RESUMEN
We report here the draft genome assembly of the brackish cyanobacterium Nodularia spumigena strain CENA596 isolated from a shrimp production pond in Rio Grande do Sul, Brazil. The draft genome consists of 291 contigs with a total size of 5,189,679 bp. Secondary metabolite annotations resulted in several predicted gene clusters, including those responsible for encoding the hepatotoxin nodularin.
RESUMEN
Raphidiopsis brookii P. J. Hill (cyanobacteria) was isolated from a small subtropical eutrophic pond (Biguá Pond) located in the grounds of Rio Grande University in the extreme south of Brazil, following a toxic bloom of this species. Growth, saxitoxin production, and release of carbohydrates and protein were monitored at three sodium nitrate concentrations (500, 1,000, and 1,500 µM), from inoculation up to the stationary growth phase. Growth was monitored by determining the biovolume, chl content, and trichome count. Growth was better described in terms of biovolume and chl measurements, because trichome fragmentation was observed to increase at the stationary growth phase. Carbohydrates and proteins were released in small amounts during most of the experiment, with a significant increase during the stationary phase. Extracellular polysaccharides were essentially composed of glucose, galactose, N-acetyl-glucosamine, mannose, xylose, rhamnose, arabinose, and fucose. The relative proportions of these units showed no significant variation during growth. Small quantities of extracellular free carbohydrates were also detected, and only fucose was released in significant amounts at the lowest nitrate concentration (500 µM). R. brookii produced both saxitoxin and dc-saxitoxin, the former at four times the rate of the latter. This was the first study demonstrating saxitoxin production and the release of both carbohydrate and protein by R. brookii.