title: Changes in saxitoxin-production through growth phases in the metaphytic cyanobacterium Scytonema cf. crispum.
abstract: The cyanobacterium Scytonema cf. crispum produces a range of saxitoxins. Previous studies on other saxitoxin-producing cyanobacteria have shown that toxin production can vary throughout the growth cycle. Monitoring cyanotoxin-production in S. cf. crispum is challenging because it is metaphytic and has a very slow growth rate (ca. 6 months to reach stationary phase). In this study, a new method was developed to track growth and toxin production in S. cf. crispum. Samples were collected once a week for 131 days, and cell concentrations and saxitoxin quotas determined. Cells in the lag and exponential growth phases had significantly (P < 0.05) higher saxitoxin quotas (162 ± 37 fg cell(-1) and 139 ± 32 fg cell(-1), respectively) than the stationary phases (83 ± 19 fg cell(-1)). Extracellular saxitoxin concentrations were present at low concentrations (2-16 ng mL(-1) of culture medium) throughout the experiment. The proportion of extracellular saxitoxin to total saxitoxin decreased throughout the experiment. New knowledge on growth and saxitoxin variability will assist in improving monitoring, risk assessment and management of this species.
authors.affiliation: Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.
authors.forename: Francine
authors.initials: F
authors.lastname: Harland
authors.affiliation: Cawthron Institute, Private Bag 2, Nelson, New Zealand; University of Waikato, Private Bag 3015, Hamilton, New Zealand. Electronic address: Susie.wood@cawthron.org.nz.
authors.forename: Susanna A
authors.initials: SA
authors.lastname: Wood
authors.affiliation: School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.
authors.forename: Paul
authors.initials: P
authors.lastname: Broady
authors.affiliation: Environmental Science and Research Ltd, PO Box 29-181, Christchurch, New Zealand.
authors.forename: Wendy
authors.initials: W
authors.lastname: Williamson
authors.affiliation: Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch, New Zealand; Biomolecular Interaction Centre, School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand.
authors.forename: Sally
authors.initials: S
authors.lastname: Gaw
mesh_terms: D002851:Chromatography, High Pressure Liquid; D000458:Cyanobacteria / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D018570:Risk Assessment; D012530:Saxitoxin / Q000096:biosynthesis*; D014871:Water Microbiology
chemical_list: D012530:Saxitoxin
keywords: Cyanobacteria; Growth; Saxitoxin; Scytonema; Toxin-production