Ralf Kellmann

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Saxitoxin (STX) and its analogues cause the paralytic shellfish poisoning (PSP) syndrome, which afflicts human health and impacts coastal shellfish economies worldwide. PSP toxins are unique alkaloids, being produced by both prokaryotes and eukaryotes. Here we describe a candidate PSP toxin biosynthesis gene cluster (sxt) from Cylindrospermopsis raciborskii(More)
Saxitoxin is a potent neurotoxin that occurs in aquatic environments worldwide. Ingestion of vector species can lead to paralytic shellfish poisoning, a severe human illness that may lead to paralysis and death. In freshwaters, the toxin is produced by prokaryotic cyanobacteria; in marine waters, it is associated with eukaryotic dinoflagellates. However,(More)
Toxic cyanobacterial blooms cause economic losses and pose significant public health threats on a global scale. Characterization of the gene cluster for the biosynthesis of the cyanobacterial toxin cylindrospermopsin (cyr) in Cylindrospermopsis raciborskii AWT205 is described, and the complete biosynthetic pathway is proposed. The cyr gene cluster spans 43(More)
The cyanobacteria or "blue-green algae", as they are commonly termed, comprise a diverse group of oxygenic photosynthetic bacteria that inhabit a wide range of aquatic and terrestrial environments, and display incredible morphological diversity. Many aquatic, bloom-forming species of cyanobacteria are capable of producing biologically active secondary(More)
Saxitoxin and its analogues collectively known as the paralytic shellfish toxins (PSTs) are neurotoxic alkaloids and are the cause of the syndrome named paralytic shellfish poisoning. PSTs are produced by a unique biosynthetic pathway, which involves reactions that are rare in microbial metabolic pathways. Nevertheless, distantly related organisms such as(More)
The alkaloid cylindrospermopsin is the most recently discovered cyanotoxin and has caused epidemic outbreaks of human poisoning. Cylindrospermopsin producing cyanobacteria have in recent times appeared in countries all over the world where they had not been observed previously and, thus, represent a global public health concern. Three putative(More)
Marine dinoflagellates are the single most important group of algae that produce toxins, which have a global impact on human activities. The toxins are chemically diverse, and include macrolides, cyclic polyethers, spirolides and purine alkaloids. Whereas there is a multitude of studies describing the pharmacology of these toxins, there is limited or no(More)
The paralytic shellfish poisoning (PSP) toxins, saxitoxin, and its derivatives, are produced by a complex and unique biosynthetic pathway. It involves reactions that are rare in other metabolic pathways, however, distantly related organisms, such as dinoflagellates and cyanobacteria, produce these toxins by an identical pathway. Speculative explanations for(More)
The recent identification of genes involved in the production of the potent neurotoxin and keystone metabolite saxitoxin (STX) in marine eukaryotic phytoplankton has allowed us for the first time to develop molecular genetic methods to investigate the chemical ecology of harmful algal blooms in situ. We present a novel method for detecting and quantifying(More)