Microcystis toxigenic strains in urban lakes: a case of study in Mexico City.

Microcystis is a bloom-forming, common cyanobacterium in urban lakes of Mexico City. To assess the presence of potentially cyanotoxin-producing Microcystis, molecular techniques were applied and acute toxicity bioassays were performed with Daphnia magna neonates exposed to cyanobacterial crude extracts. Toxigenic potential of isolated strains was inferred by amplifying the mcyA-Cd genes and their identity as Microcystis was confirmed through the 16S rDNA and phycocyanin operon amplification. Microcystins synthesized under culture conditions were quantified through ELISA. The acute toxicity bioassays revealed that mortality was independent from the cyanotoxin concentration in some strains; this suggests the presence of other metabolites (different from microcystins) that also exerted an important biological effect. Isolated strains had the mcyA-Cd gene and most of them produced variable amounts of microcystins in the culture conditions used, confirming their toxigenic potential. Results warn about possible toxic effect risks for aquatic biota, neighboring areas, visitors and users of these sites, due to the constant presence of these blooms in the studied water bodies.

Detection, isolation, and characterization of exopolysaccharide produced by a strain of Phormidium 94a isolated from an arid zone of Mexico.

Phormidium 94a, a cyanobacteria that produces extracellular polymeric substances (EPS), was isolated from arid soils of Mexico. Microscopic localization, using histochemical techniques like the Toluidine blue technique, was done in order to demonstrate the presence of EPS. Acetone was added to precipitate the EPS. In this study we characterized the EPS by GC, HPLC, and IR techniques. The highest fraction of EPS had a molecular weight of 2000 kDa. The sugar composition was galactose, mannose, galacturonic acid, arabinose, and ribose in the three main fractions, and the sugar ratio found was different in each fraction. The low EPS concentrations had a Newtonian behavior, when the concentrations were increased, the behavior changed to pseudoplastic. The EPS rheulogical behavior is similar to low viscosity arabic gum. Also, it was found that an increase in viscosity occurred at longer hydration time. More rheological and toxicological studies are required in order to analyze its possible application in food industries.

Uso tradicional y actual de spirulina sp. (arthrospira sp.) / Traditional and present use of spirulina sp. (arthrospira sp.)

Spirulina sp. (Arthrospira sp.) es una cianobacteria filamentosa no diferenciada, habitante de lagos alcalinos, que se cultiva para consumo humano debido a su contenido nutricional. En México, el consumo de esta cianobacteria se remonta a tiempos prehispánicos, cuando era conocida como tecuitlatl, siendo conocida como dihé por las tribus nativas de la región del lago de Chad, en Africa. En los últimos años se le han atribuido diversos efectos positivos en el tratamiento de algunos tipos de alergias, anemia, cáncer, enfermedades virales y cardiovasculares. Muchas de sus propiedades son consecuencia de la presencia de pigmentos como las ficobiliproteínas y los carotenoides, así como de otros compuestos como polisacáridos, ácidos grasos (destacando el ácido gama linoleico), proteínas, vitaminas y minerales. Las propiedades y aplicaciones de este organismo hacen de él un alimento promotor de la salud o nutracéutico