Characterization and potential antitumor effect of a heteropolysaccharide produced by the red alga Porphyridium sordidum

Taking into account the rising trend of the incidence of cancers of various organs, effective therapies are urgently needed to control human malignancies. However, almost all chemotherapy drugs currently on the market cause serious side effects. Fortunately, several studies have shown that some non‐toxic biological macromolecules, including algal polysaccharides, possess anti‐cancer activities or can increase the efficacy of conventional chemotherapy drugs. Polysaccharides are characteristic secondary metabolites of many algae. The efficacy of polysaccharides on the normal and cancer cells is not well investigated, but our investigations proved a cell specific effect of a newly isolated extracellular polysaccharide from the red microalga Porphyridium sordidum. The investigated substance was composed of xylose:glucose and galactose:manose:rhamnose in a molar ratio of 1:0.52:0.44:0.31. Reversible electroporation has been exploited to increase the transport through the plasma membrane into the tested breast cancer tumor cells MCF‐7 and MDA‐MB231. Application of 75 µg/mL polysaccharide in combination with 200 V/cm electroporation induced 40% decrease in viability of MDA‐MB231 cells and changes in cell morphology while control cells (MCF10A) remained with normal morphology and kept vitality.     

Circumtropical distribution of the epiphytic dinoflagellate Coolia malayensis (Dinophyceae): Morphology and molecular phylogeny from Puerto Rico and Brazil

The dinoflagellate genus Coolia, which contains potentially toxic species, is an important component of epiphytic assemblages in marine ecosystems. The morphology of C. malayensis has been illustrated from strains isolated in Asia and Oceania. In this study, strains of C. malayensis isolated from the Caribbean Sea in Puerto Rico, and for the first time from the South Atlantic Ocean in Brazil, were investigated by light, epifluorescence and scanning electron microscopies. No significant morphological differences between these new strains and other geographically distant strains of C. malayensis were observed. In the LSU rDNA phylogeny, the C. malayensis sequences from Brazil and Puerto Rico branched within the clade of strains from Oceania and Asia. The recently described species C. santacroce branched as a sister group of C. monotis, and C. palmyrensis was basal to the combined group of C. monotis/C. malayensis/C. santacroce. A tentative undescribed species from Florida and New Zealand branched as a sister group of C. malayensis. Our results confirm that C. malayensis showed a cosmopolitan distribution in tropical to subtropical waters, while the type species C. monotis remains endemic for the Mediterranean Sea and the temperate North Atlantic.     

微藻与细菌作用关系的研究进展

藻类是水生环境中的初级生产者,它的生长常常伴随着细菌并受菌的影响。有研究者指出藻类和细菌有着密不可分的关系。一些研究表明与藻相关的主体细菌是特定的细菌群体,特别是α-变形菌频繁地发现,说明这类菌可能能够开启和维持共生关系。最近的研究提出了营养物质交换是菌藻共生的基础,这类相关化合物是复杂的和特定的分子,可能参与信号处理和监控作用,而不只是被动扩散。同时,这种作用很明显不是静态的,它的开启和终止可能是对环境和发育的响应。需要指出的是明确菌藻关系的作用机理还有待于进一步的深入研究,本篇综述结合新提出的理论,对细菌与微藻作用关系的研究进展进行总结,概括了微藻与菌的作用关系(进化关系,营养依赖,代谢互补和协作生物合成),这种作用关系涉及到的菌的分类(膜菌和藻际微环境菌,促生菌PGPB和溶藻菌)以及菌藻作用的应用(废水处理和生物燃料生产)的情况,并对菌藻关系的未来发展做了展望。     

Eutrophication in Australian Rivers, Reservoirs and Estuaries – A Southern Hemisphere Perspective on the Science and its Implications

Australian science has made rapid advances in the last decade in understanding eutrophication processes in inland waters and estuaries. The freshwater research on which these advances are based was triggered by well-publicised blooms of cyanobacteria during the 1980s and early 1990s, particularly a 1000 km long bloom on the Darling River. In estuaries the study which greatly enhanced our understanding but simultaneously served to stimulate further research into estuarine eutrophication, the Port Phillip Bay Study, was initially designed to address perceived problems of toxicants in the Bay but provided profound insights into drivers for, and ecosystem responses to, eutrophication. Subsequent estuarine research has largely been stimulated by management questions arising from Australia’s increasing coastal development for residential purposes. The research has shown that some of the beliefs extant at the time of the blooms were incorrect. For example, it is now clear that stratification and light penetration, not nutrient availability, are the triggers for blooms in the impounded rivers of southeastern Australia, although nutrient exhaustion limits the biomass of blooms. Again, nitrogen seems to play as important a role as phosphorus does in controlling the biomass of these freshwater blooms. The research has also shown that aspects of eutrophication, such as nutrient transport, are dominated by different processes in different parts of Australia. Many of the biophysical processes involved in eutrophication have now been quantified sufficiently for models to be developed of such processes as sediment-nutrient release, stratification, turbidity and algal growth in both freshwater and estuarine systems. In some cases the models are reliable enough for the knowledge gained in particular waterbodies to be applied elsewhere. Thus, there is now a firm scientific foundation for managers to rely upon when managing algal blooms. Whilst these findings have already been presented to managers and communities throughout Australia, there is still a considerable way to go before they are absorbed into their modus operandi.     

Modulation and adaptation of carbonic anhydrase activity in Microcystis spp. under different environmental factors

The carbonic anhydrase (CA) activities were determined in three cyanobacterial species, namely Microcystis aeruginosa Kütz., Microcystis viridis (A.Br.) Lemm, and Microcystis wesenbergii (Kom.) Kom, which were dominant in a lake (Dianchi Lake) subject to major blooms. In more detailed experiments on M. aeruginosa, the effects of inorganic carbon, pH, temperature, nitrogen/phosphorus ratio, glucose, and light intensity on CA activity were also investigated. Because of the relatively alkaline pH value of the culture media for the optimum growth of algal cells, bicarbonate ions were the main form of exogenous inorganic carbon. The results showed that the CA activity of M. aeruginosa was influenced dramatically by the concentration of bicarbonate. Consequently, it was suggested that bicarbonate ions were the main form of exogenous inorganic carbon that M. aeruginosa could utilize. Cultures grown in the dark exhibited CA activity six times higher than that of cells cultured mixotrophically with the addition of glucose. Features of eutrophic water bodies promoted an increase in CA activity, and the resulting higher CA activity would accelerate the utilization of inorganic carbon and favor the growth and blooming of Microcystis spp. in eutrophic lakes. Although the experiments were carried out under controlled experimental conditions, they could provide some basic data that would prove useful for the control of cyanobacterial blooms in nature.     

MORPHOLOGICAL AND MOLECULAR CHARACTERIZATION OF PLANKTONIC CYANOBACTERIA FROM BELGIUM AND LUXEMBOURG1

For the first time in Belgium and Luxembourg, the diversity and taxonomy of 95 cyanobacterial strains isolated from freshwater blooms were assessed by the comparison of phenotypes and partial 16S rRNA gene sequences. The results showed the high diversity of nanoplanktonic, picoplanktonic, and benthic–periphytic cyanobacteria accompanying the main bloom‐forming taxa. Indeed, besides 15 morphotypes of bloom‐forming taxa, seven non‐bloom‐forming planktonic morphotypes and 11 morphotypes from benthic–periphytic taxa were isolated in culture from the plankton samples of 35 water bodies. The bloom‐forming strains belonged to the genera Microcystis, Woronichinia, Planktothrix, Anabaena, and Aphanizomenon, whereas the other strains isolated from the same samples were assigned to the nanoplanktonic Aphanocapsa, Aphanothece, Snowella, and Pseudanabaena; to the picoplanktonic Cyanobium; and to the benthic–periphytic Geitlerinema, Komvophoron, Leptolyngbya, Lyngbya, Phormidium, Calothrix, Nostoc, and Trichormus. The results supported both the polyphyletism of genera such as Aphanocapsa, Aphanothece, Leptolyngbya, Geitlerinema, Anabaena, and Aphanizomenon as well as the validity of genera such as Microcystis, Planktothrix, and Pseudanabaena with gas vesicles and cells constricted at the cross wall. The results obtained showed the close relationship between Snowella and Woronichinia for which very few sequences exist. The first sequence of Komvophoron appeared poorly related to other available cyanobacterial sequences. Although in a few cases a good agreement existed between phenotypic and genotypic features, there was generally a discrepancy. Strains with identical morphotypes show small differences in the 16S rRNA sequences, which might be related to the different chemical properties of their habitats. The results showed the importance of the polyphasic approach in order to improve the taxonomy of cyanobacteria.     

BIOVOLUME CALCULATION FOR PELAGIC AND BENTHIC MICROALGAE

Microalgal biovolume is commonly calculated to assess the relative abundance (as biomass or carbon) of co-occurring algae varying in shape and/or size. However, a standardized set of equations for biovolume calculations from microscopically measured linear dimensions that includes the entire range of microalgal shapes is not available yet. In comparison with automated methods, the use of microscopical measurements allows high taxonomic resolution, up to the species level, and has fewer sources of error. We present a set of geometric shapes and mathematical equations for calculating biovolumes of >850 pelagic and benthic marine and freshwater microalgal genera. The equations are designed to minimize the effort of microscopic measurement. The similarities and differences between our proposal for standardization and previously published proposals are discussed and recommendations for quality standards given.     

Turbulence, watermass stratification and harmful algal blooms: an alternative view and frontal zones as “pelagic seed banks”

Watermass stratification has been considered the essential physical condition that dinoflagellates require to bloom because of their relative inability, unlike diatoms, to tolerate the elevated shear-stress associated with water-column mixing, turbulence and high velocity, coastal currents. The swimming speeds of 71 flagellate taxa, with a focus on dinoflagellates, are compared to the turbulence fields and vertical velocities that develop during representative wind conditions, upwelling and at frontal zones. The results suggest that the classical stratification–dinoflagellate bloom paradigm needs revision. Tolerance of turbulence, growth within well-mixed watermasses and survival and dispersal while entrained within current systems are well developed capacities among dinoflagellates. Their secretion of mucous, often copious during blooms, is suggested to be an environmental engineering strategy to dampen turbulence. Biophysical tolerance of turbulence by dinoflagellates is often accompanied by high swimming speeds. Motility speeds of many species exceed in situ vertical current velocities; this also allows diel migrational patterns and other motility-based behavior to persist. Species belonging to “mixing-drift” life-form assemblages can increase their swimming speeds through chain formation, which helps to compensate for the increased turbulence and vertical water-column velocities of their habitats. The ability of dinoflagellate species to tolerate the vertical velocities of offshore, frontal zones, where abundant populations often develop, suggests that fronts may serve as “pelagic seed banks”, occurring as pelagic analogues of nearshore seed beds, from which seed stock is dispersed. The different ecologies associated with the hypothesized, “pelagic seed banks” of vegetative cells and the “seed beds” of resting stage cells deposited onto sediments are discussed. There is a contradiction in the stratification–HAB paradigm: the quiescent conditions of a stratified watermass, with its characteristic nutrient-poor conditions are expected to promote stasis of the population, rather than growth and blooms. The analyses suggest that dinoflagellate blooms do not preponderate in stratified watermasses because the bloom species are biophysically intolerant of the higher velocities and turbulence of more mixed watermasses. The watermass stratification that often accompanies flagellate blooms is probably a secondary, parallel event and less essential than some other factor(s) in triggering the observed bloom.