CONICET | Buscador de Institutos y Recursos Humanos

Unicellular cyanobacteria of the genus Synechococcus are known to be widespread and abundant throughout the worlds oceans and, together with those of the Prochlorococcus genus, are very important contributors to marine and global primary production. Several genetic lineages of Synechococcus have been defined through phylogenetic analysis of the 16S rRNA gene [1], while more potential lineages have been proposed more recently, based on ITS and the N-regulatory gene ntcA [2,3]. The wide oceanic distribution of these microorganisms is mirrored by high physiological and genetic diversity of cultured isolates and natural populations. Recently, a detailed analysis of the distribution of these genetic lineages was reported including the local and ocean basin scale using data from cruises in the Pacific, Altantic, Indian, and Arctic Oceans [4,5]. However, to date little is known about the picophytoplankton diversity in the South Atlantic Ocean. As part of a study on the biodiversity and population dynamics of the unexplored picophytoplankton of the Argentinean Sea, the aim of this work was to identify and molelcular characterize the components of the prokaryotic picophytoplankton using microscopic and molelcular methodologies. Water samples were collected at a permanent coastal station (EPEA, 38º28S-57º41W) or in the shelf in the Patagonian region of the Argentinean Sea. Only cyanobacteria of the genus Synechococcus were found, according with their ecophysiological characteristics [6]. We determined the genetic diversity after PCR amplification, cloning and sequencing of the 16S rRNA gene (from genomic DNA or environmental DNA) and analysed the phylogenetic relationships of Synechochoccus either from cultured isolates or from natural populations. In the latest case, 16S rRNA gene clone libraries were constructed from each water sample collected at 5 m depth. The 16S rRNA gene sequences grouped with Synechococcus of the clade 1 of the marine subcluster 5.1 [6]. Supported by grants of ANPCyT (PICT 2005 16/38144), CONICET (PID 6105), PNUD ARG 02/018 and FIBA.