title: Quantification of toxic Microcystis and evaluation of its dominance ratio in blooms using real-time PCR.
abstract: Microcystins are produced by cyanobacteria carrying microcystin synthetase (mcy) genes in blooms. The present study investigated seasonal variations in concentrations of mcy A and 16S rRNA genes, encoded in the genus Microcystis using real-time PCR, and measured the water quality variables and microcystin concentrations in a hypereutrophic fish pond between June and November 2007. Prior to field survey, the relationship between axenic Microcystis aeruginosa NIES 102 cell abundance and concentrations of mcy A and 16S rRNA genes was determined by real-time PCR in the laboratory. Based on the quantitative relationship, microcystin-producing and total Microcystis cell numbers in the study site were estimated. The average dominance ratio of microcystin-producing strains in the total Microcystis population was approximately 80% and microcystin concentration was highly associated with toxic Microcystis cell numbers equivalent of mcy A gene. It was also observed that total nitrogen concentration was associated with development of Microcystis blooms, and high concentrations of NOx and NH4 increased microcystin production by promoting growth of microcystin-producing Microcystis strains.
authors.affiliation: Department of Urban and Environmental Engineering, Kyoto University, Kyoto-Daigaku-Katsura, Nishikyo-ku, Kyoto 615-8540, Japan. jhha@water.mbox.media.kyoto-u.ac.jp
authors.forename: Joo H
authors.initials: JH
authors.lastname: Ha
authors.forename: Taira
authors.initials: T
authors.lastname: Hidaka
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tsuno
mesh_terms: D001483:Base Sequence; D017931:DNA Primers; D052998:Microcystins / Q000032:analysis / Q000633:toxicity; D046931:Microcystis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D016133:Polymerase Chain Reaction
chemical_list: D017931:DNA Primers; D052998:Microcystins