title: Phenotypic plasticity in freshwater picocyanobacteria.
abstract: Picocyanobacteria can occur as single-cell (Pcy) or as colonies (CPcy). Published evidence suggests that some Pcy strains have the capability to aggregate under certain culture conditions, however this has not been demonstrated to occur in natural environments. We investigated whether the Pcy and CPcy belong to the same species (i.e. phylotype), and the factors that determine their morphological and genetic variability in a hypertrophic shallow lake dominated by picocyanobacteria. Six main different morphologies and >30 phylotypes were observed. All sequences retrieved belonged to the 'Anathece + Cyanobium' clade (Synechococcales) that are known to have the capability of aggregation/disaggregation. The temporal variation of picocyanobacteria morphotype composition was weakly correlated with the DGGE temporal pattern, and could be explained by the composition of the zooplankton assemblage. Laboratory experiments confirmed that the small cladoceran Bosmina favoured the dominance of CPcy, i.e. Cyanodictyon doubled the size of the colonies when present, most likely through the aggregation of single-cell picocyanobacteria into colonies. Flow cytometry cell sorting and 16S rRNA + ITS sequencing of the Pcy and CPcy cytometrically-defined populations revealed that some phylotypes could be found in both sorted populations, suggesting phenotypic plasticity in which various Synechococcales phylotypes could be found in situ either as single-cells or as colonies.
authors.affiliation: Instituto de Investigaciones Biotecnológicas-Instituto Tecnológico de Chascomús (IIB-INTECH), UNSAM-CONICET, Av. Intendente Marino Km 8.200, (B 7130 IWA) Chascomús, Buenos Aires, Argentina.
authors.forename: Paula
authors.initials: P
authors.lastname: Huber
authors.affiliation: Instituto de Investigaciones Biotecnológicas-Instituto Tecnológico de Chascomús (IIB-INTECH), UNSAM-CONICET, Av. Intendente Marino Km 8.200, (B 7130 IWA) Chascomús, Buenos Aires, Argentina.
authors.forename: Nadia
authors.initials: N
authors.lastname: Diovisalvi
authors.affiliation: Instituto de Investigaciones Biotecnológicas-Instituto Tecnológico de Chascomús (IIB-INTECH), UNSAM-CONICET, Av. Intendente Marino Km 8.200, (B 7130 IWA) Chascomús, Buenos Aires, Argentina.
authors.forename: Marcela
authors.initials: M
authors.lastname: Ferraro
authors.affiliation: Instituto de Investigaciones Biotecnológicas-Instituto Tecnológico de Chascomús (IIB-INTECH), UNSAM-CONICET, Av. Intendente Marino Km 8.200, (B 7130 IWA) Chascomús, Buenos Aires, Argentina.
authors.forename: Sebastián
authors.initials: S
authors.lastname: Metz
authors.affiliation: Instituto de Investigaciones Biotecnológicas-Instituto Tecnológico de Chascomús (IIB-INTECH), UNSAM-CONICET, Av. Intendente Marino Km 8.200, (B 7130 IWA) Chascomús, Buenos Aires, Argentina.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Lagomarsino
authors.affiliation: Instituto de Investigaciones Biotecnológicas-Instituto Tecnológico de Chascomús (IIB-INTECH), UNSAM-CONICET, Av. Intendente Marino Km 8.200, (B 7130 IWA) Chascomús, Buenos Aires, Argentina.
authors.forename: María Eugenia
authors.initials: ME
authors.lastname: Llames
authors.affiliation: Departament de Biologia Marina i Oceanografia, Institut de Ciències del Mar, CSIC, Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Catalonia, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Royo-Llonch
authors.affiliation: Instituto de Investigaciones Biotecnológicas-Instituto Tecnológico de Chascomús (IIB-INTECH), UNSAM-CONICET, Av. Intendente Marino Km 8.200, (B 7130 IWA) Chascomús, Buenos Aires, Argentina.
authors.forename: José
authors.initials: J
authors.lastname: Bustingorry
authors.affiliation: Instituto de Investigaciones Biotecnológicas-Instituto Tecnológico de Chascomús (IIB-INTECH), UNSAM-CONICET, Av. Intendente Marino Km 8.200, (B 7130 IWA) Chascomús, Buenos Aires, Argentina.
authors.forename: Roberto
authors.initials: R
authors.lastname: Escaray
authors.affiliation: Departament de Biologia Marina i Oceanografia, Institut de Ciències del Mar, CSIC, Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Catalonia, Spain.
authors.forename: Silvia G
authors.initials: SG
authors.lastname: Acinas
authors.affiliation: Departament de Biologia Marina i Oceanografia, Institut de Ciències del Mar, CSIC, Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Catalonia, Spain.
authors.forename: Josep M
authors.initials: JM
authors.lastname: Gasol
authors.affiliation: Instituto de Investigaciones Biotecnológicas-Instituto Tecnológico de Chascomús (IIB-INTECH), UNSAM-CONICET, Av. Intendente Marino Km 8.200, (B 7130 IWA) Chascomús, Buenos Aires, Argentina.
authors.forename: Fernando
authors.initials: F
authors.lastname: Unrein
mesh_terms: D044822:Biodiversity; D000458:Cyanobacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D060106:Lakes / Q000382:microbiology*; D010641:Phenotype; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics
chemical_list: D012336:RNA, Ribosomal, 16S