title: Microcystin production by Microcystis aeruginosa in a phosphorus-limited chemostat.
abstract: The production of microcystins (MC) from Microcystis aeruginosa UTEX 2388 was investigated in a P-limited continuous culture. MC (MC-LR, MC-RR, and MC-YR) from lyophilized M. aeruginosa were extracted with 5% acetic acid, purified by a Sep-Pak C(18) cartridge, and then analyzed by high-performance liquid chromatography with a UV detector and Nucleosil C(18) reverse-phase column. The specific growth rate (mu) of M. aeruginosa was within the range of 0.1 to 0.8/day and was a function of the cellular P content under a P limitation. The N/P atomic ratio of steady-state cells in a P-limited medium varied from 24 to 15 with an increasing mu. The MC-LR and MC-RR contents on a dry weight basis were highest at mu of 0.1/day at 339 and 774 microg g(-1), respectively, while MC-YR was not detected. The MC content of M. aeruginosa was higher at a lower mu, whereas the MC-producing rate was linearly proportional to mu. The C fixation rate at an ambient irradiance (160 microeinsteins m(-2) s(-1)) increased with mu. The ratios of the MC-producing rate to the C fixation rate were higher at a lower mu. Accordingly, the growth of M. aeruginosa was reduced under a P limitation due to a low C fixation rate, whereas the MC content was higher. Consequently, increases in the MC content per dry weight along with the production of the more toxic form, MC-LR, were observed under more P-limited conditions.
authors.affiliation: Environmental Microbiology Research Unit, Korea Research Institute of Bioscience and Biotechnology, Yusong, Taejon 305-600, Korea. heemock@mail.kribb.re
authors.forename: H M
authors.initials: HM
authors.lastname: Oh
authors.forename: S J
authors.initials: SJ
authors.lastname: Lee
authors.forename: M H
authors.initials: MH
authors.lastname: Jang
authors.forename: B D
authors.initials: BD
authors.lastname: Yoon
mesh_terms: D003470:Culture Media / Q000737:chemistry; D052998:Microcystins; D046931:Microcystis / Q000254:growth & development / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism; D010456:Peptides, Cyclic / Q000096:biosynthesis; D010758:Phosphorus / Q000378:metabolism; D010788:Photosynthesis
chemical_list: D003470:Culture Media; D052998:Microcystins; D010456:Peptides, Cyclic; D010758:Phosphorus; C078588:microcystin; D009584:Nitrogen