title: Evidence for differences in the metabolism of saxitoxin and C1+2 toxins in the freshwater cyanobacterium Cylindrospermopsis raciborskii T3.
abstract: The activity of paralytic shellfish poisoning (PSP) toxins biosynthetic enzymes was assayed in the cyanobacterium Cylindrospermopsis raciborskii T3 after inhibiting protein synthesis with chloramphenicol (CAM). The production of C1+2 and saxitoxin (STX) was sensitive to CAM with STX levels decreasing by 70% after 24-h exposure to the antibiotic. PSP toxin production was strongly promoted by arginine supplementation, with a maximum 476% increase in intracellular STX concentrations after 24-h exposure to 10 mM of the amino acid. However, arginine had no stimulating effect on PSP toxin levels if supplemented in combination with CAM at 10 microg l(-1). Addition of agmatine and proline to C. raciborskii T3 cultures in the presence of 10 microg l(-1) CAM increased C1+2 toxins levels, while having a negative or no effect on STX accumulation. In vitro, PSP toxin levels increased naturally in cyanobacterial extracts, with CAM and arginine having no influence on either C1+2 or STX synthesis. The evidence presented in this study suggests a possible difference between the metabolism of STX and the C1+2 toxins and indicated a high turnover rate of STX biosynthetic enzymes in C. raciborskii T3.
authors.affiliation: Environmental Research Group, DBSF University of Insubria, 21100 Varese, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Pomati
authors.forename: Michelle C
authors.initials: MC
authors.lastname: Moffitt
authors.forename: Rosalia
authors.initials: R
authors.lastname: Cavaliere
authors.forename: Brett A
authors.initials: BA
authors.lastname: Neilan
mesh_terms: D000376:Agmatine / Q000378:metabolism; D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism; D002701:Chloramphenicol / Q000494:pharmacology; D000458:Cyanobacteria / Q000187:drug effects / Q000378:metabolism*; D005618:Fresh Water; D008387:Marine Toxins / Q000737:chemistry / Q000378:metabolism*; D015394:Molecular Structure; D011392:Proline / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012530:Saxitoxin / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D008387:Marine Toxins; D011500:Protein Synthesis Inhibitors; D012530:Saxitoxin; D002701:Chloramphenicol; D000376:Agmatine; D011392:Proline