Microcystis Wesenbergii Research Articles

A proposal for the unification of five species of the cyanobacterial genus Microcystis Kützing ex Lemmermann 1907 under the rules of the Bacteriological Code.

Genomic DNA homologies were examined from six Microcystis (cyanobacteria) strains, including five different species, Microcystis aeruginosa, Microcystis ichthyoblabe, Microcystis novacekii, Microcystis viridis and Microcystis wesenbergii. All DNA-DNA reassociation values between two strains of M. aeruginosa and the other four species exceeded 70%, which is considered high enough for them to be classified within the same bacterial species. It is proposed to unify these five species into M. aeruginosa under the Rules of the Bacteriological Code and NIES843T (= IAM M-247T) is proposed as the type strain. Two other species, Microcystis flos-aquae and Microcystis pseudofilamentosa, should be regarded as morphological variations of this unified M. aeruginosa. The current taxonomy of cyanobacteria depends too much upon morphological characteristics and must be reviewed by means of bacteriological methods as well as traditional botanical methods.

On the dominance of the planktic cyanobacterium Microcystis wesenbergii - ecological and statistical analysis of the population

Water bloom forming cyanobacteria are dominant in the summer phytoplankton in an eutrophic reservoir Brno, Czech Republic. The reservoir is used for recreation and as a source for drinking water. Microcystis aeruginosa was a dominant organism in this reservoir, until the beginning of 1990's. In 1994 Microcystis aeruginosa was dominant together with Aphanizomenon flos-aquae, Anabaena flos-aquae, A. lemmermannii, Microcystis ichthyoblabe and M. wesenbergii at the beginning of summer period. In July Microcystis aeruginosa suddenly disappeared, and Microcystis wesenbergii became dominant. This species was already observed there before, but only as a minor component of cyanobacterial bloom. Microcystis wesenbergii is not the typical species forming mass developments. It is known as common component of the blooms dominated by another species. Nevertheless, in the 1994 Microcystis wesenbergii reached an extraordinary dominance. More than 1200 colonies per ml were observed and concentration of chlorophyll a reached 51.75 mg.m -3 . Biomass of this cyanobacterium formed almost 3 cm thick scum near the shore.

DNA-DNA reassociation among a bloom-forming cyanobacterial genus, Microcystis.

DNA base composition and DNA-DNA hybridization among the cyanobacterial genus Microcystis were determined using nine axenic Microcystis strains, including the three 'morphological' species of Microcystis aeruginosa, Microcystis viridis and Microcystis wesenbergii. These Microcystis species showed a similar DNA base composition (42.1-42.8 mol% G + C) and demonstrated more than 70% DNA relatedness, confirming their synonymy based on bacterial criteria.

Morphological variability of colonies of Microcystis morphospecies in culture.

Serial observations were carried out on cultures of five morphospecies of the genus Microcystis Kützing ex Lemmermann 1907, Microcystis aeruginosa (Kützing) Kützing, Microcystis ichthyoblabe Kützing, Microcystis novacekii (Komárek) Compére, Microcystis viridis (A. Brown) Lemmermann, and Microcystis wesenbergii (Komárek) Komárek in Kondratieva. Many strains maintained colony forms characteristic of their morphospecies, and others showed morphological variations, some of which were characteristic of other morphospecies. M. novacekii displayed several morphotypes including some characteristics of M. aeruginosa and M. ichthyoblabe. M. wesenbergii also showed great morphological variability and showed morphotypes characteristic of M. aeruginosa. Distinction among these morphospecies, therefore, seemed to be obscure or impossible. We conclude that the current classification of the genus Microcystis, chiefly based on morphological characteristics, is no longer valid and must be reviewed in light of our observations that one strain may have various colony forms.

Predation and Degradation Characteristics of Microcystis Forming Water Bloom by Combination of Functional Microanimals.

Predation and degradation characteristics of cyanobacteria, Microcystis using functional micro-animals, Mastigophora Monas guttula, Rotifera Philodina erythrophthalma and Oligochaeta Aeolosoma hemprichi, which were isolated from a biofilm in a practical biological treatment facility as a preliminary treatment of source water for water supply, were examined in batch predation and degradation experiment. A small flagellate, M.guttula effectively predated on the singly dispersed viable cells of Microcystis wesenbergii with the removal ratio of 94% for 6 days. As for the predation of the colonial M.wesenbergii, A.hemprichi was found to play an important role for the effective degradation of Microcystis by M.guttula. It was also clarified that A.hemprichi could enhance the degradation of the natural colony of Microcystis obtained from eutrophicated lake water. In order to reduce effectively the colonial Microcystis, it is important to activate a food chain of sequential functional microorganisms in aquatic ecosystem.

Effects of nutrient enrichment on the growth rates and community structure of summer phytoplankton from the Gulf of Riga, Baltic Sea

Sea water collected in mid-July was spiked with different combinations of nutrients. Dissolved inorganic nitrogen (DIN) became exhausted, while significant amounts of P-PO4 and Si- SiO3 remained available. NH, was taken up before NO3, but, in some cultures, NO3 uptake appears to have started in the presence of -7.5 uM N-NH4. In the original assemblage, 29 species were found, belonging to five algal divisions. Cryptophytes and chlorophytes dominated the numbers of indi- viduals, while diatoms and cyanobacteria contributed most to the total biovolume. The toxic dino- flagellate Dinophysis acuminata contributed 5% of the total biovolume. The diatom Skeletonema costatum and the cyanobacterium Microcystis reinboldii were the fastest growers during the first days of culturing, with growth rates up to 1.7 divisions (div.) day-1. Growth rates of the chlorophyte Oocystis borgei and of the cyanobacteria Microcystis wesenbergii and Snowella lacustris were highest during the last days of the culture period, with >1 div. day1. At the end of the experiment, 17 out of the original 29 species had disappeared, including most dinoflagellates and diatoms, species numbers of both chlorophytes and cryptophytes halved, while only one cyanobacterium out of five disappeared. The chlorophyte O.borgei increased its biovolume from 7.7% to 51.0% of the total, while the cyanobacteria M.reinboldii and S.lacustris increased theirs from 0.1% to 10.8%, and from 12.4% to 63.5%, respectively. Five species not found in the original assemblage were recorded at the end of the experiment. Overall, the cryptophytes were a large or the largest component of the standing stock after 3 days, while diatoms contributed most to the total biovolume; nonetheless, the contribution by other taxa was still significant. At the end of the experiment, chlorophytes and cyanobacteria were the dominant taxa, while contributions by other taxa to both the standing stock and the biovolume were negligible, except in iron- and (Co + Mn + Mo)-supplemented cultures. In cultures to which iron had been added, the nitrogen yield index was 2.4 times higher than for similar nutrient conditions but without iron. The ability to sustain growth from uptake of dissolved organic matter (DOM) and N2 fixation, combined with production of aUelopathic substances, is assumed to have enabled the cyanobacteria to dominate the assemblages by the end of the culture period.

Persistence of cyanobacterial hepatotoxin, microcystin-LR in particulate material and dissolved in lake water

The persistence of cyanobacterial hepatotoxin, microcystin-LR, was investigated in Lake Tuusulanjärvi in southern Finland from August to October, 1993 and 1994. The amount of toxin in particulate material and dissolved in water were determined by HPLC from samples collected from mesocosm enclosures and from the surrounding lake water. In the beginning of the experiments over 80% of the phytoplankton biomass consisted of cyanobacteria. The main species were Microcystis wesenbergii (Chroococcales, Cyanobacteria), M. viridis and M. aeruginosa. The microcystin-LR concentration in particulate material varied from 2.7 to 3.2 μg l −1 and the corresponding concentration of microcystin LR dissolved in water from 0.06 to 0.21 μg l −1. The cyanobacterial biomass decreased towards the middle of September and simultaneously the microcystin concentration in freeze dried particulate material decreased below the detection limit of 10 μg g −1, corresponding 0.01 μg l −1. Dissolved microcystin-LR was detected in a concentration range of 1 to 5 ng l −1 even at the end of the experiments in October, when the cyanobacterial biomass was less than 1 mg l −1. Thus, dissolved microcystin was more persistent compared to microcystin in particulate material: the decimal reduction time for dissolved toxin was 30 d and for toxin in particulate material about 15 d.

Species composition and seasonal cycles of phytoplankton with special reference to the nanoplankton of Lake Mikri Prespa

The phytoplankton of Lake Mikri Prespa was studied atmonthly or biweekly intervals during the period May1990–September 1992. Its species composition,consisting of a great number of cyanophytes and a verysmall number of chrysophytes and desmids, may reflectthe eutrophic character of the lake. Moreover, themean annual biomass values (15.0 and 3.2 g m−3 inthe two years, respectively) and the maximum biomass(38.1, 6.4 and 9.6 g m−3), classify Mikri Prespaas a eutrophic lake. A tendency towards adouble-peaked pattern of biomass distribution in timewith one peak in autumn, composed mainly ofcyanophytes, and another in spring made up of diatoms,was observed. This pattern contrasts with the standardpattern in eutrophic, stratified temperate lakes,which exhibit a third biomass maximum in summer. Cyanophytes were the most important group in terms ofbiomass and were dominated by the species Microcystis aeruginosa, Microcystis wesenbergii,Anabaena lemmermannii var. minor and Aphanocapsa elachista var. conferta. Diatomsconstituted the second most important group, with main representative the species Cyclotellaocellata. Cyanophytes, diatoms, chlorophytes anddinophytes revealed annual periodicity whereas theother algal groups did not show any seasonality atall. The nanoplankton constituted an important part ofalgal biomass (38.9 and 49.9% in the two years,respectively) and revealed annual periodicity withmaximum values in winter and spring, mainly composedof diatoms and cryptophytes. Low temperature,increased rainfall and high DIN concentrations seemedto be the main factors influencing the seasonality.Although the percentage contribution of nanoplanktondecreased with the increase in total biomass,justifying the classification of Lake Mikri Prespaamong the eutrophic lakes, the nanoplankton biomassdid not correlate significantly with totalphytoplankton biomass.

Hepatotoxic microcystin diversity in cyanobacterial blooms collected in portuguese freshwaters

Twelve toxic cyanobacterial bloom samples collected in natural lakes, reservoirs and rivers of Portugal were analysed. Toxicity was evaluated by mouse LD 50 bioassay of the lyophilised samples. The main bloom species present in the samples were Microcystis aeruginosa, Microcystis wesenbergii, Anabaena flos-aquae and Nostoc sp. Toxins were extracted, isolated by reverse phase HPLC and characterised by HPLC amino acid analysis and fast atom bombardment mass spectrometry. Two to seven microcystins were purified from each sample, and a total of seven different toxins were isolated and their structure assigned. MCYST-LR was the most common and its proportion in each sample ranged from 45.5% to 99.8% of the total microcystin contents. MCYST-RR, MCYST-YR and [D-Asp 3]MCYST-LR were also identified in the samples. Three less common microcystins, MCYST-HilR, [L-MeSer 7]MCYST-LR and [Dha 7]MCYST-LR, were found in only one sample. Total MCYST concentration varied from 1.0 to 7.1 μg/mg dry weight of cyanobacteria. Significant relationships between LD 50-MCYST-LR-total MCYST content were found. The need for monitoring cyanobacteria and their toxins in eutrophic waters that are used for drinking and recreation purposes is discussed.

鳥取県湖山池における池水の理化学的・生物学的特性の現状と相互関係

The actual conditions of physical, chemical and biological properties and interrelationship between them in the eutrophic Lake Koyama in Tottori were investigated in 1991 and 1992.In the both years, the blue-green algae made bloom in early summer (dominantly, Anabaena solitaria) and fall (dominantly, Microcystis wesenbergii). The outbreak of Anabaena might be brought about by low N, especially water soluble N of the water in May and June. Anabaena made the water rich in the non-soluble N. The soluble N of the water increased after the disappearance of Anabaena.Microcystis became dominant soon after the disappearance of Anabaena. It made bloom in October. It seemed difficult to explain the outbreak of Microcystis by the change in the N concentration of the water. The concentration of P, however, was always enough for the growth of blue-green algae. It was found out that the both blue-green algae suppressed the growth of other algae.The water temperature became maximum in August and seemed one of the major factors of bloom outbreak. It, however, was also difficult to explain the outbreak of Microcystis by the change in the water temperature.The peak time of the CFU was close to that of the algae, which suggested the interrelationship between bacteria and algae.

Toxicity of Microcystis species isolated from natural blooms and purification of the toxin

Microcystis strains (2 toxic and 18 nontoxic to mice) were isolated from toxic waterblooms that had been collected from Lake Kasumigaura, Ibaraki Prefecture, Japan, in August 1985. Thirteen of the strains (2 toxic and 11 nontoxic) were Microcystis aeruginosa, 2 (nontoxic) were Microcystis wesenbergii, and the other 5 were difficult to identify. Six (1 toxic and 4 nontoxic M. aeruginosa and 1 M. wesenbergii) of these 20 strains were established as axenic cultures. A toxic and axenic strain of M. aeruginosa, K-139, was used to study the relationship between growth conditions and toxicity. Cells in early-to-mid-log phase showed the highest toxicity (50% lethal dose, 7.5 mg of cells per kg of mouse), and maximum toxicity was not affected by growth temperatures between 22 and 30 degrees C. Purification and characterization of the toxins from K-139 cells were also conducted, and at least two toxins were detected. One of the toxins (molecular mass, 980 daltons) has not been reported previously. The main target of the toxin in mice was the liver. Marked congestion and necrosis in the parenchymal cells around the central veins of the liver were observed microscopically in specimens that had been prepared from the mice with acute toxicity after injection with the toxin.

Zooplankton grazing on [methyl‐3H]thymidine‐labeIled natural particle assemblages: determination of filtering rates and food selectivity

SUMMARY. 1. The grazing of [methyl‐3H]thymidine‐labelled bacteria by zooplankton was studied in Lake Norrviken. Sweden.2. Animals did not ingest bacteria attached to large colonies of the cyanobacterium Microcystis wesenbergii Kom. but small aggregates of hacteria and free bacteria were readily consumed.3. Diaphanosoma brachyurum (Liévin). Daphnia cucullata Sars. and Daphnia galeata Sars grazed free bacteria more quickly than aggregates, but Endiaptomus gracilis (Sars), Chydorus sphaericus Müll. and Bosmi‐ na coregoni s.l. Baird grazed the aggregates more readily.4. Filtering rate determinations varied from LA to 123 μl ind. −1h − 1for various species.

Autoradiographic Studies of [ methyl - 3 H]Thymidine Incorporation in a Cyanobacterium ( Microcystis wesenbergii )-Bacterium Association and in Selected Algae and Bacteria

The present investigation showed by means of autoradiography that the cyanobacterium Microcystis wesenbergii did not incorporate [H]thymidine at nanomolar concentrations, whereas its associated heterotrophic bacteria appearing in the gelatinous cover of the cyanobacterium became labeled. Several other tested cyaobacteria and algae did not incorporate [H]thymidine.

β-Cyclocitral and Alkanes in Microcystis (Cyanophyceae)

Abstract A tobacco-like odorous compound isolated from a bloom of the blue-green alga Microcystis wesenbergii and a laboratory culture of M . aeruginosa was analysed by gas-liquid chromatography and mass spectrometry. Its structure was determined as β-cyclocitral. No other monoterpenes have been detected in these and in other blue-green algae. The hydrocarbon content was 0.10 - 0.18% of the dry weight. n-Hexadecane, n-heptadecane, 4-methylheptadecane and n-octadecane constituted the main components. The relation of the different alkanes to each other, especially 4-methylheptadecane and n-octadecane, revealed marked differences in the two organisms.