title: Spatiotemporal changes in the genetic diversity of a bloom-forming Microcystis aeruginosa (cyanobacteria) population.
abstract: The variations in microcystin concentrations during cyanobacterial blooms in freshwater ecosystems appear to depend on numerous factors, which have still not been fully identified. To contribute to clarify the situation, we have developed a spatial sampling approach to determine the dynamics and genetic diversity of a bloom-forming population of Microcystis aeruginosa in a large French reservoir, and the variations in the proportions of microcystin-producing genotypes. We demonstrated that marked changes occurred in the internal transcribed spacer (ITS) genotype composition of the M. aeruginosa population during the development of the bloom. These changes led progressively to the selection of one dominant ITS genotype throughout the entire reservoir when the cell number reached its maximum. At the same time, we identified a decrease in the proportion of the mcyB+ genotype, and a significant negative correlation between this proportion and that of the dominant ITS genotype during the bloom. Thus, it appeared that favorable conditions for Microcystis cell growth led to the selection, within the Microcystis population, of a non-microcystin-producing genotype, whereas potentially microcystin-producing genotypes were dominant in this population before and after the bloom, when environmental conditions were less favorable for growth.
authors.affiliation: MNHN, USM505/EA4105 Ecosystèmes et interactions toxiques, Paris Cedex 05, France.
authors.forename: Enora
authors.initials: E
authors.lastname: Briand
authors.forename: Nicolas
authors.initials: N
authors.lastname: Escoffier
authors.forename: Cécile
authors.initials: C
authors.lastname: Straub
authors.forename: Marion
authors.initials: M
authors.lastname: Sabart
authors.forename: Catherine
authors.initials: C
authors.lastname: Quiblier
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Humbert
mesh_terms: D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D005602:France; D005618:Fresh Water / Q000382:microbiology*; D014644:Genetic Variation; D005843:Geography; D052998:Microcystins / Q000235:genetics; D046931:Microcystis / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D013997:Time Factors
chemical_list: D004269:DNA, Bacterial; D021903:DNA, Ribosomal Spacer; D052998:Microcystins; C078588:microcystin