title: Dynamics of microcystin-producing and non-microcystin-producing Microcystis populations is correlated with nitrate concentration in a Japanese lake.
abstract: Temporal changes in hepatotoxin microcystin-producing and non-microcystin-producing Microcystis aeruginosa populations were examined in Lake Mikata, Japan. To monitor the densities of the total M. aeruginosa population and the potential microcystin-producing subpopulation, we used a quantitative real-time PCR assay targeting the phycocyanin intergenic spacer and the microcystin synthetase gene (mcyA), respectively. During the sampling period, the ratio of the mcyA subpopulation to the total M. aeruginosa varied considerably, from 0.5% to 35%. When surface nitrate concentrations increased, there was a rise in the relative abundance of the mcyA subpopulation. This was a positive correlation with the nitrate concentrations (r=0.53, P<0.05, n=14); whereas temperature and ortho-phosphate had no significant correlation with the presence of mcyA. Our data suggest that high nitrate loading may be a significant factor promoting the growth of the microcystin subpopulations within M. aeruginosa communities in Lake Mikata.
authors.affiliation: Department of Marine Bioscience, Fukui Prefectural University, Obama-City, Fukui, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Yoshida
authors.forename: Takashi
authors.initials: T
authors.lastname: Yoshida
authors.forename: Yukari
authors.initials: Y
authors.lastname: Takashima
authors.forename: Naohiko
authors.initials: N
authors.lastname: Hosoda
authors.forename: Shingo
authors.initials: S
authors.lastname: Hiroishi
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D021901:DNA, Intergenic / Q000737:chemistry; D005618:Fresh Water / Q000737:chemistry / Q000382:microbiology*; D005838:Genotype; D007564:Japan; D052998:Microcystins / Q000096:biosynthesis* / Q000235:genetics; D046931:Microcystis / Q000145:classification / Q000378:metabolism*; D009566:Nitrates / Q000032:analysis*; D010453:Peptide Synthases / Q000235:genetics; D010798:Phycocyanin / Q000235:genetics; D016133:Polymerase Chain Reaction; D011156:Population Density; D011157:Population Dynamics
chemical_list: D001426:Bacterial Proteins; D021901:DNA, Intergenic; D052998:Microcystins; D009566:Nitrates; D010798:Phycocyanin; C078588:microcystin; D010453:Peptide Synthases; C432283:microcystin synthetase A