title: Environmental modulation of microcystin and β-N-methylamino-L-alanine as a function of nitrogen availability.
abstract: The most significant modulators of the cyanotoxins microcystin and β-N-methylamino-L-alanine in laboratory cyanobacterial cultures are the concentration of growth-medium combined nitrogen and nitrogen uptake rate. The lack of field studies that support these observations led us to investigate the cellular content of these cyanotoxins in cyanobacterial bloom material isolated from a freshwater impoundment and to compare these to the combined nitrogen availability. We established that these toxins typically occur in an inverse relationship in nature and that their presence is mainly dependent on the environmental combined nitrogen concentration, with cellular microcystin present at exogenous combined nitrogen concentrations of 29 μM and higher and cellular BMAA correlating negatively with exogenous nitrogen at concentrations below 40 μM. Furthermore, opposing nutrient and light gradients that form in dense cyanobacterial blooms may result in both microcystin and BMAA being present at a single sampling site.
authors.affiliation: Department of Biochemistry and Microbiology, Nelson Mandela Metropolitan University, PO Box 77 000, Port Elizabeth 6031, South Africa. Electronic address: Laura.Scott@nmmu.ac.za.
authors.forename: L L
authors.initials: LL
authors.lastname: Scott
authors.affiliation: Department of Biochemistry and Microbiology, Nelson Mandela Metropolitan University, PO Box 77 000, Port Elizabeth 6031, South Africa. Electronic address: Simone.Downing@nmmu.ac.za.
authors.forename: S
authors.initials: S
authors.lastname: Downing
authors.affiliation: Department of Biochemistry and Microbiology, Nelson Mandela Metropolitan University, PO Box 77 000, Port Elizabeth 6031, South Africa. Electronic address: Richard.Phelan2@nmmu.ac.za.
authors.forename: R R
authors.initials: RR
authors.lastname: Phelan
authors.affiliation: Department of Biochemistry and Microbiology, Nelson Mandela Metropolitan University, PO Box 77 000, Port Elizabeth 6031, South Africa; Institute for Ethnomedicine, P.O. Box 3464, Jackson, WY 83001, USA. Electronic address: Tim.Downing@nmmu.ac.za.
authors.forename: T G
authors.initials: TG
authors.lastname: Downing
mesh_terms: D000599:Amino Acids, Diamino / Q000378:metabolism*; D000641:Ammonia / Q000494:pharmacology; D002273:Carcinogens / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D000087522:Cyanobacteria Toxins; D004777:Environment; D005618:Fresh Water / Q000032:analysis; D052998:Microcystins / Q000378:metabolism*; D046931:Microcystis / Q000187:drug effects / Q000378:metabolism*; D009566:Nitrates / Q000494:pharmacology; D009573:Nitrites / Q000494:pharmacology; D009584:Nitrogen / Q000494:pharmacology*
chemical_list: D000599:Amino Acids, Diamino; D002273:Carcinogens; D000087522:Cyanobacteria Toxins; D052998:Microcystins; D009566:Nitrates; D009573:Nitrites; C001824:beta-N-methylamino-L-alanine; D002734:Chlorophyll; D000641:Ammonia; C078588:microcystin; D009584:Nitrogen; D000077194:Chlorophyll A
keywords: BMAA; Chlorophyll a; Microcystin; Nitrogen; β-N-Methylamino-L-alanine