Are We Underestimating Benthic Cyanotoxins? Extensive Sampling Results from Spain.

Microcystins (MCs) are potent hepatotoxins, and their presence in water bodies poses a threat to wildlife and human populations. Most of the available information refers to plankton, and much less is known about microcystins in other habitats. To broaden our understanding of the presence and environmental distribution of this group of toxins, we conducted extensive sampling throughout Spain, under a range of conditions and in distinct aquatic and terrestrial habitats. More than half of the tested strains were toxic; concentrations of the hepatotoxin were low compared with planktic communities, and the number of toxic variants identified in each sample of the Spanish strains ranged from 1-3. The presence of microcystins LF and LY (MC-LF and MC-LY) in the tested samples was significant, and ranged from 21.4% to 100% of the total microcystins per strain. These strains were only detected in cyanobacteria Oscillatoriales and Nostocales. We can report, for the first time, seven new species of microcystin producers in high mountain rivers and chasmoendolithic communities. This is the first report of these species in Geitlerinema and the confirmation of Anatoxin-a in Phormidium uncinatum. Our findings show that microcystins are widespread in all habitat types, including both aerophytic and endolithic peat bogs and that it is necessary to identify all the variants of microcystins in aquatic bodies as the commonest toxins sometimes represent a very low proportion of the total.

Effects of global change factors on fatty acids and mycosporine-like amino acid production in Chroothece richteriana (Rhodophyta).

Under natural conditions, Chroothece richteriana synthesizes a fairly high proportion of fatty acids. However, nothing is known about how environmental changes affect their production, or about the production of protective compounds, when colonies develop under full sunshine with high levels of UV radiation. In this study, wild colonies of C. richteriana were subjected to increasing temperature, conductivity, ammonium concentrations and photosynthetically active radiation (PAR), and UV radiations to assess the potential changes in lipid composition and mycosporine-like amino acids (MAAs) concentration. The PERMANOVA analysis detected no differences for the whole fatty acid profile among treatments, but the percentages of α-linolenic acid and total polyunsaturated fatty acids increased at the lowest assayed temperature. The percentages of linoleic and α-linolenic acids increased with lowering temperature. γ-linolenic and arachidonic acids decreased with increasing conductivity, and a high arachidonic acid concentration was related with increased conductivity. The samples exposed to UVB radiation showed higher percentages of eicosapentaenoic acid and total monounsaturated fatty acids, at the expense of saturated fatty acids. MAAs accumulation increased but not significantly at the lowest conductivity, and also with the highest PAR and UVR exposure, while ammonium and temperature had no effect. The observed changes are probably related with adaptations of both membrane fluidity to low temperature, and metabolism to protect cells against UV radiation damage. The results suggest the potential to change lipid composition and MAAs concentration in response to environmental stressful conditions due to climate change, and highlight the interest of the species in future research about the biotechnological production of both compound types.

Microcystins and cyanophyte extracts inhibit or promote the photosynthesis of fluvial algae. Ecological and management implications.

The ecological influence of cyanotoxins on aquatic biota remains unclear despite the numerous published references on toxicological and sanitary problems related with cyanophyte proliferation. The effects of microcystins and cyanophyte extracts on the photosynthesis of the algae that belong to two taxonomic groups, Rhodophyta and Bacillariophyta, were studied in an attempt to elucidate their role in the intraspecific competence and physiognomy of fluvial communities. The data showed that both cyanobacteria extracts and pure microcystin-LR affected the photosynthetic activity of all the tested organisms, diatoms (Fistulifera pelliculosa, Gomphonema parvulum, Nitzschia frustulum and Stephanodiscus minutulus) and red algae (Chroothece richteriana) at environmentally relevant concentrations. Effects varied with strains and time, and promoted or inhibited photosynthesis. The microcystins and the other compounds present in cyanobacteria extracts may explain the competence effects observed in nature, especially in calcareous environments where they predominate, and after disturbing events like heavy rains or floods, which may destroy cyanophyte mats and release toxic or inhibitory compounds in a seasonal scale pattern.

PARTIAL PURIFICATION AND CHARACTERIZATION OF A CALCIUM-DEPENDENT ALKALINE PHOSPHATASE FROM THE CYANOBACTERIUM ARTHROSPIRA PLATENSIS (1).

In the present study, Triton X-114 (TX-114) is used to extract and partially purify alkaline phosphatase (ALP) from a membranous fraction of Arthrospira platensis Gomont containing cell wall, plasma membrane, thylakoids, and sheath. TX-114 has a double effect: solubilizing cell components to liberate the enzyme and, after phase partitioning, removing chl and other pigments present in the crude extract. The recovery of the enzyme in the aqueous phase suggests the overall hydrophilic character of this enzyme. ALP was kinetically characterized at pH 11.0 using p-nitrophenyl phosphate as substrate, giving a Km value of 1.7 mM. Orthovanadate was seen to be a competitive inhibitor of ALP, with a Ki of 0.8 mM. The enzyme was almost completely inactivated in the presence of 70 µM EDTA, although the addition of Ca(2+) reverted this inactivation; these results indicate that ALP from A. platensis is a calcium-dependent metalloenzyme. When the effect of Ca(2+) was investigated in detail, a value of 0.067 µM(-1) for the affinity constant was obtained. The enzyme was histochemically localized in the cytoplasm, cell wall, and sheath using the enzyme-labeled fluorescent substrate (ELF) method. It is assumed that the same enzyme is either soluble in the cytoplasm and in some way "trapped" in the cell wall or in the sheath. ALP localization within the sheath and the subsequent release of phosphorus (P) may benefit the neighboring cells surrounding this layer.

RETRACTED: Carotenoids, Mycosporine-Like Amino Acid Compounds, Phycobiliproteins, And Scytonemin In The Genus Scytonema (Cyanobacteria): A Chemosystematic Study1.

The following article from the Journal of Phycology, "Carotenoids, Mycosporine-Like Amino Acid Compounds, Phycobiliproteins, And Scytonemin In The Genus Scytonema (Cyanobacteria): A Chemosystematic Study," submitted by Antonia D. Asencio, and published online on August 22, 2011 on Wiley Online Library (http://www.wileyonlinelibrary.com), has been retracted by agreement between the journal Editor, Robert Sheath, and Wiley Periodicals, Inc. The retraction has been agreed upon request by Ferran Garcia-Pichel, listed as co-author, but not having agreed to the submission or publication of the manuscript.