CONICET | Buscador de Institutos y Recursos Humanos

Oxygenic photoautotrophs of the genera Synechococcus and Prochlorococcus dominate the marine picoplankton over vast tracts of the worlds oceans and contribute significantly to primary production. While Prochlorococcus are largely confined to a 40ºN-40ºS latitudinal band, Synechococcus are distributed ubiquitously throughout oceanic regions, ranging from polar through temperate to tropical waters and are generally more abundant in nutrient-rich surface waters. The wide oceanic distribution of Synechococcusis mirrored by high physiological and genetic diversity. To date little is known about the prokaryotic phytoplankton diversity in the Southwest Atlantic Ocean. The aim of this work was to characterize at the molecular genetic level, Synechococcus strains from the Argentinean Sea and to carry out d carbon metabolism by ammoniumphylogenetic analyses based on both the ITS of the 16SrRNA gene and on the ntcA gene, which encodes a transcriptional activator (NtcA protein) that mediates the control of nitrogen an. Interestingly, it was shown that expression of ntcA is a useful indicator for determining the nitrogen-status of cyanobacteria, and hence that of the marine environment. After microscopic observation, two Synechococcus strains were isolated and kept in an appropriate growing medium. Total DNA from isolated strains or from environmental samples was used for PCR ampliﬁcation of either 16SrRNA of ntcA gene fragments, and environmental libraries were constructed and maintained in Escherichia coli cells. Essentially identical tree topologies were obtained for the phylogenetic analysis of ntcA sequences supporting the phylogenetic relationships obtained with 16srRNA. Also, amplicons from both gene fragments were obtained from DNA of cultivated Synechococcus strains or DNA from environmental samples and analyzed by Denaturing Gradient Gel Electrophoresis (DGGE). After visualization, the gel bans were excised and the purified DNA samples were sequenced. We conclude that Synechococcus populations belonging to Clade I dominate in the Argentinean Sea. Supported by ANPCyT (PICT Nº 38144), CONICET (PIP 6105), UNMdP, and FIBA.