Detection of the neurotoxin BMAA within cyanobacteria isolated from freshwater in China

Abstract

The cyanobacterial neurotoxin, β-N-methylamino- l -alanine (BMAA), has been suggested as an important environmental factor for neurodegenerative disease such as amyotrophic lateral sclerosis- Parkinsonism dementia complex (ALS/PDC) in Guam. BMAA was detected within the majority of cyanobacterial isolates surveyed in both free and symbiotic cyanobacteria, living in freshwater as well as marine environments. In this study, we report two methods using liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS/MS) each coupled with a different type of hydrophilic interaction liquid chromatography (HILIC) column to detect BMAA. A third method using AQC-derivatized BMAA was also used for comparison. Axenic cultures of Microcystis aeruginosa and Nostoc sp. isolated from Chinese freshwater were analyzed for both free and protein-bound BMAA at the exponential growth stage. Cultures of two strains of M. aeruginosa collected at four growth stages were also analyzed for the presence of BMAA. BMAA was detected in the Nostoc sp. at very low concentrations (<0.07 pmoles on column) only when precolumn AQC derivatization was used. No BMAA was detected in the Chinese derived axenic cultures of Microcystis; detection limits for the LC-ESI-MS and LC-ESI-MS/MS without precolumn derivatization were 10 ng and 2 pg BMAA on column, respectively. We suggest that cyanobacteria grown under some culture conditions may be relatively free of BMAA.