Phenotypic plasticity in freshwater picocyanobacteria

HUBER, P.; DIOVISALVI, N.; FERRARO, M.; METZS,S.; LAGOMARSINO, L.; LLAMES, M.; ROYO LLONCH, M.; BUSTINGORRY, J.; ESCARAY, R.; ACINAS,S.; GASOL, J.; UNREIN, F.

ENVIRONMENTAL MICROBIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016

1462-2912

Picocyanobacteria can occur as single-cell (Pcy) or as colonies (CPcy).Published evidence suggests that some Pcy strains have the capability toaggregate under certain culture conditions, however this has not beendemonstrated to occur in natural environments. We investigated whether thePcy and CPcy belong to the same species (i.e. phylotype), and the factorsthat determine their morphological and genetic variability in a hypertrophicshallow lake dominated by picocyanobacteria. Six main differentmorphologies and >30 phylotypes were observed. All sequences retrievedbelonged to the ?Cyanobium+Anathece? clade (Synechococcales) that areknown to have the capability of aggregation/disaggregation. The temporalvariation of picocyanobacteria morphotype composition was weaklycorrelated with the DGGE temporal pattern, and could be explained by thecomposition of the zooplankton assemblage. Laboratory experimentsconfirmed that the small cladoceran Bosmina favoured the dominance ofCPcy, i.e. Cyanodictyon doubled the size of the colonies when present,most likely through the aggregation of single-cell picocyanobacteria intocolonies. Flow cytometry cell sorting and 16S+ITS sequencing of the Pcyand CPcy cytometric populations revealed that some phylotypes could befound in both sorted populations, suggesting phenotypic plasticity in which various Synechococcales phylotypes could be found in situ either as single-cells or as colonies.