algae of the genus Anabaena. In July-August, a prolonged increase in water temperature up to 25-27°C contributes to an increase in phytoplankton of blue-green algae of the genera Aphanizomenon, Microcystis, Oscillatoria. Blue-green algae, creating the effect of “blooming” of water, form large colonies and dominate over other types of microorganisms. Thanks to the developments of scientists, it became possible to use biological reclamation in the restoration of ecosystems of natural and artificial reservoirs. Algolization - the introduction of microalgae Chlorella vulgaris into water bodies, allows to improve the quality of water in terms of gas composition, content of organic substances and reduce the effect of water “blooming”.

Structure and spatial distribution of phytoplankton from the Bouake’s research station fishponds (Central, Côte D’ivoire

This study was carried out to evaluate phytoplankton structure from farmed environments at Bouaké’s Fisheries and Aquaculture Research Station (SRPAC). Measure of physical-chemical and phytoplankton flora sampling were realized from December, 2015 to March, 2016. Conductivity, water transparency and temperature were measured in situ. Phytoplankton was sampled in fishpond using a plankton net mesh-size 20 µm between 7 to 9 am. The results showed that conductivity varied from 19, 37 mS/cm ± 0, 21 to 23, 88 mS/cm ± 1, 20. Therefore, water transparency is relatively ranging from 16 cm ± 0,2 to 57 cm ± 0,5. The pond water temperature fluctuated between 28, 34 °C ± 0, 88 and 30, 20 °C ± 1, 27. Phytoplankton flora is spatially heterogeneous and is made up of 197 taxa divided into 7 branches. These are Chlorophyta (36,04%), Euglenophyta (24,87%), Bacillariophyta (14,72%), Cyanobacteria (13,71%), Charophyta (7,11%), Ochrophyta (2,54%) and Miozoa (1,02%).This phytoplankton study confirmed the existence of potential toxigenic microalgae identified in genus Anabaena, Anabaenopsis, Cylindrospermopsis, Lyngbya, Microcystis, Oscillatoria and Peridinium that could interfere with fish production. This study showed the main phytoplankton communities which dominate in the fish ponds of the Bouaké Research Station.

Temperature and precipitation significantly influence the interactions between arbuscular mycorrhizal fungi and diazotrophs in karst ecosystems

Arbuscular mycorrhizal fungi (AMF) and diazotrophs have the potential for nutrient transfer and biological nitrogen fixation in ecosystems, respectively. However, their response to vegetation restoration remains unclear, especially under varying temperature and precipitation levels in karst ecosystems. This study aimed to understand the effects of three climatic levels within four natural and managed vegetation restoration types on the diversity and community composition of AMF and diazotrophs. The interactive effects of temperature, precipitation, and vegetation types affected AMF diversity, while diazotroph diversity was not affected. Under conditions of natural vegetation restoration, there was an increase in AMF diversity in response to increasing temperature and precipitation. AMF richness was higher in shrubland and mature forest than in cropland when temperatures were over 20 ℃ and precipitation was high. Thus, in terms of diversity, AMF were more responsive to changes in climatic conditions and vegetation recovery than diazotrophs. Both AMF and diazotroph community compositions were affected by temperature and vegetation type. The relative abundances of AMF groups (e.g., Gigaspora, Glomus, and Septoglomus) and diazotroph taxa (e.g., Frankia) increased at temperatures above 18 ℃. The relative abundances of the AMF genus Glomus and the diazotroph genus Bradyrhizobium in shrubland and mature forest were higher than those in cropland, while abundances of the AMF genus Septoglomus and diazotroph genus Anabaena increased in cropland. Network complexity increased with increasing temperature and precipitation between AMF and diazotroph taxa. Glomus and Bradyrhizobium showed the most links with other groups, confirming that the dominant genera perform well in the co-occurrence network. These results suggested high hydrothermal regions resist rapid nutrient decomposition by strengthening the interactions between AMF and diazotrophs, especially between the abundant groups Glomus and Bradyrhizobium. Management to increase AMF and diazotroph abundance during vegetation recovery in high climate level may stimulate nutrient absorption and transport.

Vertical Distribution and Migration of Algae under Thermal Stratification in Small Water Bodies of the Forest-Steppe Volga Region

In this article the author presents some study results of taxonomic composition, distribution and migrations of algae under thermal stratification in small water bodies of the forest-steppe Volga region. The author considers the main factors influencing the formation of heterogeneity of the structure of algocoenoses: vertical temperature gradients, water density and the content of basic biogenic substances. The composition of vertically migrating common species is discovered. The nature of species distribution during the day is shown, when samples are taken with an interval of 3 hours. The predominance of mobile mixotrophic phytoflagel-lates is a feature of the taxonomic composition of algae in water bodies with a pronounced vertical heterogeneity of populations of dominant species. The clearest picture of distribution and migration in plankton is demonstrated by Pandorina morum, Mallomonas caudata, Dinobryon divergens, Cryptomonas curvata, and a number of other large-cell flagellar forms. Of the species without active movement, vertical distribution was constantly observed in Westella botry-oides, Botryococcus braunii, Dictyosphaerium pulchellum, Koliella longiseta, Woronichinia naegeliana, and some species of the genus Anabaena. The author notes the connection between the maximums of the abundance of some common species with changes in the content of nutrients within the photic zone. Vertical heterogeneity of taxonomic and quantitative indicators in algocoenoses is considered as an adaptive strategy to the heterogeneity of the habitat in highly eutrophic water bodies with a high density of algae in plankton.

Cyanobacterial Akinete Distribution, Viability, and Cyanotoxin Records in Sediment Archives From the Northern Baltic Sea

Cyanobacteria of the order Nostocales, including Baltic Sea bloom-forming taxa Nodularia spumigena, Aphanizomenon flosaquae, and Dolichospermum spp., produce resting stages, known as akinetes, under unfavorable conditions. These akinetes can persist in the sediment and germinate if favorable conditions return, simultaneously representing past blooms and possibly contributing to future bloom formation. The present study characterized cyanobacterial akinete survival, germination, and potential cyanotoxin production in brackish water sediment archives from coastal and open Gulf of Finland in order to understand recent bloom expansion, akinete persistence, and cyanobacteria life cycles in the northern Baltic Sea. Results showed that cyanobacterial akinetes can persist in and germinate from Northern Baltic Sea sediment up to >40 and >400 years old, at coastal and open-sea locations, respectively. Akinete abundance and viability decreased with age and depth of vertical sediment layers. The detection of potential microcystin and nodularin production from akinetes was minimal and restricted to the surface sediment layers. Phylogenetic analysis of culturable cyanobacteria from the coastal sediment core indicated that most strains likely belonged to the benthic genus Anabaena. Potentially planktonic species of Dolichospermum could only be revived from the near-surface layers of the sediment, corresponding to an estimated age of 1–3 years. Results of germination experiments supported the notion that akinetes do not play an equally significant role in the life cycles of all bloom-forming cyanobacteria in the Baltic Sea. Overall, there was minimal congruence between akinete abundance, cyanotoxin concentration, and the presence of cyanotoxin biosynthetic genes in either sediment core. Further research is recommended to accurately detect and quantify akinetes and cyanotoxin genes from brackish water sediment samples in order to further describe species-specific benthic archives of cyanobacteria.

Assessment of small water bodies Sergiev Posad district on the taxonomic diversity of green, blue-green and diatom algae

The purpose of the study was to determine the degree of saprobity of the artificial extension of the Vytravki riverbed (left tributary of the Dubna river) in the Sergiev Posad district of the Moscow region, based on the taxonomic composition of the pelagial and littoral algal flora. For this purpose, the systematic position of algae was determined using a number of domestic and foreign sources, as well as using the electronic database AlgaeBase. The most attention was paid to common indicator types, according to the literature data. Algological samples were taken in accordance with generally accepted methods; the main part of the samples was processed immediately after collection on site, the rest of the material was fixed with a formalin solution and Prat medium for detailed study in laboratory conditions under a microscope. According to the results of the study of hydrobiological samples, the composition of algal flora in the summer-autumn period was determined. There is a large species diversity of algae, represented by most of the divisions characteristic of the Central part of Russia. The green, diatomaceous, and blue-green algae divisions were the most represented. Maximum species diversity was observed for the genera Scenedesmus (9 species) and Pediastrum (10 species). Diatoms are the second group in terms of frequency of occurrence of species that live both in standing water and in rheophilic conditions. Blue-green algae were represented by pelagic forms, with a small frequency of occurrence. Among them, the genera Anabaena (5 species) and Microcystis (3 species) are notable for their high species diversity. The algal flora of the pond was marked divisions, dinophyceae and kropotova, typical for oligotrophic and distrophic reservoirs, indicating a high quality water environment. The established hydrochemical parameters of the reservoir were normal and were similar to the reservoirs of Central Russia at the end of the growing season, which were not exposed to anthropogenic impact.

Variations in the Temporal and Spatial Distribution of Microalgae in Aquatic Environments Associated with an Artificial Weir

The construction of weirs causes changes in the aquatic environment and affects several aquatic organisms. To understand the ecosystem in the Sangju Weir, Gyeongsangbuk-do Province, variations in the spatiotemporal distribution and composition of microalgae communities were analyzed. Microalgae were collected fortnightly from April to November 2018 from six sites in the Nakdonggang River. There was significant variation in environmental factors, microalgal community structure, and flora. Microalgae communities were dominated by diatoms (e.g., Fragilariacrotonensis, Ulnariaacus, and Aulacoseiraambigua), green algae (e.g., genera Eudorina and Desmodesmus), cyanobacteria (e.g., genera Anabaena and Microcystis). Multidimensional scaling indicated that species composition and diversity were generally similar among sites but varied between the bottom and the surface and middle water layers. Vertical migration of microalgae was difficult to investigate because of the thermocline in the study area and high turbidity in the lower layer. The distribution of microalgae was little affected by the construction of the weir, but the formation of thermocline changed microalgae communities in the water layer.

Современное состояние и динамика флоры некоторых малых озер Ярославской области

The phytoplankton and vascular aquatic plants have been studied in small lakes Vashutinskoe, Chashnitskoe, Ryumniki, and Zaozer’e, located in the southern part of the Yaroslavl Region, Russia. The taxonomic composition of phytoplankton comprised 137 species of algae belonging to 8 divisions, 18 orders, and 76 genera. The studied water bodies were characterized by high biomass of cyanobacteria. Aphanizomenon flos-aquae (L.) Ralfs ex Born et Flah. and the species of the genus Anabaena had a significant contribution to the phytoplankton biomass in the lakes Zaozer’e, Chashnitskoe, and Ryumniki, Limnothrix planctonica (Wołosz.) Meff. and Microcystis aeruginosa (Kütz.) Kütz, in the Lake Vashutinskoe. In terms of phytoplankton biomass, the pelagial and shallow areas of the Lake Vashutinskoe belonged to eutrophic reservoirs, of the Lake Ryumniki, to oligotrophic. The phytoplankton biomass in the pelagial zone of the lakes Chashnitskoe and Zaozer’e indicated the mesotrophic status of these water bodies, in the littoral zone, eutrophic. The study of the phytoplankton of the lakes was carried episodically and was often performed at different periods of the growing season. Therefore, the obtained data did not allow one to assess the direction of the successional changes in the algal flora. The flora of vascular plants of lakes was represented by 118 species belonging to 4 divisions, 5 classes, 22 orders, and 37 families. Thirty-four species were common to all studied water bodies. The differences in the The differences in the flora of vascular aquatic plantsof the studied lakes were associated with differences in their trophic status, the presence of various biotopes, the nature of anthropogenic load, and the degree of eutrophication. During a hundred years of observations, some species have disappeared, but some have appeared, including adventive species (such as Elodea canadensis Michx., Bidens frondosa L., Epilobium adenocaulon Hausskn, Zizania latifolia Griseb., and Juncus tenuis Willd.). The study of the current state of rare and protected species of vascular plants made it possible to reveal the eventual causes and period of disappearance of some species from the lakes. The taxonomic and ecological structure of phytoplankton and vascular plants of lakes was quite diverse and usual for the water bodies of the European part of Russia.

Age matters: Submersion period shapes community composition of lake biofilms under glyphosate stress

The phosphonate herbicide glyphosate, which is the active ingredient in the commercial formulation Roundup®, is currently the most globally used herbicide. In aquatic ecosystems, periphytic biofilms, or periphyton, are at the base of food webs and are often the first communities to be in direct contact with runoff. Microcosm experiments were conducted to assess the effects of a pulse exposure of glyphosate on community composition and chlorophyll a concentrations of lake biofilms at different colonization stages (2 months, 1 year, and 20 years). This is the first study that uses such contrasting submersion periods. Biofilms were exposed to either environmental levels of pure analytical grade glyphosate (6 μg/L, 65 μg/L, and 600 μg/L) or to corresponding phosphorus concentrations. Community composition was determined by deep sequencing of the 18S and 16S rRNA genes to target eukaryotes and cyanobacteria, respectively. The results showed that submersion period was the only significant contributor to community structure. However, at the taxon level, the potentially toxic genus Anabaena was found to increase in relative abundance. We also observed that glyphosate releases phosphorus into the surrounding water, but not in a bioavailable form. The results of this study indicate that environmental concentrations of glyphosate do not seem to impact the community composition or metabolism of lake biofilms under pulse event conditions.

Approach to improve the productivity of bioactive compounds of the cyanobacterium Anabaena oryzae using factorial design

Cyanobacteria are one of the richest sources of biomedical relevant compounds with extensive therapeutic pharmaceutical applications and are also known as producer of intracellular and extracellular metabolites with diverse biological activities. The genus Anabaena sp. is known to produce antimicrobial compounds, like phycocyanin and others. The goal of this study was to optimize the production of these bioactive compounds. The Plackett–Burman experimental design was used to screen and evaluate the important medium components that influence the production of bioactive compounds. In this present study, eight independent factors including NaNO3, K2HPO4, MgSO4·7H2O, CaCl2, citric acid, ammonium ferric citrate, ethylene diamine tetraacetic acid disodium magnesium salt (EDTA-Na2Mg) and Na2CO3 were surveyed and the effective variables for algal components production of Anabaena oryzae were determined using two-levels Plackett–Burman design. Results analysis showed that the best medium components were NaNO3 (2.25gl−1); K2HPO4 (0.02gl−1); MgSO4 (0.0375gl−1); CaCl2 (0.018gl−1); citric acid (0.009gl−1); ammonium ferric citrate (0.009gl−1) and EDTA-Na2 (0.0015gl−1) respectively. The total chlorophyll-a, carotenoids, phenol, tannic acid and flavonoid contents in crude extract of Anabaena oryzae were determined. They were 47.7, 4.11, 0.256, 1.046 and 1.83μg/ml, respectively. The antioxidant capacity was 62.81%.

16S rRNA 분석에 의한 Subsection IV cyanobacteria 균주들의 다계통성 기원의 증거

Unicellular cyanobacterial strains of Subsections Ⅰ and Ⅱ and filamentous cyanobacterial strains of Subsection Ⅲ have been shown to be polyphyletic, heterocystous strains of Subsections Ⅳ and Ⅴ, both of which were previously reported to be monophyletic. In this study, the small subunit ribosomal RNA (16S rRNA) sequences of 13 strains of cyanobacteria - one strain, Oscillatoria nigro-viridis PCC7112, of the Subsection Ⅲ, 6 strains including genus Anabaena, Nostoc, Tolypothrix, Calothrix and Scytonema of the Subsection Ⅳ, and 6 strains including genus Hapalosiphon, Fischerella and Chlorogloeopsis of the Subsection Ⅴ - were determined. The phylogenetic analysis of cyanobacteria was carried out using the 16S rRNA sequences. The results of the phylogenetic analyses of 16S rRNA sequences, based on Neighbour-joining, maximum-parsimony, and maximum-likelihood methods, indicated that the members of Subsection Ⅳ were not monophyletic but polyphyletic. In addition, the phylogenetic results strongly indicated that the genus Scytonema in Subsection Ⅳ could be a common ancestor of heterocystous cyanobacteria in Subsection Ⅳ and Ⅴ. Furthermore, the phylogenetic analyses revealed that the genus Anabaena could be phylogenetically diverse and that cyanobacterial strains in Subsection Ⅳ might be polyphyletic, whereas those in Subsection Ⅴ could be monophyletic, as reported before. The results for the genus Anabaena indicate that it should be reclassified.

Formation and maintenance of nitrogen-fixing cell patterns in filamentous cyanobacteria

Cyanobacteria forming one-dimensional filaments are paradigmatic model organisms of the transition between unicellular and multicellular living forms. Under nitrogen-limiting conditions, in filaments of the genus Anabaena, some cells differentiate into heterocysts, which lose the possibility to divide but are able to fix environmental nitrogen for the colony. These heterocysts form a quasiregular pattern in the filament, representing a prototype of patterning and morphogenesis in prokaryotes. Recent years have seen advances in the identification of the molecular mechanism regulating this pattern. We use these data to build a theory on heterocyst pattern formation, for which both genetic regulation and the effects of cell division and filament growth are key components. The theory is based on the interplay of three generic mechanisms: local autoactivation, early long-range inhibition, and late long-range inhibition. These mechanisms can be identified with the dynamics of hetR, patS, and hetN expression. Our theory reproduces quantitatively the experimental dynamics of pattern formation and maintenance for wild type and mutants. We find that hetN alone is not enough to play the role as the late inhibitory mechanism: a second mechanism, hypothetically the products of nitrogen fixation supplied by heterocysts, must also play a role in late long-range inhibition. The preponderance of even intervals between heterocysts arises naturally as a result of the interplay between the timescales of genetic regulation and cell division. We also find that a purely stochastic initiation of the pattern, without a two-stage process, is enough to reproduce experimental observations.

A detailed morphological, phylogenetic and ecophysiological analysis of four benthic Anabaena (Nostocales, Cyanobacteria) strains confirms deep heterogeneity within the genus

Four benthic Anabaena strains isolated from different localities in the Czech Republic were examined from the morphological, phylogenetic, and physiological points of view. The results of combined analysis showed distinct morphological dissimilarity between the studied strains, which were further found to belong to different phylogenetic groups based on the 16S rRNA gene phylogeny. To assess the temperature and light (irradiance) optima of the strains, we exposed them to various combinations of these two parameters. The experiment revealed unexpectedly high temperature and light optima for some of the strains, while others showed optima that were similar to those of previously studied planktic species of related heterocytous genera. Our study is the first of its kind to be applied to benthic Anabaena strains. Our results indicate that the benthic Anabaena genus is much more complex than previously thought and provide novel insights into the biology and ecology of benthic Anabaena species. With the collection of more data, we expect the genus Anabaena will be split into several new monophyletic taxa, each covering distinct morpho- and ecotypes.

Biodegradation of polychlorinated biphenyls (PCBs) by the novel identified cyanobacterium Anabaena PD-1.

Polychlorinated biphenyls (PCBs), a class of hazardous pollutants, are difficult to dissipate in the natural environment. In this study, a cyanobacterial strain Anabaena PD-1 showed good resistance against PCB congeners. Compared to a control group, chlorophyll a content decreased 3.7% and 11.7% when Anabaena PD-1 was exposed to 2 and 5 mg/L PCBs for 7 d. This cyanobacterial strain was capable of decomposing PCB congeners which was conclusively proved by determination of chloride ion concentrations in chlorine-free medium. After 7 d, the chloride ion concentrations in PCB-treated groups (1, 2, 5 mg/L) were 3.55, 3.05, and 2.25 mg/L, respectively. The genetic information of strain PD-1 was obtained through 16S rRNA sequencing analysis. The GenBank accession number of 16S rRNA of Anabaena PD-1 was KF201693.1. Phylogenetic tree analysis clearly indicated that Anabaena PD-1 belonged to the genus Anabaena. The degradation half-life of Aroclor 1254 by Anabaena PD-1 was 11.36 d; the total degradation rate for Aroclor 1254 was 84.4% after 25 d. Less chlorinated PCB congeners were more likely to be degraded by Anabaena PD-1 in comparison with highly chlorinated congeners. Meta- and para-chlorines in trichlorodiphenyls and tetrachlorobiphenyls were more susceptible to dechlorination than ortho-chlorines during the PCB-degradation process by Anabaena PD-1. Furthermore, Anabaena PD-1 can decompose dioxin-like PCBs. The percent biodegradation of 12 dioxin-like PCBs by strain PD-1 ranged from 37.4% to 68.4% after 25 days. Results above demonstrate that Anabaena PD-1 is a PCB-degrader with great potential for the in situ bioremediation of PCB-contaminated paddy soils.

Detection of cyanobacterial sxt genes and paralytic shellfish toxins in freshwater lakes and brackish waters on Åland Islands, Finland

Harmful cyanobacteria are a globally growing concern. They produce a large variety of toxic compounds, including saxitoxin and its many structural variants, a group of potent neurotoxins collectively called paralytic shellfish toxins or PST. Nucleic acid based detection methods, such as qPCR, have been proposed as potential screening and monitoring tools for toxic cyanobacteria, but it is not clear how well the presence and quantity of saxitoxin biosynthesis (sxt) genes can be used to predict the production of PST in the environment. In this study, the prevalence of three sxt genes and their co-occurrence with paralytic shellfish toxins in the environment was investigated. The sxtA, sxtG and sxtB genes were present on average in 31% of the samples collected from lakes and brackish coastal waters on Åland Islands, Finland, during the three-year monitoring period. PST detection frequency varied from 13% to 59% from year to year, and concentrations were generally low. On average higher sxtB copy numbers were associated with PST detection, and although a positive correlation between gene copy numbers and toxin concentrations was observed (Spearman rank correlation, ρ=0.53, P=0.012), sxt gene presence or quantity didn’t reliably predict PST production. Sequencing of sxtA fragments and identification of main cyanobacteria indicated that the likely candidate responsible for PST production in the samples belonged to the genus Anabaena.

Saxitoxin-Producing cyanobacteria in Lake Baikal

Cyanobacteria containing neurotoxic saxitoxin synthesis genes were found in the coastal zone of Lake Baikal near the village of Turka for the first time. Phylogenetic analysis showed that the sequences of saxitoxin synthesis genes belong to the genus Anabaena Bory. Saxitoxin concentration in the water according to ELISA was 1.93 ± 0.64 mg/L. The genetic and taxonomic composition of the bacterial community of the central part of Lake Baikal was characterized using 16S rRNA gene pyrosequencing. It was established that the phylum Cyanobacteria dominated in the composition of summer bacterioplankton in both littoral and pelagic zones of the lake, but higher species diversity was found in the plankton of littoral zone.

Investigation on the Nitrogen Fixing Cyanobacteria (BGA) in Rice Fields of North-West Region of Bangladesh. III: Filamentous (Heterocystous)

The experiment was conducted to carry out the nitrogen fixing cyanobacterial (BGA) resources and their distribution pattern in rice fields of North-West region of Bangladesh during the period of 2011. Considering the vast importance of Blue-green algae (BGA) in agricultural land especially in rice fields, their twelve months long systematic was undertaken. A total of 10 genera with 37 species of filamentous-heterocystous blue-green algal forms were identified and recorded from this region. Out of 37 species, 9 species belonging to the genus Anabaena, 8 to Nostoc, 5 to Cylindrospermum, 4 to Calothrix, 3 to Rivularia, 3 to Gloeotrichia and 2 to Aulosira; while 1 species belonging to each genus of Anabaenopsis, Microcheate and Aphanizomenon. The distribution pattern of filamentous-heterocystous BGA in rice fields over the study area has also been observed in this study. With few exceptions, the filamentous-heterocystous BGA are more or less uniformly distributed all over the study areas. All of the BGA members have a tremendous ability to contribute on enhancing agricultural production by fixing atmospheric nitrogen and adding organic matter, vitamins, growth promoting substances etc to the soil and crops.DOI: http://dx.doi.org/10.3329/jesnr.v6i1.22075 J. Environ. Sci. & Natusral Resources, 6(1): 253-259 2013