title: Effects of microcystins on and toxin degradation by Poterioochromonas sp.
abstract: A Chrysophyceae species, Poterioochromonas sp., was isolated from Microcystis cultures. This species can efficiently prey on Microcystis and can grow faster phagotrophically than autotrophically. The growth of Poterioochromonas sp. was stimulated in the presence of microcystin-LR and microcystin-RR (in concentrations ranging from 0.1 to 4 mg/L). The growth rate of Poterioochromonas was 4-5 times higher than the control, indicating the toxins serve as growth stimuli for this organism. A subculture of toxin-treated cells, however, showed low cellular viability, suggesting that growth enhancement by microcystins was not a normal process. The antioxidant enzymatic activity of Poterioochromonas sp. was screened for toxicology analysis. Glutathione, malondialdehyde, and superoxide dismutase (SOD) content was up-regulated within 8 h of exposure to microcystin-LR (500 microg/L). A high level of SOD activity during exposure to the toxin indicated that SOD was involved in decreasing oxidative stress caused by microcystin-LR. Simultaneously with growth, Poterioochromonas was able to degrade microcystin-LR even, at a toxin concentration of 4 mg/L. This putative degradation mechanism in Poterioochromonas is explored further and discussed in this article. Our findings may shed light on understanding the role of Poterioochromonas in the aquatic ecosystem, in particular, as a grazer of toxic cyanobacteria and a biodegrader for microcystins.
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072, People's Republic of China.
authors.forename: Danyun
authors.initials: D
authors.lastname: Ou
authors.forename: Lirong
authors.initials: L
authors.lastname: Song
authors.forename: Nanqin
authors.initials: N
authors.lastname: Gan
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
mesh_terms: D001673:Biodegradation, Environmental; D044523:Chrysophyta / Q000201:enzymology / Q000254:growth & development*; D000458:Cyanobacteria / Q000737:chemistry / Q000472:pathogenicity; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology*; D008387:Marine Toxins; D052998:Microcystins; D010456:Peptides, Cyclic / Q000378:metabolism / Q000494:pharmacology*; D013482:Superoxide Dismutase / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D004791:Enzyme Inhibitors; D008387:Marine Toxins; D052998:Microcystins; D010456:Peptides, Cyclic; C063855:microcystin RR; D013482:Superoxide Dismutase; C057862:cyanoginosin LR